Identification of a flavonoid C-glycoside as potent antioxidant.

Flavonoids have been documented to have good antioxidant activities in vitro . However, reports on the cellular antioxidant activities of flavonoid C -glycosides are very limited. In this work, an apigenin C -glycoside was purified from Artocarpus heterophyllus by column chromatography and was identified to be 2″- O - β -D-xylosylvitexin by nuclear magnetic resonance spectroscopy. The cellular antioxidant activity and anticancer activity of 2″- O - β -D-xylosylvitexin were evaluated for the first time. The quantitative structure-activity relationship was analysed by molecular modeling. Apigenin presented an unexpected cellular antioxidation behaviour. It had an antioxidant activity at low concentration and a prooxidant activity at high concentration, whereas 2″- O - β -D-xylosylvitexin showed a dose-dependent cellular antioxidant activity. It indicated that C-glycosidation improved the cellular antioxidation performance of apigenin and eliminated the prooxidant effect. The ortho -dihydroxyl at C -3′/ C -4′ and C -3 hydroxyl in the flavonoid skeleton play important roles in the antioxidation behaviour. The cell proliferation assay revealed a low cytotoxicity of 2″- O - β -D-xylosylvitexin. [ABSTRACT FROM AUTHOR]