Indiosides G–K: Steroidal Glycosides with Cytotoxic and Anti-inflammatory Activities from Solanum violaceum

Five new steroidal glycosides (1–5) and nine known compounds were isolated from Solanum violaceum. Indiosides G (1) and H (2) are spirostene saponins with an iso-type F ring, indioside I (3) is a spirostane saponin, and indiosides J (4) and K (5) are unusual furostanol saponins with a deformed F ring. These structures represent rare naturally occurring steroidal skeletons. The structures of the new compounds were elucidated using 1D and 2D spectroscopic techniques and acid hydrolysis. Compounds 2, 3, and 7–9 exhibited cytotoxic activity against six human cancer cell lines (HepG2, Hep3B, A549, Ca9-22, MDA-MB-231, and MCF-7) with IC50 values of 1.83–8.04 μg/mL. Steroidal saponins 3, 8, and 9 showed inhibitory effects on superoxide anion generation with IC50 values of 2.84 ± 0.18, 0.62 ± 0.03, and 1.62 ± 0.59 μg/mL, respectively. Saponins 8 and 9 also inhibited elastase release with IC50 values of 111.05 ± 7.37 and 4.04 ± 0.51 μg/mL, respectively. Structure–activity relationship correlations of these compoun...