Organoruthenium (II) complexes featuring pyrazole-linked Schiff base ligands: Crystal structure, DNA/BSA interactions, cytotoxicity and molecular docking

Half-sandwiched ruthenium (II) arene complexes with piano stool-like geometry with the general formula [(p-cymene)RuClL1] and [(p-cymene)RuClL2] [where L-1 = (Z)-N '-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)furan-2-carbohydrazide and L-2 = (Z)-N '-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)thiophene-2-carbohydrazide] were synthesized and characterized. The single crystal X-ray data revealed that the complexes belong to the same crystal system (monoclinic) with octahedral geometry, where the ruthenium atom is surrounded by hydrazone ligand coordinated through ON atoms, one chloride labile co-ligand and the remaining three coordination sites covered by an electron cloud of p-cymene moiety. The interaction between the complexes and DNA/bovine serum albumin (BSA) was evaluated using absorption and emission titration methods showing intercalative modes of interaction. The DNA cleavage ability of the complexes was checked by agarose gel electrophoresis method exhibiting the destruction of DNA duplex arrangement. To understand the interaction between ruthenium complex and DNA/BSA molecule, molecular docking studies were performed. In vitro cytotoxicity of the complexes was examined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on human lung cancer cell line, A549, and found that at lower IC50, cell growth inhibition has occurred. Similarly, the IC50 values of the complexes treated with cancerous cell lines have produced a significant amount of lactase dehydrogenase and nitrite content in the culture medium, which were evaluated as apoptosis-inducing factors, suggesting that the ruthenium (II) arene hydrazone complexes with pyrazole ligands have promising anticancer activities.