期刊
BIOCHEMICAL PHARMACOLOGY
卷 63, 期 9, 页码 1725-1737出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/S0006-2952(02)00915-2
关键词
antioxidant; lipid peroxidation; reactive oxygen species; xanthine oxidase; electron spin resonance (ESR); medicinal herb; thonningianin A; Thonningia sanguinea
The antioxidant properties of Thonningianin A (Th A), an ellagitannin, isolated from the methanolic extract of the African medicinal herb, Thonningia sanguinea were studied using the NADPH and Fe2+/ascorbate-induced lipid peroxidation (LPO), electron spin resonance spectrometer and the deoxyribose assay. Th A at 10 muM inhibited both the NADPH and Fe2+/ascorbate-induced LPO in rat liver microsomes by 60% without inhibitory effects on cytochrome P450 activity. Th A was similar to the synthetic antioxidant, tannic acid, as an inhibitor of both the NADPH and Fe2+/ascorbate-induced LPO but potent than gallic acid, vitamin C and vitamin E. While Th A poorly scavenged the hydroxyl radical generated by the Fenton reaction it dose-dependently scavenged 1,1-diphenyl-2-picrylhydrazyl, superoxide anion and peroxyl radicals with IC50 of 7.5, 10 and 30 muM, respectively. Furthermore, Th A showed inhibitory effects on the activity of xanthine oxidase with an IC50 of 30 muM. In the deoxyribose assay both T. sanguinea and its methanolic component Th A showed only site-specific (Fe3+ + H2O2) but not non-site-specific (Fe3+ + EDTA + H2O2) hydroxyl radical scavenging suggesting chelating ability for iron ions. Spectroscopic studies showed that Th A enhanced absorbance in the visible region in the presence of Fe2+ ions. These results indicate that the antioxidant properties of Th A involve radical scavenging, anti-superoxide formation and metal chelation. (C) 2002 Elsevier Science Inc. All rights reserved.
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