Antioxidant properties of Thonningianin A, isolated from the African medicinal herb, 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 microM 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 microM, respectively. Furthermore, Th A showed inhibitory effects on the activity of xanthine oxidase with an IC50 of 30 microM. 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.
Gyamfi
Maxwell Afari
MA
Laboratory of Physiology and Pharmacology, Faculty of Medicine, School of Health Sciences, University of the Ryukyus, Nishihara, Okinawa, Japan.
Aniya
Yoko
Y
D000818:Animals; D000975:Antioxidants / Q000302:isolation & purification* / Q000494:pharmacology; D002614:Chelating Agents / Q000302:isolation & purification / Q000494:pharmacology; D004492:Edetic Acid / Q000737:chemistry; D005609:Free Radicals / Q000378:metabolism; D047348:Hydrolyzable Tannins; D015227:Lipid Peroxidation / Q000187:drug effects*; D008297:Male; D016488:Medicine, African Traditional; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D008968:Molecular Conformation; D010946:Plants, Medicinal / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013634:Tannins / Q000302:isolation & purification* / Q000494:pharmacology
D000975:Antioxidants; D002614:Chelating Agents; D005609:Free Radicals; D047348:Hydrolyzable Tannins; D017382:Reactive Oxygen Species; D013634:Tannins; C411320:thonningianin A; D004492:Edetic Acid