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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
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 =
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
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
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
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).
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:
) × 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
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.
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
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
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).
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
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
Tea Catechin
Earl Grey
Breakfast Tea
Twinings Irish
Black Tea
Black Tea
Earl Grey
Black Tea
Sweet Touch
NEE Black
Comment Decaf
English Tea
Time Decaf
Iced Tea
Peach Iced
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
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
Tea Catechin
Green Tea
Green Tea
Uncle Lee’s
Green Tea
Green Tea
Earl Green
Green Tea
Stash Premium
Green Tea
Green Tea
Seasoning Decaf
Green Tea
Green Tea
Green Tea
mg/100 ml per capsule
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
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
-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
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
Tea Catechin
Uncle Lee’s Green
Lipton Green
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
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:
Submitted 15 October 2002; accepted in final form 12 February 2003.
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Salada Green Tea Earl Green 1250 ± 26 59.7
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Wissotzky Earl Grey 1205 ± 58 23.6
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Sweet Touch NEE Black Tea 967 ± 39 23.5
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Snapple Peach Ice Tea
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Stash Premium Green Tea Decaf 765 ± 14 26.4
Bigelow Constant Comment 757 ± 53 21.7
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Bigelow Constant Comment Decaf 618 ± 33 5.4
Lipton Lemon Ice Tea
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Bigelow English Tea Time Decaf 507 ± 46 4.7
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Vol. 45, No. 2 235
... This was consistent with the findings of Vinci et al. [39] and Anesini et al. [40]. Henning et al. [41] also reported a significant correlation between flavanol content in tea and oxygen radical absorbance capacity (ORAC) values. ...
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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.
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
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.
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.
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.†
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.
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.
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.