Studies on Inhibition Mechanism of Autoxidation by Tannins and Flavonoids: V: Radical-Scavenging Effects of Tannins and Related Polyphenols on l,l-Diphenyl-2-picrylhydrazyl Radical

Takashi Yoshida, Kazuko Mori, Tsutomu Hatano, Tomoko Okumura, Ikue Uehara, Keiko Komagoe, Takuo Okuda

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Radical scavenging effects of tannins and related polyphenols on l,l-diphenyl-2-picrylhydrazyl (DPPH) radical were evaluated by colorimetry. All of the polyphenols examined showed effects much stronger than that of a-tocopherol. The hydrolyzable tannins having galloyl groups in the molecule exhibited stronger effects than those having modified galloyl groups, such as hexahydroxydiphenoyl (HHDP), dehydrohexahydroxydiphenoyl (DHHDP) and chebuloyl groups. (-)-Epigallocatechin gallate, (-)-epigallocatechin, (-)-epicatechin gallate and methyl gallate also showed fairly significant effects, even though they are small molecules. The predominant reaction products upon the treatment of various alkyl gallates with DPPH radical on a preparative scale were dialkyl hexahydroxydiphenates, which should be formed by mutual coupling of C-centered galloyl radicals. Evidence for the formation of the alkyl gallate radicals was also obtained by the electron spin resonance spectroscopy.

Original languageEnglish
Pages (from-to)1919-1921
Number of pages3
JournalChemical and Pharmaceutical Bulletin
Issue number7
Publication statusPublished - 1989



  • alkyl gallate
  • dialkyl hexahydroxy-diphenate
  • hydrolyzable tannin
  • l-diphenyl-2-picrylhydrazyl
  • radical coupling
  • radical scavenger
  • tannin l

ASJC Scopus subject areas

  • Chemistry(all)
  • Drug Discovery

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