Attachment of rhamnosyl glucoside on quercetin confers potent iron-chelating ability on its antioxidant properties

The pharmacological essence of the natural addition of rhamnosyl glucoside on quercetin that is commonly found in nature in medicinal plants is rather obscure. The present study therefore sought to compare the antioxidant activities of both compounds by comparing their ability to decolourise DPPH radicals, reduce Fe3+, chelate Fe2+, prevent deoxyribose degradation and inhibit hepatic thiobarbituric acid reactive substances induced by both Fe2+ and sodium nitroprusside. The results show that quercetin is generally a more potent antioxidant than its rhamnosyl glucoside derivative (rutin). However, rutin exerted a more potent iron-chelating ability than quercetin which diminishes in a time dependent fashion suggesting why it exhibited a reduced inhibitory effect on lipid peroxidation and deoxyribose degradation under harsh prooxidant assault than quercetin. Taken together, we speculate that rutin may have been produced initially in plants as a possible defense mechanism for protection and survival under oxidative assaults and where both flavonoids are found to co-exist in nature, there is a possible synergy in their antioxidant actions.