Preparation of fatty acid methyl esters and dimethylacetals from lipids with boron fluoride–methanol

Dietary sources of conjugated dienoic isomers of linoleic acid, a newly recognized class of anticarcinogens

http://www.jbc.org/content/241/6/1350.full.pdf

Intermediates and Products of the Biohydrogenation of Linoleic Acid by Butyrivibrio fibrisolvens

Adaptation of a macro-scale method to the micro-scale for fatty acid methyl transesterification of biological lipid extracts

(1960). A Specific and Reasonably Accurate Method for Routine Determination of Plasma Triglyceride. Scandinavian Journal of Clinical and Laboratory Investigation: Vol. 12, No. 1, pp. 1-9.

A specific and reasonably accurate method for routine determination of plasma triglyceride.

Procedures are described for rapid lipase hydrolysis of triglycerides, isolation of the hydrolytic products by TLC and their conversion to methyl esters and fatty acid analysis by GLC. The techniques are applicable to a few mg of triglycerides or fats. Examples of data obtained with purified triglycerides indicate that the specific action of pancreatic lipase for the 1,3 ester groups is nearly absolute and the technique may be used as a criterion of purity of di- and tri-acid triglycerides. Ca. 83% of the palmitic but only 10~12% of stearic and C18 unsaturated acids of commercial lard occur in 2-position.

Pancreatic lipase hydrolysis of triglycerides by a semimicro technique

Methyl esters were prepared from cholesteryl esters, phospholipids, and glycerides in substantially quantitative yields by methanolysis with large excess of sodium or potassium methoxide in absolute methanol. A silicic acid chromatographic adsorption column technique was described, which was effective in separating methyl esters from unsaponifiables such as sterols, pigments, etc., and free acids. Conditions for complete methanolysis of glyceride fats and oils requiring only 5 min. of reflux time were described. Quantitative conversion of fatty acids to methyl esters was accomplished by direct esterification with absolute methanol containing 4% HCL or H2SO4 and by methylation with diazomethane.

Direct conversion of lipid components to their fatty acid methyl esters

Fatty acid composition of component lipides from human plasma and atheromas.

A fresh sample of cows' milk was converted directly to the methyl esters by methanolysis and the esters were fractionated into eleven distilled fractions and an undistilled portion. The latter, which contained the bulk of the polyunsaturated and long chain esters, was further fractionated by adsorption chromatography on a silicic acid column. Each fraction from the distillation and adsorption chromatography was analyzed by gas-liquid chromatography on columns containing polyester stationary phases of different polarity. Twenty-seven minor components, including some not previously reported, were present each in less than 0.1%. The fatty acid distribution of the major components fell within the range generally reported.

Fatty acids of cows' milk. B. Composition by gas-liquid chromatography aided by other methods of fractionation

Milk fat methyl esters were subjected to distillation and silicic acid column chromatography to provide fractions of less complexity for gas-liquid chromatographic analysis. It was still necessary however to employ supplemental techniques for identification. Chromatograms were obtained with polyester columns of different polarity on all the fractions and necessary reference samples. While many of the components were identified in the usual way by plots of relative retention time versus number of carbon atoms, iodine values for total unsaturation and ultraviolet spectrophotometry for conjugated and nonconjugated polyunsaturated acids were essential for positive identification of some components. Similarly, examination by infrared spectrophotometry confirmed the presence or absence of conjugated diene ascis-trans, trans-trans or both. Isolatedtrans or terminal double bonds were also determined in this way. Gas-liquid chromatograms of some fractions showed incompletely resolved peaks attributable to the presence of methyl esters of odd-carbon atom, branched-chain, and unsaturated acids. Hydrogenation and rechromatographing provided more positive determination of the structure of these components. Further confirmation of identity of some peaks on the chromatogram was achieved by collection of the appropriate fractions and examination of the collected material. At least 60 fatty acids were identified, including several not previously reported, such as odd-numbered carbon chain length monoethenoid acids from C15 to C23.

R. W. Riemenschneider

Papers

Pancreatic lipase hydrolysis of triglycerides by a semimicro technique

Direct conversion of lipid components to their fatty acid methyl esters

Fatty acid composition of component lipides from human plasma and atheromas.

Fatty acids of cows' milk. B. Composition by gas-liquid chromatography aided by other methods of fractionation

Fatty acids of cows' milk. A. Techniques employed in supplementing gas-liquid chromatography for identification of fatty acids