Photochemical properties and phototoxicity of Pazufloxacin: a stable and transient study.

Photochemical properties and phototoxicity of Pazufloxacin (PAX) were systematically investigated in aqueous solutions using UV–Vis, fluorescence, laser flash photolysis, pulse radiolysis and SDS–PAGE gel electrophoresis techniques. PAX triplet-state (3PAX∗) absorption spectra (λmax=570nm) was determined. 3PAX∗ was quenched by PAX and O2, with rate constants of 6.9×108 and 3.2×108dm3mol−1s−1, respectively. The pKa values (5.7 and 8.6) for the protonation equilibrium were determined by UV–Vis and fluorescence techniques. The PAX triplet energy (ET=260.3kJ/mol) was obtained using energy transfer method. The reaction of electron transfer from tryptophan (TrpH) and dGMP to 3PAX∗ was found with rate constants of 8.8×107 and 8.7×106dm3mol−1s−1, respectively. The rate constants for reactions of OH, SO4- and hydrated electron with PAX were found to be 5.8×108, 2.1×109 and 9×109dm3mol−1s−1, respectively. Based on the results obtained, a rational scheme for dGMP, TrpH and lysozyme photodamage induced by PAX was proposed.