| Abstract
| - Flavonoids and hydrolyzable tannins isolated from Pelargonium reniforme were evaluated for theirantioxidant ability using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical generating system and aluminol-dependent chemiluminescence assay. In both assays, the polyphenols tested showed higherradical scavenging activities than the reference antioxidant, ascorbic acid (IC50 2.6−32.9 μM vs 40.9μM in the DPPH test, and 2−25 times stronger effects in the chemiluminescence assay). A comparisonof the flavonoids and the tannins showed that the latter have more potential than the former. Structuralrequirements for marked antioxidant activities of hydrolyzable tannins were the presence of galloyland hexahydroxydiphenoyl groups, and apparently carbonyl (ester) functionalities in oxidativelymodified dehydrohexa-hydroxydiphenoyl moieties. For flavonoids, it appeared that a catechol (3‘,4‘-dihydroxy) element in the B-ring were important determinants and that O-glycosides were moreeffective than flavone-based C-glucosyls. Conspicuously, introduction of a galloyl group significantlyenhanced their potentials. The demonstrated marked antioxidant effects of the polyphenols providea clue for beneficial effects of P. reniforme in the treatment of liver disorders among several ethnicgroups in areas of southern Africa. Keywords: Pelargonium reniforme; Geraniaceae; hydrolyzable tannins; flavonoids; 1,1-diphenyl-2-picrylhydrazyl; chemiluminescence; free radicals; antioxidant
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