Synthesis, structure and biological activity of copper(II) complexes with gatifloxacin

The copper(II) complexes with the third-generation quinolone gatifloxacin (Hgati) were prepared in the absence or presence of the N,N'-donor heterocyclic ligands 2,2'-bipyridylamine (bipyam), 1,10-phenanthroline (phen) or 2,2'-bipyridine (bipy) and were characterized physicochemically and spectroscopically. The crystal structures of complexes [Cu(gati)(bipyam)Cl]center dot MeOH center dot H2O and [Cu(MOM-gati)(bipy)Cl]center dot MeOH center dot 3H(2)O (MOM = methoxymethyl) were determined by X-ray crystallography. The antimicrobial activity of the compounds was tested against four different microorganisms (Escherichia coli, Xanthomonas campestris, Staphylococcus aureus and Bacillus subtilis) and was found similar or higher than that of free Hgati. The interaction of the complexes with calf-thymus DNA was monitored by UV-vis spectroscopy and DNA-viscosity measurements and by competitive studies with ethidium bromide; intercalation is suggested as the most possible binding mode. The interaction of the complexes with human or bovine serum albumins was studied by fluorescence emission spectroscopy and the corresponding albumin-binding constants of the complexes were calculated. (C) 2016 Elsevier Ltd. All rights reserved.