Free radical scavenging activity of the flavonoids isolated from Tecoma radicans

Successive extracts of aerial parts of Tecoma radicans, F. Bignoniaceae, showed free radical scavenging activity. Ethyl acetate extract produced maximum inhibition [97.8%] of DPPH using electron spin resonance [ESR] technique. Activity-guided fraction led to the isolation of the flavonoids. Five were identified as luteolin; quercetin 3-methyl ether; apigenin; 6-hydroxyluteolin and chrysoeriol. The most potent of them as free radical scavenger is quercetin 3-methyl ether 68.9%, then luteolin 39.4%