Docosahexaenoic Acid Ethyl Ester Research Articles

Dietary sesamin and docosahexaenoic and eicosapentaenoic acids synergistically increase the gene expression of enzymes involved in hepatic peroxisomal fatty acid oxidation in rats

The interaction of sesamin, one of the most abundant lignans in sesame seed, and highly purified docosahexaenoic acid (DHA) or eicosapentaenoic acid (EPA) in the form of ethyl ester in affecting hepatic fatty acid oxidation was examined in rats. In the first experiment, 3 groups of rats were fed with purified experimental diets free of n-3 fatty acid ethyl ester and containing 0%, 0.2%, and 0.4% sesamin (1:1 mixture of sesamin and episesamin), and 2 groups of animals were fed with a 2% DHA ethyl ester diet containing either 0% or 0.2% sesamin. In the second trial, 4 groups of rats were fed with either a 0% or a 2% EPA ethyl ester diet containing 0% or 0.2% sesamin. After 15 days of feeding, DHA and EPA ethyl esters added to a sesamin-free diet little affected the activity and messenger RNA (mRNA) levels of various enzymes involved in fatty acid oxidation. Sesamin increased the activity levels of various hepatic enzymes involved in fatty acid oxidation irrespective of the presence or absence of n-3 fatty acid ethyl ester in diets. However, the diet containing sesamin and DHA or EPA ethyl ester in combination increased many of these parameters synergistically. In particular, the peroxisomal palmitoyl-coenzyme A oxidation rate and acyl-coenzyme A oxidase activity level were much higher in rats fed with sesamin and DHA or EPA in combination than in animals fed with a diet free of n-3 fatty acid ethyl ester and containing sesamin. Analyses of mRNA levels revealed that a diet simultaneously containing sesamin and n-3 fatty acid ethyl ester increased the gene expression of various enzymes involved in peroxisomal fatty acid oxidation in a synergistic manner. However, the combination of sesamin and n-3 fatty acid ethyl esters was ineffective in causing a synergistic increase in mRNA levels of enzymes of mitochondrial fatty acid oxidation, microsomal cytochrome P-450 IV A1, and cytosolic liver-type fatty acid–binding protein. It was concluded that sesamin and DHA or EPA ethyl ester synergistically increased hepatic fatty acid oxidation primarily through up-regulation of the gene expression of peroxisomal fatty acid oxidation enzymes. The results essentially reproduced those observed in our previous study with a diet containing both fish oil and sesamin despite the fact that DHA and EPA ethyl esters were much less effective than fish oil in increasing hepatic fatty acid oxidation.

Reduction in Plasma Glucose after Lipid Changes in Mice Fed Fish Oil, Docosahexaenoic Acid, and Eicosapentaenoic Acid Diets

Background/Aim: Effects of the dietary docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and fish oil on weekly changes in plasma glucose, total cholesterol, triacylglycerol, and phospholipid concentrations of male Crlj:CD-1 mice were investigated. Method: Animals were fed five different experimental diets which contained 6.0% lard (lard diet), 6.0% fish oil (fish oil diet), 1.5% DHA-ethyl ester + 4.5% lard (DHA diet), 0.4% EPA-ethyl ester + 5.6% lard (EPA diet), and 1.5% DHA-ethyl ester + 0.4% EPA ethyl ester + 4.1% lard (DHA+EPA diet) for 17 weeks. Glucose and lipid concentrations in plasma collected at weeks 0, 1, 2, 4, 6, 8, 12, and 16 were measured. Results: Plasma phospholipid concentrations were significantly lower in mice fed the fish oil and DHA+EPA diets than in those fed the lard diet at week 2. Plasma total cholesterol and glucose concentrations were significantly lower in the fish oil diet group than in the lard diet group at weeks 6 and 8, respectively. Conclusion: These results indicate that the decreases in plasma glucose concentrations in response to intakes of DHA and EPA in mice take place over a longer period of time than similar decreases in the plasma lipid concentrations.

Detection of radical development by ESR spectroscopy techniques for assessment of oxidative susceptibility of fish oils

Detection of radical development by two different Electron Spin Resonance (ESR) spectroscopy techniques has been evaluated for obtaining objective analytical information about oxidative susceptibility of fish oils under mild oxidation conditions. Two oils from different by-products in the fish industry, salmon viscera oil (SVO) and cod liver oil (CLO), were used. In addition, radical formation in the ethyl ester of docosahexaenoic acid (DHA) was studied as representing polyunsaturated fatty acids in fish oils that are very prone to oxidation. The ESR spin trapping technique, using the spin trap α-phenyl-N-tert-butylnitrone, and the ESR spin scavenging technique, using the stable nitroxyl radical 2,2,6,6-tetramethyl-1-piperidinyl-1-oxyl (TEMPO) to be scavenged by radicals generated in the oxidative process, were applied to detect radical development at 40 °C in the dark. For comparative purposes, oxidative susceptibility was evaluated by determination of peroxide value (PV) and the TBARS test under the same oxidation conditions. Results were also compared to the oil stability index (OSI) obtained at 60 °C. Results obtained by ESR spin trapping were consistent with results obtained in the OSI test, as well as those obtained for PV and the TBARS test. Therefore, detection of radical formation by ESR spin trapping provided objective information upon the relative oxidative susceptibility of SVO and CLO. On the other hand, results obtained by ESR spin scavenging were not concluding to establish the different oxidative susceptibility of the two oils found by the other determinations applied. The kinetic curves of TEMPO were similar for both oils, which suggests that mechanisms other than that based on the expected radical-radical interactions might be involved.

Vapor–liquid equilibria and densities of CO 2 with four unsaturated fatty acid esters at elevated pressures

In this study experimental P– T– x– y equilibrium data for four binary mixtures over a wide range of pressure (10.44–23.54 MPa) were determined at 313 K and 333 K. Liquid and vapor densities of carbon dioxide + four fatty acid ester systems, including oleic acid methyl ester, linoleic acid methyl ester, eicosapentaenoic acid ethyl ester, and docosahexaenoic acid ethyl ester were measured by using two circulating systems consisting of two vibrating tube densitometers. The vapor-phase density was observed to increase more significantly with pressure than the liquid-phase density at constant temperature. Experimental equilibrium constants of oleic acid methyl ester and linoleic acid methyl ester were found to be larger than those of eicosapentaenoic acid ethyl ester, docosahaxaenoic acid ethyl ester, linoleic acid, triolein, and tocopherol. This indicates that the two methylated fatty acids would be extracted easier than the other compounds in a separation process using supercritical CO 2 extraction. The equilibrium data were successfully correlated using the Peng–Robinson and modified Soave–Redlich–Kwong equations of state with quadratic (two parameters), Panagiotopoulos–Reid (three parameters), and Adachi–Sugie (three parameters) mixing rules. In general, the Soave–Redlich–Kwong equation of state with the Panagiotopoulos–Reid mixing rules and the quadratic mixing rules give the best correlation for methylated fatty acids and ethylated fatty acids, respectively.

Supercritical CO2 extraction and concentration of n-3 polyunsaturated fatty acid ethyl esters from tuna cooking juice

Cooking is an important step in the tuna canning process; it usually produces functional solubilized proteins and lipids. The objective of this study was to recover and increase the concentration of functional n−3 fatty acids from the lipids in cooking juice. The lipids contained 12.98% eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) after ethyl esterification and increased to 37.4% with subsequent urea adduct fractionation. Supercritical carbon dioxide extraction was further used to increase the concentration of EPA and DHA ethyl esters. The ratio of EPA+DHA ethyl esters (high-molecular-weight components) to that of C16 and C18∶1 fatty acid ethyl esters (low-molecular-weight components) was used as a separation index for evaluating the process variables. Experimental results indicated that a high CO2 density caused a low separation factor. At 1500 psig and 328.2 K, the extraction collected over 600 L CO2, displaying an accepted concentration factor of EPA+DHA ethyl esters herein. About 80% yield of EPA and DHA was obtained and the ethyl esters increased from 37.4% to 54.3%.

Effect of Supplementation with Docosahexaenoic Acid Ethyl Ester and sn-2 Docosahexaenyl Monoacylglyceride on Plasma and Erythrocyte Fatty Acids in Rats

Background/Aims: Docosahexaenoic acid (C22:6, DHA) is an omega-3 fatty acid required for the normal development of the mammalian nervous and visual system. DHA is provided by the mother during pregnancy and lactating period. Mother’s DHA supplementation during pregnancy, and even before pregnancy, has been suggested. DHA can be provided by marine oils, egg’s yolk phospholipids, single cell algae oils, the pure fatty acid, or by the ethyl ester derivative (DHA-EE). Another way to provide DHA can be by sn-2 docosahexaenyl monoacylglyceride (DHA-MG), obtained by the treatment of fish oil with stereospecific lipases. sn-2 Fatty acid monoacylglycerides can be more easily absorbed at the intestine than other fatty acid derivatives. Methods: Female rats fed with a synthetic, which provided essentially no DHA, received a 40-day supplementation of either DHA-EE or DHA-MG. Plasma and erythrocyte fatty acid composition were assessed by gas chromatography at day 0 and 40 of supplementation. Results: DHA-EE increased plasma and erythrocyte DHA by 15 and 11.9%, respectively, with no modification of arachidonic acid (AA) content. DHA-MG supplementation increased plasma and erythrocyte DHA by 24 and 23.8%, respectively, but reduced AA by 5.5 and 3%, respectively. Conclusions: We conclude that in the rat, DHA-MG supplementation allows a higher plasma and erythrocyte DHA content than DHA-EE with minor modification of AA content.

Lack of Chemoprevention or Promotion Effects of Docosahexaenoic Acid on Small Intestine, Colon, Liver, Lung, Thyroid, Esophagus, Kidney, and Forestomach Carcinogenesis in a Rat Medium-Term Multi-Organ Carcinogenesis Model

Modifying effects of docosahexaenoic acid (DHA) were examined using a medium-term multi-organ carcinogenesis model (DMBDD model). Groups of twenty F344 male rats were treated sequentially with N-diethylnitrosamine (DEN, i.p.), N-methyl-N-nitrosourea (MNU, i.p.), 1,2-dimethylhydrazine (DMH, s.c.), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN, in drinking water) and dihydroxy-di-N-propylnitrosamine (DHPN, in drinking water) during the first 4 weeks (DMBDD treatment), and then DHA-ethyl ester (DHA-E), DHA-triglyceride (DHA-TG) and/or tocopherol were administered intragastrically 3 times a week for 31 weeks. Significant inhibition of the development of glutathione S-transferase placental form (GST-P) positive foci was observed in DMBDD treated 30% DHA-TG 404 mg and 128 mg + tocopherols groups and with tocopherol alone; however, this appeared to be due to the tocopherol. DHA treatment did not influence the development of aberrant crypt foci in the large intestine. Histopathologically, the incidences of preneoplastic and neoplastic lesions in other organs were also not increased or decreased by DHA treatment. Thus, the results indicate a lack of chemopreventive and tumor promotion effects of any type of DHA in male rats under the present experimental conditions.

Dietary Docosahexaenoic Acid Suppresses T Cell Protein Kinase Cθ Lipid Raft Recruitment and IL-2 Production

To date, the proximal molecular targets through which dietary n-3 polyunsaturated fatty acids (PUFA) suppress the inflammatory process have not been elucidated. Because cholesterol and sphingolipid-enriched rafts have been proposed as platforms for compartmentalizing dynamically regulated signaling assemblies at the plasma membrane, we determined the in vivo effects of fish oil and highly purified docosahexaenoic acid (DHA; 22:6n-3) on T cell microdomain lipid composition and the membrane subdomain distribution of signal-transducing molecules (protein kinase C (PKC)theta;, linker for activation of T cells, and Fas/CD95), before and after stimulation. Mice were fed diets containing 5 g/100 g corn oil (control), 4 g/100 g fish oil (contains a mixture of n-3 PUFA) plus 1 g/100 g corn oil, or 4 g/100 g corn oil plus 1 g/100 g DHA ethyl ester for 14 days. Dietary n-3 PUFA were incorporated into splenic T cell lipid raft and soluble membrane phospholipids, resulting in a 30% reduction in raft sphingomyelin content. In addition, polyclonal activation-induced colocalization of PKCtheta; with lipid rafts was reduced by n-3 PUFA feeding. With respect to PKCtheta; effector pathway signaling, both AP-1 and NF-kappaB activation, IL-2 secretion, and lymphoproliferation were inhibited by fish oil feeding. Similar results were obtained when purified DHA was fed. These data demonstrate for the first time that dietary DHA alters T cell membrane microdomain composition and suppresses the PKCtheta; signaling axis.

Effect of n-3 fatty acids on serum lipid levels and hepatic fatty acid metabolism in BALB/c.KOR- Apoe shl mice deficient in apolipoprotein E expression

N-3 fatty acids exert a potent serum lipid-lowering effect in rodents mainly by affecting hepatic fatty acid oxidation and synthesis. However, it has been observed that fish oil and docosahexaenoic acid ethyl ester do not lower serum lipid levels in apolipoprotein E (apoE)-knockout ( Apoe tm1Unc ) mice generated by gene targeting. To test the hypothesis that apoE expression is required for n-3 fatty acid–dependent regulation of serum lipid levels and hepatic fatty acid metabolism, we examined the effect of fish oil and n-3 fatty acid ethyl esters on the activity and gene expression of hepatic enzymes involved in fatty acid oxidation and synthesis using an alternative apeE-deficient mouse model with the BALB/c genetic background (BALB/c.KOR- Apoe shl ). ApoE-deficient mice were fed diets containing 9.4% palm oil, fish oil, or 5.4% palm oil and 1% EPA plus 3% DHA ethyl esters for 15 days. In contrast to the reported data on apoE-knockout mice, fish oil and n-3 fatty acid ethyl esters greatly decreased serum triacylglycerol, cholesterol, and phospholipid levels in the Apoe shl mice. The decreases were greater with fish oil than with ethyl esters. The alterations by dietary n-3 fatty acids of serum lipid levels were accompanied by parallel changes in the activity and mRNA levels of enzymes involved in hepatic fatty acid oxidation and synthesis. The reason for the discrepancy between the results of the current study and previous studies is unknown. However, our study at least indicates that a lack of apoE expression does not necessarily accompany deficits in the n-3 fatty acid–dependent regulation of serum lipid levels and hepatic fatty acid metabolism.

Effect of Dietary Docosahexaenoic Acid and Catechins on Maze Behavior in Mice

Background/Aims: Docosahexaenoic acid (DHA; 22:6 n–3) and catechins are food components that play an important role in maintaining human health. However, the effect of a simultaneous intake of DHA and catechins on brain function is unknown. The purpose of this study was to investigate the effect of DHA and catechins on maze behavior in mice. Method: Adult (5 months old) and old (15 months old) male mice were fed 5% lard diets containing 0 or 1.5% DHA ethyl ester (DHA-EE), either with or without 0.5% catechins, for 3.5 months. Maze behavior was assessed 3 months after the start of the feeding experiment. The time required and distance traveled to reach the maze exit, and the number of times that a mouse strayed into blind alleys in the maze were measured. The fatty acid compositions of plasma and brain lipids were measured after the maze behavior experiment. Results: Adult mice in the catechin, DHA-EE, and DHA-EE + catechin diet groups required less time and traveled a shorter distance to reach the maze exit, and strayed into blind alleys fewer times than those in the corresponding lard groups. Among old mice, the DHA-EE + catechin diet group showed an improvement in maze behavior. No marked differences in the brain fatty acid composition between lard and catechin diet groups were observed; in the DHA-EE intake groups, the brain DHA percentage was raised. Conclusion: These results suggest that a simultaneous intake of DHA and catechins may certainly enhance brain function in both adult and old mice.

Divergent effects of eicosapentaenoic and docosahexaenoic acid ethyl esters, and fish oil on hepatic fatty acid oxidation in the rat

The physiological activity of fish oil, and ethyl esters of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) affecting hepatic fatty acid oxidation was compared in rats. Five groups of rats were fed various experimental diets for 15 days. A group fed a diet containing 9.4% palm oil almost devoid of n-3 fatty acids served as a control. The test diets contained 4% n-3 fatty acids mainly as EPA and DHA in the form of triacylglycerol (9.4% fish oil) or ethyl esters (diets containing 4% EPA ethyl ester, 4% DHA ethyl ester, and 1% EPA plus 3% DHA ethyl esters). The lipid content of diets containing EPA and DHA ethyl esters was adjusted to 9.4% by adding palm oil. The fish oil diet and ethyl ester diets, compared to the control diet containing 9.4% palm oil, increased activity and mRNA levels of hepatic mitochondrial and peroxisomal fatty acid oxidation enzymes, though not 3-hydroxyacyl-CoA dehydrogenase activity. The extent of the increase was, however, much greater with the fish oil than with EPA and DHA ethyl esters. EPA and DHA ethyl esters, compared to the control diet, increased 3-hydroxyacyl-CoA dehydrogenase activity, but fish oil strongly reduced it. It is apparent that EPA and DHA in the form of ethyl esters cannot mimic the physiological activity of fish oil at least in affecting hepatic fatty acid oxidation in rat.

Essential fatty acids for larval mud crab Scylla serrata: implications of lack of the ability to bioconvert C18 unsaturated fatty acids to highly unsaturated fatty acids

This study was conducted to examine the effect of essential fatty acids (EFA) on the survival, development and bioconversion of fatty acids in mud crab Scylla serrata larvae. Mud crab larvae held in 1-l plastic beakers (30 ind/l) were fed rotifers that had been enriched with oleic acid (18:1 n−9, OA), linoleic acid (18:2 n−6, LA), linolenic acid (18:3 n−3, LNA), eicosapentaenoic acid (20:5 n−3, EPA) and docosahexaenoic acid (22:6 n−3, DHA) ethyl ester oil during the zoea (Z)1 and Z2 stage. Upon reaching the Z3 stage, rotifers were shifted to unenriched Artemia or Artemia enriched with either EPA or DHA ethyl ester. Further in order to allow comparison of the effect of the enriched rotifers on the fatty acid composition of the Z2 stage larvae, larvae fed enriched rotifers were harvested upon reaching the Z2 stage for fatty acid analysis. The survival of mud crab larvae was more strongly affected by the EFA contained in the Artemia compared to rotifers. Mud crab larvae fed unenriched Artemia showed EFA deficiency signs such as lower survival, longer intermolt period, and a narrower carapace width at the first crab stage, indicating that DHA was superior to that of EPA and followed by LNA and LA. The fatty acid composition of the whole body of Z2 larvae fed rotifers enriched with OA, LA or LNA revealed that the content (g/100 g larvae) of EPA decreased from 1.2 to 0.4–0.8 and DHA decreased from 0.5 to 0.1–0.2, respectively. Moreover, the contents of monoenes increased from 1.4 to 2.5–3.2, indicating dietary EFA deficiency. We conclude that mud crab larvae have a limited or negligible capability to convert C18 unsaturated fatty acids to highly unsaturated fatty acids.

Effects of simultaneous docosahexaenoic acid and catechin intakes on the plasma and liver lipids in low- and high-fat diet fed mice

The purpose of this study was to clarify the synergistic effects of fish oil and tea components on plasma and liver lipids in mice fed low- and high-fat diets. Male mice (5 months old) were fed for 4 months on low (5%) or high (20%) fat diets containing 0%, 0.1%, or 1% docosahexaenoic acid ethyl ester (DHA-EE) either with or without 0.03% catechin. The plasma total cholesterol (T-Chol) content of mice fed the 1% DHA-EE + 0.03% catechin diet was the lowest among the experimental low-fat diet groups. The plasma total and free cholesterol and phospholipids were significantly lower in the mice fed 1% DHA-EE + 0.03% catechin diet than in animals fed 1% DHA-EE or 0.03% catechin diets. However, there were no marked differences in the plasma and liver lipid components between any of the experimental high-fat diet groups. In mice fed either the low- or high-fat diet, plasma and liver DHA percentages rose with the increasing of DHA-EE supplementation, while the catchins supplementation hardly influenced the plasma and liver fatty acid composition. These results suggest that simultaneous intakes of DHA and catechins may be effective in the improving plasma lipid levels in animals fed low-fat diet.

Regiospecific distribution of fatty acids in triacylglycerols of Artemiafranciscana nauplii enriched with fatty acid ethyl esters

This paper reports the positional distribution of fatty acids in triacylglycerols (TAG) of Artemia franciscana nauplii enriched with each of palmitic (16:0), oleic (18:1n-9), linoleic (18:2n-6), linolenic (18:3n-3), eicosapentaenoic (20:5n-3), and docosahexaenoic (22:6n-3) acid ethyl esters. TAG extracted from the enriched and unenriched nauplii were subjected to regiospecific analysis to determine the fatty acid compositions of the sn-1(3) and sn-2 positions of TAG. In the unenriched nauplii, 16:0, 18:1n-9, and 18:2n-6 were preferentially located in the sn-1(3) position followed by the sn-2 position [i.e. sn-1(3)> sn-2], whereas 18:3n-3 was concentrated in the sn-2 position [i.e. sn-2> sn-1(3)]. Contents of 20:5n-3 and 22:6n-3 were low. After the nauplii were enriched with each of the ethyl esters for 18 h, fatty acid fed to the nauplii showed higher content in the sn-1(3) position than in the sn-2 position [i.e. sn-1(3)> sn-2]. Distribution pattern of 18:3n-3 changed from sn-2> sn-1(3) to sn-1(3)> sn-2 during the enrichment with 18:3n-3 ethyl ester. Increases in all of the fatty acids in TAG were attributed to that in the sn-1(3) position much more than that in the sn-2 position. Artemia nauplii appear to be characterized by preferential incorporation of exogenous fatty acids into the sn-1(3) position of TAG, even though endogenous fatty acids are esterified in the opposite position.

Dose-response effect of docosahexaenoic acid ethyl ester on maze behavior and brain fatty acid composition in adult mice.

The dose-response effect of dietary docosahexaenoic acid (DHA, 22:6 n-3) ethyl ester (EE) on maze-learning ability in mice was studied. Male Crj:CD-1 mice aged three months were fed a) a diet containing 5 g palm oil/100 g diet (control group); b) a diet containing 0.5 g DHA ethyl ester/100 g diet plus 4.5 g palm oil/100 g diet (DHA-EE 0.5% group); c) a diet containing 1 g DHA ethyl ester/100 g diet plus 4 g palm oil/100 g diet (DHA-EEE 1% group); d) a diet containing 2 g DHA ethyl ester/100 g diet plus 3 g palm oil/100 g diet (DHA-EE 2% group) for four months. Maze-learning ability was assessed three months after the start of the experiment. The time required to reach the maze exit and the number of times that a mouse strayed into blind alleys in the maze were measured in three trials, performed every four days. In trial 1, the DHA-EE 0.5%, 1% and 2% groups required less (p < 0.05) time to reach the maze exit, and the DHA-EE 2% group strayed (p < 0.05) into blind alleys fewer times than the control group. In trial 3 performed four days after the second trial, the DHA-EE 2% group needed less (p < 0.05) time to find the exit and spent a fewer (p < 0.05) number of times in blind alleys than did the control group. In the total lipids of plasma and brain of mice fed DHA, increasing intakes of DHA resulted in an increase in DHA levels, with a corresponding decrease in arachidonic acid (20:4 n-6). Improved maze-learning ability in mice fed DHA-EE 2% was associated with higher DHA levels in brain. Our resulted suggest that there are no linear dose-response effects of DHA on maze-learning ability, however, the intake of DHA-EE 2% diet improves learning ability in adult mice as demonstrated by maze performance.

Effects of Deamidation and Fragmentation on Antioxidative Activity of .ALPHA.-Zein.

The effcts of deamidation of fragmentation on the antioxidative activity of α-zein were investigated individually. Heat treatment at 70°C in 70% ethanol-0.05M HCl caused deamidation of α-zein without fragmentation. Antioxidative activity of α-zein was improved by this deamidation. α-Zein with deamidation treatment for 12 hours protected 80% of docosahexaenoic acid ethyl ester from autoxidation until 7 days. Model peptide of α-zein had a lower antioxidative activity than α-zein. Fragmentation by N-btromosuccinimide decreased the antioxidative activity of α-zein.

Autoxidation kinetic analysis of docosahexaenoic acid ethyl ester and docosahexaenoic triglyceride with oxygen sensor.

The application of omega-3 polyunsaturated fatty acids (PUFAs) as food additives is restricted by their chemically quite reactive properties. However, quantitative analyses of the oxidative kinetics of PUFAs are very few compared to other studies on food chemistry. In this study, the autoxidation kinetics of ethyl docosahexaenoate (DHAEE), docosahexaenoic triglyceride (DHA oil), and emulsified DHA oil were investigated with an oxygen sensor. The autocatalytic reaction rate constants for DHAEE, DHA oil, and the emulsified DHA oil with 20% (w/v) GA, 20% SSPS, or 20% SSPS containing 5% soy protein were obtained at 35, 50, and 70 degrees C. A plot of the natural logarithm of the frequency factor, In ka0, vs. the activation energy, Ea, demonstrated that In ka0 against Ea fitted well with a single straight line both for the data from this study and for other reported results. This implies that the chemical compensation relationship holds between ka0 and Ea for PUFA and emulsified DHA oil.

Purification of Docosahexaenoic Acid Ethyl Ester Using a Silver-Ion-Immobilized Porous Hollow-Fiber Membrane Module

Docosahexaenoic acid ethyl ester (DHA-Et) was purified by adsorption on Ag-ion-immobilized membranes via selective interaction between silver ion and carbon-carbon double bonds of DHA-Et. Silver ions were immobilized onto sulfonic-acid-group-containing porous hollow-fiber membranes at an Ag ion density of 1.4 mol/kg of membrane, and 30 membranes were housed in one module (inner diameter = 18 mm and effective length = 80 mm). The adsorption isotherms of DHA-Et in various organic solvents revealed that DHA-Et was adsorbed on the immobilized Ag ions with a DHA-Et/Ag ion molar binding ratio of 1/5 in methanol, and that acetonitrile was the solvent of choice for the elution of the adsorbed DHA-Et. Permeation of bonito oil ethyl ester solution in methanol through the Ag-ion-immobilized hollow-fiber membrane module demonstrated that the displacement adsorption of other lower unsaturated fatty-acid ethyl esters by DHA-Et proceeded along the membrane thickness. The purity of DHA-Et was improved to 99 wt % by permeating first bonito oil ethyl ester containing 95 wt % DHA-Et and then acetonitrile through the module.

Docosahexaenoic acid ethyl esters from Isochrysis galbana

In order to produce docosahexaenoic acid (DHA), a culture of the microalgal strain Isochrysis galbana was implemented. In Erlenmeyer flasks, a natural seawater medium, the Provasoli 1/3 medium, was compared to the classical Jones medium for DHA production. The Provasoli 1/3 medium stimulated growth (0.44 d −1), but influenced DHA accumulation negatively (0.240 pg cell −1). However, DHA production per liter of culture medium were of the same order of magnitude with both media (0.961 mg l −1). In a 2-l bioreactor, DHA production per liter of culture medium did not increase significantly between 4 and 8 days of culture. With a view to optimize DHA productivity, cells should be harvested at the end of exponential phase i.e. after 4 days of culture. Two strategies were then attempted to produce DHA ethyl esters. First, lipids from I. galbana were submitted to lipase-catalyzed transesterification with ethanol. Secondly, fatty acids from I. galbana were submitted to lipase catalyzed esterification with ethanol. In both cases, lipase from Candida antarctica was shown to be the best candidate, among the five tested, with conversion yields of 20 and 60% after 24 h of transesterification and esterification respectively.

Positional distribution of highly unsaturated fatty acids in triacyl-sn-glycerols of Artemia nauplii enriched with docosahexaenoic acid ethyl ester.

This paper presents the positional distribution of fatty acids in triacyl-sn-glycerols (TAG) of Artemia nauplii used in aquaculture as a live food for marine fish larvae. The nauplii were enriched with docosahexaenoic acid (DHA) ethyl ester (EE) in the form of gelatin-acacia microcapsules for 4, 18, and 24 h. TAG of the initial, enriched, and unenriched Artemia nauplii were subjected to stereospecific analysis. A remarkable increase of DHA content in the enriched Artemia TAG confirmed the view that DHA-EE is effectively assimilated and incorporated into the TAG fraction of Artemia nauplii. TAG of the nauplii enriched with 25 mg/L of DHA-EE contained DHA at concentrations of 5.9-6.8, 4.3-6.0, and 14.3-22.3 mol% in the sn-1, sn-2, and sn-3 positions, respectively. When the nauplii were enriched with 100 mg/L of DHA-EE, proportions of DHA in the sn-1, sn-2, and sn-3 positions were 5.2-8.6, 3.9-6.0, and 12.2-25.4 mol%, respectively. In all of the enriched Artemia, DHA was preferentially located in the sn-3 position followed in sequence by the sn-1 and sn-2 positions. The lower content of DHA in the sn-1 and sn-2 positions was consistent with low content of this acid in 1,2-diacyl-sn-glycerophospholipids. When fish larvae are reared on Artemia nauplii enriched with EE-type DHA oil, the larvae feed on DHA esterified in TAG with a positional distribution pattern similar to that of marine mammals (sn-3 >> sn-1 > sn-2) rather than that of fish or marine invertebrates (sn-2 >> sn-3 > sn-1).