Identification of very-long-chain polyunsaturated fatty acids from Amphidinium carterae by atmospheric pressure chemical ionization liquid chromatography-mass spectroscopy

Variations of intact phospholipid compositions in the digestive system of Antarctic krill, Euphausia superba, between summer and autumn

The biochemical composition of Antarctic krill, Euphausia superba, is largely determined by their feeding behaviour. As they supply energy for animals of a higher trophic level and are also commercialized for human consumption, the interest in research on the species is high. Lipids, especially phospholipids, make up a high proportion of dry weight in krill. Seasonal changes are well documented in the fingerprint of free fatty acids analysed after hydrolysis of phospholipids, but the underlying intact polar lipids are rarely considered. In this study, we evaluated the compositions of intact phospholipids (IPLs) in the stomach, digestive gland and hind gut of Antarctic krill caught in summer and autumn at the Antarctic Peninsula region. Using high-resolution mass spectrometry, the fatty acid composition of 179 intact phospholipids could be resolved. Most IPLs were phosphatidylcholines, followed by phosphatidylethanolamines. Several very long chain polyunsaturated fatty acids up to 38:8, which have not been reported in krill before, were identified. The composition shifted to higher molecular weight IPLs with a higher degree of unsaturation for summer samples, especially for samples of the digestive gland. The data supplied in this paper provides new insights into lipid dynamics between summer and autumn usually described by free fatty acid biomarkers.

Very long chain fatty acids

Very long chain fatty acids (VLCFAs) are important components of various lipid classes in most organisms, from bacteria to higher plants and mammals, including humans. VLCFAs, or very long chain polyunsaturated fatty acids (VLCPUFAs), can be defined as fatty acids with 23 or more carbon atoms in the molecule. The main emphasis in this review is on the analysis of these acids, including obtaining standards from natural sources or their synthesis. Furthermore, the occurrence and analysis of these compounds in both lower (bacteria, invertebrates) and higher organisms (flowering plants or mammals) are discussed in detail. Attention is paid to their biosynthesis, especially the elongation of very long chain fatty acids protein (ELOVL4). This review deals with papers describing these very interesting compounds, whose chemical, biochemical and biological properties have not been fully explored.

Lipidomic profile in three species of dinoflagellates (Amphidinium carterae, Cystodinium sp., and Peridinium aciculiferum) containing very long chain polyunsaturated fatty acids

This study describes the identification of very long chain polyunsaturated fatty acids (VLCPUFAs) in three strains of dinoflagellates (Amphidinium carterae, Cystodinium sp., and Peridinium aciculiferum). The strains were cultivated and their lipidomic profiles were obtained by high resolution mass spectrometry with the aid of positive and negative electrospray ionization (ESI) mode by Orbitrap apparatus. Hydrophilic interaction liquid chromatography (HILIC/ESI) was used to separate major lipid classes of the three genera of dinoflagellates by neutral loss scan showing the ion [M + H-28:8]⁺, where 28:8 was octacosaoctaenoic acid, and by precursor ion scanning of ions at m/z 407, which was an ion corresponding to the structure of acyl of 28:8 acid (C₂₇H₃₉COO^-). Based on these analyzes, it was found that out of more than a dozen lipid classes present in the total lipids, only two classes of neutral lipids, i.e. major triacylglycerols and minor diacylglycerols contain VLCPUFAs. In polar lipids, VLCPUFAs were identified only in phosphatidic acid (PA) and phosphatidyl choline (PC) or in their lyso-forms (LPA and LPC). Further analysis of individual lipid classes by reversed-phase high-performance liquid chromatography (RP-HPLC) showed the presence of triacylglycerols (TAGs) containing VLCPUFAs, i.e. molecular species of the sn-28:7/28:8/28:8, sn-26:7/28:7/28:8, or sn-26:7/28:8/28:8 types. These TAGs are the longest and most unsaturated TAGs isolated from a natural source that have yet been synthesized. In the case of PA and PC, tandem MS identified sn-28:8/16:0-PA and sn-28:8/16:0-PC and the corresponding lyso-forms (28:8-LPC and 28:8-LPA). All these results indicate that TAGs containing VLCPUFAs are biosynthesized in dinoflagellates in the same manner as in higher eukaryotic organisms, which means that the PA, after conversion to DAG, serves as a precursor in the biosynthesis of other phospholipids, e.g. PC, and, after further acylation, also of TAG.

Chromatographic Methods in the Separation of Long-Chain Mono- and Polyunsaturated Fatty Acids

This review presents various chromatographic systems, TLC, HPLC, GC, and also SFC, developed for identification and accurate quantification of long-chain mono- and polyunsaturated fatty acids from different samples with emphasis on selected literature which was published during last decade. Almost all the aspects such as preseparation step of fatty acids (cisandtrans), stationary phase, solvent system, and detection mode are discussed.

A nine carbon homologating system for skip-conjugated polyenes

Ozonolysis of Z,Z,Z-cylonona-1,4,7-triene leads to a 1,9-difunctionalised Z,Z-3,6-nonadiene which is readily converted into a range of polyunsaturated pheromones and fatty acids.

Diversity of fatty acid composition of symbiotic dinoflagellates in corals: evidence for the transfer of host PUFAs to the symbionts

High diversity of fatty acid (FA) composition of endosymbiotic dinoflagellates of the Symbiodinium group (zooxanthellae) isolated from different cnidarian groups has been found. To explain this diversity, FA composition of the total lipids of pure symbiont fractions (SF) and host cell tissue fractions (HF) isolated from one hydrocoral, two soft coral, and seven hard coral species inhabiting the shallow waters of the South China Sea (Vietnam) were compared. Symbiodinium phylogenetic clade designation for each SF was also determined, however, the relationship between the clade designation and FA composition of Symbiodinium was not found. The profiles of marker polyunsaturated FAs (PUFAs) of symbionts (18:4n-3, 18:5n-3, 20:5n-3) did not depend on taxonomic designation of the host and reflected only a specimen-specific diversity of the SF lipids. Several FAs such as 20:0, C24 PUFAs, 22:5n-6, and 18:2n-7 concentrated in HF lipids but were also found in SF lipids. For ten cnidarian species studied, the principal components analysis of total FAs (27 variables) of the symbiotic fractions was performed. The clear division of the symbiotic dinoflagellates according to the host systematic identity was found on a subclass level. This division was mainly caused by the FAs specific for the host lipids of each cnidarian subclasses such as hard corals, soft corals, and hydrocorals. Thus, the coral hosts affect the FA profile of their symbionts and cause the diversity of FA composition of Symbiodinium. The transfer of FAs from the coral host to their symbiotic dinoflagellates and modulation of PUFA biosynthesis in symbionts by the host are considered as possible reasons of the diversity studied.

Efficient synthesis of the very-long-chain n-3 fatty acids, tetracosahexaenoic acid (C24:6n-3) and tricosahexaenoic acid (C23:6n-3)

Tetracosahexaenoic acid (C(24):6n-3, THA, 3) is an essential biosynthetic precursor in mammals of docosahexaenoic acid (C(22):6n-3, DHA, 1), the end-product of the metabolism of n-3 fatty acids. THA 3 is present in commercially valuable fishes, such as flathead flounder. Tricosahexaenoic acid (C(23):6n-3, TrHA, 2), an odd-numbered-chain fatty acid, has been identified from marine organisms such as the dinoflagellate, Amphidinium carterae. To date, few studies have examined THA 3 and TrHA 2 due to difficulties in detecting and identifying these compounds, so their chemical and biological properties remain poorly characterized. Only one methodology for the chemical synthesis of THA 3 has been presented, and no method for the synthesis of TrHA 2 has been reported. We report here the efficient synthesis of THA 3 in four steps in 56% overall yield, and the synthesis of TrHA 2 in six steps in 48% overall yield. We also present the synthesis of Δ(2)-THA 4, an intermediate of β-oxidation of THA 3 to DHA 1, in three steps in 73% overall yield.

Retinal very long-chain PUFAs: new insights from studies on ELOVL4 protein

Compared with other mammalian tissues, retina is highly enriched in PUFA. Long-chain PUFA (LC-PUFA; C18-C24) are essential FAs that are enriched in the retina and are necessary for maintenance of normal retinal development and function. The retina, brain, and sperm also contain very LC-PUFA (VLC-PUFA; >C24). Although VLC-PUFA were discovered more than two decades ago, very little is known about their biosynthesis and functional roles in the retina. This is due mainly to intrinsic difficulties associated with working on these unusually long polyunsaturated hydrocarbon chains and their existence in small amounts. Recent studies on the FA elongase elongation of very long chain fatty acids-4 (ELOVL4) protein, however, suggest that VLC-PUFA probably play some uniquely important roles in the retina as well as the other tissues. Mutations in the ELOVL4 gene are found in patients with autosomal dominant Stargardt disease. Here, we review the recent literature on VLC-PUFA with special emphasis on the elongases responsible for their synthesis. We focus on a novel elongase, ELOVL4, involved in the synthesis of VLC-PUFA, and the importance of these FAs in maintaining the structural and functional integrity of retinal photoreceptors.

Recent trends in the advanced analysis of bioactive fatty acids

The consumption of dietary fats have been long associated to chronic diseases such as obesity, diabetes, cancer, arthritis, asthma, and cardiovascular disease; although some controversy still exists in the role of dietary fats in human health, certain fats have demonstrated their positive effect in the modulation of abnormal fatty acid and eicosanoid metabolism, both of them associated to chronic diseases. Among the different fats, some fatty acids can be used as functional ingredients such as alpha-linolenic acid (ALA), arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), gamma-linolenic acid (GLA), stearidonic acid (STA) and conjugated linoleic acid (CLA), among others. The present review is focused on recent developments in FAs analysis, covering sample preparation methods such as extraction, fractionation and derivatization as well as new advances in chromatographic methods such as GC and HPLC. Special attention is paid to trans fatty acids due its increasing interest for the food industry.

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.

Odd-numbered very-long-chain polyunsaturated fatty acids from the dinoflagellate Amphidinium carterae identified by atmospheric pressure chemical ionization liquid chromatography-mass spectrometry

A method is described for the enrichment of odd very-long-chain polyunsaturated fatty acids (VLCPUFAs) by means of RP-HPLC and argentation TLC from total fatty acids of the dinoflagellate A. carterae and their identification as picolinyl esters by means of microbore liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization (LC-MS/APCI). The combination of argentation TLC and LC-MS/APCI was used to identify rare and unusual odd VLCPUFAs up to nonacosahexaenoic acid. Two acids, (allZ)-nonacosa-11,14,17,20,23-pentaenoic acid (29:5n-6) and (allZ)-nonacosa-11,14,17,20,23,26-hexaenoic acid (29:6n-3), were synthesized for the first time to unambiguously confirm their structure. Possible biosynthetic pathways for odd VLCPUFAs are also proposed.