Stearidonic Acid-Enriched Soybean Oil Increased the Omega-3 Index, an Emerging Cardiovascular Risk Marker

A plant source of omega-3 fatty acid (FA) that can raise tissue eicosapentaenoic acid (EPA) and/or docosahexaenoic acid (DHA) is needed. A soybean oil (SBO) containing approximately 20% stearidonic acid [SDA; the delta-6 desaturase product of alpha-linolenic acid (ALA)] derived from genetically modified soybeans is under development. This study compared the effects of EPA to SDA-SBO on erythrocyte EPA+DHA levels (the omega-3 index). Overweight healthy volunteers (n=45) were randomized to SDA-SBO (24 ml/day providing approximately 3.7 g SDA) or to regular SBO (control group) without or with EPA ethyl esters (approximately 1 g/day) for 16 weeks. Serum lipids, blood pressure, heart rate, platelet function and safety laboratory tests were measured along with the omega-3 index. A per-protocol analysis was conducted on 33 subjects (11 per group). Compared to baseline, average omega-3 index levels increased 19.5% in the SDA group and 25.4% in the EPA group (p<0.05 for both, vs. control). DHA did not change in any group. Relative to EPA, SDA increased RBC EPA with about 17% efficiency. No other clinical endpoints were affected by SDA or EPA treatment (vs. control). In conclusion, SDA-enriched SBO significantly raised the omega-3 index. Since EPA supplementation has been shown to raise the omega-3 index and to lower risk for cardiac events, SDA-SBO may be a viable plant-based alternative for providing meaningful intakes of cardioprotective omega-3 FAs.     

Determination of Substrate Preferences for Desaturases and Elongases for Production of Docosahexaenoic Acid from Oleic Acid in Engineered Canola

Production of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in plant seed oils has been pursued to improve availability of these omega‐3 fatty acids that provide important human health benefits. Canola (Brassica napus), through the introduction of 10 enzymes, can convert oleic acid (OLA) into EPA and ultimately DHA through a pathway consisting of two elongation and five desaturation steps. Herein we present an assessment of the substrate specificity of the seven desaturases and three elongases that were introduced into canola by expressing individual proteins in yeast. In vivo feeding experiments were conducted with 14 potential fatty acid intermediates in an OLA to DHA pathway to determine the fatty acid substrate profiles for each enzyme. Membrane fractions were prepared from yeast expression strains and shown to contain active enzymes. The elongases, as expected, extended acyl‐CoA substrates in the presence of malonyl‐CoA. To distinguish between enzymes that desaturate CoA‐ and phosphatidylcholine‐linked fatty acid substrates, we developed a novel in vitro method. We show that a delta‐12 desaturase from Phytophthora sojae, an omega‐3 desaturase from Phytophthora infestans and a delta‐4 desaturase from Thraustochytrium sp., all prefer phosphatidylcholine‐linked acyl substrates with comparatively low use of acyl‐CoA substrates. To further validate our method, a delta‐9 desaturase from Saccharomyces cerevisiae was confirmed to use acyl‐CoA as substrate, but could not use phosphatidylcholine‐linked substrates. The results and the assay methods presented herein will be useful in efforts to improve modeling of fatty acid metabolism and production of EPA and DHA in plants.     

Lipase selectivity toward fatty acids commonly found in fish oil

The main objective of this study was to compare the fatty acid selectivity of numerous commercially available lipases toward the most ubiquitous fatty acids present in fish oils in form of their corresponding ethyl esters. Special interest was taken in their ability to separate the n‐3 long‐chain polyunsaturated fatty acids (PUFA), mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), from the more saturated fatty acids as well as exploiting the putative discrimination between these highly valuable n‐3 PUFA. Hydrolysis of sardine oil ethyl esters in a Tris buffer solution by 12 microbial lipases is described. The results reveal that all of the lipases strongly discriminate against the n‐3 PUFA and prefer the more saturated fatty acids as substrates. Most of the lipases discriminate between EPA and DHA in favor of EPA, however, 2 bacterial lipases from Pseudomonas were observed to prefer DHA to EPA. Digestive lipolytic enzymes isolated from salmon and rainbow trout intestines displayed reversed fatty acid selectivity when their fish oil triacylglycerol hydrolysis was studied. Thus, the n‐3 PUFA including EPA and DHA were observed to be hydrolyzed at a considerably higher rate than the more saturated fatty acids.     

Stearidonic Acid Increases the Red Blood Cell and Heart Eicosapentaenoic Acid Content in Dogs

Plant sources of omega-3 fatty acids (FA) are needed that can materially raise tissue levels of long-chain omega-3 FA [i.e., eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 20:6n-3)]. Stearidonic acid (SDA; 18:4n-3) is the delta-6 desaturase product of alpha-linolenic acid (ALA; 18:3n-3), and when fed to humans, increases red blood cell (RBC) content of EPA to a greater extent than does ALA. This study was undertaken to determine the dose-dependence and time course of the increase in the EPA and DHA content of the heart and RBC in dogs. Adult male Beagles were fed 21, 64, or 193 mg/kg of SDA in in their food daily for up to 12 weeks. Positive and negative controls were given EPA (43 mg/kg) or high oleic acid sunflower oil, respectively. The baseline EPA content of RBC was 0.38 ± 0.03% which increased (P < 0.01) in a dose-dependent manner, with the high dose of SDA and EPA achieving levels of 1.33 ± 0.26 and 1.55. ± 0.28%, respectively. In the heart, the content of EPA rose from 0.06 ± 0.01 to 1.24 ± 0.22% in the EPA group and to 0.81 ± 0.32% in the high SDA group (both P < 0.01). In both tissues, DHA did not change. Compared to dietary EPA, SDA was 20–23% as efficient in raising tissue EPA levels. In conclusion, SDA supplementation increased the EPA content of RBC and heart and may have utility as a plant-based source of omega-3 FA.     

Docosahexaenoic Acid and Eicosapentaenoic Acid Did not Alter <Emphasis Type="Italic">trans</Emphasis>-10,<Emphasis Type="Italic">cis</Emphasis>-12 Conjugated Linoleic Acid Incorporation into Mice Brain and Eye Lipids

trans 10,cis 12‐CLA has been reported to alter fatty acid composition in several non‐neurological tissues, but its effects are less known in neurological tissues. Therefore, the purpose of this study was to determine if CLA supplementation would alter brain and eye fatty acid composition and if those changes could be prevented by concomitant supplementation with docosahexaenoic acid (DHA; 22:6n3) or eicosapentaenoic acid (EPA; 20:5n3). Eight‐week‐old, pathogen‐free C57BL/6N female mice (n = 6/group) were fed either the control diet or diets containing 0.5% (w/w) t10,c12‐CLA in the presence or absence of either 1.5% DHA or 1.5% EPA for 8 weeks. CLA concentration was significantly (P < 0.05) greater in the eye but not in the brain lipids of the CLA group when compared with the control group. The sums of saturated, monounsaturated, polyunsaturated fatty acids, and n3:n6 ratio did not differ between these two groups for both tissues. The n3:n6 ratio and concentrations of 20:5n3 and 22:5n3 were significantly greater, and those of 20:4n6, 22:4n6, and 22:5n6 were lesser in the CLA + DHA and CLA + EPA groups than in the control and CLA groups for either tissue. DHA concentration was higher in the CLA + DHA group only but not in the CLA + EPA group when compared with the CLA group for both tissues. The dietary fatty acids generally induced similar changes in brain and eye fatty acid concentration and at the concentrations used both DHA and EPA fed individually with CLA were more potent than CLA alone in altering the tissue fatty acid concentration.     

EPA,DHA, and Lipoic Acid Differentially Modulate the n-3 Fatty Acid Biosynthetic Pathway in Atlantic Salmon Hepatocytes

The aim of the present study was to investigate how EPA, DHA, and lipoic acid (LA) influence the different metabolic steps in the n‐3 fatty acid (FA) biosynthetic pathway in hepatocytes from Atlantic salmon fed four dietary levels (0, 0.5, 1.0 and 2.0%) of EPA, DHA or a 1:1 mixture of these FA. The hepatocytes were incubated with [1‐¹⁴C] 18:3n‐3 in the presence or absence of LA (0.2 mM). Increased endogenous levels of EPA and/or DHA and LA exposure both led to similar responses in cells with reduced desaturation and elongation of [1‐¹⁴C] 18:3n‐3 to 18:4n‐3, 20:4n‐3, and EPA, in agreement with reduced expression of the Δ6 desaturase gene involved in the first step of conversion. DHA production, on the other hand, was maintained even in groups with high endogenous levels of DHA, possibly due to a more complex regulation of this last step in the n‐3 metabolic pathway. Inhibition of the Δ6 desaturase pathway led to increased direct elongation to 20:3n‐3 by both DHA and LA. Possibly the route by 20:3n‐3 and then Δ8 desaturation to 20:4n‐3, bypassing the first Δ6 desaturase step, can partly explain the maintained or even increased levels of DHA production. LA increased DHA production in the phospholipid fraction of hepatocytes isolated from fish fed 0 and 0.5% EPA and/or DHA, indicating that LA has the potential to further increase the production of this health‐beneficial FA in fish fed diets with low levels of EPA and/or DHA.     

One-Step Concentration of Highly Unsaturated Fatty Acids from Tuna Oil by Low-Temperature Crystallization

Highly unsaturated fatty acids (HUFA), including eicosapentaenoic acid (EPA, 20:5n‐3), docosapentaenoic acid (DPA, 22:5n‐3 and 22:5n‐6) and docosahexaenoic acid (DHA, 22:6n‐3), play an important role in human health and nutrition. In this study, concentration of HUFA in free fatty acids (FFA) form by low‐temperature crystallization was investigated. For this purpose, tuna oil (7.1% EPA, 26.8% DHA) was first converted into corresponding FFA. Subsequently, crystallization conditions of various solvent types, the ratio of FFA to acetonitrile, operation temperature and crystallization time were optimized at a small scale of 2 g tuna oil fatty acids. Taking purity and yield into account, the optimum conditions were a 1:10 ratio of FFA to acetonitrile (w/v), ?60 °C, and 1 h. The optimal conditions resulted in concentrations of EPA, DHA and HUFA of 15.1, 58.4 and 79.6%, respectively, with corresponding yields of 61.5, 61.8 and 60.7%, respectively. Crystallization was carried out under the optimal conditions at a large scale of 200 g tuna oil FFA, and a similar concentration result was achieved. After evaporating away the solvent, the residual amount of acetonitrile met the US Pharmacopoeia requirement of <410 ppm. The process for enrichment of HUFA is readily scalable, effective and time‐saving.     

New natural antioxidants for protecting omega‐3 rich products

The long‐chain (LC) highly unsaturated omega‐3 fatty acids, EPA (eicosapentaenoic acid, 20:5) and DHA (docosahexaenoic acid, 22:6) are vital for a wide range of biological functions and are implicated in the prevention of numerous diseases. However, these fatty acids are highly susceptible to oxidation because of their unsaturated nature. Addition of antioxidants is one method to prevent lipid oxidation. As synthetic antioxidants may have carcinogenic effects at higher levels, the replacement of synthetic antioxidants with natural antioxidants is now in demand. We have isolated natural antioxidants from yoghurt, potato peel, fish protein hydrolysates and seaweed, which were able to protect highly unsaturated fish oil from oxidation. These antioxidant extracts may have potential for commercial exploitation.     

Highly unsaturated fatty acid synthesis in vertebrates: New insights with the cloning and characterization of a Δ6 desaturase of Atlantic salmon

Fish are an important source of the n−3 highly unsaturated fatty acids (HUFA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids that are crucial to the health of higher vertebrates. The synthesis of HUFA involves enzyme-mediated desaturation, and a Δ5 fatty acyl desaturase cDNA has been cloned from Atlantic salmon (Salmo salar) and functionally characterization of a Δ6 fatty acyl desaturase of Atlantic salmon and describe its genomic structure, tissue expression, and nutritional regulation. A salmon genomic library was screened with a salmon Δ5 desaturase cDNA and positive recombinant phage isolated and subcloned. The full-length cDNA for the putative fatty acyl desaturase was shown to comprise 2106 bp containing an open reading frame of 1365 bp specifying a protein of 454 amino acids (GenBank accession no. AY458652). The protein sequence included three histidine boxes, two transmembrane regions, and an N-terminal cytochrome b₅ domain containing the heme-binding motif HPGG, all of which are characteristic of microsomal fatty acid desaturases. Functional expression showed that this gene possessed predominantly Δ6 desaturase activity. Screening and sequence analysis of the genomic DNA of a single fish revealed that the Δ6 desaturase gene constituted 13 exons in 7965 bp of genomic DNA. Quantitative real-time PCR assay of gene expression in Atlantic salmon showed that both Δ6 and Δ5 fatty acyl desaturase genes, and a fatty acyl elongase gene, were highly expressed in intestine, liver, and brain, and less so in kidney, heart, gill, adipose tissue, muscle, and spleen. Furthermore, expression of both Δ6 and Δ5 fatty acyl desaturase genes in intestine, liver, red muscle, and adipose tissue was higher in salmon fed a diet containing vegetable oil than in fish fed a diet containing fish oil.     

Stearidonic acid (18:4n‐3): Metabolism,nutritional importance,medical uses and natural sources

Stearidonic acid (SA, 18:4n‐3) is a polyunsaturated fatty acid (PUFA) that constitutes the first metabolite of α‐linolenic acid (ALA, 18:3n‐3) in the metabolic pathway leading to C_20–22 PUFA, such as eicosapentaenoic acid (EPA, 20:5n‐3), and docosahexaenoic acid (DHA, 22:6n‐3), which recently have received much attention because of their various physiological functions in the human body. Recently, several studies indicated that dietary SA increased EPA more efficiently than ALA. Thus, vegetable oils containing SA may become a dietary source of n‐3 fatty acids that is more effective in increasing tissue n‐3 PUFA concentrations than the current ALA‐containing vegetable oils. Nevertheless, few SA sources occur in nature, although there are still a large number of species untested to date. SA has been detected in variable amounts in several species of algae, fungi and animals tissues, but the seeds of some plant families seem to be better sources of SA, especially Echium (Boraginaceae) species. This work reviews the nutritional significance, medical uses and natural occurrence of SA.     

Uncoupling EPA and DHA in Fish Nutrition: Dietary Demand is Limited in Atlantic Salmon and Effectively Met by DHA Alone

Due to the scarcity of marine fish oil resources, the aquaculture industry is developing more efficient strategies for the utilization of dietary omega‐3 long‐chain polyunsaturated fatty acids (n‐3 LC‐PUFA). A better understanding of how fish utilize EPA and DHA, typically provided by fish oil, is needed. However, EPA and DHA have different physiological functions, may be metabolized and incorporated into tissues differently, and may vary in terms of their importance in meeting the fatty acid requirements of fish. To address these questions, Atlantic salmon were fed experimental diets containing, as the sole added dietary lipid source, fish oil (positive control), tallow (negative control), or tallow supplemented with EPA, DHA, or both fatty acids to ~50 or 100 % of their respective levels in the positive control diet. Following 14 weeks of feeding, the negative control diet yielded optimum growth performance. Though surprising, these results support the notion that Atlantic salmon requirements for n‐3 LC‐PUFA are quite low. EPA was largely β‐oxidized and inefficiently deposited in tissues, and increasing dietary levels were associated with potential negative effects on growth. Conversely, DHA was completely spared from catabolism and very efficiently deposited into flesh. EPA bioconversion to DHA was largely influenced by substrate availability, with the presence of preformed DHA having little inhibitory effect. These results clearly indicate EPA and DHA are metabolized differently by Atlantic salmon, and suggest that the n‐3 LC‐PUFA dietary requirements of Atlantic salmon may be lower than reported and different, if originating primarily from EPA or DHA.     

Fatty acid profiles from forty-nine plant species that are potential new sources of γ-linolenic acid

Forty-nine plant species from Spain, belonging to the Boraginaceae, Scrophulariaceae, Onagraceae, and Ranunculaceae families, were surveyed in a search of new sources of γ-linolenic acid (18∶3ω6, GLA). Fatty acid profiles from seeds, stems, roots, flowers and leaves were determined. GLA was detected mainly in seed and root tissues. High GLA amounts were found in seeds of Boraginaceae species, with a maximum of 20.25% of total fatty acids in Myosotis nemorosa. Within the Scrophulariaceae the highest GLA content (10.17%) was found in Scrophularia sciophila. Variable amounts of stearidonic acid, (18∶4ω3, SDA) were present in Boraginaceae species, ranging from 0.08% of total seed fatty acids in Anchusa azurea to 21.06% in Echium asperrimum. SDA was also very abundant in all organs of Asperugo procumbens. A multivariate analysis was performed using our results and those reported for other plant species belonging to the same families in order to investigate a possible correlation between the fatty acid profile and the genera within these families.     

Combined Urea Complexation and Argentated Silica Gel Column Chromatography for Concentration and Separation of PUFAs from Tuna Oil: Based on Improved DPA Level

Eicosapentaenoic acid (EPA, 20:5n‐3), docosapentaenoic acid (DPA) isomers (22:5n‐6 and 22:5n‐3) and docosahexaenoic acid (DHA, 22:6n‐3) derived from tuna oil were concentrated by three stages of urea fractionation at various crystallization temperatures and different fatty acid/urea ratios. Thereafter, polyunsaturated fatty acids concentrate containing comparatively enriched DPA levels was purified by argentated silica gel column chromatography. A product containing 22.2 ± 0.6 % EPA, 4.6 ± 0.0 % DPAn‐6, 5.9 ± 0.1 % DPAn‐3 and 42.3 ± 1.2 % DHA was obtained at 1:1.6 fatty acid/urea ratio (w/w) by crystallization at ?8 °C for 16 h, ?20 °C for 8 h, and ?8 °C for 16 h. A DPA isomer concentrate containing 26.1 ± 0.5 % DPAn‐6 and 22.3 ± 0.4 % DPAn‐3 was achieved by argentated silica gel chromatography in the 6 % acetone/n‐hexane solvent fraction (v/v), and the recovery of both fatty acids was 66.1 ± 3.2 and 70.7 ± 2.2 %, respectively. Furthermore, 91.9 ± 2.5 % EPA and 99.5 ± 2.1 % DHA with recoveries of 47.8 ± 2.0 and 56.7 ± 3.3 %, respectively, were obtained in various fractions.     

Restricted-Range Boraginaceae Species Constitute Potential Sources of Valuable Fatty Acids

The aim of this work was to establish the richness in γ-linolenic acid (GLA, 18:3n-6) and stearidonic acid (SDA, 18:4n-3) of the seed oil of several restricted-range Boraginaceae species, in a search for new valuable oils as advantageous alternatives to the commercially available sources of both polyunsaturated fatty acids. To this end, seeds of selected Boraginaceae species were collected and analyzed. The highest GLA contents (% total fatty acids) were found in the seed oils of Symphytum caucasicum M.Bieb. (22.9 %), Anchusa undulata subsp. undulata (Ten.) Cout. (22.0 %), Anchusa puechii Valdés (20.0 %), Glandora nitida Thomas (19.2 %), Echium pininana Webb & Berth. (17.1 %) and Pentaglottis sempervirens (L.) L. H. Bailey (17.0 %). With regard to SDA, the highest percentage was found in the seed oil of Echium cantabricum (M. Laínz) Fdez. Casas & M. Laínz (14.7 %), followed by Lappula patula (Lehm.) Asch ex Gürke (13.6 %). It is noticeable that several GLA-enriched species stand under a great threat of extinction, thus revealing the importance of the preservation of the natural ecosystems for endangered species.     

Engineering Oilseed Plants for a Sustainable,Land-Based Source of Long Chain Polyunsaturated Fatty Acids

Numerous clinical studies have demonstrated the cardiovascular and mental health benefits of including very long chain omega-3 polyunsaturated fatty acids, namely eicospentaenoic acid (EPA) and docosohexaenoic acid (DHA) in the human diet. Certain fish oils can be a rich source of omega-3 long chain polyunsaturated fatty acids although processed marine oils are generally undesirable as food ingredients because of the associated objectionable flavors and contaminants that are difficult and cost-prohibitive to remove. Oilseed plants rich in omega-3 fatty acids, such as flax and walnut oils, contain only the 18-carbon omega-3 polyunsaturated fatty acid alpha-linolenic acid, which is poorly converted by the human body to EPA and DHA. It is now possible to engineer common omega-6 rich oilseeds such as soybean and canola to produce EPA and DHA and this has been the focus of a number of academic and industrial research groups. Recent advances and future prospects in the production of EPA and DHA in oilseed crops are discussed here.     

Stabilization of highly unsaturated fatty acids and delivery into foods

Highly unsaturated fatty acids derived from fish or algal oils, particularly EPA and DHA, are in high demand as healthy food ingredients in fortified foods. Due to their oxidative instability most food products incorporate stabilized microencapsulated EPA and DHA oils to avoid negative sensory impact associated with oxidation of these fatty acids. Complex coacervation has been particularly successful in stabilizing fish oil and providing an ingredient with a sensory shelf‐life consistent with that of the food product. Overcoming the technical challenges associated with the instability of these oils will help drive growth of the omega‐3 fortified healthy food ingredient market.     

Dietary Crude Lecithin Increases Systemic Availability of Dietary Docosahexaenoic Acid with Combined Intake in Rats

Crude lecithin, a mixture of mainly phospholipids, potentially helps to increase the systemic availability of dietary omega‐3 polyunsaturated fatty acids (n‐3 PUFA), such as docosahexaenoic acid (DHA). Nevertheless, no clear data exist on the effects of prolonged combined dietary supplementation of DHA and lecithin on RBC and plasma PUFA levels. In the current experiments, levels of DHA and choline, two dietary ingredients that enhance neuronal membrane formation and function, were determined in plasma and red blood cells (RBC) from rats after dietary supplementation of DHA‐containing oils with and without concomitant dietary supplementation of crude lecithin for 2–3 weeks. The aim was to provide experimental evidence for the hypothesized additive effects of dietary lecithin (not containing any DHA) on top of dietary DHA on PUFA levels in plasma and RBC. Dietary supplementation of DHA‐containing oils, either as vegetable algae oil or as fish oil, increased DHA, eicosapentaenoic acid (EPA), and total n‐3 PUFA, and decreased total omega‐6 PUFA levels in plasma and RBC, while dietary lecithin supplementation alone did not affect these levels. However, combined dietary supplementation of DHA and lecithin increased the changes induced by DHA supplementation alone. Animals receiving a lecithin‐containing diet also had a higher plasma free choline concentration as compared to controls. In conclusion, dietary DHA‐containing oils and crude lecithin have synergistic effects on increasing plasma and RBC n‐3 PUFA levels, including DHA and EPA. By increasing the systemic availability of dietary DHA, dietary lecithin may increase the efficacy of DHA supplementation when their intake is combined.     

Fucoxanthin Enhances Chain Elongation and Desaturation of Alpha-Linolenic Acid in HepG2 Cells

Dietary fucoxanthin (FX), a carotenoid compound from brown algae, was found to increase docosahexaenoic acid (DHA, 22:6n‐3) and arachidonic acid (ARA, 20:4n‐6) in the liver of mice. DHA and ARA are known to be biosynthesized from the respective precursor α‐linolenic acid (ALA, 18:3n‐3) and linoleic acid (LNA, 18:2n‐6), through desaturation and chain elongation. We examined the effect of FX on the fatty acid metabolism in HepG2 cells (Hepatocellular carcinoma, human). In the first experiment, cells were co‐treated with ALA (100 μM) and FX (0–100 μM) or vehicle for 48 h. FX increased eicosapentaenoic acid (EPA, 20:5n‐3), docosapentaenoic acid (DPA, 22:5n‐3), DHA at concentrations of ≥50 μM. To clarify the change in the metabolism of polyunsaturated fatty acid (PUFA), in the second experiment, cells were co‐treated with universally‐[¹³C]‐labeled (U‐[¹³C]‐) ALA (100 μM) and FX (100 μM) for 0.5, 3, 6, 24 and 48 h. [¹³C] labeled‐EPA, DPA and DHA content in HepG2 cells were all increased by FX after 48 h treatment. Furthermore, estimated delta‐5 desaturase (D5D) but not delta‐6 desaturase (D6D) activity index was increased at 48 h. These results suggested that FX may enhance the conversion of ALA to longer chain n‐3 PUFA through increasing D5D activity in the liver.     

Gamma‐linolenic and stearidonic acids from Moroccan Boraginaceae

Seeds from 20 species belonging to Boraginaceae, subfamilies Boraginoideae and Heliotropioideae, were surveyed in a search for new sources of γ‐linolenic acid (GLA) and stearidonic acid (SDA). Seed oil content ranged from 7.5% in Echium humile ssp. pycnanthum to 28.8% in Anchusa undulata. GLA ranged from 0.2% of total fatty acids in Heliotropium undulatum to 20.2% in Lithodora maroccana. This last species may be considered as new source of GLA. GLA content was also tested in other Lithodora species from the south east of Spain, to compare GLA percentages among related taxa. GLA amounts in all Echium species reached approximately 12%, in good agreement with previous findings in other European Echium species. SDA ranged from an absence in several Cynoglossum species to 16.2% in Echium humile ssp. pycnanthum, which may be considered as a new source of this fatty acid.     

Strategies for the enzymatic enrichment of PUFA from fish oil

PUFA from oil extracted from Nile perch viscera were enriched by selective enzymatic esterification of the free fatty acids (FFA) or by hydrolysis of ethyl esters of the fatty acids from the oil (FA‐EE). Quantitative analysis was performed using RP‐HPLC coupled to an evaporative light scattering detector (RP‐HPLC‐ELSD). The lipase from Thermomyces lanuginosus discriminated against docosahexaenoic acid (DHA) most, resulting in the highest DHA/DHA‐EE enrichment while lipase from Pseudomonas cepacia discriminated against eicosapentaenoic acid (EPA) most, resulting in the highest EPA/EPA‐EE enrichment. The lipases discriminated between DHA and EPA with a higher selectivity when present as ethyl esters (EE) than when in FFA form. Thus when DHA/EPA were enriched to the same level during esterification and hydrolysis reactions, the DHA‐EE/EPA‐EE recoveries were higher than those of DHA/EPA‐FFA. In reactions catalysed by lipase from T. lanuginosus, at 26 mol% DHA/DHA‐EE, DHA recovery was 76% while that of DHA‐EE was 84%. In reactions catalysed by lipase from P. cepacia, at 11 mol% EPA/EPA‐EE, EPA recovery was 79% while that of EPA‐EE was 92%. Both esterification of FFA and hydrolysis of FA‐EE were more effective for enriching PUFA compared to hydrolysis of the natural oil and are thus attractive process alternatives for the production of products highly enriched in DHA and/or EPA. When there is only one fatty acid residue in each substrate molecule, the full fatty acid selectivity of the lipase can be expressed, which is not the case with triglycerides as substrates.