The distribution of fatty acids between the α′- and β-positions of the glycerophospholipids of buttermilk

Abstract

Fractionation of buttermilk phospholipids on silicic acid columns gave a cephalin (mixture of amino-N; phospholipids) fraction, in which approximately 29% of the total fatty acids were saturated, and phosphatidyl choline, in which approximately 57% of the total fatty acids were saturated. The main difference between the fatty acids of the two phospholipid fractions was in the proportions of palmitic and oleic acid; a further difference was the predominance of the polyenoic acids in the cephalin fraction. In phosphatidyl choline, the ratio of unsaturated to saturated fatty acids in the α′-position was 0.54 and in the β-position, 1.05. Although the nature of the fatty acids present in minor quantities in lecithin and cephalin was very different, the positional distributions of the major fatty acids common to both phospholipid fractions were similar. Oleic and palmitic acids together contributed almost identical proportions to the α′ and to the β fatty acids in both the cephalin fraction and phosphatidyl choline. These two acids comprised 61% of the total acids in the cephalin fraction and 66% of the total acids in phosphatidyl choline. In both the amino-N and choline glycerophospholipids, most of the stearic acid was in the α′-position; whereas most of the dienoic, trienoic, and polyenoic acids were in the β-position. It has been found that the unsaturated acids are less randomly distributed than previously reported for milk glycerophospholipids, but are more randomly distributed than in many other mammalian tissues.