A new macrocyclic flavonoid from Onychium japonicum

Seven compounds were isolated from Onychium japonicum by macroporous resin, silica gel, ODS, Sephadex LH-20 column chromatography and semi-preparative HPLC. Their structures were identified by NMR, MS and other spectroscopic methods as onychone A (1), quercetin (2), quercetin-3-O-α-L-rhamnoside (3), kaempferol-7-O-β-D-glucopyranoside (4), kaempferol-3-O-α-L-rhamnopyranoside (5), (-)-prunin (6), and norathyriol (7). Compound 1 is a novel macrocyclic flavonoid, and all the others are reported from this plant for the first time. In vitro cytotoxic activities of compounds 1-7 were evaluated by MTS testing with five cancer cell lines. Compound 7 exhibited weak cytotoxicity against tumor cell lines A549, SMMC-7721, and SW480.