title: A laser flash photolysis and pulse radiolysis study of primary photochemical processes of flumequine.
abstract: The 355 nm laser flash photolysis of argon-saturated pH 8 phosphate buffer solutions of the fluoroquinolone antibiotic flumequine produces a transient triplet state with a maximum absorbance at 575 nm where the molar absorptivity is 14,000 M(-1) cm(-1). The quantum yield of triplet formation is 0.9. The transient triplet state is quenched by various Type-1 photodynamic substrates such as tryptophan (TrpH), tyrosine, N-acetylcysteine and 2-deoxyguanosine leading to the formation of the semireduced flumequine species. This semireduced form has been readily identified by pulse radiolysis of argon-saturated pH 8 buffered aqueous solutions by reaction of the hydrated electrons and the CO2*- radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2,500 M(-1) cm(-1). In argon-saturated buffered solutions, the semireduced flumequine species formed by the reaction of the flumequine triplet with TrpH stoichiometrically reduces ferricytochrome C (Cyt Fe3+) under steady state irradiation with ultraviolet-A light. In the presence of oxygen, O2*- is formed but the photoreduction of Cyt Fe3+ by O2*- competes with an oxidizing pathway which involves photo-oxidation products of TrpH.
authors.affiliation: Laboratoire de Photobiologie, Museum National D'Histoire Naturelle, Paris, France.
authors.forename: M
authors.initials: M
authors.lastname: Bazin
authors.forename: F
authors.initials: F
authors.lastname: Bosca
authors.forename: M L
authors.initials: ML
authors.lastname: Marin
authors.forename: M A
authors.initials: MA
authors.lastname: Miranda
authors.forename: L K
authors.initials: LK
authors.lastname: Patterson
authors.forename: R
authors.initials: R
authors.lastname: Santus
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry*; D003574:Cytochrome c Group / Q000737:chemistry; D024841:Fluoroquinolones; D007834:Lasers; D010084:Oxidation-Reduction; D010782:Photolysis; D011807:Quinolizines / Q000737:chemistry*; D013053:Spectrophotometry
chemical_list: D000890:Anti-Infective Agents; D003574:Cytochrome c Group; D024841:Fluoroquinolones; D011807:Quinolizines; C012976:flumequine