William W. Christie

Advances in conjugated linoleic acid research

BIOSYNTHESIS AND METABOLIC PROCESSES Conjugated Linoleic Acid Synthesis within the Gut Microbial Ecosystem of Ruminants Detection of Partial b-Oxidation Products of Conjugated Linoleic Acid Isomers and Their Metabolites in Animals and Humans TECHNIQUES OF DETERMINATION OF INDIVIDUAL ISOMERS Syntheses of Conjugated Linoleic Acids Systematic Analysis of trans and Conjugated Linoleic Acids in the Milk and Meat of Ruminants New Developments in Silver Ion and Reverse Phase HPLC of Conjugated Linoleic Acid Structural Characterization of Conjugated Linoleic Acid Methyl Esters with Acetonitrile Chemical Ionization Tandem Mass Spectrometry DIVERSITY OF CLA Growth Inhibition and Apoptotic Cell Death of Cancer Cells Induced by Conjugated Linoleic Acid Modulatory Properties of Conjugated Linoleic Acid on Inflammation and Immune Function: Cellular and Molecular Mechanisms Conjugated Linoleic Acid in Hypertension Antioxidative Activity of Conjugated Linoleic Acid Determined by ESR EFFECTS OF CLA ISOMERS IN HUMANS An Overview of the Effects of Conjugated Linoleic Acid on Body Weight and Body Composition in Humans Conjugated Linoleic Acid in Healthy and Cancerous Human Tissues Lipid-Lowering Actions of trans-10, cis-12 Conjugated Linoleic Acid in Primary Cultures of Human (Pre)Adipocytes Safety Data on Conjugated Linoleic Acid from Animal Studies: An Overview

Gas Chromatography-Mass Spectrometry Methods for Structural Analysis of Fatty Acids

Procedures for structural analysis of fatty acids are reviewed. The emphasis is on methods that involve gas chromatography-mass spectrometry and, in particular, the use of picolinyl ester and dimethyloxazoline derivatives. These should be considered as complementing each other, not simply as alternatives. However, additional derivatization procedures can be of value, including hydrogenation and deuteration, and preparation of dimethyl disulfide and 4-methyl-1,2,4-triazoline-3,5-dione adducts. Sometimes complex mixtures must be separated into simpler fractions prior to analysis by gas chromatography-mass spectrometry. Silver ion and reversed-phase high-performance liquid chromatography are then of special value. In particular, a novel application of the latter technique, involving a base-deactivated stationary phase and acetonitrile as mobile phase, is described that is suited to the separation of fatty acids in the form of picolinyl ester and dimethyloxazoline derivatives, as well as methyl esters.

Advances in lipid methodology

Analysis of plant lipoxygenase metabolites Separations of molecular species of phospholipids by high-performance liquid chromatography Preparative high-performance liquid chromatography of lipids Structural analysis of fatty acids Analysis of stable isotopes in lipids Reversed-phase high-performance liquid chromatography: general principles and application to analysis of fatty acids and triacylglycerols Some important references in lipid methodology: 1995 and 1996.

Metabolites of conjugated isomers of linoleic acid (CLA) in the rat.

Metabolism of conjugated isomers of linoleic acid (CLA) in rats was studied by feeding high quantities of CLA (180 mg/day) for six days to animals that had been reared on a fat-free diet for two weeks. After this period, animals were sacrificed and liver lipids extracted. High-performance liquid chromatography (HPLC) analyses with UV detection revealed the presence of conjugated polyunsaturated fatty acids in the total liver lipid methyl esters. After isolation by HPLC, three fatty acid metabolites were identified by gas liquid chromatography coupled with mass spectrometry as being C20:3 delta 8,12,14, C20:4 delta 5,8,12,14 and C20:4 delta 5,8,11,13. A higher quantity of C20:4 delta 5,8,12,14 compared to C20:4 delta 5,8,11,13 was observed. These must arise from the elongation and desaturation of 18:2 delta 10,12 and 18:2 delta 9,11, respectively.

Silver ion chromatography of lipids and fatty acids

Silver ion chromatography as applied to the analysis of lipids is reviewed. Thin-layer, column, high-performance liquid and supercritical fluid chromatography in the silver ion mode are included. The lipid types covered are fatty acids, triacylglycerols and complex lipids. Separations are divided into those according to number, geometry and position of double bonds, as well as acyl positional isomers for triacylglycerols. The mechanism of silver ion chromatography is discussed in relation to recent studies using silver ion high-performance liquid chromatographic methodology.

Mass spectra of the picolinyl esters of isomeric mono- and dienoic fatty acids

The picolinyl ester derivatives of the complete series of isomeric octadecenoates, methylene-interrupted octadecadienoates, and of octadec-9-ynoate have been subjected to gas chromatography-mass spectrometry. A fused-silica capillary column, coated with a cross-linked methyl silicone, was used for the separation. Electron impact spectra were determined at 70 eV. Earlier observations with a limited series of model compounds were confirmed, and it was shown that the picolinyl ester derivatives were of almost universal value in the location of double bonds in such isomers. Difficulties of interpretation arose mainly when the double bonds were close to the carboxyl group.

Lipid composition of Spodoptera frugiperda (Sf9) and Trichoplusia ni (Tn) insect cells used for baculovirus infection

The lipid composition of two different insect cell lines from Spodoptera frugiperda (Sf9) and Trichoplusia ni (Tn) which are established cell lines for infection with recombinant baculovirus was analyzed by high‐performance liquid chromatography and gas‐liquid chromatography. The major phospholipids found were phosphatidylcholine and phosphatidylethanolamine, the major mono‐unsaturated fatty acids were oleic acid and palmitoleic acid, the major saturated fatty acid was stearic acid. The cholesterol to phospholipid ratio was demonstrated to be lower than in mammalian cell lines. Infection with a recombinant baculovirus Autographa californica resulted in increased levels of phosphatidylcholine in the insect cells. The baculovirus/insect cell system has become a popular system for heterologous protein production. Functional changes of membrane proteins produced in these two cell lines might be correlated to a different lipid profile of their cellular membranes.

Stereospecific analysis of triacyl-sn-glycerolsvia resolution of diastereomeric diacylglycerol derivatives by high-performance liquid chromatography on silica

The compositions of positionssn-1, 2 and 3 of triacylglycerols can be determined by partial hydrolysis with ethyl magnesium bromide, derivatization of the total products with (S)-(+)-1-(1-naphthyl)ethyl isocyanate and isolation of the diacyl-sn-glycerol urethane derivatives by chromatography on solid-phase extraction columns containing an octadecylsilyl phase. The diastereomericsn-1,2-and 2,3-diacylglycerol derivatives are separated by high-performance liquid chromatography on silica for determination of their fatty acids by gas chromatography. Each step in the process has been evaluated rigorously. The compositions of all three positions can be calculated with good accuracy from the analyses of these compounds and that of the total triacylglycerols. Although the 1,3-sn-diacylglycerol derivatives can also be isolated easily, they do not give reliable results for the composition of positionsn-2 because acyl migration occurs during their generation. The stereospecific analysis procedure has been applied to some plant and animal triacyl-sn-glycerols of commercial and scientific interest, containing predominantly C16 and C18 fatty acids,i.e. safflower, sunflower, olive and palm oils, tallow, egg and rat adipose tissue. The method is not at present suited to the analysis of more complex triacylglycerols, such as milk fat or fish oils, and problems associated with these are discussed.

A comparison of pyrrolidide and picolinyl ester derivatives for the identification of fatty acids in natural samples by gas chromatography-mass spectrometry.

The pyrrolidide and picolinyl ester derivatives of the fatty acids in two natural lipid samples rich in unsaturated fatty acids, pig testis lipids and cod liver oil were satisfactorily resolved on capillary columns of fused silica coated with stationary phases of varying polarity. The picolinyl esters, in particular, when subjected to gas chromatography-mass spectrometry on a column containing a cross-linked methyl silicone, gave distinctive mass spectra, which could be interpreted in terms of both the numbers and positions of the double bonds.

Mass spectrometric determination of positions of double bonds in polyunsaturated fatty acid pyrrolidides

Low resolution mass spectra of pyrrolidides of isomeric octadecadienoic acids and other polyunsaturated straight chain fatty acids are presented and discussed. The spectra of the pyrrolidides contain mainly ions from the polar part of the molecule and give spectra that are specific for each isomer. The interpretation follows, in most cases, the rule developed for monounsaturated fatty acid pyrrolidides.