Free radicals produced by the oxidation of gallic acid and catechin derivatives

Gallic acid and catechin derivatives were oxidized in alkaline solution (pH 10.0-13.0) with K sub(3)[Fe(CN) sub(6)] under anaerobic conditions, and electron spin resonance (ESR) spectra of the radicals produced were measured. Gallic acid, epicatechin gallate. gallocatechin gallate. epigallocatechin,...

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Bibliographic Details
Published inJournal of wood science Vol. 50; no. 6; pp. 545 - 547
Main Authors Oniki, T. (Kyushu Dental Coll., Kitakyushu, Fukuoka (Japan)), Takahama, U
Format Journal Article
LanguageEnglish
Published Heidelberg Springer Nature B.V 01.11.2004
Subjects
Acids
Anaerobic conditions
ANTIOXIDANTS
CATECHIN
Derivatives
Electron paramagnetic resonance
Electron spin
ESR SPECTROSCOPY
FREE RADICALS
GALLATES
Gallic acid
Hyperfine structure
Oxidation
Potassium ferricyanide
Rings (mathematics)
Spin resonance
TANNINS
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Summary:Gallic acid and catechin derivatives were oxidized in alkaline solution (pH 10.0-13.0) with K sub(3)[Fe(CN) sub(6)] under anaerobic conditions, and electron spin resonance (ESR) spectra of the radicals produced were measured. Gallic acid, epicatechin gallate. gallocatechin gallate. epigallocatechin, and epigallocatechin gallate showed hyperfine structures. Gallic acid was found to be oxidatively C-O coupled in alkaline solution (pH 10.5-12.0). It was found that an unpaired electron delocalized over gallocatechin gallate and epigallocatechin molecules, but was localized on the galloyl group and the A-ring of epicatechin gallate and epigallocatechin gallate. The galloyl group of gallo-catechin gallate was readily alkalihydrolyzed but those of epicatechin gallate and epigallocatechin gallate were resistant to alkaline hydrolysis.
Bibliography:2005007696
K50
ISSN:1435-0211
1611-4663
DOI:10.1007/s10086-003-0591-1