New constituents from Crinum latifolium with inhibitory effects against tube-like formation of human umbilical venous endothelial cells

Six compounds (1-6) were isolated from the methanol extract of Crinum latifolium by bioassay-guided separation. Among the six isolates, compounds 2 and 6 were new metabolites. Their structures were established as 4-senecioyloxymethyl-3,4-dimethoxycoumarin (2) and 5,6,3'-trihydroxy-7,8,4'-trimethoxyflavone (6) based on spectroscopic analyses. Compound 2 was found to be strongly inhibitory against the in vitro tube-like formation of human umbilical venous endothelial cells (HUVECs) while manifesting no cytotoxicity in tumor cell lines (B16F10, HCT116). Significant inhibitory activity (inhibition percentage, 53.5%) was still observed at concentrations as low as 1 mug/mL. Compound 6 showed a modest inhibitory effect on the tube-like formation of HUVECs. Other compounds, including cycloartenol (1), 4',7-dihydroxy-3'-methoxyflavan (3), 4',7-dihydroxyflavan (4), and 2',4',7-trihydroxydihydrochalcone (5) were found to be nearly inactive.