Structure-based design, synthesis, and biological evaluation of withaferin A-analogues as potent apoptotic inducers.

Apoptosis inducers represent an attractive approach for the discovery and development of anticancer agents. Herein, we report on the development by molecular fine tuning of a withaferin A-based library of 63 compounds (2–64), 53 of them reported for the first time. Their antiproliferative evaluation on HeLa, A-549 and MCF-7 human tumor cell lines identified fifteen analogues displaying higher activity (IC50 values ranging 0.3–4.8 μM) than the lead (IC50 values ranging 1.3–10.1 μM) either in lag or log growth phases. SAR analysis revealed that acylation enhances cytotoxicity, suggesting the hydrophobic moiety contributes to the activity, presumably by increasing affinity and/or cell membrane permeability. Further investigation clearly indicated that compounds 3, 11, 12, and 18 induce apoptosis evidenced by chromatin condensation, phosphatidylserine externalization, and caspase-3 activation effects on HeLa cells. The potent capacity to induce apoptosis with concomitant cell loss in G2/M highlights the potential of 27-benzyl analogue (18) as an apoptotic inducer drug candidate.