Synthesis, cytotoxicity and HQSAR study of amides-fused isosteviol derivatives as potential anti-colorectal cancer agents

A series of novel amide-fused isosteviol derivatives were designed and synthesized. Their cytotoxicities in vitro against HCT-116 cells were screened. The preliminary bioassays indicated that most of the title compounds exhibited noteworthy cytotoxicity. Especially, the compound 33 revealed the most potent inhibitory activity with IC50 value of 7.663 ± 0.211 μM. Based on these bioactivity data, hologram quantitative structure-activity relationship (HQSAR) was performed, and a statistically reliable model with good predictive power (r2 = 0.866, q2 = 0.662 and r2pred = 0.762) was achieved. In addition, the contribution maps derived from the optimal model explained the individual atomic contribution to the total activity of single molecule.

The Finally Rewarding Search for A Cytotoxic Isosteviol Derivative

Acid hydrolysis of stevioside resulted in a 63% yield of isosteviol (1), which served as a starting material for the preparation of numerous amides. These compounds were tested for cytotoxic activity, employing a panel of human tumor cell lines, and almost all amides were found to be non-cytotoxic. Only the combination of isosteviol, a (homo)-piperazinyl spacer and rhodamine B or rhodamine 101 unit proved to be particularly suitable. These spacered rhodamine conjugates exhibited cytotoxic activity in the sub-micromolar concentration range. In this regard, the homopiperazinyl-spacered derivatives were found to be better than those compounds with piperazinyl spacers, and rhodamine 101 conjugates were more cytotoxic than rhodamine B hybrids.