Design, synthesis and in vitrocytotoxicity evaluation of indolo–pyrazoles grafted with thiazolidinone as tubulin polymerization inhibitorsElectronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d2md00442a

In the pursuit of potential and effective chemotherapeutic agents, a series of 2-((3-(indol-3-yl)-pyrazol-5-yl)imino)thiazolidin-4-ones was designed and synthesized, conjoining salient pharmacophoric properties for directing prominent cytotoxicity. The in vitrocytotoxicity evaluation revealed potent compounds with IC50values <10 μM on tested human cancer cell lines. Compound 6cexhibited the highest cytotoxicity with an IC50value of 3.46 μM against melanoma cancer cells (SK-MEL-28) and was highly cytospecific and selective towards cancer cells. The traditional apoptosis assays revealed morphological and nuclear alterations such as apoptotic body formation, condensed/horseshoe-shaped/fragmented/blebbing nuclei, and the generation of ROS. Flow cytometric analysis revealed effective early-stage apoptosis induction and cell-cycle arrest in the G2/M phase. In addition, the enzyme-based effect of 6con tubulin showed the inhibition of tubulin polymerization (about 60% inhibition, IC50was <1.73 μM). Moreover, molecular modeling studies affirmed the constant accommodation of compound 6cat the active pocket of tubulin, establishing many electrostatic and hydrophobic interactions with the active pocket's residues. The tubulin-6ccomplex was stable during the MD simulation for 50 ns with the recommended range of RMSD value (2–4 Å) for each pose.