Mass spectrometry of fatty acid pyrrolidides

Pantoea trifolii sp. nov., a novel bacterium isolated from Trifolium rubens root nodules

A novel bacterium, designated strain MMK2T, was isolated from a surface-sterilised root nodule of a Trifolium rubens plant growing in south-eastern Poland. Cells were Gram negative, non-spore forming and rod shaped. The strain had the highest 16S rRNA gene sequence similarity with P. endophytica (99.4%), P. leporis (99.4%) P. rwandensis (98.8%) and P. rodasii (98.45%). Phylogenomic analysis clearly showed that strain MMK2T and an additional strain, MMK3, should reside in the genus Pantoea and that they were most closely related to P. endophytica and P. leporis. Genome comparisons showed that the novel strain shared 82.96-93.50% average nucleotide identity and 26.2-53. 2% digital DNA:DNA hybridization with closely related species. Both strains produced siderophores and were able to solubilise phosphates. The MMK2T strain was also able to produce indole-3-acetic acid. The tested strains differed in their antimicrobial activity, but both were able to inhibit the growth of Sclerotinia sclerotiorum 10Ss01. Based on the results of the phenotypic, phylogenomic, genomic and chemotaxonomic analyses, strains MMK2T and MMK3 belong to a novel species in the genus Pantoea for which the name Pantoea trifolii sp. nov. is proposed with the type strain MMK2T (= DSM 115063T = LMG 33049T).

Unusual Lipid Components of Legionella gormanii Membranes

Legionella spp. cause Legionnaires’ disease with pneumonia as the predominant clinical symptom. L. gormanii is the second most prevalent causative agent of community-acquired pneumonia after L. pneumophila. The study aimed to characterize the lipidome of L. gormanii membranes and the importance of these analyses in bacterial chemotaxonomy. Lipidomic analyses based on ultra-high performance liquid chromatography-mass spectrometry allowed the detection of individual molecular species of a wide range of L. gormanii membrane lipids contained in the outer (OM) and inner membranes (IM). The lipid profile comprised glycerolipids (triglycerides, diglycerides), phospholipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, cardiolipin), and sphingolipids (ceramides, hexosylceramides). The most abundant lipid fraction in the IM and OM were phospholipids. The lipidomic analysis showed that two independent phosphatidylcholine (PC) synthesis pathways operating in L. gormanii: the PE-methylation (PmtA) pathway and the PC synthase (Pcs) pathway. Comparison of the molecular profile of PC species contained in the lipids of L. gormanii membranes cultured on the medium, with and without exogenous choline, showed quantitative differences in the PC pool. An unusual feature of the L. gormanii lipids was the presence of ceramides and hexosylceramides, which are typical components of eukaryotic cells and a very small group of bacteria. To the best of our knowledge, this is the first report of the occurrence of ceramides in Legionella bacteria.

GC/EI-MS method for the determination of phytosterols in vegetable oils

Sterols are a highly complex group of lipophilic compounds present in the unsaponifiable matter of virtually all living organisms. In this study, we developed a novel gas chromatography with mass spectrometry selected ion monitoring (GC/MS-SIM) method for the comprehensive analysis of sterols after saponification and silylation. A new referencing system was introduced by means of a series of saturated fatty acid pyrrolidides (FAPs) as internal standards. Linked with retention time locking (RTL), the resulting FAP retention indices (RI_FAP) of the sterols could be determined with high precision. The GC/MS-SIM method was based on the parallel measurement of 17 SIM ions in four time windows. This set included eight molecular ions and seven diagnostic fragment ions of silylated sterols as well as two abundant ions of FAPs. Altogether, twenty molecular ions of C₂₇- to C₃₁-sterols with 0-3 double bonds were included in the final method. Screening of four common vegetable oils (sunflower oil, hemp oil, rapeseed oil, and corn oil) enabled the detection of 30 different sterols and triterpenes most of which could be identified.

Fatty acid composition and lipid profiles as chemotaxonomic markers of phytopathogenic fungi Puccinia malvacearum and P. glechomatis

The analysis of the overall fatty acid pattern as well as their distribution in various lipid classes of phytopathogenic fungi Puccinia malvacearum and P. glechomatis are considered as chemotaxonomic biomarkers. Puccinia malvacearum on Alcea rosea and P. glechomatis on Glechoma hederacea collected from plants grown in various localities were analysed to determine their fatty acid composition. Both species synthesised significant amounts of saturated palmitic and stearic acids as well as 9,10-epoxy-octadecanoic acid, which rarely occurs in the nature. Both species synthesised hydroxy FAs including 9,10-dihydroxy octadecanoic acid and long-chain 2-hydroxy fatty acids.2-hydroxy 18:0 and 3-hydroxy 20:0 fatty acids were present only in P. malvacearum spores, and these may be the chemotaxonomic markers of the species. Ultra-high performance liquid chromatography mass spectrometry was performed for a comparative lipidomic analysis of P. malvacearum and P. glechomatis. The results revealed the complexity of molecular lipid species of these fungi. P. malvacearum and P. glechomatis lipids were characterised by the presence of a high number of triglyceride (TG) species. 9,10-epoxy octadecanoic fatty acid was found in TGs. Among the many types of oxidised TGs identified in P. glechomatis lipids, the most abundant species corresponds to TG(22:5+6O_17:0_18:2). P. malvacearum and P. glechomatis produced various ceramide species with different FAs from 14 to 24 chain-length. Unusual lipids like (O-acyl)-ω-hydroxy FA 18:0/18:0 in P. glechomatis and (O-acyl)-ω-hydroxy FA 18:0/20:0 and 18:0/22:0 in P. malvacearum were detected. The analysis of the polar lipid composition showed the presence of phosphatidylcholine and phosphatidylethanolamine as the main phospholipid classes of Puccinia spp. with the highest diversity of molecular species. Other phospholipids phosphatidic acid, phosphatidylglycerol phosphatidylserine and phosphatidylinositol were present in smaller amounts. The diversity of the neutral and polar lipid composition and fatty acid profile of P. malvacearum and P. glechomatis can be used in chemotaxonomic studies.

Secondary metabolites from Garcinia daedalanthera Pierre leaves (Clusiaceae)

Two new glycerol esters, (S)-2-hydroxy-3-(octanoyloxy)propyl tetracosanoate (1) and (S)-3-(((S)-11-acetoxy octadecanoyl)oxy)propane-1,2-diyl diacetate (2), and eight known compounds, docosanedioic acid (3), 2,5-dimethylnonadecane (4), lupeol (5), stigmasterol (6), β-sitosterol (7), heptadecanoic acid (8), hexanedioic acid, 1,6-bis[(2R)-ethylhexyl] ester (9), and 1,3-di-O-[2',2'-di-(p-phenylene)] (10) were isolated from the leaves of Garcinia daedalanthera Pierre, collected from Indonesia. Structural analysis of the isolates was performed using 1 D- and 2 D-NMR, LC- and GC-MS, IR, polarimetry, and UV-visible spectroscopic methods. Cytotoxicity assessments, as well as reactive oxygen species (ROS) analysis of the isolates, were also completed. Lupeol was the only compound found active with an IC₅₀ value of 19.2 µM against HT-29 colon cancer cells. Significant ROS inhibition and induction activity was observed for compounds 4 and 8, respectively.

Scent gland constituents of the Middle American burrowing python, Loxocemus bicolor (Serpentes: Loxocemidae)

Analysis by gas chromatography/mass spectrometry of the scent gland secretions of male and female Middle American burrowing pythons (Loxocemus bicolor) revealed the presence of over 300 components including cholesterol, fatty acids, glyceryl monoalkyl ethers, and alcohols. The fatty acids, over 100 of which were identified, constitute most of the compounds in the secretions and show the greatest structural diversity. They include saturated and unsaturated, unbranched and mono-, di-, and trimethyl-branched compounds ranging in carbon-chain length from 13 to 24. The glyceryl monoethers possess saturated or unsaturated, straight or methyl-branched alkyl chains ranging in carbon-chain length from 13 to 24. Alcohols, which have not previously been reported from the scent glands, possess straight, chiefly saturated carbon chains ranging in length from 13 to 24. Sex or individual differences in secretion composition were not observed. Compounds in the scent gland secretions of L. bicolor may deter offending arthropods, such as ants.

Evolved differences in larval social behavior mediated by novel pheromones

Pheromones, chemical signals that convey social information, mediate many insect social behaviors, including navigation and aggregation. Several studies have suggested that behavior during the immature larval stages of Drosophila development is influenced by pheromones, but none of these compounds or the pheromone-receptor neurons that sense them have been identified. Here we report a larval pheromone-signaling pathway. We found that larvae produce two novel long-chain fatty acids that are attractive to other larvae. We identified a single larval chemosensory neuron that detects these molecules. Two members of the pickpocket family of DEG/ENaC channel subunits (ppk23 and ppk29) are required to respond to these pheromones. This pheromone system is evolving quickly, since the larval exudates of D. simulans, the sister species of D. melanogaster, are not attractive to other larvae. Our results define a new pheromone signaling system in Drosophila that shares characteristics with pheromone systems in a wide diversity of insects.

DOI:http://dx.doi.org/10.7554/eLife.04205.001

The release of chemical signals called pheromones is a common tactic used by animals in many social situations, such as to attract potential mates or to follow trails left by other members of their colony. Larvae of the fruit fly Drosophila melanogaster—a species commonly studied in the laboratory—gather together when sharing a food source and then cooperate in a way that may increase how efficiently they feed. It has been proposed that pheromones coordinate this behavior, but no larval pheromones had been identified.

Mast et al. noticed that Drosophila larvae crawling on a surface tended to occupy areas where other larvae had crawled before. This suggested that larvae had left attractive chemicals on the surface. Mast et al. identified two such substances by analyzing the chemicals left on the surface and then by testing the response of larvae to each compound.

Ultimately, Mast et al. found that a single sensory neuron in the larva is responsible for detecting these attractive chemical signals. Furthermore, two genes called pickpocket23 and pickpocket29 control this response. These genes were previously known for their roles in detecting sex pheromones, and they are members of a diverse family of calcium channel subunits that are involved in detecting multiple ‘sensory modalities’ such as touch and taste. When either pickpocket23 or pickpocket29 are inactivated, larvae ignore the social cues left by their neighbors.

Mast et al. also looked for an evolutionary role for these pheromones. Larvae of a closely related fly species called Drosophila simulans produce a subtly different blend of compounds to D. melanogaster, and this blend is not attractive to any of the species tested. While Drosophila simulans larvae were not attracted to the cues left by their own species, they were attracted to the pheromones produced by Drosophila melanogaster, indicating that they retain the sensory mechanisms to detect and respond to these pheromones. These results suggest that larvae experience a rapidly evolving, complex, pheromone-rich environment that may help them tailor their behavior to survive.

DOI:http://dx.doi.org/10.7554/eLife.04205.002

Metabolite profiling of Schizochytrium sp. by GC-MS, an oleaginous microbial source of biodiesel

The chemical screening carried out on Schizochytrium sp. biomass led the identification of 24 types of organic compounds belonging to n-alkanes, 1-alkenes, 1-alkanols, free fatty acids, methyl and ethyl esters of saturated and unsaturated fatty acids, saturated tri- and diglycerides, unsaturated monoglycerides, wax esters, sterols, triterpenes, and mono- and sesquiterpenes. Moreover, a sample containing fully saturated ethyl biodiesel was obtained experimentally with a yield of 28.72% w/w of the crude extract, and an average chain length of 15.52 carbons. This strain produced no toxins, but showed important nutrients, making it potentially applicable to the field of functional food, and biodiesel production.

Isolation of fucoxanthin and highly unsaturated monogalactosyldiacylglycerol from brown alga Fucus evanescens C Agardh and in vitro investigation of their antitumor activity

Fucoxanthin (FX) and highly unsaturated monogalactosyldiacylglycerol (MGDG) were isolated from the ethanol extract of brown alga Fucus evanescens. Their structures were identified by nuclear magnetic resonance, complemented by electrospray ionization mass spectrometry (ESIMS). MGDG was identified as 1-O-(5Z,8Z,11Z,14Z,17Z-eicosapentanoyl)-2-O-(6Z,9Z,12Z,15Z-octadecatetraenoyl)-3-O-β-D-galactopiranosyl-sn-glycerol. Antitumor activity of these compounds was tested on human melanoma (SK-MEL-28) cells. MGDG and FX inhibited the growth of human melanoma cells in a dose-dependent manner. IC50 values for growth inhibition were 104 and 114 μM, correspondently.

LC/ESI-MS/MS detection of FAs by charge reversal derivatization with more than four orders of magnitude improvement in sensitivity

Quantitative analysis of fatty acids (FAs) is an important area of analytical biochemistry. Ultra high sensitivity FA analysis usually is done with gas chromatography of pentafluorobenzyl esters coupled to an electron-capture detector. With the popularity of electrospray ionization (ESI) mass spectrometers coupled to liquid chromatography, it would be convenient to develop a method for ultra high sensitivity FA detection using this equipment. Although FAs can be analyzed by ESI in negative ion mode, this method is not very sensitive. In this study, we demonstrate a new method of FA analysis based on conversion of the carboxylic acid to an amide bearing a permanent positive charge, N-(4-aminomethylphenyl)pyridinium (AMPP) combined with analysis on a reverse-phase liquid chromatography column coupled to an ESI mass spectrometer operating in positive ion mode. This leads to an ∼60,000-fold increase in sensitivity compared with the same method carried out with underivatized FAs. The new method is about 10-fold more sensitive than the existing method of gas chromatography/electron-capture mass spectrometry of FA pentafluorobenzyl esters. Furthermore, significant fragmentation of the precursor ions in the nontag portion improves analytical specificity. We show that a large number of FA molecular species can be analyzed with this method in complex biological samples such as mouse serum.

Non-methylene interrupted and hydroxy fatty acids in polar lipids of the alga Grateloupia turuturu over the four seasons

Phospholipids (PL) and glycolipids (GL) FA in the edible Rhodophyta Grateloupia turuturu, from Brittany, France, were investigated over four seasons. The major lipid class was GL in all seasons (around 45 %). More than 80 FA occurred in polar lipids, with chains from C12 to C26, identified as methyl esters and N-acyl pyrrolidides by gas chromatography-mass spectrometry (GC-MS). PUFA occurred at up to 47.1 % (summer) in PL, and up to 43.6 % (summer) in GL. The major PUFA were 20:5n-3 (12.2 % in PL and 29.0 % in GL) and 20:4n-6 (25.6 % in PL and 10.4 % in GL). The unusual 18:3n-7 acid was identified in PL up to 2.2 %. Several minor unsaturated FA were identified in PL and are previously unreported in seaweeds, namely 14-tricosenoic, 15-tetracosenoic, 5,11-octadecadienoic and 5,9-nonadecadienoic. Also unprecedented in seaweeds, ten 2-hydroxy and three 3-hydroxy FA occurred mainly in PL, 13.9 % in spring with the 3-hydroxyhexadecanoic acid as the major one (8.1 % winter). Three n-9 monounsaturated 2-hydroxy FA occurred in PL. The 2-hydroxy-15-tetracosenoic acid was characterized as the dimethyl disulfide adduct of its methyl ester. The 2-hydroxy-16-pentacosenoic and 2-hydroxy-17-hexacosenoic acids were identified by comparison of mass spectra and GC mobilities with those of the 2-hydroxy-15-tetracosenoic acid, and of other homogeneous FA series. These rare n-9 monounsaturated 2-hydroxy FA are unprecedented in seaweeds.

Non-methylene-interrupted fatty acids from marine invertebrates: Occurrence, characterization and biological properties

Marine organisms, in particular invertebrates, have proved to be a major source of unique fatty acid (FA) structures originating from unusual biosynthetic pathways. Among them, non-methylene-interrupted (NMI) FA occur in various molluscs in the wide ranges of concentrations (up to 20%), such as the most often encountered 20:2 Delta5,11, 20:2 Delta5,13, 22:2 Delta7,13 or 22:2 Delta7,15. Such NMI FA have also been reported from algae, echinoderms, sponges, tropical rays, and many other invertebrates. The most intriguing marine invertebrates seem to be sponges that commonly contain very long-chain Delta5,9 FA. A third double bond can occur in the NMI FA as reported in some marine organisms, such as 20:3 Delta7,13,16 or 30:3 Delta5,9,23. Lipids of invertebrates from deep-sea hydrothermal and cold-seep vents gave rise to an intense research activity including reports on unprecedented NMI polyunsaturated FA. The bivalve molluscs are able to synthesize de novo the NMI FA but their precise biological interest is presently not well-known, although structural and functional roles in biological membranes have been suggested, in particular a higher resistance to oxidative processes and microbial lipases. Biosynthetic pathways of Delta5,9 FA in sponges were demonstrated up to C(26) FA structures and include particular elongation and desaturation steps. Recently, intense research effort has been conducted to investigate the biomedical potential of these unusual FA. Thus, Delta5,9 FA displayed interesting antiplasmodial activity. The most promising FA topoisomerase I inhibitors to date seem to be the long-chain Delta5,9 FA. This inhibitory activity is probably partially responsible for the toxicity displayed by some of the Delta5,9 FA towards cancer cell lines.

Fatty acid profile, volatiles and antibacterial screening of lipids of the sponge Fasciospongia cavernosa (Schmidt) collected from the bay of Bengal (Orissa coast)

The fatty acid composition as well as the volatiles of a lipophilic extract from the marine sponge Fasciospongia cavernosa (Schmidt) was analyzed. The fatty acids (FA) were characterized by linear saturated fatty acids (33.05 %), branched saturated fatty acids (9.30 %) and mono-unsaturated fatty acids (18.07 %). A significant amount of polyunsaturated fatty acids (PUFA) (30.79 %) was found in the total lipid, which included linoleic acid (18:2 n-6, 11.14 %), 9,12,15-octadecatrienoic acid/?-linolenic acid (18:3 n-3, 1.99 %), dihomo-?-linolenic acid (20:3 n-6, 2.03 %) and arachidonic acid (20:4 n-3, 0.51 %). An antibacterial assay of the lipid extract of F. cavernosa showed broad-spectrum activity against different human and fish pathogens.

Fatty acid biomarkers of symbionts and unusual inhibition of tetracosapolyenoic acid biosynthesis in corals (octocorallia)

Seven zooxanthellae-free species of octocorals (the genera Acanthogorgia, Acabaria, Chironephthya, Echinogorgia, Menella, Ellisella, and Bebryce) and two zooxanthellate octocorals (the genera Paralemnalia and Rumphella) were examined to elucidate their fatty acid (FA) composition. Arachidonic (about 40% of the total FA) and palmitic acids were predominant in all the species studied. Seven furan FA (F-acids) (up to 9.7%) were identified in the azooxanthellate octocorals. The main F-acids were 14,17-epoxy-15-methyldocosa-14,16-dienoic and 14,17-epoxy-15,16-dimethyldocosa-14,16-dienoic acids. In all specimens of Bebryce studeri, C(25-28) demospongic FA (about 20%) were identified. These FA reflect the presence of a symbiotic sponge in B. studeri and can be used as the specific markers for other corals. A significant difference (P < 0.01) between azooxanthellate and zooxanthellate corals was found for odd-chain and methyl-branched saturated FA, 18:1n-7, and 7-Me-16:1n-10; that indicated the presence of an advanced bacterial community in azooxanthellate corals. The zooxanthellate species were distinguished by significant amounts of 18:3n-6, 18:4n-3, and 16:2n-7 acids, which are proposed as the markers of zooxanthellae in soft corals. Contrary to the normal level of 24:5n-6 (9.4%) and 22:4n-6 (0.6%), unexpected low concentrations of 24:5n-6 (0.4%) accompanied by a high content of 22:4n-6 (up to 11.9%) were detected in some specimens. The presence of an unknown factor in octocorals, specific for n-6 PUFA, which inhibited elongation of 22:4n-6 to 24:4n-6, is conjectured.

New method for GC/FID and GC-C-IRMS analysis of plasma free fatty acid concentration and isotopic enrichment

A simple, direct and accurate method for the determination of concentration and enrichment of free fatty acids (FFAs) in human plasma was developed. The validation and comparison to a conventional method are reported. Three amide derivatives, dimethyl, diethyl and pyrrolidide, were investigated in order to achieve optimal resolution of the individual fatty acids. This method involves the use of dimethylamine/Deoxo-Fluor to derivatize plasma free fatty acids to their dimethylamides. This derivatization method is very mild and efficient, and is selective only towards FFAs so that no separation from a total lipid extract is required. The direct method gave lower concentrations for palmitic acid and stearic acid and increased concentrations for oleic acid and linoleic acid in plasma as compared to methyl ester derivative after thin-layer chromatography. The [(13)C]palmitate isotope enrichment measured using direct method was significantly higher than that observed with the BF(3)/MeOH-TLC method. The present method provided accurate and precise measures of concentration as well as enrichment when analyzed with gas chromatography combustion-isotope ratio-mass spectrometry.

Enrichment of eicosapentaenoic acid from sardine oil with Delta5-olefinic bond specific lipase from Bacillus licheniformis MTCC 6824

Lipase derived from Bacillus licheniformis MTCC 6824 was purified to homogeneity by anion exchange chromatography on Amberlite IRA 410 (Cl-) and gel filtration using Sephadex G-100 as judged by denaturing polyacrylamide gel electrophoresis. The purified lipase was used for hydrolysis of triacylglycerol in sardine oil to enrich Delta5-polyunsaturated fatty acids (Delta5-PUFAs) namely, arachidonic acid (5,8,11,14-eicosatetraenoic acid, ARA, 20:4n-6) and eicosapentaenoic acid (5,8,11,14,17-eicosapentaenoic acid, EPA, 20:5n-3). The individual fatty acids were determined as fatty acid methyl esters (FAMEs) by gas-liquid chromatography and gas chromatography-mass spectroscopy as FAMEs and N-acyl pyrrolidides. The enzyme exhibited hydrolytic resistance toward ester bonds of Delta5-PUFAs as compared to those of other fatty acids and was proved to be effective for increasing the concentration of EPA and ARA from sardine oil. Utilizing this fatty acid specificity, EPA and ARA from sardine oil were enriched by lipase-mediated hydrolysis followed by urea fractionation at 4 degrees C. The purified lipase produced the highest degree of hydrolysis for SFAs and MUFAs (81.5 and 72.3%, respectively, from their initial content in sardine oil) after 9 h. The profile of conversion by lipase catalysis showed a steady increase up to 6 h and thereafter plateaued down. Lipase-catalyzed hydrolysis of sardine oil followed by urea adduction with methanol provided free fatty acids containing 55.4% EPA and 5.8% ARA, respectively, after complexation of saturated and less unsaturated fatty acids. The combination of enzymatic hydrolysis and urea complexation proved to be a promising method to obtain highly concentrated EPA and ARA from sardine oil.

Application of Fatty Acids for Chemotaxonomy of Reef-Building Corals

Sixteen scleractinian species of six coral families (Acroporidae, Pocilloporidae, Poritidae, Faviidae, Pectiniidae, and Fungiidae) from Vietnam were analyzed for fatty acid (FA) composition. Except for the Poritidae species, total lipids of the corals had the same set of FAs, about 50% of them being unsaturated acids. Some coral families had high levels of characteristic FAs: 20:3(n-6), 20:4(n-3), and 22:6(n-3) in Pocilloporidae; 18:1(n-9) and 22:6(n-3) in Poritidae; and 18:3(n-6) and 22:5(n-3) in Faviidae. For the first time in hexacorals, unsaturated C(24) FAs (24:1(n-9), 24:2(n-6), 24:2(5,9), 24:3(5,9,17), and 24:4(n-3)) were discovered in the Poritidae species. The highest level of 18:1(n-7), odd-chain and branched FAs (7.5% in total) was detected in Sandalolitha robusta. The data obtained on the contents of ten principal C(18)-C(22) polyunsaturated FAs (PUFAs) for the 16 specimens were combined with data on the 19 reef-building coral specimens investigated previously and subjected to multidimensional scale analysis (MSA). The representative coral families (Acroporidae, Pocilloporidae, Poritidae, Faviidae, Dendrophylliidae, and Milleporidae) were separated by MSA according to the composition of their principal PUFAs. Therefore, PUFAs may serve as chemotaxonomic markers for reef-building corals at the family level. Family-specific compositions of coral zooxanthellae characterized by different PUFA profiles, which affect the PUFA content of whole coral colonies, were supposed to be the probable cause of the discovered chemotaxonomic distinctions between reef-building corals.

Identification of novel alpha-methoxylated phospholipid fatty acids in the Caribbean sponge Erylus goffrilleri

The phospholipid fatty acid composition of the Caribbean sponge Erylus goffrilleri is described for the first time. A total of 70 fatty acids with chain lengths between 13 and 29 carbons were identified in the sponge. Methyl-branched fatty acids predominated in E. goffrilleri suggesting the presence of a considerable number of bacterial symbionts. The novel fatty acids (5Z,9Z)-2-methoxy-5,9-hexadecadienoic acid, (5Z,9Z)-2-methoxy-5,9-octadecadienoic acid, (5Z,9Z)-2-methoxy-5,9-nonadecadienoic acid, and (5Z,9Z)-2-methoxy-5,9-eicosadienoic acid are described for the first time in the literature. In addition, the iso-methyl-branched fatty acids (9Z)-2-methoxy-15-methyl-9-hexadecenoic acid and (5Z,9Z)-2-methoxy-15-methyl-5,9-hexadecadienoic acid, also identified in E. goffrilleri, were identified for the first time in nature. Based on the identified metabolites it is proposed that the unprecedented biosynthetic sequence: i-17:1Delta9 --> 2-OMe-i-17:1Delta9 --> 2-OMe-i-17:2Delta5,9 might be responsible for the biosynthesis of the novel iso-alpha-methoxylated fatty acids in E. goffrilleri.

Fatty Acids in Liver, Muscle and Gonad of three Tropical Rays including Non-Methylene-Interrupted Dienoic Fatty Acids

Scientific investigation of lipids in Elasmobranchs has been conducted mainly on shark species. Because rays seem to be neglected, this study was performed to examine the complete fatty acid (FA) composition with a particular interest for long-chain polyunsaturated FA (PUFA) content in different tissues of three ray species including parts usually discarded. The total FA and PUFA profiles of total lipids were determined in muscle, liver, and gonad of Rhinobatos cemiculus, Rhinoptera marginata, and Dasyatis marmorata, the most often caught ray species from the East Tropical Atlantic Ocean. Fifty FA were characterized as methyl esters and N-acyl pyrrolidides by gas chromatography/mass spectrometry, showing significant levels of 20:5n-3 (EPA) (up to 5.3%) and 22:5n-3 (DPA) (up to 7.3%), high levels of 20:4n-6 arachidonic (ARA) (4.8-8.6% of total FA) and 22:6n-3 (DHA) (up to 20.0%). The results show that muscle, liver and gonad of rays can provide high amounts of essential PUFA, specially DHA, for direct human nutrition or the food processing industry. High proportions of DHA were particularly found in all samples of R. cemiculus (11.6-20.0%), and in muscle and liver of D. marmorata (11.1-16.1%). Regarding the high amounts of (n-3) PUFA, this study shows that these rays deserve a better up-grading, including the normally discarded parts, and describes the occurrence of unusual NMID FA in all tissues studied. Five non-methylene-interrupted dienoic fatty acids (NMID FA) (0-3.4%) were reported, including previously known isomers, namely 20:2 Delta7,13, 20:2 Delta7,15, 22:2 Delta7,13, 22:2 Delta7,15, and new 22:2 Delta6,14. These acids are quite unusual in fish and unprecedented in rays. The 22:2 Delta6,14 acid occurred in gonads of male specimens of R. cemiculus at 2.9%.

Novel cyclopropane fatty acids from the phospholipids of the Caribbean sponge Pseudospongosorites suberitoides

The cyclopropane fatty acids 17-methyl-trans-4,5-methyleneoctadecanoic acid, 18-methyl-trans-4,5-methylenenonadecanoic acid, and 17-methyl-trans-4,5-methylenenonadecanoic acid were characterized for the first time in nature in the phospholipids (mainly PE, PG and PS) of the hermit-crab sponge Pseudospongosorites suberitoides. Pyrrolidine derivatization was the key in identifying the position of the cyclopropyl and methyl groups in the acyl chains and (1)H NMR was used to determine the trans stereochemistry of the cyclopropane ring. The phospholipids from the sponge also contained an interesting series of iso-anteiso Delta(5,9) fatty acids with chain-lengths between 17 and 21 carbons, with the fatty acids (5Z,9Z)-18-methyl-5,9-nonadecadienoic acid and the (5Z,9Z)-17-methyl-5,9-nonadecadienoic acid being described for the first time in sponges. The anteiso alpha-methoxylated fatty acid 2-methoxy-12-methyltetradecanoic acid was also identified for the first time in nature in the phospholipids of this interesting marine sponge. The novel cyclopropyl fatty acids could have originated from the phospholipids of a cyanobacterium living in symbiosis with the sponge.

Synthesis and mass spectrometry of benzoxazoline, dimethyloxazoline and 4-phenyloxazoline derivatives of polyunsaturated fatty acids

Cyclic nitrogen moieties have proved to be of great value for the mass spectrometric location of double bonds in polyunsaturated fatty acids. However, their synthesis has traditionally required long reaction times and/or high temperatures. Recently, we introduced a one-pot, high-yield, mild and efficient method for the synthesis of various fatty acid amide derivatives. We have now extended this procedure to include the synthesis of benzoxazoline, dimethyloxazoline and 4-phenyloxazoline analogs of a series of fatty acids containing 18 to 22 carbon atoms and 0 to 6 double bonds. A comparison of the mass spectral properties of the three derivatives of these saturated and unsaturated fatty acids is described.

Lipid class and fatty acid composition of the boreal soft coral Gersemia rubiformis

Total lipid, phospholipid, and FA composition and distribution of FA between polar lipids (PL) and neutral lipids (NL) were investigated in the boreal soft coral Gersemia rubiformis from the Bering Sea. The total lipids were mostly hydrocarbons and waxes (33.7%) and PL (33.1%). The content of monoalkyldiacylglycerols (9.7%) exceeded the content of TAG (6.7%). PC and PE constituted 31.4% and 25.6% of total phospholipids, respectively. Principal FA were 16:0, 16:1n-7, 18:0, 18:1n-9, 18:1n-7, 20:1n-7, 20:4n-6, 20:4n-3, 20:5n-3, 22:5n-3, 22:6n-3, 24:5n-6, and 24:6n-3. Most n-6 PUFA (52% of total FA) were associated with the PL fraction; this was especially true for arachidonic and tetracosapentaenoic acids. The NL were enriched with mono-, di-, trienoic, and n-3 PUFA. The variation in EPA levels in both NL and PL suggests an origin of this acid from lipids of diatoms consumed by the corals.

Fragmentation of negative ions from carbohydrates: part 2. Fragmentation of high-mannose N-linked glycans

[M + NO3]- And [M + (NO3)2]2- ions were produced by electrospray from neutral high-mannose ([Man](5-9)[GlcNAc]2, [Glc](1-3)[Man](4-9)[GlcNAc]2) N-linked glycans and their 2-aminobenzamide derivatives sprayed from methanol:water containing ammonium nitrate. Low energy collision-induced decomposition (CID) spectra of both types of ions were almost identical and dominated by cross-ring and C-type fragments, unlike the corresponding spectra of the positive ions that contained mainly B- and Y-type glycosidic fragments. This behavior could be rationalized by an initial proton abstraction from various hydroxy groups by the initially-formed anionic adduct. These negative ion spectra were more informative than the corresponding positive ion spectra and contained prominent ions that were diagnostic of structural features such as the composition of individual antennas that were not easily obtainable by other means. C-ions defined the sequence of the constituent monosaccharide residues. Detailed fragmentation mechanisms are proposed to account for many of the diagnostic ions.

A new charge-associated mechanism to account for the production of fragment ions in the high-energy CID spectra of fatty acids

A new mechanism, termed a charge-assisted process, is proposed as an additional mechanism to the charge-remote process to account for ions of the [M - CnH2n+2] series found in the positive and negative high energy CID spectra of fatty acids and related compounds when ionized as closed-shell ([M - H]- or [M + X]+) species. The new mechanism is based on that commonly invoked to account for similar ions in the electron-impact spectra of derivatized fatty acids whereby the positive charge on the derivative abstracts a hydrogen atom from various positions of the alkyl chain to leave a radical that initiates a radical-induced cleavage of the chain. It is proposed that in the high energy CID spectra of closed-shell ions, similar hydrogen migrations occur but unpairing of electrons is avoided by charge transfer to the alkyl chain. This charge then initiates a concerted cleavage of the chain to give an allylic carbonium (positive ion spectrum) or carbanion (negative ion spectrum). The mechanism avoids the need to involve radicals or loss of hydrogen atoms from even-electron (closed shell) ions and provides a driving force for the reaction, namely, the formation of ions with a stabilized charge. An extension of the mechanism is also proposed to account for the formation of odd-electron ions from these compounds. The charge-assisted mechanism does not rule out the occurrence of other mechanisms that have been accepted for many years but provides an alternative process that can account for some spectral features which were difficult to explain earlier.

Isolation of 2-methyl branched unsaturated very long fatty acids from marine sponge Halichondria panicea and identification of them by GC–MS and NMR

In order to study the biomarker fatty acids of symbionts in the marine sponge Halichondria panicea, purification and structural identification of two new 2-methyl branched monoenoic very long fatty acids (2-Me-24:1 n-7 and 2-Me-26:1 n-9) were performed for the first time. These acids amounted to 7.1% of total sponge FAs, but our attempts to determine their structures by one-step GC-MS analysis were unsuccessful because of low yields of the correspondent N-acyl pyrrolidide derivatives. Silver-ion thin-layer chromatography isolated enriched fractions of monoenoic fatty acids extracted from the sponge. Further purification of unknown fatty acid methyl esters was carried out by reversed-phase high-performance liquid chromatography. Determination of the chain length, degree and position of unsaturations was achieved by gas chromatography-mass spectrometry on methyl esters and dimethyldisulfide adducts. Structures, position of methyl substitution, and double bonds cis isomery were confirmed by 1H nuclear magnetic resonance.

Phospholipid fatty acids and sterols of two Cinachyrella sponges from the Saudi Arabian Red Sea: comparison with Cinachyrella species from other origins

Phospholipid class compositions, fatty acids and sterols of the sponges Cinachyrella alloclada and C. kükenthali from the Saudi Arabian Red Sea were studied and compared with previous results for other Cinachyrella spp. collected in Senegal (East Atlantic) and New Caledonia (West Pacific). More than 50 fatty acids were identified as methyl esters and N-acyl pyrrolidides in each phospholipid mixture by GC/MS. Six fatty acids not hitherto found in nature were identified, namely 17-methyltetracosanoic in C. kükenthali and 18-methyltetracosanoic, 18-methylpentacosanoic, 18-methylhexacosanoic, 18,24-dimethyl-hexacosanoic and 6-bromo-5,9-nonacosadienoic acids in C. alloclada. Approximately 20 Delta 5,9 unsaturated fatty acids were found, including three 6-brominated acids. The presence of bacteria was evidenced by the relatively high proportions of phosphatidylglycerol and high levels of branched short-chain fatty acids. A total of 20 free 3beta-hydroxysterols were found by GC/MS, including clerosterol in relatively high amounts and gorgosterol in low amounts. The latter sterol has not been reported to date in a sponge. Comparisons with Cinachyrella species from other geographical areas show marked differences for both phospholipid fatty acid and sterol compositions.

Triacylglycerol and phospholipid fatty acids of the silverleaf whitefly: composition and biosynthesis

The identification and composition of the fatty acids of the major lipid classes (triacylglycerols and phospholipids) within Bemisia argentifolii Bellows and Perring (Homoptera: Aleyrodidae) nymphs were determined. Comparisons were made to fatty acids from the internal lipids of B. argentifolii adults. The fatty acids, as ester derivatives, were analyzed by capillary gas chromatography (CGC) and CGC-mass spectrometry (MS). All lipid classes contained variable distributions of eight fatty acids: the saturated fatty acids, myristic acid (14:0), palmitic acid (16:0), stearic acid (18:0), arachidic acid (20:0); the monounsaturated fatty acids, palmitoleic acid (16:1), oleic acid (18:1); the polyunsaturated fatty acids, linoleic acid (18:2), linolenic acid (18:3). Fourth instar nymphs had 5-10 times the quantities of fatty acids as compared to third instar nymphs and 1-3 times the quantities from adults. The fatty acid quantity differences between fourth and third instar nymphs were related to their size and weight differences. The percentage compositions for fatty acids from each lipid class were the same for the pooled groups of third and fourth instar nymphs. For nymphs and adults, triacylglycerols were the major source of fatty acids, with 18:1 and 16:0 acids as major components and the majority of the polyunsaturated fatty acids, 18:2 and 18:3 were present in the two phospholipid fractions, phosphatidylethanolamine and phosphatidylcholine. Evidence was obtained that whiteflies indeed synthesize linoleic acid and linolenic acid de novo: radiolabel from [2-(14)C] acetate was incorporated into 18:2 and 18:3 fatty acids of B. argentifolii adults and CGC-MS of pyrrolidide derivatives established double bonds in the Delta(9,12) and Delta(9,12,15) positions, respectively.

Lack of stearoyl-CoA desaturase-1 function induces a palmitoyl-CoA Delta6 desaturase and represses the stearoyl-CoA desaturase-3 gene in the preputial glands of the mouse

The mouse preputial gland (PG), a specialized sebaceous structure, is rich in wax esters, triglycerides, and alkyl-2,3-diacylglycerol. We have found that the mouse PG expresses the three gene isoforms (SCD1, SCD2, and SCD3) of the Delta9 stearoyl-CoA desaturase enzyme that catalyzes the biosynthesis of monounsaturated fatty acids mainly, C16:1n-7 and C18:1n-9. However, mice with a targeted disruption in the SCD1 isoform (SCD1(-/-)) have undetectable SCD3 mRNA expression in the PG while the expression of SCD2 isoform was not altered. The levels of C16:1n-7 were reduced by greater than 70% while that of C18:1n-9 were reduced by 28%. The content of the C16:1n-10 (Delta6 hexadecenoic acid) isomer and a major fatty acid of the PG was increased by greater than 2-fold, mainly in the wax ester fraction of the SCD1(-/-) mouse. We demonstrate that the increase in C16:1n-10 is due to induction of a specific palmitoyl-CoA Delta6 desaturase activity. Testosterone administration to the SCD1(-/-) mouse induced SCD3 mRNA expression and resulted in an increase in the Delta9 desaturation of 16:0-CoA, but not of 18:0-CoA. These observations demonstrate that loss of SCD1 function alters the expression of SCD3 and reveal for the first time the presence and regulation of a palmitoyl-CoA Delta6 desaturase enzyme in mammals.