Antioxidant and radical--scavenging activity of flavonoids from {\sl Solidago canadensis}

OBJECTIVE To investigate the flavonoids of an exotic herb,Solidago canadensis.METHODS The compounds were separated by different chromatographies and the structures were determined mainly by means of MS and NMR techniques;antioxidant and radical-scaveging activity of all the isolated compounds were evaluated by DPPH radical-scavenging assay.RESULTS Nine flavonoids were obtained from the methyl extract of S.canadensis and determined as quercetin(1),3-methoxy-quercetin(2),quercetin-3-O-β-D-glucopyranoside(3),quercetin-3-O-α-L-rhamopyranoside(4),rutin(5),kaempferol(6),kaempferol-3-O-β-D-glucopranoside(7),kaempferol-3-O-α-L-rhamopyranoside(8) and kaempferol-3-O-rutinnoside(9),respectively.DPPH radical-scavenging assay displayed that compound(1) owned the most strong activity,compared to the positive control of Vit C.Compound(2) and(3) showed moderate activity while compound(4()～()9) exhibited more weaker activity than that of Vit C.CONCLUSION Compound 2,4,8 and 9 are isolated in this plant for the first time.The flavonoids from S.canadensis possesses pretty strong activity of antioxidant and radical-scavenging and the relationships between the molecular structures and activity are also discussed.