Lipids are important biomolecules in all biological systems and serve numerous essential cellular functions. The global analysis of complex lipids is very challenging due to the extreme diversity in lipid structures. Variation in linkages and positions of fatty acyl chain(s) on the lipid backbone, functional group modification, occurrence of the molecular species as isomers or isobars are among some of the greatest challenges to resolve in lipidomics. In this work, we describe a routine analytical approach combining two liquid chromatography platforms: hydrophilic interaction (HILIC) and C30 reversed-phase chromatography (C30RP) coupled to high resolution mass spectrometry (HRMS) as complementary high throughput platforms to analyze complex lipid mixtures. Vascular plants (kale leaves and corn roots), rat brain and soil microbes were used as proxies to evaluate the efficiency of the enhanced approach to resolve traditional, as well as, modified lipids during routine lipidomics analysis. We report for the first time, the observation of a modified class of acylphosphatidylglycerol (acylPG) in corn roots by HILIC, and further resolution of the isomers using C30RP chromatography. We also used this approach to demonstrate the presence of high levels of N-monomethyl phosphatidylethanolamine (MMPE) in soil microbes, as well as to determine the regioisomers of lysophospholipids in kale leaves. Additionally, neutral lipids were demonstrated using C30RP chromatography in positive ion mode to resolve triacylglycerol isomers in rat brain. The work presented here demonstrates how the enhanced approach can more routinely permit novel biomarker discovery, or lipid metabolism in a wide range of biological samples.

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Clear differences in the volatile metabolites of wild and farmed sea bass have been found. A great deal of valuable information on sea bass volatile metabolites has been obtained, which can be useful in understanding certain aspects of the quality and safety of raw and processed sea bass.

Fatty acid esters of hydroxy fatty acids (FAHFA), diglycerides (DG) and monoacetyldiglycerides (MAcDG) are gaining interest as functional lipids in pharmaceuticals and functional food formulations for managing and treating metabolic or inflammatory diseases. Herein, we investigated whether the antler and/or meat of two Cervids (moose and caribou) are novel sources of FAHFA, DG and MAcDG. We observed FAHFA present in moose and caribou composed mainly of polyunsaturated families, and that the esterification occurred frequently at the C5-hydroxy fatty acid moiety, most noticeably arachidonic acid 5-hydroxyeicosatrienoic acid (ARA-5-HERA). Moose antler, caribou and moose meat also contained significant levels of both 1,2-DG and 1,3-DG lipids. The 1,3-DG molecular species consisted mainly of 16:0/18:1, 18:0/16:0, and 18:0/18:1. On the other hand, major 1,2-DG species consisted of DG 18:0/18:0, 16:0/16:0 and 18:1/18:1 molecular species with higher levels in the antler compared to the meat. The molecular species composition of MAcDG was very simple and consisted of 14:2/18:2/2:0, 16:0/18:2/2:0, 16:0/18:1/2:0 and 18:0/18:1/2:0 with the first species 14:2/18:2/2:0 predominating in the tip of moose antlers. Increasing access to and knowledge of the presence of these functional lipids in foods will enhance their intake in the diet with potential implications in improving personal and population health.

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The consistency of the results confirms the usefulness of FTIR spectroscopy to detect frauds regarding sea bass origin, and to provide important compositional data about sea bass lipids from the nutritional and technological point of view.

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Farmed European sea bass (Dicentrarchus labrax) fillets were salted by two methods, brine-and drysalting. Both salted and unsalted fillets were submitted to thermo-oxidative conditions in order to study the evolution of their lipids and their oxidative stability. Lipids were extracted and studied by proton nuclear magnetic resonance ( 1 H NMR). This technique allowed the evolution of the molar percentages of the different kinds of acyl groups (omega-3, docosahexaenoic, eicosapentaenoic, diunsaturated omega-6, and omega-1) to be followed. In addition, the formation of secondary oxidation compounds, such as aldehydes (alkanals, trans-2-alkenals, trans,trans-2,4-alkadienals), could be monitored and quantified by means of this technique, providing information about the oxidative status of the sea bass fillets. No primary oxidation compounds were detected. Moreover, the concentrations of 1,2-diglycerides and phosphatidylcholine were determined. Equations for all the mentioned quantitative determinations were proposed. It was evidenced that the use of salting methods did not provoke the immediate oxidation of sea bass lipids, but reduced their oxidative stability, this effect being more pronounced in dry-salting. Although oxidation began earlier in brine-salted samples than it did in unsalted ones, these latter reached a degradation level of a similar order to that of the brine-salted samples after a certain period of time under the degradative conditions. Practical applications:The results of this study will be useful for optimizing the conditions of European sea bass salting processes, in order to minimize possible lipid oxidation. This is of great importance for sectors of the seafood industry, which focus on this and other fish species with similar lipid content and acyl group proportions, and which are interested in providing high quality food products. The information given by 1 H NMR, a rapid and non-destructive method compared with other conventional chemical ones, is very valuable for other researchers who also study fish lipid oxidation processes.