Fatty acids of bovine milk glycolipids and phospholipids and their specific distribution in the diacylglycerophospholipids

Milk lipids were fractionated by silicic acid column chromatography and preparative thinlayer chromatography (TLC). Ceramide monohexoside (CMH), ceramide dihexoside (CDH), phosphatidyl ethanolamine (PE), phosphatidyl choline (PC), phosphatidyl serine (PS), and sphingomyelin (Sph) were isolated, and the purity of each was checked by infrared spectroscopy and TLC. The diacylphospholipids were hydrolyzed with phospholipase A and the products separated by TLC. Fatty acid methyl esters were prepared from the various fractions and analyzed by gas chromatography. The glycolipids, CMH and CDH, and Sph contained large amounts of long-chain saturated fatty acids, especially C_22:0, C_23:0, and C_24:0, PE, PS, and PC contained C₁₀-C₂₂ normal and branched-chain saturated fatty acids, and C₁₅-C₂₀ unsaturated fatty acids (mainly monoenes). The distributions of saturated acids between the α′- and β-positions were respectively: PE, 46 and 11%; PS, 65 and 19%; and PC, 72 and 53%. PC was exceptional in that there was 10.8% myristic acid in the β-position and only 5.6% in the α′-position. PE and PS were similar in composition except that in PE oleic acid was evenly distributed, and in PS was largely in the β-position. In general, PC was much more saturated than PE or PS, and there was no overall pattern governing the specific distribution of the fatty acids in the three diacylphospholipids. Comparison with PC from other bovine tissues and from egg lecithin showed that fatty acids are located much less specifically in milk phospholipids than in PC from other sources. Presented at the AOCS Meeting, Houston, Texas, April, 1965.