Organometallic rhenium tricarbonyl-enrofloxacin and -levofloxacin complexes: synthesis, albumin-binding, DNA-interaction and cell viability studies.

Organometallic rhenium complexes have recently been considered in the development of novel antitumor agents due to their suitable properties. A series of rhenium(I) tricarbonyl complexes was synthesized with the quinolone antimicrobial agents enrofloxacin (Herx) and levofloxacin (Hlfx) and solvent (e.g., methanol), imidazole (im) or pyridine (py) as co-ligands. The complexes were characterized by spectroscopic methods. The interaction of the rhenium complexes with bovine serum albumin was investigated by fluorescence emission spectroscopy and the corresponding binding constants were determined. The binding of the rhenium complexes to calf-thymus DNA was monitored by UV-Vis spectroscopy, viscosity measurements and competitive studies with ethidium bromide. These studies indicated that intercalation is the most possible mode of action and the corresponding DNA-binding constants of the complexes were calculated. The cytotoxicity of the Re-complexes against human K-562 erythroleukemia cells was found to be moderate to high. These preliminary results are promising and warrant the design of new Re-complexes with improved properties in future studies.