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Catechin Content of 18 Teas and a Green Tea Extract Supplement Correlates With the Antioxidant Capacity

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Our literature review of currently available data in the area of tea and cancer prevention demonstrated that there is more conclusive evidence for the chemopreventive effect of green tea compared with black tea. We suggest that this is due to a large variation of the flavanol content in tea, which is not taken into consideration in most of the epidemiological studies. It was the purpose of this study to determine the flavanol content of various teas and tea products and to correlate it with their radical scavenging activity. A modified oxygen radical absorbance capacity (ORAC) assay at pH 5.5 was utilized. The total flavavol content varied from 21.2 to 103.2 mg/g for regular teas and from 4.6 to 39.0 mg/g for decaffeinated teas. The ORAC value varied from 728 to 1686 trolox equivalents/g tea for regular teas and from 507 to 845 trolox equivalents/g for decaffeinated teas. There was a significant correlation of flavanol content to ORAC value (r = 0.79, P = 0.0001) for the teas and green tea extract. The large variation in flavanol content and ORAC value among various brands and types of tea provides critical information for investigators using tea in studies of nutrition and cancer prevention.
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Catechin Content of 18 Teas and a Green Tea Extract Supplement
Correlates With the Antioxidant Capacity
Susanne M. Henning, Claudia Fajardo-Lira, Hyun W. Lee, Arthur A. Youssefian,
Vay L. W. Go, and David Heber
Abstract: Our literature review of currently available data in
the area of tea and cancer prevention demonstrated that
there is more conclusive evidence for the chemopreventive ef
-
fect of green tea compared with black tea. We suggest that
this is due to a large variation of the flavanol content in tea,
which is not taken into consideration in most of the epidemio
-
logical studies. It was the purpose of this study to determine
the flavanol content of various teas and tea products and to
correlate it with their radical scavenging activity. A modified
oxygen radical absorbance capacity (ORAC) assay at pH 5.5
was utilized. The total flavavol content varied from 21.2 to
103.2 mg/g for regular teas and from 4.6 to 39.0 mg/g for de-
caffeinated teas. The ORAC value varied from 728 to 1686
trolox equivalents/g tea for regular teas and from 507 to 845
trolox equivalents/g for decaffeinated teas. There was a sig-
nificant correlation of flavanol content to ORAC value (r =
0.79, P = 0.0001) for the teas and green tea extract. The large
variation in flavanol content and ORAC value among vari-
ous brands and types of tea provides critical information for
investigators using tea in studies of nutrition and cancer pre
-
vention.
Introduction
Tea is one of the most popular beverages in the world and
is consumed by over two-thirds of the world’s population.
Tea (Camellia sinensis) is manufactured as black (78%),
green (20%), or oolong tea (2%). The consumption of tea has
been associated with anticarcinogenic, antimutagenic, and
cardioprotective effects based on experimental studies using
cell culture and animal models. Epidemiological studies,
however, are not as conclusive (Table 1). The consumption of
tea has been associated with a decreased risk of developing
cancer of the stomach, colorectum, esophagus, lung, and
prostate as well as a decreased risk of atrophic gastritis, coro
-
nary heart disease, and incidence of stroke in some studies
(1). Other studies, however, do not support the protective ef
-
fect of tea against cancer (Table 1). Based on a summary in
-
cluding epidemiological studies with more than 200 cases
(Table 1) we concluded that there is stronger evidence for the
chemopreventive potential of green tea in Asian countries,
whereas studies of the chemopreventive effect of black tea in
smaller quantities are less convincing (Table 1).
The biological benefits of tea are due to their flavanol con
-
tent. Tea flavanols are a group of natural polyphenols found
in green and black tea. Four flavanol derivatives are found in
tea: (–)-epicatechin (EC), (–)-epigallocatechin (EGC), EC
gallate (ECG), and EGC gallate (EGCG) (Fig. 1). Their bio-
logical benefits are due to their strong antioxidant and
anti-angiogenic activity as well as their potential to inhibit
cell proliferation and modulate carcinogen metabolism (1).
Flavanols account for 6–16% of the dry green tea leaves
(2). During the manufacturing process of black and oolong
teas, tea leaves are crushed to allow polyphenol oxidase to
catalyze the oxidation and polymerization of flavanols to
polymers called theaflavins (2–6%) and thearubigins (20%)
(3). These polymers contribute to the characteristic bright or-
ange-red color of black tea. Three to 10% of the flavanols re
-
main in black tea. The major fraction of black tea
polyphenols is composed of high molecular weight com
-
pounds called thearubigins, which have been poorly charac
-
terized thus far (4).
Tea is usually prepared by infusing green or black tea
leaves in hot water. A typical cup of tea in Western society is
prepared by brewing one tea bag (1.8–2.4 g tea) in 200–250
ml of hot water for 3–5 min. Decaffeinated green tea extract
dietary supplements are also available to provide the con
-
sumer with a convenient way to benefit from the health bene
-
fits of tea flavanols without ingesting caffeine.
Chen et al. demonstrated that the flavanols in tea drinks are
stable in aqueous solutions with low pH (5). Even after a 7-h
brew at 98°C, only 20% of the green tea flavanols degraded.
Previous measurements of the antioxidant capacity of foods
and beverages have beenperformed using the classical oxygen
radical absorbance capacity (ORAC) assay with a phosphate
buffer pH 7 (6). Because most flavanols are unstable at pH 7,
the results from the classical ORAC assay may haveunderesti
-
NUTRITION AND CANCER, 45(2), 226–235
Copyright © 2003, Lawrence Erlbaum Associates, Inc.
S. M. Henning, C. Fajardo-Lira, H. W. Lee, A. A. Youssefian, V. L. W. Go, and D. Heber are affiliated with the UCLA Center for Human Nutrition, 900 Veteran
Ave., Los Angeles, CA 90095.
Vol. 45, No. 2 227
Table 1. Tea consumption and Cancer
Ref. Intervention/Location of Study Cancer Site/Outcome No. of Cases/Controls
Beneficial effects of tea consumption against cancer
7 10 cups green tea, Japan Delay in onset in all sites RR = 0.57 384/8,552
8 Green tea in female, nonsmoker, China Lung cancer RR = 0.65 649/675
9 >2 cups of black tea, male nonsmoker, Uruguay Lung cancer RR = 0.34 427/428
10 10 cups of Okinawa tea, Japan Lung cancer RR = 0.38 333/666
11 Green tea consumption, China Stomach cancer RR = 0.53 and chronic gastritis RR =
0.49
299/433
12 >7 cups of green tea, Japan Stomach cancer RR = 0.69 1706/21,128
13 300 g/mo of tea, China Colon, rectum, and pancreas, RR = 0.82, 0.72, 0.63 931,884,451/1,552
14 >2 cups of tea/day, postmenopausal women, Iowa Digestive and urinary tract, RR = 0.68, 0.4 2,936/35,369
15 Green tea, China Stomach cancer, RR = 0.71 711/711
16 Green tea, Shanghai, China Esophageal cancer, RR = 0.43 734/1,552
17 >5 cups, Japan Recurrence of breast cancer stage I and II, R = 0.56 472/8,552
18 >10 cups of green tea Chronic atrophic gastritis, R = 0.64 636/—
19 Green tea, China Gastric cancer 272/544
20 >1 cup hot tea, Arizona Squamous cell carcinoma RR = 0.63 234/216
21 3–4 cups tea, The Netherlands Bladder cancer RR = 0.8 569/3,123
22 Green tea, China Stomach cancer RR = 0.77 1,124/1451
No association of tea consumption with cancer
23 >5 cups of green tea, Japan Gastric cancer, R = 1.1 419/26,311
24 >5 cups of black tea, The Netherlands Breast, colorectal, stomach, and lung cancer 2,264/121,043
25 2–3 cups of black tea, Sweden Breast cancer, R = 1.1 1,271/59,036
26 >5 cups of green tea, Japan Cancer of all sites 4,069/38,540
27 Meta-analysis, 37 studies Urinary tract cancer
28 >4 cups of tea, Canada Prostate cancer 1,623/1,623
29 >2 cups of tea, postmenopausal women, Iowa Cancer of the colon and rectum 685/2,434
30 Tea, Italy Cancer of the oral cavity, esophagus, stomach, bladder,
kidney, and prostate
6,277/6,147
31 >2.6 cups tea, Iowa Bladder and kidney cancer 1,452,406/2,434
32 Black tea, Sweden Colon cancer 460/61,463
33 Tea, Canada Bladder, colon, and rectal cancer 927,991,825/2118
34 >4 cups of tea, Italy Ovarian cancer 1,031/2,411
35 >1 cup of tea, Italy Cancer of the colon and rectum 3,530/7,057
14 >2 cups of tea, postmenopausal women, Iowa Melanoma, non-Hodgkins lymphoma, cancer of the
pancreas, lung, breast, uterine corps, and ovaries
6,277/35,369
Figure 1. Chemical structures of EC, ECG EGC, EGCG, theaflavin, theaflavin-3-monogallate, theaflavin-3-monogallate, and theaflavin-3,3-digallate.
matedthe antioxidant capacityof the flavanols.The purposeof
this study was to measure the flavanol and theaflavin content
of various green tea, black tea, iced tea beverages, and one
green tea extract supplement. In addition, the ORAC values of
these teas and tea products were measured using a modified
ORAC assay at pH 5.5 and correlated to the flavanol and
theaflavin content of the teas and green tea supplement.
Results of this study provide important data for epidemio
-
logical studies by demonstrating the importance of collecting
more detailed information about the type of tea (decaffein
-
ated or regular, black or green). The results also will assist
consumers to choose the tea product that provides the most
health benefits.
Materials and Methods
Chemicals
β-Phycoerythrin (β-PE) from porphyridium cruentum,
gallic acid, (–)-catechin, (–)-catechin gallate, EC, EGC,
ECG, (–)-gallocatechin gallate, EGCG, caffeine, and a
theaflavin mixture called black tea extract containing four
theaflavins were purchased from Sigma (St. Louis, MO).
2,2-Azobis(2-amidinopropane) dihydrochloride (AAPH)
was purchased from Wako Chemicals, Inc. (Richmond,
VA). 6-Hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic
acid (Trolox) was obtained from Aldrich (Milwaukee, WI).
HPLC solvents were purchased from Fisher Scientific
(Pittsburgh, PA).
Teas
Eighteen different green and black tea bags and two brands
of iced tea were purchased in local supermarkets. Pharmanex
generously provided the green tea extract supplement.
Sample Preparation
Tea leaves from each tea bag (1.5–2.4 g) were removed,
weighed, and used for tea brewing in 100 ml boiling
deionized water for 3 min. Tea brews were filtered through a
coffee filter to remove tea leaves. The catechin content of the
filtered tea brews was analyzed by high-performance liquid
chromatography (HPLC), and aliquots were frozen at –20°C
for ORAC analysis. Tea brews prepared to test the difference
in flavanol content among different lots of Uncle Lee’s Green
Tea, Lipton Green Tea, and Bigelow Darjeeling Blend were
brewed for 5 min. The flavanol content of Tegreen capsules
was analyzed by dissolving one capsule in 100 ml of boiling
water. Aliquots were frozen at –20°C and analyzed by
HPLC. All determinations were performed in duplicates.
pH Stability Test
Flavanol stock solutions (6 mM) were prepared in metha
-
nol and stored at –70ºC. Twenty- to 60-fold dilutions were
prepared in phosphate buffers (0.5 M), pH 3–7, at room tem
-
perature. Samples were placed into the autosampler
immediately, and their flavanol concentrations were deter
-
mined using HPLC analysis.
ORAC Assay
The ORAC assay was performed as described by Cao and
Prior (6) except that a sodium acetate buffer (75 mM, pH 5.5)
was used to prevent degradation of the flavanols. In the final
mixture of 0.2 ml, β-PE (3.39 mg/l) was used as a target of
free radical attack and AAPH (8 mM) was used as a peroxyl
radical generator at 37°C. Trolox (10 µM) was used as a stan
-
dard control. The decrease of PE fluorescence was deter
-
mined by reading the fluorescence (excitation 535 nm, emis
-
sion 595 nm) every 2 min for 70 min in a Perkin Elmer HTS
BioAssay Reader (Norwalk, CT). The ORAC value was eval
-
uated as an area under curve (AUC) and calculated by taking
into account the Trolox reading using the following equation:
(AUC
sample
–AUC
buffer
)/(AUC
Trolox
–AUC
buffer
) × dilution
factor of sample × initial Trolox concentration (µM). Brewed
tea was diluted 1:250 with sodium acetate buffer (75 mM, pH
5.5) and flavanol and other flavonoid standard solutions were
prepared in methanol (3 mM) and diluted 1:150 to 1:600 in
the same buffer. Tea samples were analyzed in triplicate and
flavanol standards were measured in six replicates.
HPLC Tea Flavanol Analysis
After mixing the brewed tea with mobile phase 1:1 v/v
and filtering the mix through a 0.2-µm PVDF acrodisc sy-
ringe filter (Gelman, Ann Arbor, MI), tea flavanols were ana-
lyzed by HPLC. Filter discs were washed with 200 µl metha-
nol and the wash solution was also analyzed for flavanols by
HPLC. The flavanol content eluted from the filter disc was
added to the data from the tea analyses. The flavanol analysis
was performed by HPLC with a Waters NovaPak C18 (150 ×
3.9 mm, 4 µm) HPLC column and an Alltech Macrosphere
RP 300 C18 5U guard column. Mobile phase A was com
-
posed of acetonitrile and mobile phase B was composed of
960 ml 0.1% acetic acid (pH 3.5) + 20 ml acetonitrile + 20 ml
tetrahydrofuran. Flavanols were eluted with the following
gradient: at time 0 min, 100% B; at time 45 min, 40% B; and
at time 47 min, 100% B. The equilibration period was 8 min.
An Agilent Technologies (San Diego, CA) 1050 HPLC sys
-
tem was used with a Shimadzu (Cole Scientific Inc.,
Moorpark, CA) SPD-6AV, UV-VIS spectrophotometer (260
nm). Peak areas were integrated using the Agilent Technol
-
ogies 2D ChemStation Rev. A.0701. Final concentrations
were calculated in comparison with a known standard re
-
sponse.
Statistical Analysis
For each tea analysis, two samples were analyzed and the
mean values obtained. ORAC values were determined in six
replicates and mean values obtained. The Pearson correlation
228 Nutrition and Cancer 2003
coefficient for the tea flavanol content and ORAC values was
analyzed with the SAS program.
Results
Tea Flavanol Content
The four most common flavanols in green and black tea
are EGCG, EGC, EC, and ECG (Figs. 1 and 2). The flavanol,
gallic acid, and caffeine content of the teas, tea beverages,
and green tea extract supplement are shown in Table 2. The
green tea flavanol content ranged from 59.3 to 103.2 mg/g tea
in regular teas and from 26.7 to 52.2 mg/g in decaffeinated
teas. The flavanol content of regular black tea varied from
21.2 to 68.3 mg/g tea and from 4.6 to 5.4 mg/g decaffeinated
tea (Table 2). The tea content per tea bag ranged from 1.6 to
2.4 g of tea per tea bag. Black tea contained less flavanols
than green tea due to the fermentation process that generates
the epicatechin polymers known as theaflavins and
thearubigins and their gallate derivatives (Fig. 1). The
theaflavin content of regular black tea varied from 3.5 to 8.3
mg/g tea for regular teas and from 0.9 to 1.2 mg/g decaffein
-
ated black tea. In general, decaffeinated teas contained less
flavanols and theaflavins compared with regular teas. The
flavanol content of the green tea extract supplement was
equivalent to the flavanol content of one cup of the green tea
with the highest flavanol content. Iced tea beverages did not
contain any flavanols (Table 2a). Variations of flavanol con-
tent in tea bags from different lots purchased at different
times and different stores (Table 3) were smaller compared
with differences in teas from different brands (Table 2a,b).
Flavanol pH Stability
The stability of flavanols in different conditions such as
pH and temperature is an important factor to consider in the
determination of their biological activity. As shown in Figs. 3
and 4, the pH stability varies among different flavanols. At
pH 7, catechin, epicatechin, and ECG are still relatively sta
-
ble, whereas EGC, EGCG, and GCG are completely de
-
graded (Fig. 3). After 2 h at pH 7 only 34% of EGC and 61%
of EGCG remained (Fig. 4). After 7 h at pH 7 EGC and
EGCG were completely degraded. This shows the impor
-
tance of performing the measurements of the antioxidant ca
-
pacity at a lower pH where all the flavanols are stable.
ORAC Values of Individual Flavanols and
Flavonoids
The intra-assay coefficient of variation (CV) in the ORAC
assay was 0.9–3.7% for buffer and 1.3–3.2% for the Trolox
standard. The interassay CV was 8.0% for buffer and 5.4%
for the Trolox standard. The ORAC values of the individual
flavanol standard solutions as determined with the modified
ORAC assay are shown in Table 4. If expressed in Trolox
equivalents/µmol flavanol the following order of antioxidant
capacity was observed: ECG > EGCG > EC = catechin >
EGC > mixed theaflavins > gallic acid. To validate the modi
-
fied ORAC assay, the ORAC values of ascorbic acid and
other flavonoids such as quercetin, kaempherol, and
naringenin were determined (1.2, 6.7, 2.6, and 2.4 µmol
TE/µmol). The ORAC values of these antioxidants were con
-
sistent with the data from other investigators (9).
ORAC Values of Individual Teas and Tea
Products
The ORAC values of the individual teas and tea products
were also determined with the modified ORAC assay. The
standard and samples were diluted with the 75-mM sodium
acetate buffer (pH 5.5). ORAC values varied from 728 to
1,372 Trolox equivalents/g tea for regular black tea and
507–618 for decaffeinated black tea. Regular green tea
ORAC values varied from 1,239 to 1,686 trolox equiva
-
lents/g tea, and the ORAC values for decaffeinated green tea
varied from 765 to 845 trolox equivalents/g tea (Table 5). Fig.
5 shows the correlation between the ORAC value and the
catechin content of individual teas with r = 0.79 (P = 0.0001).
The ORAC value of the green tea extract supplement was
higher than all the green or black tea brews, whereas the iced
teas showed the lowest ORAC values (Table 5).
Discussion
The antioxidant capacity of polyphenols in vivo is due to
several factors: 1) radical scavenging activity, 2) metal
ion-chelating effect, 3) stability of the resulting radical
formed after scavenging, 4) pH sensitivity, and 5) solubility
in the lipophilic phase (36). As shown by Van Acker et al.
(37), the free radical scavenging activity is related to the elec
-
trochemical oxidation potential of the flavonoids. Flavonoids
with the lowest electrochemical potential showed a high radi
-
cal scavenging activity (36). Measurements of the struc
-
ture-activity relationship by other investigators (36,37)
showed that the radical scavenging activity is highest in
flavonoids with either a catechol or pyrogallol group in the B
ring. The additional double bond between C2-C3 and the
3-OH group enhanced the scavenging activity. The metal
ion-chelating activity also depended on the catechol structure
as well as the hydroxyl group in position 3 (36). In addition,
Cao et al. (36) pointed out that an increase in the number of
OH substitutions in the A- and B-ring corresponded to a
stronger antioxidant response as determined by the ORAC
assay.
The ORAC assay provides an effective way to evaluate the
potential antioxidant capacity of various phytochemicals,
foods, beverages, or biological samples (38). The assay used
in this study measures the capacity of individual compounds
or mixtures of compounds to scavenge the peroxyl radicals
generated from AAPH at an elevated temperature. The order
of antioxidant capacity for the different catechin standard so
-
lutions was ECG > EGCG > EC = catechin > EGC > mixed
Vol. 45, No. 2 229
230 Nutrition and Cancer 2003
Figure 2. HPLC chromatograms of (A) catechin and caffeine standard mixture, (B) Uncle Lee’s Green Tea, and (C) theaflavin standard mixture.
Vol. 45, No. 2 231
Table 2a. Determination of Catechin Content of 11 Black Teas and 2 Iced Teas
a
Tea Catechin
Wissotzky
Earl Grey
Bigelow
Constant
Comment
Bigelow
English
Teatime
Twinings
English
Breakfast Tea
Bigelow
Darjeling
Blend
Twinings Irish
Breakfast
Black Tea
Lipton
Black Tea
Twinings
Earl Grey
Black Tea
Sweet Touch
NEE Black
Tea
Bigelow
Constant
Comment Decaf
Bigelow
English Tea
Time Decaf
Lipton
Lemon
Iced Tea
Snapple
Peach Iced
Tea
mg/100 ml (= teabag)
Gallic acid 3.3 ± 0.7 3.1 ± 0.1 6.8 ± 0.1 4.5 ± 0.4 6.4 ± 0.1 5.6 ± 0.1 6.5 ± 0.1 5.6 ± 0.2 5.6 ± 0.5 3.0 ± 0.1 4.6 ± 0.2 0.0 ± 0 0.0 ± 0
Caffeine 27.1 ± 5.1 25.3 ± 0.2 51.6 ± 1.3 45.4 ± 1.7 55.1 ± 0.1 39.4 ± 4.4 36.2 ± 1.6 31.5 ± 0.8 38.1 ± 2.3 2.7 ± 0.1 3.4 ± 0.2 2.0 ± 0 6.5 ± 0
EGC 0.0 ± 0 0.0 ± 0 14.8 ± 0.3 0.0 ± 0 11.6 ± 1.0 23.5 ± 10.3 6.2 ± 0.9 4.1 ± 2.1 0.0 ± 0 0.0 ± 0 0.0 ± 0 0.0 ± 0 0.0 ± 0
Catechin 8.1 ± 2.0 7.2 ± 0 15.4 ± 0.6 13.1 ± 1.9 16.2 ± 0.1 3.5 ± 0.5 2.7 ± 0.3 4.4 ± 0.8 12.1 ± 0.9 0.0 ± 0 0.0 ± 0 0.0 ± 0 0.0 ± 0
Epicatechin 2.9 ± 0.2 4.1 ± 0.1 9.0 ± 0.1 5.2 ± 0.2 5.6 ± 0.2 2.3 ± 0 5.3 ± 0.4 5.2 ± 0.3 1.1 ± 0.3 0.0 ± 0 0.0 ± 0 0.0 ± 0 0.0 ± 0
EGCG 3.8 ± 1.0 6.8 ± 0 27.3 ± 0.6 10.9 ± 0.6 74.5 ± 0.8 8.1 ± 2.6 8.9 ± 0.6 10.8 ± 0.5 9.4 ± 0.6 0.0 ± 0 0.0 ± 0 0.0 ± 0 0.0 ± 0
GCG 2.3 ± 0.8 3.0 ± 0 2.9 ± 0.1 2.0 ± 0 8.7 ± 0.3 4.8 ± 1.9 4.2 ± 0.5 2.6 ± 0.7 3.6 ± 0.6 2.0 ± 0.2 2.4 ± 0.1 0.0 ± 0 0.0 ± 0
ECG 2.0 ± 0.5 2.7 ± 0.2 9.4 ± 0.2 4.8 ± 0.3 21.3 ± 1.2 3.8 ± 2.0 4.5 ± 0.1 5.4 ± 0.5 1.4 ± 1.7 2.0 ± 0.2 0.0 ± 0 0.0 ± 0 0.0 ± 0
Catechin gallate 3.1 ± 0.7 2.3 ± 0 2.8 ± 0 4.3 ± 0.2 4.3 ± 0 3.3 ± 0.4 3.0 ± 0 1.5 ± 0 3.7 ± 0.2 0.5 ± 0.7 1.2 ± 0.1 0.0 ± 0 0.0 ± 0
Total theaflavin 13.3 ± 4.3 9.0 ± 0.2 10.9 ± 0.7 20.1 ± 3.5 8.8 ± 0.2 10.2 ± 1.3 14.2 ± 1.0 7.3 ± 0 18.1 ± 1.1 2.2 ± 0.3 2.0 ± 0.1 0.0 ± 0 0.0 ± 0
Total catechin 20.4 ± 3.3 26.0 ± 0.4 81.6 ± 1.9 40.4 ± 0.7 148.7 ± 0.8 49.3 ± 2.9 34.8 ± 1.9 32.6 ± 3.1 31.2 ± 1.0 4.6 ± 0.3 3.6 ± 0.2 0.0 ± 0 0.0 ± 0
Total catechin +
theaflavins + gallic
acid
38.8 ± 9.8 38.1 ± 0.3 99.4 ± 2.7 65.0 ± 2.4 163.9 ± 0.6 65.2 ± 1.5 55.5 ± 2.8 45.6 ± 3.3 54.8 ± 2.5 9.8 ± 0.1 10.1 ± 0.5 0.0 ± 0 0.0 ± 0
Total catechin +
theaflavins + gallic
acid/g tea
24.3 ± 6.1 21.2 ± 0.2 43.2 ± 1.2 31.0 ± 1.2 68.3 ± 0.2 31.0 ± 0.7 23.1 ± 1.2 21.7 ± 1.6 23.8 ± 1.1 5.4 ± 0.03 4.6 ± 0.2 n/a n/a
a: n =2.
232 Nutrition and Cancer 2003
Table 2b. Determination of Catechin Content of 8 Green Teas and 1 Green Tea Extract Supplement
a
Tea Catechin
Bigelow
Green Tea
Celestial
Seasoning
Green Tea
Uncle Lee’s
Green Tea
Salada
Green Tea
Earl Green
Lipton
Green Tea
Stash Premium
Green Tea
Decaf
Salada
Green Tea
Decaf
Celestial
Seasoning Decaf
Green Tea
Green Tea
Supplement
Green Tea
Supplement
mg/100 ml per capsule
b
per g powder
Gallic acid 1.5 ± 0.1 0.6 ± 0 1.0 ± 0.1 0.8 ± 0.1 1.2 ± 0 0.7 ± 0.1 2.0 ± 0 1.8 ± 0.1 9.6 ± 0.5 27.4 ± 1.4
Caffeine 23.6 ± 1.5 33.6 ± 0.2 29.4 ± 2.7 21.8 ± 1.8 33.1 ± 0.7 5.8 ± 0.6 3.8 ± 0 0.7 ± 0 5.7 ± 0.2 16.3 ± 0.6
EGC 30.9 ± 1.5 79.7 ± 1.0 49.2 ± 2.3 38.7 ± 2.9 76.4 ± 1.8 22.0 ± 1.5 23.8 ± 0.3 22.2 ± 0.4 7.6 ± 1.5 21.7 ± 4.3
Catechin 0.0 ± 0 4.4 ± 0.1 3.6 ± 0.5 0.0 ± 0 5.8 ± 0.9 0.0 ± 0 3.4 ± 0.5 0.0 ± 0 4.7 ± 0.1 13.4 ± 0.3
Epicatechin 6.5 ± 0.4 13.3 ± 0.1 15.4 ± 1.2 7.0 ± 0.6 11.9 ± 0.1 0.0 ± 0 4.1 ± 0 2.9 ± 0 6.9 ± 0.3 19.7 ± 0.9
EGCG 42.5 ± 2.5 99.3 ± 1.8 65.0 ± 7.1 49.8 ± 3.6 83.9 ± 2.8 20.7 ± 1.8 46.3 ± 0.7 37.7 ± 0.8 100.5 ± 3.4 285.1 ± 9.7
GCG 4.1 ± 0.2 5.4 ± 0.3 4.3 ± 0.4 3.1 ± 0.3 1.1 ± 0.1 3.6 ± 0.6 6.2 ± 0.1 3.4 ± 0 52.8 ± 2.2 150.9 ± 6.3
ECG 3.6 ± 0 4.0 ± 1.6 15.9 ± 1.5 9.5 ± 0.8 13.7 ± 0.3 6.1 ± 0.6 2.0 ± 0.1 5.2 ± 0.3 25.2 ± 0.8 72.0 ± 2.3
Catechin gallate 0.0 ± 0 10.0 ± 1.2 2.4 ± 0.2 0.3 ± 0.5 3.1 ± 0.1 0.4 ± 0.5 1.1 ± 0 0.9 ± 0 7.7 ± 0.2 22.0 ± 0.6
Total catechin 87.5 ± 4.6 216.2 ± 0.5 155.7 ± 13.2 108.5 ± 8.6 196.6 ± 5.2 52.7 ± 5.0 86.8 ± 0.7 72.3 ± 0.7 205.4 ± 5.5 584.8 ± 15.7
Total catechin +
gallic acid
89.0 ± 4.6 216.7 ± 0.5 156.8 ± 13.3 109.3 ± 8.7 197.8 ± 5.2 53.3 ± 5.0 88.8 ± 0.7 74.1 ± 0.6 214.9 ± 6.0 612.2 ± 17.1
Total catechin +
gallic acid/g
tea
59.3 ± 3.1 103.2 ± 0.3 78.4 ± 6.6 60.7 ± 4.8 82.4 ± 2.2 26.7 ± 2.5 52.2 ± 0.4 39.0 ± 0.3
a: n =2.
b: 350 mg teasolids per capsule.
theaflavins > gallic acid. This is in good agreement with the
structure-activity analysis by Van Acker et al. and Cao et al.
(36,37) and with results by Salah et al. (39). The results from
our study, however, indicate that epicatechin and catechin
have a stronger radical scavenging potential than EGC and
gallic acid. This is possibly due to the pH stability of
epicatechin and catechin. As shown in Fig. 3, catechin and
epicatechin are more stable in the pH range from 5 to 7 than
EGC and gallic acid. The antioxidant capacity of theaflavins
and their gallate esters has also been evaluated by Miller et al.
(40) and Leung et al. (41). In these studies, however, the anti
-
oxidant capacity was measured via Cu
2+
-mediated LDL oxi
-
dation, which is an indication of the metal ion-chelating ca
-
pacity rather than their radical scavenging activity. In our
study, the black tea extract theaflavin mix purchased from
Sigma was ranked low compared with the other flavanols.
Due to the lack of purified individual theaflavin standards,
we were unable to determine the ORAC value for individual
theaflavins.
The tea flavanol analysis (Tables 2a and b) showed large
variations among teas from different brands. This variation
was larger than the standard deviation of flavanol concentra
-
tions determined in teas of the same brand but different lot
numbers (Table 3). Therefore, we concluded that the differ
-
ence among brands (Tables 2a and b) is due to different pro
-
duction conditions and technologies of the tea companies
rather than differences in production lots, shelf life, and stor
-
age conditions. The flavanol contents determined in our anal
-
yses compared well with flavanol contents published by
Khokhar and Magnusdottir (47). They also found that
Darjeeling tea contained a large amount of flavanols com
-
pared with other black teas.
Vol. 45, No. 2 233
Table 3. Catechin Content in Tea With Different Lot
Numbers
a
Tea Catechin
Uncle Lee’s Green
Tea
Lipton Green
Tea
Bigelow
Darjeeling
Blend
Gallic acid 1.0 ± 0.2 1.3 ± 0.61 6.2 ± 0.4
Caffeine 46.5 ± 3.2 29.0 ± 2.4 67.0 ± 3.9
EGC 79.8 ± 14.5 80.2 ± 6.2 16.8 ± 0.9
Catechin 4.5 ± 1.6 4.9 ± 1.7 4.3 ± 0.4
Epicatechin 18.9 ± 0.9 16.3 ± 1.7 5.1 ± 0.4
EGCG 97.2 ± 13.0 83.3 ± 14.9 96.0 ± 7.2
GCG 7.6 ± 1.6 3.3 ± 0.9 8.0 ± 0.4
ECG 19.4 ± 3.4 10.5 ± 3.2 21.7 ± 1.6
Total catechins 230.4 ± 28.9 201.4 ± 27.2 151.9 ± 10.5
a: n = 2.
Figure 3. HPLC peak area of gallic acid, EGC, EC, EGCG, and ECG ex
-
posed to pH 3–7.
Figure 4. Kinetic change of HPLC peak area of EGC, EC, EGCG, and ECG
at pH 7.
Table 4. ORAC Value of Different Catechins and
Flavonoids
a
Catechins ORAC (mmol /mmol) ORAC (mmol /mg)
Gallic acid 2.7 15.9
Epigallocatechin 4.6 15.0
Epicatechin 6.7 23.1
Catechin 6.1 21.0
Epicatechin gallate 10.4 23.5
Gallocatechin gallate 6.4 14.0
Epigallocatechin gallate 8.2 17.9
Quercetin 6.7 22.2
Kaempherol 2.6 9.1
Naringenin 2.4 8.8
Ascorbic acid 1.2 6.8
Caffeine 0.4 2.1
a: ORAC values are expressed as means of two determinations.
The ORAC values of the individual teas, determined in
this study, are similar to the values obtained by Cao et al.
(38). The regression analysis of the ORAC value in relation
to the flavanol content of the individual teas demonstrated
that the flavanol content is responsible to a large extent for
the antioxidant capacity of tea. However, there are other fac
-
tors such as the thearubigin and rutin content that can explain
the relatively high ORAC value of some black teas with low
flavanol and theaflavin content. Iced teas also represented an
exception with a zero flavanol content but an ORAC value of
790 and 609 µmol/100 ml of tea. This antioxidant capacity is
most likely due to other food additives with antioxidant activ
-
ity in the iced tea beverages.
The large variation in flavanol content and ORAC value
among different teas may be an important factor responsible
for the inconsistency of epidemiological studies in regard to
cancer prevention (Table 1). It appears that most reports sup
-
porting the cancer prevention effects of tea were performed
in Asian countries where green tea is predominantly con
-
sumed (42). In studies conducted in European countries,
where the consumption of black tea is more common, a pro
-
tective effect was less frequently observed (43). The ORAC
values and flavanol contents of the individual teas deter
-
mined in our study support this observation. Black teas, espe
-
cially decaffeinated teas, show a much larger variability in
catechin content and ORAC value compared with green teas.
Because epidemiological studies to this day do not account
for the type and flavonoid content of different teas in their as
-
sessment of tea consumption, the outcome may differ
depending on the characteristics of the particular teas con
-
sumed. More studies like the Arizona study are needed, in
which tea consumption and the tea preparation were care
-
fully evaluated using a detailed tea questionnaire. In this
study a chemopreventive effect of the consumption of >1cup
of hot tea in squamous cell carcinoma was determined (20).
Our results confirm that the ORAC value is a good in vitro
indicator of the antioxidant capacity of purified compounds
and beverages. However, for the in vivo evaluation, the ab-
sorption and metabolism of flavanols have to be taken into
consideration (44–46).
Acknowledgments and Notes
This study was supported by NIH Grants No. 5P50AT00151,
CA91163-01, and RO3 CA91163-02. We thank He-Jing Wang for perform
-
ing the statistical analysis. Address correspondence to Susanne M. Henning,
UCLA Center for Human Nutrition, School of Medicine, Warren Hall,
14-166, 900 Veteran Avenue, Los Angeles, CA 90095. Phone: (310)
825-9345. FAX: (310) 206-5264. E-mail: shenning@mednet.ucla.edu.
Submitted 15 October 2002; accepted in final form 12 February 2003.
References
1. Yang CS, Landau JM, Huang MT, and Newmark HL: Inhibition of
carcinogenesis by dietary polyphenolic compounds. Annu Rev Nutr
21, 381–406, 2001.
2. Balentine DA, Wiseman SA, and Bouwens LC: The chemistry of tea
flavonoids. Crit Rev Food Sci Nutr 37, 693–704, 1997.
3. Subramanian N, Venkatesh P, Ganguli S, and Sinkar VP: Role of
polyphenol oxidase and peroxidase in the generation of black tea
theaflavins. J Agric Food Chem 47, 2571–2578, 1999.
4. Yang CS, Chung JY, Yang G, Chhabra SK, and Lee MJ: Tea and tea
polyphenols in cancer prevention. J Nutr 130, 472S–478S, 2000.
5. Chen Z, Zhu QY, Tsang D, and Huang Y: Degradation of green tea
catechins in tea drinks. J Agric Food Chem 49, 477–482, 2001.
6. Cao G and Prior RL: Measurement of oxygen radical absorbance ca
-
pacity in biological samples. Methods Enzymol 299, 50–62, 1999.
7. Imai K, Suga K, and Nakachi K: Cancer-preventive effects of drinking
green tea among a Japanese population. Prev Med 26, 769–775, 1997.
234 Nutrition and Cancer 2003
Table 5. ORAC Values of Different Teas and a Green Tea
Extract
a
Tea Brand
Trolox Equivalent
(mmol/g tea)
Total Catechin
(mg/g tea)
Green Tea Supplement
b
3461 ± 66 204.7
Celestial Seasonings Authentic
Green Tea
1686 ± 47 105.7
Bigelow Green Tea 1477 ± 24 58.6
Uncle Lee’s Green Tea 1477 ± 4 76.7
Lipton Black Tea 1372 ± 24 22.8
Salada Green Tea Earl Green 1250 ± 26 59.7
Lipton Green Tea 1239 ± 47 84.3
Wissotzky Earl Grey 1205 ± 58 23.6
Bigelow English Tea Time 1189 ± 42 43.8
Bigelow Darjeeling Blend 1079 ± 50 68.1
Sweet Touch NEE Black Tea 967 ± 39 23.5
Twinnings English Breakfast Tea 935 ± 33 30.0
Celestial Seasonings Decaf
Mandarin Orange
845 ± 24 39.9
Twinning Irish Breakfast 811 ± 54 30.0
Snapple Peach Ice Tea
c
790 ± 36 0
Stash Premium Green Tea Decaf 765 ± 14 26.4
Bigelow Constant Comment 757 ± 53 21.7
Twinnings Earl Grey Black Tea 728 ± 35 21.6
Bigelow Constant Comment Decaf 618 ± 33 5.4
Lipton Lemon Ice Tea
c
609 ± 15 0
Bigelow English Tea Time Decaf 507 ± 46 4.7
a: ORAC values are expressed as means ± SD of n = 6 samples. Catechin
concentrations are means of two measurements.
b: ORAC value per capsule (350 mg teegreen extract powder).
c: ORAC value per 100 ml of iced tea.
Figure 5. Correlation of ORAC value to catechin content of 18 green and
black teas.
8. Zhong L, Goldberg MS, Gao YT, Hanley JA, Parent ME, et al.: A pop
-
ulation-based case-control study of lung cancer and green tea con
-
sumption among women living in Shanghai, China. Epidemiology 12,
695–700, 2001.
9. Mendilaharsu M, De Stefani E, Deneo-Pellegrini H, Carzoglio JC, and
Ronco A: Consumption of tea and coffee and the risk of lung cancer in
cigarette-smoking men: a case-control study in Uruguay. Lung Cancer
19, 101–107, 1998.
10. Ohno Y, Wakai K, Genka K, Ohmine K, Kawamura T, et al.: Tea con
-
sumption and lung cancer risk: a case-control study in Okinawa, Japan.
Jpn J Cancer Res 86, 1027–1034, 1995.
11. Setiawan VW, Zhang ZF, Yu GP, Lu QY, Li YL, et al.: Protective effect
of green tea on the risks of chronic gastritis and stomach cancer. Int J
Cancer 92, 600–604, 2001.
12. Inoue M, Tajima K, Hirose K, Hamajima N, Takezaki T, et al.: Tea and
coffee consumption and the risk of digestive tract cancers: data from a
comparative case-referent study in Japan. Cancer Causes Control 9,
209–216, 1998.
13. Ji BT, Chow WH, Hsing AW, McLaughlin JK, Dai Q, et al.: Green tea
consumption and the risk of pancreatic and colorectal cancers. Int J
Cancer 70, 255–258, 1997.
14. Zheng W, Doyle TJ, Kushi LH, Sellers TA, Hong CP, et al.: Tea con
-
sumption and cancer incidence in a prospective cohort study of
postmenopausal women. Am J Epidemiol 144, 175–182, 1996.
15. Yu GP, Hsieh CC, Wang LY, Yu SZ, Li XL, et al.: Green-tea consump
-
tion and risk of stomach cancer: a population-based case-control study
in Shanghai, China. Cancer Causes Control 6, 532–538, 1995.
16. Gao YT, McLaughlin JK, Blot WJ, Ji BT, Dai Q, et al.: Reduced risk of
esophageal cancer associated with green tea consumption. JNCI 86,
855–858, 1994.
17. Nakachi K, Suemasu K, Suga K, Takeo T, Imai K, et al.: Influence of
drinking green tea on breast cancer malignancy among Japanese pa-
tients. Jpn J Cancer Res 89, 254–261, 1998.
18. Shibata K, Moriyama M, Fukushima T, Kaetsu A, Miyazaki M, et al.:
Green tea consumption and chronic atrophic gastritis: a cross-sectional
study in a green tea production village. J Epidemiol 10, 310–316,
2000.
19. Ye WM, Yi YN, Luo RX, Zhou TS, Lin RT, et al.: Diet and gastric can-
cer: a case control study in Fujian Province, China. World J
Gastroenterol 4, 516–518, 1998.
20. Hakim IA, Harris RB, and Weisgerber UM: Tea intake and squamous
cell carcinoma of the skin: influence of type of tea beverages. Cancer
Epidemiol Biomarkers Prev 9, 727–731, 2000.
21. Zeegers MP, Dorant E, Goldbohm RA, and van den Brandt PA: Are
coffee, tea, and total fluid consumption associated with bladder cancer
risk? Results from the Netherlands Cohort Study. Cancer Causes Con
-
trol 12, 231–238, 2001.
22. Ji BT, Chow WH, Yang G, McLaughlin JK, Gao RN, et al.: The influ
-
ence of cigarette smoking, alcohol, and green tea consumption on the
risk of carcinoma of the cardia and distal stomach in Shanghai, China.
Cancer 77, 2449–2457, 1996.
23. Tsubono Y, Nishino Y, Komatsu S, Hsieh CC, Kanemura S, et al.:
Green tea and the risk of gastric cancer in Japan. N Engl J Med 344,
632–636, 2001.
24. Goldbohm RA, Hertog MG, Brants HA, van Poppel G, and van den
Brandt PA: Consumption of black tea and cancer risk: a prospective
cohort study. JNCI 88, 93–100, 1996.
25. Michels KB, Holmberg L, Bergkvist L, and Wolk A: Coffee, tea, and
caffeine consumption and breast cancer incidence in a cohort of Swed
-
ish women. Ann Epidemiol 12, 21–26, 2002.
26. Nagano J, Kono S, Preston DL, and Mabuchi K: A prospective study of
green tea consumption and cancer incidence, Hiroshima and Nagasaki
(Japan). Cancer Causes Control 12, 501–508, 2001.
27. Zeegers MP, Tan FE, Goldbohm RA, and van den Brandt PA: Are cof
-
fee and tea consumption associated with urinary tract cancer risk? A
systematic review and meta-analysis. Int J Epidemiol 30, 353–362,
2001.
28. Villeneuve PJ, Johnson KC, Kreiger N, and Mao Y: Risk factors for
prostate cancer: results from the Canadian National Enhanced Cancer
Surveillance System. The Canadian Cancer Registries Epidemiology
Research Group. Cancer Causes Control 10, 355–367, 1999.
29. Cerhan JR, Putnam SD, Bianchi GD, Parker AS, Lynch CF, et al.: Tea
consumption and risk of cancer of the colon and rectum. Nutr Cancer
41, 33–40, 2001.
30. La Vecchia C, Negri E, Franceschi S, D’Avanzo B, and Boyle P: Tea
consumption and cancer risk. Nutr Cancer 17, 27–31, 1992.
31. Bianchi GD, Cerhan JR, Parker AS, Putnam SD, See WA, et al.: Tea
consumption and risk of bladder and kidney cancers in a popula
-
tion-based case-control study. Am J Epidemiol 151, 377–383, 2000.
32. Terry P and Wolk A: Tea consumption and the risk of colorectal cancer
in Sweden. Nutr Cancer 39, 176–179, 2001.
33. Woolcott CG, King WD, and Marrett LD: Coffee and tea consumption
and cancers of the bladder, colon and rectum. Eur J Cancer Prev 11,
137–145, 2002.
34. Tavani A, Gallus S, Dal Maso L, Franceschi S, Montella M, et al.: Cof
-
fee and alcohol intake and risk of ovarian cancer: an Italian case-con
-
trol study. Nutr Cancer 39, 29–34, 2001.
35. Tavani A, Pregnolato A, La Vecchia C, Negri E, Talamini R, et al.: Cof
-
fee and tea intake and risk of cancers of the colon and rectum: a study
of 3,530 cases and 7,057 controls. Int J Cancer 73, 193–197, 1997.
36. Cao G, Sofic E, and Prior RL: Antioxidant and prooxidant behavior of
flavonoids: structure-activity relationships. Free Radic Biol Med 22,
749–760, 1997.
37. van Acker SA, van den Berg DJ, Tromp MN, Griffioen DH, van
Bennekom WP, et al.: Structural aspects of antioxidant activity of
flavonoids. Free Radic Biol Med 20, 331–342, 1996.
38. Cao G, Sofic E, and Prior RL: Antioxidant capacity of tea and common
vegetables. J Agric Food Chem 44, 3426–3431, 1996.
39. Salah N, Miller NJ, Paganga G, Tijburg L, Bolwell GP, et al.:
Polyphenolic flavanols as scavengers of aqueous phase radicals and as
chain-breaking antioxidants. Arch Biochem Biophys 322, 339–346,
1995.
40. Miller NJ, Castelluccio C, Tijburg L, and Rice-Evans C: The antioxi
-
dant properties of theaflavins and their gallate esters—radical scaven
-
gers or metal chelators? FEBS Lett 392, 40–44, 1996.
41. Leung LK, Su Y, Chen R, Zhang Z, Huang Y, et al.: Theaflavins in
black tea and catechins in green tea are equally effective antioxidants.
J Nutr 131, 2248–2251, 2001.
42. Bushman JL: Green tea and cancer in humans: a review of the litera
-
ture. Nutr Cancer 31, 151– 159, 1998.
43. Blot WJ, McLaughlin JK, and Chow WH: Cancer rates among drink
-
ers of black tea. Crit Rev Food Sci Nutr 37, 739–760, 1997.
44. Lee MJ, Wang ZY, Li H, Chen L, Sun Y, et al.: Analysis of plasma and
urinary tea polyphenols in human subjects. Cancer Epidemiol
Biomarkers Prev 4, 393–399, 1995.
45. Warden BA, Smith LS, Beecher GR, Balentine DA, and Clevidence
BA: Catechins are bioavailable in men and women drinking black tea
throughout the day. J Nutr 131, 1731–1737, 2001.
46. Scalbert A and Williamson G: Dietary intake and bioavailability of
polyphenols. J Nutr 130, 2073S–2085S, 2000.
47. Khokhar S and Magnusdottir SGM: Total phenol, catechin and caf
-
feine contents of teas commonly consumed in the United Kingdom. J
Agric Food Chem 50, 565–570, 2002.
Vol. 45, No. 2 235
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Książka z zakresu współczesnej technologii przetwórstwa surowców na produkty akceptowalne przez konsumentów. Poświęcona zagadnieniu enzymatycznego brązowienia mętnego soku jabłkowego, prezentuje badania na temat możliwości wykorzystania na przykład ekstraktów z roślin czy innych soków do przedłużania trwałości mętnych soków jabłkowych w aspekcie ich barwy. Badania te wpisują się w nurt dotyczący roli naturalnych przeciwutleniaczy jako inhibitorów brązowienia enzymatycznego.
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Nine black tea samples with different color intensity were firstly determined by chromatic difference analyzer. The color characteristics were secondly quantitatively described by UV-visible spectroscopy. Thirdly, liquid chromatography tandem mass spectrometry (LC-MS) based metabolomics analysis was applied in low-molecular-weight compounds. Finally, the color contributors were identified by the correlation analysis of color, spectrometry and mass data. UV-visible based metabolomics analysis revealed that the wavelength at 380-520 nm (VIP > 1.50) was the critical absorbance band for distinguishing different color of BT infusions, while LC-MS based metabolomics analysis indicated that there were 48 main marker compounds responsible for the classification of different BT infusions. Correlation analysis results showed that the coefficients of theaflavins, thearubigins, theabrownins, flavonoid glycosides, and some hydroxycinnamoyl acids were > 0.7, which suggested they were main color contributors of BT infusion. The present study expanded a new vision on the color analysis of BT infusion.
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The main dietary sources of polyphenols are reviewed, and the daily intake is calculated for a given diet containing some common fruits, vegetables and beverages. Phenolic acids account for about one third of the total intake and flavonoids account for the remaining two thirds. The most abundant flavonoids in the diet are flavanols (catechins plus proanthocyanidins), anthocyanins and their oxidation products. The main polyphenol dietary sources are fruit and beverages (fruit juice, wine, tea, coffee, chocolate and beer) and, to a lesser extent vegetables, dry legumes and cereals. The total intake is ∼1 g/d. Large uncertainties remain due to the lack of comprehensive data on the content of some of the main polyphenol classes in food. Bioavailability studies in humans are discussed. The maximum concentration in plasma rarely exceeds 1 μM after the consumption of 10–100 mg of a single phenolic compound. However, the total plasma phenol concentration is probably higher due to the presence of metabolites formed in the body's tissues or by the colonic microflora. These metabolites are still largely unknown and not accounted for. Both chemical and biochemical factors that affect the absorption and metabolism of polyphenols are reviewed, with particular emphasis on flavonoid glycosides. A better understanding of these factors is essential to explain the large variations in bioavailability observed among polyphenols and among individuals.
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AIM: To explore the relationship between consumption of fish sauce, other dietary factors, living habits and the risk of gastric cancer. METHODS: From May 1994 to July 1995, a population-based 1:2 case-control study was in Carried out in high-risk areas of gastric cancer, Changle and Fuqing cities, Fujian Province. Totally 272 cases and 544 age, gender-matched controls were included. Risk state analyses were made by ASRS package. RESULTS: Risk state single-factor analysis indicated that gastric cancer risk rose with high intake of fish sauce (OR = 2.57), salted vegetables (OR = 1.41), salted/fried fish and small shrimps (OR = 1.57), low consumption of fresh vegetables (OR = 1.95), fresh citrus fruits (OR = 1.41), other fresh fruits (OR = 1.31), green tea (OR = 1.72), exposure to moldy foods (OR = 2.32), irregular dinners (OR = 5.47) and familial history of malignancy (OR = 3.27). No significant relationship was observed between smoking, drinking, salt intake, use of refrigerator and gastric cancer risk. The results of risk state conditional Logistic regression showed that fish sauce, salted dried fish and small shrimps, irregular dinners, familial history of malignancy were included in the best risk set. The summary ARS for the four factors was 75.49%. CONCLUSION: High intake of fish sauce, salted foods, moldy foods, irregular dinners and familial history of malignancy were possible risk factors for gastric cancer, whereas fresh vegetables and fruits. And green tea might have protective effects for gastric cancer. Keywords: stomach neoplasms/etiology, living habits, food habits, risk facto Citation: Ye WM, Yi YN, Luo RX, Zhou TS, Lin RT, Chen GD. Diet and gastric cancer: a case-control study in Fujian Province, China. World J Gastroenterol 1998; 4(6): 516-518
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Publisher Summary Several methods have been developed to assess the total antioxidant capacities of various biological samples, particularly complex matrices such as plasma, serum, wine, fruits, vegetables, and animal tissues. This chapter presents a method called “oxygen radical absorbance capacity” (ORAC) assay based largely on the work reported by Glazer's laboratory, which depends on the unique properties of phycoerythrin (PE). The ORAC assay is the only method that takes reactive species (RS) reaction to completion and uses an “area under the curve” (AUC) technique for quantitation, thus combining both inhibition time and inhibition percentage of the RS action by antioxidants into a single quantity. The chapter discusses the general principles of ORAC assay for assessing antioxidant capacity against peroxyl radicals. By integrating inhibition percentages over the whole inhibition time period, the ORAC assay successfully overcomes all related problems in quantitation of the antioxidant capacity of a biological sample. Either B- or R-phycoerythrin (B-PE or R-PE) can be used in the ORAC assay. The sensitivity of B- or R-PE to hydroxyl radical damage may be different even for the same PE with different lot numbers. The concentrations of Cu 2+ and standard (Tro lox) can be adjusted, when it is necessary. The aforementioned procedures are based on using B- or R-PE that loses more than 90% of its fluorescence within 30 rains. The chapter concludes with a discussion of ORAC assay for assessing antioxidant capacity against transition metals.
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AIM To explore the relationship between consumption of fish sauce, other dietary factors, living habits and the rish kf gastric cancer. METHODS From May 1994 to July 1995, a population-based 1:2 case-control study was in Carried out in high-risk areas of gastric cancer, Changle and Fuqing cities, Fujian Province. Totally 272 cases and 544 age, gender-matched controls were included. Risk state analyses were made by ASRS package. RESULTS Risk state single-factor analysis indicated that gastric cancer risk rose with high intake of fish sauce ( OR=2.57 ), salted vegetables (OR=1.41), salted/fried fish and small shrimps (OR=1.57), low consumption of fresh vegetables (OR=1.95), fresh citrus fruits (OR = 1.41), other fresh fruits (OR = 1.31), green tea (OR=1.72), exposure to moldy foods (OR=2.32), irregular dinners (OR=5.47) and familial history of malignancy (OR=3.27). No significant relationship was observed between smoking, drinking, salt intake, use of refrigerator and gastric cancer rish. The results of rish state conditional Logistic regression showed that fish sauce, salted dried fish and small shrimps, irregular dinners, familial history of malignancy were included in the best rish set. The summary ARS for the four factors was 75.49%. CONCLUSION High intake of fish sauce, salted foods, moldy foods, irregular dinners and familial history of malignancy were possible risk factors for gastric cancer, whereas fresh vegetables and fruits. and green tea might have protective effects for gastric cancer.
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The effect of green tea drinking in reducing human cancer risk is unclear, though a protective effect has been reported in numerous animal studies and several epidemiologic investigations. Herein the hypothesis that green tea consumption may reduce the risk of cancers of the colon, rectum and pancreas is examined in a large population-based case-control study conducted in Shanghai, China. Newly diagnosed cancer cases (931 colon, 884 rectum and 451 pancreas) during 1990–1993 among residents 30–74 years of age were included. Controls (n = 1,552) were selected among Shanghai residents and frequency-matched to cases by gender and age. Multivariate odds ratios (ORs) and 95% confidence intervals (Cls) of each cancer associated with green tea consumption were derived after adjustment for age, income, education and cigarette smoking. Additional adjustment for dietary items and body size was found to have minimal impact. An inverse association with each cancer was observed with increasing amount of green tea consumption, with the strongest trends for rectal and pancreatic cancers. For men, compared with non-regular tea drinkers, ORs among those in the highest tea consumption category (≥300 g/month) were 0.82 for colon cancer, 0.72 for rectal cancer and 0.63 for pancreatic cancer, with p values for trend being 0.38, 0.04 and 0.04, respectively. For women, the respective ORs for the highest consumption category (≥200 g/month) were 0.67, 0.57 and 0.53, with the respective p values for trend being 0.07, 0.001 and 0.008. Our findings provide further evidence that green tea drinking may lower the risk of colorectal and pancreatic cancers. Int. J. Cancer, 70:255–258, 1997. © 1997 Wiley-Liss, Inc.†
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Inhibitory effects of green tea on carcinogenesis have been investigated in numerous laboratory studies using (–)-epigallocatechin gallate (EGCG) or crude green tea extract, and there is also some epidemiologic evidence. Further, EGCG has been reported to inhibit the growth of cancer cells, lung metastasis in an animal model, and urokinase activity. In this study, we first examined the association between consumption of green tea prior to clinical cancer onset and various clinical parameters assessed at surgery among 472 patients with stage I, II, and III breast cancer. We found that increased consumption of green tea was closely associated with decreased numbers of axillary lymph node metastases among premenopausal patients with stage I and II breast cancer and with increased expression of progesterone receptor (PgR) and estrogen receptor (ER) among postmenopausal ones. Since these are potential prognostic factors, we then investigated the prognosis of breast cancer with special reference to consumption of green tea, in a follow-up study of these patients. We found that increased consumption of green tea was correlated with decreased recurrence of stage I and II breast cancer (P<0.05 for crude disease-free survival); the recurrence rate was 16.7 or 24.3% among those consuming ≥5 cups or ≥4 cups per day, respectively, in a seven-year follow-up of stage I and II breast cancer, and the relative risk of recurrence was 0.564 (95% confidence interval, 0.350–0.911) after adjustment for other lifestyle factors. However, no improvement in prognosis was observed in stage III breast cancer. Our results indicate that increased consumption of green tea prior to clinical cancer onset is significantly associated with improved prognosis of stage I and II breast cancer, and this association may be related to a modifying effect of green tea on the clinical characteristics of the cancer.
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BACKGROUND The divergent incidence patterns of gastric cardia and distal stomach cancer may suggest different etiologies. This study examined the role of cigarette smoking, alcohol drinking, and green tea consumption as risk factors for carcinoma by anatomic subsite of stomach.METHODS Newly-diagnosed stomach carcinoma patients (n = 1124) and frequency-matched population controls (n = 1451) were interviewed in person. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models.RESULTSExcess risks associated with cigarette smoking and alcohol consumption were observed largely among men. The adjusted ORs for all stomach cancer combined were 1.35 (CI: 1.06–1.71) for current smokers, and 1.26 (CI: 0.86–1.84) for ex-smokers. For tumors of the distal stomach, statistically significant positive dose-response trends were found for the number of cigarettes smoked per day, the duration and pack-years of smoking, and inverse trends for years of stopped smoking. For tumors of the gastric cardia, however, a monotonic association was found only for the number of cigarettes smoked per day (P = 0.06). Alcohol consumption was not related to the risk of cardia cancer, while a moderate excess risk of distal stomach cancer (OR: 1.55; CI: 1.07–2.26) was observed among heavy alcohol drinkers. Green tea drinking was inversely associated with risk of stomach cancer arising from either subsite, with ORs of 0.77 (CI: 0.52–1.13) among female heavy drinkers, and 0.76 (CI: 0.55–1.27) among male heavy drinkers.CONCLUSIONS Our findings provide further evidence that cigarette smoking and, possibly, alcohol consumption increase the risk of stomach carcinoma, notably of the distal segment. An inverse association with green tea drinking was also observed. Cancer 1996;77:2449-57.
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Objectives: To evaluate the relationship between prostate cancer and several potential lifestyle risk factors. Methods: We analyzed data obtained from a population-based case–control study conducted in eight Canadian provinces. Risk estimates were generated by applying multivariate logistic regression methods to 1623 histologically confirmed prostate cancer cases and 1623 male controls aged 50–74. Results: Cases were more likely to have a first-degree relative with a history of cancer, particularly prostate cancer (OR = 3.1, 95% CI = 1.8–5.4). Reduced risks of prostate cancer were observed among those of Indian descent (OR = 0.2, 95% CI = 0.1–0.5) or any Asian descent (OR = 0.3, 95% CI = 0.2–0.6) relative to those of western European descent. Total fat consumption, tomato and energy intake, were not associated with prostate cancer. The risk of prostate cancer was inversely related to the number of cigarettes smoked daily (p = 0.06) and cigarette pack-years (p < 0.01), while no association was observed between the total number of smoking years or the number of years since smoking cessation. Anthropometric measures and moderate and strenuous levels of leisure time physical activity were not strongly related to prostate cancer. In contrast, strenuous occupational activities at younger ages appeared protective. Conclusions: Our analyses are limited by the absence of data related to tumor severity and screening history. Further studies are needed to investigate the relationship between behavioral risk factors and prostate cancer screening practices.