The superoxide anions scavenging activity and antioxidation of seven flavonoids-quercetin, rutin, morin, acacetin, hispidulin, hesperidin, and naringin-were studied. The superoxide anions were generated in a phemazin methosulphate-NADH system and were assayed by reduction of nitroblue tetrazolium. The scavenging activity ranked: rutin was the strongest, and quercetin and naringin the second, while morin and hispidulin were very weak. The concentration values yielding 50% inhibition of lipid peroxidation in mouse liver homogenate were in order of 10-6 M for quercetin, rutin, and morin; and of 10-5 M for acacetin and hispidulin, while naringin and hesperidin had no antioxidative action. In comparison with the antioxidative and scavenging activities of flavonoids, there are no correlations. © 1990.