Evidence of the formation of different hydroperoxides in irradiated gamma-linolenate solutions: Effect of micelle formation

Peroxidation of unconjugated polyunsaturated fatty acids such as linolenic acid proceeds through a free radical chain mechanism and is accompanied by the formation of conjugated dienes such as hydroperoxides. In an investigat ion of radiation-induced oxidation of aqueous Linolenate, we have measured two indexes of peroxidation: (1) conjugated dienes by means of absorption s pectroscopy and (2) hydroperoxides by high-pressure liquid chromatography u sing detection of chemiluminescence, The experimental results indicate a st rong effect of the concentration of linolenate on the yields of oxidized pr oducts. In addition, this work shows the quantitative production of two kin ds of hydroperoxides. The ratio of these hydroperoxides is independent of t he radiation dose but is dependent on the linolenate concentration. One hyd roperoxide is formed predominantly below the critical micellar concentratio n (3 mM under our conditions), while the second is observed predominantly w hen micelles are formed in the aqueous medium. The influence of the composi tion of the medium on the nature of both hydroperoxides is discussed. (C) 2 000 by Radiation Research Society.