Ru(II)-Arene Complexes of Pyrazole-Based Acylthiourea for Anticancer Application against Ovarian Cancer Cell Lines: Effect of Arene, Halido, and Acylthiourea Ligands

Abstract

A series of acylthiourea ligands (L) with variations at the C-terminal (thiophenyl or methylene-thiophenyl) by incorporating an N-substituted pyrazole and their Ru(II)-arene complexes [(arene)Ru(L)(X)₂] (arene = p-cymene/benzene; X = chlorido (Cl)/iodido (I)) were synthesized and characterized using UV–vis, FT-IR, ¹H NMR and ¹³C NMR spectroscopy, HRMS, and single crystal X-ray diffraction. DFT studies provided optimized geometries and electronic structures of the complexes, and molecular docking was performed with B-cell lymphoma 2 (Bcl-2) protein and DNA to assess their binding interactions. In vitro cytotoxicity of the ligands and complexes was evaluated against ovarian cancer cell lines (A2780 and cisplatin-resistant A2780). Complexes C3, C4, and C6 exhibited significant cytotoxic activity, with IC₅₀ values lower than those of the precursors and cisplatin. Further studies using AO/EB staining, Hoechst staining, JC-1 assay, and flow cytometry indicated that these complexes could exhibit enabled apoptosis through mitochondrial dysfunction. The studies proved that the introduction of a methylene group in the ligand or varying arene/halido had a significant influence over cytotoxicity. Notably, the benzene complexes showed enhanced anticancer activity compared to their p-cymene counterparts. The most active complex, C3, also oxidized GSH to GSSG, suggesting a mechanism involving oxidative stress induction.