Synthesis,Characterization, Cytotoxicity and Detailed HSA Interaction of New Zinc(II) Complexes Containing Dithiocarbamate and Heterocyclic N-donor Ligands

Zn(ph-dtc)(bpy)]Cl (1) and Zn(ph-dtc)(phen)]Cl (2) (where bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline and ph-dtc = phenylacetichydrazidedithiocarbamate) were synthesized and characterized by elemental analysis and spectroscopic methods (FT–IR, UV–Vis and ¹H NMR). Zn(II) complexes were examined in biological tests in vitro using MCF-7 breast cancer cell line. Both complexes showed significant cytotoxic activity against human breast cancer MCF-7 cells. The interaction of above compounds with Human Serum Albumin (HSA) was investigated by means of various spectroscopic (at pH ～ 7.4 in Tris–HCl buffer medium) and molecular docking methods. The fluorescence data showed that 1 and 2 quench the intrinsic fluorescence of HSA through a static quenching procedure. The binding constants (K_b) and the number of binding sites (n ～ 1) were calculated. The thermodynamic analysis suggested that hydrophobic interaction played major roles in the binding of 1 or 2 to HSA. The distance r between protein and the above-mentioned compounds was obtained according to fluorescence resonance energy transfer. The conformational changes of protein secondary structure in the presence of Zn(II) complexes were proven using UV–Vis absorption and circular dichroism techniques. Also, docking results confirmed the spectroscopic results.