Ni(II) Ternary Complex Based on Antimicrobial Drug Enoxacin: Synthesis and Biological Properties

First Ni(II) ternary complex using the quinolone antibacterial agent enoxacin (HEn) as ligand and 1,10-phenanthroline as co-ligand has been synthesized and characterized. It is a mononuclear structure, in which enoxacin acts as a bidentate ligand bound to the metal through the ketone oxygen and a carboxylate oxygen atom. The complex exhibited good binding propensity to human and bovine serum albumin proteins having relatively high binding constants (6.40x10(4) and 7.12x10(4), respectively). The investigation of the interaction of the complex with calf-thymus (CT) DNA has been performed with UV and circular dichroism (CD) spectroscopies, indicating that they bind to CT DNA probably by the intercalative binding mode. The binding constant (K-b) of the complex with CT DNA calculated with UV is 2.03x10(5), which is higher than that of free enoxacin drug (2.09x10(4)) and even higher than that of typical intercalation indicator (1.23x10(5)) of ethidium bromide (EB). Fluorescence competitive studies with EB have revealed that the complex exhibited the ability to displace the DNA-bound EB using the intercalative binding site. In addition, the antimicrobial activity showed that the complex exhibited a little bit good inhibition (MIC=1.843 (gmL(-1)) against B. subtilis than free HEn.