Identification of methyl-branched fatty acids from the triacylglycerols of subcutaneous adipose tissue of lambs.

A concentrate of branched chain fatty acids (as methyl esters) was prepared from the triacylglycerols of subcutaneous adipose tissue lipids of lambs receiving a carbohydrate-rich (cereal diet). This was accomplished by procedures which allowed the removal of unsaturated components by peroxidation and straight chain saturated components by urea-adduct formation. The concentrate was analyzed by high resolution gas chromatography in combination with mass spectrometry and was shown to consist of a complex mixture of saturated methyl-substituted fatty acids. Methyl substitution occurred on even-numbered carbon atoms (relative to the carboxyl group) and the chain lengths of the acids ranged from 10 to 18 carbon atoms. Acids with one methyl substituent in the fatty acyl chain were most abundant; di-, tri- and tetramethyl-substituted acids were also present. The biosynthesis of these methyl-substituted acids is discussed briefly.

The phytanic acid content of the lipids of bovine tissues and milk.

In three steers which were given grass silage for six months, the content of phytanic acid (i.e. 3,7,11,15-tetramethyl-hexadecanoic acid) in plasma lipid increased to about 8% of the total fatty acids, whereas after this time the proportion in the total fatty acids of liver and heart lipids was about 1%, and only 0.1% in those of kidney lipids; the acid was present in trace amounts in adipose-tissue triglycerides and was apparently absent from brain lipids. In eight lactating cows which were given grass silage for about 3 months, the content of phytanic acid in the total long chain fatty acids of milk and of plasma was 0.7% and 13%, respectively. In the plasma lipids of both steers and lactating cows, phytanic acid constituted a substantial proportion of the total fatty acids of the triglycerides and phospholipids; the acid was present in lowest proportion in the cholesteryl esters.

Micellar solubilization of fatty acids in aqueous media containing bile salts and phospholipids.

1. The solubility of fatty acids in aqueous media containing bile salts alone and in admixture with either lecithin (phosphatidylcholine) or phosphatidylethanolamine was determined. 2. Over the pH range 2-0-7-4, the order of fatty acid solubility in aqueous solutions containing bile salts was linoleic greater than oleic greater than elaidic greater than palmitic greater than stearic. The solubility of each fatty acid increased as the pH of the miceus solutions of bile salts greatly increased the solubility of palmitic acid and stearic acid. 4. In the presence of bile salts and lecithin, the solubility of oleic acid and elaidic acid decreased with increasing pH of the micellar solution, indicating a competitive effect between the fatty acid anions and lecithin. The solubility of linoleic acid increased linearly with lecithin concentration. 5. Phosphatidylethanolamine as an additive to bile salts increased the solubility of both saturated and unsaturated fatty acids in the pH range 2-3-7-4. The effectiveness of phosphatidylethanolamine as an amphiphile was similar to that of lecithin, although at pH 3.0 fatty acid solubility was greater in the presence of phosphatidylethanolamine. 6. The significance of these findings is discussed in relation to the intestinal absorption of fatty acids in sheep.

Influence of the products of phospholipolysis of phosphatidylcholine on micellar solubilization of fatty acids in the presence of bile salts.

1. The solubility of fatty acids in aqueous solutions containing bile salts and lysolecithin at pH values between 2-0 and 7-4 was studied. Both the 1-acyl and 2-acyl isomers of lysolecithin increased the solubility of fatty acids to the same extent, the order of solubility being linoleic greater than oleic greater than elaidic greater than palmitic greater than stearic. 2. The influence of the products of phospholipolysis of lecithin on palmitic acid solubility was determined. On a molar basis, lysolecithin was more effective than were bile salts in promoting the solubilization of the fatty acid. 3. In bile salt solutions in which the phospholipid concentration was constant on a molar basis, in solubility of palmitic acid decreased linearly with the progressive replacement of lecithin by lysolecithin. Palmitic acid was solubilized to the same extent on replacing lecithin with lysolecithin on a constant weight basis. 4. In bile salt solution containing lysolecithin and oleic acid in equimolar amounts, the solubility of palmitic acid was similar to that in bile salt solution containing lecithin in equivalent proportion. 5. The results are discussed in relation to the action of phospholipolytic activity on the intestinal absorption of fatty acids in sheep.

Application of open-tubular column/gas-liquid chromatography to the analysis of complex mixtures of branched-chain fatty acids.

Methyl and butyl esters of branched-chain fatty acids of subcutaneous triacylgycerols from barley-fed lambs were subjected to urea-adduction and the resulting fractions were analyzed as methyl esters by gas-liquid chromatography on wall-coated open-tubular columns. The chromatogram of each fraction was less complex than that of the original and there was evidence to suggest that, in the original mixture of branched-chain acids, components resistant to urea-adduction were present, but their occurrence was obscured in chromatograms by the presence of monomethyl-substituted acids.

The lipids of human pancreas with special reference to the presence of fatty acid methyl esters.

Total lipids were extracted from human pancreas with chloroform-methanol, chloroform-methanol following acidification, and benzene. A similar proportional amount of total lipid was obtained by each procedure. Regardless of the method of extraction (i.e., whether or not methanol was present), a small proportion (about 1%) of the total lipid was found to consist of fatty acid methyl esters. Triglycerides constituted the major fraction (about 80%) of the pancreatic lipids; in addition to methyl esters, the remaining lipids comprised free fatty acids, phospholipids, cholesterol esters, and traces of free cholesterol. In general, each class of lipid had a similar over-all fatty acid composition with palmitic and oleic acids as predominant components. The methyl esters had a relatively high content of linolenic acid, and the free fatty acids contained a notably high proportion of palmitic acid, in each case accompanied by a corresponding decrease in the proportion of oleic acid present.