Antioxidant properties of a novel flavonoid from leaves of Leucas aspera

The crude methanol extract of Leucas aspera leaves showed strong 1,1-diphenyl-2-picrylhydrazyl (DDPH) and superoxide radical-scavenging activities compared to other polarity-based extracted fractions. It was selected for purification of the bioactive compound. The activity-guided repeated fractionation of the methanol extract by silica gel column chromatography yielded a compound that exhibited strong antioxidant activity. Based on various physicochemical and spectroscopic analyses, e.g. UV, IR, 1H NMR, 13C NMR and mass spectroscopy, the bioactive compound isolated was elucidated as 5,7-dihydroxy-2-[14-methoxy-15-propyl phenyl]-4H-chromen-4-one (leucasin). Radical-scavenging potential and strong inhibition of lipid peroxidation in a liposome model were observed at a leucasin concentration of 40 ppm. These results demonstrate the antioxidant potency of leucasin which could be the basis for its alleged health-promoting potential.