Radical reactions induced by ketoprofen in phospholipid membranes under ultraviolet light irradiation.

2-(3-Benzoylphenyl)propanoic acid (ketoprofen), one of the nonsteroidal anti-inflammatory drugs, causes photocontact dermatitis by ultraviolet (UV) light as a side effect. In this study, we examined radical reactions induced by ketoprofen in the lipid membranes under UV irradiation using egg yolk phosphatidylcholine (egg-PC) liposomal membranes containing 5- or 16-doxyl stearic acid (5- or 16-DSA), which carry nitroxyl radical at the 5- or 16-position of the fatty acid chain, respectively. When the suspension of liposomal membrane was mixed with ketoprofen and irradiated with UV, electron spin resonance signal of 5- and 16-DSA in the membrane decreased. The decay consisted of fast decay and subsequent slow decay. The overall decay for 5-DSA was faster than that for 16-DSA. The rate of slower decay of 16-DSA increased with ketoprofen concentration. The bulk lipid in the membrane affected the rate of slower decay of 5-DSA; the rate increased with the amount of egg-PC and decreased in the rigid membrane composed of dipalmitoylphosphatidylcholine. When spin trapping studies with α-(4-pyridyl 1-oxide)-N-tert-butylnitrone (POBN) and 5,5-dimetyl-1-pyrroline-N-oxide (DMPO) were performed in ketoprofen solution, C-centered radical adducts of POBN and superoxide anion radical adducts of DMPO were detected after UV irradiation. POBN suppressed the signal decay of 5-DSA in the liposomal membrane, whereas superoxide dismutase accelerated it. These results support that ketoprofen penetrates the lipid membrane and induces a radical reaction near the polar region in the membrane, and that ketoprofen-related C-centered radical is involved in the radical reaction.

Electrolytic aminated carbon materials for the electrocatalytic redox reactions of inorganic and organic compounds.

Some kinds of amine groups can be introduced to the glassy carbon surface by the electrode oxidation of the carbon electrode surface in ammonium carbamate solution, and this amine groups modified electrode is named as an aminated glassy carbon electrode. The existences of not only primary amine but also secondary and tertially amines were confirmed by X ray photoelectron spectroscopy. The applications of the aminated carbon material for the electrocatalytic reductions of oxygen, hydrogen peroxide, and organic compounds such as quinones were carried out, and the effects of amination on the formation of electrocatalytic sites for many species were revealed. The electrocatalyzed cyclic voltammograms of metal ions and metal chelate compounds obtained by aminated glassy carbon electrodes are also discussed. Moreover, we intend to describe that the aminated carbon electrode can exhibit the large reduction waves of inorganic oxoacids such as N02- or bromide ion. The introduced functional groups containing nitrogen atom can change the distribution of the electron densities of the graphite carbon surface, and this specific electron distribution environment may generate the various electrocatalytic activities.