Synthesis and cytotoxic activity of nitric oxide-releasing isosteviol derivatives

Fifteen novel hybrids containing diterpene skeleton and nitric oxide (NO) donor were prepared from isosteviol. All the compounds were tested on preliminary cytotoxicity, and the results showed that six target compounds (8c, 10b, 14a, 14c, 18c, and 18d) exhibited anti-proliferation activity on HepG2 cells, with 8c (IC50 = 4.24 μM) and 18d (IC50 = 2.75 μM) superior to the positive control CDDO-Me (2-cyano-3,12-dioxooleana-1,9(11)-dien-28-acid methyl ester, IC50 = 4.99 μM); eleven target compounds (8a-c, 9a-c, 10a-b, 14a, 14c, 18d) exhibited anti-proliferation activities on B16F10 cells at different levels, among them, seven compounds were more potent than comptothecin (IC50 = 2.78 μM) and CDDO-Me (IC50 = 5.85 μM), particularly, 10b (IC50 = 0.02 μM) presented the strongest effect, which was selected as a candidate for further study.