Free radical scavenging and antioxidant activity of 5,7,3′,4′-hydroxy-substituted flavonoids

Abstract

The antioxidant efficiencies of 5,7,3′,4′-hydroxy-substituted flavonoids were examined. The tested compounds (quercetin, luteolin , taxifolin , (+)-catechin and eriodictyol) were selected with a view to their C-ring differentiated pattern. Each one was added in cottonseed oil at equimolar amounts and the retardation of lipid peroxidation was estimated by means of peroxide value . Furthermore, their ability to scavenge DPPH radical was studied in two solvents (methanol and ethyl acetate) and the DPPH method proved a satisfactory prediction test for the antioxidant action of flavonoids in oils when methanol was used as the reaction media. Furthermore, the comparison of the C-ring structural element contribution to the antioxidant action revealed the full substitution to be the most important followed by the 3-OH and 2,3-double bond in the presence of the 4-carbonyl. Concerning the monosubstituted flavonoids , the 4-carbonyl group induced minor activity, whereas the 3-OH increased significantly the antiradical and antioxidant action.