Ruthenium(III) S-methylisothiosemicarbazone Schiff base complexes bearing PPh₃/AsPh₃ coligand: Synthesis, structure and biological investigations, including antioxidant, DNA and protein interaction, and in vitro anticancer activities

New Ru(III) isothiosemicarbazone complexes [RuCl(EPh₃)L ^1-4] (E = P or As) were obtained from the reactions between [RuCl₃(EPh₃)₃] and bis(salicylaldehyde)-S-methylisothiosemicarbazone (H₂L ^1-3)/bis(2-hydroxy-naphthaldehyde)-S- methylisothiosemicarbazone (H₂L⁴) ligands. The new complexes were characterized by using elemental analyses and various spectral (UV-Vis, IR, ¹H NMR, FAB-Mass and EPR) methods. The redox properties of the complexes were studied by using cyclic voltammetric method. The new complexes were subjected to various biological investigations such as antioxidant assays involving DPPH radical, hydroxyl radical, nitric oxide radical and hydrogen peroxide, DNA/protein interaction studies and in vitro cytotoxic studies against human breast cancer cell line (MCF-7). New complexes showed excellent free radicals scavenging ability and could bind with DNA via intercalation. Protein binding studies using fluorescence spectroscopy showed that the new complexes could bind strongly with bovine serum albumin (BSA). Photo cleavage experiments using DNA of E-coli bacterium exhibited the DNA cleavage ability of the complexes. Further, the in vitro anticancer activity studies on the new complexes against MCF-7 cell line exhibited the ability of Ru(III) isothiosemicarbazone complexes to suppress the development of malignant neoplastic disease cells.