Effect of UV Irradiation on Conjugated Linoleic Acid (9c 11t and 10t 12c)

Abstract

This study was carried out to examine the effects of UVA irradiation on the Conjugated Linoleic Acid (CLA) isomers; 9c11t CLA and 10t12c CLA. CLA 9c11t free fatty acid (90%) and 10t12c-Octadecadienoic acid methyl ester (90%) samples in UV transparent cuvettes sealed under nitrogen gas were subjected to UVA irradiation at 365 nm. About four drops of each sample were taken out at regular intervals. These irradiated samples were analyzed using IR spectroscopy and Gas Chromatography (GC). The second derivative profiles of the IR spectra of UVA irradiated 9c11t CLA and 10t12c CLA show the decrease in intensity of the peaks at wavenumbers at 944 and 986. Furthermore, a slight increase in the intensity of the peak at around 967/cm and a slight blue shift of the peak at 984 to 988/cm are also observed. The GC peaks corresponding to tt CLA isomers increase in intensity showing the isomerization of methylene interrupted 18:2 linoleic acid to tt isomers of Conjugated Linoleic Acids. Furthermore, formation of oleic acid (!8:1 9c) in the irradiated sample of 9c11t free fatty acid and formation of oleic and elaidic acid (18:1 9t) in the irradiated sample of 10t12c methyl ester also observed. The results clearly indicate the depletion of conjugated linoleic acids during UV irradiation.

Effect of UV Irradiation on Conjugated Linoleic Acid (9c 11t and 10t 12c)