Spirostanol steroids from the roots of Allium tuberosum

Three new spirostanol saponins named tuberosines A-C (1-3), together with three known ones tuberoside O (4), 25(S)-Schidigera-saponin D5 (5), and shatavarin IV (6) were isolated from the roots of Allium tuberosum. Their structures were established on the basis of extensive spectroscopic analyses. Whereas compounds 5 and 6 exhibited potent antibacterial activities against Bacillus subtilis (32 μg/mL) and Escherichia coli (16 μg/mL), the new saponin 2 showed only moderate antibacterial activities against these pathogens. The relationship between the antibacterial activities and the structures of these saponins are described.