Three new compounds: 2R,3R-pterosin L 3-O-β-D-glucopyranoside (1), β-Dxylopyranosyl(1→2)-7-O-benzoyl-β-D- lucopyranoside (2) and 4-O-benzoyl-β-D-xylopyranosyl(1→2)-7-O-benzoyl-β-D-glucopyranoside (3), together with nine known compounds, were isolated from the ethyl acetate extract of Pteris ensiformis. 5-[2-Hydroxyethylidene]-2(5H)-uranone (4), which had been synthesized, was isolated from natural sources for the first time. The structures of all isolated compounds were determined on the basis of mass and spectroscopic evidence. Compound 1 and pterosin B (5) show cytotoxicity against HL 60 cells (human leukemia) with the IC50 values of 3.7 and 8.7 μg/mL, respectively.
