Six unprecedented steroidal glycosides from Allium atropurpureum bulbs and their cytotoxicities against SBC-3 human small-cell lung cancer cells

Nine steroidal glycosides (1−9) comprising five furostanol glycosides (1−3, 5, and 7), a pseudofurostanol glycoside (4), and three spirostanol glycosides (6, 8, and 9) were isolated from Allium atropurpureum bulbs. The structures of unprecedented compounds (1−6) were determined mainly by two-dimensional NMR spectroscopy and hydrolysis studies. The cytotoxicities of 1−9 and the corresponding spirostanol derivative (3a) of 3 were evaluated in SBC-3 human small-cell lung cancer cells using a modified 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2-tetrazolium bromide (MTT) assay. Compounds 3, 7−9, and 3a were determined to be moderately cytotoxic toward SBC-3 cells, with IC50 values in the 1.4−6.0 µM range.