Synthesis, characterization and in vitro DNA binding and cleavage studies of Cu(II)/Zn(II) dipeptide complexes

Novel dipeptide complexes Cu(II)-Val-Pro (1), Zn(II)-Val-Pro (2), Cu(II)-Ala-Pro (3) and Zn(II)-Ala-Pro (4) were synthesized and thoroughly characterized using different spectroscopic techniques including elemental analyses, IR, NMR, ESI-MS and molar conductance measurements. The solution stability study carried out by UV-vis absorption titration over a broad range of pH proved the stability of the complexes in solution. In vitro DNA binding studies of complexes 1-4 carried out employing absorption, fluorescence, circular dichroism and viscometric studies revealed the binding of complexes to DNA via groove binding. UV-vis titrations of 1-4 with mononucleotides of interest viz., 5'-GMP and 5'-TMP were also carried out. The DNA cleavage activity of the complexes 1 and 2 were ascertained by gel electrophoresis assay which revealed that the complexes are good DNA cleavage agents and the cleavage mechanism involved a hydrolytic pathway. Furthermore, in vitro antitumor activity of complex 1 was screened against human cancer cell lines of different histological origin.