DNA binding and cytotoxicity of some Cu(II)/Zn(II) complexes containing a carbohydrazone Schiff base ligand along with 1,10-phenanthroline as a coligand

We report the synthesis, characterization and biological activities of the complexes [Cu(o-phen)HL] (1), [Cu(o-phen)LCu(OAc)] (2), and [Zn(o-phen)LCu(OAc)] (3), where, H3L=o-HOC6H4C(H)N–NH–C(OH)N–NC(H)–C6H4OH-o, o-phen=1,10-phenanthroline, and OAc=CH3COO−. The free ligand and compound 3 have been characterized by X-ray crystallography. A four-line EPR pattern originating from the interaction of the unpaired electron with the central 63/65Cu nucleus (I=3/2) with the isotropic coupling constant (Aiso) value of 80±1.5G at RT for compound 1 in DMF suggests its monomeric nature in solution. These compounds undergo irreversible oxidation-reduction. Biological studies show intercalative DNA binding and remarkable cell cytotoxicity as well as anticancer activity. The IC50 values of 1, 2 and 3 for the human lung cancer A549 cell line (0.44, 0.22, and 4.80μM, respectively) and for the breast cancer MCF7 cell line (2.7, 4.1, and 3.6μM, respectively) are found to be very promising and appear to be more potent than some anticancer drugs tested for these cell lines. Most importantly, 3 is found to be remarkably less toxic for HaCaT and L132 normal cell lines as evident from the cell viabilities of these two cell lines in presence of this compound.