Four mononuclear platinum(II) complexes: synthesis, DNA/BSA binding, DNA cleavage and cytotoxicity

Four new platinum(II) complexes: Pt^II L1·H₂O (C1, H₂ L1 = C₂₀H₁₆N₂O₂), Pt^II L2Cl₂ (C2, L2 = C₂₂H₁₆N₂O₂), Pt^II L3Cl₂·H₂O (C3, L3 = C₂₀H₁₆N₂), Pt^II L4Cl₂·0.4H₂O (C4, L4 = C₁₈H₁₄N₄) have been synthesized and characterized by using various physico-chemical techniques. The binding interaction of the four platinum(II) complexes C1-C4 with calf thymus (CT)-DNA has been investigated by UV-Vis and fluorescence emission spectrometry. The apparent binding constant (K _app) values follow the order: C3 > C1 > C2 > C4. In addition, fluorescence spectrometry of bovine serum albumin (BSA) with the four platinum(II) complexes C1-C4 showed that the quenching mechanism might be a static quenching procedure. For C1-C4, the number of binding sites was about one for BSA and the binding constants follow the order: C3 (7.08 × 10⁵M^-1) > C1 (2.82 × 10⁵M^-1) > C2 (0.85 × 10⁵M^-1) > C4 (0.15 × 10⁵M^-1). With the single condition change such as absence of an external agent, the DNA cleavage abilities of C3 exhibit remarkable changes. In addition, the cytotoxicity of C3 in vitro on tumor cells lines (MCF-7, HepG2 and HT29) were examined by MTT and showed better antitumor effects on the tested cells.