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

Chem Pharm Bull (Tokyo). 2010 Jan;58(1):98-102. doi: 10.1248/cpb.58.98.

Abstract

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.

MeSH terms

  • Camellia sinensis / chemistry*
  • Catechin / chemistry*
  • Catechin / isolation & purification
  • Flavonoids / chemistry*
  • Flavonoids / isolation & purification
  • Free Radical Scavengers / chemistry*
  • Free Radical Scavengers / isolation & purification
  • Models, Molecular
  • Molecular Structure
  • Phenols / chemistry*
  • Phenols / isolation & purification
  • Polyphenols
  • Proanthocyanidins / chemistry*
  • Proanthocyanidins / isolation & purification
  • Superoxides / chemistry
  • Tea / chemistry*

Substances

  • Flavonoids
  • Free Radical Scavengers
  • Phenols
  • Polyphenols
  • Proanthocyanidins
  • Tea
  • Superoxides
  • proanthocyanidin
  • Catechin