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Paper | Regular issue | Vol 63, No. 7, 2004, pp.1547-1554
Published online, 23rd April, 2004
DOI: 10.3987/COM-04-10039
Characterization of the Oxidation Products of (-)-Epigallocatechin Gallate, a Bioactive Tea Polyphenol, on Incubation in Neutral Solution

Tsutomu Hatano,* Mami Hori, Miwako Kusuda, Takayo Ohyabu, Hideyuki Ito, and Takashi Yoshida

*Faculty of Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-Naka, Okayama 700-8530, Japan

Abstract

(-)-Epigallocatechin gallate (EGCG) (1) changes rapidly into various products in neutral solution containing trace amounts of metal ions as catalysts. In addition to theasinensins A (2) and D (3), (-)-gallocatechin gallate (4), and gallic acid, five products were isolated from a reaction mixture resulting from the incubation of 1. MS and NMR spectroscopic analyses of the products revealed two monomeric [EGCG-MOx-M1 (5) and M2 (6)], and three dimeric [EGCG-MOx-D1 (7), D2 (8) and D3 (9)] structures.