Antineoplastic agents .2. Four furostanol glycosides from rhizomes of Dioscorea collettii var. hypoglauca

During activity-guided fractionations to screen for antineoplastic agents, further studies by means of preparative HPLC led to the isolation of four known furostanol saponins: protoneodioscin, protodioscin, protoneogracillin, protogracillin, along with their corresponding artifacts: methyl protoneodioscin, methyl protodioscin, methyl protoneogracillin, and methyl protogracillin, from the rhizomes of Dioscorea collettii var. hypoglauca. Among them, protoneodioscin, protodioscin, and protoneogracillin are first reported from the title plant. The structures of the compounds were established on the basis of chemical evidence and spectral analysis (H-1-NMR, C-13-NMR, H-1-H-1 COSY, HMQC, HMBC, and FAB-MS). These eight compounds all caused morphological abnormality of Pyricularia oryzae mycelia. They also showed cytotoxic activities against the cancer cell line of K562 in vitro as antineoplastic agents.