Chemical constituents of Pteris excelsa and their antioxidant activity

Pteris excelsa Gaud. is a perennial evergreen herbaceous plant belonging to the Pteridaceae family. In the present study, the chemical constituents of this species were obtained by utilizing MCI, C18 and silica gel and Sephadex LH-20 gel column chromatography. A new flavonol glycoside was identified, kaempferol-4 ',7-dimethyl-3-O-beta-D-glucosyl-(1 -> 4)-alpha-L-rhamnoside (1), together with fourteen known compounds (2-15), kaempferol-4 '-methyl-3-O-beta-D-glucoside (2), kaempferol-4 ',7-dimethyl-3-O-glucoside (3), kaempferol-3-O-beta-D-glucoside (4), kaempferol-4 '-methyl-3,7-alpha-O-L-dirhamnoside (5), kaempferol-3,7-di-O-alpha-L-rhamnoside (6), pterosin B (7), 3 beta-hydrox-ycinnamolide (8), N-(3-carboxypropyl)-2-acetylpyrrole (9), vanillic acid (10), sauropunol C/D (11), 6-anhydro-2-deoxy-beta-O-furanosides (12), aquilegiolide (13), menisdaurilide (14), 2-(D-glycerol-1,2-dihydroxyethyl) furan (15). The structures of these compounds were established based on their high-resolution electrospray ionization mass spectrometry results and nuclear magnetic resonance spectroscopy data and by comparing their spectro-scopic data with those reported in the literature. Importantly, we found that the antioxidant activity of PE, EtOAc and n-BuOH fractions of 98% methanol extract of P. excelsa (mediated by scavenging free radicals) was 33.57 +/- 0.67%, 52.98 +/- 1.55% and 45.25 +/- 1.10% at a concentration of 400 mu g/mL, respectively. Besides, compounds 1-6 displayed an antioxidant effect against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical.