Physachenolide C induces complete regression of established murine melanoma tumors via apoptosis and cell cycle arrest

•PCC and LG-134 had direct cytotoxicity in murine melanoma cell lines (IC50 values ranged from 0.19–1.8 µM).•PCC treatment induced apoptosis of tumor cells both in vitroand in vivo.•PCC treatment induced G0-G1 cell cycle arrest of melanoma cells.•PCC treatment caused complete regression of established melanoma tumors in all mice.•17β-hydroxywithanolides have the potential to improve melanoma therapeutic outcome.