Effects of substituents in the A-ring on the physiological activity of flavones

Abstract The flavonoids quercetagetin, gossypetin and scutellarein 7-glucoside which have o -dihydroxyl groups in the A ring inhibit indole-3-acetic acid oxidase. Since scutellarein 7-glucoside has no such grouping in the B-ring it is clear that it is the hydroxyls in the A-ring that cause the inhibition. The presence of o -dihydroxyls in the A-ring also decreases the inhibitory effect upon ATP formation in mitochondria.