Photooxidation of Linoleic Acid by Ultraviolet Light and Effect of Superoxide Anion Quencher

Abstract

Peroxidation of linoleic acid (LA) was promoted by ultraviolet (UV) light of main wave-length 254 nm in a 40% aqueous ethanol solution at pH 7.0 and 25°C. The reduction of nitroblue tetrazolium (NBT), an indicator of superoxide anion (O₂^-), was observed in the photooxidation of LA, and was dependent on the photolysis of linoleic acid hydroperoxides (LAHPO). The reduction of NBT in the photolysis of LAHPO required the presence of oxygen, and was inhibited by the addition of Cu (II)-Gly complex, which is known to have super-oxide dismutase-like activity. The photooxidation of LA was inhibited by the addition of NBT or Cu (II)-Gly complex, and these inhibitory effects depended on the O₂^- quenching activities of these additions rather than on the decrease in the transmittance of UV light absorbed by the additions. These facts suggest that Cu (II)-Gly complex inhibits the photooxi-dation of LA by quenching O₂^- or an O₂^-like factor derived from the photolysis of LAHPO.