Diacyl Glyceryl Ethers Research Articles

Unusual Ether Lipids and Branched Chain Fatty Acids in Sea Cucumber (Cucumaria frondosa) Viscera and Their Seasonal Variation.

The sea cucumber, Cucumaria frondosa, is harvested primarily for its muscular bands and body wall. Development of a nutraceutical product based on lipid recovered from its viscera would give commercial value to the entire organism; however, such development requires knowledge of the lipid and fatty acid (FA) profiles of the viscera. Here, we describe the lipid and FA composition of viscera recovered from C. frondosa harvested in coastal waters in the northwest Atlantic, taking into account variation due to harvest season. We found highest lipid content at ~29% in winter, with diacylglyceryl ethers (DAGE) comprising ~55% of the total lipid mass and triacylglycerols (TAG), phospholipids (PL) and monoacylglycerol ethers (MAGE) at 5–25% each. The branched chain FA, 12-methyltetradecanoic acid (12-MTA), represented 42% of total FA mass in DAGE. In summer, lipid content was lower at 24% and TAG was the dominate lipid, with proportions more than double that found in winter (45% vs. 20%); DAGE in summer dropped to ~30% of total lipids. In TAG, 12-MTA was much lower than found in DAGE in winter, at only 10% but eicosapentaenoic acid (EPA) content was ~20%, which brought the total EPA% to 28% of total FA—the highest among all three seasons. There was little effect of season on MAGE or PL proportions. These data can help harvesters maximize catch efforts in terms of lipid yield and profile.

Floral origin modulates the content of a lipid marker in Apis mellifera honey

The compound DAGE (DiAcyl Glyceryl Ether, 1-stearyl-2,3-dioleoyl glycerol), present in Apis mellifera honey, is a lipidic entomological marker secreted by the salivary glands of worker bees. Its content was determined by NMR, analyzing the organic extracts of a number of Italian honeys of different floral typology. We have found that the DAGE content is related to the botanical origin of honey. This dependence on floral typology was further confirmed by a linear correlation (R2 > 0.83) observed between the content of DAGE and the enzymatic activity of invertase and diastase in honey. Also these enzymes originate from bee salivary secretions and their concentrations in honey are known to depend on the floral source. DAGE content appears to be a sensitive parameter to some forms of honey manipulations, as indicated by the results of artificial bee-feeding experiments. This suggests its possible use as indicator of honey authenticity.

Characterization and potential strategies for the valorisation of the Southwest Atlantic butterfish (Stromateus brasiliensis)

The waste of fish resources constitutes a serious environmental problem that must be avoided. The valorisation of by-catch species and decreasing the discard rate constitute a more efficient and sustainable use of these marine biomasses. In this work, we characterize and propose different potential uses for Stromateus brasiliensis, another frequently discarded (≥ 90%) and poorly studied by-catch species captured in the South Atlantic Ocean (FAO 41) by trawler fishing fleets. Furthermore, in the case of this species, freezing and frozen storage of the whole fish is the only strategy currently employed for its exploitation. The results revealed that muscle from S. brasiliensis presented a high content of polyunsaturated fatty acids (20.34%) and that the concentrations of both total diacyl glyceryl ethers (2.41%) and heavy metals (Hg 0.038, Pb 0.006 and Cd 0.018 mg/kg) were below the established limits for safe human consumption. Likewise, the protein hydrolysates proved to be a good source of amino acids for human consumption or animal feeding. Minced muscle blocks could be made by a mechanical separation process of the flesh, and the composition of minced muscle did not differ much from that of the whole fish. Furthermore, this process allows the incorporation of cryoprotectants and antioxidants to extend the frozen shelf life of this fatty fish. An extraction process from mechanically mixed skin and bones yielded a good source of collagen that should not be neglected.

Lipase catalyzed glycerolysis of ratfish liver oil at stirred tank basket reactor: A kinetic approach

Abstract The kinetics of the lipase (Novozym 435) catalyzed glycerolysis of ratfish liver oil has been studied at pilot plant scale. A model derived from a generalized Michaelis–Menten mechanism was developed to describe the rates of disappearance of triacylglycerols and diacylglyceryl ethers. Positive discrimination of the immobilized lipase against diacylglyceryl ether was accurately determined in the different data sets studied. More than 1.5 times faster glycerolysis of triacylglycerol compared to that of diacylglyceryl ethers was observed in each set of experiments investigated. Reutilization of the same batch of the biocatalysts was carried out in a stirred tank basket reactor to evaluate the enzyme inactivation. A first-order model for deactivation of the lipase was fit to the data sets. Three different sets of enzymatic glycerolysis were carried out. In all cases rapid inactivation of the immobilized lipase was observed. The half life of Novozym 435 under the glycerolysis conditions studied was approximately 145 h which indicates a deleterious effect of the reaction conditions assayed on lipase activity. After 5 lipase reutilizations of 24 h each, lipase was washed with hexane/ethanol 50/50 w/w but original lipase activity could not be fully restored.

Lipids from the marine world: Perspectives of an organic chemist

This report describes synthesis of novel structured triacylglycerols (TAGs) and diacylglyceryl ethers (DAGEs) of the 1‐O‐alkyl‐sn‐glycerol type constituting EPA and DHA as the sole fatty acids. One of two TAGs was comprised of a pure EPA located at the 1,3‐positions with pure DHA at the 2‐position and the other had it reversed with a pure DHA at the 1,3‐positions and pure EPA at the 2‐positions. The similarly structured DAGEs were derived from chimyl‐, batyl‐, and selachyl alcohols constituting pure EPA at their sn‐3 position with pure DHA at the sn‐2 position as well as the opposite composition with pure DHA at the sn‐3 position and EPA at the sn‐2 position, the total of six such DAGE products. The syntheses of these compounds were brought about by a two‐step chemoenzymatic process involving a highly regioselective immobilized Candida antarctica lipase to incorporate EPA or DHA activated as acetoxime esters exclusively into the 1,3‐positions of glycerol and the sn‐3 position of the 1‐O‐alkyl‐sn‐glycerols. The second PUFA acyl groups were subsequently introduced to the remaining 2‐positions by EDCI coupling agent to accomplish the title compounds highly efficiently in very high to excellent yields (86–92%).Practical applications: The work described is based on a previously reported methodology to introduce n‐3 PUFAs activated as oxime esters exclusively into the terminal 1,3‐positions of glycerol and 1‐O‐alkyl‐sn‐glycerols to prepare reversed structured TAGs and DAGEs by use of immobilized Candida antarctica lipase. The methodology is ideal for introducing isotopically labeled fatty acids into predetermined positions of TAGs and DAGEs.Novel structured triacylglycerols (TAGs) and diacylglyceryl ethers (DAGEs), constituting EPA and DHA as the sole fatty acids, were obtained by a two‐step chemoenzymatic synthesis comprised of an exclusive incorporation of EPA or DHA, activated as acetoxime esters, into the terminal positions of glycerol and 1‐O‐alkyl‐sn‐glycerols by use of immobilized Candida antarctica lipase, and a subsequent introduction of a second PUFA acyl group to the remaining 2‐positions by EDCI coupling agent.

Entomological authentication of stingless bee honey by 1H NMR-based metabolomics approach

The high value of stingless bee honey, better known as pot-honey, offers an incentive to fraud and requires new analytical methods to guarantee the entomological origin. In this research, Geotrigona-Trigona, Melipona, Scaptotrigona, and Apis mellifera Ecuadorian honeys were analyzed. Orthogonal projection to latent structure-discriminant analysis (OPLS-DA) built on 1H NMR data obtained by both water dilution and chloroform extracts spectra, conveyed to successful entomological discrimination. The metabolic fingerprints of these different types of honeys are unique. The most important findings are specific marker signals of entomological origin in chloroform extracts: metabolites deriving from the cerumen secreted by the same bees are present and may be considered as the bee species signature on honey. Furthermore, the endogenous diacylglyceryl ether is recognized as the key marker of pot-honey adulteration with Apis mellifera honey.

Characterization of Markers of Botanical Origin and Other Compounds Extracted from Unifloral Honeys

The possibility of tracing the botanical and geographical origin of products such as honey has become more important because of market globalization. As a consequence, numerous analytical methods have been applied to the determination of honey authenticity. The scope of the present work is to chromatographically purify and characterize 23 compounds from organic extracts of unifloral (chestnut, linden, orange, acacia, eucalyptus, honeydew) and polyfloral honeys. Of these compounds, 17 were identified as specific markers and were used for botanical discrimination in a previous study based on multivariate statistical analysis of proton nuclear magnetic resonance ((1)H NMR) data. Together with the botanical markers, 6 other substances were isolated and characterized using NMR and mass spectrometry. These phytochemicals belong to several classes, that is, terpenes, organic acids, flavonoids, and others. For the first time, a diacylglyceryl ether and 5 other compounds present in different types of honey were identified and characterized.

Long-Term Treatment with a Health Product (Squina Diacylglyceryl Ether) Enhances Innate and Adaptive Immunity in Mice

This study aimed to investigate the effects of a health product Squina (Diacylglyceryl Ether) (DAGE) on innate and adaptive immunity in mice. Both ex vivo/ in vivo mouse models and an in vitro system using cultured mouse splenocytes were recruited for the assessment of innate and adaptive immunity. For the innate immune response, DAGE extract treatment enhanced the LPS-induced IL1-β secretion by activated macrophages in vitro and long-term DAGE treatment (0.18 and 1.8 g/kg × 20 doses) elevated the phagocytic activity of macrophages, as well as natural killer cell activity in mice. The DAGE-induced increase in macrophage phagocytic and natural killer cell activities were accompanied by the suppression of tumor growth in Sarcoma-180 cell-inoculated mice. For the adaptive immune response, long-term DAGE treatment enhanced the splenocyte index and concanavalin A- stimulated proliferation ex vivo in mice. Consistently, the incubation with DAGE extract potentiated the concanavalin A-stimulated proliferation in mouse splenocytes in vitro. In conclusion, the results show that long-term DAGE treatment produces stimulatory effects on both innate and adaptive immunity in mice.

Lipid composition and partitioning of deepwater chondrichthyans: inferences of feeding ecology and distribution

The composition of lipids and fatty acids was determined for the livers, muscle, pancreas, kidney and stomach fluids of deepwater chondrichthyan species (including 11 squaliformes, 3 chimaeriformes, 1 hexanchiforme and 3 carcharhiniformes) caught as bycatch from continental waters off south-eastern Australia. The lipid class, fatty acid and fatty alcohol composition differed markedly in each tissue and in each species. The lipid and fatty acid composition of large, lipid-rich (38–70% wet weight, ww) livers demonstrated the multifunctional role of this organ in: lipid distribution, storage and biosynthesis, and buoyancy regulation. In the liver, the importance of certain lipids (including squalene, diacylglyceryl ethers, triacylglycerols and to a lesser extent wax esters) as mediators of buoyancy varied according to lifestyle and habitat. Less variability was observed in the muscle profiles, characterized by low lipid content ( 70%). The lipid and fatty acid profiles of the kidney and pancreas showed the highest intraspecific variability, suggesting these organs also have complex roles in lipid storage and metabolism. Overall intra- and interspecific differences in the tissue fatty acid profiles could be related to differences in a number of factors including phylogeny, habitat (depth), buoyancy regulation and diet and presumably also reflect different ecological roles. The lipid and fatty acid profiles are the first published for Rhinochimaera pacifica, Chimaera lignaria and Figaro boardmani and the first to demonstrate interspecific variation in lipid profiles of various tissues of deepwater chondrichthyans. The application of multivariate analysis to lipid class and fatty acid tissue profiles in chondrichthyans inferred dietary differences and metabolic preferences between species and habitats. These results have important implications for the future use of fatty acids as dietary tracers in chondrichthyan research.

Lipid Classes and Fatty Acid Composition of the Tropical Nudibranch Mollusks Chromodoris sp. and Phyllidia coelestis

Two nudibranch mollusks, Chromodoris sp. and Phyllidia coelestis, collected from tropical waters of the Northwestern Pacific, were analyzed for lipids. The aim of this study was to fill the gap in knowledge of lipid biochemistry of mollusks. Phospholipids (PL) were the dominating lipid class followed by sterols (13%). Neutral lipids were not detected in Chromodoris sp. By contrast, P. coelestis contained TAG, diacylglyceryl ether, long chain alcohol and esters of sterols. Among PL, PC was predominant (about 50%); PE, PS and CAEP were almost in equal proportions. Sixty five FA were identified as methyl esters and N-acyl pyrrolidides by GC-MS. The sea slugs exhibited a wide diversity of FA. The common marine n-3 PUFA, 20:5n-6 and 22:6n-3, constituted 0.6-1.3% of the total FA, whereas n-6 PUFA, 22:4n-6, 20:4n-6, and 18:2n-6, were the main (25%). Among monounsaturated FA, 7-21:1 was the main (up to 6.2%). The non-methylene-interrupted (NMI) FA were found (9.4 and 12.4%), including the known 5,11-20:2, 5,13-20:2, 7,13-22:2, 7,15-22:2 and a novel isomer 7,13-21:2 (up to 3.9%). The pathway of its biosynthesis was suggested. A series of very long chain FA (VLC FA), with the main 5,9-25:2 and 5,9-26:2, were identified. High level of VLC FA (8.7 and 11.7%) in sea slugs is apparently the result of predation on sponges. Another unique feature concerned a high abundance of various odd and branched FA (16.7 and 34%), which could have originated from the dietary origin or symbiotic bacteria. This is the first report on lipid and FA composition of nudibranchs.

Lipid Composition of the Digestive Gland, Mantle and Stomach Fluid of the Gonatid Squid Berryteuthis anonychus

The lipid content and class composition of the digestive gland, mantle and stomach fluid of the gonatid squid Berryteuthis anonychus collected in the North Pacific are described. The digestive glands contained large amounts of lipids (20.0-35.6%), which comprised mainly triacylglycerols (TAG: 57.1-77.3%) and diacyl glyceryl ethers (DAGE: 12.9-14.6%). The mantles contained the least amounts of lipids (1.3-1.4%), which comprised phospholipids (76.2-79.4%), TAG (0.1%) and trace amounts of DAGE. The stomach fluids contained low amounts of lipids (4.5%), which comprised wax esters (75.2%), TAG (4.7%) and DAGE (0.9%). The main components of the alkyl chains in DAGE from the digestive glands were 16:0 (50.7-57.3%), 20:1n-11 (6.2-8.0%), 16:1n-7 (3.7-7.1%) and 18:0 (2.8-7.9%) alcohols. Component fatty alcohols originating in wax esters from the stomach fluids were rich in monoenes (90.9%), including 22:1n-11 (45.3%) and 20:1n-11 (15.3%) alcohols. The fatty acid compositions of DAGE and TAG in the digestive glands, of phospholipids in the mantles, and of wax esters and TAG in the stomach fluids are also discussed.

Characterization of the lipid composition and natural antioxidants in the liver oil of Dasyatis brevis and Gymnura marmorata rays

The omega-3 polyunsaturated fatty acids (PUFA) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA), have been recognized for their important role in health. EPA has several beneficial effects regarding coronary heart disease, while DHA has been found to be important for the development of the brain and retina. The increase in the consumption of fish oil, a commercial source of PUFA, has made necessary the search for new fish species rich in PUFA that could be used as raw material for the fish oil production. The lipid, fatty acid composition and natural antioxidant contents (carotene, tocopherol) were analyzed for the liver oil of Dasyatis brevis (arenera) and Gymnura marmorata (mariposa), two ray species commercially captured in the Gulf of California. The liver oil yield 25–50% (w/w) for D. brevis and 38–56% for G. marmorata. The triglyceride fraction was the major lipid class (577–758 mg/g) for both species, with smaller proportions of sterol esters, free sterols, polar lipids and diacyl glyceryl ethers. D. brevis showed a greater carotene and tocopherols concentration (6.9 mg/100 g, 25.3 mg/100 g, respectively) than G. marmorata (1.8 mg/100 g, 2.8 mg/100 g, respectively). The content of saturated and monoenoic fatty acid was similar for both species, however, the liver oil of G. marmorata had twice as much DHA than D. brevis. The composite percentage composition of DHA plus EPA with respect to the total of fatty acids in liver oil was 18% for G. marmorata and 16% for D. brevis. The liver oil of G. marmorata and D. brevis represent a new source of omega-3 PUFA that can be used for human and animal nutrition.

Direct analysis of lipids in single zooplankter individuals by matrix-assisted laser desorption/ionization mass spectrometry.

A highly sensitive method to analyze the intact lipids in a single zooplankter individual at the level of a few tenths of a microgram was developed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with a direct sampling technique. The sampling procedure involved (1) putting a zooplankter individual sample onto the MALDI sample plate, (2) cutting the sample into a few pieces by means of tweezers, (3) depositing aliquots of matrix and cationization reagent solutions on the zooplankter sample, and (4) irradiating with a N2 laser to cause MALDI. By using this technique, the mass spectra of the single zooplankter samples showed a series of ions generated from phospholipids with 34 or 36 carbons in the acyl groups and neutral lipids such as triglycerides and diacylglyceryl ethers with 50-54 carbons in their acyl and alkenyl groups. Accordingly, this method enabled us to estimate the relative quantity between "structured lipids" (phospholipids) and "storage lipids" (neutral lipids) in an individual zooplankter, which should give us a good clue to elucidate the roles of each class of lipids in its growth.

Inter species changes of lipid compositions in liver of shallow-water sharks from the Indian Ocean

: The liver oils of five dominant shark species, Alopias superciliosus, Carcharhinus falciformis, C. longimanus, Prionace glauca, and Sphyrna lewini, in the Indian Ocean were studied for their lipid classes, fatty acid and triacylglycerol (TAG) molecular compositions, in order to understand and identify the inter species changes and possible utilization avenues. The livers showed 26.1–60.1% oil content regardless of the gender or species of shark. Triacylglycerol was the predominant lipid class (65.2–86.1%) in all species followed by sterol esters (2.9–12.7%), hydrocarbons (2.5–11.6%) and diacylglyceryl ethers (1.0–3.8%). The major fatty acid in total lipid and TAG was docosahexaenoic acid (C22:6n-3; DHA), which in male S. lewini was at remarkable levels (43.4%). The predominant fatty acid combinations of TAG molecules in all shark species were palmitic, DHA and oleic acids (PDO 12.5–19.9%), and palmitic, DHA and palmitic acids (PDP; 8.4–15.4%). Tridocosahexaenoin was found in considerable levels in S. lewini (male).

Variation in lipid classes and fatty acid composition of salmon shark ( Lamna ditropis) liver with season and gender

The influence of season and gender on lipid content, lipid classes, and fatty acid compositions was assessed in livers of salmon shark ( Lamna ditropis), caught in the Pacific Ocean. No significant difference in the hepatosomatic index was noted with season, though the lipid content was significantly higher ( P<0.05) in winter. Triacylglycerol (TAG) was identified as the predominant lipid class (78.5–82.0%), followed by sterol esters (5.7–9.1%) and hydrocarbons (3.4–5.4%). No significant differences were observed in TAG composition with respect to the season or gender. However, diacylglyceryl ether contents were significantly higher ( P<0.05) in winter (3.8–5.3%) than those obtained in summer (1.3–1.1%). Polyunsaturated fatty acids constituted the major fatty acid class of salmon shark total liver lipid and docosahexaenoic acid (C22:6n-3) (22.7–28.4%) was the most abundant fatty acid which was significantly lower ( P<0.05) in winter. These results suggested that lipid characteristics of salmon shark liver were influenced by season, but not by gender.

Comparison of growth and lipid composition in the green abalone, Haliotis fulgens, provided specific macroalgal diets

Lipid composition of abalone was examined over a one-year interval. A feeding trial was designed to cover a full reproductive cycle in young adult green abalone, Haliotis fulgens, consisting of five diet treatments: the macrophytic algal phaeophyte Egregia menziesii, rhodophyte Chondracanthus canaliculatus, chlorophyte Ulva lobata, a composite of the three algae and a starvation control. The lipid class, fatty acid, sterol and 1- O-alkyl glyceryl ether profiles were determined for foot, hepatopancreas/gonad tissues and larvae. The major fatty acids were 16:0, 18:0, 18:1( n-7)c, 18:1( n-9)c, 20:4( n-6), 20:5( n-3) and 22:5( n-3), as well as 14:0 for abalone fed brown and red algae. 4,8,12-Trimethyltridecanoic acid, derived from algae, was detected for the first time in H. fulgens (hepatopancreas complex, 1.2–13.9%; larvae, 0.5% of total fatty acids). Diacylglyceryl ethers were present in larvae (0.6% of total lipid). The major 1- O-alkyl glycerols were 16:0, 16:1 and 18:0. Additionally, 18:1( n-9) was a major component in hepatopancreas/gonad and larvae. The major sterol was cholesterol (96–100% of total sterols). Highest growth rates were linked to temperature and occurred in abalone fed the phaeophyte E. menziesii (43 μm·day –1, 56 mg·day –1 yearly mean), an alga containing the highest levels of C 20 polyunsaturated fatty acids and the highest ratio of 20:4( n-6) to 20:5( n-3). This study provides evidence of the influence of diet and temperature on seasonal changes in abalone lipid profiles, where diet is most strongly related to body mass and temperature to shell length. The allocation of lipids to specific tissues in green abalone clarifies their lipid metabolism. These results provide a basis for improving nutrition of abalone in mariculture through formulation of artificial feeds.

Seasonal Lipid Composition in Macroalgae of the Northeastern Pacific Ocean

The lipid classes and fatty acid profiles of macrophytic algae from the Phaeophyta (Egregia menziesii), Rhodophyta (Chondracanthus canaliculatus) and Chlorophyta (Ulva lobata) were determined. Ulva lobata contained the highest amounts of lipids (20-29 mg g - 1 dry mass), followed by Egregia menziesii (9-16 mg) and Chondracanthus canaliculatus (2-3 mg), with increased lipids in winter and spring. This was reflected in total fatty acid content (14-24, 6-13 and 1-2 mg g - 1 dry mass, respectively). Major lipid classes were polar lipids (44-94 % of total lipids) and sterols (3-8 %). Higher levels of triacylglycerols occurred in Egregia menziesii during spring (22 %) and in Ulva lobata during summer (12 %). Free fatty acids were also variable (0-26 %). Triacylglycerols were not detected in Chondracanthus canaliculatus. Low levels of wax esters and diacylglyceryl ethers were detected in Ulva lobata (0.1 %). The major fatty acid common to all species was 16:0. Egregia menziesii and Chondracanthus canaliculatus contained 14:0, 18:1(n-9), 20:4(n-6) and 20:5(n-3) as major components. Egregia menziesii and Ulva lobata also contained 18:2(n-6), 18:3(n-3) and 18:4(n-3), and Chondracanthus canaliculatus and Ulva lobata contained 18:1(n-7). Large amounts of C 1 6 polyunsaturated fatty acids and the presence of 22:0 and C 2 2 polyunsaturated fatty acids were unique to U. lobata. Knowledge gained regarding macroalgal lipid composition may prove useful in raising mariculture species.

Amount and Composition of Diacyl Glyceryl Ethers in Various Tissue Lipids of the Deep-sea Squid Berryteuthis magister.

Examination was made of the amounts and compositions of diacyl glyceryl ethers (DAGE) in various tissue lipids of the deep-sea squid Berryteuthis magister. Liver specimens contained copious amounts of lipids (56.9%) which were composed almost entirely of triacylglycerols (TG: 53.1%) and DAGE (32.4%). Ovary samples contained substantial amounts of lipids (13.9%) with considerable DAGE (8.1%). Mantle, integument and testis samples contained small amounts of lipids (1.0, 1.1 and 1.5%, respectively) with lower DAGE content (0.1%, 0.1% and trace, respectively). In liver and mantle, glyceryl ethers originating in DAGE had essentially the same alkyl chains, whose most predominant component was 16:0 (70.2% and 69.9%) alcohol followed by 18:0 (7.1% and 6.3%), 18:1n-9 (7.4% and 5.9%) and 18:1n-7 (4.5% and 4.6%) alcohols, respectively. Component glyceryl ethers in ovary were characteristically rich in monoenes (52.9%) with 18:1n-9 (24.6%), 20:1n-9 (15.5%) and 18:1n-7 (10.2%) alcohols. Fatty acid compositions of DAGE, TG and phospholipid classes in various tissue lipids of this squid species are discussed.

Unusually high levels of non-saponifiable lipids in the fishes escolar and rudderfish: Identification by gas and thin-layer chromatography

Analysis of the non-saponifiable lipids of the fishes Lepidocybium flavobrunneum and Ruvettus pretiosus (escolar), and Centrolophus niger and Tubbia spp. (rudderfish) was performed. The analyses were used to clarify the cause of recent reports of illness (diarrhoea) in Australia from consumption of purported rudderfish. Both escolar and rudderfish contained very high levels of oil (generally between 14 to 25%, as % wet mass) in the fillet and the oil compositions were different to most seafood. Escolar oil contained mainly wax ester (>90% of oil). The oil from five specimens of rudderfish contained mainly diacylglyceryl ether (DAGE, >80% of oil) or hydrocarbon (>80% of oil, predominately squalene). One rudderfish specimen contained mainly polar lipid. Major differences in oil content and composition, including fatty alcohol and glyceryl ether diols (derived from DAGE), were observed between purported individuals of the same species or related species of rudderfish, raising the possibility of geographic or seasonal differences affecting the oil composition. The oil composition of fish fillet samples associated with the health issues were consistent with the profiles for escolar, rather than rudderfish species. These findings, in particular the lipid class and fatty alcohol profiles, were supported by general protein fingerprinting results and were consistent with the samples originating from individuals of the escolar species L. flavobrunneum. The high wax ester content of the escolar group clarifies the reported diarrhoeal effects to consumers. Purgative properties of high wax ester containing fish oils have been reported for escolar and other species. The results highlight the potential for non-saponifiable lipid profiles to be used for identification of fish fillets and oils to at least group level.

Identification and quantification of molecular species of diacyl glyceryl ether by reversed-phase high-performance liquid chromatography with refractive index detection and mass spectrometry

We have developed a method to identify and quantify the molecular species of diacyl glyceryl ether (DAGE) using high-performance liquid chromatography (HPLC) equipped with a refractive index detector and an electrospray ionization and time of flight mass spectrometer (LC–RI–MS). An octadecyl silica column with a mixture of acetonitrile and dichloromethane (65:35, v/v) as an eluant was used for the HPLC. When the LC–RI–MS method was applied to a mixture of synthetic DAGEs; 1- O-hexadecyl-2,3-dioleoylglycerol ( O-16:0–18:1–18:1), 1- O-octadecyl-2,3-dioleoylglycerol ( O-18:0–18:1–18:1), 1- O-octadecenyl-2,3-dioleoylglycerol ( O-18:1–18:1–18:1), 1- O-octadecyl-2,3-didocodahexaenoylglycerol ( O-18:0–22:6–22:6), and 1- O-octadecenyl-2,3-didocosahexaenoylglycerol ( O-18:1–22:6–22:6), good separation and quantification were obtained on the refractive index chromatogram. A pseudo-molecular ion [M+NH 4] + and a monoacyl glyceryl ether ion [M−RCO 2] + were observed for all synthetic DAGEs on the mass spectrum. It was found that the fatty acids and glyceryl ether in DAGE could be easily identified by these mass spectra. When this LC–RI–MS method was applied to the DAGEs extracted from muscle of Stromateus stellatus, approximately 18 peaks were observed on LC–RI–MS chromatograms and the major molecular species of DAGEs were identified as O-16:0–18:1–18:1.