期刊
CHEMICAL & PHARMACEUTICAL BULLETIN
卷 58, 期 1, 页码 98-102出版社
PHARMACEUTICAL SOC JAPAN
DOI: 10.1248/cpb.58.98
关键词
Camellia sinensis L.; catechin; A-type proanthocyanidin dimer; superoxide anion radical; scavenging activity
The purpose of this paper is to report structural characteristics for superoxide anion radical (02) scavenging and productive activities of green tea polyphenols. (-)-Epicatechin 3-O-gallate (5), (-)-epigallocatechin (6), (-)-epigallocatechin 3-O-gallate (7), (+)-gallocatechin-(4 alpha -> 8')-epigallocatechin (8), and (-)-epigallocatechin-(2 beta -> O ->', 4 beta -> 8')-epicatechin 3'-O-gailate (9) were isolated from the tea plant Camellia sinensis L. (+)-Epigallocatechin-(2 beta -> O -> 7, 4 beta -> 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 approximate to 11 approximate to 8, 7, 10, 2 approximate to 9, 5 approximate to 4. 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 approximate to 7, 2, 11, 89 10, 3 approximate to 4. 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.
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