Physicochemical properties of quinolone antibiotics in various environments

The progress and photosensitivity of quinolone antibiotics are briefly described. By the photolysis of nalidixic acid, the loss of -COOH group is observed. The photoreaction of fluoroquinolones involves heterolytic C-F bond. fragmentation. The protonation and divalent cation complexation equilibria are also examined. The spectroscopic properties of these drugs are intensively investigated in biological mimetic systems such as AOT reverse micelle, and H2O-CH3OH and H2O-CH3CN mixed solvents. For ofloxacin and norfloxacin, the excited-state intramolecular charge transfer (ICT) is observed. So, fluorescence spectra exhibit reverse solvatochromism in mixed solvents. The change of radiative and non-radiative rate constant can also be explained using this ICT. The influence of dielectric effects of solvent is more significant compared with the specific hydrogen bonding interaction. Theoretical treatments support all of these results. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.