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A Laser Flash Photolysis and Pulse Radiolysis Study of Primary Photochemical Processes of Flumequine ¶
Author(s) -
Bazin M.,
Bosca F.,
Marin M. L.,
Miranda M. A.,
Patterson L. K.,
Santus R.
Publication year - 2000
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2000)0720451alfpap2.0.co2
Subject(s) - radiolysis , flash photolysis , photochemistry , photodissociation , laser , chemistry , pulse (music) , flash (photography) , primary (astronomy) , optics , radical , physics , detector , organic chemistry , quantum mechanics , astronomy , reaction rate constant , kinetics
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 CO 2 ·− radicals with flumequine. The absorption maximum of the transient semireduced species is found at 570 nm with a molar absorptivity of 2500 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 Fe 3+ ) under steady state irradiation with ultraviolet‐A light. In the presence of oxygen, O 2 ·− is formed but the photoreduction of Cyt Fe 3+ by O 2 ·− competes with an oxidizing pathway which involves photo‐oxidation products of TrpH.