Oxovanadium(IV) complexes with Knoevenagel Schiff base condensate as impending chemotherapeutic agents: Synthesis,characterization, biological screening and anti-proliferative assay

Two novel oxovanadium(IV) complexes [VOL1]SO₄ (1) and [VOL2]SO₄ (2) containing Knoevenagel condensate Schiff base ligand (L1/L2) have been synthesized and characterized by physical, spectral and analytical methods. These complexes are reported as ionic in nature on the basis of elemental composition and molar conductance, and possess square pyramidal geometry around the central metal ions. The binding interactions of (1) and (2) with calf thymus DNA (CT DNA) were explored by absorption spectrophotometric titration, cyclic voltammetry data and viscosity measurements. The calculated intrinsic binding constant values (K_b) for (1) and (2) obtained from UV–Vis absorption studies are 0.4 × 10⁵ and 5.6 × 10⁵ (M⁻¹) respectively. These experimental results indicate that (1) and (2) are intercalative binders and avid binder to CT DNA with different affinities. These complexes exhibit significant oxidative cleavage of supercoiled plasmid (pUC18) DNA in the presence of activators. In particular, the in vitro antimicrobial efficacy of oxovanadium(IV) complexes reveal that they are more active than free ligands. Besides, the in vitro cytotoxic effect of the titled complexes were examined on a bundle of human tumor cell lines such as MCF-7 and HeLa cancerous cell lines by the MTT method. Interestingly, complex (2) exhibits more potent cytotoxic activity than the other complex and standard drug (cisplatin). The mode of cell death was assessed by Hoechst 33258 staining morphological studies.