Structures of two new oxidation products of green tea polyphenols generated by model tea fermentation

To clarify the oxidation mechanism of green tea catechins during tea fermentation, pure catechins were oxidized with a catechin-free homogenate of tea leaf. Oxidation of a mixture of (−)-epicatechin and (−)-epigallocatechin yielded a new metabolite, named dehydrotheaflavin, produced by the oxidation...

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Bibliographic Details
Published inTetrahedron Vol. 58; no. 43; pp. 8851 - 8856
Main Authors Tanaka, Takashi, Mine, Chie, Kouno, Isao
Format Journal Article
LanguageEnglish
Published OXFORD Elsevier Ltd 21.10.2002
Elsevier
Subjects
catechin
Chemistry
Chemistry, Organic
oxidation
Physical Sciences
polyphenol
Science & Technology
tea
theaflavin
oxidation
tea
catechin
polyphenol
theaflavin
PEROXYL RADICALS
INVITRO OXIDATION
TANNINS
ANTIOXIDANT CHEMISTRY
CATECHINS
THEAFLAVINS
BLACK TEA
(-)-EPIGALLOCATECHIN GALLATE
LEAF
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Summary:To clarify the oxidation mechanism of green tea catechins during tea fermentation, pure catechins were oxidized with a catechin-free homogenate of tea leaf. Oxidation of a mixture of (−)-epicatechin and (−)-epigallocatechin yielded a new metabolite, named dehydrotheaflavin, produced by the oxidation of a benzotropolone moiety of the black tea pigment theaflavin. Similar oxidation of a mixture of (−)-epicatechin and (−)-epigallocatechin 3- O-gallate afforded a new dimer of (−)-epigallocatechin 3- O-gallate, which was generated by the oxidation and cycloaddition of two pyrogallol rings. Structures were determined by spectroscopic method, and the oxidation mechanisms for the formation of the products were proposed. Graphic
ISSN:0040-4020
1464-5416
DOI:10.1016/S0040-4020(02)01061-X