Purification, antitumor activity in vitro of steroidal glycoalkaloids from black nightshade (Solanum nigrum L.)

• Six steroidal glycoalkaloids (1–6) were isolated from Solanum nigrum L.
• Compounds 1, 2, 3 and 6 showed cytotoxicity against the MGC-803.
• Compounds with rhamnose at C-2 or hydroxyl on steroidal backbone have high activity.
• Compound 3 induced S phase arrest and apoptosis.
• Apoptosis is related to the expression of Bax, Bcl-2, mutant p53 and caspase-3.

Six steroidal glycoalkaloids (1–6) were isolated and purified from Solanum nigrum L. (SNL) by acid extraction and alkaline precipitation, various chromatographic techniques, and their structures were elucidated by spectroscopic data. Antitumor activity, structure–activity and its molecular mechanism were investigated by methyl thiazolyl tetrazolium (MTT) method, flow cytometry, colorimetric assay and an immunocytochemical method. Experimental results showed that compounds 1 (solasonine), 2 (β1-solasonine), 3 (solamargine) and 6 (solanigroside P) have cytotoxicity to MGC-803 cells. Compounds with three sugar units and a-l-rhamnopyranose at C-2 or a hydroxyl group on the steroidal backbone may be potential candidates for the treatment of gastric cancer. The mechanism of action may be related to the decrease of mutation p53, the increase of the ratio of Bax to Bcl-2 and the activation of caspase-3 to induce apoptosis.