Complex Mixture Of Fatty Acids Research Articles

Aqueous Extracts from Hemp Seeds as a New Weapon against Staphylococcus epidermidis Biofilms.

This study investigated the antibiofilm activity of water-soluble extracts obtained under different pH conditions from Cannabis sativa seeds and from previously defatted seeds. The chemical composition of the extracts, determined through GC-MS and NMR, revealed complex mixtures of fatty acids, monosaccharides, amino acids and glycerol in ratios depending on extraction pH. In particular, the extract obtained at pH 7 from defatted seeds (Ex7d) contained a larger variety of sugars compared to the others. Saturated and unsaturated fatty acids were found in all of the analysed extracts, but linoleic acid (C18:2) was detected only in the extracts obtained at pH 7 and pH 10. The extracts did not show cytotoxicity to HaCaT cells and significantly inhibited the formation of Staphylococcus epidermidis biofilms. The exception was the extract obtained at pH 10, which appeared to be less active. Ex7d showed the highest antibiofilm activity, i.e., around 90%. Ex7d was further fractionated by HPLC, and the antibiofilm activity of all fractions was evaluated. The 2D-NMR analysis highlighted that the most active fraction was largely composed of glycerolipids. This evidence suggested that these molecules are probably responsible for the observed antibiofilm effect but does not exclude a possible synergistic contribution by the other components.

Abstract 15134: Joint Associations of Fatty Acids With Inflammation and Lipid Profiles: A Mixture Analysis Approach

Introduction: The human diet consists of a complex mixture of fatty acids with differential effects on cardiovascular health. Saturated fatty acids have been shown to exert a hypercholesterolemic effect, while omega-3 polyunsaturated fatty acids have anti-inflammatory properties. Advanced statistical approaches are needed however to address whether their covarying relationships may contribute to varying outcomes on cardiovascular health. Methods: We used data on adult participants from the 2003-2004 and 2011-2012 National Health and Nutrition Examination Survey. Blood lipid levels were measured in 2,926 participants, and C-reactive protein (CRP) was measured in 1,339 participants. Fatty acids were measured in serum or plasma and analyzed as the percentage of total fatty acids. We used covariate-adjusted quantile g-computation to assess the joint effects of 6 saturated, 6 monounsaturated, and 11 polyunsaturated fatty acids on log-transformed outcomes, as well as examine the relative contribution of each fatty acid to the joint mixture effect. Results: We estimated positive associations between the mixture of saturated fatty acids with total cholesterol and LDL, which was primarily driven by myristic acid and docosanoic acid. The mixture of monounsaturated fatty acids was associated with lower total cholesterol and LDL, but higher CRP with a quartile increase in monounsaturated fatty acids associated with 21.1% (95% CI: 7.9, 35.9) higher CRP. The mixture of omega-6 polyunsaturated fatty acids was positively associated with both total cholesterol and LDL. We found that the mixture of omega-3 polyunsaturated fatty acids was negatively associated with CRP and LDL. A quartile increase in omega-3 fatty acids was associated with -11.6% (95% CI: -18.8, -3.7) lower CRP, and -2.1% (95% CI: -3.6, -0.4) lower LDL. The relationship with CRP was primarily driven by docosapentaenoic n-3 acid and eicosapentaenoic acid, while the relationship with LDL was driven by docosapentaenoic n-3 acid and docosahexaenoic acid. Conclusions: Assessing the complex mixture of fatty acids, we found distinct beneficial relationships between omega-3 fatty acids with inflammation and lipid profiles, with an important role of docosapentaenoic n-3 acid.

Silver ion chromatography for the analysis of trans-fatty acid isomers in humans

More than 65 different fatty acids, including positional and geometric fatty acid isomers, have been reported in humans. These isomers have the same molecular mass and very similar chemical structures but can have very different biological functions. The large number of cis- and trans-isomers in human blood pose analytical challenges and require detailed investigations to appropriately determine their effects on health and changes in the amount and composition in people. Silver ion chromatography, a technology used to separate complex fatty acid mixtures, in combination with an expanded version of Centers for Disease Control and Prevention (CDC) gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) method for fatty acids can effectively separate cis- and trans-fatty acid isomers. This approach has potential for determining comprehensive trans-fatty acid profiles in people.

Valorization of Unconventional Lipids from Microalgae or Tall Oil via a Selective Dual Catalysis One-Pot Approach.

A dual catalysis approach enables selective functionalization of unconventional feedstocks composed of complex fatty acid mixtures with highly unsaturated portions like eicosapentaenoate (20:5) along with monounsaturated compounds. The degree of unsaturation is unified by selective heterogeneous hydrogenation on Pd/γ-Al2O3, complemented by effective activation to a homogeneous carbonylation catalyst [(dtbpx)PdH(L)]+ by addition of diprotonated diphosphine (dtbpxH2)(OTf)2. By this one-pot approach, neat 20:5 as a model substrate is hydrogenated to up to 80% to the monounsaturated analogue (20:1), this is functionalized to the desired C21 α,ω-diester building block with a linear selectivity of over 90%. This catalytic approach is demonstrated to be suitable for crude microalgae oil from Phaeodactylum tricornutum genetically engineered for this purpose, as well as tall oil, an abundant waste material. Both substrates were fully converted with an overall selectivity to the linear α,ω-diester of up to 75%.

Characterization of Synthesized and Commercial Forms of Magnesium Stearate Using Differential Scanning Calorimetry, Thermogravimetric Analysis, Powder X-Ray Diffraction, and Solid-State NMR Spectroscopy

Magnesium stearate is the salt of a complex mixture of fatty acids, with the majority being stearate and palmitate. It has multiple crystalline forms and, potentially, an amorphous form. Magnesium stearate is used in the pharmaceutical manufacturing industry as a powder lubricant, and typically is added at low levels (∼1%) during the manufacturing process and blended for a relatively short time (∼5 min). Proper levels and mixing times are needed, as too short a mixing time or too small a quantity will result in improper lubrication, and too much can negatively impact dissolution rates. The complex mixture of multiple fatty acids and crystalline forms in magnesium stearate leads to variability between commercial sources, and switching between sources can impact both the amount of lubricant and mixing time needed for proper lubrication. In order to better understand the complex nature of magnesium stearate, a variety of analytical techniques were used to characterize both synthesized and commercial magnesium stearate samples. The results show that correlation among differential scanning calorimetry, thermogravimetric analysis, solid-state NMR spectroscopy, and other techniques provides a unique insight into the forms of magnesium stearate. Finally, the ability to monitor form changes of magnesium stearate in an intact tablet using solid-state NMR spectroscopy is shown.

Comparative study of the modulation of fructose/sucrose-induced hepatic steatosis by mixed lipid formulations varying in unsaturated fatty acid content.

BackgroundNon-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in developed countries. NAFLD encompasses a spectrum of diseases, ranging from hepatic steatosis to non-alcoholic steatohepatitis (NASH), cirrhosis, and liver failure. The etiology of NAFLD remains unclear but is thought to relate to increased fatty acid flux within the liver that results in toxic fatty acid metabolite production. One source of increased fatty acid flux is fructose/sucrose-induced hepatic lipogenesis. Current treatment for NAFLD encompasses dietary modifications. However, little scientific evidence exists on which to base many dietary recommendations, especially the intake of different types of carbohydrates and fats. We hypothesized that lipid mixtures of unsaturated fatty acids would inhibit lipogenesis and subsequent hepatic steatosis induced by high carbohydrate diets. The aim of this study was to examine the effects of different complex mixtures of fatty acids upon the development of fructose/sucrose-induced hepatic steatosis.MethodsC57BL/6 mice were randomized to normocaloric chow-based diets that varied in the type of carbohydrate (starch, sucrose, fructose). Animals in each carbohydrate group were further randomized to diets that varied in lipid type (no additional lipid, soybean oil, fish oil, olive/soybean oil, macadamia nut oil). These oils were chosen based upon their content of omega-6 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, omega-9 monounsaturated fatty acids, or omega-7 monounsaturated fatty acids. Fatty acid flux in the liver was determine by assessing hepatic lipid content (steatosis). We also assessed fatty acid levels in the plasma and liver of the animals, hepatic lipogenesis activity, hepatic stearoyl-CoA-1 desaturase activity, and hepatic elongase activity.ResultsAnimals consumed similar amounts of the diets and maintained normal body weights throughout the study. Both sucrose and fructose induced hepatic lipogenesis and steatosis, with fructose being more potent. All mixed lipids similarly inhibited steatosis, limiting lipid content to levels found in the control (starch) animals. Lipogenesis and stearoyl-CoA-1 desaturase activity were increased in the sucrose and fructose groups. Levels of these enzymatic processes remained at baseline in all of the lipid groups.ConclusionThis is the first study to compare various complex lipid mixtures, based upon dietary oils with different types of long-chain fatty acids, upon development of sucrose/fructose-induced steatosis. Both carbohydrate source and lipid content appear important for the modulation of steatosis. Moderate intake of complex lipids with high unsaturated to saturated fatty acid ratios inhibited both lipogenesis and steatosis.

Identification of Subvisible Particles in Biopharmaceutical Formulations Using Raman Spectroscopy Provides Insight into Polysorbate 20 Degradation Pathway.

PurposeTo study composition and heterogeneity of insoluble subvisible particles in Mab formulations resulting from degradation of polysorbate 20 and to develop a better understanding of the mechanisms of polysorbate degradation leading to particle formation.MethodsIn this study, we exploit the potential of Raman microscopy for chemical identification of particles in monoclonal antibody formulations. Through a combination of experiments and density functional theory (DFT) calculations, we identified unique spectral marker bands for insoluble degradation products of polysorbate 20. We first applied our methodology to identify particles in model systems containing complex mixtures of fatty acids and then to subvisible particles in antibody formulations stored at 5°C for several years.ResultsMost of the subvisible particles identified were comprised of mixtures of fatty acids with no observable signal from fatty acid esters consistent with hydrolysis being the predominant degradation mechanism leading to particulate formation under these storage conditions.ConclusionsOur methodology is generally applicable for identification of particles in antibody formulations and, in particular, has the potential to give detailed information about particle heterogeneity and insight into mechanistic aspects of particle formation.Electronic supplementary materialThe online version of this article (doi:10.1007/s11095-015-1670-x) contains supplementary material, which is available to authorized users.

Effects of omega-3 and omega-6 fatty acids on human placental cytokine production

IntroductionDietary supplementation with omega-3 long chain polyunsaturated fatty acids (n-3 PUFAs) may exert benefits in pregnancy through inhibition of placental inflammation. However, studies on the anti-inflammatory effects of n-3 PUFAs in the placenta are lacking. We compared the cytokine responses of human placental explants in vitro after 4 days pre-incubation with either: a) individual n-3 or n-6 PUFAs (20 μM), or b) physiologically relevant combinations of low, medium or high n-3 or n-6 PUFA concentrations. MethodsPlacental cytokine (IL-6 and TNF-α) mRNA expression and protein production were assessed at 4 h and 12 h, respectively. Cytokine and fatty acid concentrations were also measured in placentas delivered at term by women who ingested either low (n = 12) or high (n = 10) amounts of fish/fish oil in the month prior to delivery. ResultsPre-exposure to n-3 PUFAs as individual fatty acids results in reduced placental IL-6 production (P < 0.05), whereas exposure to complex fatty acid mixtures enriched in n-3 PUFAs (high n-3:n-6 ratios) results in a significant stimulation of IL-6 production (P < 0.05). There were no differences in placental n-3 or n-6 PUFA levels between women with either high or low dietary fish oil intake and no differences in cytokine expression. DiscussionIn summary, data from our complex lipid explant model and an observational cohort study do not support a role for n3 PUFAs in the suppression of pro-inflammatory cytokine expression in the human placenta. Results from studies of placental tissues exposed to single n-3 and n-6 PUFAs should be interpreted with considerable caution.

Acaricidal and tyrosinase inhibitory activities of Tagetes verticillata Lag. &amp; Rodr

Tagetes verticillata Lag. & Rod.is an andean plant with ethnobotanical uses in Colombia, but there is not scientific research literature devoted to it. Tetranychus urticae Koch is a highly polyphagous species with 1059 host plants reported worldwide [1]. In this work, we obtained extracts from T. verticillata by percolation at room temperature using as solvents petroleum ether (PET), ethanol (ET) and ethyl acetate (EAT). The acaricidal activity of extracts was measured over adult females and nymphs of T. urticae. Also, egg-hatching inhibition was measured. The tyrosinase inhibitory activity of the extract with the highest acaricidal activity was measured. From PET extract we found significant and increasing mortality through the measuring periods (24, 48 and 72h), reaching mortality peaks for nymphs of 84.4% (1000 µg/mL) and for adults of 68.9% (5000 µg/mL). PET extract also caused 78.6% of inhibition of egg hatching (1000 µg/mL). Using PET extract we carried out a bioguided fractionation, obtaining the most active fraction over the mite. From that fraction we recorded a CL50 of 1162.7 ± 146.8 µg/mL (72h) for adults. Also, that fraction had an IC50 value of 150.7 ± 5.3 µg/mL for tyrosinase inhibitory activity. Using GC-MS, from PBT most active fraction, we identified 2,6-di-t-butyl-octahydroazulene-3-alpha as a major component. Other compounds identified in PBT extract were 9,12,15 octadecatrienoic acid as well as its ethyl ester derivative. It was also possible to identify complex mixtures of fatty acids whose main component was oleic acid. We concluded that the PET extract has a nymph-specific acaricidal activity of T. urticae and an inhibitory activity of egg-hatching. The gradual increase in mortality could be caused by a decrease of mite natural defences, on the basis of the inhibitory activity of tyrosinase found in our research and the role of this enzyme in the biosynthesis of melanin and other defensive substances in arthropods [2].

Validation of the sensitive and accurate quantitation of the fatty acid distribution in bovine milk

A method for the precise analysis of the complex mixture of fatty acids in milk has been developed and validated. The triacylglycerol of nonanoic acid was applied as the internal standard (ISTD) for absolute quantification. Milk lipids were extracted by miniaturised ultrasonication and methylated with trimethylsulfonium hydroxide. Resulting fatty acid methyl esters were determined by gas chromatography with flame ionisation detection giving excellent resolution, including separation of several 18:1 isomers. The low quantitation limit (0.01 mg mL−1 milk) indicates that the sensitivity of the method is sufficient to quantify up to 50 fatty acids, from 4:0 to 23:0. Measurements of precision provided excellent results for different bovine milk samples of different fat content (coefficient of variance: 1.9% and 9.8% for intra- and interday precision, respectively). Recovery averaged 108 ± 3.5%. Evaluation of methods for determining the total fat content showed that gravimetry is no longer needed when using the ISTD.

Marine natural products from the Turkish sponge Agelas oroides that inhibit the enoyl reductases from Plasmodium falciparum, Mycobacterium tuberculosis and Escherichia coli

The type II fatty acid pathway (FAS-II) is a validated target for antimicrobial drug discovery. An activity-guided isolation procedure based on Plasmodium falciparum enoyl-ACP reductase ( PfFabI) enzyme inhibition assay on the n-hexane-, the CHCl 3 - and the aq MeOH extracts of the Turkish marine sponge Agelas oroides yielded six pure metabolites [24-ethyl-cholest-5α-7-en-3-β-ol ( 1), 4,5-dibromopyrrole-2-carboxylic acid methyl ester ( 2), 4,5-dibromopyrrole-2-carboxylic acid ( 3), ( E)-oroidin ( 4), 3-amino-1-(2-aminoimidazoyl)-prop-1-ene ( 5), taurine ( 6)] and some minor, complex fatty acid mixtures ( FAMA– FAMG). FAMA, consisting of a 1:2 mixture of (5 Z,9 Z)-5,9-tricosadienoic ( 7) and (5 Z,9 Z)-5,9-tetracosadienoic ( 8) acids, and FAMB composed of 8, (5 Z,9 Z)-5,9-pentacosadienoic ( 9) and (5 Z,9 Z)-5,9-hexacosadienoic ( 10) acids in ≈3:3:2 ratio were the most active PfFabI inhibitory principles of the hexane extract (IC 50 values 0.35 μg/ml). ( E)-Oroidin isolated as free base ( 4a) was identified as the active component of the CHCl 3 extract. Compound 4a was a more potent PfFabI inhibitor (IC 50 0.30 μg/ml = 0.77 μM) than the ( E)-oroidin TFA salt ( 4b), the active and major component of the aq MeOH extract (IC 50 5.0 μg/ml). Enzyme kinetic studies showed 4a to be an uncompetitive PfFabI inhibitor ( K i: 0.4 ± 0.2 and 0.8 ± 0.2 μM with respect to substrate and cofactor). In addition, FAMA and FAMD (mainly consisting of methyl-branched fatty acids) inhibited FabI of Mycobacterium tuberculosis ( MtFabI, IC 50s 9.4 and 8.2 μg/ml, respectively) and Escherichia coli ( EcFabI, IC 50s 0.5 and 0.07 μg/ml, respectively). The majority of the compounds exhibited in vitro antiplasmodial, as well as trypanocidal and leishmanicidal activities without cytotoxicity towards mammalian cells. This study represents the first marine metabolites that inhibit FabI, a clinically relevant enzyme target from the FAS-II pathway of several pathogenic microorganisms.

Gas–liquid chromatographic method for analysing complex mixtures of fatty acids including conjugated linoleic acids ( cis9 trans11 and trans10 cis12 isomers) and long-chain (n-3 or n-6) polyunsaturated fatty acids : Application to the intramuscular fat of beef meat

The optimisation and validation of a gas–liquid chromatographic (GLC) method using direct saponification with KOH/methanol followed by a derivatization with (trimethylsilyl)diazomethane was carried out trying to overcome all the difficulties posed by the analysis of complex mixtures of fatty acids (FAs) in animal fat tissues. The presented method allowed sensitive, selective and simultaneous determination of a wide range of different FAs, including short-chain FAs, branched-chain FAs and conjugated linoleic acid isomers in the same GLC run along with other well known saturated, monounsaturated and polyunsaturated FAs. To demonstrate the feasibility of the procedure, the total FA profile of beef meat was characterised.

Surface chemical analysis of raw cotton fibres and associated materials

The surface chemical composition of raw unscoured cotton was successfully investigated by the surface analytical techniques X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS). The presence of non-cellulosic material at the fibre surface was established and determined to be a complex mixture of fatty acids, alcohols, alkanes, esters and glycerides. The effect of scouring and bleaching was to reduce the surface concentration of these materials but even after aqueous processing some non-cellulosic material residue was still detected at the fibre surface.

The isolation and characterisation of bacteria with the potential to degrade waxes that cause water repellency in sandy soils

Water repellency in soils is caused by waxy coatings on particles and can seriously limit agricultural production. Bioremediation of these soils, using wax-degrading bacteria isolated from soils and other sources rich in microorganisms, was investigated. Wool wax, a complex mixture of fatty acids and alcohols, was used to select bacteria capable of metabolising hydrophobic compounds. Of the 37 stable isolates, two-thirds were actinomycetes. These organisms are known for their ability to metabolise a wide range of organic compounds. Degradation of waxes associated with soil particles is facilitated by the production of biosurfactants that emulsify hydrophobic compounds. Measurement of biosurfactant production indicated that those isolates that grew best on hydrocarbon were also the most prolific biosurfactant producers. Inoculation of water-repellent soils, under controlled conditions, with the most efficient wax-degrading bacterial isolates resulted in significant improvements in soil wettability.

Improved detection of polyunsaturated fatty acids as phenacyl esters using liquid chromatography-ion trap mass spectrometry

The fatty acid composition of Shewanella pealeana was determined by the analysis of fatty acid methyl esters via gas chromatography-mass spectrometry (GC-MS) and fatty acid 2-oxo-phenylethyl esters via high-performance liquid chromatography-mass spectrometry (LC-MS) combined with ultra violet (UV) detection. There was good agreement between the percentage composition of components determined by GC-MS and LC-UV analyses. However, LC-MS analysis using Atmospheric Pressure Chemical Ionization (APCI) demonstrated dramatically enhanced detection of unsaturated fatty acid 2-oxo-phenylethyl esters. The degree of enhancement was proportional to the degree of unsaturation. Tests with a pure polyunsaturated fatty acid (PUFA) standard gave an absolute detection limit in full scan mode of 200 pg. In samples, the selectivity of MS over UV gave a significantly lower detection limit due to lack of chemical interferences. In ‘Selected Reaction Monitoring’ (SRM) mode, the detection limit was 5 pg. This was essentially independent of whether the sample is a standard or complex mixture of fatty acids. Tandem mass spectrometry was used to support structural information and to enhance the ability to target specific fatty acids. Several PUFAs which were not evident from GC-MS analysis were detected and identified by APCI LC-MS, including some rare or novel PUFAs from S. pealeana and a menhaden oil standard. Detailed analysis of bacterial fatty acid composition by either GC-MS or APCI LC-MS is highly preferable to analysis systems based solely on retention time identification.

SILVER ION HPLC OF p-METHOXYPHENACYL DERIVATIVES OF UNSATURATED FATTY ACIDS. II. CHAIN LENGTH VS. DOUBLE BOND POSITION

The role of the chain-length and double bond position for the separation of positionally isomeric unsaturated fatty acid p-methoxyphenacyl esters by silver ion HPLC was evaluated. A clear effect of chain-length on retention was found, with k” decreasing when the number of carbon atoms in the chain increased. Thus, the resolution was affected both by the chain length and double bond position with the double bond position having the major impact. This allowed for the resolution of complex mixtures of fatty acids that differ in chain length and position of the double bonds by a single chromatographic run. Examples of such separation on model mixtures are presented.

Structural analysis of the lipopolysaccharide from Chlamydophila psittaci strain 6BC.

The lipopolysaccaride of Chlamydophila psittaci 6BC was isolated from tissue culture-grown elementary bodies using a modified phenol/water procedure followed by extraction with phenol/chloroform/light petroleum. Compositional analyses indicated the presence of 3-deoxy-Dmanno-oct-2-ulosonic acid, GlcN, organic bound phosphate and fatty acids in a molar ratio of approximately 3. 3 : 2 : 1.8 : 4.6. Deacylated lipopolysaccharide was obtained after successive microscale treatment with hydrazine and potassium hydroxide, and was then separated by high performance anion-exchange chromatography into two major fractions, the structures of which were determined by 600 MHz NMR spectroscopy as alpha-Kdo-(2-->8)-alpha-Kdo-(2-->4)-alpha-Kdo-(2-->6)-beta-D-GlcpN -(1 -->6)-alpha-D-GlcpN 1,4'-bisphosphate and alpha-Kdo-(2-->4)-[alpha-Kdo-(2-->8)]-alpha-Kdo-(2-->4)-alpha-Kdo-(2- ->6)-beta-D-GlcpN-(1-->6)-alpha-D-GlcpN 1,4'-bisphosphate. The distribution of fatty acids in lipid A was determined by compositional analyses and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry experiments on lipid A and de-O-acylated lipid A. It was shown that the carbohydrate backbone of lipid A is replaced by a complex mixture of fatty acids, including long-chain and branched (R)-configured 3-hydroxy fatty acids, the latter being exclusively present in an amide linkage.

L'analyse des acides gras en électrophorèse capillaire

The analysis of fatty acids by capillary electrophoresis has been expanding over the last ten years. From the first approaches performed by CZE with acids presenting short normal chains, studies become more diversified thanks to the potentialities offered by capillary electrophoresis (use of micelles of various nature, study in non aqueous media). So, analyses of complex mixtures of fatty acids from C 10 to C 24 , with normal and substituted chains have been successfully performed.

Novel di-, tri-, and tetraenoic fatty acids with bis-methylene-interrupted double-bond systems from the sponge Haliclona cinerea.

Unusual fatty acids, with up to 34 carbon atoms and containing one or two bis-methylene-interrupted double-bond systems, have been identified in the sponge Haliclona cinerea from the Black Sea. These include the dienes-5,9-16:2, 7,11-18:2, 9,13-20:2, 13,17-24:2, 15,19-26:2, 17,21-28:2, 19,23-30:2 and 21,25-32:2; trienes-5,9,23-30:3, 5,9,24-31:3, 5,9,25-32:3, and 5,9,27-34:3; and the tetraenes-5,9,19,23-30:4, 5,9,21,25-32:4, and 5,9,23,27-34:4. In addition, 5,9,13-eicosatrienoic acid was present. Many of these do not appear to have been described before, and only 5,9-16:2 and 5,9,23-30:3 are found often in sponges. They were identified by using silver-ion high-performance liquid chromatography to simplify the complex mixture of fatty acids for subsequent analysis by gas chromatography-mass spectrometry as picolinyl ester derivatives. Deuteration with Wilkinson's catalyst in homogeneous solution confirmed the structures. We speculate that the di- and tetraenoic fatty acids arise by chain elongation of 5,9-hexadecadienoic acid, also a major component of the lipids, followed by further insertion of double bonds in the 5 and 9 positions. The trienes may be formed from 9-hexadecenoic acid by similar mechanisms.

Gas chromatography/tandem mass spectrometry as an analytical tool for the identification of fatty acids.

Structures of fatty acids present at very low quantities in mycobacteria are difficult to determine. A commonly used strategy is to introduce heteroatoms into functional groups by chemical means before subjecting them to gas chromatography/tandem mass spectrometry (GC/MS/MS) analysis. Routinely used methods give very low abundance diagnostic ions leading to ambiguities in structural conclusions. GC/MS/MS associated with electron capture ionization of pentafluorobenzyl esters was used to study very complex mixtures of fatty acids from Mycobacterium fallax and M. aurum. The charge-remote fragmentation of fatty acid carboxylate anions was used for structure determination at the nanogram level of a large number of unsaturated, branched, and cyclopropane-containing fatty acids. Some of them have not been observed previously in these Mycobacteria. On the basis of these studies, biosynthetic pathways of unsaturated, branched, and cyclopropane-containing fatty acid are proposed.