The Unsaturated Fatty Acids of Egg Lecithin

The work on liver lecithins by Levene and Ingvaldsen’ and by Levene and Simms,z has shown the existence of lecithins which are distinguished from one another by the nature of their unsaturated fatty acids. There were isolated from liver lecithin, two unsaturated fatty acids, oleic and arachidonic, as well as two saturated acids, palmitic and stearic. Hence on the basis of the present findings it is permissible to accept the existence in the liver of four lecithins. Furt,her work may lead to the discovery of an even greater number. The work on the liver lecithins suggested the need of a reinvestigation of the lecithins of other organs with a view of finding in them also lecithins containing acids of a higher order of unsaturation than that of oleic acid. The present communication contains the report of the work on egg lecithin. This “lecithin” also was found to contain more than one unsaturated fatty acid. Three acids were isolated; namely, oleic, linolic, and arachidonic. Oleic acid was identified by its iodine number and by its hydrogenation product, stearic acid. Linoleic acid was isolated in small quantities only and was identified as its tetrabromide. Arachidonic acid was identified by its octabromide and by its hydrogenation product, arachidic acid. Comparing the mixed lecithins of liver and those of the egg yolk, one is struck by the difference in the proportions of the individual forms in them. The liver lecithin contains a very large proportion of the forms with highly unsaturated fatty acids, whereas in the egg yolk the proportion of the latter is small.