Fatty Acid Profiles of Commercially Available Finfish Fillets in the United States

Fillets of 76 finfish species (293 composites of three fish) were obtained from commercial seafood vendors in six regions of the United States (i.e., Great Lakes, Mid-Atlantic, New England, Northwest, Southeast, and Southwest). Full fatty acid profiles were determined for each species and are presented here. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been associated with many health benefits. Thus, fillets of each species were compared for total EPA plus DHA content, which ranged from 17 mg/100 g (pangasius/swai) to 2430 mg/100 g (Chilean sea bass). Of the top ten most popularly consumed seafoods in the US, finfish, including salmon species (717–1533 mg/100 g), Alaskan pollock (236 mg/100 g), tilapia (76 mg/100 g), channel catfish (44 mg/100 g), Atlantic cod (253 mg/100 g), and pangasius/swai (17 mg/100 g), exhibited a wide concentration range of EPA plus DHA. Large variances were found within many of the farmed species analyzed, which likely stems from dietary differences in the farm-fed diet. The results of this study provide current information on a broad range of species and will help nutritionists and the public make informed decisions regarding seafood consumption.     

DHA与EPA的研究进展

二十二碳六烯酸(Docosahexaenoic acid,22∶6n3,DHA)和二十碳五烯酸(Eicosapentaenoic acid,20∶5n3,EPA)均属于n3类多不饱和脂肪酸(Polyunsatumted fatty acids,PUFAs),能够在一定程度上预防和治疗糖尿病、类风湿性关节炎、自身免疫紊乱等疾病,对人体健康非常重要,因而受到越来越多的关注。本文对DHA与EPA的生理功能、合成机制及其在微藻和真菌中合成的研究现状进行了综述,并对利用转基因技术在哺乳动物体内生产EPA和DHA的前景进行了展望。     

Synthesis of polyunsaturated fatty acid-enriched triglycerides by lipase-catalyzed esterification

This paper reports on the synthesis of triglycerides by enzymatic esterification of polyunsaturated fatty acids (PUFA) with glycerol. A PUFA concentrate obtained from cod liver oil was used to optimize the reaction to favor triglyceride synthesis with lipases. The type and amount of lipase and organic solvent, glycerol content, temperature, water content, and amount and time of addition of molecular sieves were studied. The optimal reaction mixture and conditions were: 9 mL hexane, 60°C, 0.5% (vol/vol) water, 1 g molecular sieves added after 24 h of reaction, glycerol/fatty acid molar ratio 1:3 and 100 mg of Novozym 435 (Novo Nordisk A/S) lipase. Under these conditions, an enriched triglyceride yiedl of 84.7% containing 27.4% eicosapentaenoic acid and 45.1% docosahexaenoic acid was obtained from a cod liver oil PUFA concentrate.     

Effect of salt concentration on production of polyunsaturated fatty acids in <Emphasis Type="Italic">Thraustochytrium aureum</Emphasis> ATCC 34304

This study attempted to characterize the effects of NaCl and MgSO₄ as the primary components of sea salt affecting the yields of production of polyunsaturated fatty acids (PUFAs) by Thraustochytrium aureum ATCC 34304. Reductions in the NaCl concentration of the culture medium suppressed the formation of palmitic acid (PA, C16: 0) but enhanced the production of PUFAs, which induced an increase of the concentration of docosahexaenoic acid (DHA, C22: 6) up to 46.65% from 44.26%. MgSO₄ revealed a similar, yet more highly significant, effect on the fatty acids profile than NaCl. The yields of PUFAs and DHA showed maximum values such as 67.10% and 49.47%, respectively, at the concentration of 10 g L⁻¹ for NaCl and 0 g L⁻¹ for MgSO₄. However, the quantities of mono-and diunsaturated fatty acids, oleic acid (OA, C18: 1) and linoleic acid (LA, C18: 2) at the same concentrations, were compared with those of normal culture medium. Additionally, it was investigated that the increase of culture temperature reduced PUFAs contents but the reductions were recovered by the removal of MgSO₄ form the culture medium, which showed that concentration of salts and culture temperature affected independently the production of PUFAs in T. aureum.     

Microwave-Assisted,Base-Catalyzed Synthesis of Fatty Acid Methyl Esters from Seeds and Fish Oil Supplements

Growing health awareness has resulted in the increased use of dietary supplements derived from plants and marine sources, leaving consumers unsure of their best options. There were three objectives of the present study. The first was to design and evaluate an efficient derivatization procedure. The second was to perform a comparative analysis of liquid oils and their corresponding capsules of hemp, chia, and flax seeds. The final objective was to determine the fatty acid (FA) composition of six fish oil products and compare it to the one provided on the label. For the FA profiling, we implemented two efficient, one-step, sustainable methods with high percentage recovery for the synthesis of FA methyl esters (FAME), which use base catalysis and microwave-assisted heating. Our results found no difference in nutritional value between liquid oils and capsules of the seed supplements, with flaxseed and chia offering a higher, beneficial n-3:n-6 ratio compared to hemp oil. Four of the fish oils analyzed contained significantly less eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) than their reported label, and the other two not only agreed with the manufacturers' declaration but were able to fulfill the daily adequate intake (AI) with fewer capsules.     

Protective Effects of EPA and Deleterious Effects of DHA on eNOS Activity in Ea hy 926 Cultured with Lysophosphatidylcholine

Oxidized low density lipoprotein (Ox-LDL) is a well-established risk factor in atherosclerosis and lysophosphatidylcholine (LysoPtdCho) is considered to be one of the major atherogenic component of Ox-LDL. The purpose of this work was to investigate the effects of two membrane n-3 long chain polyunsaturated fatty acids (n-3 PUFAs), EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) compared to n-6 PUFA, ARA (arachidonic acid), on the activation of endothelial NO synthase (eNOS) by histamine in Ea hy 926 endothelial cells incubated during 24 h in the presence or the absence of LysoPtdCho. DHA (50 μM) produced a ROS induction in cells and aggravated the LysoPtdCho-induced oxidative stress. It did not modify the basal eNOS activity but impaired the stimulation of eNOS induced by histamine and was unable to correct the deleterious effect of LysoPtdCho on histamine-stimulated eNOS activity or phosphorylation of Ser 1177. In contrast, EPA (90 μM) did not modify the ROS level produced in the presence or absence of LysoPtdCho or basal eNOS activity and the stimulating effect of histamine on eNOS. However, it diminished the deleterious effect of LysoPtdCho as well as on the histamine-stimulated eNOS activity on the phosphorylation on Ser 1177 of eNOS. The beneficial effect of EPA but not DHA on endothelial eNOS activity in Ea hy 926 could be also partially due to a slight decrease in membrane DHA content in EPA-treated cells. Consequently, the equilibrium between NO generated by eNOS and ROS due to oxidative stress could explain, in part, the beneficial effect of EPA on the development of cardiovascular diseases. By contrast ARA an n-6 PUFA was devoid of any effect on ROS generation or eNOS activity in the basal state or after histamine-induced stimulation. In vivo experiments should be undertaken to confirm these results.     

One-Step Extraction and Concentration of Polyunsaturated Fatty Acids from Fish Liver

The fatty acids (FA) eicosapentaenoic acid (20:5ω-3; EPA) and docosahexaenoic acid (22:6ω-3; DHA), which have several health benefits, have been concentrated from mako shark liver (Isurus oxyrinchus). The process was carried out in one single step, in which fish liver oil was simultaneously extracted, saponified and concentrated. Additionally, the polyunsaturated fatty acids (PUFA) concentrate was winterized to crystallize the remaining saturated FA, resulting in a further increase in the concentration of DHA and EPA. Two variables, temperature and water concentration in the saponification mixture, were optimized to increase the concentration of ω-3 PUFA. Best results were obtained at 12 °C and 0% water content in the mixture, obtaining 17.8% purity and 77.6% yield of EPA; DHA purity and yield were 33.3 and 82.2%, respectively.     

Muscle Lipids and Fatty Acid Profiles of the Sea Catfish (Arius madagascariensis) in Madagascar Inland Waters

Muscle lipids and fatty acids (FA) of catfish Arius madagascariensis were determined in catfish caught in the Betsiboka River, Madagascar, during a 5-month sampling period. Total lipids from muscle were extracted and quantified. Fatty acids were identified by means of gas chromatography–mass spectrometry of FA methyl esters and FA pyrrolidides, leading to the identification of 42 FA. Lipid content was relatively high in our fish sample and ranged from 4.3 to 6.6% of wet muscle. Three FA dominated the FA composition: palmitic acid (C16:0, 22.9–32.6%), oleic acid (C18:1n-9, 11.3–13.4%) and stearic acid (C18:0, 10.8–12.0%). A number of polyunsaturated FA (PUFA) were present in appreciable amounts, including arachidonic acid (C20:4n-6, 4.7–7.6%), docosahexaenoic acid (C22:4n-6, 3.0–8.1%), eicosapentaenoic acid (C20:5n-3, 0.6–1.0%), n-3 docosapentaenoic acid (C22:5n-3, 1.1–1.6%), n-6 docosatetraenoic acid (C22:4n-6, 0.7–1.2%) and n-6 docosapentaenoic acid (22:5n-6, 0.9–1.8%). The sum of the n-6 PUFA and n-3 PUFA was 11.3–18.8 and 7.5–13.4%, respectively. These results indicate that A. madagascariensis, an abundant freshwater fish in Madagascar rivers, may be good source of dietary PUFA.     

Chemometric Characterization and Classification of Selected Freshwater and Marine Fishes from Turkey Based on their Fatty Acid Profiles

The fatty acid (FA) profiles of edible muscle of selected commercially important freshwater and marine fish species from Turkey were investigated. The fatty acid compositions of freshwater fish species were 23.00–29.60% saturated (SFA), 25.70–36.50% monounsaturated (MUFAs), and 26.59–31.92% polyunsaturated acids (PUFAs), whereas the fatty acid compositions of marine fish consisted of 21.08–36.90% (SFA), 18.03–51.45% MUFAs, and 20.92–53.17% PUFAs. There was a wide variation and significant (P < 0.05) differences among the fatty acid profiles of the freshwater and marine fish samples, including differences in the SFA, MUFA, PUFA, EPA, DHA, DHA/EPA, total n-3 PFAs, total n-6 PUFAs and n-3/n-6 values. In addition, the cheap marine fish species such as anchovy and European pilchard, bogue are better dietary sources of n-3 PUFAs than more expensive species such as bluefish, Atlantic mackerel, sea bream and sea bass. Through the application of two multivariate statistical methods, Principal Component and Hierarchical Analysis, fish species from Turkey waters were classified according to the geographical locations categorized in terms of fatty acid profiles. Clustering by fish species also gave rise to defined groups.     

Enrichment of docosahexaenoic acid from tuna oil via lipase-mediated esterification under pressurized carbon dioxide

This study focused on the use of pressurized CO₂ as a reaction medium for the enrichment of docosahexaenoic acid (DHA) from tuna oil fatty acids via lipase-mediated esterification. Of the three lipases tested, Lipozyme RM IM from Rhizomucor miehei was selected for further study. Enzyme loading, water addition, and reaction time were also explored. Near-supercritical CO₂, prepared at 25 °C and 8.3 MPa, was the most effective reagent tested for enriching DHA from the residual fatty acid fraction. In addition to near-supercritical CO₂, optimal conditions included addition of 0.2 wt% (based on total substrates) water, enzyme loading of 5 wt% (based on total substrates), and a reaction time of 18 h. The DHA concentration and recovery yield for the residual fatty acid fraction under these optimal conditions were 75.8 wt% and 81 wt%, respectively.     

Eicosapentaenoic acid (20∶5n-3) from the marine microalgaPhaeodactylum tricornutum

Eicosapentaenoic acid (EPA, 20∶5n-3) was obtained from the marine microalgaePhaeodactylum tricornutum by a three-step process: fatty acid extraction by direct saponification of biomass, polyunsaturated fatty acid (PUFA) concentration by formation of urea inclusion compounds, and EPA isolation by semipreparative high-performance liquid chromatography (HPLC). Alternatively, EPA was obtained by a similar two-step process without the PUFA concentration step by the urea method. Direct saponification of biomass was carried out with two solvents that contained KOH for lipid saponification. An increase in yield was obtained because the problems associated with emulsion formation were avoided by separating the biomass from the soap solution before adding hexane for extraction of insaponifiables. The most efficient solvent, ethanol (96%) at 60°C for 1 h, extracted 98.3% of EPA. PUFA were concentrated by the urea method with a urea/fatty acid ratio of 4∶1 at a crystallization temperature of 28°C and by using methanol and ethanol as urea solvents. An EPA concentration ratio of 1.73 (55.2∶31.9) and a recover yield of 78.6% were obtained with methanol as the urea solvent. This PUFA concentrate was used to obtain 93.4% pure EPA by semipreparative HPLC with a reverse-phase, C₁₈, 10 mm i.d.×25-cm column and methanol/water (1% acetic acid), 80∶20 w/w, as the mobile phase. Eighty-five percent of EPA loaded was recovered, and 65.7% of EPA present inP. tricornutum biomass was recovered in highly pure form by this three-step downstream process. Alternatively, 93.6% pure EPA was isolated from the fatty acid extract (without the PUFA concentration step) with 100% EPA recovery yield. This two-step process increases the overall EPA yield to 98.3%, but it is only possible to obtain 20% as much EPA as that obtained by three-step downstream processing.     

Fatty acid profiles in tissues of mice fed conjugated linoleic acid

The incorporation of vaccenic acid (VA, 0.5 and 1.2%), conjugated linoleic acid (CLA, mixture of primarily c9,t11‐ and t10,c12‐CLA, 1.2%), linoleic acid (LA, 1.2%) and oleic acid (OA, 1.2%) into different tissues of mice was examined. The effects on the fatty acid composition of triacylglycerols (TAG) and phospholipids (PL) in kidney, spleen, liver and adipose tissue were investigated. VA and CLA (c9,t11‐ and t10,c12‐CLA) were primarily found in TAG, especially in kidney and adipose tissue, respectively. Conversion of VA to c9,t11‐CLA was indicated by our results, as both fatty acids were incorporated into all the analyzed tissues when a diet containing VA but not c9,t11‐CLA was fed. Most of the observed effects on the fatty acid profiles were seen in the CLA group, whereas only minor effects were observed in the VA groups compared with the OA group. Thus, CLA increased n‐3 polyunsaturated fatty acids (PUFA) in PL from kidney and spleen and lowered the ratio of n‐6/n‐3 PUFA in these tissues. Furthermore, CLA increased C₂₂ PUFA in the PL fraction of kidney, spleen and liver, but reduced the level of arachidonic acid in PL of liver and spleen and lowered the Δ⁹‐desaturation indexes in all analyzed tissue TAG.     

Modification of Palm Oil for Anti-Inflammatory Nutraceutical Properties

Palm oil is one of the most important edible oils in the world. Its composition (rich in palmitate and oleate) make it suitable for general food uses but its utility could be increased if its fatty acid quality could be varied. In this study, we have modified a palm olein fraction by transesterification with the n-3 polyunsaturated fatty acids, α-linolenate or eicosapentaenoic acid (EPA). Evaluation of the potential nutritional efficacy of the oils was made using chondrocyte culture systems which can be used to mimic many of the degenerative and inflammatory pathways involved in arthritis. On stimulation of such cultures with interleukin-1α, they showed increased expression of cyclooxygenase-2, the inflammatory cytokines tumour necrosis factor-α (TNF-α), IL-1α and IL-1β and the proteinase ADAMTS-4. This increased expression was not affected by challenge of the cultures with palm olein alone but showed concentration-dependent reduction by the modified oil in a manner similar to EPA. These results show clearly that it is possible to modify palm oil conveniently to produce a nutraceutical with effective anti-inflammatory properties.     

Optimization of fatty acid extraction from Phaeodactylum tricornutum UTEX 640 biomass

Fatty acids in the microalga Phaeodactylum tricornutum were isolated using an optimized three-step method: extraction of crude fatty acid potassium salts made by direct saponification of lipids in the microalgal biomass with KOH/ethanol (96%, vol/vol), separation of unsaponifiable lipids by extraction with hexane, and final purification of fatty acids by acidification of the alcoholic solution of potassium soaps followed by extraction of fatty acid into hexane. Direct saponification was carried out in ethanol (96%, vol/vol) using 2.09 mL ethanol (96%) per gram of wet biomass (10 mL/g of dry biomass) mixed with 0.4 g KOH/g of biomass. Under these conditions the fatty acid yield was 87%. The optimal water content of the alcoholic solution for extraction of the unsapononifiables was established as 40%, w/w. Data on equilibrium carotenoid distribution between the alcoholic (40%, w/w water) and hexane phases were determined. These data allow prediction of the carotenoid yields with different volumes of hexane in several extraction steps. The optimal pH of the alcoholic solution before extracting the purified fatty acid was established as pH 6, and the equilibrium fatty acid distribution between the alcoholic and hexane phases was determined. This optimized method permited a 20% reduction in the production costs of highly purified eicosapentaenoic acid (EPA) in the three-step preparative process (extraction of fatty acid, concentration of polyunsaturated fatty acids by the urea method, and EPA fractionation through preparative high-performance liquid chromatography) previously developed by the authors.     

Effect of temperature programming on the performance of urea inclusion compound-based free fatty acid fractionation

The effect of cooling rate on the degree of removal of saturated acyl groups from FFA derived from canola oil and the isolation of di- and polyunsaturated acyl groups from FFA derived from vegetable and fish oil, respectively, during urea inclusion compound (UIC)-based fractionation was investigated. Traditionally, slow cooling has been used (ca.−1°C min⁻¹). A more rapid cooling rate (−47°C min⁻¹) produced UIC crystals of similar morphology and thermodynamic properties, but of a size an order of magnitude smaller than the UIC formed during slow cooling. Fractionations used only renewable materials (urea, FFA, and 95% ethanol as solvent) and benign operating conditions (ambient pressure, 25–75°C, and neutral pH). When the recovery of FFA (in the solvent-rich phase) was relatively high (>60%), the selectivity of UIC-based fractionation toward the inclusion of saturated FFA and against polyunsaturated FFA was not affected by the cooling rate. In contrast, when the FFA recovery was low, representing cases in which an increase of the PUFA purity is a more important economic goal, a slower cooling rate resulted in a significantly greater discrimination against PUFA groups, hence to a FFA product with a measurably greater purity. This paper was presented at the 96th AOCS Anual Meeting and Expo, Salt Lake City, Utah, on May 4, 2005.