Observations on the silicic acid chromatography of the neutral lipides of rat liver, beef liver, and yeast.

Within the past several years the application of silicic acid to the chromatographic fractionation of simple and complex lipides has received increased attention. In particular this adsorbent has been used in the separation of phospholipides by McKibbin (I), Lea et aE. (Z), and Hanahan et al. (3). As shown by Borgstrom (4), who used model lipide compounds, and Fillerup and Mead (5), who employed mainly the naturally occurring lipide of plasma, the various neutral lipides can also be separated on silicic acid by judicious choice of solvents. Lovern (6), working with the lipides of the haddock flesh, obtained quite sharp peaks on silicic acid chromatography but subsequently found that these components did not necessarily represent pure fractions. In a study of the lipides of human hair, Nicolaides and Foster (7) have reported a partial fractionation on silicic acid with benzenediethyl ether mixtures. In a consideration of the various studies carried out on neutral lipide separations on silicic acid, it seemed that insufficient characterization data were available on the individual fractions thus obtained. Furthermore, in view of our experience, petroleum ether as the main non-polar solvent was neither as effective nor as reproducible as desired. In a preliminary note from this laboratory (8), it was reported that pure n-hexane appeared suitable as the major non-polar solvent, and some of the characteristics of fractions obtained by silicic acid chromatography of certain neutral lipides were presented. The present communication provides further details on this study of the chemical nature of the neutral lipides from rat liver, beef liver, and bakers’ yeast (Sacchuromyces cerevisiae).