PHOTOCHEMICAL AND PHOTOBIOLOGICAL PROPERTIES OF KETOPROFEN ASSOCIATEDWITH THE BENZOPHENONE CHROMOPHORE

Irradiation of ketoprofen in neutral aqueous medium gave rise to 3-eth ylbenzophenone as the major photoproduct. Its formation is justified v ia protonation of a benzylic carbanion or hydrogen abstraction by a be nzylic radical. Minor amounts of eight additional compounds were isola ted. Four of them are derived from the benzylic radical: 3-(1-hydroxye thyl)benzophenone, 3-(1-hydroxyethyl)benzophenone, 3-acetylbenzophenon e and 2,3-bis-(3-benzoylphenyl)butane. The other four products involve initial hydrogen abstraction by the excited benzophenone chromophore of ketoprofen: 2-bis-(3-ethylphenyl)-1,2-diphenyl-1,2-ethanediol, zoyl phenyl)-1-(3-ethylphenyl)-1-phenylpropan-1-ol, alpha-(3-ethylphenyl)ph enylmethanol, 1, -[3-(2-hydroxycarbonylethyl)phenyl]-1,2-diphenyl-1 ,2 -ethanediol. The latter process was found to mediate the photoperoxida tion of linoleic acid through a type I mechanism, as evidenced by the inhibition produced by the radical scavengers butylated hydroxyanisole and reduced glutathione. The major photoproduct, which contains the b enzophenone moiety but lacks the propionic acid side chain, also photo sensitized linoleic acid peroxidation. Because lipid peroxidation is i ndicative of cell membrane lysis, the above findings are highly releva nt to explain the photobiological properties of ketoprofen.