Polar lipids in bovine milk II. Long-chain bases, normal and 2-hydroxy fatty acids, and isomeric cis and trans monoenoic fatty acids in the sphingolipids

Abstract

Sphingomyelin, glucosylceramide and lactosylceramide were isolated from spray-dried buttermilk powder. The long-chain bases in the three sphingolipids were very similar in composition, and consisted of normal, iso and anteiso saturated and monounsaturated dihydroxy bases. Hydroxy fatty acids comprised less than 1% of the total fatty acids. The 2-hydroxy fatty acids in sphingomyelin were indentified by combined gas-liquid chromatography and mass spectrometry as C 16:0-C 25:0 and C 23:1-C 25:1 acids. The compositions of the normal and 2-hydroxy fatty acids were similar in all three sphingolipids. The trans contents of the monoenoic fatty acids from sphingomyelin were C 18:1 = 94.2%, C 22:1 = 98.2%, C 23:1 = 63.9%, C 24:1 = 23.4% and C 25:1 = 7.1%. Similar patterns were observed in glucosylceramide and lactosylceramide. The distribution of cis double bonds in C 23:1, C 24:1 and C 25:1, and trans double bonds in C 23:1 and C 24:1 were determined, and the significance of the results discussed.