Two new steroidal alkaloid saponins, solanigrosides Q and R (1 and 2), together with four known compounds khasianine (3), solamargine (4), solasonine (5), and soladulcoside A (6) were isolated from the whole plants of Solanum nigrum. The structures of new compounds (1 and 2) were determined by interpretation of HR-ESI-MS, 1D and 2D NMR spectra, and chemical transformation. Compound 4 exhibited potent cytotoxic activity against MDA-MB-231, A549, Hep3B, PC3 human cancer cell lines with IC50 values of 1.86 ± 0.45, 2.24 ± 0.15, 0.78 ± 0.11, 5.13 ± 1.34 μM, respectively. © 2018 Natural Product Incorporation.