Pulse radiolysis study on gatifloxacin — A fluoroquinolone antibiotic

Abstract

The reactions between gatifloxacin (GFX) and various one-electron oxidants, such as ·OH, N3·, Br2·−, and SO4·−, have been studied by pulse radiolysis techniques. The GFX radical anion formed in the reaction of GFX with eaq− could either be protonated or deprotonated, and the absorption of GFX radical anion was located at 390 nm. The transient species produced by the reaction of GFX with ·OH radical shows a broad band in the 380–600 nm region with a shoulder, while the oxidation by N3·, SO4·−, and Br2·− results in an absorption band with λmax = 370 nm. At neutral condition (pH 7), the rate constants of GFX reacting with ·OH, N3·, Br2·−, SO4·− and eaq− are estimated to be 1.0 × 1010, 3.1 × 109, 2.8 × 109, 3.0 × 109, and 1.8 × 1010 dm3 mol−1 s−1, respectively. From the pH dependence on the formation of electron adducts and on the rate constant of GFX with eaq−, the pKa of GFX radical anion is estimated to be 5.5 and 9.3.