Different types of copper complexes with the quinolone antimicrobial drugs ofloxacin and norfloxacin: Structure, DNA- and albumin-binding

Three novel copper(II) complexes with the second-generation quinolone antibacterial agents norfloxacin (nfH) and ofloxacin (ofloH) have been synthesized resulting in the complexes [Cu(nfH)(phen)Cl]Cl·5H2O (1·5H2O), [Cu(nfH)2]Cl2·6H2O (2·6H2O) and [CuII(ofloH)2][(CuICl2)2] (3), respectively. The crystal structures of the complexes have been determined by X-ray crystallography revealing that the quinolones act as bidentate ligands coordinated to Cu(II) atom through the pyridone oxygen and a carboxylato oxygen. UV study of the interaction of the quinolones and the complexes with calf-thymus DNA (CT DNA) has shown that they can bind to CT DNA with [CuII(ofloxacin)2][(CuICl2)2] exhibiting the highest binding constant to CT DNA. The cyclic voltammograms of the complexes in the presence of CT DNA solution have shown that the interaction of the complexes with CT DNA is mainly through electrostatic binding. DNA solution viscosity measurements have shown that the interaction of the compounds with CT DNA by classical intercalation may be ruled out. Competitive studies with ethidium bromide (EB) indicate that the complexes can partially displace the DNA-bound EB suggesting low to moderate competition with EB. Norfloxacin, ofloxacin and their copper complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values.

Three novel copper(II) complexes with the quinolone antibacterial agents norfloxacin and ofloxacin have been characterized and their ability to bind to biomolecules has been evaluated. Copper complexes can bind to CT DNA and exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values.Figure optionsDownload as PowerPoint slideHighlights
► Copper(II) complexes with quinolone ligands norfloxacin and ofloxacin
► Three crystal structures of copper mixed–ligand quinolone complexes
► The complexes can bind to human or bovine serum albumin proteins.
► The complexes bind to DNA via electrostatic interaction.
► The complexes can partially displace EB from EB–DNA complex.