Furanoid fatty acids from fish lipids

Fatty acids, recently reported as constitutents of certain fish lipids, were identified to be derivatives of furan (furanoid fish fatty acids). 12,15-Epoxy-13,14-dimethyleicosa-12,14-dienoic acid is predominant among the furan acids and is associated withbis-homologs in regard to chain length. Monomethyl acids, such as 12,15-epoxy-13-methyleicosa-12,14-dienoic, are present in appreciable amounts. The structures were concluded from oxidative degradations, from mass spectrometry of methyl esters of the novel acids and fatty acids derived from them by opening the ring, and from nuclear magnetic resonance, infrared, and Raman spectra. The results from chemical procedures and from spectrometric methods were in aggreement with those obtained with authentic methyl 9,12-epoxyoctadeca-9,11-dienoate. The number of substituents at the furan ring greatly influences hydrogenation, hydrogenolysis, and hydrolysis reactions of the ring. Scientific Journal Series 9154, Agricultural Experiment Station, University of Minnesota, St. Paul, MN 55101; Hormel Institute Publication No. 749.     

Comparison between extraction of lipids and fatty acids from microalgal biomass

Seven solvent mixtures have been used to extract the lipid fraction of lyophilized biomass ofIsochrysis galbana. Six of them were composed of biocompatible solvents. Each method was carried out under relaxed operating conditions (i.e., one hour at room temperature) with extraction in a nitrogen atmosphere to prevent autooxidation and degradation of polyunsaturated fatty acids (PUFAs). Apart from the well-established Bligh and Dyer method [Can. J. Biochem. Physiol. 37:911 (1959)] (Cl₃CH/MeOH/H₂O, 1∶2∶0.8, vol/vol/vol), which rendered the highest yield of lipids (93.8%), ethanol (96%) and hexane/ethanol (96%), 1∶2.5 vol/vol produced the best results (84.4 and 79.6%, respectively). To obtain free fatty acids, KOH was added to the solvent mixtures used to extract the total lipids, except for Cl₃CH/MeOH/H₂O, and direct saponification was carried out at 60°C for 1 h or at room temperature for 8 h. The highest yields obtained by direct saponicification were 81% with hexane/ethanol (96%), 1∶2.5, vol/vol and 79.8% with ethanol (96%). Partial yields of the mainn-3 PUFAs found inI. galbana, stearidonic acid (SA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were calculated for both extraction methods. For lipid extraction with ethanol (96%), yields of 91, 82 and 83% were obtained for SA, EPA and DHA, respectively. When direct saponification was used, hexane/ethanol (96%; 1∶2.5, vol/vol) produced the best yields of (91, 79 and 69% for SA, EPA and DHA, respectively).     

Characterization of fatty acids from root and shoot lipids ofCapsicum species

Lipids were extracted from the roots and shoots of four species of theCapsicum (pepper) genus and separated into three fractions: triglycerides; free fatty acids, mono- and diglycerides; and phospholipids. The component fatty acids were determined by subjecting the methyl esters to gasliquid chromatography. The predominate fatty acids obtained were palmitic (16∶0) and linoleic (18∶2), with lesser amounts of linolenic (18∶3), stearic (18∶1), and oleic (18∶0). Differences existed in the neutral lipid fractions which might be of value from taxonomic interests; however, the phospholipids from each of the species and plant parts did not differ so greatly. A comparison of the amount of unsaturated fatty acids in the phospholipid fractions indicates that differences exist which might be of value in determining the relative sensitivity of the several species to chilling temperatures.     

Variation of cyclopropenoid fatty acids in cottonseed lipids

The proportions of the cyclopropenoid fatty acids (CPA) esters, malvalate and sterculate, varied little in lipids from individual cottonseeds. Coefficients of variation were 10% and 20% for seeds from a lock and 13 varieities, respectively. Within the seed, variations in CPA concentrations were very large. Cyclopropenoid fatty acid concentration in the lipids decreased from 28% in the root tip to 2% in the top of the axis, and to 0.02% in the portion of the cotyledons nearest to the hull. The axial portion was only ca. 5% of the kernel, yet it contained 75% of the CPA. Distribution of dihydrosterculic acid, the precursor of CPA, was similar to that of CPA. High concentrations of CPA were found in immature seeds, root tip and radicle of germinated seeds, and root tips of cotton plants. Presented at the 73rd annual AOCS meeting, Toronto, Ontario, May 1982. One of the facilities of the Southern Region, Agricultural Research Service, U.S. Department of Agriculture. Names of companies or commercial products are given solely for the purpose of providing specific information; their mention does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Rapid analysis of fatty acids in plasma lipids

A rapid and convenient procedure for the quantitative determination of the fatty acid composition of plasma lipids is described. Human plasma was applied directly to the preadsorbent zones of thin-layer silica gel plates with added antioxidant, internal standards and carriers. The thin-layer chromatography (TLC) plates were partially developed with methanol followed by chloroform/methanol (1∶1, v/v), and then they were fully developed in hexane/diethyl ether/acetic acid (80∶20∶1, v/v/v) to separate the major classes of lipids. Silica gel from regions containing the separated lipids was scraped into screw-capped tubes and treated with boron trifluoride-methanol prior to gas chromatography. The method of direct application to TLC plates gave yields and compositions of fatty acids very similar to the method of applying extracted plasma lipids. This relatively simple method is suitable for analyzing the fatty acids in plasma lipids from a 50 microliter finger-tip blood samples from an individual, and it may be useful in wide-scale screening of different individuals to estimate the relative amounts of ingested polyunsaturated fatty acids. Pfizer Biomedical Research Awardee.     

Structured lipids from high-laurate canola oil and long-chain omega-3 fatty acids

The lipase-assisted acidolysis of high-laurate canola oil (HLCO; Laurical 25) with long-chain n−3 FA (DHA and EPA) was studied. Response surface methodology was used to obtain a maximal incorporation of DHA or EPA into HLCO. The studied process variables were the amount of enzyme (2–6%), reaction temperature (35–55°C), and incubation time (12–36 h). The amount of water added and the mole ratio of substrates (oil to DHA or EPA) were kept at 2% and 1∶3, respectively. All experiments were conducted according to a face-centered cube design. Under optimal conditions (4.79% of enzyme; 46.1°C; 30.1 h), the incorporation of DHA into HLCO was 37.3%. The corresponding maximal incorporation of EPA (61.6%) into Laurical 25 was obtained using 4.6% enzyme, a reaction temperature of 39.9°C, and a reaction period of 26.2 h. Examination of the positional distribution of FA on the glycerol backbone of modified HLCO with DHA showed that the DHA was primarily located in the sn-1,3 positions of the TAG molecules. However, lauric acid also remained mainly in the sn-1,3 positions of the modified oil. For EPA-modified Laurical 25, lauric acid was present mainly in the sn-1,3 positions, whereas EPA was randomly distributed over the three positions.     

Rat testicular lipids and dietary isomeric fatty acids in essential fatty acid deficiency

Weanling rats were fed essential fatty acid-deficient diets, either completely fat-free, or with partially hydrogenated fish oil (PHFO, 28 wt %), or with fractions derived from PHFO containing primarily positional isomers oftrans-eicosenoate (20∶1, 3 wt %) ortrans-docosenoate (22∶1, 3 wt %). Control animals were fed a peanut oil-containing diet (28 wt %). After 5 or 15 weeks on the diet, the content of neutral and phosphorus-containing lipids in the testes was determined. The fatty acid distribution in major lipid classes was analyzed for animals fed the diets for 15 weeks. The testicular stage of maturation or degeneration was assessed by histology. The group fed PHFO exhibited signs of complete testicular degeneration, or lack of maturation, already after 5 weeks, whereas the animals on the diets with the very long chain monoenoic acids suffered severe degenerations only after 15 weeks. In the PHFO-fed rats, a sharp decline in the concentration of testicular triacylglycerols was observed. In all of the essential fatty acid-deficient groups, an increase in testicular sphingomyelin was observed. Cholesterol levels were fairly similar among all dietary groups. The total testicular fatty acids of the PHFO-fed animals contained somewhat more eicosadienoic acid than found in the other groups, and somewhat less (n−9)-acids. In all EFA-deficient groups, (n−6)-acids were lowered, in particular in triacylglycerols and phosphatidyl cholines. The PHFO group did not show a lower (n−6)-concentration than the other deficient groups, in spite of the more severe symptoms of deficiency. There was no evidence of a major accumulation of long chain isomeric fatty acids in the degenerated testes of the PHFO-, 20∶1, and 22∶1-fed groups.     

Circum-annual changes in triglyceride fatty acids of bat brown adipose tissue

A circum-annual study of the fatty acids of brown adipose tissue triglycerides ofEptesicus fuscus has demonstrated a rhythmic pattern of change. This is seen as a reciprocal shift of the levels of oleic and linoleic acids. Oleic acid levels are lower during the summer months and higher in the winter months. Levels of palmitic and linoleic acids reach maximal values in midsummer and fall significantly during the winter. Homogenates of brown adipose tissue produce more¹⁴CO₂ from 1-¹⁴C-palmitic acid than from 1-¹⁴C-oleic acid when incubated at temperatures below 20C. The formation of¹⁴CO₂ from either substrate was maximal in the neighborhood of 30C, and the temperature effect was enhanced by stimulation with DL-carnitine. It is proposed that the rhythmic change in brown adipose tissue triglyceride composition is a reflection of the different rates of fatty acid oxidation and the absence of normal food intake for extended periods of time.     

Polyunsaturated fatty acids of serum lipids in myocardial infarction

Two groups of volunteers had blood drawn for serum analysis of fatty acids. The first group was comprised of patients admitted to the hospital with possible myocardial infarction (MI). Blood was drawn at admission and at 12, 24 and 48 hr. These patients were subsequently divided into three groups, those with MI, those without (No MI) and those taking prostaglandin inhibitors (PGI), on the basis of the cardiac enzymes, electrocardiograms and clinical history. A fourth group of Normal nonstressed people was also drawn at 0, 12, 24 and 48 hr for comparison. Fatty acid composition of phospholipids (PL), nonesterified fatty acids (NEFA), triglycerides (TG) and cholesteryl esters (CE) was determined by capillary gas chromatography (GC), and comparison were made between the MI, No MI, PGI and Normal groups. Total NEFA were significantly elevated in patients admitted for possible MI compared with Normals. Those patients with MI had marginally higher levels of NEFA than the No MI group at each sampling time, but this difference was not statistically significant. The MI, No MI and PGI groups had significantly different fatty acid patterns in NEFA with reduced percentages of arachidonic acid (AA) than controls. The fatty acid patterns in the four lipid classes showed few significant differences comparing the MI, No MI and PGI groups. The regular use of prostaglandin inhibitors before hospitalization for chest pain was associated with a reduced frequency of MI (p<0.002). NEFA levels, nonesterified AA levels and fatty acid patterns in this group did not differ from those patients not taking prostaglandin inhibitors. Part of this work was presented at the 78th American Oil Chemists’ Society Annual Meeting, May 17–21, 1987.     

Occurrence of unusual hexadecenoate fatty acids in hepatoma lipids

Cis-hexadecenoates isolated from rat liver and hepatoma 7288CTC lipids were analyzed for positional isomers by ozonolysis and capillary gas liquid chromatography. In addition to the Δ6, Δ7, Δ9 and Δ11 isomers found in both tissues, the hepatoma neutral and polar lipids contained relatively high percentages of Δ12 and Δ14 hexadecenoates that were virtually absent from liver. The occurrence of these unusual fatty acids may result from an error in lipid metabolism in the hepatoma.     

Effects of clofibrate on lipids and fatty acids of mouse liver

Clofibrate administration significantly altered the amount and fatty acid composition of lipids in mouse liver. The net content of phospholipids (PL) increased and that of triacylglycerols (TG) decreased concomitantly with liver enlargement in mice treated for two weeks with this drug (0.5% w/w in the food). The highest increase among PL was in phosphatidylcholine; other components either showed lower increases or, as in the case of sphingomyelin and the plasmalogens, decreased. In all lipid classes the treatment resulted in altered ratios between major saturates, between saturates and monoenes, and between major polyenes. Among these, 20∶3n–6 and 22∶5n–3 increased several-fold, and the 20∶3n–6/20∶4n–6 and 22∶5n–3/22∶6n–3 ratios increased due to a more active formation of the precursors than of the corresponding products. This change affected all glycerolipid classes. Liver sphingomyelin showed a relative enrichment in monoenoic fatty acids like 22∶1 and 24∶1, caused by a net decrease in the amount of saturates, particularly 22∶0 and 24∶0. The stimulated membrane proliferation imposed by clofibrate must increase phospholipid synthesis and, hence, the need for fatty acids. The results suggest that these demands are met mostly by TG acyl groups, either directly or after oxidation/desaturation processes. This was apparently the case for the polyenoic fatty acids of the n-6 and n-3 series. The longer chain (C₂₂ and C₂₄) components decreased, suggesting that their oxidation was stimulated to provide part of the required (C₂₀ and C₂₂) polyenes.     

Anatomical variation in fatty acid composition and triglyceride distribution in animal depot fats

The fatty acid composition and glyceride distribution of fatty acids in pork, beef and lamb depot fats from different localities within the same animal were determined by a combination of gas liquid chromatography and lipase hydrolysis techniques. The glyceride distribution was calculated according to the method of Vander Wal, based on the 1, 3-random and 2-random distribution pattern. Both fatty acid composition and glyceride structure were found to vary depending on the position within the animal from which the depot fat was obtained. Presented at the AOCS meeting in Chicago, October, 1964.     

Studies on the fatty acid composition of crayfish lipids

The fatty acid composition of carcass and exoskeleton lipids was determined for the freshwater crayfishOrconectes rusticus. Lipid fractions were isolated by column and thin-layer chromatography. Fatty acid methyl esters and alcohol acetates were then prepared and analyzed by gas-liquid chromatography. Peak identities were established from retention time data for methyl esters, hydrogenated methyl esters, and saturated, monoene, diene, and polyene methyl esters separated as acetoxy-mercuri-methoxy derivatives. Minor component acids were estimated from their relative compositions in these fractions. Presented at the symposium honoring J. B. Brown, AOCS meeting in Chicago, 1964.     

Antimicrobial lipids: Natural and synthetic fatty acids and monoglycerides

Over 40 natural or synthetic lipophilic compounds were screened for antimicrobial activity. Gram (+) bacteria and yeasts but not Gram (−) bacteria were affected by these agents. Epimino and selena fatty acids are more active than their corresponding straight chain unsubstituted fatty acids. The position of selenium influenced the antimicrobial activity of the fatty acid. The presence and position of a double or triple bond, usually an important factor in long chain fatty acids (>C₁₄) had little or no effect in C₁₁ fatty acids. Optimum antimicrobial activity was found for fatty acids and their corresponding monoglycerides when the chain length was C₁₂. The dilaurin derivative was not active.     

Effect of oxygen levels on the fatty acids and lipids ofMucor rouxii

The effect of aerobic and oxygen limiting (anaerobic) growth conditions upon the fatty acid and lipid composition ofMucor rouxii has been examined. The aerobic cells contained a range of fatty acids typical of phycomycetes, i.e. γ-linolenic acid, with an unsaturation index of 1.20, whereas the anerobic cells contained relatively high levels of shorter chained fatty acids and very low concentrations of unsaturated acids (unsaturation index=0.025). The unsaturated compounds were monoolefinic tetra-, hexa-, and octadecenoic acids; and closer examination of their di-trimethylsilyl derivatives by gas chromatography and mass spectrometry showed that all three acids contained the double bond in the Δ⁹ position. These results were consistent with a microaerobic biosynthetic pathway. In addition, there were major quantitative differences in the lipid composition of the two types of cells; and it was evident that the differences in growth environment markedly affected the cellular lipid and fatty acid compositions.     

Positional isomers of unsaturated fatty acids in rat liver lipids

The fatty acids of liver lipids from rats raised on a fat free diet from the 30th to the 90th day after birth were analyzed with special regard to the detection of positional isomers of mono-, di-, tri-, and tetraenoic fatty acids. The methyl esters obtained after transesterification of total lipids were separated by argentation chromatography into five fractions: I saturated, II monoenoic, III dienoic, IV dienoic nonmethylene interrupted, V triand tetraenoic fatty acid esters. After hydroxylation of the double bonds with osmium tetroxide, the analysis of the poly-O-trimethylsilyl derivatives by gas liquid chromatography on S.C.O.T. columns combined with mass spectrometry revealed the presence of 19 monoenoic, 15 dienoic, and 9 trienoic as well as 3 tetraenoic fatty acid isomers including the normally occurring representatives of the (n−3), (n−6), (n−7), and (n−9) fatty acid families. The majority of the identified isomers can be coordinated to one of these families like 7–16∶1; 11–20∶1; 6,9–18∶2; 8,11–20∶2; 5,11–20∶2; 5,8,11–20∶3; 7,10,13–22∶3 to the (n−9) family, 11–18∶1; 13–20∶1; 5,11–18∶2; 7,13–20∶2; 6,11–18∶2; 6,9–16∶2; 8, 11–18∶2; 10,13–20∶2; 5,8,11–18∶3; 7,10,13–20∶3; 4,7,10,13–20∶4 to the (n−7) family and 11,14–20∶2; 5,11,14–20∶3; 6,9,12–18∶3; 8,11,14–20∶3; 5,8,11,14–20∶4; 7,10,13,16–22∶4 to the (n−6) family. All these naturally occuring isomers can be placed into a network of desaturation and chain elongation steps which allows certain conclusions about the substrate specificity of the Δ6-, Δ5-and Δ4-desaturase systems. The great number of isomers found in the (n−7) family indicates that the members of this family are actively metabolized in partial essential fatty acid deficiency.     

Long-chain polyunsaturated fatty acids in plasma lipids of obese children

Fatty acid composition of plasma phospholipids (PL), triglycerides (TG), and sterol esters (STE) was determined by high-resolution capillary gas-liquid chromatography in 22 obese children (age: 13.7±1.4 y, body weight relative to normal weight for height: 170±24%, mean ±SD) and compared with data obtained in 25 age-matched healthy controls. There were no differences in the levels of linoleic acid (LA, C_18∶2n-6) in any of the plasma fractions from the obese children and the controls. Obese children exhibited significantly higher values of arachidonic acid (AA, C_20∶4n-6) than controls both in PL (12.6 [2.4] vs. 8.3 [1.4], % wt/wt, [median (interquartile range)],P<0.001) and STE (7.3 [1.8] vs. 6.0 [1.1],P<0.05). Similarly, obese children showed higher values than controls for dihomo-γ-linolenic acid (DHGLA, C_20∶3n-6) in PL (4.0 [0.5] vs. 3.0 [0.6],P<0.001), TG (0.4 [0.1] vs. 0.2 [0.1],P<0.001), and STE (0.9 [0.1] vs. 0.7 [0.1],P<0.01), and for γ-linolenic acid (C_18∶3n-6) in STE (1.1 [0.2] vs. 0.8 [0.2],P<0.001). The AA/LA ratios were higher in obese children than in controls in PL (0.68 [0.16] vs. 0.42 [0.09],P<0.0005) and STE (0.16 [0.04] vs. 0.12 [0.02],P<0.05), whereas the AA/DHGLA ratios were lower in TG of obese children than in controls (3.40 [0.64] vs. 5.10 [1.75],P<0.005). Plasma glucose concentrations were inversely related to AA in TG (r=0.53,P<0.05), and plasma TG concentrations were inversely related to AA in PL and STE (r=−0.49,P<0.05 andr=−0.48,P<0.05) and to the AA/DHGLA ratios in PL (r=−0.57,P<0.01),TG (r=−0.56,P<0.01) and STE (r=−0.56,P<0.01). We conclude that the significantly higher values of n-6 long-chain polyunsaturated fatty acids (LCP) in plasma lipids of obese children than in age-matched controls may be caused by an enhanced activity of Δ6-desaturation, and we speculate that elevated fasting immunoreactive insulin seen in obese children (19.4±8.0 μU/mL) may stimulate synthesis of n-6 LCP fatty acids.     

Use of aqueous HCI/MeOH as esterification reagent for analysis of fatty acids derived from soybean lipids

A quick, reliable and very inexpensive method is described for the analysis of fatty acids derived from soybean lipids. The method involves extraction of soybean lipids with petroleum ether, followed by hydrolysis of lipids with KOH/MeOH (0.5 M) for 5 min at 100 C followed by esterification with aq. HC1 (36%)/MeOH (4:1, v/v) for 15 min at 100 C. No problems were encountered with the esterifica-tion procedure in the presence of water and the procedure gave results comparable to die more conventional BF₃/MeOH reagent. The aq. HCI/MeOH reagent is several hundred times cheaper than BF₃/MeOH, and does not compromise the efficiency of the reagent.     

The variation of triglyceride structure with fatty acid composition in pig adipose tissue

Forty-five triglyceride samples with a wide range of fatty acid compositions were selected from a large number of pig adipose tissue samples (inner and outer back fats and perenephric fat) available from nutritional experiments. These samples were subjected to stereospecific analysis to determine the changes occurring in the positional distribution of the component fatty acids. The oleic acid content of the triglycerides was taken as the standard of comparison and as this increased, the proportions of the other unsaturated fatty acids also increased in a linear manner and the concentrations of the saturated components decreased proportionately. In position 1, the palmitic acid concentration remained constant while the stearic acid concentration decreased linearly and the concentrations of the unsaturated fatty acids increased. In position 2 the stearic acid concentration remained almost constant while the palmitic acid concentration decreased linearly in response to increases in the concentrations of the unsaturated acids. The least change occurred in position 3 where there were slight decreases in the concentrations of saturated acids as the concentrations of unsaturated acids increased. The precise quantitative relationships depended on the tissue examined. Constant proportions of the available myristic and palmitoleic acids were found in all three positions and constant proportions of the available stearic and oleic acids were found in position 1. These results are discussed in relation to possible pathways of triglyceride biosynthesis in pig adipose tissues.     

Monoenoic fatty acids in human brain lipids: Isomer identification and distribution

The carbon chain length distribution and the double bond positional isomer composition of the monoenoic fatty acids of the lipids of total human brain tissue have been determined using gas chromatography and gas chromatography/mass spectrometry of the fatty acid methyl and picolinyl esters. The even chain length monoenoic C₁₆ to C₂₈ fatty acids contain predominantly two positional isomer series, the n−7 and n−9cis homologues, whose relative proportion varies significantly with chain length. The odd chain length long-chain fatty acids consist of n−8 and n−10 isomers, whereas the odd chain length very long-chain (more than 22 carbon) fatty acids are n−7 and n−9 isomers.