Tannins and Related Compounds. CXIV. Structure of Novel Fermentation Products, Theogallinin, Theaflavonin and Desgalloyl Theaflavonin from Black Tea, and Changes of Tea Leaf Polyphenols during Fermentation

Abstract

Continuing chemical examination of black tea has led to the isolation of three novel fermentation products, theogallinin (1), theaflavonin (10) and desgalloyl theaflavonin (11). The structure of 1 was established on the basis of physico-chemical evidence to be a condensation product linked through pyrogallol-pyrogallol rings in theogallin (2) and (-)-epigallocatechin 3-O-gallate (3), while 10 and 11 were characterized as B, B'-linked bisflavonoids formed by an oxidative coupling of isomyricitrin (12) and tea catechins [3 and (-)-epigallocatechin (4)]. Furthermore, high performance liquid chromatography analyses of the changes of tea polyphenols during fermentation have revealed that original tea catechins are more rapidly transformed by endogenous phenol oxidase to theasinensins (e.g.6, 8) and oolongtheanin (13) than the formerly known black tea pigments, theafiavins.