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JFS C: Food Chemistry and Toxicology
HPLC Analysis of Catechins, Theaflavins, andAlkaloids in Commercial Teas and Green TeaDietary Supplements: Comparison ofWaterand 80% Ethanol/Water ExtractsMENDEL FRIEDMAN, C AROL E. LEVIN, SUK -H YUN CHOI, ETSUKO K OZUKUE, AND NOBUYUKI K OZUKUE
ABSTRACT: To help meet the needs of consumers, producers of dietary tea supplements, and researchers for in-formation on health-promoting tea compounds, we compared the following conditions for the extraction of tea leaves and green tea-containing dietary supplements: 80% ethanol/water at 60 ◦C for 15 min and boiled water for5 min. Thefollowing 7 catechins, 4 theaflavins, and3 alkaloidswere separatedin a 70-min single HPLC analysis: (−)-epigallocatechin, (−)-catechin, (+)-epicatechin, (−)-epigallocatechin-3-gallate, (−)–gallocatechin-3-gallate, (−)-epicatechin-3-gallate, (−)-catechin-3-gallate, theaflavin, theaflavin-3-gallate, theaflavin-3-gallate, theaflavin-3,3-digallate, caffeine, theobromine, and theophylline. The following ranges of concentrations of flavonoids (catechins
plustheaflavins) in the tealeaves extracted with 80% ethanol were observed (in mg/g): in 32 black teas, 19.8 to 115.1;in 24 green teas, 12.3 to 136.3; in 14 specialty teas, 4.9 to 118.5; in 7 herbal teas, 0 to 46.0. Total alkaloids in all teasrangedfrom 0 to 32.6 mg/g. Significantly greater amountsof flavonoids were extractedfrom thetea leaveswith aque-ous ethanol than with boiled water. Levels of tea catechins in 10 capsules sold as dietary supplements were about50 to 75% lower than the amounts listed on the labels. Catechin content of 4 commercial green tea extracts rangedfrom 96 to 696 mg/g. The results make it possible to maximize the extraction of tea compounds to better relate theflavonoid and alkaloid content of teas and dietary tea supplements to their health-promoting effects.
Keywords: alkaloids, dietary supplements, flavonoids, HPLC, tea leaves
Introduction
Interest in teas, tea extracts used as dietary supplements, and tea
compoundsarisesfromthefactthatteaflavonoids(catechinsandtheaflavins) arereported to havebeneficialprotective effects against
cholesterol (Maron and others 2003); diabetes (Fukino and others
2005); chronic liver disease (Ruhl and Everhart 2005); breast (Seeley
andothers2005),lung(Yangandothers2005),prostate(Bettuzziand
others 2006), and skin cancers (Camouse and others 2005); obesity
(Berube-Parent and others 2005; Murase and others 2006; Kao and
others 2006); and pathogenic microorganisms (Cushnie and Lamb
2005; Friedman and others 2006). Flavonoid-containing cosmetics
(cosmeceuticals) are also of interest (Thornfeldt 2005). For discus-
sions of possible antioxidative and reactive oxygen species (ROS)-
suppressing mechanisms of the beneficial effects of tea flavonoids
and related dietary ingredients see Friedman (1997), Nam and
others (2005a, 2005b), and Choe and Min 2006.Teas also contain 3 pharmacologically active purine (methylx-
anthine) alkaloids: caffeine, theobromine, and theophylline. These
are also reported to exhibit beneficial effects. Selected studies de-
scribethe useof caffeineto enhancemental activity (Rao andothers
2005) and running performance (McLellan and others 2005) and to
treat apnea (absence of breathing) (Schmidt 2005) and migraine
MS 20060096 Submitted 2/13/2006, Accepted 4/29/2006. Authors Friedmanand Levinare with Western Regional Research Center, Agricultural ResearchService, US Dept. of Agriculture, Albany, CA 94710. Authors Choi, Kozukue,and Kozukue are with Uiduk Univ., Dept. of Food Service Industry, San 50 Yugeom, Gangdong, Gyeongju, Gyongbuk 780-713, Korea. Direct inquiries to author Friedman (E-mail: [email protected]).
headaches (Goldstein and others 2005) and of theophylline and
theobromine to treat asthma (Barnes 2006) and bradycardia (slow-
ness of heartbeat) (Schulz-Stubner 2005).The cited studies suggest the need to define the composition of
teas sold commercially as tea bags and of green tea extracts sold as
dietary supplements in the form of capsules, gums, powders, and
tea drinks. Although tea is generally consumed after water infusion,
isolated tea extracts and individual tea compounds are widely used
to prepare dietary supplements and tea beverages sold at retail and
in biomedical studies. Detailed knowledge of the composition will
allow consumers, researchers, and producers and distributors of
supplementsand cosmetics toselectteas,extracts, andsupplements
with the highest content of beneficial compounds.
All analytical methods for quantifying biologically active com-
pounds present in tea leaves involve extraction, separation, and
analysis. To help define the composition of commercial teas, wehad previously validated an HPLC method to analyze, in a single
run, levels of 7 catechins, 4 theaflavins, and 2 purine alkaloids in a
large number of commercial teas extracted with hot water to simu-
late homeuse (Friedmanand others 2005). Other investigatorsused
a wide variety of extraction conditions, resulting in a wide variety
of measured concentrations of flavonoids and alkaloids from dry
tea leaves. Previous studies include the use of (a) boiling water for
3 min(DelRioand others2004); (b)boilingwaterfor 5 min(Khokhar
and Magnusdottir 2002; Bonoli and others 2003); (c) boiling water
for 10 min (Aucamp and others 2000); (d) water at 80 ◦C for 30 min
(Sakakibara and others 2003); (e) water at 90 ◦C for 30 min (Lee
and Ong 2000); (f ) acetonitrile/water for 1 h (Fernandez and others
2002);(g)ethanolatroomtemperature(Linandothers2003);(h)80%
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Efficient extraction of tea compounds . . .
methanol for3 h, then with 80%methanol containing 0.15%HCl for
3 h (Cabrera and others 2003); (i) 80% acetone for 2 wk (Menet and
others 2004); and (j) pressurized liquids (Pineiro and others 2004).
In the course of studies designed to relate tea and rice bran
flavonoids to anticarcinogenic and antimicrobial effects, we noted
thataqueousethanolefficientlyextracted flavonoids fromtea leaves
and dark rice brans (Friedman and others 2006; Nam and oth-
ers 2006). These observations suggested the need to better define
the potential of aqueous ethanol as an extraction solvent for tea
flavonoids andalkaloids.We therefore comparedlevelsof flavonoidsandalkaloidsextractedwithaqueousethanoltolevelsextractedwith
boiled water.
Themainobjectivesofthisstudywereto(a)simultaneouslydeter-
mine, by a previously validatedHPLC method (Friedmanand others
2005), levels of 14 tea catechins, theaflavins, and alkaloids in a sin-
gle analysis; (b) compare levels of tea constituents extracted with
ethanol/water to previously reported levels (except theophylline)
of water extracts of the same 77 teas; and (c) compare levels of
flavonoids andalkaloidsof 15greentea extracts (10capsules,1 gum,
and4 powders)sold at retail to theamountslisted on thelabels.The
results demonstrate the value of aqueous ethanol for the efficient
extraction of tea compounds, and the lack of correlation between
observedflavonoidcontentof thedietarysupplements andamountslisted on the labels.
Materials and Methods
MaterialsTeas were purchased as tea bags in local markets and restau-
rants and from the Stash Tea Co. (Portland, Oreg., U.S.A.). Di-
etary green tea supplements were obtained from local stores and
commercial companies. (−)-Epigallocatechin, (+)-catechin, (−)-
epicatechin, (−)-epigallocatechin gallate, (−)-gallocatechin gallate,
(−)-epicatechingallate,(−)-catechingallate,caffeine,theobromine,
and theophylline were obtained from Sigma-Aldlrich (St. Louis,
Mo., U.S.A.). Theaflavin, theaflavin-3-gallate, theaflavin-3-gallate,
and theaflavin-3, 3-digallate were obtained from Wako ChemicalCo. (Osaka, Japan). HPLC grade solvents were filtered through a
0.45-μM membrane (Millipore, Bedford, Mass., U.S.A.) and de-
gassed in an ultrasonic bath before use.
Extraction and analysis of commercial tea leaves andgreen tea dietary supplements
For extraction with 80% ethanol, each sample (approximately
1.5 g) was placed into a 250-mL flask equipped with a reflux con-
denser. This was followed by addition of 50 mL of a mixture of
ethanol: water (80:20, v/v). Each sample was then heated in a water
bath for 15 min at 60 ◦C, sonicated for 5 min, and then cooled. The
residue was extracted twice more with the same solvent. The com-
bined supernatants were then filtered through a 0.45-μm Milliporenylon filter.
For extraction with water (in this study, only theophylline in all
teas and in green tea products and catechins and alkaloids in green
tea dietary supplements were analyzed), each tea sample (approx-
imately 1.5 g) was placed into a 250-mL flask to which was added
250mL of water previously brought to theboiling point.The sample
was then stirred slowly with a magnetic stirrer for 5 min. The av-
erage temperature during the extraction, determined by measuring
the temperature of the water at 0, 1, 2, 3, 4, and 5 min intervals after
boiling,was approximately 90 ◦C. The cooledsample wasfiltered on
a 0.45 μm Millipore nylon filter before analysis.
The effect of the following variations to the cited conditions on
the efficiency of the extractions were also evaluated: (a) ethanol in
the aqueous-ethanol solvent: 10, 20, 40, 60, 80, or 95%; 60 ◦C for
15 min; and (b) time: 3, 5, 10, 15, or 20 min; 80% ethanol at 60 ◦C.
HPLC was carried out on a Hitachi liquid chromatograph model
665-II equipped with an Autosampler (model 655A-40, Hitachi Ltd.,
Tokyo,Japan).Thestainlesssteelcolumn(250mm×4.0mmi.d.)was
packed with Inertsil ODS-3v (5 μm particle diameter, GL Sciences,
Tokyo, Japan). The column temperature of 30 ◦C was maintained
witha Shimadzucolumn oven CTO-10vp(Shimadzu, Kyoto, Japan).
The gradient system consisted of a mixture of acetonitrile and 20
mMKH2PO4. The flow rate was1 mL/min. A Shimadzuphoto diodearrayUV-VISdetector(modelSPD-10Avp,Kyoto,Japan)was setfrom
200 to700 nm. The tea extract (10μL) wasinjected into thecolumn.
Separateanalyses,each intriplicate,werecarriedout with3 separate
extracts prepared from 3 different tea bags or green tea extracts for
each sample.
Theinitialcompositionofthemobilephase,consistingof7%(v/v)
solvent A (100%acetonitrile)and 93%of solvent B (20mM KH2PO4),
was maintained for 7 min. Solvent A was then increased linearly to
10% at 20 min, 15% at 25 min, 20% at 30 min, and 25% at 45 min to
70 min. Programming was then continued in the isocratic mode as
follows: 40% A at 70.1 to 75.0 min and 7% A at 75.1 to 90.1 min.
Spiking-extraction, linearity of concentration plots, and lim-
its of detection (LOD) were determined as described previously (Friedmanand others 2005). Thisreferencecontains values for these
parameters for 13 tea compounds, but not for theophylline. These
values for theophylline were determined in this study. Theophylline
eluted at approximately13 min, the concentration-response plot
was linear between 0 and 800 ng, LOD was 1.9 ng, and recovery
after spiking ranged from 95 and 107% of added sample. Recoveries
of catechins and alkaloidsfrom spiked green tea powders (capsules)
determined in this study ranged from 85% to 115%.
Statistical analysisThe square root or log transformation was used to stabilize the
variance prior to one-way analyses of variance (ANOVA) between
the 77 teas among the respective sums of 7 catechins, 4 theaflavins,
and 11 catechinsand theaflavins. Zeros were deleted from one-way
analyses (ANOVA) since they would result in a negative bias of the
error variance estimates. Dunnet’s one-tailed test was used to test
for decreases from the 10th highest ranked tea (SAS 2000).
Results and Discussion
Analytical aspectsThe previously validated HPLC-UV method for the analysis of the
compositionofaqueousteaextracts(Friedmanandothers2005)was
alsofoundto be effectivefor 80%ethanol/water extracts. Themobile
phase, consisting of mixturesof acetonitrileand 20 mM KH2PO4 and
programmed in linear/isocratic modes, separated, in a single run,
all 14 catechins, theaflavins, and alkaloids. The elution positions of a mixture of the 14 standardsand chromatograms of representative
black, green, pouching (oolong), and herbal teas as well as 2 green
tea extracts are shown in Figure 1. To our knowledge, this is the first
report on the simultaneous determination of these tea compounds
by HPLC.
We determined the effect of varying the ethanol concentration
from 10% to 95% during aqueous ethanol extraction at 60 ◦C on
the composition of a representative black and green teas. The data
(not shown) indicate that ethanol concentrations up to 80%did not
significantly affect the levels of extracted tea compounds. We also
noted that 80% ethanol/water evaporated at a faster rate than 20%
ethanol/water and that the amounts extracted with 95% ethanol
were lower than with the other ethanol/water mixtures.
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Efficient extraction of tea compounds . . .
Black Tea80% ethanol extract
Green Tea80% ethanol extract
0 20 40 60
Pouchong Tea80% ethanol extract
Herbal Tea80% ethanol extract
1
1
1
1 2
2
2
2
3
3
3
4
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4
6
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11 121314
5
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A b s o r b a n c e , 2 8 0 n m
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78
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Standards
0 20 40 60
Tea Capsule Hwater extract
1 2 3
4
65
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Tea Capsule H80% ethanol extract
1 2 3
4
65
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Tea Powder M
water extract
1 3
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89
10
Tea Powder M80% ethanol extract
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4
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Retention time (min)
Figure 1 --- HPLCchromatograms of amixture of 7 catechins, 4theaflavins, and 3 alkaloidstandards, selected teas,and green tea extracts.Peak 1, theobromine; 2,theophylline; 3,(−)-epigallocatechin; 4,caffeine; 5, catechin; 6,(+)-epicatechin; 7,(−)-epigallocatechingallate; 8, (−)-gallocatechingallate; 9, (−)-epicatechingallate; 10, (−)-catechingallate; 11, theaflavin; 12,theaflavin 3-gallate; 13,theaflavin 3-gallate; 14,theaflavin 3,3-digallate.
Additional studies also showed that varying the extraction time
from3to20minfor80%ethanolat60◦Calsodidnotsignificantlyin-
fluence the levelsof all tea compounds, with the possible exception
of epicatechin-3-gallate. Based on these observations and to avoid
evaporation of ethanol at higher temperaturesduring the workup of
the extracts, we selected 60 ◦C and 15 min as convenient standard
conditions for extractions with the 80% ethanol.
Composition of tea leavesLevels of individual catechins in teas extracted with 80%
ethanol or water. For the 77 teas evaluated in this study we use
samplenumbersbutnotteabrandnames.Thebrandnamesofthese
teas are listed in Friedman and others (2005). Table 1 compares the
composition of these teas after extraction with 80%ethanol at 65 ◦C
for 15 min to amounts extracted with boiled water for 5 min.
Forthe7individualteacatechins,theamountsextractedwith80%
ethanol are in most cases greater than the corresponding levels ex-
tracted with water. The differential trends in the amounts extracted
with the 2 solvents become more apparent for individual and to-
tal theaflavin and total flavonoid (catechin plus theaflavin) levels
outlined below.Levels of individual theaflavins in black teas. For the
theaflavins in black teas extracted with 80% ethanol, the levels (in
mg/g tea) for theaflavin (TF) ranged from 0.4 (#16) to 9.1 (#15) and
for the water extracts from 0 to 5.4 (#15). For theaflavin-3-gallate
(TF3G), the corresponding values are from 0 to 5.9 (#3) and 0 to 2.1(#23); for theaflavin-3-gallate (TF3G), from 0 to 3.8 (#18) and 0 to
0.8 (#21 and #30); and for theaflavin-3,3 -digallate (TF33G), from
1.8 (#28) to 10.9 (#30) and 0 to 6.4 (#31). Green teas contained no
theaflavins. Only 2 of the 14 specialty teas (#60 and #67) and one
of the 7 herbal teas (#74) contained theaflavins. The data show that
significantlygreateramounts of theaflavins were extractedwith 80%
ethanol than with water.Totallevelsofcatechinsandtheaflavins. Itisalsoinstructiveto
compare the trends in the sums of the concentrations of the 7 cate-
chins and4 theaflavins (seetotal FLAV columnin Table1), calculated
from theindividualvalues to thecorresponding sums present in the
water extracts of the same teas. For 32 black teas, the sum of the 11
catechins and theaflavins (in mg/g tea) extracted with 80% ethanol
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Efficient extraction of tea compounds . . .
ranged from 19.8 (#4) to 115.9 (#31) and for the water extracts, from
6.5 (#1) to 72.5 (#32). Most black teas contained both catechins and
theaflavins.
The sum of 7 catechins (total CATS column in Table 1) for the 32
black teas (in mg/g tea) extracted with 80%ethanol rangedfrom 9.6
(#3) to 111.0 (#29) and for water extracts, from 5.4 (#1) to 69.5 (#32).
For the sum of the 4 theaflavins (total TFS column in Table 1), the
valuesfor the80% ethanol extracts rangedfrom 3.7(#27) to 20.7 (#3)
and for the water extracts, from 0 to 8.8 (#18). Such high catechin
levels insomeof the black teas appear not to have been reported inthe published studies mentioned above.
The sum of 7 catechins for the 24 green teas (in mg/g dry tea)
extracted with 80%ethanol ranged from 12.3 (#1) to 136.3 (#56) and
for water extracts, from 4.4 (#33) to 100.0 (#56). The green teas con-
tained no theaflavins.
The sum of 7 catechins for the 14 specialty teas (in mg/g tea)
extracted with 80%ethanol ranged from 4.9 (#59) to 118.5 (#70) and
for the water extracts, from 3.4 (#57) to 83.1 (#70). The sum of 7
catechins for the 7 herbal teas (in mg/g tea) extracted with 80%
ethanol ranged from 0 to 46.0 (#77) and for the water extracts, from
1.2 (#71) to 26.4 (#77). The data show that greater total amounts of
flavonoids are extracted by 80% ethanol than by water.
A statistical profile using one-way analyses of variance (ANOVA,Dunnet’s one-tailed test) between 77 teas among the respective
sums of 7 catechins, 4 theaflavins, and 11 catechins and theaflavins
wasusedtodefineasubsetof10teascontainingthehighestamounts
of catechins and theaflavins extracted with both solvents. See foot-
note b to Table 1.
Factors that may affect extraction of tea compounds from
leaves. Extraction of the 7 catechins and 4 theaflavins with 80%
ethanol at 60 ◦C for 15 min was more effective than extracting with
water for 5 min at an average temperature of approximately 90 ◦C,
conditions used worldwide to prepare tea infusions. Both individ-
ual and total levels of catechins and theaflavins extracted with 80%
ethanol differed significantly from amounts extracted with water.
Possible reasons for these differences are not readily apparent, ex-
cept to suggest that geographical origin, soil composition, differ-
ences inthe compositionof different leaves,postharvest treatments,
and physical structure of thedifferent leavesmay influence thesus-
ceptibilities of dry tea leaves to extraction (Wang and others 2000;
Astill and others 2001; Lin and others 2003). It is also likely that
positively charged metal ions (minerals) also present in tea leaves
(Ferraraand others 2001)chemically chelate to phenolicOH groups
of flavonoids and that thefiber matrix of the leaves preferentially or
selectively binds or physically occludes some of the catechins and
theaflavins. Such physicochemical forces may make it more diffi-
cult to extract tea compounds from leaves. Still another possibility
is that levels of high-molecular weight theaflavins exceed solubili-
ties in water but not in theaqueous ethanol. Similar considerations
may govern the extraction of potato glycoalkaloids from leaves of the potato plant (Brown and others 1999).
As mentioned in the Introduction, to extract biologically active
compounds from tea leaves, other investigators used a wide range
of solvents and conditions. The previously reported levels of these
compounds also vary widely. The values we obtained with 80%
ethanol compare favorably with the highest levels reported in the
published studies. In addition,this is thefirst report on theanalysis
of all 14 tea compounds in a single HPLC run.
Purine (methylxanthine) tea alkaloids. Teas also contain 3
purine alkaloids: theobromine, theophylline, and caffeine. Table 1
compares the levels of these alkaloids after extraction with either
80% ethanol at 65 ◦C for 15 min to amounts extracted with boiled
waterfor 5 min. Belowwe compare thetrends in thelevels extracted
with the 2 solvents.
Thecaffeinecontent (inmg/g of tea) forblackteas extractedwith
80% ethanol ranged from 12.9 (#15) to 30.3 (#30) and the amounts
extracted with water, from 3.5 (#1) to 26.7 (#30). For green teas, the
corresponding ranges are from 0.5 (#33) to 26.8 (#51) and from 0 to
23.9 (#41); and for specialty teas, from 4.3 (#58) to 31.9 (#68) and 2.1
(#58) to29.7 (#67).Herbal teas contained noor low levelsof caffeine.
The theobromine content (in mg/g of tea) of all 77 teas extracted
with 80% ethanol ranged from 0.5 (#33) to 2.5 (#71) and with water,from 0 to 3.2 (#30). Theophylline levels ranged from 0 to 1.6 (#17)
for both extracts. Total alkaloid levels for all teas ranged from 0 to
32.7mg/gtea(#68).Mostpreviousstudiesdonotreporttheophylline
levelsof teas. Thestatisticalanalysismentioned earlier was also ap-
plied to caffeine and theobromine levels of the teas. See footnote
b in Table 1. The data show smaller differences in the amounts of
alkaloids extracted by the 2 solvents compared to much larger dif-
ferences for the flavonoids described earlier.
Composition of dietary green tea supplementsGeneral aspects. Although green tea extracts are widely used in
biomedicalstudies,therearefewpublishedstudiesontheactuallev-
els of tea flavonoids and alkaloids in green tea extracts sold at retailas capsules or powders as health-promoting dietary supplements
(neutraceuticals) (Laiand Roy 2004). Onesuch study (Manningand
Roberts 2003) of 7 commercial green tea products determined by
HPLCrevealed widevariability and muchloweramountsin thecon-
tent of 5 catechins (extracted with 80 ◦C water and allowed to steep
for 8 h) compared to claims on the labels. The authors recommend
thatthe phytochemicalcontent of suchdietary supplements should
be standardized so that consumers can make a rational choice.
To contribute to this effort, we determined the flavonoid and al-
kaloid content of 15 commercial green tea extracts sold as capsules
or powders. Table 2 lists these products and the compositional data
as listed on the labels. Table 3 compares the levels of 7 individual
catechins, their sums, levelsof the3 alkaloids, andtheir sums deter-
minedby HPLC with wateror 80%ethanolextracts.Forcapsules, we
also calculated the amounts per capsule listed in the last column of
the table. None of the samples contained theaflavins. What follows
is an attempt to relate our findings to the compositional data listed
on the labels.
Green tea gum and capsules. We determined the content of 7
catechins and 3 alkaloids in 1 product sold at retail as a gum and 10
products sold as capsules. The data in Table 3 show that (a) unlike
the results from tea leaves described earlier, the values determined
with the ethanolic extracts weregenerally only approximately 5% to
10% higher than the corresponding values for both individual and
total catechin levels obtained with the water extracts; (b) the total
catechin content of the gum (A in Table 2 and 3) of 10 mg/piece
is much lower than the 120 mg/piece listed on the label; (c) thetotal catechin content (in mg/g) of the capsules ranged from 41.6
(E in Table 3) to 379.9 (D); the corresponding range per capsule is
from 21.5 (C) to 176.1 (D); and(d) total catechin (polyphenol) levels
obtained in the present study are approximately 50% to 75% lower
than the values listed on the labels of these products.
All capsules also contained caffeine, theobromine, and theo-
phylline. Thedata show that (a) theamounts of individual andtotal
alkaloidsextracted withboth solvents did not differ significantly; (b)
values (in mg/g) for caffeine ranged from 16.7 (C) to 78.5 (F); and
(c) corresponding theobromine levels ranged from approximately
0.4 (C) to approximately 2.5 (G, K) and of theophylline levels, from
approximately 0.1 (C) to 2.2 (D). There is a 3-fold variation in the
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Efficient extraction of tea compounds . . .
Table 2 --- Commercial green tea extracts sold as capsules, gums, and powders
Product Name of product Label Size Comments from labels
A Mega-T dietary supplement,green tea chewing gum
120 mg 24 pieces Blend of green tea (leaf) powder, white tea (leaf) powder, andEGCG
B Green tea capsules 100 mg 60 capsules Each capsule contains green tea extract (leaf); 50%catechins (polyphenols)
C Green tea capsules 315 mg 90 capsules Green tea extract (leaf) = 14% polyphenols = 44 mgD White tea capsules 315 mg 90 capsules White leaf and flower extract. 90% polyphenols = 283.5 mgE Green tea capsules 100 mg 120 capsules Green tea extract, 100 mg; catechins (polyphenols), 50 mgF Green and white tea
capsules, organic
500 mg 60 Vcaps White peony and green sencha tea (leaf). Minimum 40%
polyphenols (200 mg), 3 to 6% theanine (15 to 30 mg), and5 to 9% caffeine (25 to 45 mg)
G Green extract capsules 315 mg 100 capsules Natural whole herb, Camellia sinensis ; each capsulecontains the polyphenol catechins of 3 cups of green teawith less than 1/5 caffeine of 1 cup (5 oz.)
H Green tea complex capsules 1000 mg 50 caplets Standardized green tea extract (leaves): 790 mg leaf extract(25% polyphenols, 8.5% EGCG, 5% caffeine) plus greentea powder (leaf), 210 mg
I Mega-T dietary supplementgreen tea
600 mg 30 caplets Metabolic support blend provides 90 mg EGCG and 50 mgcaffeine/capsule; contains green tea and several herbalextracts (fo ti root, gacinia fruit, guarana seed,bladderwrack kelp, and gotu kola whole plant)
J Green tea complex 1000 mg 60 caplets 790 mg green tea extract (Camellia sinensis ) (25%polyphenols, 8.5% EGCG, 5% caffeine); 210 mg green teapowder (Camellia sinensis) (leaf)
K Green tea extract 315 mg 100 capsules Natural whole herb; 2 capsules contain 630 mg green tea
extract (Camellia sinensis ) (aerial) (standardized to contain15% polyphenols, 95 mg)L Instant green tea beverage
mix2.2 g 32 tubes 300 mg of antioxidants per serving from fresh green tea
leavesM Green tea leaf-BRMa 5 g Powder Store at room temperatureN Green tea leaf-XRMa 5 g Powder Store at room temperatureO Green tea polyphenol 10 g Powder Storage: +4 ◦C
aThe characterization data of BRMsTM (Botanical reference material) from a specific genus and species of plant. XRMTM reference material comes with determinedvalues for their chemical composition and physical properties along with the methods used to obtain these values.
alkaloid levels among the capsules, with caffeine approximately 20
times greater than levels of theobromine and theophylline.
A possible reason why the amounts extracted with the 2 solvents
from both capsules and powders do not differ significantly may be
that we are dealing with catechins and alkaloids that have already
been extracted from tea leaves. Strictly speaking, the solvents do
not extract but rather dissolve the catechins from the matrices of
the commercial products. We do not know why catechin levels show
such wide variation among the capsules and why these levels differ
significantly from the amounts listed on the labels. Are catechins
degradedduringstorageby interactingchemically orphysically with
other capsuleconstituentssuch ascellulose,starch, andlactoseused
as fillers (excipients)? This aspect merits study.
Green tea powders. We also determined the catechin and alka-
loid levels of 4 commercial green tea powders. As is the case with
capsules, the amounts extracted with the 2 solvents tended to be
generally similar. Table 3 shows that the catechin levels (in mg/g)
for the 4 products ranged from 96.0 (L) to 696.9 (O), a 7.3-fold vari-
ation from highest to lowest value. Levels of alkaloids ranged fromapproximately 24 (L) to approximately 85 (N), a 3.5-fold variation.
The label on the tea beverage mix (L in Table 2) states that it pro-
vides 300 mg of antioxidants per serving of 2.2 g. The determined
total catechin amount of 206.5 mg per serving corresponds to 69%
of the amount shown on the label. The analytical data provided by
the supplier of the ChromaDex TM XRM powder (M) agree well with
total catechins we are reporting (52.5% for the 80% ethanol extract
and 49.4% for the water extract compared with 52.2% reported by
ChromaDex TM). However, individual catechin in the extracts deter-
mined in this study differed from the data on the label. We found
morethan twice the amount of (−)-epigallocatechin and about half
theamountof(+)-epicatechincompared to their analysis.Our anal-
ysis also revealed the presence of small amounts of gallocatechin-
3-gallate and catechin-3-gallate.
Conclusions
The results obtained in this study indicate that aqueous ethanol
is an excellent solvent for theextractionand analysis in a single
determination by HPLC of 7 tea catechins, 4 theaflavins, and3 alka-
loids from tea leaves. Extraction of tea compounds from the leaves
with80% ethanol at 60 ◦C was generally moreefficient thanreported
extraction of the same teas with hot water alone. The greater ex-
traction efficiency with aqueous ethanol seems to be influenced by
both thetypeof teaas wellas thechemicalstructure ofthe individual
flavonoids.Becausebiologicalpotenciesof individual teaflavonoids
vary widely (Cabrera and others 2003; Xu and others 2004; Cooper
and others 2005a, 2005b; Cushnie and Lamb 2005; Friedman and
others 2006), studies on the relationship between composition and
healtheffects of teas shouldevaluateboth water and ethanol/water
extracts. Thepossible variability in the composition of the same tea
brands originating fromdifferent retailers or tea batches also meritsfurther study.
Because theamountsof teacompounds in greentea dietarysup-
plements extractedwith the 2 solvents were significantly lower than
the amounts listed on the labels, our data suggest that consumers
could benefit by more accurate labeling of dietary supplements for
flavonoid(polyphenol) content.Moreover,because noneof theeval-
uated supplements contained beneficial theaflavins, there is a need
for new supplements containing both catechinsderived from green
teas and theaflavins derived from black teas.
Acknowledgment We thank Dr. Bruce E. Mackey for statistical analysis.
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Efficient extraction of tea compounds . . .
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