Separation and quantitation of phospholipids in animal tissues by latroscan TLC/FID

A procedure has been developed to separate and quantitate phospholipids, including phosphatidylinositol and phosphatidylserine, from animal tissues by means of the Iatroscan TLC/FID technique. The method is based on the use of 0.01 M oxalic acid impregnated Chromarods-SII and stepwise resolution of the phospholipids in the presence of 1,2-dipalmitoyl-sn-glycero-3-phospho (N,N-dimethylethanolamine) as internal standard. To remove the neutral lipids, the rods are initially developed in a nonpolar solvent mixture followed by partial scanning. Next, the rods are impregnated with oxalic acid, developed twice in CHCl₃/CH₃OH/CH₃COOH/HCOOH/H₂O (80∶35∶2∶1∶3, v/v/v/v/v) and partially scanned for measuring lysophosphatidylcholine, sphingomyelin and phosphatidylcholine. The subsequent step involves double development in CHCl₃/CH₃OH/30% NH₄OH (60∶35∶0.9, v/v/v) to resolve cardiolipin, internal standard, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and phosphatidic acid. For each phospholipid a linear calibration curve with a highly significant correlation coefficient was obtained. However, the calibration lines extrapolated to negative intercepts on the ordinate, indicating declining sensitivity at low phospholipid loads.     

Improved separation of phospholipids by counter-current distribution

Separation by counter-current distribution of individual molecular species of phospholipids are much improved by the use of CCl₄:CH₃OH:H₂O (62∶33∶5 v/v) for lecithins and of heptane: CH₃OH:H₂O (50∶47.5∶2.5 v/v) for the methyl esters of the dinitrophenyl derivatives of phosphatidylethanolamines.     

Quantitative analyses of methyl esters of fatty acid geometrical isomers,and of triglycerides differing in unsaturation,by the Iatroscan TLC/FID technique using AgNO3 impregnated rods

The relative FID responses for Iatroscan analyses ofcis andtrans isomers of methyl esters of 18∶1†6, 18∶1†9 and 18∶1†11 on Chromarods-S impregnated with AgNO₃ were studied at load levels ranging from 0.5 to 20 μg, using methyl stearate as internal standard. The FID response correction factors were greater for thecis than for thetrans isomers. The correction factors were relatively constant in the 10–20 μg interval, but increased in the range 0.5–5 μg. Separation of tristearin, triolein, trilinolein and trilinolenin also was obtained on Chromarods-S impregnated with AgNO₃ using a mixture of benzene: chloroform: acetic acid (90∶8∶2) as the solvent system. The relative FID responses for the triolein, trilinolein and trilinolenin were determined at load levels ranging from 0.5 to 14.3 μg using tristearin as an internal standard. The FID response correction factors of these three triglycerides differed significantly for load levels of 1.0, 2.5 and 5.0 μg. However, the factors could be considered as being equal in the range 10 to 14.3 μg. Correction factors were not affected by repeated re-use of the same set of Chromarods. Several hundred separations and scans appeared feasible.     

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).     

Inevitable generation of primary alcohols during reduction of oxidized lipids with sodium borohydride

This report deals with the fluorometric determination of fatty alcohols generated by the reduction of the ester linkage of lipids with NaBH₄, and with the limitations of the reduction method for assaying oxidized lipids. Optimum conditions for the fluorometric analysis of primary and secondary alcohols using 1-anthroyl nitrile were obtained. After reduction with NaBH₄ in MeOH or in MeOH/benzene (8∶2, v/v), the formation of 1-hexadecanol from a variety of palmitic acid esters was measured fluorometrically by reverse-phase high-performance liquid chromatography (HPLC): From glycerides and methyl palmitate, 1–3% (w/w) 1-hexadecanol was produced and a trace was produced from cholesteryl palmitate (10 min, 21°C). 1-Hexadecanol was never generated from palmitic acid. Although considerable improvement occurred with the choice of the solvent for the NaBH₄ reduction, the generation of primary alcohols from ester lipids usually seems inevitable.     

Chemical characterization and physicochemical behavior of biosurfactants

Microbes have been isolated from soil and water samples after an enrichment culture process with kerosene and tested for biosurfactant production by measuring the surface and interfacial tensions and emulsification power of culture broths. The isolation and characterization of extracellular surface-active agents from the culture broth of Pseudomonas aeruginosa 44T1 strain have been made. Preliminary structure identification with specific TLC reagents of the CHCl₃MeOH (2:1) extracts showed two spots with a glycolipidic structure and Rf values of 0.70 and 0.45, respectively, using the solvent system CHCl₃:MeOH:H₂O (65:25:4). Separation of surface active agents by Chromatographic absorption column in Florisil or silica gel and further spectroscopic study (IR, 1H-NMR, 13C-NMR) and chemical degradation techniques (acid and alkaline hydrolysis) gave a structure of β[β(2-0-α-L-rhamnopyranosyloxy)decanoyl] decanoic acid and β[β (2-0-α-L-rhamnopyranosyl-α-L-rhamnopyranosyloxy) decanoyloxy] decanoic acid (glycolipid A and glycolipid B, respectively) for the two glycolipids detected. A new method of mass spectrometry, fast atom bombardment mass spectrometry (FABMS), was used to probe molecular structure. The mass spectra obtained contain molecular weight recognition and sequence information signals, and they are in agreement with the proposed structures. Physicochemical evaluations of the two isolated glycolipids were made. The minimum surface tension obtained was 25 mN/m in water solutions. At pH 7 the CMC value was 11 ppm. In both cases, at pH 3 the CMC was displaced to lower and at pH 9 it was displaced to higher concentration values. Glycolipid B showed a lower value of interfacial tension (0.2 mN/m) than glycolipid A (1.0 mN/m). Glycolipid A showed a lower CMC value at alkaline pH, whereas glycolipid B had a lower CMC at acidic pH than at alkaline pH.     

Analysis of soybean lecithins and beef phospholipids by HPLC with an evaporative light scattering detector

Linear (r > 0.99) calibration curves were obtained for 10–150 μg of phosphatidylethanolamine (PE), 10–75 μg of phosphaditylinositol (PI), phosphaditylserine (PS) and lysophosphatidylethanolamine, 10–100 μg of phosphatidic acid (PA) and 10–250 μg of phosphatidylcholine (PC) by high-performance liquid chromatography analyses with an evaporative light scattering detector, a Zorbax 7-μm silica column and gradient elution with two solvents. One solvent (A) contained 415 mL isooctane (IOCT), 5 mL tetrahydrofuran (THF), 446 mL isopropanol (IPA), 104 mL CHCl₃ and 30 mL H₂O; and the other solvent (B) contained 216 mL IOCT, 4 mL THF, 546 mL IPA, 154 mL CHCl₃ and 80 mL H₂O. The gradient in which 100% A linearly changed to 100% B in 20 min followed by 12 min of 100% B and then a linear change to 100% A during 5 min separated PE, PS and PC in soybean lecithins and beef lipids, but failed to resolve PI and PA. In these same samples, less polar lipids were separated from phospholipids (PL) by elution from Bond-Elut silica columns with diethyl ether/hexane (20:80, vol/vol), and PL were recovered by elution with methanol. This procedure is useful for concentration of minor lipid components. Levels of PE, PI-PA, PS and PC were higher in granular than in liquid lecithin, and PC was the most abundant PL in soybean lecithins and beef lipids.     

Morphology and photophysical properties of luminescent electrospun fibers prepared from diblock and triblock polyfluorene-<Emphasis Type="Italic">block</Emphasis>-Poly(2-vinylpyridine)/PEO blends

We successfully prepared luminescent electrospun (ES) fibers from the polymer blends of diblock poly[2,7-(9,9-dihexylfluorene)]-block-poly(2-vinylpyridine)(di-PFPVP) or triblock P2VP-b-PF-b-P2VP (tri-PFPVP) with polyethylene oxide (PEO) using a single-capillary spinneret. The morphology and photophysical properties of ES fibers were explored via the molecular architecture, solvent selectivity, and different molecular weights of PEO. The ES fibers had diameters around 400–800 nm using solvent of methanol (MeOH)/H₂O while those using CHCl₃ were around 1–3 μm, which was probably due to the difference on the solvent dielectric constant. Furthermore, the PF aggregated size and emission peak maximum in the ES fibers increased with enhancing the block copolymer composition using CHCl₃. However, an insignificant variation was observed using MeOH/H₂O. The larger PF aggregated size of the di-PFPVP/PEO blend ES fibers resulted in the red-shifting and broader emission peak, in comparison with that of the tri-PFPVP/PEO blend ES fibers. The efficient interaction of the PEO with the PVP block in two different block copolymers accounted for the above results. In the ES fibers using the low molecular weight of PEO (Mn~100 K), it exhibited a red-shifting on the PL spectra in comparison with the spin-coated films due to the geometrical confinement. Nevertheless, such confinement was probably significantly reduced using the high molecular weight PEO (Mn~2000 K) and thus an insignificant variation was found on the PL spectra. The present study demonstrated that their aggregate morphology and photophysical properties of ES fibers prepared from conjugated rod-coil block copolymer blends could be significantly tuned through polymer architecture, solvent selectivity, and copolymer composition.     

Determination of lycopene, α- and β-carotene and retinyl esters in human serum by reversed-phase high performance liquid chromatography

A rapid specific, microdetermination of the major human blood carotenoids by high performance liquid chromatography (HPLC) separation and quantitation at 466 nm is detailed in this paper. Serum retinyl esters can also be quantified utilizing the same separation procedure but detected at 325 nm. One hundred microliters of deproteinated serum were extracted with chloroform and injected on a reverse-phase column. Separation occurred within 16 min for all compounds of interest employing a mobile solvent of MeOH/AcN/CHCl₃ (47∶47∶6). All compounds were quantified at the wavelengths cited by integrated peak areas using retinyl acetate as a daily standard. Analysis of serum from a hypercarotenemic anorexia nervosa patient and a person suffering from hypervitaminosis A are presented as examples of the clinical application of this procedure.     

Extracting long-chain fatty acids from a fermentation medium

Several solvents were evaluated for extracting free long-chain FA (LCFA) from a fermentation medium. Chloroform, chloroform/methanol (1∶1), hexane, and hexane/methyl tert-butyl ether (MTBE) (1∶1) were evaluated as alternative extraction solvents. Parameters considered for optimizing LCFA recoveries included pH and ionic strength. Maximal LCFA recoveries were obtained by adding 2 mL of the hexane/MTBE (1∶1) solvent mixture, 80 μL of 50% H₂SO₄, and 0.05 g NaCl to 1 mL of the aqueous sample and mixing for 15 min at 200 rpm. This method quantified saturated LCFA [capric acid (C_10∶0) to stearic acid (C_18∶0)] and unsaturated LCFA with 18 carbons [linoleic acid (C_18∶2) and oleic acid (C_18∶1)] with a 98 to 100% recovery. Caproic (C_6∶0) and caprylic (C_8∶0) acids were characterized by 27 and 76% recoveries, respectively.     

Quantitating heart lipids: Comparison of results obtained using the Iatroscan method with those from phosphorus and gas chromatographic techniques

The precision and accuracy of the Iatroscan method was evaluated by comparing the results obtained with established phosphorus and gas chromatographic techniques. A complete lipid class analysis of rat heart lipids was chosen in order to evaluate the performance of the Iatroscan method for biological samples which contained both neutral lipids and phospholipids. A partial scan and repeat development with chloroform/methanol/water (68.5∶29∶2.5) was introduced to achieve consistently good separations of the phospholipids on the Chromarods in the Iatroscan method. The results showed that the precision of the Iatroscan method for some lipid classes was comparable to that of phosphorus or gas chromatographic techniques, while for other lipid classes it was lower. Compared to the data obtained using the phosphorus method, the Iatroscan data were generally similar, while the gas chromatographic method generally gave lower values. These findings, together with the advantages of time required for analysis, size of sample, and universality of detection, suggest that the Iatroscan is a valuable complementary method for complex lipid analyses.     

Paper chromatography of 2,4-dinitrophenylhydrazones of saturated aliphatic aldehydes

Summary A rapid method of separating the 2,4-dinitrophenylhydrazones of C₁ to C₉ aldehydes by descending chromatographic system has been described. Whatman No. 1 filter paper was impregnated with ethylene glycol-methanol (1∶4, v/v), and n-heptane saturated with methanol was used as a developing solvent. Complete separation was achieved in 3 hrs. It has been shown that the method can also be used for the separation of 2,4-dinitrophenylhydrazone derivatives of ketones. Funds for support of these studies were made available by the American Dairy Association and Grant A-1671 National Institutes of Health.     

Effect of diets rich in linoleic or α-linolenic acid on phospholipid fatty acid composition and eicosanoid production in atlantic salmon (Salmo salar)

Atlantic salmon post-smolts were fed diets rich in linoleic acid (sunflower oil, SO), α-linolenic acid (linseed oil, LO) or long-chain polyunsaturated fatty acids (fish oil, FO) for a period of 12 wk. In the liver phospholipids of fish fed SO, the levels of 18∶2n−6, 20∶2n−6, 20∶3n−6 and 20∶4n−6 were significantly elevated compared to both other treatment. In choline phospholipids (CPL), ethanolamine phospholipids (EPL) and phosphatidylserine (PS) the levels of 22∶4n−6 and 22∶5n−6 were significantly elevated in fish fed SO. In liver phospholipids from fish fed LO, 18∶2n−6, 20∶2n−6 and 20∶3n−6 were significantly elevated but 20∶4n−6, 22∶4n−6 and 22∶5n−6 were similar or significantly decreased compared to fish fed FO. Liver phospholipids from fish fed LO had increased 18∶3n−3 and 20∶4n−3 compared to both other treatments while EPL and phosphatidylinositol (PI) also had increased 20∶5n−3. In fish fed LO, 22∶6n−3 was significantly reduced in CPL, PS and PI compared to fish fed FO. Broadly similar changes occurred in gill phospholipids. Production of 12-lipoxygenase metabolites in isolated gill cells stimulated with the Ca²⁺-ionophore A23187 were significantly reduced in fish fed either SO or LO compared to those fed FO. However, the ratio 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE)/12-hydroxy-5,8,10,14,17-eicosapentaenoic acid (12-HEPE) was significantly elevated in stimulated gill cells from SO-fed fish. Although mean values of thromboxane B₂ (TXB₂) and prostaglandin E₂ (PGE₂) were increased in fish fed SO, they were not significantly different from those of the other two treatments.     

Separation and recovery of vanadium from leached solution of spent residuehydrodesulfurization (RHDS) catalyst using solvent extraction

Leached solution, generated by oxalic acid washing of spent residue hydrodesulfurization (RHDS) catalyst, was used for separation and recovery of vanadium. First of all, solvent extraction, using mixture of 20% (v/v) Alamine-336 and 5% (v/v) tri-butyl phosphate (TBP) as a phase modifier, was conducted to extract molybdenum completely at pH 0.50. Then molybdenum-free solution was used for vanadium extraction at pH 1.25 with 20% Alamine-336 and 5% TBP. Stripping of vanadium from loaded organic solution was performed with 1.5 M H₂SO₄ at O/A phase ratio of 5:1 where more than 99% of vanadium was stripped in two stages. The stripped vanadium solution was further processed by precipitating with ammonium hydroxide to recover ammonium-meta-vanadate which was calcined to obtain vanadium pentoxide. Finally a conceptual process was established for recovery of high purity vanadium pentoxide from oxalic acid leached solution of spent residue hydrodesulfurization (RHDS) catalyst.     

Structural importance of thecis-5 ethylenic bond in the endogenous desaturation product of dietary elaidic acid,cis-5,trans-9 18∶2 acid,for the acylation of rat mitochondria phosphatidylinositol

When rats were fed elaidic (trans-9 18∶1) acid at a high load in diets that were otherwise marginally or almost completely deficient in linoleic (cis-9,cis-12 18∶2) acid, elaidic acid was desaturated tocis-5,trans-9 18∶2 acid. This polymethylene-interrupted acid was then incorporated into most phospholipids from rat mitochondria, cardiolipin being an exception. Its level of esterification in phospholipids followed the increasing order: phosphatidylethanolamine <phosphatidylcholine < phosphatidylinositol (PI). The content ofci-5,trans-9 18∶2 acid decreased in organs in the order liver > kidney > heart. The levels ofcis-5,trans-9 18∶2 acid increased in mitochondria phospholipids as the level of linoleic acid was lowered in the diet. In liver mitochondria PI, it reached 16% of total fatty acids. After hydrolysis of liver mitochondria PI withNaja naja phospholipase A₂, we observed that elaidic acid was essentially esterified to position 1 at the expense of saturated acids, whereascis-5,trans-9 18∶2 acid was exclusively esterified to position 2, along with 20∶3n−9 and 20∶4n−6 acids. As a consequence, the sums of saturated andtrans-9 18∶1 acids on the one hand, and of 20∶3n−9, 20∶4n−6, andcis-5,trans-9 18⩺2 acids on the other hand, remained fairly constant in liver mitochondria PI (ca. 55 and 30%, respectively). Becausetrans-9 18∶1 andcis-5,trans-9 18∶2 acids differ only by thecis-5 ethylenic bond, which is also present in 20∶3n−9 and 20∶4n−6 acids, this distribution pattern indicates that thecis-5 double bond, rather than any other ethylenic bond, may be of major structural importance for channeling fatty acids to position 2 of PI.     

Fluorescent lipids of bovine brain white matter

Two fluorescent lipids were isolated from a chloroform-methanol (2∶1 v/v) extract of bovine brain white matter by two-step preparative thin layer chromatography on Silica Gel G. The first step was performed with chloroform-diethyl ether-acetic acid (70∶30∶1 v/v) as developing solvent and revealed a single fluorescent band below the solvent front. The band was scraped off, and the lipid was eluted in chloroform and reapplied to Silica Gel G plates. In the second step, benzene-methanol-ethyl acetate (85∶10∶5 v/v) as developing solvent revealed two fluoresent bands (A and B) with R_f values of 0.72 and 0.65. The lipids were eluted and the UV and visible absorption spectra were measured in heptane, as were the excitation and fluorescence spectra. Sulfuric acid absorption spectra (2 and 24 hr treatment at 22 C) as well as the resulting excitation and fluorescence spectra were also determined. The fluorescent lipids reacted positively in a number of nonspecific color tests for steroids, but the chemical nature of these minor components of the neutral lipid fraction remains to be established.     

Adsorption of weak and non-electrolytes by activated carbon

Four activated carbons, one of them commercially available Darco active carbon and the remaining three from a series of coconut charcoals steam activated to varying degrees, are used to study the adsorption of weak and non-electrolytes. Introduction of —CI into the CH₃COOH molecule increases adsorption onto activated carbon while —OH and —NH₂ have the opposite effect. Substitution in the benzene ring shows that adsorption from aqueous solutions is in the order —NH₂, >—OH, >CO₂, >(—OH + —COOH). Effect of polarity of solvent on adsorption capacities is studied in H₂O, CHCl₃ and C₆H₆. Substitution of —Cl into the CH₃COOH molecule invariably increases the adsorption irrespective of the polarity of the solvent. On introducing a specific group in the benzene ring the adsorption is in the order: aniline ? phenol > benzoic acid > salicylic acid in H₂O medium but in CHCl₃ and C₆H₆ media aniline ? phenol > salicylic acid > benzoic acid. However, on comparing the results of individual adsorbates in three media, generally the magnitude of adsorption is H₂O > C₆H₆ ? CHCl₃. Adsorption of lower aliphatic acids (formic to caproic) from aqueous solutions increases regularly as one ascends the homologous series—a behaviour known as Traube's rule; however, of all the surface area available for N₂ adsorption, only a fraction of it is available for adsorption of the aliphatic acids.     

Effect of extraction methods on lipid yield and fatty acid composition of lipid classes containing γ-linolenic acid extracted from fungi

The effect of extraction procedures on the lipid yield and fatty acid composition of total lipid and main lipid structures (phospholipids, diacylglycerols, triacylglycerols, free fatty acids, and sterol esters) of fungal biomass (Mucor mucedo CCF-1384) containing γ-linolenic acid (GLA) was investigated. Seventeen extraction methods, divided into three groups, were tested: six with chloroform/methanol, five with hexane/alcohols, and six with common solvents or mixtures. The chloroform/methanol procedure (2∶1) was selected as standard, where lipid yield (TL/DCW, total lipid per dry cell weight) was 17.8%, considered to be 100% of lipids present. All chloroform/methanol extractions yielded more than 83% recorvey of lipids. Use of hexane/isopropanol solvent systems led to a maximum of 75% recovery. The best lipid yield was achieved by a two-step extraction with ethanol and hexane (120%). Extraction efficiency of the other solvent systems reached a maximum of 73%. Triacylglycerols were the main structures of lipid isolated; only methanol-extracted lipid contained 58.5% phospholipids. The fatty acid content of total recovered lipid was variable and depended on both the lipid class composition and the solvent system. GLA concentrations in total lipids isolated by hexane/alcohol procedures (7.3–10.7%) are comparable with classical chloroform/methanol systems (6.5–10.0%). The maximal GLA yield was obtained with chloroform/methanol/n-butanol/water/0.1 M ethylenediaminetetraacetic acid (EDTA) (2∶1∶1∶1∶0.1, by vol) and after two-step extraction with ethanol and hexane (14.3 and 13.7 g GLA/kg DCW, respectively). The highest GLA content was analyzed in the phospholipid fraction (16.1%) after using chloroform/methanol/n-butanol/water/0.1 M EDTA (2∶1∶1∶1∶0.1, by vol). Remarkably low concentrations of polyunsaturated fatty acids were determined in the free fatty acid fraction.     

The effects of a dietary oxidized oil on lipid metabolism in rats

This study was carried out to investigate the effects of a dietary oxidized oil on lipid metabolism in rats, particularly the desaturation of fatty acids. Two groups of rats were fed initially for a period of 35 d diets containing 10% of either fresh oil or thermally treated oil (150°C, 6d). The dietary fats used were markedly different for lipid peroxidation products (peroxide value: 94.5 vs. 3.1 meq O₂/kg; thiobarbituric acid-reactive substances: 230 vs. 7 μmol/kg) but were equalized for their fatty acid composition by using different mixtures of lard and safflower oil and for tocopherol concentrations by individual supplementation with dl-α-tocopherol acetate. In the second period which lasted 16 d, the same diets were supplemented with 10% linseed oil to study the effect of the oxidized oil on the desaturation of α-linolenic acid. During the whole period, all the rats were fed identical quantities of diet by a restrictive feeding system in order to avoid a reduced food intake in the rats fed the oxidized oil. Body weight gains and food conversion rates were only slightly lower in the rats fed the oxidized oil compared to the rats fed the fresh oil. Hence, the effects of lipid peroxidation products could be studied without a distortion by a marked reduced food intake and growth. To assess the rate of fatty acid desaturation, the fatty acid composition of liver and heart total lipids and phospholipids was determined and ratios between product and precursor of individual desaturation reactions were calculated. Rats fed the oxidized oil had reduced ratios of 20∶4n−6/18∶2n−6, 20∶5n−3/18∶3n−3, 20∶4n−6/20∶3n−6, and 22∶6n−3/22∶5n−3 in liver phospholipids and reduced ratios of 20∶4n−6/18∶2n−6, 22∶5n−3/18∶3n−3, and 22∶6n−3/18∶3n−3 in heart phospholipids. Those results suggest a reduced rate of desaturation of linoleic acid and α-linolenic acid by microsomal Δ4-, Δ5-, and Δ6-desaturases. Furthermore, liver total lipids of rats fed the oxidized oil exhibited a reduced ratio between total monounsaturated fatty acids and total saturated fatty acids, suggesting a reduced Δ9-desaturation. Besides those effects, the study observed a slightly increased liver weight, markedly reduced tocopherol concentrations in liver and plasma, reduced lipid concentrations in plasma, and an increased ratio between phospholipids and cholesterol in the liver. Thus, the study demonstrates that feeding an oxidized oil causes several alterations of lipid and fatty acid metabolism which might be of great physiologic relevance.     

Incorporation of n−3 fatty acids of fish oil into tissue and serum lipids of ruminants

This study examines the biohydrogenation and utilization of the C₂₀ and C₂₂ polyenoic fatty acids in ruminants. Eicosapentaenoic (20∶5n−3) and docosahexaenoic (22∶6n−3) acids were not biohydrogenated to any significant extent by rumen microorganisms, whereas C₁₈ polyenoic fatty acids were extensively hydrogenated. The feeding of protected fish oil increased the proportion of 20∶5 from 1% to 13–18% and 22∶6 from 2% to 7–9% in serum lipids and there were reductions in the proportion of stearic (18∶0) and linoleic (18∶2) acids. The proportion of 20∶5 in muscle phospholipids (PL) increased from 1.5% to 14.7% and 22∶6 from 1.0% to 4.2%; these acids were not incorporated into muscle or adipose tissue triacylglycerols (TAG). In the total PL of muscle, the incorporated 20∶5 and 22∶6 substituted primarily for oleic (18∶1) and/or linoleic (18∶2) acid, and there was no consistent change in the porportion of arachidonic (20∶4) acid.