Superoxide radical scavenging properties of extracts and flavonoids isolated from the leaves of Blumea balsamifera

In view of the pharmacological interest in flavonoids, the superoxide radical scavenging capacity of pet-ether, chloroform, and methanol extracts and flavonoids of Blumea balsamifera DC leaves on nonenzymatically (phenazine methosulfate/NADH) generated superoxide radicals were evaluated. The methanol extract (93.91 +/- 1.37%) exhibited higher radical scavenging activity than the chloroform extract (84.58 +/- 1.51%). The pet-ether extract was inactive toward nonenzymatically generated superoxide radicals. The superoxide radical scavenging capacity of flavonoids (100 muM) as determined was decreased in the order quercetin > luteolin > 5,7, 3',5'-tetrahydroxyflavanone > blumeatin > rhamnetin > tamarixetin > luteolin-7-methyl ether > dihydroquercetin-4'-methyl ether > dihydroquercetin-4',7-dimethyl ether. It was concluded that flavonoids with a free hydroxyl group were more active than methylated compounds and that the flavonoid content of extracts contributed to their superoxide radical scavenging activity.