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Effect of Basic Amino Acids on Photoreaction of Ketoprofen in Phosphate Buffer Solution
Author(s) -
Suzuki Tadashi,
Osanai Yohei,
Isozaki Tasuku
Publication year - 2012
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 - 10.1111/j.1751-1097.2012.01132.x
Subject(s) - chemistry , deprotonation , protonation , carbanion , decarboxylation , amino acid , hydroxylation , photochemistry , ketoprofen , histidine , yield (engineering) , phenethylamine , free base , medicinal chemistry , stereochemistry , organic chemistry , chromatography , biochemistry , salt (chemistry) , ion , materials science , metallurgy , enzyme , catalysis
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.