Cytotoxic steroidal saponins from Panicum turgidum Forssk

- Seven steroidal saponins were isolated from Panicum turgidum.
- Three bidesmosidic cholestane-type and one spirostane-type steroidal glycosides were found new.
- Spirostane-type steroidal glycosides showed cytotoxicity.

Three new bidesmosidic cholestane-type steroidal glycosides, 16-O-β-d-glucopyranosyl-cholest-5-en-3β,16β-diol-22-one-3-O-α-l-rhamnopyranosyl-(1 → 2)-O-[(β-d-glucopyranosyl(1 → 4)]-O-β-d-glucopyranoside (1), 16-O-β-d-glucopyranosylcholest-5-en-3β,16β-diol-22-one-3-O-α-l-rhamnopyranosyl-(1 → 2)-O-β-d-glucopyranoside (2), and 16-O-β-d-glucopyranosylcholestan-3β,16β-diol-6,22-dione-3-O-α-l-rhamnopyranosyl-(1 → 2)-O-β-d-glucopyranoside (3) were isolated from a methanolic extract of Panicum turgidum. In addition four known compounds, pennogenin 3β-O-α-l-rhamnopyranosyl-(1 → 2)-O-[α-l-rhamnopyranosyl-(1 → 4)-O-α-l-rhamnopyranosyl-(1 → 4)]-O-β-d-glucopyranoside (4), yamogenin 3β-O-α-l-rhamnopyranosyl-(1 → 2)-O-[α-l-rhamnopyranosyl-(1 → 4)]-O-β-d-glucopyranoside (5), yamogenin 3β-O-α-l-rhamnopyranosyl-(1 → 2)-O-[α-l-rhamnopyranosyl-(1 → 4)-O-α-l-rhamnopyranosyl-(1 → 4)]-O-β-d-glucopyranoside (6), and pennogenin 3β-O-α-l-rhamnopyranosyl-(1 → 2)-O-[α-l-rhamnopyranosyl-(1 → 4)]-O-β-d-glucopyranoside (7) were also isolated and characterized. Their structures were established using extensive spectroscopic methods including 1D and 2D NMR and HRESIMS. The isolated compounds were screened for cytotoxicity towards a panel of mammalian cell lines and 4-7 were found to be cytotoxic.

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