title: Effect of basic amino acids on photoreaction of ketoprofen in phosphate buffer solution.
abstract: Photoreaction of ketoprofen (KP), one of the widely used nonsteroidal anti-inflammatory drugs (NSAIDs), was studied with transient absorption spectroscopy in phosphate buffer solution (pH 7.4) in the presence of basic amino acids of histidine (His), lysine (Lys) and arginine (Arg). Deprotonated form of KP (KP(-)) excited with UV-light irradiation gave rise to carbanion through a decarboxylation reaction. It was found that carbanion abstracted a proton from the side chain of the protonated amino acids to yield 3-ethylbenzophenone ketyl biradical (EBPH); however, no reaction was observed with alanine. The relative yield of EBPH by the proton transfer reaction with His was ca. 40 times larger than that of the other two basic amino acids, suggesting that the proton-donating ability of His (protonated His) should be quite high. The information on the photoreaction mechanism of NSAIDs with basic amino acids was essential to understand primary reaction of excited NSAIDs in vivo causing photosensitization on human skin.
authors.affiliation: Department of Chemistry and Biological Science, Aoyama Gakuin University, Kanagawa, Japan. suzuki@chem.aoyama.ac.jp
authors.forename: Tadashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Yohei
authors.initials: Y
authors.lastname: Osanai
authors.forename: Tasuku
authors.initials: T
authors.lastname: Isozaki
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D001120:Arginine / Q000737:chemistry*; D002021:Buffers; D005609:Free Radicals; D006639:Histidine / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007660:Ketoprofen / Q000737:chemistry*; D007700:Kinetics; D008239:Lysine / Q000737:chemistry*; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry; D011522:Protons; D012996:Solutions; D013057:Spectrum Analysis; D014466:Ultraviolet Rays; D014867:Water
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D002021:Buffers; D005609:Free Radicals; D017319:Photosensitizing Agents; D011522:Protons; D012996:Solutions; D014867:Water; D006639:Histidine; D007660:Ketoprofen; D001120:Arginine; D008239:Lysine