Antioxidant properties of a novel flavonoid from leaves of Leucas aspera

摘要

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, ~(13)C 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.