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Phytochemicals of Cranberries and Cranberry Products: Characterization, Potential Health Effects, and Processing Stability

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Emerging evidence is elucidating how non-nutrient phytochemicals underlie the health promotion afforded by fruits and vegetables. This review focuses on Vaccinium macrocarpon, the American cranberry, compiling a comprehensive list of its known phytochemical components, and detailing their prevalence in cranberry fruit and its products. Flavonoids, especially colored anthocyanins, abundant flavonols, and unique proanthocyanidins, have attracted major research attention. Other notable active components include phenolic acids, benzoates, hydroxycinnamic acids, terpenes and organic acids. Health effects of cranberries, cranberry products, and isolated cranberry components in humans and animals, as well as in vitro, are debated. Evidence for protection from several bacterial pathogens, cancer, cardiovascular disease, and inflammation is compelling, while neuroprotection and anti-viral activity also have begun to draw new consideration. Emerging bioavailability data is considered and potential molecular mechanisms are evaluated, linking phytochemicals to health effects through their biochemical properties and reactions. Finally, the effects of processing and storage on cranberry phytochemicals is discussed, with a focus on identifying research gaps and novel means to preserve their natural, health-promoting components.
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Phytochemicals of Cranberries and Cranberry Products: Characterization,
Potential Health Effects, and Processing Stability
E. Pappas a; K. M. Schaich a
a Department of Food Science, Rutgers University, New Brunswick, NJ
To cite this Article Pappas, E. and Schaich, K. M.(2009) 'Phytochemicals of Cranberries and Cranberry Products:
Characterization, Potential Health Effects, and Processing Stability', Critical Reviews in Food Science and Nutrition, 49:
9, 741 — 781
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Critical Reviews in Food Science and Nutrition
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ISSN: 1040-8398
DOI: 10.1080/10408390802145377
Phytochemicals of Cranberries
and Cranberry Products:
Characterization, Potential Health
Effects, and Processing Stability
E. PAPPAS and K. M. SCHAICH
Department of Food Science, Rutgers University, 65 Dudley Rd., New Brunswick, NJ 08901-8520
Emerging evidence is elucidating how non-nutrient phytochemicals underlie the health promotion afforded by fruits and
vegetables. This review focuses on Vaccinium macrocarpon, the American cranberry, compiling a comprehensive list of
its known phytochemical components, and detailing their prevalence in cranberry fruit and its products. Flavonoids,
especially colored anthocyanins, abundant flavonols, and unique proanthocyanidins, have attracted major research attention.
Other notable active components include phenolic acids, benzoates, hydroxycinnamic acids, terpenes and organic acids.
Health effects of cranberries, cranberry products, and isolated cranberry components in humans and animals, as well
as in vitro,are debated. Evidence for protection from several bacterial pathogens, cancer, cardiovascular disease, and
inflammation is compelling, while neuroprotection and anti-viral activity also have begun to draw new consideration.
Emerging bioavailability data is considered and potential molecular mechanisms are evaluated, linking phytochemicals
to health effects through their biochemical properties and reactions. Finally, the effects of processing and storage on
cranberry phytochemicals is discussed, with a focus on identifying research gaps and novel means to preserve their natural,
health-promoting components.
Keywords anthocyanins, proanthocyanidins, flavonols, phenols, urinary tract infections, cancer, inflammation, absorption
INTRODUCTION
Everyone grows up hearing the admonitions of mothers to
“eat your fruits and vegetables,” and ample scientific evidence
now exists that our mothers were justified. Indeed, the health
benefits from fruits and vegetables are among the best demon-
strated in nutrition. Increased dietary consumption of fruits and
vegetables correlates with increased cardiovascular health as
well as reduced cancer, stroke, degenerative diseases, loss of
functionality associated with aging, and more (Ames and Gold,
1991; Block et al., 1992; Ames et al., 1993; Joshipura et al.,
1999; Temple, 2000; Feldman, 2001; Liu, 2003; Dai et al.,
2006). While fruits and vegetables are rich sources of vitamins
and minerals, recent attention has focused heavily on the effects
of phytochemical components such as flavonoids, stilbenes,
Address correspondence to K. M. Schaich, Department of Food Science,
Rutgers University, 65 Dudley Rd., New Brunswick, NJ 08901-8520, Tel. 732
932-9611 x233. E-mail: schaich@aesop.rutgers.edu
nonnutritive carotenoids, phytoestrogens, terpenes and other di-
verse phenolics (Schaich and Fisher, 1993; Liu, 2004; Rice-
Evans, 2004; Ahuja et al., 2006; Baur and Sinclair, 2006; Cirico
and Omaye, 2006; He and Liu, 2006). The exact mechanisms of
phytochemical action remain largely unexplained and are cur-
rently the subject of much speculation and research. Antioxidant
mechanisms have been proposed, especially in the context of
cardiovascular health, cancer and age-related degenerative dis-
eases (Hollman, 2001; Liu, 2003; Liu, 2004; Shukitt-Hale et al.,
2006a; Patel et al., 2007; Srinivasan et al., 2007). For inflamma-
tion and cancer in particular, phytochemical interactions with
vital proteins, signal transduction pathways, and pathogen bind-
ing also have attracted significant attention (Puupponen-Pimi¨
a
et al., 2001; Steinberg et al., 2004; Comalada et al., 2005; Baur
and Sinclair, 2006; Liu et al., 2006; Neto, 2007a; Ruel and
Couillard, 2007).
Looking at one fruit in particular, the American cranberry,
species Vaccinium macrocarpon, has for centuries been con-
sidered a health food. Native Americans relied on cranberries
as a food, a meat preservative, and a medicine to treat diverse
741
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742 E. PAPPAS AND K. M. SCHAICH
ailments, and they introduced them to European settlers who
enjoyed the bright red berries at the first Thanksgiving dinner
(Henig and Leahy, 2000). No longer merely a side dish to be
eaten with turkey at Thanksgiving, cranberries today are an in-
creasingly significant crop in the United States. With an almost
50% increase in per capita consumption between 1989 and 2004
(USDA-ERS, 2007), the U.S. cranberry crop topped 660 million
pounds worth $1.5 billion in 2006. This increased demand for
and the corresponding production of the fruit have been stim-
ulated by widespread new emphasis on consuming foods that
promote health and well-being and by the perceived unique
health benefits associated with cranberries.
Cranberry juice was a staple folk medicine prescription for
healing urinary tract infections in women, and recent verification
of this pharmaceutical effectiveness against bacterial pathogens
in contemporary clinical studies (see Section titled Urinary Tract
Infections) has excited an explosion of research into cranberry
chemical composition, health effects, absorption, bioavailabil-
ity, metabolism, and antioxidant capacity. However, despite tar-
geted grant programs, dozens of studies, and several theories,
no mechanism to explain the effects of cranberries on urinary
tract infections has yet been conclusively identified. Indeed, as
new data becomes available, often more questions than answers
arise.
To provide a basis for understanding the complexities of
cranberry nutraceutical actions, this paper compiles current in-
formation about the phytochemical composition of American
cranberries and reviews cranberry health effects in the context
of the absorption, bioavailability, metabolism, and excretion
of cranberry phytochemicals. Molecular mechanisms proposed
to account for the potential dietary benefits of cranberries are
discussed. Lastly, because cranberries are rarely consumed in
their natural state, processing critically influences components
available to affect the health of consumers; thus, alterations in
composition and destruction of nutrients and phytochemicals by
processing and storage also are reviewed. Consideration is lim-
ited to the American cranberry; its wild relative (the European
cranberry), Vaccinium Oxycoccus, will not be included.
PHYTOCHEMICALS OF CRANBERRIES AND
CRANBERRY PRODUCTS
Cranberries are a uniquely rich and heterogeneous source
of phytochemicals. Currently, over 150 individual phytochem-
icals have been identified and studied in cranberries, although
undoubtedly many more will be discovered with continued im-
provement in analytical methods.
Table 1 summarizes general classes of phytochemicals re-
ported to exhibit bioactivity in cranberries, along with their
characteristic properties, functionalities, and reported health
effects. By far, the dominant components are flavonoids. Most
readily-recognized are anthocyanins responsible for the bright
red cranberry color; flavonols, secondary yellowish pigments;
proanthocyanidins associated with protection against urinary
tract infections; catechins, organic acids, and resveratrol which
contribute the sour, astringent flavor unique to cranberries; ter-
pene aroma components; and pectins that gel cooked cranberries
into the cranberry sauce familiar to everyone.
Table 2 provides a comprehensive list of individual cran-
berry phytochemicals in each class, along with their concen-
trations in cranberries and cranberry products. Most research
has focused on cranberry flavonoids, including anthocyanins
(ACYs), proanthocyanidins (PACs), flavonols, and flavan-3-ols.
Other polyphenolics, simple phenolics, terpenes, organic acids,
complex carbohydrates, and sugars of cranberries have attracted
somewhat less medical research attention, but nevertheless have
shown some promise as health promoters.
Additional details about cranberry components and their
health effects are provided in the following discussion.
Anthocyanins
Anthocyanins (ACYs), probably the most studied chemical
component of cranberries, are responsible for the majority of
the red color that is appealing and distinctive enough to demand
its own shade: “cranberry red”. Localized within color bodies
in the exocarp layer of the fruit’s skin, anthocyanins are po-
tent color attractants in cranberries and accumulate as the fruit
matures (Sapers et al., 1983a; Vvedenskaya and Vorsa, 2004).
Given the strong antioxidant activity of anthocyanins, recent re-
search focus has shifted from spectral characteristics to bioac-
tivity and potential health benefits. Structures of individual an-
thocyanins are shown in Table 3; corresponding concentrations
in whole berries and in cranberry juice concentrate are listed in
Table 2.
The major pigments of cranberries, 3-monogalactosides and
3-monoarabinosides of cyanidin and peonidin (Structures 1–2
and 4–5, respectively, Table 3), were identified first (Sakamura
and Francis, 1961; Zapsalis and Francis, 1965) and the 3-
monoglucosides of cyanidin (structure 3, Table 3) and peoni-
din (structure 6, Table 3) were identified a short time later
(Fuleki and Francis, 1967). For several decades, these six an-
thocyanins remained the only ones found in cranberries and are
still believed to contribute most of the desirable color in fresh
cranberries.
Recent analyses have revealed a much more diverse ACY
profile in processed cranberry products. Using HPLC-ESI-MS-
MS, Wu and Prior (2005) identified 13 anthocyanins in freeze
dried cranberries, adding malvidin, pelargonidin, delphinidin,
and petunidin to the basic backbone structures (along with
cyanidin and peonidin). Furthermore, their results showed that
of the eighteen anthocyanin-rich fruits tested, only cranberries
and Concord grapes contained all six anthocyanin backbones.
Of the thirteen anthocyanins identified, all except peonidin
3,5-diglucoside are present also in processed cranberry juice
(Ohnishi et al., 2006). However, the possibility that these newly
identified anthocyanins are artifacts of tandem mass spectral
analysis cannot yet be ruled out and confirmatory identification
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CRANBERRY PHYTOCHEMICALS 743
Tab le 1 Summary of phytochemical classes with potential health benefits from cranberry fruit
Phytochemical
Class Example
Function in
Plant
Function in
Cranberry
Products
Potential
Health
Benefits
Bio-
availability References
Flavonoids:
Anthocyanins peonidin-3-O-
galactoside
color attractants primary red pigment AC, AOX, NFP,
CHB
+Karakaya, 2004;
Andres-Lacueva et al.,
2005; Crews et al., 2005
Yao and Viero, 2006;
Ohnishi et al., 2006
Flavonols quercetin-3-
Ogalactoside
color attractants,
reproduction,
UV protection
copigment, AOX
stabilizer
AC, AI , AOX,
CHB
++ Moon et al., 2001; Yan et al.,
2002; Zhang and Wang
2003; Li et al., 2004;
Vvendenskaya and Vorsa,
2004; Karakaya, 2004;
Chen and Zuo, 2007
Flavanols (Catechins) epicatechin pathogen defense astringent flavors,
AOX stabilizer
AC, AI , AOX,
CHB
++ Manach et al., 1999; Chen
et al., 2001; Cunningham
et al., 2004; Karakaya,
2004; Harnley et al., 2006
Proanthocyanidins proanthocyanin A2 pathogen defense,
structural
astringent flavors,
AOX stabilizer
AA, AOX, AU,
AV, CHB, NFP
Howell et al., 1998; Foo et al.,
2000a; Foo et al., 2000b;
Ariga, 2004; Prior and Gu,
2005; Neto et al., 2006
Polymeric Color
Compounds
cyanidin-pentoside-
flavan-3-ol
color attractants red-brown pigment AOX?, AA?, AV? ? Hong and Wrolstad, 1986a;
Reed et al., 2005
Non-Flavonoids:
Non-Flavonoid
Polyphenols
resveratrol diverse astringent flavors,
AOX stabilizer
AC, AI , AOX +Daniel et al.,1989; Mazur
et al., 2000; Asensi et al.,
2002; Wang et al., 2002;
Baur and Sinclair, 2006
Simple Phenolics salicylic acid AOX, odor attractants odors,
AOX stabilizer
AC, AI , AOX,
CHB
++ Borne and Rice-Evans, 1998;
Zuo et al., 2002; Zhang and
Zuo, 2004; Karakaya,
2004; Duthie et al., 2005
Non-Phenols:
Non-Aromatic
Organic Acids
ascorbic acid antibacterial sour flavors AC, AOX +++ Hong and Wrolstad, 1986a;
Jensen et al., 2002;
Cunningham et al., 2004;
He and Liu, 2006
Complex
Carbohydrates
pectin structural gelation, edible films AC, AOX Struckrath et al., 1998;
Cunningham et al., 2004;
Kahlon and Smith, 2006
Sugars fructose energy storage sweet flavors AA, AC +++ Hong and Wrolstad 1986a;
Neto et al., 2005; He and
Liu, 2006
Abbreviations Used: AA =Antiadhesion towards bacteria, AC =Anticancer, AI =Anti-inflammatory, AOX =Antioxidant, AU =Antiulcer, AV =Antiadhesion
towards viral pathogens, CHB =Cardiovasular health benefits, NFP =Neural Function Protection. Symbols used: ? denotes unknown.
by NMR, IR, or other non-destructive analytical or chemical
techniques is needed. Furthermore, these have not been identi-
fied in fresh fruit and could be a result of processing or sample
preparation. The malvidin, pelargonidin, delphinidin and petu-
nidin compounds account for only about 1% of the total ACYs
of cranberries (Wu et al., 2006) and thus do not contribute signif-
icantly to cranberry color. If these novel cranberry anthocyanins
do result from processing, questions arise as to whether they
add to or detract from the nutraceutical properties of fresh cran-
berries. Natural or not, it will be interesting to learn whether
they have some specific and unique health benefits (Wu et al.,
2006).
Although cranberries are rich in dietary anthocyanins in gen-
eral, they may be even more important as major sources of
individual ACY species in the US diet. Peonidin glycosides, in
particular, make up only 7% of the total ACY intake in the
US (Wu et al., 2006) but comprise half of the total cranberry
anthocyanins (Prior et al., 2001). Also notable are the cyani-
din and peonidin galactosides and arabinosides, which account
for 57.8% and 39.5%, respectively, of cranberry anthocyanins
(Prior et al., 2001) but are rarely found in other commonly con-
sumed fruits (Wu and Prior, 2005). New evidence suggests that
these glycosides appear to selectively facilitate absorption of
anthocyanins (Mulleder et al., 2002; Vorsa et al., 2007a), so
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744 E. PAPPAS AND K. M. SCHAICH
Tab le 2 Phytochemical components of the American cranberry, Vaccinium macrocarpon
Conc. in
Cran.
Phytochemical/Class # Conc. in Cran. ProductsReferences
Anthocyanins 13.6–171 mg/100 g 13.6 mg/L Sapers et al., 1983; Ozgen et al., 2005 Lee et al.,
2005;
cyanidin-3-O-galactoside 1 2.0 mg/L Cunningham et al., 2004
cyanidin-3-O-arabinoside 2 1.4 mg/L Cunningham et al., 2004
cyanidin-3-O-glucoside 3 0.1 mg/L Cunningham et al., 2004
peonidin-3-O-galactoside 4 2.8 mg/L Cunningham et al., 2004
peonidin-3-O-arabinoside 5 1.1 mg/L Cunningham et al., 2004
peonidin-3-O-glucoside 6 0.3 mg/L Cunningham et al., 2004
peonidin 3,5-digalactoside Wu and Prior, 2005
malvidin-3-O-arabinoside 7 Wu and Prior, 2005; Ohnishi et al., 2006
malvidin-3-O-galactoside 8 Wu and Prior, 2005; Ohnishi et al., 2006
pelargonidin-3-O-arabinoside 9 Wu and Prior, 2005; Ohnishi et al., 2006
pelargonidin-3-O-galactoside 10 Wu and Prior, 2005; Ohnishi et al., 2006
delphinidin-3-O-arabinoside 11 Wu and Prior, 2005; Ohnishi et al., 2006
petunidin-3-O-galactoside 12 Wu and Prior, 2005; Ohnishi et al., 2006
Polymeric Color Compounds Hong and Wrolstad, 1986a; Reed et al., 2005
Flavonols 200–400 mg/kg 48.5 mg/L Zheng and Wang, 2003; Cunningham et al., 2004;
Vvedenskaya and Vorsa, 2004
quercetin 13 104 mg/kg∗∗;
194 mg/kg∗∗;
41.6 µg/g
13.0 mg/L;
30.6 µmol/L
Zheng and Wang, 2003;Cunningham et al., 2004;
Harnley et al., 2006; Mullen et al., 2007
quercetin-3-galactoside (hyperin) 14 70.4 µg/g 23.2 mg/L Zheng and Wang, 2003; Cunningham et al., 2004
quercetin-3-α-arabinopyranoside
(avicularin)
15 34.4 µg/g 1.8 mg/L;
5.4 µmol/L
Zheng and Wang, 2003; Cunningham et al., 2004;
Vvedenskaya et al., 2004; Mulllen et al., 2007
quercetin-3-rhamnoside (quercitrin) 16 41.6 µg/g 5.2 mg/L;
10.8 µmol/L
Zheng and Wang, 2003; Cunningham et al., 2004;
Vvedenskaya et al., 2004; Mullen et al., 2007
quercetin-3-xyloside 6.0 µmol/L Yan et al., 2002; Mullen et al., 2007
quercetin-3-β-glucoside (isoquercetin) Vvedenskaya et al., 2004; Vvedenskaya and
Vorsa, 2004
3-methoxyquercetin-3-β-galactoside Vvedenskaya et al., 2004; Vvedenskaya and
Vorsa, 2004
3-methoxyquercetin-3-α-xylopyranoside Vvedenskaya et al., 2004; Vvedenskaya and
Vorsa, 2004
quercetin-3-O-(6-p-coumaroyl)-β-
galactoside
17 Vvedenskaya et al., 2004; Vvedenskaya and
Vorsa, 2004
quercetin-3-O-(6-benzoyl)-β-galactoside 18 Vvedenskaya et al., 2004; Vvedenskaya and
Vorsa, 2004
kaempferol Bilyk and Sapers, 1986
kaempferol-3-glucoside 5.6 µg/g Zheng and Wang, 2003
myricetin 19 69 mg/kg∗∗ ;
166 mg/kg∗∗
5.3 mg/L;
16.1 µmol/L
Cunningham et al., 2004; Harnley et al., 2006;
Mullen et al., 2007
myricetin-3-β-xylopyranoside 20 3.3 µmol/L Vvedenskaya et al., 2004; Vvedenskaya and
Vorsa, 2004, Mullen et al., 2007
myricetin 3-α-arabinofuranoside 21 37.5 µg/g Yan et al., 2002; Zheng and Wang, 2003
Catechins 7.3 mg/100 g 6 mg/L Gu et al., 2004
()epicatechin 22 4.5 mg/100 g∗∗ 8.1 mg/L (WJ);
3.5 mg/L
Gu et al., 2004a; Cunningham et al., 2004;
Harnley et al., 2006
epigallocatechin 1.5 mg/100 g∗∗ Harnley et al., 2006
(+)catechin 23 0.8 mg/100 g∗∗ 8.1 mg/L (WJ) Chen et al., 2001; Harnley et al., 2006
epigallocatechin gallate 1.9 mg/100 g∗∗ Harnley et al., 2006
catechin gallate 7.9 mg/100 g∗∗ Harnley et al., 2006
gallocatechin gallate 0.4 mg/100 g∗∗ Harnley et al., 2006
Proanthocyanins 418.8 mg/100 g 231–625 mg/L;
35 mg/100 g (CS);
80 mg/100 g (SDC)
Porter et al., 2001; Gu et al., 2004; Cunningamn
et al., 2004, Neto et al., 2006
Total Dimers 25.9 mg/100 g 29 mg/L Gu et al., 2004
procyanidin B2 {(EC-(4β8)-EC}24 Foo et al., 2000a; Prior et al., 2001
procyanidin A2 {EC-(4β8,
2βO7)-EC}
25 Foo et al., 2000a; Prior et al., 2001
Total Trimers 18.8 mg/100 g 17 mg/L Gu et al., 2004
EC-(4β6)-EC-(4β8, 2βO7)-EC 26 Foo et al., 2000a; Prior et al., 2001
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CRANBERRY PHYTOCHEMICALS 745
Tab le 2 Phytochemical components of the American cranberry, Vaccinium macrocarpon (Continued)
Conc. in
Cran.
Phytochemical/Class # Conc. in Cran. ProductsReferences
EC-(4β8, 2βO7)EC-(4β8)-EC 27 Foo et al., 2000a; Prior et al., 2001
EC-(4β8)-EC-(4β8, 2βO7)-EC 28 Foo et al., 2000a; Prior et al., 2001
Total 4–6 mers 70.3 mg/100 g 49 mg/L Gu et al., 2004
Total 7–10 mers 62.9 mg/100 g 41 mg/L Gu et al., 2004
Total >10 mers 233.5 mg/100 g 89 mg/L Gu et al., 2004
flavanones — —
naringenin 7-glucosode (Prunin) Turner et al., 2005
Non-flavonoid Polyphenols
phloretin 2-glucoside (phloridzin) Lotito and Frei, 2004; Turner et al., 2005
ellagic acid 120 mg/kg (DWB) Daniel et al., 1989
2-O-(3,4-dihydroxybenzoyl)-2,4,6-
trihydroxyphenylmethylacetate
29 Turner et al., 2007
trans-resveratrol 30 — 0.2 mg/L (WJ)∗∗ Wang et al., 2002; Baur and Sinclair, 2006
cis-resveratrol 0.03 mg/L (WJ)∗∗ Wang et al., 2002; Baur and Sinclair, 2006
secoisolariciresinol (SECO) 31 10.54 mg/kg (DWB)∗∗ Mazur et al., 2000; Cunningham et al., 2004
Phenolic Acids and Benzoates
Total phenolic Acids 5.7 g/kg Zuo et al., 2002
benzoic acid 32 4741 µg/g∗∗ 54.94 ug/mL∗∗; 43.7
mg/L
Zuo et al., 2002; Cunningham et al., 2004;
Zhang and Zuo, 2004
o-hydroxybenzoic acid (salicylic acid) 33 23.2 µg/g∗∗ 3.11 µg/mL∗∗;7.04
mg/L∗∗
Zuo et al., 2002; Zhang and Zuo, 2004; Duthie
et al., 2005
m-hydroxybenzoic acid 9.14 µg/g∗∗ 0.15 µg/mL∗∗ Zuo et al., 2002; Zhang and Zuo, 2004
p-hydroxybenzoic acid 21.6 µg/g∗∗ 0.07 µg/mL∗∗ Zuo et al., 2002; Zhang and Zuo, 2004
phydroxyphenylacetic acid 7.36 µg/g∗∗ ND Zuo et al., 2002; Zhang and Zuo, 2004
2,3-dihydroxybenzoic acid 3.16 µg/g∗∗ 2.41 µg/mL∗∗ Zuo et al., 2002; Zhang and Zuo, 2004
2,4-dihydroxy benzoic acid 34 42.5 µg/g∗∗ ND Zuo et al., 2002; Zhang and Zuo, 2004
3,4-dihydroxybenzoic acid
(protocatechuic acid)
2.3 mg/L Cunningham et al., 2004
vanillic acid 35 19.2 µg/g∗∗; 49.3 µg/g 1.2 mg/L Zuo et al., 2002; Zheng and Wang 2003;
Cunningham et al., 2004
trans-cinnamic acid 36 20.5 µg/g∗∗ 0.18 µg/mL∗∗ Zuo et al., 2002; Zhang and Zuo, 2004
o-hydroxycinnamic acid 89 µg/g∗∗ 3.43 µg/mL∗∗ Zuo et al., 2002; Zhang and Zuo, 2004
p-coumaric acid 37 253.8 µg/g∗∗ 2.63 µg/mL∗∗ ;4.4
mg/L; 5.2 mg/L
Chen et al., 2001; Zuo et al., 2002; Zhang and
Zuo, 2004
o-phthalic acid 15.7 µg/g∗∗ Zuo et al., 2002
caffeic acid 38 156.4 µg/g∗∗; 42.5 µg/g 1.1 mg/L Zuo et al., 2002; Zheng and Wang 2003;
Cunningham et al., 2004
ferulic acid 39 87.9 µg/g∗∗ 1.11 µg/mL∗∗ Zuo et al., 2002; Zhang and Zuo, 2004
sinapic acid 40 211.8 µg/g∗∗ 5.11 µg/mL∗∗ Zuo et al., 2002; Zhang and Zuo, 2004
gallic acid ∗∗ Zhang and Shetty, 2000
3-O-caffeoylquinic acid (chlorogenic acid) 5.1 mg/L; 11.0 mg/L Chen et al., 2001; Cunningham et al., 2004
5-O-caffeoylquinic acid 25.4 umol/L Mullen et al., 2007
benzoic acid α-L-arabinopyranosyl
(16)-β-D-glucopyranoside
He and Liu, 2006
6-O-benzoyl-β-D-glucose (vacciniin) 0.022% Marwan and Nagel, 1986; Heimhuber et al.,
1990; He and Liu, 2006
1-O-benzoyl-β-D-glucose ? Heimhuber et al., 1990
2-O-benzoyl-β-D-glucose ? Heimhuber et al., 1990
6-O-benzoyl-α-D-glucose ? Heimhuber et al., 1990
Other Phenols —— —
1-[3-(4-hydroxyphenyl)-2-propenoate]-β-D-
glucopyranoside
He and Liu, 2006
benzyl benzoate Croteau and Fagerson, 1971
benzaldehyde Croteau and Fagerson, 1971
4-methoxy benzaldehyde Croteau and Fagerson, 1971
benzyl alcohol Croteau and Fagerson, 1971
2-phenyl ethanol Croteau and Fagerson, 1971
dibutyl phthalate Croteau and Fagerson, 1971
2-hydroxy diphenyl Croteau and Fagerson, 1971
methyl benzoate Croteau and Fagerson, 1971
(Continued on next page)
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746 E. PAPPAS AND K. M. SCHAICH
Tab le 2 Phytochemical components of the American cranberry, Vaccinium macrocarpon (Continued)
Conc. in
Cran.
Phytochemical/Class # Conc. in Cran. ProductsReferences
ethyl benzoate Croteau and Fagerson, 1971
benzyl formate Croteau and Fagerson, 1971
benzyl ethyl ether Croteau and Fagerson, 1971
acetophenone Croteau and Fagerson, 1971
Non-Phenolic Organic Acids 2.67–3.65% (w/v) 2.75%(WJ) Jensen et al., 2002; He and Liu, 2006
quinic acid 41 1.05% (WJ), >0.26% Cunningham et al., 2004; He and Liu, 2006
citric acid 1.06% (WJ) Jensen et al., 2002; Cunningham et al., 2004
malic acid 0.78% (WJ) Cunningham et al., 2004
shkimic acid 42 0.1–0.9 g/100 g (WJ) Hong and Wrolstad, 1986a; Jensen et al., 2002
galacturonic acid 0.19% (WJ) Cunningham et al., 2004
2-furoic acid 2.9 ppm Cunningham et al., 2004
oxalic acid 5 ppm Cunningham et al., 2004
2(R)-hydroxybutanedioic acid 1-methyl ester
(tartaric acid methyl ester)
43 He and Liu, 2006
2(R)-hydroxybutanedioic acid (tartaric acid) He and Liu, 2006
fumaric acid Seeram et al., 2004
isocitric acid Seeram et al., 2004
2-methyl butyric acid Duke, 1992
ascorbic acid 11.5 mg/100 g 0–2 mg/100 g (WJ) Licciardello et al., 1952; Hong and Wrolstad,
1986a; Cunningam et al., 2004
Terpenes Jensen et al., 2002; Choi et al., 2005
oleanolic acid Wu and Parks, 1953
ursolic acid 44 60–110 mg/100 g Wu and Parks, 1956; Kondo, 2006; He and
Liu, 2006
cis-3-O-p-hydroxy cinnamoyl ursolic acid 45 Murphy et al., 2003; He and Liu, 2006
trans-3-O-p-hydroxy cinnamoyl ursolic acid 46 Murphy et al., 2003; He and Liu, 2006
β-sitosterol He and Liu, 2006
β-sitosterol-3-Oβ-D-glucoside He and Liu, 2006
monotropein 47 Jensen et al., 2002; Choi et al., 2005
6,7-dihydromonotropein 48 Jensen et al., 2002
10-p-cis-coumaroyl-1S-dihydromonotropein 49 Turner et al., 2007
10-p-trans-coumaroyl-1S-dihydromonotropein Turner et al., 2007
Complex Carbohydrates/Fiber 12000–160000 ppm 0.1% (WJ); 1.4% (CS) Marlett and Vollendorf, 1994; Cunningham
et al., 2004; Kahlon and Smith, 2007
cellulose Holmes and Rha, 1978
hemicellulose Holmes and Rha, 1978
protopectin Stuckrath et al., 1998
high methoxy pectin Stuckrath et al., 1998
Sugars 3.7–5.4% (WJ) Hong and Wrolstad, 1986a; Lowe and
Fagelman, 2001; Cunningham et al., 2004,
Turner et al., 2005
glucose 4.3% Hong and Wrolstad, 1986a; Cunningham
et al., 2004
sucrose <0.05% Cunningham et al., 2004
fructose 0.8% (WJ) Hong and Wrolstad, 1986a; Lowe and
Fagelman, 2001; Cunningham et al., 2004
Sorbitol trace Cunningham et al., 2004
1-O-methylgalactose 5 ppm (WJ) Turner et al., 2005
Miscellaneous
lutein 0.28–2 ppm Duke, 1992
niacin 1–8.3 ppm Duke, 1992
pantothenic acid 2.2–16 ppm Duke, 1992
thiamin (vitamin B1) 0.3–2.5 ppm Duke, 1992
riboflavin (vitamin B2) 0.2–1.7 ppm Duke, 1992
adermine (vitamin B6) 0.6–5.4 ppm Duke, 1992
folic acid (vitamin B9) 0.1–0.2 ppm Duke, 1992
beta-carotene 0.2–2.6 ppm Duke, 1992
alpha tocopherol 9–81 ppm Duke, 1992
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CRANBERRY PHYTOCHEMICALS 747
Tab le 3 Chemical structures of anthocyanins found in cranberries
Structure # Anthocyanin Name R1R2R3
1 cyanidin-3-O-galactoside OH H Galactose
2 cyanidin-3-O-arib inoside OH H Arabinose
3 cyanidin-3-O-glucoside OH H Glucose
4 peonidin-3-O-galactoside OMe H Galactose
5 peonidin-3-O-arib inoside OMe H Arabinose
6 peonidin-3-O-glucoside OMe H Glucose
7 malvidin-3-O-arib inoside OMe OMe Arabinose
8 malvidin-3-O-galactoside OMe OMe Galactose
9 pelargonidin-3-O-arib inoside H H Arabinose
10 pelargonidin-3-O-galactoside H H Galactose
11 delphinidin-3-O-arib inoside OH OH Arabinose
12 petunidin-3-O-galactoside OMe OH Galactose
may increase the availability of cranberry anthocyanins relative
to other sources.
Whole raw cranberries contain high but inconsistent levels
of anthocyanins, varying from 13.6 to 140 mg/100 g depending
on fruit size, ripeness, variety, and other factors (Sapers et al.,
1983a, 1983b; Vorsa and Welker, 1985; ¨
Ozgen et al., 2005).
These high levels make cranberries a potentially significant di-
etary source of anthocyanins, especially considering that cur-
rent U.S. per capita consumption of anthocyanins is estimated
at only 12.5 mg total ACY/day (Wu et al., 2006). Interestingly,
it is common industry practice for cranberry processors to pay
growers a “color bonus” based on ACY content of their berries
(Francis, 1995; Vvedenskaya and Vorsa, 2004; ¨
Ozgen et al.,
2005), and much effort has been devoted to improving the an-
thocyanin yield (and hence color intensity) of cranberries, both
through plant breeding techniques and use of topical treatments
(Vorsa et al., 2003; ¨
Ozgen et al., 2005). Indeed, very recently, a
new cultivar of cranberry has been bred and patented, claiming
higher anthocyanin yields as one of its primary improvements
over traditionally cultivated strains (Vorsa, 2007).
Cranberry juice cocktails contain lower amounts of antho-
cyanins, ranging from approximately 1.2–1.5 mg/100 mL (Prior
et al., 2001; Lee et al., 2005) to as high as 2.5 mg/100 mL
(Cunningham et al., 2004).
Polymeric Pigments
While monomeric anthocyanins are the major bright red pig-
ments, polymeric anthocyanin-containing compounds are the
source of deeper brownish-red colors in cranberries. About 10%
of the color in freshly prepared whole cranberry juice is due to
polymeric material (Hong and Wrolstad, 1986a), and this in-
creases with age of the juice. In fact, cranberry researchers
measure polymeric color (determined as the color remaining af-
ter anthocyanins are bleached) to determine the extent of color
deterioration during post-harvest degradation, processing, and
storage.
Pigmented polymers from cranberries have been only par-
tially characterized and remain poorly understood. Nevertheless,
several lines of evidence support their existence. Some cran-
berry proanthocyanidin fractions show a weak absorbance at 520
nm, the wavelength associated with anthocyanins (Porter et al.,
2001). Matrix assisted laser desorption ionization mass spec-
trometry (MALDI-MS) analysis of cranberry juice extract de-
tected the presence of novel anthocyanin-epicatechin oligomers
(Neto, 2007b), as well as several vinyl linked ACY-flavanol
dimers (Krueger et al., 2004; Reed et al., 2005):
cyanidin-pentoside-flavan-3-ol (m/z 735.3)
peonidin-pentoside-flavan-3-ol (m/z 749.3)
cyanidin-hexoside-flavan-3-ol (m/z 765.4)
peonidin-hexoside-flavan-3-ol (m/z 779.3)
Several anthocyanins linked to A and B type PAC dimers
were also identified (Krueger et al., 2004; Reed et al., 2005):
cyanidin-pentoside-DP2 (A-type =m/z 1021.2, B-type =m/z
1023.1)
peonidin-pentoside-DP2 (A-type =m/z 1035.1, B-type =m/z
1037.1)
cyanidin-hexoside-DP2 (A-type =m/z 1051.2, B-type =m/z
1053.2)
peonidin-hexoside-DP2 (A-type =m/z 1065.2, B-type =m/z
1067.1).
Twenty-eight similar ACY-PAC conjugates in spray dried
juice and twenty-five in whole cranberry berry extracts were
reported, all with a single anthocyanin residue and degrees of
polymerization up to six (Krueger et al., 2004). Increased het-
erogeneity of higher polymers prevented their characterization
(Krueger et al., 2004). One plausible chemical structure for
these polymers is presented in Fig. 1. The authors propose that
these compounds are generated during normal fruit ripening,
although the possibility that the polymers were analytical arti-
facts or chemical degradation products could not be ruled out.
MALDI-MS characterizations are tentative, and NMR or IR
confirmation will be necessary for positive identification of an-
thocyanin and flavanol monomer units, sugar moieties, linkages
involved, and overall structures.
Substantial research on polymeric color has been conducted
in wine, where anthocyanins can be linked to flavan-3-ol
monomers and polymers via a vinyl linkage (from acetaldehyde
condensation) or via an ether linkage (through direct conden-
sation) (Es-Safi and Cheynier, 2004; Sun and Hai Liu, 2006).
In grapes, both types of polymers contain multiple units of
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748 E. PAPPAS AND K. M. SCHAICH
Figure 1 Postulated vinyl linkages between anthocyanin (cyanidin-3-
galactoside) and proanthocyanidin (PAC A2) in a polymeric pigment from
cranberries, determined by MALDI-TOF mass spectral analysis (Krueger et al.,
2004; Reed et al., 2005).
epicatechin and one unit of malvidin-3-glucoside. Wine also
contains a class of anthocyanin-derived pigments known as
pyranthocyanins (Sun and Hai Liu, 2006). However, only vinyl-
linked anthocyanin-flavanol complexes have been found in
cranberries.
Given their strong antioxidant activity and structural simi-
larities to PACs, polymeric color compounds warrant research
as health-promoting compounds. With high molecular weight,
these polymeric color compounds (and perhaps ether-linked
ACY-PAC complexes) are likely to be present in significant
quantity in cranberry NDM (non-dialyzable material) (see Sec-
tion titled High Molecular Weight Fraction (NMD)) and may be
responsible for some health effects observed from that cranberry
fraction. However, support for any health benefits necessitates
further research into the fate of these molecules upon con-
sumption, which is totally absent in today’s literature. Health-
promoting activity in the mouth, stomach, and the digestive
tract should be expected, but the high molecular weight pre-
cludes significant absorption: systemic effects are feasible only
if these compounds are degraded to smaller compounds in the
GI tract.
Flavonols
Flavonols in whole cranberries are mostly glycosylated forms
of quercetin, myricetin, and, to a lesser extent, kaempferol.
Puski and Francis (1967) first identified individual flavonols
and flavanol glycosides in cranberries and found quercetin
(structure 13, Fig. 2), quercetin-3-galactoside (hyperin or hy-
peroside) (structure 14, Fig. 2), quercetin-3-arabinoside (avicu-
larin) (structure 15, Fig. 2), quercetin-3-rhamnoside (quercitrin)
(structure 16, Fig. 2), myricetin-3-arabinoside (structure 21,
Figure 2 Chemical structures of selected cranberry flavonols (quercetin
and derivatives 1318; myricetin and derivatives 19–21): quercetin (13); hy-
perin (14); avicularin (15); quercitrin (16); quercetin-3-O-(6-p-coumaroyl)-
β-galactoside (17); quercetin-3-O-(6-benzoyl)-β-galactoside (18); myricetin
(19); myricetin β-xylopyranoside (20) and myricetin 3-α-arabinoside (21).
Fig. 2) and myricetin-3-digalactoside in the Early Black va-
riety of cranberries. Later, small amounts of kaempfero1 (0 to
2.5 mg/kg) were reported in some, but not all, cranberry vari-
eties (Bilyk and Sapers, 1986).
Contemporary analytical technology has revealed a far more
diverse profile of cranberry flavonols. Myricetin 3-α-arabino-
furanoside, quercetin 3-xyloside, and 3-methoxyquercetin 3-β
-galactoside (isorhamnetin-3-galactoside) have been identi-
fied by 1H and 13C NMR (Yan et al., 2002). Zheng and
Wang (2003) reported the presence of kaempferol-3-glucoside
and another unidentified kaempferol derivative in Ben
Lear cranberries. HPLC isolated and MS, 1H and
13C NMR identified quercetin-3-β-glucoside (isoquercetin),
3-methoxyquercetin-3-α-xylopyranoside, quercetin-3-O-(6-
p-coumaroyl)-β-galactoside (structure 17, Fig. 2), quercetin-
3-O-(6-benzoyl)-β-galactoside (structure 18, Fig. 2) and
myricetin-3-β-xylopyranoside (structure 20, Fig. 2) in cranberry
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CRANBERRY PHYTOCHEMICALS 749
powder (Vvedenskaya et al., 2004). Two of these compounds
(structures 17 and 18, Fig. 2) exhibit a rare structural
characteristic—a phenolic acid substituted on a sugar unit of a
flavonol-glycoside—and present a new class of phytochemical
never before observed in cranberries. In all, this study detected
twenty-two distinct compounds believed to be flavonols, fifteen
of which were identified. Vvedenskaya and Vorsa (2004) con-
firmed the presence of all of these flavonols in whole cranberry
fruit as well, showing the remarkable diversity and abundance
of flavonols in cranberries and cranberry products.
Flavonols are relatively unimportant to cranberry color,
primarily contributing yellow undertones. However, these
flavonoids are now thought to underlie many cranberry health
benefits (Neto, 2007b; Vorsa et al., 2007a). Cranberry flavonols
are rather unique in character, containing distributions not found
in other fruits, and this in itself makes them very interesting to
study. However, it is the unparalleled high concentrations of
cranberry flavonols that seem most significant to health effects,
which will be discussed further in Sections on the Health Effect
of Cranberries, Bioavailability and Metabolism, and Molecular
Mechanisms Underlying Health Effects.
Total flavonol contents of cranberries are consistently high
across cultivars and high compared to related species such as
blueberry and blackberry (Bilyk and Sapers, 1986), ranging
from 200 to 400 mg/kg in fresh cranberries (Zheng and
Wang, 2003; Vvedenskaya and Vorsa, 2004/11; Harnly et al.,
2006). Indeed, a recent review lists cranberries as the most
abundant source of flavonols among thirty plant foods known to
contain these bioactive phytochemicals (Aherne and O’Brien,
2002). Yellow onion (350–1200 mg/kg) and curly kale (300–
600 mg/kg) have similar or higher levels of total flavonols than
cranberries, but no fruits exceeded cranberry flavonol contents
by weight (Manach et al., 2004). One recent investigation re-
vealed that flavonol concentrations are remarkably constant over
the development of both Ben Lear and Stevens cranberry, rang-
ing from 35 to 45 mg/100 unripe to mature. In contrast, an-
thocyanins increase dramatically from 0to>100 mg/100 g
as the fruit ripens, while proanthocyanidins levels start high
(180–220 mg/100 g) at berry onset, decrease by about half to
60–110 mg/100 g during early stages of development, and then
increase again slightly to 80–130 mg/100 g as the berry ripens
(Vvedenskaya and Vorsa, 2004).
Cranberry juice cocktail contains 4.85 mg/100 mL total
flavonols (Cunningham et al., 2004), higher than any other bev-
erage reviewed by Aherne et al. (2002) and nearly twice the
flavonol content of 12 other commonly consumed, commer-
cially available juices: purple grape, red grape, pomegranate,
clear apple, cloudy apple, grapefruit, reconstituted concentrated
orange, fresh orange, tropical fruit blend, white grape, pineap-
ple, tomato (Mullen et al., 2007). Interestingly, flavonol con-
centrations are lower than anthocyanins in ripe cranberry fruit
(Vvedenskaya and Vorsa, 2004), but are about three times higher
than anthocyanins in cranberry juice (Cunningham et al., 2004;
Mullen et al., 2007). Lower anthocyanin levels in juice could
be due to several factors, including incomplete anthocyanin ex-
Figure 3 Molecular structures of selected cranberry catechin monomers: the
stereoisomers () epicatechin (22)and(+) catechin (23).
traction during pressing and greater susceptibility to oxidative
degradation, as will be discussed further in the Section titled
Effects of Processing, Storage and Composition on Cranberry
Phytochemical Stability.
Data on individual flavonol contents of cranberries is some-
what more limited (Table 2). Zheng and Wang (2003) report
hyperin (7.04 mg/100 g), quercetin (4.16 mg/100 g), myricetin
3-arabinoside (3.75 mg/100 g) and avicularin (3.45 mg/100 g)
in Ben Lear cranberries. Harnley et al. (2006) found 16.6 mg
myricetin and 19.4 mg quercetin per 100 g hydrolyzed raw cran-
berries. These are substantial concentrations considering esti-
mates of 20–22 mg/day combined total flavonol and flavonone
dietary intake in American doctors (Sampson et al., 2002).
Flavonol concentrations in cranberry juice cocktail are some-
what lower due to dilution and perhaps oxidation: 2.32, 1.30,
0.53, 0.52, and 0.18 mg/100 mL respectively for hyperin,
quercetin, myricetin, quercitrin, and avicularin (Cunningham
et al., 2004).
Catechin Monomers (Flavan-3-ols)
Cranberries contain high levels of flavanols or flavan-3-ols
(Fig. 3), which are also monomers of proanthocyanidin poly-
mers (PACs). Contents of individual flavanols in cranberries are
reported in Table 2.
Gu et al. (2004) detected 7.3 mg/100 g of total PAC monomer
in whole cranberries (variety not identified) and 6 mg/L in cran-
berry juice cocktail. However, which specific flavan-3-ols are
present in cranberries remains controversial, perhaps due to
differences among cranberry varieties and analytical methods.
Some evidence indicates that epicatechin (structure 22,Fig.
3) is the primary and perhaps only free flavanol in cranberry
juice (Cunningham et al., 2004), while catechin (structure 23,
Fig. 3) was the only flavanol found in commercial cranberry
juice cocktail and whole juice (Chen et al., 2001). Recently,
gallocatechin gallate (0.4 mg/100 g), catechin (0.8 mg/100 g),
epigallocatechin (1.5 mg/100 g), epigallocatechin gallate (1.9
mg/100 g) and larger amounts of catechin gallate (7.9 mg/100
g) have been reported to be present in whole cranberries after
hydrolysis (Harnly et al., 2006). However, these identifications
must be considered tentative since only HPLC-PDA was used
for characterization; whether these gallolyated flavan-3-ols are
reaction artifacts must also be determined.
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750 E. PAPPAS AND K. M. SCHAICH
Figure 4 Structures of proanthocyanidins identified in cranberries: procyanidin B2 (EC-(4β8, 2βO7)-EC) (24); procyanidin A2 (EC-(4β8)-EC)
(25); 3: EC-(4β6)-EC-(4β8, 2βO7)-EC (26);4:EC-(4β8, 2βO7)EC-(4β8)-EC (27); EC-(4β8-EC-(4β8,2 βO7)-EC (28)where
EC =epicatechin.
The total flavanol content of 7 mg/100 g fruit (Gu et al.,
2004) classifies cranberries as a moderate source of flavanols
in comparison to other fruits (ranging from 0–20 mg/100 g)
(Arts et al., 2000). While the intake of fresh cranberries or
canned cranberry sauce may be tied to season or entree, sweet-
ened dried cranberries and cranberry juices have become very
popular snacks and beverages eaten in much higher quantities.
Considering estimates of 30–70 mg/day total flavanol intake in
the United States (Gu et al., 2004) and 50 mg/day in the Nether-
lands (Arts et al., 2001), cranberries can thus provide a modest
but important dietary contribution of these micronutrients.
Proanthocyanidins (PACs)
One unique property of cranberries is their diverse group
of proanthocyanidins that exhibit several rare structural char-
acteristics (Fig. 4). Also known as condensed tannins, PACs
are defined as oligomers or polymers of flavan-3-ols. Structural
characteristics of PACs underlie multiple functions: polypheno-
lic structures promote antioxidant capacity while vicinal hy-
droxyl groups bind metals. Perhaps most distinctively, their
size, high molecular weight, and many free hydroxyl groups
allow PACs to interact with (and often denature or precipi-
tate) proteins. This activity in the saliva is responsible for the
astringent or bitter tastes from cranberry, wine, cocoa and other
PAC rich foods (Santos-Buelga and Scalbert, 2000). A recent
review by Prior and Gu (2005) compiles excellent informa-
tion about the types, the levels, and the health effects of these
bioactive phytochemicals in commonly consumed foods. Al-
though several individual cranberry proanthocyanidin species
have been identified, PACs so far have been quantitated only
by degree of polymerization and not individually (Table 2),
due to their structural heterogeneity and difficult analytical
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CRANBERRY PHYTOCHEMICALS 751
separation. Gu et al. (2004) report 23.1 mg/100 mL total PAC
in cranberry juice cocktail and 418 mg/100 g in fresh cranber-
ries (unspecified varieties). In comparison, among twenty-one
fruits evaluated, only chokeberry showed higher PAC contents.
The estimated total daily PAC consumption in the US is only
57.7 mg/person (Gu et al., 2004). Thus, even with only small
portions, cranberries certainly have the potential to be a major
dietary source of these phytochemicals.
Structural diversity and the lack of analytical standards pose
significant challenges for PAC research. Cheynier (2005) notes
that there are nx(n-1)ypossible PACs for an n-mer with x types
of constitutive units and y types of linkages. Cranberry PACs
contain three constitutive units [epicatechin (EC), epigallocate-
chin (EGC) and catechin] (Foo et al., 2000a; Gu et al., 2003a;
Reed et al., 2005) and at least three types of linkages: two com-
mon B-type linkages (C4C6 and C4C8) and the relatively
uncommon A-type ether linkage (C2OC7) (Foo et al.,
2000a). Degrees of polymerization as high as 23 have been ob-
served in cranberries (Reed et al., 2005). Applying Cheynier’s
model to cranberry PACs yields a dramatic figure close to half a
billion (483,833,152) different polymers possible. Even though
only a miniscule portion of the individual PACs from this model
appear to be present in cranberries (e.g. only a handful of the
216 theoretically possible trimers have been observed), their
immense heterogeneity remains evident.
Research has only begun to scratch the surface in elucidat-
ing structures of individual cranberry PACs, despite intensive
research. Isolation of single chemical species and analyses by
LC-MS, NMR, and chemical degradation have positively char-
acterized only a few cranberry PACs. These methods have iden-
tified two procyanidin dimers: A2 (EC-(4β8, 2βO7)-
EC) (structure 24, Fig. 4) and B2 (EC-(4β8)-EC) (structure
25, Fig. 4) as well as three A-type procyanidin trimers: EC-
(4β6)-EC-(4β8, 2βOto7)-EC (structure 26,Fig.4),
EC-(4β8, 2βOto7)EC-(4β8)-EC (structure 27,Fig.
4) and EC-(4β8)-EC-(4β8,2βO7)-EC (structure 28,
Fig. 4) (Foo et al., 2000b). Even more prevalent are PAC
tetramers and pentamers composed of predominantly epicat-
echin units, with epigallocatechin and catechin extending units,
and mostly A-type terminal units in cranberry extracts (Foo
et al., 2000a).
Beyond these, characterizations of cranberry PACs have re-
lied almost entirely upon mass spectral techniques and chem-
ical degradation of mixtures of PACs. MALDI-MS currently
seems to be the analytical instrument of choice to character-
ize heterogeneous polymers such as cranberry PACs. While
these methods can not fully reveal chemical configurations of
individual species, they yield crucial information: DP, type of
constitutive units, number of A-type linkages and estimations
of the distributions of each. Employing such methodology, sev-
eral reports have documented multiple procyanidin polymers
with DP of 4>10>, most including one to multiple A-type
linkages, but some with only B-type linkages (Porter et al.,
2001; Prior et al., 2001; Gu et al., 2002, 2003a, 2004; Howell
et al., 2005; Reed et al., 2005; Neto et al., 2006). Epicate-
chin units are dominant but EGC units are also present (Foo
et al., 2000a; Porter et al., 2001; Howell et al., 2005; Reed
et al., 2005; Neto et al., 2006); data verifying the presence of
catechin units in cranberry PACs is more limited (Foo et al.,
2000a; Gu et al., 2003a; Gu et al., 2003a). This apparent dis-
crepancy in findings regarding the constitutive monomer units
of cranberry PACs is intriguing and is perhaps due to cultivar
variations.
Estimates of average degree of polymerization in cranberry
PACs range from 4.7 (Foo et al., 2000a) to 8.5 (Gu et al., 2003a).
The latter estimate is likely more accurate since Foo’s extraction
procedure may exclude larger PACs. A-type linkages dominate
in cranberry PACs; an estimated 51–65% of cranberry PACs con-
tain at least one A-type linkage, with most of these ether linkages
in the terminal units (Foo et al., 2000a; Gu et al., 2003a). The
terminal A-type bonds common to cranberry PACs are quite rare
in foods: peanuts and plums are the only other foods containing
them, although at substantially lower levels (Gu et al., 2002,
2003a; Prior and Gu, 2005). Similarly, PACs containing both
terminal and extension A-type linkages are unique to cranber-
ries and peanuts (again at low concentrations); these were not
found in any other of 88 foods tested (Gu et al., 2003a; Gu et al.,
2004). While no estimations of average intake are available for
A-type PACs, cranberry certainly is among the richest source of
these rare phytochemicals in the American diet.
Flavanones
Flavanones have only recently been identified in cranberries.
Prunin (naringenin 7-glucoside) was isolated from cranberry
juice concentrate in modest amounts (1.5 ppm) and character-
ized by NMR (Turner et al., 2005). Although it was found in a
cranberry fraction that exhibited anti-adhesive activity towards
uropathogenic bacteria, isolated prunin did not exhibit similar
activity.
Nonflavonoid Polyphenols
Although largely overshadowed by the flavonoid compo-
nents, nonflavonoid polyphenols also contribute to the biologi-
cal effects of cranberries. Perhaps best known of these phenols
is the bioactive stilbene, resveratrol. Despite intense publicity
on the antioxidant activity of resveratrol in red wines, there
has been surprisingly little research on this active compound
in cranberries. HPLC-MS identified trans-resveratrol (structure
30, Fig. 5), the isomer with the highest bioactivity, in raw cran-
berry juice at 0.2 mg/L (1.91 nmol/g) (Wang et al., 2002);
levels were comparable to those found in grape juice (0.05 to
0.5 mg/L depending on variety) though lower than in red wine
(as high as 14 mg/L ) (Baur and Sinclair, 2006). Thus, cranber-
ries can be an important dietary source of this phytochemical.
It is likely that cranberries contain predominantly bound
forms of resveratrol. Wang et al. (2002) used β-D-glucosidase
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752 E. PAPPAS AND K. M. SCHAICH
Figure 5 Structures of selected non-flavonoid polyphenols in cranberries:
2-O-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxyphenylmethylacetate (29); trans-
resveratrol (30)andSECO(31).
digestions before extraction, so the trans-resveratrol reported
probably includes bound forms of the polyphenol, such as trans-
piceid (resveratrol-3-O-β-D-glucoside). Piceid has been iden-
tified in grapes, as well as other foods (Baur and Sinclair, 2006)
and may exert health effects similar to those of resveratrol, as
well as some distinctive ones.
Cis-resveratrol is present in cranberry juice in lower concen-
trations (0.14 nmol/g juice) (Wang et al., 2002). Total resveratrol
levels of 900 ng/g (dry weight) in lyophilized wild cranberries
from Canada (Rimando et al., 2004) and 0.19 mg/g (dry weight)
in cranberry powder (Vattem et al., 2006) have been reported.
Other phenols identified in cranberry juice concentrate
include phloridzin (phloretin 2-glucoside) (Turner et al.,
2005), a dihydrochalcone known for its antioxidant capac-
ity and abundantly occurring in apples (Lotito and Frei,
2004), and a novel depside, 2-O-(3,4-dihydroxybenzoyl)-2,4,6-
trihydroxyphenylmethylacetate (structure 29, Fig. 5) (Turner
et al., 2007). Whole cranberry fruit has low concentrations of
ellagic acid (120 ug/g dry weight) (Daniel et al., 1989) and the
lignan SECO (secoisolariciresinol) (10.54 mg/kg dry weight)
(structure 31, Fig. 5) (Mazur et al., 2000). SECO, a phytoe-
strogen found mostly in glycoylated forms, required extensive
hydrolysis for release from the berry tissue. The levels present
in cranberries are intermediate relative to other berries, but high
in comparison to other fruits and plant foods.
Additional research is warranted to verify the concentrations
of these promising phytochemicals in cranberry products, to de-
termine their variability across cranberry varieties and products,
and to investigate their individual health effects.
Simple Phenolics and Benzoates
Simple phenolics and benzoates are important aromatic
phytochemicals providing potent antioxidant and antimicrobial
activity as well as strong odors and aromas. Benzoates, in par-
ticular, are present in cranberries at unusually high levels. Sur-
prisingly, little attention was given to simple phenolics and ben-
zoates of cranberry until recently, despite extensive studies of
these compounds in apples, citrus fruits, and other berries (Zuo
et al., 2002). Current data on the simple aromatics in cranberry
are presented in Table 2; representative structures are shown in
Table 4.
Tab le 4 Structures of selected phenolic and hydroxycinnamic acids from
cranberries
Structure # Name R1R2R3
Phenolic acids
32 benzoic acid H H H
33 salicylic acid OH H H
34 2,4-dihydroxy benzoic acid OH H OH
35 vanillic acid H OCH3OH
trans-Cinnamic acids
36 trans-Cinnamic acid H H H
37 p-coumaric acid H OH H
38 caffeic acid OH OH H
39 ferulic acid OCH3OH H
40 sinapic acid OCH3OH OCH3
Unlike most fruit juices, aromatic compounds rather than
terpenes dominate the active odor fraction of cranberry juice.
Croteau and Fagerson (1968) identified the following fifteen
volatile aromatics in cranberry juice by GC retention times and
mass spectrometry:
most abundant – benzoic acid (structure 32, Table 4)
benzyl alcohol
benzaldehyde
benzyl benzoate
2-phenyl ethanol benzoic acid
lower concentrations – 4-methoxy benzaldehyde
2-phenyl ethanol
dibutyl phthalate
2-hydroxy diphenyl
methyl benzoate
ethyl benzoate
benzyl formate
benzyl ethyl ether
benzene
acetophenone.
Eugenol and anisaldehyde are also present (Duke, 1992).
The soluble phenolic fraction of cranberries contains a large
number of compounds that undoubtedly contribute to the an-
tioxidant capacity of cranberries and cranberry products. Low
total benzoates (0.1% of fresh weight) were initially reported
(Marwan and Nagel, 1986). However, more sensitive instru-
mentation has revealed a much more diverse profile of ben-
zoates and simple phenolics, verified unusually high levels in
cranberry juice, and confirmed that phenolics and benzoates
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CRANBERRY PHYTOCHEMICALS 753
in cranberries are mostly bound forms, esterified to sugars, cell
wall polysaccharides, or other components. Less than 50% (most
at <10%) of the benzoates and simple phenols are present in
their free form (released without hydrolysis) (Zuo et al., 2002).
Indeed, hydrolysis is often required for the detection of sim-
ple phenols, and the compounds released appear to be specific
for the hydrolysis method used, perhaps because they are re-
leased from different binding sites. For example, fresh cran-
berry juice had 41 mg/L benzoic acid in free form, while total
benzoic acid (free +bound) after acid hydrolysis increased
to 178 mg/L (Chen et al., 2001). Acid hydrolysis also re-
leased p-anisic acid (2.2 mg/L) in fresh cranberry juice as
well as chlorogenic acid (structure 41, Table 4) (5.1 mg/L)
and p-coumaric acid (structure 37, Table 4) (5.2 mg/L) in
canned cranberry juice (Chen et al., 2001). Alkaline hydrolysis
of cranberry juice cleaved salicylic acid (7.04 mg/L) (Duthie
et al., 2005), while enzymatic hydrolysis of cranberry po-
mace generated gallic acid, chlorogenic acid, p-hydroxybenzoic
acid, and p-coumaric acid as major products (Zheng and
Shetty, 2000). This single report of gallic acid monomer in
cranberry products is very interesting considering the pres-
ence of gallic acid substitutions in cranberry flavanols and
proanthocyanidins.
With and without acid hydrolysis, GC-MS analysis found
significantly high levels of free and bound benzoic and other
phenolic acids (0.57% wet weight) in fresh cranberries (Zuo
et al., 2002). Benzoic acid (0.47%) accounted for the majority
of this fraction, with lesser amounts of fourteen other phenolic
and benzoic acids (Zuo et al., 2002) (Table 4):
Bound o-hydroxybenzoic acid (salicylic acid) (structure 33,
Table 4)
p-hydroxyphenylacetic acid
2,3-dihydroxybenzoic acid
hydroxycinnamic acids
Free trans-cinnamic acid (structure 36, Table 4)
m-hydroxybenzoic acid
p-hydroxybenzoic acid
o-phthalic acid, vanillic acid (structure 35, Table 4)
2,4-dihydroxybenzoic acid (structure 34, Table 4).
Of hydroxycinnamic acids, p-coumaric acid and sinapic acid
(structure 40, Table 4) are most prevalent, but significant
amounts of caffeic acid (structure 38, Table 4) and ferulic acid
(structure 39, Table 4) are also present.
The molecular sites of phenol binding in cells appear to be
mostly saccharides, but the preference and distribution between
low molecular weight glycosides and more complex polysac-
charides is not yet clear. Most phenols appear to be bound
to low molecular weight species, e.g. linked to mono and di-
saccharides by ether or ester bonds. Complexed forms iden-
tified in cranberry extracts or juice concentrates include hy-
droxycinnamic acid esterified to ursolic acid (Murphy et al.,
2003; He and Liu, 2006), coumaric acid bound to iridoid glyco-
sides (Turner et al., 2007), benzoic acid and hydroxycinnamic
acid esterified to mono- and di-saccharides (Marwan and Nagel,
1982, 1986; Heimhuber et al., 1990; He and Liu, 2006; Mullen
et al., 2007), and glycosylated derivatives of p-coumaric, caf-
feic, ferulic and sinapic acids (Marwan and Nagel, 1982), vac-
ciniin (6-benzoyl-D-glucose) (Marwan and Nagel, 1986), and
three additional glycosylated benzoic acid isomers (Heimhu-
ber et al., 1990). Vvedenskaya et al. (2004) similarly isolated
and characterized simple phenolic compounds bound to sev-
eral flavonol glycosides in cranberry powder. All these newly
identified compounds are rare and several appear unique to
cranberries.
Other work suggests a significant proportion of cranberry
phenolics are bound to complex carbohydrates or other macro-
molecules. Zhang and Shetty (2000) used pure β-D-glucosidase
as well as crude enzymatic extracts from L. edodes to re-
lease phenolics from cranberry pomace, which is composed
of mostly insoluble fiber. That the crude enzyme containing an
esterase (α-L-arabinofuranosidase, α-L-rhamnosidase, and/or
β-D-apiosidase) produced notably higher yields of phenolics
than did pure β-D-glucosidase suggests that most of the phe-
nolics in cranberry pomace are bound to more complex car-
bohydrates and/or more diverse chemical species, potentially
including substituted proanthocyanidins (PACs). These com-
plex carbohydrate-phenolic acid esters and substituted PACs
are heterogeneous in structures and linkages, making it difficult
to isolate individual species for characterization. Still, the com-
plexes may be present in the high molecular weight fraction of
cranberry juice that has been the subject of significant research
(Section titled High Molecular Weight Fraction (NDM)), and
they also are likely to have some biological activity, especially
as antioxidants. Further research is needed to fully elucidate
the nature and health effects of low molecular weight bound
phenolics from cranberries.
Nonphenolic Organic Acids
Nonphenolic organic acids (Table 2 and Fig. 6) are significant
components of cranberries, accounting for 2.67–3.65% w/v of
the berry tissue (Jensen et al., 2002) and 2.75% w/w of whole
cranberry juice (Hong and Wrolstad, 1986a). The three primary
nonvolatile organic acids—quinic acid (structure 41,Fig.6),
citric acid, and malic acid of cranberry juice (Coppola et al.,
1978; Coppola and Starr, 1986; Hong and Wrolstad, 1986a)
are present in very consistent ratios (1:1:0.75, respectively).
Figure 6 Structures of selected non-volatile organic acids from cranberries:
quinic acid (41), shkimic acid (42) and the methyl ester of tartaric acid (43).
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754 E. PAPPAS AND K. M. SCHAICH
These ratios together with the uniquely high content of quinic
acid in cranberries form the basis for the HPLC-UV assay used
extensively in the cranberry juice industry today to detect the
adulteration in cranberry juice products.
Ascorbic acid (vitamin C) has many reported health bene-
fits as an antioxidant and nutrient and its dietary deficiency is
widely known to cause scurvy. Vitamin C is present in whole
cranberries at concentrations that are moderate (11.5 mg/100
g) (Licciardello et al., 1952) but sufficient to prevent scurvy
among early American settlers (Henig and Leahy, 2000). Ascor-
bic acid levels in cranberry juice cocktail and sauce are lower
(2–4 mg and 1 mg/100 g, respectively) (Licciardello et al., 1952;
Cunningham et al., 2004; Starr and Francis, 1968) or absent
(Hong and Wrolstad, 1986a). Hence, cranberry products are
often fortified with vitamin C to meet consumer expectations.
Lower levels of shikimic acid (0.1–0.9 g/100 ml) (structure
42, Fig. 6) (Hong and Wrolstad, 1986a) and galacturonic acid
(0.19 g/100 ml) (Cunningham et al., 2004) as well as trace
amounts of tartaric acid and its methyl ester (structure 43,Fig.
6) (He and Liu, 2006) have been found in whole cranberry juice.
Galacturonic acid is thought to accumulate from commercial
enzymatic depectinization (Cunningham et al., 2004). These
acids have been well characterized and quantified by 1H and
13C NMR and MS (He and Liu, 2006).
Cranberry juice cocktail is generally standardized to 0.5%
titratable acidity. It is this high acidity, similar to that of lemon, as
well as the low content of natural sugars (Section titled Sugars)
that demands the sweetening of cranberry products to reduce
astringency and enhance natural flavors. While vital to flavor,
organic acids other than vitamin C are not known to have im-
portant health effects.
Figure 7 Ursolic acid (44) and its derivatives, cis-andtrans- 3-O-p-hydroxy
cinnamoyl ursolic acid (45 and 46), found in cranberries.
Figure 8 Iriodoid glycosides from cranberries: monotropein (47), 6,7 dihy-
dromonotropein (48) and 10-p-cis-coumaroyl-1S-dihydromonotropein (48).
Terpenes, Sterols, and Terpene Derivatives
Terpenes and terpene derivatives such as nerol, limonene,
linalool, myrcene, α-pinene, β-pinene and especially α-
terpineol are responsible for much of the flavor and aroma
of cranberries (Croteau and Fagerson, 1968). Table 2 lists the
component terpenes of cranberries, and their quantities, when
known. Figures 7 and 8 shows selected terpene molecular struc-
tures. These odorants are common in foods and are used ex-
tensively as food flavoring additives, so do not likely elicit the
health effects unique to cranberry.
Ursolic acid (structure 44, Fig. 7), a pentacyclic triterpene,
identified in cranberries more than half a century ago (Wu and
Parks, 1956), has more recently attracted attention for its poten-
tial anticancer effects (He and Liu, 2006). Two rare hydroxycin-
namic derivatives of this triterpene were also recently isolated
by HPLC and identified by MS as well as 1H and 13CNMR
in cranberry: cis- and trans- 3-O-p-hydroxy cinnamoyl ursolic
acid (structures 45 and 46, Fig. 7) (Murphy et al., 2003; He
and Liu, 2006). Recently, 60–110 mg/100 g ursolic acid was
quantified in whole cranberries of different cultivars (Kondo,
2006).
He and Liu (2006) also isolated two sterols, β-sitosterol, and
β-sitosterol-3-O-β-D-glucoside, from whole cranberry fruit us-
ing bioactivity guided fractionation and identified the structures
by MS and 1H and 13C NMR. These compounds are widely
distributed in plants but may nonetheless contribute subtly to
cranberry health effects (He and Liu, 2006).
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CRANBERRY PHYTOCHEMICALS 755
Another study revealed the presence of two related iri-
doid glycosides: monotropein (structure 47, Fig. 8), and 6,7-
dihydromonotropein (structure 48, Fig. 8) by HPLC-NMR
and HPLC-MS (Jensen et al., 2002). The isolated amounts
correspond to about 0.01% w/v each in whole cranberry
juice. Two isomeric derivatives of 6,7-dihydromonotropein
[10-p-cis-(structure 49, Fig. 8) and 10-p-trans-coumaroyl-1S-
dihydromonotropein] have been recently isolated and charac-
terized from cranberry juice concentrate (Turner et al., 2007).
Aside from monotropein, these iridoid glycosides are novel and
may be unique to cranberry, although they have not been linked
to health effects (Jensen et al., 2002; Turner et al., 2007).
The terpene fraction of cranberry has only very recently at-
tracted considerable research attention beyond its odor contribu-
tions, and several exotic chemical species have been identified.
Future research will reveal whether or not these interesting phy-
tochemicals contribute to the health benefits of cranberries.
Complex Carbohydrates
Consumption of complex carbohydrate fibers has been as-
sociated with a number of health benefits, none of which are
typical of cranberries. Because of this, or perhaps because cran-
berry juice (with little fiber) is the major form of cranberry
consumption, complex carbohydrates of cranberries have been
largely ignored. Cranberry pomace solids are 35% insoluble
fiber (USDA-ARS, 2004), the pectins of which are largely
responsible for cranberry sauce gelation, and more extensive
utilization of fiber by-products has recently been the focus of
some research (Zheng and Shetty, 1998, 2000; Park and Zhao,
2006; Raghavan and Richards, 2007).
Not surprisingly, an early investigation into the cell wall com-
position of cranberries revealed the presence of cellulose, pectin,
and hemicellulose in cranberry pomace (Holmes and Rha,
1978). The alcohol insoluble fraction of lyophilized berries is
mostly protopectin (54–67%, with lower levels of high methoxy
pectin (10–18%); overall degree of esterification in the pectins
is 47.7–57.5% depending on variety (Stuckrath et al., 1998).
The soluble fiber fraction of cranberries contains monomer
units mostly of arabinose, glucose and galactose/rhamnose, with
lesser amounts of xylose and mannose (30, 28, 21, 11, and 10%
respectively) (Marlett and Vollendorf, 1994).
Although whole cranberry juice, like most juices, contains
very little fiber (0.1%) (Cunningham et al., 2004), cranberry
sauce contains substantial levels, 1%, of these insoluble car-
bohydrates (Marlett and Vollendorf, 1994). Interesting data sug-
gesting covalent interactions between complex carbohydrates
and phenolics in cranberries (Zheng and Shetty, 2000) was dis-
cussed above (Section titled Phenolic Acids and Benzoates).
Such interactions may improve the potential health benefits of
these fibers as well as provide functionality to products derived
from them. Indeed, edible films with unique properties, such as
natural bright color and antioxidant activity, have been devel-
oped from cranberry pomace (Park and Zhao, 2006).
High Molecular Weight Fraction (NDM)
Numerous studies have reported substantial health effects
from the high molecular weight fraction of cranberry, known
as cranberry nondialyzable material or NDM (Zafriri et al.,
1989; Ofek et al., 1991; Ofek et al., 1996; Weiss et al., 1998;
Burger et al., 2002; Shmuely et al., 2004; Shmuely et al., 2007;
Weiss et al., 2004; Steinberg et al., 2005; Weiss et al., 2005;
Steinberg et al., 2005; Bodet et al., 2006a, 2006b; Labrecque
et al., 2006; Bodet et al., 2007a). NDM is prepared by dialysis
of fresh cranberry juice or cranberry juice concentrate with MW
cut off of 12,000–15,000, often at refrigerated temperatures.
Ofek et al. (1996) described NDM as tannic in nature; soluble
in water; free of proteins, carbohydrates, and fatty acids; and
composed of 4.14% hydrogen and 56.6% carbon. Others found
that NDM contains no sugars or acids but consists of 0.35%
ACY and 65.1% PAC (Bodet et al., 2006a; Bodet et al., 2006b).
It seems likely that cranberry NDM is a heterogeneous mixture
of condensed phenols and flavonoids whose structural variabil-
ity will prevent any concrete structural elucidation. Whether
this elusive fraction is naturally in cranberries or results from
processing is also unknown. Further characterization is needed
to more fully understand its observed activities.
HEALTH EFFECTS OF CRANBERRIES, THEIR
PRODUCTS, AND COMPONENTS
Numerous health benefits have been associated with cran-
berry consumption. Unique to cranberries among foods are anti-
pathogenic effects including:
Prevention of urinary tract infections
Clearance of stomach pathogens
Disruption of oral pathogen virulence and biofilm formation
Depression of viral infectivity in vitro
Cranberries have also been shown to inhibit progression of
degenerative disease and loss of functionality, with the following
health benefits:
Inhibition of Alzheimer’s disease development and neural de-
generation
Promotion of cardiovascular health
Prevention and inhibition of cancer
Modulation of inflammatory responses
Scientific evidence supporting these health effects varies
greatly. The following sections will provide brief overviews of
each disease state and discuss observations from epidemiologi-
cal, in vitro, ex vivo, and in vivo data affirming or refuting the
reported health benefits. Special emphasis will be given to the
specific phytochemicals implicated in each action. Molecular
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756 E. PAPPAS AND K. M. SCHAICH
mechanisms will be considered in Section titled Molecular
Mechanisms Underlying Health Effects.
Urinary Tract Infections
Best-known and most extensively documented of cranberry
health effects is prevention of urinary tract infections (UTIs).
Occurring primarily in women, UTIs are surprisingly common
and quite costly. An estimated 11.3 million women (about one
in ten women) in the United States per year contract infections,
at a cost of $1.6 billion annually (Foxman et al., 2000). Even
more troublesome, UTIs are often recurring: 26.6% of women
with a UTI were confirmed to have a second infection within 6
months (Foxman, 1990).
Cranberries have long been a folk remedy for UTIs, and
science is now providing both verification of cranberry effi-
cacy and explanations for cranberry actions. Clinical trials have
convincingly demonstrated reduced bacteriuria and/or lowered
occurrence of UTIs in groups of women consuming cranberry
products including juices, extracts, and powders on a daily basis
for at least several weeks (Avorn et al., 1994; Walker et al., 1997;
Kontiokari et al., 2001; Stothers, 2002; Bailey et al., 2007). A
recent meta-analysis of clinical data revealed a relative risk of
0.65 for symptomatic UTIs and 0.61 for recurrent UTIs for sub-
jects consuming cranberry products as compared to control or
placebo groups (Jepson and Craig, 2007). A case-control study
of 324 adult women with and without previous UTIs found that
those who consumed more fruit juice, berry juices in particular,
faced significantly lowered risk of contracting UTIs. Odds ratios
(OR)1were reduced from 1 (equal incidence) to 0.66 (p <0.011)
after consumption of just over 200 mL juice per day, and the ef-
fect was enhanced even further (OR =0.28, p <0.001) among
subjects who preferred berry juices (including cranberry, lin-
gonberry, blueberry, raspberry, strawberry, currant, and cloud-
berry) over other juices (Kontiokari et al., 2003). Within this
group, even occasional cranberry consumption (<1 serving per
week) was associated with lowered risk of UTI (OR =0.48,
p<0.03). Statistical analysis of regular consumption of cran-
berry was not possible because none of the 139 women in the
study with a recent UTI had consumed more than one serving
of cranberry juice per week.
UTI effects of cranberries appear to be specific for or most
pronounced in women. Groups at increased risk for contracting
UTIs, including children, the elderly, and patients needing inter-
mittent catheterization, have shown little or no benefit from cran-
berry product supplementation (Avorn et al., 1994; Haverkorn
and Mandigers, 1994; Foda et al., 1995; Schlager et al., 1999;
Linsenmeyer et al., 2004; Waites et al., 2004; McMurdo et al.,
2005; Jepson and Craig, 2007). In addition, cranberry effects
1Odds ratios were calculated from comparison of regression curves relating various
dietary fators to UTI incidence for subjects with previous UTIs compared to paired sunjects
without previous UTIs. For specific fruit comparisons, an OR of 1 was the risk assigned to
subjects who never consumed the fruit.
against UTI appear to be exclusively prophylactic but not ther-
apeutic, preventing the development of infection but inactive
against existing UTIs.
How do cranberries prevent development of UTI’s? Es-
cherichia coli is the pathogen responsible for the most UTIs,
accounting for 75–95% of infections (Gupta et al., 2001; Jepson
and Craig, 2007). The use of antibiotics to treat recurrent in-
fections increases pathogen resistance to them, so that resistant
strains now account for 7–60% of infections (Gupta et al., 2001;
Jepson and Craig, 2007). As currently understood, UTIs begin
in the periurethral tissue where bacteria colonize. Protein-based
adhesins or lectins expressed on the surface of these bacte-
ria bind to glycoproteins and/or glycolipids on host cell sur-
faces, allowing for subsequent colonization (Sharon and Ofek,
2002) in the urinary tract and finally in the bladder (Jepson and
Craig, 2007). In the case of uropathogenic E. coli, these lectins
have been identified as primarily mannose binding type-1 ad-
hesins and in some strains, additionally, the galabiose-binding
P-fimbriated adhesins (Beachey, 1981). This pathogen-host cell
interaction is essential to infection, since innate cleansing mech-
anisms such as urine flow will otherwise flush pathogens from
the bladder and urinary tract. In the face of increasing antibi-
otic resistance, the failure of antibiotic treatments to prevent
recurring infections, and high costs associated with UTIs, alter-
native therapies like supplementation of cranberry products are
increasingly attractive.
Until recently, anti-UTI action was ascribed to cranberry’s
high acid content and acidification of urine. Sobota (1984) then
found that when mice and humans were fed cranberry juice
cocktail, their urine inhibited adherence of diverse strains of
clinically isolated E. coli to uroepithelial cells ex vivo. This
ex vivo action has been verified and strikingly demonstrated to
be dose-dependent in a placebo-controlled, double-blind clin-
ical trial (Di Martino et al., 2006): as little as 250 mL daily
intake of cranberry juice cocktail inhibited adhesion to uroep-
ithelial cells by 45% (p <4.9 ×1012), while 750 mL reduced
adhesion by 63% (p <2.6 ×1018). Exposing uroepithelial
cells to cranberry juice directly in vitro inhibited adhesion of
E. coli expressing both 1-type and P-type fimbriae, but not an-
other adhesin from a diarrheal isolate (Zafriri et al., 1989; Ofek
et al., 1991). (Zafriri et al., 1989; Ofek et al., 1991). The action
occurs also in vivo,as demonstrated by reduced bacteriuria ob-
served in women consuming cranberry products (Avorn et al.,
1994).
That prevention of bacterial adhesion to epithelial cells in the
urinary tract is a major action of cranberries now seems clear.
However, many questions about cranberry anti-UTI activity re-
main unanswered. There is considerable controversy over which
components in cranberry juice are actually responsible for the
anti-adhesion activity. Early studies attributed activity to fruc-
tose for the 1-type adhesin and the high molecular weight NDM
fraction for the P-fimbriated adhesin because of their in vitro
activity (Zafriri et al., 1989). Recently attention has shifted to
proanthocyanidins. Lower molecular weight A-type cranberry
PACs were reported to inhibit binding of P-fimbriated (but not
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CRANBERRY PHYTOCHEMICALS 757
1-type) E. coli in vitro (Howell et al., 1998; Foo et al., 2000a,
2000b; Howell et al., 2005; Howell, 2007).
Inconsistency of in vitro and ex vivo data with bioavail-
ability of cranberry phytochemicals poses a serious limitation
to elucidating mechanisms. While fructose is active in vitro
and is absorbed, in vivo it is preferentially utilized in other
metabolic pathways. Indeed, feeding of fructose-rich apple and
grape juices failed to promote anti-adhesion properties in urine
ex vivo (Howell et al., 2005). After cranberry consumption, col-
lected urine clearly inhibits adhesion of both 1-type and P-type
E. coli ex vivo (Sobota, 1984; Di Martino et al., 2006). However,
in vitro NDM is clearly inactive against 1-type E. coli (Zafriri
et al., 1989) and PAC activity has not been reported. In inhibiting
adhesion of P-type E. coli, isolated individual cranberry PACs
were active at as low as 0.3 mg/mL and mixed cranberry PACs
were active at as low as 75 µg/mL in vitro (Foo et al., 2000a;
Foo et al., 2000b). High ppm concentrations such as these, if
absorbed, should easily be detected with modern analytical tech-
nology. Nevertheless, these components have not been isolated
(in any amount) in urine after consumption of cranberry products
(see Section titled Bioavailability and Metabolism of Cranberry
Phytochemicals), casting great doubt on their activity against
UTIs in vivo (Valentova et al., 2007; Vorsa et al., 2007a). Thus,
cranberry components active against UTIs in vivo remain a mys-
tery, and are perhaps unknown metabolites of PACs (Howell,
2007) or other, yet to be identified, components.
Even though anti-UTI effects may be limited to women,
cranberry foods remain unique as the only nutritional therapies
clearly demonstrated to be effective in preventing an infectious
disease (Donabedian, 2006). The UTI-cranberry association is
so strong that the French health agency AFSSA has recently
allowed certain cranberry juices, powders, and concentrates to
be marketed as urinary health promoters—the first instance of
a government sponsored, specific health claim allowed for an
individual fruit.
Much must still be learned about the molecular chemistry
underlying gender specificity, inhibition of bacterial adhesion,
and other potential mechanisms by which cranberry components
prevent urinary tract infections. Direct molecular mechanisms
are proposed in the Section titled Molecular Mechanisms Under-
lying Health Effects, but none of these has yet been proven. Con-
tinuing studies are needed to answer these fundamental ques-
tions as well as identify adequate minimum dosage required and
minimum duration of supplementation for effective treatment.
Gastrointestinal Disease
Accumulating evidence indicates that cranberries also pre-
vent adhesion of the stomach pathogen Helicobacter pylori
(Burger et al., 2000, 2002; Shmuely et al., 2004; Shmuely et al.,
2007; Lin et al., 2005; Vattem et al., 2005). Stomach ulcers and
cancers were traditionally attributed to noninfectious mecha-
nisms because the stomach is highly acidic and thus hostile
environment to bacteria. However, H. pylori have recently been
implicated as the primary cause of these diseases. H. pylori
is ubiquitous, with incidence as high as 90% in some popula-
tions; it is now estimated to cause 60–90% of all gastric cancers
(Malfertheiner et al., 2005). In 2005 B.J. Marshall and J.R.
Warren were awarded the Nobel Prize in Medicine “for their
discovery of the bacterium Helicobacter pylori and its role in
gastritis and peptic ulcer disease.
Like uropathogenic E. coli,H. pylori attach to host cells via
adhesions expressed on the bacteria’s surface. Many such ad-
hesions have been identified in H. pylori, where they facilitate
binding to gastric mucus and erythrocytes as well as epithe-
lial cells (Burger et al., 2000, 2002). While the gastric mucus
layer is its most common habitat, it is believed that H. pylori
must penetrate that mucus layer over multiple generations and
bind to the epithelial cells to cause gastritis and cancer (Burger
et al., 2000). Conventional treatment with two antibiotics and
a proton pump inhibitor (amoxicillin, clarithromycin, omepra-
zole, respectively) is about 85% effective (Shmuely et al., 2007).
Higher eradication rates are desired, but antibiotic resistance is
already a serious concern and higher antibiotic levels would
only increase this risk (Dunn et al., 1997).
Observations that cranberry components inhibit H. pylori ad-
hesion to gastric mucosal cells in vitro offer promise that cran-
berries may prevent the disease altogether or at least reduce the
antibiotic levels required to control it. Cranberry NDM were first
shown to prevent adhesion of H. pylori to gastric mucosal con-
stituents, gastric cell lines, and erythrocytes (Burger et al., 2000,
2002); sialic acid-sensitive lectins binding cells to the mucosa
were the key targets. In a subsequent study, low concentrations
of cranberry NDM (0.2 mg/mL) inhibited the adherence of 53
of 83 clinically isolated strains of H. pylori to a human gastric
cell line, indicating that cranberry components must affect mul-
tiple but perhaps not all of the adhesions expressed by H. pylori.
Importantly, NDM inhibited a significantly higher percentage
of strains (64%) than did the antibiotic metronidazole (58%)
(Shmuely et al., 2004). Synergy between oregano and cranberry
constituents in inhibiting these bacteria has also been demon-
strated (Lin et al., 2005). Recently, promising clinical evidence
has emerged indicating that cranberries are also highly effec-
tive in preventing adhesion of H. pylori in vivo and thus may
inhibit critical steps in the pathogen’s virulence therapeutically.
In a randomized, double-blind, placebo-controlled trial involv-
ing 189 adults infected with H. pylori, daily consumption of
500 mL of cranberry juice cocktail resulted in a modest (14%)
though significant (p <0.05) decrease in infection relative to
placebo (5%) after 35 days, and the effect persisted through
the 90 day study (Zhang et al., 2005). These results are un-
precedented in demonstrating that consumption of a food was
effective in treating an existing pathogenic infection in vivo, not
just preventing it.
Gender specificity such as observed with UTI may also be
active for H. pylori inhibition. When cranberry supplementation
was combined with conventional drug cocktail therapy, female
patients, but not males, showed higher rates of H. pylori eradi-
cation (Shmuely et al., 2007).
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758 E. PAPPAS AND K. M. SCHAICH
Despite some notable advances, H. pylori’s mechanism of
infection and transmission remains poorly understood (Zhang
et al., 2005). One literature review suggests berry juices and/or
probiotic drinks may be effective, low cost treatments in control-
ling H. pylori (Gotteland et al., 2006). Perhaps most importantly,
cranberry remains extremely promising as a means to control
strains of H. pylori resistant to antibiotic therapies. However,
more research is needed to verify and clarify a number of criti-
cal issues: potential gender specificity, whether dietary supple-
mentation with cranberry products can prophylactically prevent
development of ulcers, how cranberries affect interaction of mi-
crobial cells with stomach tissues, whether cranberries present a
viable alternative to antibiotic treatment alone, or if antibiotics
and cranberry supplementation (perhaps along with probiotic
therapies) can be used in conjunction to increase therapeutic
efficiency.
Dental Health and Gum Disease
Cranberry products and components may reduce bacterial
infections in the mouth and thus prevent dental caries and
periodontal disease. Bacteria bind to teeth, then aggregate,
and cooperating oral bacteria secrete dental plaque biofilms.
These biofilms harbor the diverse oral pathogens that produce
acid, causing dental caries and eliciting inflammatory immune
reactions responsible for periodontal disease. Biofilms create a
habitat enabling bacterial reproduction in an environment pro-
viding protection from cleansing mechanisms. While Strepto-
coccus mutans and Streptococcus sobrinus are acknowledged
as the primary pathogens responsible for dental caries and Por-
phyromonas gingivalis is the primary pathogen in periodontal
disease, several hundred species of bacteria have been found
to inhabit the human mouth and may contribute to (or inhibit)
these disease states (Liljemark and Bloomquist, 1996). Cran-
berries and products derived from them may play important
roles in limiting plaque formation, dental caries, and periodontal
disease.
The first report investigating cranberry effects on dental
health revealed that both isolated cranberry NDM and cran-
berry juice (but not apple juice) prevented and reversed inter-
species co-aggregation of bacteria in vitro (Weiss et al., 1998).
2.5 mg/mL Cranberry NDM (approximately the concentration
in cranberry juice cocktail) inhibited co-aggregation in 58% of
the 84 oral bacterial pairs tested, suggesting that cranberry com-
ponents may prevent dental disease. These results were later
confirmed in a saliva matrix (Weiss et al., 2002). Prolifera-
tion of the periodontal pathogens Porphyromonas gingivalis,
Tannerella forsythia, and Treponema denticola and their pro-
teolytic virulence factors were inhibited by cranberry NDM in
vitro (Bodet et al., 2006b). Cranberry components also prevent
biofilm formation, adhesion of S. Sobrinus,S. mutans, P. gingi-
valis to tooth-like and oral cell surfaces, and acid production in
S. mutans (Steinberg et al., 2005; Duarte et al., 2006; Koo et al.,
2006; Labrecque et al., 2006). In suppressing S. mutans acid
production and biofilm formation, cranberry PACs were most
active, flavonol effects were intermediate, and ACYs were in-
active (Duarte et al., 2006). Inflammation responses stimulated
by isolated lipopolysaccharide were also dose-dependently in-
hibited by cranberry NDM in a model of periodontitis. Thus,
cranberry components appear to alleviate gum disease by host
interactions as well as the previously discussed pathogen in-
teractions (Bodet et al., 2007a). The cause of tissue damage
in gingivitis inflammation will be discussed further in Section
titled Anti-Inflammation.
In vivo evidence for cranberry contributions to dental health
is very limited. In a preliminary clinical trial, mouthwashes con-
taining NDM and used twice a day for 6 weeks lowered bacterial
counts of Streptococcus mutans by two orders of magnitude over
a control mouthwash (Weiss et al., 2002). While bioavailability
of compounds is not a limitation to activity in the mouth, col-
lection of more in vivo data seems justified, especially because
consumption of cranberry products is much different than us-
ing mouthwash. Clinical trials evaluating the effect of cranberry
juice supplementation on patients with periodontitis or high in-
cidence of dental carries may yield very interesting results.
It must be stressed that cranberry juice cocktail, if sweet-
ened with sugar, is not recommended for dental health pro-
motion since the sugar content facilitates rather than prevents
dental carries (Weiss et al., 1998). Instead, unsweetened or ar-
tificially sweetened cranberry products or isolated cranberry
components may provide effective therapies for dental health
improvement. Toothpastes supplemented with cranberry phyto-
chemicals (combinations of NDM, PACs and flavonols) as well
as mouthwashes consisting entirely of whole cranberry juice or
solutions fortified with cranberry components also seem promis-
ing as dental health promoters.
Antivirus Activity
That cranberries may significantly reduce infectivity of vi-
ral pathogens has only recently been recognized, so little data
detailing the action is yet available. Viruses are responsible for
some of the most innocuous infections, like the common cold, to
the most deadly, notably AIDS, so developing therapies against
viral pathogens is critically important. Currently available anti-
viral therapies are costly and only partially effective. Investiga-
tion of alternative therapies such as cranberry supplementation,
is clearly needed and may even provide greater insight into
mechanisms of infectivity and identification of potential treat-
ment targets.
In vitro cranberry NDM and isolated cranberry PACs in-
hibited adhesion and infectivity of influenza virus A (subtypes
H1N1and H3N2) and influenza virus B to human red blood cells
(Weiss et al., 2005). NDM activity was 5 times more potent on
a molar basis than isolated PACs (Weiss et al., 2005). In a study
of effects of three commercially available fruit juices on the
infectivity of several bacteriophages (A2 and A4) and a simian
rotovirus (SA-11), orange juice and grapefruit juice reduced the
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CRANBERRY PHYTOCHEMICALS 759
infectivity of the bacteriophages on E. coli by 20–35% over
60 minutes incubation time, but cranberry juice cocktail caused
90–100% reductions in infectivity almost immediately (Lipson
et al., 2007a). After treatment with cranberry juice, Simian ro-
tovirus did not infect African green monkey cells, in contrast
to the control, and hemagglutination was completely inhibited
(Lipson et al., 2007b). In monkey epithelial cell lines treated
with isolated cranberry phytochemicals, 25 to 2000 µg/mL
isolated proanthocyanidins and flavonols dose-dependently re-
duced infectivity of bovine reovirus after 3–5 minutes of incu-
bation time. High MW proanthocyanidins were more effective
than low MW proanthocyanidins; flavonols and cranberry juice
cocktail were mildly active and anthocyanins inactive (Lipson
et al., 2007b).
These observations demonstrate a nonspecific antiviral effect
exerted by cranberry juice and cranberry components (Lipson
et al., 2007a; Lipson et al., 2007b). Interestingly, anti-HIV ac-
tivity has been documented from several, rare plant flavonoids
(flavonols, flavonol glycosides, as well as prenylated and gal-
loylated flavonols) from exotic sources such as the bulbs of
the Chinese flower Chrysanthemum morifolium, the medici-
nal Korean herb Acer okamotoanum, and leaves of the African
rainforest tree Monotes africanus (Hu et al., 1994; Kim et al.,
1998; Meragelman et al., 2001). Inhibition of the enzyme HIV
integrase, vital to HIV’s ability to penetrate host cells, has
been proposed as a possible mechanism for anti-HIV activity
of flavonoids (Kim et al., 1998). Whether similar interference
with viral enzymes underlies the anti-viral properties of cranber-
ries is unknown, but some observations support the hypothesis
that cranberry components inhibit viral penetration of host cells
(Lipson et al., 2007a, 2007b). Viral RNA was not found within
cells incubated with cranberry juice and then challenged with
bovine reovirus (Lipson et al., 2007b), and electron microscopy
failed to detect intact Simian rotovirus in exposed MA-104
cultures after incubation with cranberry juice (Lipson et al.,
2007a).
Antiviral activity of cranberry products and components in
vivo has not yet been documented. Nevertheless, a greater un-
derstanding of the mechanisms involved could have tremen-
dous medical implications since available anti-viral therapies
are quite limited.
Cardiovascular Health
Cranberry consumption appears to modulate several
biomarkers of cardiovascular health and thus may reduce the
incidence of cardiovascular disease, similarly to moderate wine
consumption. A comprehensive discussion of the role of cran-
berries in cardiovascular health is available in a recent review by
Ruel and Couillard (2007). Briefly, atherosclerosis is believed
to be initiated by the gradual incorporation of oxidized lipopro-
teins into blood vessel walls, creating fatty lesions. Crucially,
surrounding endothelial cells then induce pro-inflammatory re-
sponses, including the expression of adhesion molecules (see
Section titled Anti-Inflammation), that recruit lymphocytes to
the sub-epithelial intima. These immune cells ingest the fatty
deposits, which may be cleared or, in the case of atheroscle-
rosis, eventually become encased in hardened plaques that re-
strict blood flow, resulting in hypertension and damage to the
heart. Even worse, they promote blood clotting (thrombosis)
or rupture, which may completely halt blood flow, resulting
in heart attack or stroke (Neto, 2007a; Ruel and Couillard,
2007).
Epidemiological data suggest a strong inverse correlation
between cardiovascular disease and consumption of fruits, veg-
etables, and flavanoid compounds (Hertog et al., 1993, 1995).
Flavonol intake, in particular, has been strongly associated with
lower rates of coronary disease mortality and stroke incidence
(Hollman and Katan, 1997, 1999). The consumption of
cranberries, a fruit with high flavonoid and especially flavonol
content, may then promote cardiovascular health, though this
effect has not been studied directly epidemiologically.
Oxidation of blood low density lipid protein cholesterol
(LDL) is believed to be a crucial step in the early develop-
ment of atherosclerosis. Moreover, high levels of LDL and low
levels of high density lipoprotein (HDL) are widely considered
strong risk factors for cardiovascular disease. That cranberries
and cranberry components inhibit LDL oxidation in vitro is not
surprising since so many cranberry phytochemicals are strong
antioxidants (Wilson et al., 1998; Porter et al., 2001; Vinson
et al., 2001; Chu and Liu, 2005).
Whether dietary consumption of cranberries is beneficial to
overall cardiovascular health is more controversial. Much in vivo
data show that cranberry consumption has antioxidant action im-
portant in combating cardiovascular disease. After a single 500
mL administration, cranberry juice cocktail (but not a control
drink or blueberry juice) significantly raised the plasma antioxi-
dant capacity (P <0.001) as measured by both the ferric reduc-
ing antioxidant potential (FRAP) assay and the Fremy’s salt rad-
ical reduction assay in female subjects (Pedersen et al., 2000).
Similarly, plasma antioxidant capacity increased after daily ad-
ministration of 660 mL of cranberry juice to male and female
volunteers for ten weeks: thiobarbituric acid reactive substances
(TBARS) in plasma were reduced significantly (P <0.05) from
3.56 (baseline) to 2.08 µM and oxidative lag time of harvested
LDL ex vivo was significantly (P <0.002) increased from 50.67
(baseline) to 60.67 minutes (Lu and Wang, 2006). In contrast,
the placebo group, who drank simulated cranberry juice with
the same level of vitamin C, exhibited more rapid ex vivo LDL
oxidation. In another study, drinking seven mL cranberry juice
per kg body mass per day for two weeks induced a significant
increase in plasma antioxidant capacity (AOC) (6.5%, P <0.02)
and reduction in circulating oxidized LDL content (∼−
10%,
P<0.02) in male volunteers (Ruel et al., 2005). In the same
research program, consumption of 250 mL per day of “lite”
cranberry juice cocktail for four weeks significantly (p <0.01)
raised HDL levels in obese male volunteers (Ruel et al., 2006).
Additionally, during consumption of a cranberry supplement
(spray-dried cranberry juice in gelatin capsules, 1200 mg/day)
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760 E. PAPPAS AND K. M. SCHAICH
advanced oxidation protein products (AOPP) in plasma de-
creased significantly (p <0.05) after four and eight weeks,
with greater than four-fold reductions relative to baseline and
placebos levels. Incredibly, the reduction in AOPP remained sig-
nificant (p <0.05, compared to baseline) in a follow-up analysis
240 days after supplementation was stopped (Valentova et al.,
2007). A measure of in vivo oxidative stress, AOPP is higher in
those with coronary artery disease and ischemic heart disease
than in healthy individuals (Witko-Sarsat et al., 1996; Kaneda
et al., 2002). This is the first and only report to date that con-
sumption of plant antioxidants (other than vitamin C) affects
this biomarker. (Valentova et al., 2007).
In direct contrast, regular consumption of cranberry juice of
750 mL/day for two weeks had no significant effect on several
cardiovascular disease risk factors (plasma AOC as measured
by FRAP, LDL content, and HDL content) in healthy females
(Duthie et al., 2006). Ruel et al. (2006) speculate that these
discrepancies may be due to the short duration of the interven-
tion and the populations studied. Also, markers of antioxidant
effects may have been missed because blood and urine were
collected after overnight fasting. Increased FRAP was reported
to be detectable only up to 250 minutes after cranberry juice
consumption (Pedersen et al., 2000).
Overall, then, most available data suggests that regular
consumption of cranberry products increases the antioxidant
capacity and decreases oxidation biomarkers in human plasma
and thus may contribute actively to maintaining cardiovascular
health. More detailed clinical evaluations should reveal whether
cranberry supplementation may become therapeutic as well as
preventative in high risk populations, e.g. hypercholesterolemic,
hypertensive, or obese patients.
It must be noted, however, that in none of the studies cited
were plasma levels of cranberry phenols measured, and as will
be discussed in Section titled Bioavailability and Metabolism of
Cranberry Phytochemicals, absorption of cranberry flavonoids
is extremely low. Thus, it seems most likely that cranberry con-
sumption mediates protection of the cardiovascular system indi-
rectly and at a distance rather than by direct molecular interven-
tion within the blood vessels. In particular, the anti-inflammatory
effects as well as signal transduction cascades that activate phys-
iological defenses may play critical roles in cardio-protection
by cranberries. These mechanisms will be discussed in further
detail in Sections titled Anti-Inflammation and the Effects on
Signal Transduction, Protein Expression and Activity.
Neurological Health
Until recently, the cause of age-related loss of neurological
function defied convincing explanation. Then, the inability of
aged brain tissue to counter oxidative insults was hypothesized
as the primary cause of this degeneration (Markesbery, 1997).
Applied to Alzheimer’s disease, this theory holds that oxidative
stress, largely facilitated by amyloid-βaccumulation and sub-
sequent free radical formation, initiates a cascade of events that
mediate Ca2++ efflux from neurons and lead to further oxidative
stress and eventually cell death. Clinical and epidemiological
observations have emerged to support this reasoning (Engelhart
et al., 2002; Petersen et al., 2005).
Dietary antioxidants may be effective in inhibiting this pro-
cess. Indeed, animals fed polyphenol-rich berries and grapes (or
extracts of these) showed improved neural function, marked by
inhibition and even reversal of age-related neural deficiencies as
measured behaviorally and physiologically (Joseph et al., 1999;
Bickford et al., 2000; Andres-Lacueva et al., 2005; Shukitt-Hale
et al., 2006a, 2006b), and this effect may extend to protection
from ischemic damage and radiation-induced neural damage
(Wang et al., 2005; Rabin et al., 2005). Perhaps most convinc-
ingly, a prospective study of 1836 subjects demonstrated that in-
creased consumption of fruit and vegetable juices was inversely
correlated with development of Alzheimer’s disease (Dai et al.,
2006). Subjects who consumed less than one serving per week
of fruit and vegetable juices were four times more likely to de-
velop Alzheimer’s disease than those consuming three or more
servings per week (p <0.01). Intake of vitamins E and C as
well as β-carotene failed to correlate with Alzheimer’s disease
development, so nonnutrient phytochemicals, polyphenols in
particular, were proposed to be the components responsible.
Although blueberries seem to be the prototype for this ef-
fect, neuroprotection also has been associated with cranberries.
In a model of Alzheimer’s disease in which COS-7 cells were
treated with dopamine or amyloid-β, pretreatment with a cran-
berry extract significantly reduced deficits of Ca2+homeosta-
sis compared to controls (Joseph et al., 2004). In addition, an
anthocyanin-rich cranberry extract inhibited oxidation of the
neurotransmitter 6-hydroxy-dopamine in an in vitro cellular
model of Parkinson’s disease (Yao and Vieira, 2007).
In an animal study of cranberry effects on Alzheimer’s dis-
ease, aged rats fed 2% (by weight) freeze-dried cranberries for
eight weeks showed greater strength and balance than controls
in tests of motor skills (p =0.0001). Brain tissue from the
group fed cranberries exhibited enhanced nerve signal trans-
mission (p =0.007) and better response (p =0.06) towards
oxidative stress ex vivo after 16 weeks supplementation. The
investigators concluded that cranberries enhanced neural func-
tion, neuro-protective responses, and some motor function in
these aged animals (Shukitt-Hale et al., 2005). In humans, on
the other hand, a double-blind, placebo-controlled pilot study
found no significant correlation between improved neuropsy-
chological function and cranberry juice cocktail supplementa-
tion (32 ounces, 950 mL per day) for six weeks in fifty elderly
participants, although a positive trend (p =0.12) was observed
in self-reported improved memory function (Crews et al., 2005).
The researchers suggest that a larger trial over a more extended
period may more effectively reveal the neuroprotective actions
of cranberries.
Although it has received relatively little attention, protec-
tion of neurological function seems to be a promising area of
research for cranberries and other foods high in antioxidants.
More extensive testing in elderly human populations, with more
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CRANBERRY PHYTOCHEMICALS 761
subjects and longer periods of supplementation, certainly seems
appropriate to verify or disprove this potential benefit of cran-
berry consumption.
Anticancer
Cancer, one of the most feared diseases and now the #1 killer
of those under 85 (Twombly, 2005), involves DNA mutation and
unchecked tumor growth as major mechanisms. Current radia-
tion and chemotherapy treatments are often ineffective against
tumors and cause damage to peripheral tissues, so finding alter-
native therapies as well as means of prevention is of paramount
importance. For the past thirty years, diet has been a major focus
in cancer prevention research, and isolated phytochemicals are
being evaluated as chemotherapeutic agents or aids to current
chemotherapies.
Although connections between diet and cancer, either pos-
itively or negatively, were initially treated as folklore fantasy,
there is now strong epidemiological evidence supporting reduc-
tion of cancer incidence and mortality by high dietary consump-
tion of fruits and vegetables (Ames and Gold, 1991; Block et al.,
1992; Ames et al., 1993; Ruxton et al., 2006; Linseisen et al.,
2007). Meta-analysis of case control studies revealed strong
inverse correlation between fruit consumption and esophageal,
stomach, colorectal, bladder, and lung cancer risk, but not breast
cancer (Riboli and Norat, 2003). Effects were most dramatic
with stomach cancer incidence and least with colorectal cancer
(respective odds ratios odds ratio 0.69 and 0.93 per 100 g fruit
consumed per day). Results of epidemiological studies relating
total flavonoid consumption to cancer rates have been mixed,
hampered by incomplete knowledge of the occurrence and dis-
tribution of these phytochemicals in foods and also in tissues
(Hollman and Katan, 1999; Erlund, 2004).
In vitro studies have revealed encouraging potential for cran-
berry products, extracts, and individual components to inhibit
cancer (see Neto et al., 2007b for a recent comprehensive
review). Quercetin seems to be particularly active in vitro,
suppressing proliferation in pancreatic, leukemia, colon, and
breast cancer cells by 50% at 15–60 µg/mL (Choi et al., 2001;
Lee et al., 2002; Neto, 2007a, 2007b). Cell growth was also
inhibited by 50% when exposed to ursolic acid derivatives
(42–117 µg/mL) in lung, cervical, breast, colon, prostate, and
leukemia cancer models (Murphy et al., 2003) and by cran-
berry proanthocyanidins (20–70 µg/mL) in lung, cervical, and
leukemia cancer cell lines (Neto et al., 2006). Proanthocyanidin-
rich extracts proved cytotoxic to ovarian cancer cells at con-
centrations as low as 79 mg/mL and significantly increased
the chemotherapeutic activity of paraplatin (Singh et al.,
2007).
Evidence for anti-cancer effects of cranberries in vivo is more
equivocal. Feeding studies of cranberry components, most no-
tably large quantities of quercetin and resveratrol, demonstrate
clear inhibition of induced cancers in rats and mice (Verma et al.,
1988; Baur and Sinclair, 2006). Resveratrol feeding (200 µg/kg
per day for 100 days) lowered the incidence of azoxymethane-
induced precancerous aberrant crypt foci in rats by 35% (p <
0.01) compared to controls (Tessitore et al., 2000). Cranberry
juice given as 20% solutions versus water controls, <20 mL/day,
reduced the incidence of azoxymethane-induced aberrant crypt
foci in rats by 77% (p >0.05) when supplemented for three
weeks before and ten weeks after the chemical insult (Boateng
et al., 2007).
In human clinical trials, aspirin (an acetylated derivative of
salicylic acid found in cranberries) at as low as 81 mg/day dose-
dependently decreased precancerous, colorectal adenomas in
patients with a confirmed history of adenoma incidence within
16 months prior to the study (Baron et al., 2003). Higher an-
tioxidant capacitates in the plasma of healthy male and female
volunteers consuming cranberry juice (Pedersen et al., 2000;
Ruel et al., 2005; Lu and Wang, 2006) is also suggestive of
increased anti-cancer potential. On the other hand, in healthy
females cranberry supplementation for six weeks failed to al-
ter biomarkers of cancer, such as plasma antioxidant capacity,
levels of basal lymphocyte DNA damage in vivo, and induced
lymphocyte DNA damage ex vivo (Duthie et al., 2006). How-
ever, blood samples were collected after overnight fasting. This
protocol would miss effects if cranberry compounds and dam-
aged DNA are cleared or metabolized in less than twelve hours.
Thus, it would be interesting to see if cancer biomarkers are
altered within short times after consumption and to determine
how long any protection lasts. It would also be useful to deter-
mine whether groups with higher cancer risk (such as cigarette
smokers) show greater response to cranberries.
The potential for anti-cancer action when cranberry com-
pounds contact cancer cells seems clear, although for this pro-
tection to be actuated in vivo, the active compounds must be
absorbed and distributed to tissues, a distinct problem for sev-
eral major cranberry components. However, the requirement
for absorption is eliminated in the gastrointestinal tract, which
may explain why cranberries seem to be particularly protective
against colon cancer.
Issues of uptake and bioavailability as well as possible mech-
anisms of action will be discussed further in Sections titled
Bioavailability and Metabolism of Cranberry Phytochemicals
and the Effects on Signal Transduction, Protein Expression, and
Activity.
Anti-Inflammation
Inflammation, the physiological response to real or perceived
harmful stimuli or infection, is critical to immune function, but
when out of control it produces chronic inflammatory condi-
tions such as arthritis, colitis, and periodontitis. In inflamma-
tion, immune cells are attracted to foreign bodies or abnor-
mal cells and attempt to remove them. Recruitment of immune
cells and regulation of inflammation is complex; the total re-
sponse involves cyclooxygenase enzymes (COX-1, COX-2) that
produce eicosanoids, nitric oxide, and histamine as well as
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762 E. PAPPAS AND K. M. SCHAICH
adhesion molecules (ICAM-1, VCAM-1), nuclear factors (NF-
κB), chemokines (IFN-γ,TNF-α, IL-1), and cytokines (IL-6,
IL-8). Faulty regulation, persistent infection, and autoimmunity
lead to chronic inflammation: immune cells release reactive ni-
tric oxide and potent enzymes that cause tissue damage and
promote apoptosis, leading to cell death.
Inflammation appears to play an important exacerbating role
in diseases such as cancer and atherosclerosis. For example,
chronic inflammation predisposes tissue to cancer development
(Hagemann et al., 2007). Chronic activation of the epithelium
resulting in a variety of inflammatory responses is pivotal in
recruiting immune cells to blood vessel walls in the develop-
ment of atherosclerosis (Ross, 1999). Considering this behavior,
some have proposed that plasma levels of adhesion molecules
are novel, dynamic biomarkers of endothelial dysfunction and
elevated levels of these are risk factors for atherosclerosis (Ruel
and Couillard, 2007).
Investigations of diet and phytochemical effects on inflam-
mation mediators reveal potent anti-inflammatory activity in
cranberries and its components in vitro (Kandil et al., 2002;
Youdim et al., 2002a; Bodet et al., 2006a, 2007a, 2007b). Antho-
cyanins and hydroxycinnamic acids isolated from cranberries
reduce inflammation responses in human microvascular en-
dothelial cells challenged with TNF-α, in particular limiting up-
regulation of cytokines and adhesion molecules (Youdim et al.,
2002a). Regular cranberry juice consumption for twelve weeks
in obese volunteers lowered levels of plasma adhesion molecules
(Ruel and Couillard, 2007). In inhibiting immune responses
from vascular endothelial cells, these results suggest cardio-
protective as well as anti-inflammatory benefits from cranberry
components (Youdim et al., 2002a; Ruel and Couillard,
2007). Cranberry NDM, in a dose-dependent manner, also
inhibited the inflammatory responses of human macrophages
induced by periodontal pathogen lipopolysaccharides (Bodet
et al., 2006a) (see also the Section titled Dental Health and
Gum Disease).
In vivo, several isolated cranberry phytochemicals, includ-
ing flavonols, salicylic acid, resveratrol, and triterpenoids inhibit
inflammation in animal models. Quercitrin, one of cranberry’s
more abundant flavonols, reduced an index based on physiolog-
ical observations (body weight, presence of blood in feces, and
stool consistency) and ex vivo cytokine production in a rat model
of colitis (Comalada et al., 2005). Also in rats, resveratrol inhib-
ited inflammatory COX activity both before and after induction
by N-nitrosodiethylamine (Khanduja et al., 2004). One patent
application claims that flavonols and purified cranberry phyto-
chemicals reduce inflammation in vivo. Mouse ear edema in-
duced by 12-O-tetradecanoylphorbol-13-acetate was reduced by
34.0% and 55.1% after topical application of 87.5 µg and 175 µg
of quercetin-3-O-(6-benzoyl)-β-galactoside isolated from pro-
cessed cranberry powder (Vorsa et al., 2007b).
Overall, the potential for dietary consumption of cranberry
products to modulate inflammation appears promising, although
more in vivo studies are needed for confirmation and for iden-
tification of necessary levels and active compounds. Possible
mechanisms involved in anti-inflammatory effects of cranber-
ries will be discussed further in the Section on Effects of Signal
Transduction, Protein Expression, and Activity.
BIOAVAILABILITY AND METABOLISM
OF CRANBERRY PHYTOCHEMICALS
Bioavailability is currently a hot topic in nutrition and food
research, and this increased interest is well-justified: for a given
component to affect an organ, it must reach that tissue in ac-
tive form at biologically relevant concentrations. The in vitro
studies commonly used to screen antioxidant activity of phy-
tochemicals present in foods and natural products may reveal
inherent reactivity. However, the results are useless for predict-
ing or explaining bioactivity if the compounds of interest are
poorly absorbed, metabolized into different products after con-
sumption, or otherwise never reach the target organs intact or at
relevant concentrations.
Relatively little is yet known concerning the absorption ef-
ficiency and bioavailability of cranberry phytochemicals after
consumption by humans or animals, although new data is be-
ginning to emerge. The most definitive information comes from
studies of isolated phytochemicals in animal models. Table 5
summarizes the bioavailability of some classes of polyphenols
(found in cranberry) as isolated compounds and from vari-
ous foods. These observations offer broad insights but may
be misleading if used to draw specific conclusions regarding
the dietary intake of cranberries. The food matrix and interac-
tions between food components strongly influence bioavailabil-
ity (Parada and Aguilera, 2007). For example, observations of
flavonol bioavailability vary wildly depending on many factors
including the source, the specific molecular species, the pres-
ence of fats, and the degree of processing of the food consumed
(Hollman and Katan, 1999; Aherne and O’Brien, 2002; Parada
and Aguilera, 2007). Known plasma metabolites of cranberries
(as well as intact phytochemicals shown to reach the blood-
stream) are listed in Table 6. The few compounds found in urine
after cranberry consumption are detailed in Table 7.
Anthocyanin bioavailability is generally poor compared to
other flavanoids (Manach et al., 2005), usually limited to less
than a percent of the amount ingested. However, about 5% of
ingested anthocyanins were recovered intact in the urine of vol-
unteers fed cranberry juice, mostly within 3–6 hours after inges-
tion (Ohnishi et al., 2006). Substantially higher than the 1%
urinary excretion of anthocyanins from wine and strawberries
(Manach et al., 2005) and the highest reported for anthocyanins
from any food source, this unusual absorption was attributed to
interactions of anthocyanins with other components present in
the juice, promoting increased absorption (Ohnishi et al., 2006).
Peonidins accounted for greater percentages of recovered antho-
cyanins than did cyanidins, which suggests partial metabolism
(O-methylation) of the cyanidin-glycosides (Ohnishi et al.,
2006). No nonanthocyanin metabolites were identified. In con-
trast, two recent studies suggest minimal or no urinary excretion
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CRANBERRY PHYTOCHEMICALS 763
Tab le 5 Bioavailability of phenolic classes (pure form or from various foods) found in cranberries
Phytochemical
Class
Peak Plasma
Conc.
Tmax
(h)
Tissues Where
Available
Primary Forms
Detected In Vivo
Urinary
ExcretionReferences
Anthocyanins 0.001–0.2 µM0.7–4 Brain intact, methylated 0.004—5.1% Milbury et al., 2002;
Andres-Lacueva et al.,
2005; Manach et al., 2005;
Ohnishi et al., 2006
Flavonols 0.05–7.6 µM 0.5–9.3 lungs, testes, liver,
kidney, heart
intact, glucuronided,
methylated, sulfated
0.07–7% Erlund, 2004; de Boer et al.,
2005; Manach et al.,2005,
Vorsa et al., 2007
Catechins 0.03–5.9 µM 0.4–4 liver, kidney intact, methylated 0.1–55% Manach et al., 2005; Tsang
et al., 2005
PAC dimers ND-41 nM 2 intact ND-1.0% Prior and Gu, 2005; Tsang
et al., 2005
PAC trimers and
polymers
ND ND ND phenolic acids, monomers
(metabolism in
intestine)
ND Prior and Gu, 2005; Tsang
et al., 2005; Valentova
et al., 2007
Phenolic Acids ND-40 µM 0.5–3 intact, methylated glycine
conjugated
27%–39.6% Scalbert and Williamson,
2000; Zhang and Zuo,
2004; Manach et al., 2005
Trans-Cinnamic
Acids
0.006–40 µM 0.5–3 intact, glucuronided,
methylated, sulfated
0.3–61.7% Bourne and Rice-Evans,
1998; Rechner et al,.
2001a; Rechner et al.,
2001b; Manach et al., 2005
Stilbenes
(resveratrol)
ND-32 µM 4 liver, kidney glucuronided, sulfated 2.3% Meng et al., 2004; Baur and
Sinclair, 2006
of anthocyanins after regular consumption of cranberry products
(Duthie et al., 2006; Valentova et al., 2007).
Differences in sample handling may contribute to discrepan-
cies in anthocyanin detection. Collection of urine directly into
an acidified solution (Ohnishi et al., 2006) prevents degradation
of anthocyanins, whose stability is highly pH-dependent. Given
evidence that cranberry anthocyanins are excreted quickly, urine
collection after overnight fasting (Duthie et al., 2006) is likely
to miss most or all of the compounds absorbed. Freeze-drying
urine prior to analysis (Valentova et al., 2007) may also lead
to degradation of anthocyanins, especially if samples are not
protected from light.
Anthocyanins are unique in that they are the only flavanoid
absorbed primarily in the stomach, mostly in glycosylated
forms (Mazza et al., 2002; Talavera et al., 2003). Antho-
cyanins also have been shown to pass the blood brain
barrier. Cyanidin-3-galactoside, cyanidin-3-arabinoside, and
peonidin-3-arabinoside known to be prevalent in cranberries
were identified in rat brains after consumption of blueberries
(Andres-Lacueva et al., 2005). The same anthocyanins should
Tab le 6 Cranberry phytochemicals and metabolites found in plasma after cranberry consumption
Dose of
Molecular Species Source Duration Compound Cmax Tmax (m) References
Benzoic AcidCJC, 200 mL single exp. 11 mg 36 45 Zhang and Zuo, 2004
Salicylic acidCJC, 200 mL single exp. 620 µg 7.1 45 Zhang and Zuo, 2004
Total SalicylatesCJC, 750 mL/day 2 weeks 5.28 mg/day 0.23∗∗ ND∗∗∗ Duthie et al., 2005
2,3-Dihydroxybenzoic acidCJC, 200 mL single exp. 482 µg 13 45 Zhang and Zuo, 2004
2,4-Dihydroxybenzoic acidCJC, 200 mL single exp. ND 5.5 270 Zhang and Zuo, 2004
p-Hydroxyphenylacetic acidCJC, 200 mL single exp. ND 8.2 45 Zhang and Zuo, 2004
Ferulic acidCJC, 200 mL single exp. 220 µg 1.6 270 Zhang and Zuo, 2004
Sinapic acidCJC, 200 mL single exp. 1.0 mg 6.7 270 Zhang and Zuo, 2004
Ascorbic Acid CJC, 500 mL single exp. 134 mg 0.2∗∗ 240 Pedersen et al., 2000
Ascorbic Acid CJC, 750 mL/day 2 weeks 675 mg/day 60∗∗ ND∗∗∗ Duthie et al., 2006
Total Phenolics CJC, 500 mL single exp. 450 mg 3527 60 Pedersen et al., 2000
Quercetin-3-galactoside Isolated compound single exp. NA NA 7.5 Vorsa et al., 2007a
Quercetin-3-glucoside Isolated compound single exp. NA NA 15 Vorsa et al., 2007a
Abbreviations: Cmax =Maximum plasma concentration; Tmax =Time to maximum concentration; exp. =exposure; m =minutes;
ND =not determined; NA =information not provided in reference; denotes samples hydroyzed prior to analysis; ∗∗denotes increase
from basal levels; ∗∗∗plasma collected after overnight fasting.
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764 E. PAPPAS AND K. M. SCHAICH
Tab le 7 Compounds found in urine after cranberry consumption
Dose of Amount Observed % of
Molecular Species Source Duration compound in Urine Dose References
Cyanidin-3-O-galactoside CJ (200 mL) Single Exp. 4.70 µg/24 h 3.7 Ohnishi et al., 2006
Cyanidin-3-O-glucoside CJ (200 mL) Single Exp. 3.6 µg 0.0492 µg/24 h 1.4 Ohnishi et al., 2006
Cyanidin-3-O-arabinoside CJ (200 mL) Single Exp. 104.6 µg3.64µg/24 h 3.6 Ohnishi et al., 2006
Peonidin-3-O-galactoside CJ (200 mL) Single Exp. 174.3 µg 19.1 µg/24 h 11.0 Ohnishi et al., 2006
Peonidin-3-O-glucoside CJ (200 mL) Single Exp. 9.9 µg1.11µg/24 h 11.3 Ohnishi et al., 2006
Peonidin-3-O-arabinoside CJ (200 mL) Single Exp. 230 µg4.50µg/24 h 2.0 Ohnishi et al., 2006
Total Anthocyanins DCJ (1200 mg/day) 8 wk. NA <0.7 mg/mmol creatinineNA Valentova et al., 2007
Quercetin-3-galactoside Isolated compound Single Exp. NA NA NA Vorsa et al., 2007a
Myricetin-3-galactoside Isolated compound Single Exp. NA NA NA Vorsa et al., 2007a
Quercetin glucuronide DCJ (1200 mg/day) 8 wk. NA 1 mg/mmol creatinineNA Valentova et al., 2007
Hippuric acid DCJ (1200 mg/day) 8 wk. NA 6 mg/mmol creatinineNA Valentova et al., 2007
Salicyluric acid and isomers DCJ (1200 mg/day) 8 wk. NA 3 mg/mmol creatinineNA Valentova et al., 2007
Dihydroxybenzoic acids and isomers DCJ (1200 mg/day) 8 wk. NA 0.5 mg/mmol creatinineNA Valentova et al., 2007
Salicyluric acid and isomers CJC (750 mL) 2 wk. NA 1.4µg/mg creatinineNA Duthie et al., 2005
Total Salicylates CJC (750 mL) 2 wk. 5.28 mg/day 0.21 µg/mg creatinineNA Duthie et al., 2005
Abbreviations used: CJ =cranberry juice; DCJ =dried cranberry juice; CJC =cranberry juice cocktail; Exp =exposure; wk =week; NA =not available.
All studies were in humans except for Vorsa et al. (2007a), which was in mice.
Results from urine analyses on final day of treatment; urinary concentrations expressed relative to creatinine to account for variation in urinary volume; reported
as difference between treatment and placebo levels. These could not be converted to absolute concentrations because urinary volumes were not available.
be available to the brain upon consumption of cranberries, albeit
in very small concentrations.
Further investigation is needed to confirm the report of high
anthocyanin availability and urinary excretion from cranberry
juice, and to identify anthocyanin metabolites and tissue distri-
butions, if any.
Proanthocyanidins exhibit poor bioavailability. Some specu-
late that metabolites of PACs may be absorbed and elicit health
effects in the urinary tract (Howell, 2007). Reports of PAC
bioavailability focus on grape seed, cocoa products, and puri-
fied isolates while cranberry PAC bioavailability data is mostly
lacking, perhaps because they are not absorbed. Some in vitro
investigations suggest that smaller PAC oligomers and polymers
are absorbed in small quantities through models of the intestinal
epithelium, but this uptake is limited mostly to cleaved monomer
units (Deprez et al., 2001; Spencer et al., 2001a, 2001b). Other
data suggests that gut microflora significantly degrade poly-
meric PACs to aromatic acids, which may be absorbed in more
significant quantities (Deprez et al., 2000). One such microbial
metabolite, p-hydroxyphenylacetic acid, was found in human
plasma 90 and 270 minutes after a single administration of
cranberry juice, while it was not present in the juice (Zhang and
Zuo, 2004). This metabolite, however, may also arise from gut
degradation of any of cranberries flavonoids.
In vivo data regarding the fate of PACs after absorption
present a mixed picture. Intact PACs are not absorbed at all
in most animal models (Donovan et al., 2002). Nearly 100% of
radioactivity was recovered in feces of chicken and sheep after
being fed PAC oligomers and polymers, showing virtually no
uptake or metabolism of any kind (Jimenez-Ramsey et al., 1994;
Terrill et al., 1994). One investigation found no PACs in human
urine after eight weeks of supplementation with dried cranberry
juice (Valentova et al., 2007). Trace amounts of PAC dimers and
trimers were found in urine of rats after consumption of large
quantities of PAC-rich grape seed extract (Koga et al., 1999;
Tsang et al., 2005). PACs from grapes, however, contain only
B-type linkages, so are not direct models of the A-type PACs
common in cranberries.
PACs are known to associate with diverse biological ele-
ments, including proteins and LDL cholesterol (Porter et al.,
2001). Along with their structural heterogeneity and the lack
of commercially available standards, this complexation compli-
cates their analysis in biological matrices and may contribute to
underreporting of PAC absorption. The tannic nature of PACs
suggests that, if absorbed, these phytochemicals would rapidly
interact with and denature proteins, which would impair physi-
ological function and potentially cause toxicity. This is a logical
reason for natural design that prevents PAC absorption. How-
ever, these phytochemicals remain available within the stomach,
colon, and other sections of the digestive tract, where they ex-
hibit potent antipathogenic, antioxidant, and other biological
activity, as will be discussed more in Section titled Molecular
Mechanisms Underlying Health Effects.
Flavan-3-ol bioavailability after cranberry consumption has
not been studied systematically. In one report, flavan-3-ol
monomers were not detected in the plasma of volunteers 45 or
90 minutes after ingestion of 1800 mL of cranberry juice cock-
tail (Zhang and Zuo, 2004). However, with such late sampling
times any absorbed monomers may well have been missed due
to rapid metabolism and elimination or distribution. Flavan-3-ol
monomers from other fruits are absorbed similarly to flavonols,
then metabolized to sulfate or glucuronic acid conjugates as
reviewed by Manach et al. (2005).
Generally, flavonols seem to be more bioavailable than other
cranberry flavonoids. Studies with purified flavonol isolates
in animal models generally show that 10% of consumed
flavonols are absorbed, and that absorption and metabolism are
highly dependent on flavonol structure, presence and type of
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CRANBERRY PHYTOCHEMICALS 765
glycosidic linkage, and the food matrix (Erlund, 2004; Manach
et al., 2005; Parada and Aguilera, 2007). Feeding large quan-
tities of quercetin to rats (0.1% and 1% diet by weight) and
pigs (500 mg/kg) resulted in greatly enhanced absorption, ex-
tensive metabolism, and distribution to a variety of tissues (de
Boer et al., 2005). With the 0.1% dose, quercetin was found in
plasma (7.70 µM), lungs (1.04 µmol/kg), testes (0.82 µmol/kg),
kidneys (0.93 µmol/kg), and heart (0.50 µmol/kg) with lesser
amounts in other tissues. While only unmetabolized quercetin
was detected in plasma, metabolites predominated in tissues.
Absorbed cranberry flavonols are excreted in bile and urine,
largely as glucuronidated metabolites (Valentova et al., 2007;
Vorsa et al., 2007a). Indeed, flavonols accumulate, intact and
as glucuronidated metabolites, in the urethra of mice (Vorsa
et al., 2007a). Cranberry flavanols, among the most abundant
and most bioavailable flavonoids in cranberry products, have
been surprisingly overlooked in attributions of health effects.
Smaller, simple phenolics appear to be among the most well
absorbed of cranberries nonnutrient phytochemicals. Indeed,
cranberry phenolic acids, relatively small and simple molecules,
have even greater bioavailability than flavanols. Total phenolics
increased significantly to 600 mg/L gallic acid equivalents
above basal levels in human plasma following the consumption
of 500 mL of cranberry juice (Pedersen et al., 2000), mostly
due to phenolic acids and hydroxycinnamic acids. µg/mL con-
centrations of benzoic acid, 2,3-dihydroxybenzoic acid, 2,4-
dihydroxybenzoic acid, o-hydroxybenzoic acid, ferulic acid,
and sinapic acid were detected in human plasma after cranberry
juice consumption (Zhang and Zuo, 2004). Phenolic acids iden-
tified in human urine in significantly higher concentrations than
controls after administration of dried cranberry juice include
hippuric acid, salicyluric acid and its isomers, and dihydroxy-
benzoic acid and its isomers (Valentova et al., 2007). Levels of
salicylates in the urine and plasma of volunteers tripled from
basal levels following two weeks of daily cranberry juice con-
sumption (Duthie et al., 2005). To not overread these reports,
however, it must be stressed that absorbed levels in all cases
were very low, as shown in Table 5.
Resveratrol, in the only available investigation of its bioavail-
ability from cranberry consumption, was not detected in the
plasma of volunteers 45 minutes after a single administration of
cranberry juice (Zhang and Zuo, 2004). Other investigations of
resveratrol metabolism, however, suggest it is mostly converted
to sulphonated and glucuronated derivates within 30 minutes
(Walle et al., 2004), so sampling after longer times is too late.
Studies monitoring metabolized forms of this bioactive polyphe-
nol within minutes after cranberry consumption may be more
sensitive, especially since quercetin has been shown to drasti-
cally slow its metabolism (Baur and Sinclair, 2006).
There is no question about the bioavailability of ascorbic acid
in cranberries. Indeed, markedly increased levels of plasma vi-
tamin C have been observed after the consumption of cranberry
products. A single administration of 500 mL of cranberry juice
cocktail significantly elevated plasma vitamin C to 20 µM
within 2 hours, and levels were maintained for 250 minutes
post consumption. After two weeks consumption of 750 mL
cranberry juice per day by healthy volunteers, vitamin C levels
remained significantly increased (30 µM) even after overnight
fasting (Duthie et al., 2006).
Given their in vitro bioactivities, the fates of ursolic acid and
other polyphenolics after cranberry consumption warrant addi-
tional research; likewise, continued research into the bioavail-
abilities of the flavonoid fractions of this fruit seems justified,
particularly to clarify their influence on UTIs, plasma antioxi-
dant capacity, inflammation, and cancer. The bioavailability of
other cranberry components is either irrelevant or unknown. Es-
sential vitamins and minerals found in cranberry products are
undoubtedly absorbed and their well-documented health effects
are beyond the scope of this paper. Sugars and nonphenolic or-
ganic acids, too, are well absorbed but do not exhibit important
health effects. Complex carbohydrate fibers in cranberries are,
in all likelihood, not absorbed.
MOLECULAR MECHANISMS UNDERLYING HEALTH
EFFECTS
As a complex mixture of phytochemicals, cranberry prod-
ucts induce their observed biological effects via a multitude of
molecular mechanisms, sometimes competing and sometimes
additive or synergistic. Mechanisms may be divided into the
following three categories:
Pathogen interactions
Antioxidant mechanisms
Effects on signal transduction, protein expression and activity.
Pathogen Interactions
Uncommon and perhaps unique among plant foods, cran-
berry exhibits clear inhibition of a variety of pathogens, both in
vitro and in vivo, with implications for E. coli in the blad-
der, H. pylori in the stomach, numerous oral bacteria, and
viruses. The components and mechanisms responsible for the
anti-pathogenic effects of cranberries remain controversial, but
recent observations provide some interesting insights.
Acidification of urine and increase in urinary volume were
early mechanisms proposed to explain how cranberries prevent
UTIs, but these have been disproven. Placebo controlled studies
preclude the latter mechanism and observations of no significant
change in urinary pH after consumption of cranberry products
dispel the former (Avorn et al., 1994; Walker et al., 1997; Di
Martino et al., 2006; Valentova et al., 2007).
Interference with bacterial adhesion is now believed to ac-
count for much of anti-pathogenic actions of cranberries (Sob-
ota, 1984; Howell, 2007). In vitro investigations suggest that
cranberry phytochemicals interact with bacterial cell surface
proteins, including those responsible for adhesion, biofilm for-
mation and acid tolerance (Zafriri et al., 1989; Ofek et al., 1991;
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766 E. PAPPAS AND K. M. SCHAICH
Howell et al., 1998; Foo et al., 2000a; Steinberg et al., 2005;
Duarte et al., 2006; Liu et al., 2006). These in vitro observa-
tions point to NDM, PACs, flavonols, and fructose as the active
components, as indeed they probably are in the mouth, stomach,
and the digestive tract. However, negligible absorption of NDM
and PACs, as well as placebo-controlled studies for fructose
precludes their activity in the urinary tract.
The interference of cranberries with bacterial adhesion has
been observed in a variety of cells and biological matrices,
including uroepithelial cells (Sobota, 1984), vaginal epithelial
cells (Gupta et al., 2007), gastric cells (Shmuely et al., 2004),
erythrocytes (Zafriri et al., 1989), buccal cells (Sharon and Ofek,
2002), gastric mucus (Burger et al., 2000) and tooth-like sur-
faces (Weiss et al., 2004), as well as in nonbiological matrices
such as silicone rubber (Habash et al., 1999), glass (Allison
et al., 2000), and borosilicate coated glass (Johnson-White et al.,
2006). Many bacteria are affected including a large number of
gram-negative oral bacteria (Weiss et al., 1998, 2002), S. mu-
tans (Duarte et al., 2006), P. gingivalis (Bodet et al., 2006b),
E. coli (Sobota, 1984), and H. pylori (Burger et al., 2000), but
not Campylobacter jejuni (Johnson-White et al., 2006), Lyste-
ria monocytogenes (Johnson-White et al., 2006), or diarrheal
isolates of E. coli (Ofek et al., 1991). That cranberries are ef-
fective in so many different systems with different structures
and molecular components yet act against a relatively limited
set of bacteria strongly argues that the anti-adherence activity of
cranberry stems from interaction with the microorganism rather
than interaction with the matrix.
Indeed, the anti-adherence effects of cranberries appear to be
lectin specific (Sharon and Ofek, 2002). But how do cranberry
phytochemicals block adherence? Six discrete mechanisms that
have been proposed merit discussion:
promotion of high urinary concentrations of the adherence-
inhibiting Tamm-Horsfall glycoprotein (Zafriri et al., 1989)
alteration of electrostatic properties (Habash et al., 2000)
change in shape of pathogenic bacteria (Ahuja et al., 1998)
action as receptor analogs (Zafriri et al., 1989; Howell, 2007)
reduction of bacterial lectin expression (Ahuja et al., 1998)
denaturation of bacterial lectins (Liu et al., 2006)
Endogenous Tamm-Horsfall glycoprotein, the most prevalent
protein in normal human urine, has been linked to innate defense
against urinary pathogens (Tamm and Horfall, 1950). This pro-
tein inhibits adherence of E. coli to kidney cells (Dulawa et al.,
1988; Kumar and Muchmore, 1990). Moreover, Tamm-Horsfall
protein knockout mice had UTIs longer in duration with a higher
degree of colonization after inoculation with type-1 E. coli than
control mice capable of expressing this protein (Bates et al.,
2004). Following this pattern, increased T-H protein could ex-
plain why, after cranberry consumption, urine inhibits adherence
of type-1 E. coli ex vivo. That cranberry phytochemicals may
promote Tamm-Horsfall glycoprotein expression is appealing
in its mechanistic simplicity, but unfortunately there is no direct
evidence yet to substantiate this action. In particular, increases
in Tamm-Horsfall protein in urine after cranberry consumption
have not been observed. Furthermore, in vitro investigations sug-
gest cranberry interaction with the pathogen rather than with the
host. Still, this mechanism has not been investigated systemati-
cally so further research is warranted before it is dismissed.
The alteration of zeta potential of uropathogenic bacteria has
been observed in only one study, but deserves consideration as a
mechanism of cranberry anti-pathogenic effects. Hydrophobic
interactions are thought to be critical forces in bacterial lectin
adhesion to host receptors (Magnusson, 1982). Charges on a
cell surface (the zeta potential) interfere with hydrophobic as-
sociations and add electrostatic interactions, and thus may be
an important factor counterbalancing the pathogenic bacteria’s
ability to bind to host receptors. For example, positive changes
to the zeta potential of several uropathogens, including E. coli,
observed after incubation in urine of volunteers who consumed
cranberry supplements for three days was assumed to prevent
pathogen binding by creating an electrostatic repulsion on cells
(Habash et al., 2000), although the components and mechanisms
responsible for this change were not identified. Zeta-potential
has never been linked directly to microbial adherence, but the
phenomenon merits further investigation and consideration in
detailed focused studies.
Mechanistic studies of the effects of cranberries on lectins
have documented considerable changes in the shape of uro-
pathogens, which logically may be expected to alter docking fit
at cell surfaces. In one study, E. coli were cultured in growth
media containing 0 or 25% cranberry juice, adjusted to pH 7.
Two strains of P-fimbriated E. coli were observed via electron
microscopy as ovoid when grown in the control agar medium
but as elongated rods when in grown in the presence of cran-
berry juice (Ahuja et al., 1998). It would be interesting to see
if such morphological changes are also observed when E. coli
are incubated in urine from subjects consuming cranberry juice.
How shape changes might affect adhesion is not yet known and
has not been evaluated (Howell, 2007), but it may be indicative
of stress to the bacteria. Morphologic alterations are not likely
the main mechanism underlying the anti-adherence activity of
cranberries, but may contribute to creation of an unfriendly en-
vironment that is not conducive to microbial “settling in.
Another possible mechanism is that phytochemicals act as
receptor analogs and bind preferentially to the lectins, effec-
tively competing with actual receptor cites (Zafriri et al., 1989;
Howell, 2007). This is the most likely mechanism for adher-
ence inhibition in vitro by fructose in cranberries (Zafriri et al.,
1989), although there is no evidence that fructose consumption
inhibits UTIs in vivo (Howell, 2007). In fact, other juices and
foods rich in fructose and/or B-type PACs, including apple juice,
grape juice, green tea, and dark chocolate, do not induce ex vivo
anti-adherence in urine after consumption (Howell et al., 2005).
Likewise, there is no evidence that cranberry NDM or proantho-
cyanidins act as surrogate receptors as they inhibit P-type E. coli
in vitro (Zafriri et al., 1989; Howell et al., 1998). Competitive
receptors, though, may be responsible for some of the observed
activity on H. pylori in the stomach or, as suggested by Zafriri
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CRANBERRY PHYTOCHEMICALS 767
et al. (1989), for activity against type-1 E. coli in the diges-
tive tract. Indeed, a major part of UTI inhibition by cranberries
may occur in the gut, the primary source of uropathogenic E.
coli causing these infections (Zafriri et al., 1989; Kontiokari
et al., 2003) rather than in the kidney or bladder reached by only
trace amounts of absorbed and conjugated metabolites. Bind-
ing strains of E. coli with uropathogenic potential and reducing
their ability to colonize in the gut may promote dominance of
nonvirulent strains (Howell, 2007), which further impairs the
ability of uropathogenic E. coli to grow and thrive. Overall,
decreased intestinal levels of pathogens materially contribute to
the lower incidence of UTIs and bacteriuria following cranberry
consumption.
Reduction of bacterial lectin expression by cranberry phy-
tochemicals or their metabolites as suggested by Ahuja et al.
(1999) is certainly possible. For one strain of P-fimbriated E.
coli (JR1), serial plating in a medium containing 25% cran-
berry juice progressively reduced the percentages of bacteria
with lectins visible by electron microscopy. Agglutination also
progressively diminished, suggesting depressed rates of lectin
expression and adhesion. In another strain (DS17), no fimbriae
were observed after plating in media containing cranberry juice,
while 40% of the bacteria grown in control media without
cranberries had fimbriae. From these results, it was proposed
that cranberry components reduce lectin expression via sev-
eral possible mechanisms, including fimbrial synthesis, fimbrial
attachment to the cell wall, or phase variation (Ahuja et al.,
1998). Observations that in vitro, high molecular weight con-
stituents of cranberry juice retarded formation of extracellular
glucosyl- and fructosyl- transferases, enzymes from Streptococ-
cus sobrinus that facilitate dental plaque formation and adhesion
of dental pathogens to teeth (Steinberg et al., 2004), supports
the first two of these mechanisms. The third mechanism, phase
variation, is a phenomenon observed in numerous pathogens
including uropathogenic E. coli, wherein the bacteria express
their various virulence factors such as lectins (or do not express
them) at different times according to the progression of the in-
fection and stress state (Rhen et al., 1983; Pere et al., 1987).
Some component of cranberry or its metabolites, may elicit a
stress response in E. coli, directly leading to reduced expression
of lectins in the urinary tract.
Increasing evidence suggests that pathogenic bacteria com-
municate via quorum sensing, with dramatic influence on ex-
pression of genes that control virulence factors, including those
responsible for adherence and biofilm formation (Fux et al.,
2005). Via quorum sensing, pathogenic bacteria coordinate
phase variation and infection based on stress levels and appro-
priate bacterial concentration, switching back and forth from
dormant to infectious modes (Fux et al., 2005). Cranberry com-
ponents or metabolites may interfere with quorum sensing com-
pounds or proteins responsible for their regulation, ultimately
leading to lowered fimbrial expression. This possibility seems
very appealing, though since knowledge of quorum sensing is
still rudimentary, the action of cranberries by this route has not
been investigated.
The most plausible mechanism is that tannic elements of
cranberry or tannic metabolites induce conformational changes
in fimbriae. Atomic force microscopy has verified that within
three hours exposure to cranberry juice in vitro causes signif-
icant shortening of the P-fimbriae of E. coli to approximately
1/3 of its original length, lowered its adhesion strength to the
silicone-nitride probe, and increased its polymer density (Liu
et al., 2006). While specific components responsible were not
identified, the investigators concluded that binding of cranberry
phytochemicals to the fimbriae followed by conformational al-
teration of the lectins was consistent with the observed changes.
In addition, decrease in length and increase in polymer den-
sity strongly suggest protein denaturation and condensing of
lectin tertiary structure, while decreased adhesion strength de-
notes loss of functionality. This strongly supports contentions
that conformational changes to lectins, either by covalent bind-
ing or noncovalent interaction, drive the anti-adherent effects of
cranberries, especially for those in the mouth, stomach, and the
digestive tract. Similar examination is needed after incubation
of E. coli in urine samples from subjects consuming cranberry
to determine whether this activity relates to UTIs, but it seems
possible and even probable.
If induced conformational change to lectins is the probable
mechanism underlying the anti-adherence activity of cranber-
ries, questions remain regarding responsible components. Tan-
nins characteristically bind and often denature proteins. For a
compound to be characterized as a tannin and have this func-
tionality, it must be polyphenolic, 500 to 3000>Daltons (Da)
in size, with 1–2 hydroxyl groups per 100 Da (Chung et al.,
1998). In effect, polyphenols must have enough alcohol groups
to interact with hydrophilic elements of proteins as well as suf-
ficient mass and length to interact over enough area of protein
to force conformational changes. Flavonoid monomers (300
Da), even when glycosylated (450 Da), seem to lack the mass
needed to exert tannic activity. Dimers (600 Da, 8 hydroxyl
groups) and higher oligomers and polymers of flavonoids (in-
cluding proanthocyanidins) do have appropriate mass and hy-
droxyl groups to mediate binding and induce protein denat-
uration. The isolated A-type dimers and trimers (as well as
cranberry NDM and crude cranberry PAC extracts) all inhibited
adherence of P-fimbriated E. coli (Zafriri et al., 1989; Howell
et al., 1998; Foo et al., 2000a; Foo et al., 2000b). However, the
B-type dimer did not have this activity in vitro nor did the urine
of those having consumed other foods rich in B-type PACs ex
vivo (Foo et al., 2000b; Howell et al., 2005). It has been specu-
lated that A-type PACs have a higher degree of structural rigidity
due to the extra linkage and this may play a role in the forma-
tion of unknown, bioactive urinary metabolites and/or increased
binding of lectins (Foo et al., 2000a; Howell et al., 2005).
Meeting the criteria to be defined as tannins, the polymeric
pigments in cranberries (or at least their proposed molecular
formula) may exhibit tannic activity as well and consequently
contribute to anti-adherence action. As previously mentioned,
though, none of these tannic cranberry phytochemicals have
been found in urine after cranberry consumption. Interestingly,
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768 E. PAPPAS AND K. M. SCHAICH
the relatively large accumulation of cranberry flavonols and their
metabolites found in the urethra of mice were recently proposed
to account for cranberry inhibition of UTI (Vorsa et al., 2007a).
Glucuronate metabolites of flavonol glycosides do have suffi-
cient molecular mass and enough alcohol groups to be catego-
rized as tannins (650 Da, 10 hydroxyl groups), so they may
be responsible for, or at least contribute to, cranberry anti- UTI
action. However, isolation of the metabolites and examination of
anti-adherence abilities at biologically relevant concentrations
would be needed to confirm this.
Recent research of antiviral properties of cranberry phy-
tochemcials points to cell surface interactions as another mecha-
nism of action. One investigation suggests that cranberry phyto-
chemicals may alter host cell surface proteins (namely junction
adhesion molecule A) used by viruses as receptor sites, causing
partial or total loss of infectivity (Lipson et al., 2007a). Un-
like the proposed mechanisms for bacterial anti-adherence, this
mechanism relies on phytochemical interaction with host cell
surfaces and thus may not be viable in vivo because the key
phytochemicals are poorly absorbed or not absorbed at all.
Antioxidant Activities and Mechanisms
Antioxidant mechanisms have attracted much research for
their roles in preventing and potential for treating diseases
that involve oxidative degradation of tissue. Decreased rates
of cancer and cardiovascular disease associated with fruit and
vegetable consumption have piqued attention of the general
public to such an extent that produce, herbs, spices, and for-
mulated foods are advertized for their ORAC values, the antiox-
idant power arising from their phytochemical components. Free
radicals and reactive oxygen species produced during routine
bioenergetic cellular processes, as well as electrophilic chem-
icals from other sources such as cigarette smoke, diet, and
environmental pollutants, cause damage to vital sub-cellular
components (Ames and Gold, 1991; Ames et al., 1993; Ames,
1998). Reactive chemical insults to DNA may result in muta-
tion, apoptosis, or cancer, while damage to proteins and other
structures leads to Alzheimer’s disease, Parkinson’s disease,
cataracts, and dozens more degenerative diseases (Ames and
Gold, 1991; Ames et al., 1993; Markesbery, 1997; Ames, 1998;
Engelhart et al., 2002; Youdim et al., 2002b). Oxidation of LDL
is an active process in the progression of atherosclerosis, and
oxidative damage to specialized cells and to tissues contributes
markedly to aging (Ames et al., 1993; Bickford et al., 2000).
Data presented throughout this review provide substantial
evidence that consumption of cranberries leads to increased
plasma antioxidant capacity and decreased biomarkers of ox-
idative stress. More unclear is whether phytochemicals directly
quench reactive oxygen species and free radicals in vivo or
whether they induce endogenous antioxidant responses through
some alternate mechanism(s). In the discussion that follows,
“direct” antioxidant mechanisms will be considered first, then
“indirect” antioxidant mechanisms.
Direct Antioxidant Activity
The in vitro antioxidant capacity of cranberry components
is among the highest reported for fruits commonly consumed
in the United States (Sun et al., 2002; Wu et al., 2004). As
measured by the total oxyradical scavenging assay (TOSC),
cranberries have nearly twice the radical scavenging activity of
the next most active fruit (Sun et al., 2002); this was attributed
entirely to the phenolic content of cranberries since no vitamin
C was detected (Sun et al., 2002). In a study of fourteen fruits,
cranberries also had the highest total antioxidant activity by
weight and second most by serving size (second to blueberry)
as measured by combined hydrophilic and lipophilic oxygen
radical absorbance capacity (ORAC) assays (Wu et al., 2004).
Significant correlation between ORAC and ACY contents in
various cranberry samples (r =0.869–0.929) suggests these
active pigments may also be the most powerful antioxidants
in cranberries. At the same time, as might be expected, there
was greater correlation between ORAC and total phenolics (r =
0.902–0.946) (Wang and Stretch, 2001). Indeed, abundant phe-
nolics make cranberries one of the most antioxidant rich foods
available.
These in vitro measures of antioxidant capacity are impres-
sive but do not reveal the full story because they do not account
for absorption, metabolism, distribution, and excretion of cran-
berry components in cells and tissues (Duthie et al., 2006). In-
deed, a major limitation of cell culture and other in vitro assays
is that they test direct exposures that may or may not occur in
vivo. Anthocyanins and PACs, in particular, show exceptional
antioxidant activity in vitro, but are poorly absorbed, as dis-
cussed earlier. Cranberry flavonoid concentrations detected in
plasma, internal tissues, or organs in vivo are only nanomo-
lar at the highest (Zhang and Zuo, 2004; Vorsa et al., 2007a).
Thus, it seems unlikely that cranberry flavonoids are absorbed
intact in concentrations necessary to act as direct antioxidants.
The exceptions, perhaps, are the excretory organs such as the
liver, kidneys, and bladder. The fast clearance observed for the
flavonols and anthocyanins that are absorbed from cranberry
consumption (Ohnishi et al., 2006; Vorsa et al., 2007a) may
concentrate these compounds in excretory tissues for short peri-
ods. This short-term concentration, together with absorption of
smaller phenols in cranberries, may cause a localized spike in re-
dox potential following cranberry consumption, recharging en-
dogenous antioxidants and halting damaging free radical chain
reactions. The bladder, in particular, seems to be most exposed to
flavonoid antioxidants as they accumulate there (Ohnishi et al.,
2006; Vorsa et al., 2007a).
Poor absorption of many antioxidant phytochemicals re-
quires a rethinking of how these compounds influence animal
systems after consumption. Lack of absorption does not equate
to lack of bioactivity or inability to act in vivo as an antioxidant
or by other mechanisms. Cranberry phytochemicals are certainly
available to the digestive tract where they may mediate a variety
of responses, especially in relation to cancers and inflammatory
diseases of the esophagus, stomach, and colon. Cancers of the
digestive and excretory organs (esophageal, stomach, colorectal,
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CRANBERRY PHYTOCHEMICALS 769
and bladder cancer) where cranberry phytochemicals have most
contact after dietary ingestion and thus greatest opportunity for
interaction are among the ones whose incidence is most in-
versely correlated with fruit intake (Riboli and Norat, 2003).
It is likely that direct antioxidant mechanisms play a large, if
not primary, role in the apparent prevention of these cancers by
fruits and cranberries.
Cranberry antioxidant effects extend far beyond cancer pre-
vention. Following cranberry consumption, the antioxidant po-
tential of its phytochemicals reaches the intestinal tract promot-
ing a shift to a reduced state. Modulating intestinal redox tone
and associated cell signaling may be one mechanism by which
cranberry antioxidants can influence physiological responses
without being absorbed. Antioxidant action in the gut to counter
oxidative stress there may spare endogenous antioxidants, re-
leasing them to protect more sensitive cells and tissues against
oxidative insult. Cranberry phytochemicals neutralize oxidative
species in the digestive tract and by binding to molecules or to
receptors on brush border epithelial may block absorption of
harmful, reactive compounds.
While parent flavonoids may be poorly absorbed, there still
may be an in vivo antioxidant role for phenolic degradation prod-
ucts from hydrolysis, microbial metabolism, or chemical degra-
dation of cranberry flavonoids and polymeric components. Add
to these also the numerous phenolic acids and hydroxycinnamic
acids naturally present in the fruit, all of which are absorbed to a
much greater extent than the antioxidant flavonoids that receive
most attention, and the result could be significant antioxidant
potential in vivo.Uptake, metabolism, and distribution of these
quantitatively minor compounds have not been followed pre-
viously, but now are beginning to receive research attention as
possible explanations for cranberry effects on cells and tissues,
particularly the increases in antioxidant capacity and decreased
biomarkers of oxidative damage observed following cranberry
consumption.
Outcomes of cranberry antioxidant effects in vivo include
reduced levels of oxidized LDL and AOPP that diminish car-
diovascular health (Ruel et al., 2005; Ruel and Couillard, 2007),
general reduction of oxidative stressors that lead to cell and tis-
sue degeneration (Valentova et al., 2007), and signal transduc-
tion that affects systemic responses far downstream, as will be
discussed in the Section titled Effects on Signal Transduction,
Protein Expression, and Activity.
Indirect Antioxidant Activity
Increasing skepticism over the ability of dietary phenols to
act as traditional antioxidants in vivo has emerged over the past
several years. Cranberries and other fruits and vegetables have
been shown to increase plasma antioxidant capacity (Pedersen
et al., 2000), yet the concentrations of circulating flavonoids and
polyphenols observed after their consumption remain very low
(10–20 µM at most) and account for only a small percentage (2–
4%) of total circulating antioxidants which include ascorbate,
urate, and simple phenolics (500 µM) (Stevenson and Hurst,
2007). Thus, cranberry flavonoids and polyphenols should have
inconsequentially small effects as direct antioxidants, except for
perhaps in the intestinal tract and digestive system. Alternative
“indirect” antioxidant mechanisms must be examined to explain
in vivo activity of cranberry polyphenols.
One indirect mechanism receiving considerable recent at-
tention is induction of endogenous defense enzymes (Dragsted
et al., 2004; Stevenson and Hurst, 2007). These include pro-
teins directly responsible for countering oxidative stress, in-
cluding superoxide dismutase, catalase, and glutathione perox-
idase, those responsible for creating endogenous antioxidants,
including γ-glutamylcysteine synthetase (GCS) and glutathione
synthetase and those responsible for the metabolism of poten-
tially reactive xenobiotics including glutathione S-transferases
and quinine reductase, governed by electrophile-responsive el-
ement (EpRE) mediated enzyme expression (Dragsted et al.,
2004; Stevenson and Hurst, 2007). This is an intriguing possible
mechanism that could explain greatly increased plasma antiox-
idant capacity with only trace levels of absorbed polyphenols.
Both quercetin and bilberry extracts at low µM concentra-
tions upregulated several EpRE containing genes in vitro, re-
sulting in increased enzyme expression, suggesting promotion
of phase II metabolic enzymes that counter electrophilic xenobi-
otics by generation of endogenous antioxidants and deactivation
of toxic reactive oxygen species (Myhrstad et al., 2006). For ex-
ample, GCS was significantly induced in COS-1 cells by low
µM concentrations of quercetin (3 fold) and kaempferol (2
fold), but not myrcetin; this activity explained observations that
quercetin (at 5 and 25 µM) significantly increased glutathione
concentrations by as much as 50% (Myhrstad et al., 2002). In
vivo, 27% and 45% cranberry juice supplementation for 120
days increased superoxide dismutase activity in the liver of or-
chidectomized rats (p <0.05) (Deyhim et al., 2007). Such induc-
tion of defensive enzymes and endogenous antioxidant systems
by flavonols has extensive ramifications for cancer prevention
and cardiovascular disease.
While few reports of cranberry induction of protective pro-
teins in vivo could be found, studies involving other fruits and
vegetables may shed light on other potential mechanisms of an-
tioxidant activity after cranberry consumption. In humans, six
days of high fruit and vegetable diets did not affect antioxi-
dant capacity measured by plasma FRAP and TEAC (which
mostly measure electron transfers rather than traditional radi-
cal quenching), but they did significantly increase LDL oxida-
tive lag time and induce glutathione peroxidase relative to con-
trol and vitamin/mineral-supplemented diets (Dragsted et al.,
2004), demonstrating that consumption of fruits and vegeta-
bles increases enzymatic antioxidant defense mechanisms via
nonnutrient mechanisms. Similar observations were made after
consumption of apple juice and black currant juice (Young et al.,
1999).
Although direct evidence is still limited, promotion of
antioxidant-related enzymes or a similar mechanism is at least
partially responsible for the strong inverse correlations between
fruit and vegetable intake and cancer and other degenerative
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770 E. PAPPAS AND K. M. SCHAICH
diseases. Also likely is that promotion of antioxidant activity
after consumption of cranberries is at least partially due to one
or several of these enzyme-related mechanisms.
Effects on Signal Transduction, Protein Expression,
and Activity
Recent evidence indicates that phytochemicals influence
gene expression, enzyme activity, and signal cascades, and these
actions may be responsible for much of the reported potential
anti-cancer, anti-inflammatory, and neuro-protective effects of
cranberries beyond the gastrointestinal tract in vivo. Although
the molecular mechanisms involved have not yet been eluci-
dated, it is likely that phenol covalent binding to proteins, e.g.
through thiol groups, and subsequent proteolysis to signal pep-
tides plays a critical role in these nutragenomic processes.
For example, cranberry phytochemicals may inhibit cancer
by interfering with key pathways involved in cell function, most
notably regulation of the cell cycle and growth via ornithine
decarboxylase (ODC) inhibition, induction of apoptosis by un-
known pathways, inhibition of invasion and metastasis via sup-
pression of matrix metalloproteinases (MMP), and reduction
of harmful inflammatory responses by modulating COX and
NFk-B pathways (Neto, 2007a, 2007b). In these actions, the
active cranberry components seem to be salicylic acid, ursolic
acid and its derivatives, flavonols, and PACs. Isolated resveratrol
also seems potently anticarcinogenic in vitro (Jang et al., 1997)
and in vivo (Tessitore et al., 2000).
ODC, a regulator of polyamines that direct cell growth and
proliferation, is often over-expressed in cancer cells (Kubota
et al., 1995, 1997; Neto, 2007b). This over-expression con-
tributes to cancer proliferation and invasion, especially in pro-
moting mitogen activated protein kinase activity that seems cru-
cial to cell proliferation and transformation (Kubota et al., 1995;
Kubota et al., 1997). Limiting ODC expression and activity,
then, is a potential means to control cancer development. An
early in vitro study revealed that crude cranberry extracts and
especially proanthocyanidin extracts were potent inhibitors of
ODC activity in cancer cells (Bomser et al., 1996). Cranberry ex-
tracts also inhibited ODC production in mouse epidermal cells;
the most active fraction containing primarily proanthocyanidins
and flavonol glycosides inhibited ODC activity by 50% at 5.67
µg/mL (Kandil et al., 2002). Expression of ODC was also sig-
nificantly reduced and ODC induction by lipopolysacharides
was totally obliterated by crude cranberry polyphenol extracts
(mg/mL levels) in a mouse fibroplast model (Matchett et al.,
2005). This mechanism is probably most important in the mouth,
stomach, and the digestive tract where absorption and bioavail-
ability are not limiting issues, but binding to proteins on the
intestinal mucosa surface may set off a signal cascade that alters
systemic enzymes.
Cell cycle arrest and promotion of apoptosis are potent targets
in halting the unchecked growth of cancerous tumors (Ramos,
2007). Various extracts of cranberry polyphenols promote apop-
tosis and cell cycle arrest in phases G1and G2at high (mg/mL)
concentrations in breast cancer models (Ferguson et al., 2004;
Sun and Hai Liu, 2006; Neto, 2007a, 2007b) and at low (µM)
quercetin concentrations in liver cancer cells (HepG2) (Ramos
et al., 2005), leading to the conclusion that in vitro anti-apoptotic
activity of cranberries was due to this flavonol (Neto, 2007a;
Neto, 2007b). In vivo, this mechanism may be active in the
mouth, stomach, bladder, and digestive tract after cranberry
consumption, but probably not otherwise, considering the rela-
tively high concentrations necessary and the low bioavailability
of flavonols.
Matrix metalloproteinases may facilitate alteration of the ex-
tracellular matrix, promoting invasion, proliferation, and metas-
tasis (Pupa et al., 2002). Cranberry PACs, as well as PACs
from other sources, inhibit MMP-2 and MMP-9 in cancer cells
(Vayalil et al., 2004; Neto et al., 2006; Neto, 2007b). One cran-
berry PAC subfraction (characterized as mostly DP 4 to 7 with at
least 1 A-type linkage) was particularly effective, inhibiting 90%
of MMP-2 and MMP-9 in prostate tumor cells at 500 µg/mL
in vitro (Neto et al., 2006). Ursolic acid and its cinnamic acid
derivatives at 9 µM concentrations similarly inhibited MMP-2
and MMP-9 (Cha et al., 1996; Kondo et al., 2004; Neto, 2007b).
In vivo,this mechanism may contribute to the inhibition of oral,
stomach, and gastrointestinal cancers observed for cranberries.
Isolated resveratrol inhibits cancer at various stages in in vitro
models, most notably by COX inhibition and induction of phase
II metabolizing enzymes (Jang et al., 1997). In vivo, resvera-
trol’s inhibition of precancerous lesions in colon cancer in rats
was traced to modified expression of p21 and bax proteins reg-
ulating apopotosis and cell proliferation (Tessitore et al., 2000).
However, the dosages (500 µg/kg) were very high, unlikely to
be achievable from normal consumption of cranberry products,
though perhaps possible by heavy supplementation.
Anti-inflammatory effects from cranberries may be related
to reduced COX activity, NF-κB down-regulation, and inhibited
adhesion molecule expression by diverse elements of the berry,
including flavonols, anthocyanins, proanthocyanidins, hydrox-
ycinnamic acids, resveratrol, and salicylic acid (Neto, 2007b;
Ruel and Couillard, 2007). COX-1 and COX-2 are enzymes
involved in the synthesis of pro-inflammatory prostaglandins
from arachidonic acid. Aspirin (acetylsalicylic acid), a COX-1
inhibitor widely prescribed to control inflammation, irreversibly
binds to the active site of COX-1 (Duthie et al., 2005). Trace
levels (nM) of its parent, salicylic acid, inhibit COX-2 activity
in vitro (Wu et al., 1991). After consumption of cranberry juice,
plasma concentration of salicylic acid increase to levels high
enough (high nM to low µM) to achieve this inhibition in vivo
(Zhang and Zuo, 2004; Duthie et al., 2005).
COX-1 and COX-2 are also inhibited by cranberry antho-
cyanins, though only mildly (10% reductions at 125 µg/mL)
(Seeram et al., 2001). Crude cranberry polyphenol extracts and
especially PAC-rich extracts show more pronounced effects,
with 50% reductions of COX-1 activity at 170 µg/mL and
20 µg/mL, respectively (Neto, 2007b). Collectively, these data
support COX inhibition and subsequent anti-inflammatory
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CRANBERRY PHYTOCHEMICALS 771
action in the mouth and digestive tract following cranberry con-
sumption due to polyphenols, and maybe more systemically due
to salicylic acid. Whether cranberry phytochemicals influence
COX expression in vivo is not yet known, but current research
is investigating this possibility (Neto, 2007b).
The transcription factor, NF-κB, is a potent regulator of
inflammation responses, affecting a wide variety of genes
that code pro-inflammatory adhesion molecules, cytokines and
chemokines (Ruel and Couillard, 2007). Quercetin at 50 µM and
100 µM (but not 5 µM) dose-dependently decreased NF-κB ac-
tivation in rat hepatocytes induced by interleukin-1b (Martinez-
Florez et al., 2005). In a rat model of colitis, anti-inflammatory
effects of quercitrin were traced to attenuation of NF-κB and
downstream effects on cytokines and inducible nitric oxide syn-
thase (Comalada et al., 2005). Abation of inflammation thus pro-
vides yet another mechanism by which cranberries effectively
influence pathologies in the mouth and digestive tract. Perhaps,
after continual consumption of cranberry, the accumulation of
cranberry flavonols in the urinary tract and bladder noted by
Vorsa et al. (2007a) may also play some role in cranberries’
prevention of urinary tract infections through anti-inflammation
mediated by NF-κB.
Adhesion molecules are stimulated by cytokines and reg-
ulated by NF-κB. These play crucial roles in inflammation
responses and atherosclerosis, linking leukocytes to endothe-
lial cells and facilitating their absorption into inflamed tis-
sues (Couffinhal et al., 1994). Numerous compounds found
in cranberries, including proanthocyanidins, anthocyanidins,
hydroxycinnamic acids, and salicylic acid, inhibit expression
of adhesion molecules in vitro. A review by Ruel and Couillard
(2007) reports previously unpublished observations of signifi-
cantly lowered plasma levels of ICAM-1 and VCAM-1 in vivo
as well, after 12 weeks of low calorie cranberry juice supple-
mentation in obese men, providing yet another explanation for
cardioprotective and anti-inflammatory effects from cranberry
consumption.
Oxidized LDL (LDLox) have received considerable attention
for their role in atherosclerosis. LDLox (Ruel et al., 2005) and
AOPP (Valentova et al., 2007) are not only biomarkers of ox-
idative stress, but also play critical roles as signaling molecules
that excite inflammatory responses in vivo. LDLox induces pro-
inflammatory reactions from epithelial cells, mainly via NFκB
activation (Robbesyn et al., 2004). AOPP promotes formation
of pro-inflammatory cytokines, which in turn, activate immune
cells (Kalousova et al., 2005; Valentova et al., 2007). As ex-
plained in Section titled Antioxidant Activities and Mecha-
nisms, whatever cranberry phenols are absorbed inhibit LDL
oxidation, probably by free radical scavenging. Thus, while the
action of cranberry compounds may be indirect, the effect—
lower circulating levels of LDLox and AOPP—directly and
materially contributes to control of inflammation and, in turn,
perhaps atherosclerosis (Ruel and Couillard, 2007; Valentova
et al., 2007).
Finally, neurodegradation in animals may be influenced via
protein expression and activity in addition to the protective
antioxidant mechanisms usually attributed to cranberries (Lau
et al., 2005). In a model of Alzheimer’s disease, feeding blue-
berries to aged mice raised concentrations of extracellular signal
regulated kinase (ERK) and protein kinase C (PKC), enzymes
critical to cognitive functioning and neural signaling; controls
without blueberries were unaffected (Micheau, 1999; Selcher
et al., 1999). Levels of these proteins were later correlated with
performance in motor tests of both young and aged rats (Lau
et al., 2005 and references therein). It seems likely that compa-
rable enzyme induction accounts also for the improved ex vivo
neural signaling observed in aged, cranberry-fed rats (Shukitt-
Hale et al., 2005). More research is needed to identify the active
components of berries and the mechanisms by which the en-
zymes are induced.
EFFECTS OF PROCESSING, STORAGE, AND
COMPOSITION ON CRANBERRY PHYTOCHEMICAL
STABILITY
Because the characteristic high acidity and tart flavor of fresh
cranberries are considered unpalatable by most consumers, cran-
berries are customarily processed into cranberry juice (65%)
and cranberry sauce (30%), both of which are generally sweet-
ened with sugars, other juices, or artificial sweeteners. Sweet-
ened dried cranberries, the [often flavored] products of coun-
tercurrent cranberry juice extraction, are increasingly gaining
popularity as well, though phytonutrient retention in this prod-
uct has not been determined. Only about 5% of cranberries are
sold in their fresh form, and the majority of these are probably
not eaten raw, but rather used in prepared foods such as cran-
berry sauce or in baked goods. Whole cranberries have been
noted for their excellent stability as compared to other fruits,
and remain unspoiled for several weeks at room temperature
if kept dry. In contrast, cranberry juice generally has a short
shelf-life relative to other fruit juices, due to rapid deteriora-
tion of color quality, which is its most attractive and important
quality factor (Francis, 1995). Loss of color, however, implies
corresponding destruction of the responsible anthocyanins and
for this reason, most research on processing and storage ef-
fects have focused on anthocyanins. Given the recent focus on
health promotion through diet, understanding processing effects
is critical not only for traditional goals of maintaining quality
and prolonging the shelf life of cranberry products, but increas-
ingly for conserving active phytochemicals that promote health
effects as well.
Storage and Processing Factors Affecting Phytochemical
Retention
Few published studies have examined the effects of stor-
age on the composition of whole cranberries, and those have
focused on anthocyanins. Because the color of the fruit does
not accurately predict the color of the juice it produces, color
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772 E. PAPPAS AND K. M. SCHAICH