Spirostanol steroids from the roots of Allium tuberosum

•Six furostanol saponins, including three new ones were isolated from the roots of Allium tuberosum.•Three saponins exhibited potent antibacterial activities against Bacillus subtilis and Escherichia coli.•The relationship between the antibacterial activities and the structures of these saponins is described.

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.

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