Metal complexes with the quinolone antibacterial agent N-propyl-norfloxacin: Synthesis, structure and bioactivity

Nine new metal complexes of the quinolone antibacterial agent N-propyl-norfloxacin, pr-norfloxacin, with VO2+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, MoO22+, Cd2+ and UO22+ have been prepared and characterized with physicochemical and spectroscopic techniques while molecular mechanics calculations for Fe3+, VO2+ and MoO22+ complexes have been performed. In all complexes, pr-norfloxacin acts as a bidentate deprotonated ligand bound to the metal through the pyridone and one carboxylate oxygen atoms. All complexes are six-coordinate with slightly distorted octahedral geometry. For the complex VO(N-propyl-norfloxacinato)2(H2O) the axial position, trans to the vanadyl oxygen, is occupied by one pyridone oxygen atom. The investigation of the interaction of the complexes with calf-thymus DNA has been performed with diverse spectroscopic techniques and has shown that the complexes can be bound to calf-thymus DNA resulting to a B → A DNA transition. The antimicrobial activity of the complexes has been tested on three different microorganisms. The complexes show equal or decreased biological activity in comparison to the free pr-norfloxacin except UO2(pr-norf)2 which shows better inhibition against S. aureus.