DNA binding studies of new valine derived chiral complexes of tin(IV) and zirconium(IV)

Valine derived chiral complexes of SnCl4 (1) and ZrCl4 (2) were designed as potent antitumor agents. These complexes were characterized by elemental analysis, IR, 1H NMR, 119Sn NMR and ESI mass spectroscopy. In vitro binding studies of complexes 1 and 2 under physiological conditions at room temperature with CT-DNA were carried out employing UV–vis absorption titration, fluorescence studies and viscosity measurements. The extent of binding was quantified by Kb values of complexes 1 and 2 which were found to be 1.97 × 104 and 1.17 × 103 M−1, respectively, suggesting that complex 1 has significantly greater DNA binding propensity in contrast to the complex 2. The mode of action at the molecular level was ascertained by the interaction of complex 1 with 5′GMP and 5′TMP which revealed that complex 1 binds via electrostatic mode with the oxygen of the negatively charged surface phosphate group of the DNA helix. The supercoiled pBR322 plasmid DNA cleavage activity of complex 1 was ascertained by gel electrophoresis assay.