Seasonal variations in the fatty acid composition of phospholipids and triacylglycerols of brown trout

Abstract

Seasonal variations on phospholipid (PL) and triacylglycerol (TG) fatty acid (FA) compositions in muscles of Salmo trutta macrostigma were investigated by gas chromatography (GC) using the method described by Folch. The total lipid of the muscle was extracted using chloroform/methanol (2: 1, v/v) and was separated into TG and PL using thin layer chromatography (TLC). A total of nineteen and sixteen different fatty acids were determined in TG and PL, respectively. The distributions of Sigma SFAs (saturated fatty acids), Sigma MUFAs (monounsaturated fatty acids) and Sigma PUFAs (polyunsaturated fatty acids) proportions were found to be different among PL and TG fractions in all seasons. TG contained a lower proportion of Sigma PUFA, but a higher proportion of Sigma MUFA and Sigma SFA than PL. The major components were palmitic acid (16: 0), oleic acid (18: 1 n-9), eicosapentaenoic acid (EPA, 20: 5 n-3) and docosahexaenoic acid (DHA, 22: 6 n-3) in PL, 16: 0, palmitoleic acid (16: 1 n-7), 18: 1 n-9, linoleic acid (LA, 18: 2 n-6), linolenic acid (ALA, 18: 3 n-3), 20: 5 n-3 and 22: 6 n-3 in TG extracted from muscle of S. trutta macrostigma in all seasons. The total lipid content varied seasonally from 1.44% to 1.90% in female muscle of wet weight for S. trutta macrostigma. N-3/n-6 ratios of PL and TG were found to be 5.19-12.0 and 1.09-2.62, respectively.