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Department of Biochemistry and
*
Department of Physiology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, The Peoples Republic of China and
Institute of Materia Medica, Chinese Academy of Medical Sciences, Beijing, The Peoples Republic of China
2To whom correspondence should be addressed. E-mail: zhenyuchen{at}cuhk.edu.hk.
Green tea catechins, including (-)-epicatechin (EC), (-)-epicatechin
gallate (ECG), (-)-epigallocatechin (EGC) and (-)-epigallocatechin
gallate (EGCG), are oxidized and dimerized during the manufacture of
black tea and oolong tea to form orange-red pigments, theaflavins
(TF), a mixture of theaflavin (TF1), theaflavin-3-gallate
(TF2A), theaflavin-3'-gallate (TF2B) and
theaflavin-3,3'-digallate (TF3). The present study was
designed to compare the antioxidant activities of individual TF with
that of each catechin using human LDL oxidation as a model. All
catechins and TF tested inhibited Cu+2-mediated LDL
oxidation. Analysis of the thiobarbituric acidreactive substances
(TBARS) and conjugated dienes produced during LDL oxidation revealed
that the antioxidant activity was in the order: TF3 > ECG > EGCG
TF2B
TF2A
> TF1
EC > EGC. Four TF derivatives
also demonstrated a dose-dependent antioxidant activity in
Cu+2-mediated LDL oxidation at concentrations of 540
µmol/L. These results demonstrate that the TF present
in black tea possess at least the same antioxidant potency as catechins
present in green tea, and that the conversion of catechins to TF during
fermentation in making black tea does not alter significantly their
free radicalscavenging activity.
KEY WORDS: black tea catechins green tea low density lipoprotein oxidation theaflavins.
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