Bioactive steroidal alkaloids from the fruits of Solanum nigrum

The investigation of the fruits of Solanum nigrum led to the isolation of four previously undescribed steroidal alkaloids, named solanine A, 7α-OH khasianine, 7α-OH solamargine and 7α-OH solasonine, together with six known ones. The structures of the isolated compounds were elucidated unambiguously by spectroscopic data analyses and chemical methods. Solanine A represents an unusual steroidal alkaloid with an unprecedented 6/5/6/5/5/6 hexacyclic ring system, and its structure was confirmed by X-ray single crystal diffraction analysis. Compounds 2-4 were rare naturally occurring steroidal alkaloid glycosides bearing a hydroxyl group at C-7 position. Solanine A showed the most potent inhibitory activity against the LPS-induced NO production in murine RAW264.7 macrophages with an IC₅₀ value of 3.85 ± 0.71 μM and significant cytotoxicity against MGC803, HepG2 and SW480 cancer cell lines with IC₅₀ values of 6.00 ± 0.52 μM, 9.25 ± 0.49 μM and 6.23 ± 0.26 μM, respectively.