Antioxidant activity of Artemisia capillaris Thunberg

In our continuous study on antioxidant activities of natural resources, the solvent extracts of Artemisia capillaris Thunb. were evaluated for their potential to scavenge 1,1-diphenylpicrylhydrazyl (DPPH) free radical and authentic peroxynitrite (ONOO-), and inhibit ONOO- generation from 3-morpholinosydnomimine (SIN-1). Methanol (MeOH) extract showed relatively strong antioxidant activity, while dichloromethane (CH2Cl2) extract showed marginal activity in DPPH system. MeOH and CH2Cl2 extracts were combined and fractionated with n-hexane, 85% aqueous MeOH, and n-butanol (n-BuOH). n-BuOH soluble fraction exhibiting most potent antioxidant activity in DPPH and authentic ONOO- model systems was further purified by repeated silica gel column chromatography and RP-HPLC to give 3,4-dicaffeoylquinic acid (1). Structure of isolated compound 1 was elucidated by extensive 2D NMR experiments, H-1 COSY, NOESY, HSQC, and HMBC, and through comparison with published spectral data.