J. J. Yin1 , M. P. Yurawecz2 , J. K. Kramer3 , A. R. Eynard4 , L. Yu5 , 1CFSAN, FDA, College Park, MD, 2Retired, 3Agri-Food Canada, 4Universidad Nacional de Córdoba, Argentina, 5University of Maryland
Conjugated linoleic acids (CLA) are a group of octadecadienoic acid (18:2) which are naturally present in food products and may have health beneficial effects. This study was undertaken to determine and compare the high purity c9,t11-CLA, t10,c12-CLA, and LA for their effects on oxygen diffusion-concentration products and depletion in liposome suspensions and ethanol solutions of the soy, egg yolk, and rat brain and heart phospholipids using electron spin resonance spin-label oximetry method.Individual CLA isomers differed in their effects on oxygen diffusion-concentration products or lipid peroxidation in both aqueous liposome suspensions and ethanol solutions, and these effects are dependent on the nature of the testing lipid system and the origin of the phospholipids.This study also examined and compared c9, t11-CLA, t10, c12-CLA, and linoleic acid (LA) for their reactions with the stable DPPH radicals in ethanol solutions and liposomes.PC containing individual CLA isomers and LA differed in their capacities to react with and quench DPPH radicals in both ethanol solution and in liposome, suggesting that both fatty acid composition and lipid system may alter the estimation of DPPH radical-fatty acid interactions. In addition, the effects of the two CLA isomers on phase transition temperature of liposomes were investigated and compared to that of linoleic acid (18:2n-6).Incorporation of LA and CLA isomers into DMPC reduced the phase transition temperature from 23.6°C to 23.1° and 23.3°C, respectively. The results form this study may provide additional information to explain the potential mechanisms involved in the beneficial actions of CLA isomers.