Lipid and Fatty Acid Composition of Low Pensity Lipoprotein and High Density Lipoprotein of Egg Yolk

Abstract

Egg yolk was fractionated into two lipoproten-containing fractions-low density lipoprotein (LDL) and high density lipoprotein (HDL)-by using ultracentrifugation. LDL contained 85.6% of lipid, 2.4% of total nitrogen, 1.0% of total phosphorus and 0.1% of total sulfur. HDL contained 27.3% of lipid, 10.9% of total nitrogen, 1.8% of total phosphorus and 0.6% of total sulfur. LDL showed only one band by protein stain in cellulose acetate membrane electrophoresis. This band was also stained by a oil red staining and schiff reaction of periodic acid. HDL was separated into five bands, one of which was stained by a oil red staining. Lipids extracted with chloroform-methanol (2:1) from these two lipoproteins differed in content and composition. The composition of tryglycerides, lecithin and cephalin was main difference of these lipeproteins. Nimety three point nine percent of non polar lipids and 27.0% of polar lipids were recovered with heptane from the chloroform-methanol extracts of LDL. On the other hand, 67.9% of non polar lipids and 18.0% of polar lipids of chloroform-methanol extracts of HDL were transferred to heptane fraction. Cephalin was more readily extracted with heptane than other phospholipids in LDL and HDL. Tryglyceride, lecithin and cephalin existed in chloroform-methanol extracts of LDL and HDL showed similar fatty acid composition. Heptane extracts of LDL and HDL contained larger amounts of C_16:0 fatty acid than that of the chloroform-methanol extracts.