Structural characteristics for superoxide anion radical scavenging and productive activities of green tea polyphenols including proanthocyanidin dimers.

The purpose of this paper is to report structural characteristics for superoxide anion radical (O(2(-))) scavenging and productive activities of green tea polyphenols. (-)-Epicatechin 3-O-gallate (5), (-)-epigallocatechin (6), (-)-epigallocatechin 3-O-gallate (7), (+)-gallocatechin-(4alpha-->8')-epigallocatechin (8), and (-)-epigallocatechin-(2beta-->O-->7', 4beta-->8')-epicatechin 3'-O-gallate (9) were isolated from the tea plant Camellia sinensis L. (+)-Epigallocatechin-(2beta-->O-->7, 4beta-->8')-epicatechin (10) was prepared by hydrolyzing 9. The polyphenols, as well as commercially available pyrogallol (1), methyl gallate (2), (+)-catechin (3), (-)-epicatechin (4), and the flavonol myricetin (11), produced O(2(-)) in descending order 1, 6 asymptotically equal to11 asymptotically equal to8, 7, 10, 2 asymptotically equal to9, 5 asymptotically equal to4. In the polyphenols with the pyrogallol-type B-ring and/or galloyl group, electron-withdrawing substituents (carbonyl and ketal carbons) and/or intramolecular hydrogen bonding constituted structural characteristics against the autoxidation reaction. The O(2(-))-productive activity partially counteracted O(2(-))-scavenging activity. However, such structural characteristics appeared to enhance the scavenging activity, accordingly the polyphenols in effect served as O(2(-))-scavengers in descending order 9 asymptotically equal to7, 2, 11, 8, 10, 3 asymptotically equal to4. On the other hand, 6, having no such structural characteristic, acted as a O(2(-))-generator, as well as 1. Further assessments covering tannins (e.g., A-type proanthocyanidin dimer 9) are needed to identify which green tea polyphenols are the most desirable chemopreventive agents.

Potential anthelmintics: polyphenols from the tea plant Camellia sinensis L. are lethally toxic to Caenorhabditis elegans.

A novel gallate of tannin, (-)-epigallocatechin-(2 beta-->O-->7',4 beta-->8')-epicatechin-3'-O-gallate (8), together with (-)-epicatechin-3-O-gallate (4), (-)-epigallocatechin (5), (-)-epigallocatechin-3-O-gallate (6), and (+)-gallocatechin-(4 alpha-->8')-epigallocatechin (7), were isolated from the tea plant Camellia sinensis (L.) O. Kuntze var. sinensis (cv., Yabukita). The structure of 8, including stereochemistry, was elucidated by spectroscopic methods and hydrolysis. The compounds, along with commercially available pyrogallol (1), (+)-catechin (2), and (-)-epicatechin (3), were examined for toxicity towards egg-bearing adults of Caenorhabditis elegans. The anthelmintic mebendazole (9) was used as a positive control. Neither 2 nor 3 were toxic but the other compounds were toxic in the descending order 8, 7 approximately 6, 9, 4, 5, 1. The LC(50) (96 h) values of 8 and 9 were evaluated as 49 and 334 micromol L(-1), respectively. These data show that many green tea polyphenols may be potential anthelmintics.