Fatty acid analysis in phosphatidylethanolamine subclasses of human erythrocyte membranes by high-performance liquid chromatography

Molecular species of glycerophospholipids and sphingomyelins of human erythrocytes: improved method of analysis

This study reports the application of modern methods of molecular species analysis in determination of the structure of both major and minor glycerophospholipids and sphingomyelins of human erythrocytes. Individual phospholipid classes were resolved from total lipid extracts by thin-layer chromatography. Diradylglycerols were released by phospholipase C and converted into trimethylsilyl ethers, which were resolved into the alkenylacyl, alkylacyl and diacylglycerol subclasses by normal phase high performance liquid chromatography. Molecular species of diradylglycerols and ceramides were quantitated according to carbon and double bond number by gas liquid chromatography using a fused silica capillary column wall-coated with bonded RTx-2330. The molecular species of ceramides were determined by GC/MS. The diradyl glycerophosphocholines contained 93.0% diacyl, 4.6% alkylacyl and 2.5% alkenylacyl, while the diradyl glycerophosphoethanolamines were made up of 48.8% diacyl, 47.8% alkenylacyl and 3.4% alkylacyl subclasses. Analysis of the molecular species showed that the long chain polyunsaturated acids were mainly combined with C16 in all diradyl GPC subclasses and in diacyl GPE, while in the alkylacyl and alkenylacyl GPE and in diacyl glycerophosphoinositol and diacyl glycerophosphoserine they were combined mainly with C18 saturated fatty chains. In addition to the C16 and C18 alkyl and alkenyl, the ether fractions also contained significant proportions of C20, C22 and C24 chains. The molecular species of the ceramide moieties of the SPH were made up largely of mono- and diunsaturated species. Over 200 molecular species were identified and quantitated in a representative sample of human red blood cells.

Determination of fatty acids as phenacyl esters in rat adipose tissue and blood vessel walls by high-performance liquid chromatography

Twenty-two biologically relevant (6:0-22:6) saturated, monounsaturated and polyunsaturated fatty acids were separated by reversed-phase high-performance liquid chromatography after derivatization with phenacyl bromide. An optimal resolution of the critical combinations linolenic-myristic, docosahexaenoic-palmitoleic-arachidonic and palmitic-oleic acids and cis and trans isomers of octadecenoic (n9) and octadecadienoic (n9, 12) acids was achieved by continuous gradient elution with methanol-acetonitrile-water. Elution of mixtures of 6:0-22:1 fatty acids was completed within 80 min at a flow-rate of 1 ml/min. By the use of UV detection at 242 nm the detection limits for short- and long-chain fatty acids were found to be about 0.8 and 12 ng per injection, respectively. Linearity was tested up to 100 ng. The method was applied to the determination of fatty acids in rat adipose tissue and blood vessel walls of animals fed hydrogenated fat diets. The results are comparable to those obtained by gas chromatography and surpass the latter for the resolution of oleic and elaidic acids.

A one-vial method for routine extraction and quantification of free fatty acids in blood and tissue by HPLC

A one-vial procedure has been developed to quantify free fatty acids in human blood serum and rat heart tissue. To allow routine analysis the system has been constructed to allow simultaneous processing of nine samples (Praechromat). The free fatty acids are extracted with Freon 11 and then derivatized to coumarin esters prior to HPLC. The Freon 11 extraction of the free fatty acids is rapid and complete. Neither hydrolytic degradation of natural fatty acid esters nor oxidative damage of unsaturated fatty acids was observed. Fifteen free fatty acids (FFA) were routinely quantified by isocratic elution with high reproducibility (SD less than 4%) and good recovery (0.1 mM FFA: 98-100%, 0.02 mM: 91-105%). The free fatty acids could be determined in the range from 20 pmol to 20 nmol.