Evaluation of DNA/BSA interaction and in vitro cell cytotoxicity of μ-oxido bridged divanadium(V) complexes containing ONO donor ligands.

Two new μ-oxido bridged divanadium (V) complexes, [VO(L)] (1 and 2) have been synthesized using bi-negative tridentate ONO-donor ligands, HL (HL = 4-tert-butyl-2-[[[3,5-di-tert-butyl-2-hydroxyphenyl]methylene]amino]phenol and HL = 5-bromo-2-[[[4-(diethylamino)-2-hydroxyphenyl]methylene]amino]phenol). The synthesized ligands and complexes have been characterized through FT-IR, UV-vis, NMR, and HR-ESI-MS techniques. Single crystal X-ray crystallography data confirmed distorted square pyramidal geometry for both the complexes. The aqueous phase stability of these complexes has been evaluated through HR-ESI-MS in CHCN:HO (80:20) mixture. Thereafter their interaction with calf thymus DNA (CT-DNA) have been studied using electronic absorption and fluorescence spectroscopy, revealing an intercalation mode of binding, with binding constant in the order of 10 M. Moreover, bovine serum albumin (BSA) interaction of 1 and 2 has been evaluated via fluorescence quenching experiment, which suggests that the quenching mechanism is static (~10 M) in nature. Additionally, the in vitro cytotoxicity of the complexes has been evaluated in human cervical cancer cells (HeLa) (IC = 13.57-16.62 μM) and normal mouse embryonic fibroblasts cells (NIH-3T3). The mechanism of cell death brought about by these complexes was studied by nuclear staining, cell cycle and Annexin V/PI double staining apoptotic assay. These studies indicate that 1 and 2 exert inhibitory effects on the S and G2M phase of cell cycle, which is an indication of apoptotic cell death. Also, a clonogenic assay was performed, which showed that the complexes could effectively inhibit colony formation.