Palladium(II) complex bearing benzothiazole based O,N,S donor pincer ligand: Study of in-vitro cytotoxicity, interaction with CT-DNA and BSA protein

A new palladium(II) complex, [Pd(LS^Et)Cl] (C1) with benzothiazole based ONS donor pincer ligand (HLS^Et) was synthesized (where, HLS^Et = 2-(benzothiazol-2-yl)-6-(((2-(ethylthio)phenyl)imino)methyl)phenol). Interaction of C1 with CT DNA was investigated, and its binding constant was found to be 4.0×10⁵ M⁻¹. The proficiency of ethidium bromide (EB) displacement from its EB-CTDNA complex by C1 was performed by the fluorescence quenching method, and Stern-Volmer quenching constant (K_sv) was found to be 4.3×10⁵ M⁻¹. Similarly, the interaction of C1 with BSA protein was investigated by UV-Vis and fluorescence methods. The apparent association constant (K_a) and K_sv were determined (K_a = 2.8×10⁴ M⁻¹ and K_sv = 5.5×10⁴ M⁻¹). In vitro cytotoxicity of the complex, [Pd(LS^Et)Cl] (C1), towards human gastric cancer cell lines (AGS) was assessed by the MTT assay method. The half maximal inhibitory concentration (IC₅₀) of C1 (9.55 ± 1.23 µM) towards AGS cancer lines was found to be lower than cisplatin (23.13 ± 1.03 µM).

Graphical abstract

Herein, new palladium(II) complex, [Pd(LS^Et)Cl] (C1) with benzothiazole-based ONS donor pincer ligand (HLS^Et) was synthesized and characterized by several spectroscopic techniques. Interaction of C1 with CT DNA and BSA protein was investigated by UV-Vis and fluorescence methods. In vitro cytotoxicity of the complex toward human gastric cancer cell lines (AGS) was evaluated by the MTT assay method. The half maximal inhibitory concentration (IC₅₀) of the palladium(II) complex (9.55±1.23 µM) was found to be less compared to cisplatin (23.13±1.03 µM) towards AGS cancer lines.