Novel spirooxindole-triazole derivatives: unveiling [3+2] cycloaddition reactivity through molecular electron density theory and investigating their potential cytotoxicity against HepG2 and MDA-MB-231 cell lines

A novel analogue of hybrid spirooxindoles was synthesized employing a systematic multistep synthetic approach. The synthetic protocol was designed to obtain a series of spirooxindole derivatives incorporating triazolyl-<i>s</i>-triazine framework via [3 + 2] cycloaddition (32CA) reaction of azomethine ylide (<b>AY)</b> with the corresponding chalcones <b>(6a-d)</b>. Unexpectedly, the reaction underwent an alternate route, leading to the cleavage of the s-triazine moiety and yielding a series of spirooxindole derivatives incorporating a triazole motif. A comprehensive investigation of the 32CA reaction mechanism was conducted using Molecular Electron Density Theory (MEDT). The viability of all compounds was evaluated through an MTT assay, and the IC₅₀ values were determined using Prism Software. The antiproliferative efficacy of the synthesized chalcones and the corresponding spirooxindole derivatives was assessed against two cancer cell lines: MDA-MB-231 (triple-negative breast cancer) and HepG2 (human hepatoma). These findings were compared with Sorafenib, which was used as a positive control. The results revealed that chalcones <b>(6c</b> and <b>6d)</b> were the most active among the tested chalcones, with IC₅₀ values of 7.2 ± 0.56 and 7.5 ± 0.281 µM for <b>(6c)</b> and of 11.1 ± 0.37 and 11.0 ± 0.282 µM for <b>(6d)</b>, against MDA-MB-231 and HepG2, respectively. Spirooxindoles <b>(9b, 9c, 9h,</b> and <b>9i)</b> exhibited the highest activity with IC₅₀ values ranging from 16.8 ± 0.37 µM to 31.3 ± 0.86 µM against MDA-MB-231 and 13.5 ± 0.92 µM to 24.2 ± 0.21 µM against HepG2. In particular, spirooxindole derivatives incorporating 2,4-dichlorophenyl moiety were the most active, with an IC₅₀ of 16.8 ± 0.37 µM for <b>(9h)</b> against MDA-MB-23 and 13.5 ± 0.92 µM for <b>(9i)</b> against HepG2. Interestingly, the IC₅₀ of compound <b>(6c)</b> (7.2 µM) exhibited better activity than that of Sorafenib (positive control) (9.98 µM) against MDA-MB-231. Molecular docking, ADMET, and molecular dynamic simulations were conducted for the promising candidates (<b>6b, 6c,</b> and <b>9h)</b> to explore their binding affinity in the EGFR active site.