Interactions of metal ions with two quinolone antimicrobial agents (cinoxacin and ciprofloxacin) -: Spectroscopic and X-ray structural characterization.: Antibacterial studies

Several novel metal-quinolone compounds have been synthesized and characterized by analytical, spectroscopic and X-ray diffraction methods. The crystal structure of the four compounds, Na-2[(Cd(Cx)(3))(Cd(Cx)(3)(H2O))].12H(2)O, [Co(Cp)(2)(H2O)(2)].9H(2)O, [Zn(Cp)(2)(H2O)(2)].8H(2)O and [Cd(HCp)(2)(Cl)(2)].4H(2)O, is presented and discussed: HCx =1-ethyl-1,4-dihydro-4-oxo(1,3)-dioxolo(4,5 g)cinnoline-3-carboxylic acid and HCp=1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid. In all these compounds the quinolone acts as a bidentate chelate ligand that binds through one carboxylate oxygen atom and the exocyclic carbonyl oxygen atom. Complexes of ciprofloxacin were screened for their activity against several bacteria, showing activity similar to that of the ligand. In addition, the number of bacteria killed after 3 h of incubation with the ligand, [Co(Cp)(2)(H2O)(2)].9H(2)O, Ni(Cp)(2).10H(2)O and Cu(Cp)(2).6H(2)O, was determined against S. aureus ATCC25923. There is a direct relationship between the growth rate and the lethal rate. Against growing bacteria, the ligand is the most bactericidal and Cu(Cp)(2).6H(2)O is the less bactericidal. On the contrary, against non-dividing bacteria, the complexes were more bactericidal than the ligand, with Cu(Cp)(2).6H(2)O the most bactericidal compound. (C) 2002 Elsevier Science Inc. All rights reserved.