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 = 570 nm) was determined. 3PAX∗ was quenched by PAX and O2, with rate constants of 6.9 × 108 and 3.2 × 108 dm3 mol−1 s−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 = 260.3 kJ/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 × 106 dm3 mol−1 s−1, respectively. The rate constants for reactions of OH, SO 4 - and hydrated electron with PAX were found to be 5.8 × 108, 2.1 × 109 and 9 × 109 dm3 mol−1 s−1, respectively. Based on the results obtained, a rational scheme for dGMP, TrpH and lysozyme photodamage induced by PAX was proposed.