Are Neutral Fat and Lecithin Present in Gall Bladder Bile?

Abstract

Since the time of Strecker 1 chemists who have worked with bile have appreciated the difficulty of separating lipoids from bile. The lipoid constituents as given by the text books at the present time are merely repetitions of the early figures given by Strecker, Hammarsten, 2 von Gorup-Besanez, 3 and others. These constituents are given as fatty acids, soaps, phosphatides, fat, and cholesterol. An examination of this early literature does not yield satisfactory evidence for the presence of either neutral fat or lecithin in bile.

Fresh bile may be extracted in 2 ways. One is to deproteinize by means of alcohol, then dry the protein-free bile and dissolve the residue in absolute alcohol, filtering off the inorganic salts, that are precipitated, and finally pouring the alcoholic solution into a large volume of anhydrous ethyl ether. This is the method used by Hammarsten.

The second method is to extract directly with ethyl and petroleum ether in the presence of some alcohol. In this manner a very persistent emulsion is formed that requires time to break. In either method a sticky molasses-like substance is obtained on evaporating the ether, which does not look like fat and contains bile salts, fatty acid, phosphorus, sulphur and nitrogen containing compounds and non-saponifiable material. After as thorough an extraction as can be carried out in this manner, saponification of the non-ether soluble residue with strong alkali will permit the extraction of much fatty acid that could not be extracted in the first place.

When 2,500 cc. of beef gall bladder bile is dried in air, and then taken up in alcohol and precipitated in ether, the ether takes up 11.45 gm. of material or 0.458%.

Suspecting that the drying of bile and solution in alcohol might hydrolyze the fats, bile was extracted directly using a modification of the Roese-Gottlieb 4 method for fat extraction from milk. This method proved very difficult on account of the persistent emulsions that were formed.