Analysis of Intact Cholesteryl Esters of Furan Fatty Acids in Cod Liver

Furan fatty acids (F‐acids) are a class of natural antioxidants with a furan moiety in the acyl chain. These minor fatty acids have been reported to occur with high proportions in the cholesteryl ester fraction of fish livers. Here we present a method for the direct analysis of intact cholesteryl esters with F‐acids and other fatty acids in cod liver lipids. For this purpose, the cholesteryl ester fraction was isolated by solid phase extraction (SPE) and subsequently analyzed by gas chromatography with mass spectrometry (GC/MS) using a cool‐on‐column inlet. Pentadecanoic acid esterified with cholesterol was used as an internal standard. GC/MS spectra of F‐acid cholesteryl esters featured the molecular ion along with characteristic fragment ions for both the cholesterol and the F‐acid moiety. All investigated cod liver samples (n = 8) showed cholesteryl esters of F‐acids and, to a lower degree, of conventional fatty acids. By means of GC/MS‐SIM up to ten F‐acid cholesteryl esters could be determined in the samples. The concentrations of cholesteryl esters with conventional fatty acids amounted to 78–140 mg/100 g lipids (mean 97 mg/100 g lipids), while F‐acid cholesteryl esters were present at 47–270 mg/100 g lipids (mean 130 mg/100 g lipids).     

Synthesis of cholesterol esters in the plasma and liver of sheep

A study was made with sheep on the formation in vitro of long chain fatty acid esters of cholesterol by the lecithin-cholesterol-acyltransferase system present in the plasma and the acyl CoA-cholesterol-acyltransferase system present in the liver. The rate of cholesterol esterification in the plasma was 0.024 μmoles/ml/hr. The relative pattern of fatty acids esterified during incubation of the plasma remained constant over the 8 hr period of incubation and was similar to the fatty acids in the plasma cholesteryl esters before incubation began and to the fatty acids in the 2-position of the plasma lecithin. The predominant cholesteryl esters synthesized contained monoenoic and dienoic fatty acids. Unlike the bovine, there was no apparent discrimination in favor of the 18∶2 containing species of plasma lecithin as donors of fatty acids. This difference could be accounted for by the similarity in the 18∶2 content of the phospholipids present in the high density (density >1.062 and < 1.21) and the low density (density > 1.006 and <1.063) lipoprotein fractions of the sheep plasma. The possibility of some discrimination against 20∶4 during cholesterol ester synthesis in the plasma of the sheep cannot be excluded. In the liver, the predominant cholesteryl esters synthesized contained saturated and monoenoic fatty acids; cholesteryl linoleate was synthesized to a very much less extent. There was considerable similarity between the composition of the unesterified fatty acid fraction of the liver before incubation began and the fatty acid composition of the cholesteryl esters synthesized during incubation. Addition of sonicated suspensions of free fatty acids altered markedly the fatty acid pattern of the cholesteryl esters synthesized by the liver slices. From the evidence presented it is concluded that the cholesteryl esters in sheep plasma are syntheized mainly by the plasma lecithin-cholesterol-acyltransferase system. The results are discussed in relation to cholesterol esterification systems demonstrated in the plasma and liver of monogastric animals.     

Cholesteryl ester and triacylglycerol fatty acids in type V hyperlipidemia

The fatty acid compositions of plasma cholesteryl esters (CE) and triacylglycerols (TG) from seven healthy individuals and five patients with type V hyperlipoproteinemia were determined. Very low density (VLDL), low density (LDL) and high density lipoproteins (HDL) were isolated. The lipids were extracted from the lipoproteins and the triacylglycerols and cholesteryl esters separated for analysis. The fatty acid compositions of triacylglycerols from healthy and type V individuals were very similar. The cholesteryl esters from type V patients had increased contents of palmitic and decreased amounts of linoleic and arachidonic acids as compared to the normal individuals. The fatty acid composition of the cholesteryl esters from the high density lipoproteins had the greatest deviation. The fatty acid compositions of the triacylglycerols from the two groups were similar. However, the triacylglycerols in all lipoprotein fractions contained more palmitic and oleic and less linoleic and arachidonic acids than the cholesteryl esters.     

Effect of dietary fat on rat liver microsomal and mitochondrial/lysosomal dolichol,phospholipid and cholesterol

The influence of different fat diets on liver phospholipid, cholesterol and dolichol was studied. Rats were separated into four groups and fed standard laboratory chow (control), a diet containing linolenic acid, a coconut oil diet, or a corn oil-containing diet. After five weeks, microsomes and mitochondrial/lysosomal fractions were prepared from the liver, and lipid compositions were analyzed. No changes in phospholipid content were observed. In control animals, the fatty acid compositions of phosphatidylcholine and phosphatidylethanolamine in the two subfractions were similar. However, these two phospholipids showed different fatty acid patterns, which were altered independently upon dietary treatment. The dietary treatments resulted, in most cases, in decreased cholesterol and dolichol contents and, especially in microsomes, in a decreased level of esterification of both lipids. The fatty acid compositions of cholesteryl esters in the two subfractions showed significant differences and cholesterol was esterified to a large extent with linolenic acid when this fatty acid was supplied in the diet. The same dietary treatment exerted different effects on the cholesterol localized in the two different intracellular compartments. This difference was most pronounced in rats fed the corn oil-containing diet; microsomal cholesteryl esters exhibited increased saturation, whereas cholesteryl esters in the mitochondrial/lysosomal fraction displayed decreased saturation. Dolichyl esters in the two cellular compartments had different fatty acyl compositions, with a considerably higher degree of saturation in microsomes. The various diets influenced the nature of the fatty acid moieties present in the isolated fractions and the effects on the two subfractions were opposite. The diet containing linolenic acid decreased the degree of saturation in microsomal dolichyl esters and increased the degree of saturation in the mitochondrial/lysosomal fraction. The results demonstrate that the fatty acid compositions of both dolichyl and cholesteryl esters display organelle specificity. Both the content of these lipids and their fatty acid compositions are greatly influenced by dietary conditions, and the esterification processes at different cellular locations exhibit independent regulation, regardless of the fatty acid content of the diet.     

Cholesteryl ester compounds containing alkyl branched acyl groups — their preparations,properties and applications

Cholesterol having a reactive hydroxyl group at C₃-position can react with fatty acids to give the corresponding cholesteryl esters. Most of the natural cholesteryl esters consist of straight alkyl chain fatty acids with a high melting point. In oleochemistry it is well known that alkyl branched fatty acids, which are derived from petroleum or the fat and oil industry, have low melting points (mp.) and are chemically more stable if they are saturated acids. We designed alkyl branched fatty acid cholesteryl esters by means of common esterification and found some esters having a low mp. (mostly as a liquid). They had no irritative effect on both animal and human skin. They showed characteristic emulsification properties, namely the formation of either O/W or W/O emulsion coexistence together with other lipid components. Applying them onto human skin, they were able to penetrate towards the stratum corneum and improve the water-retaining ability and the barrier function of the stratum corneum. Based on these properties we have been applying the alkyl branched fatty acid cholesteryl ester, especially the methyl branched isostearic acid cholesteryl ester (IS-CE), to a shampoo and a rinse as hair cosmetics, skin care cosmetics and bath-additive products in the past decade.     

α-Sulfonated fatty acids and esters: Manufacturing process,properties, and applications

α-Sulfonated fatty acid esters, because of their wide-range of application and biological properties, represent an interesting class of surfactants. A technical method for the preparation of α-sulfonated fatty acid esters is described. By using special reaction conditions it is possible to α-sulfonate saturated fatty esters directly without the use of solvents. The use of gaseous SO₃ gives the product in greater than 97% yield. A process for the bleaching of the α-sulfonated fatty esters has been developed, whereby a product of faultless color is produced without the necessity of further purification or separation techniques. The sulfonation and bleaching processes operate continuously. The process has been tried successfully on a commercial scale using the methyl esters of technical fatty acids. Methods for the preparation of α-sulfonated fatty acids are given. The chemical, technical, and biological properties of the α-sulfonated fatty acids and their esters are discussed. α-Sulfonated fatty esters possess good washing and foaming properties, have good biological degradability, possess good skin compatibility and low acute toxicity. They can be considered as surfactant components for phosphate-free or low-phosphate detergents. α-Sulfonated fatty acids and esters also possess other favorable technical properties which allow them to be used in cosmetics, as auxiliary agents in the production of fibers, plastics, and rubber, and in leather manufacture.     

Preparation of fatty acid methyl esters from lipoprotein and macrophage lipid subclasses on thin-layer plates

A simple, accurate, and fast procedure for quantitative analysis of fatty acids (FA) in simple lipid subclasses from different biological specimens is presented. Lipid extracts of isolated plasma lipoproteins (very low, low, and high density lipoproteins; VLDL, LDL, and HDL, respectively) and permanent J774 mouse macrophages were fractionated into lipid subclasses by thin-layer chromatography (TLC) on silica gel 60 plates. Bands comigrating with authentic lipid standards were scraped off under argon and subjected to direct,in situ transesterification with BF₃/MeOH in the presence of the TLC adsorbent. Fatty acid methyl esters were subsequently quantitated by capillary gas chromatography. A comparison of the FA content present in total lipid extracts and in lipid subclasses separated by TLC revealed recoveries ranging from 93 (J774 cell extracts) to 99.7% (LDL). The method described is applicable for the measurement of FA in individual lipid subclasses and was successfully applied to quantitatively analyze the FA composition of the phospholipid, triacylglycerol, and cholesteryl ester fraction derived from VLDL, LDL, and HDL. In J774 lipid extracts, the FA composition of the phospholipid-, monoacylglycerol-, diacylglycerol-, free fatty acid-, triacylglycerol-, and cholesteryl ester fraction was quantitated. In addition we have analyzed the time-dependent loss of the major HDL polyunsaturated fatty acids (18:2, 20:4) in the phospholipid and cholesteryl ester fraction during copper-dependent peroxidation of HDL. We have not encountered analytical problems concerning low FA recoveries from CE-rich lipid extracts as indicated by almost quantitative recoveries of FA in LDL, HDL, and J774 extracts.     

Gas chromatographic separation of cholesteryl esters of fatty acids of different degrees of unsaturation

Cholesteryl esters prepared from the fatty acid methyl esters of linseed oil, pig liver lipids, and Japanese anchovy oil have been separated on the basis of their chain lengths and number of double bonds by gas lipid chromatography on a cyanosiloxane SILAR 10C column. The equivalent chain lengths of cholesteryl esters having acyl groups with 14–22 carbons and 0–6 double bonds are presented. A significant influence of the column temperature on the equivalent chain lengths of the polyenoic fatty acid cholesteryl esters has been found. Separation of the cholestanyl and epicholestanyl esters of linseed oil fatty acids, respectively, under the same conditions is also described.     

Cholesterol esterification and cholesteryl ester hydrolysis by rabbit and human ovaries

Esterification of cholesterol occurred in vitro in rabbit and human ovaries via an acyl CoA-cholesterolO-acyltransferase reaction. The rate of esterification was increased in early pregnancy and may be one of the mechanisms whereby the content of stored ovarian cholesteryl esters is increased during this period. The increased cholesteryl esters were primarily in the form of cholesteryl oleate. The cholesteryl ester fatty acid patterns in both rabbit and human ovaries differed from those in sera, suggesting that a significant portion of these esters may have been derived from in situ synthesis. The rate of hydrolysis of cholesteryl esters during pregnancy was also increased, and occurred at a faster in vitro rate than esterification. Of the agents tested, only soy lecithin was found to significantly enhance the rate of hydrolysis of cholesteryl oleate by ovarian homogenates.     

Fatty acid variability of plasma lipids and cholesteryl esters in adult male twins and their brothers

Variation in the fatty acid composition of fasting plasma lipids and of cholesteryl esters was studied in 69 sets of adult male twins and 25 of their brothers. Genetic variances were estimated using the twin model. In general, monozygotic (MZ) twins were characterized by the smallest within-pair variance, and brothers of twins by the largest. Variation within dizygotic pairs fell intermediate to that of MZ twins and brothers. The present study did not reveal consistent significant (P<0.05) genetic variation in plasma fatty acids from total plasma lipids or cholesteryl esters.     

Changes in the Contents of Cholesterol and Cholesteryl Esters Occurring during Lipase-Catalysed Interesterification Reactions

The free cholesterol and cholesteryl esters isolated on silica column and the total cholesterol from saponified fat samples obtained from untreated butter fat and butter fats interesterified with Pseudomonas fluorescens lipase as catalyst were determined on immobilised OV-351 and phenylmethylsilicone gas chromatographic columns. Fatty acid composition of the cholesteryl esters of the untreated butter fat differed markedly from the fatty acid composition of acylglycerols. The proportions of cholesteryl palmitate, stearate and oleate were clearly higher in the interesterified fats and the proportion cholesteryl linoleate was distinctly lower. Determination of the free cholesterol and cholesteryl esters and the total cholesterol in the fraction of unsaponifiables revealed that, on average, 89% of cholesterol is esterified in the interesterification products, but only 2% in intact butter fat.     

Two‐stage synthesis of sorbitan esters,and physical properties of the products

A series of sorbitan‐fatty acid esters with various fatty acid/sorbitol ratios was prepared using a 2‐stage process. In the first stage, sorbitol was dehydrated to sorbitan at 180 °C (using phosphoric acid as catalyst), and in the second stage, the sorbitan was esterified with the fatty acid at 220 °C (sodium hydroxide as catalyst). The course of the reaction was monitored and the composition of final products was determined by thin‐layer chromatography using a flame‐ionisation detector (TLC‐FID). The properties (surface tension, melting points, viscosity) of prepared sorbitan esters depend on the molecular ratio of fatty acid and sorbitol. The described method is suitable for the preparation of sorbitan esters at industrial scale.     

Effects on plasma lipids and fatty acid composition of very low fat diets enriched with fish or kangaroo meat

The effects of very low fat diets (<7% energy) enriched with different sources of long chain (C20 and C22) polyunsaturated fatty acids (PUFA) on plasma lipid levels and plasma fatty acids (PUFA) on plasma lipid levels and plasma fatty acid composition were studied in 13 healthy volunteers. Three diets provided 500 g/day of tropical Australian fish (rich in arachidonic acid and docosahexaenoic acid), southern Australian fish (rich in docosahexaenoic acid) or kangaroo meat (rich in linoleic and arachidonic acids). The fourth diet was vegetarian, similarly low in fat but containing no 20- and 22-carbon PUFA. Subjects ate their normal or usual diets on weeks 1 and 4 and the very low fat diets in weeks 2 and 3. Weighed food intake records were kept, and weeks 2, 3 and 4 were designed to be isoenergetic with week 1. Plasma cholesterol levels fell significantly on all diets within one week. There were reductions in both low density (LDL) and high density lipoprotein (HDL) cholesterol levels, with effects on HDL cholesterol being more consistent. There were no consistent or significant effects on total triglyceride levels despite the high carbohydrate content of the diets. On all diets the percentage of linoleic acid fell in the plasma phospholipid and cholesteryl ester fractions, while the percentage of palmitic acid in the phospholipids and cholesteryl esters and palmitoleic acid in the cholesteryl ester fraction rose on all diets. The percentage of arachidonic acid rose in the phospholipid and cholesteryl esters on the two diets that were good sources of this fatty acid (tropical fish and kangaroo meat). The percentage of docosahexaenoic acid also rose on the two diets that were the richest sources of this fatty acid (the fish diets), and the percentage of eicosapentaenoic acid rose in the phospholipid and cholesteryl esters in proportion to the dietary level of this fatty acid (southern fish > kangaroo > tropical fish). The changes in fatty acid composition were almost completely reversed within seven days of returning to the usual higher fat diets.     

Fatty acid interrelationships in plasma,liver, muscle and adipose tissues of cattle fed safflower oil protected from ruminal hydrogenation

Steers were given diets containing formaldehyde-treated casein-safflower oil supplements, in which the constituent 18∶2 was protected from ruminal hydrogenation. A similar group was given unsupplemented diets. The fatty acid compositions of plasma, liver, muscle and adipose tissue lipids were determined in both groups of cattle after 0, 2, 4 and 8 weeks of experimentation. The proportion of 18∶2 in the triglycerides was markedly increased on feeding the supplement and the rate of incorporation into the plasma triglycerides was higher than that in the triglycerides of muscle and adipose tissue. Associated with this increase there were compensatory decreases in the proportions of 16∶0 and 18∶1 but no consistent change in the proportion of 18∶0. The proportion of 18∶2 in the plasma phospholipids and cholesteryl esters was initially much higher than in the triglycerides and this was further increased by feeding the safflower oil supplement. A linear relationship existed between the proportion of 18∶2 in the phospholipids and cholesteryl esters of plasma. The supplement also caused substantial increases in the proportion of 18∶2, both in phospholipids from liver and muscle and in cholesteryl esters from liver, and there were compensatory decreases in the proportions of other unsaturated fatty acids, e.g., 18∶1, 18∶3, 22∶6. These studies demonstrate that when ruminal hydrogenation was circumvented by feeding formaldehyde-treated casein-safflower oil particles, the linoleic acid was absorbed and the pattern of incorporation into plasma and tissue lipids was similar to that in nonruminants.     

Nonvolatile α-branched chain fatty acid derivatives: III. Addition of acid chlorides,anhydrides and amides to terminal olefins

At-butyl peroxide initiated free radical reaction was employed for the preparation of α-branched fatty acid chlorides, which were then converted in situ to methyl esters. Similarly prepared were an α-branched fatty acid amide and an α-branched acid anhydride. The latter was converted to the methyl ester. The use of the acid chloride and acid anhydride permitted reduction in the molar ratio of reactants to half or less than that used in the addition of esters to terminal olefins without affecting the yield. The resulting increase of α-branched product concentration in the reaction mixture also made isolation of the product easier. The direct addition of a variety of stearic acid derivatives to 1-decene under the same conditions (20:4:1.2 molar ratio of reactants at 160 C) gave the following olefin based yield order: stearoyl chloride > stearic anhydride > stearamide and methyl stearate > stearic acid. Presented at the AOCS Meeting, Chicago, October 1967. E. Utiliz. Res. Dev. Div., ARS, USDA.     

The effect of incubation temperature on yolk lipid parameters during embryonic development of the alligator (Alligator mississippiensis)

The effect of incubation temperature (30 and 33°C) on yolk lipid uptake and changes in the alligator has been studied. Notable changes occurred in the lipid and fatty acid compositions of the yolk. Triacylglycerols and phospholipids were the major lipid components of the yolk at the start of incubation. However, during incubation the level of cholesteryl esters increased considerably to become a major lipid component of the yolk at hatching. This increase in cholesteryl ester level occurred at a much earlier time in the eggs incubated at 33°C. The cholesteryl esters which accumulated within the yolk showed much higher levels of oleic acid. The triacylglycerols and phospholipids of the yolk both contained unusually high levels of palmitoleic acid. Their fatty acid compositions remained relatively unchanged during incubation. The lipid composition of the liver toward the end of the incubation period reflected the changes that occurred within the yolk. Thus the percentage of cholesteryl esters in the liver lipid of embryos incubated at 30 and 33°C were 7 and 40%, respectively. The accumulated cholesteryl esters also showed a significantly higher content of oleic acid. The differences in the yolk and tissue lipids during incubation at the two temperatures are discussed with reference to the respective rates of embryonic development but in particular with respect to the feature of temperature-dependent sex determination.     

Preparation,chromatography and mass spectrometry of cholesteryl ester and glycerolipid-bound aldehydes

To identify lipid ester core aldehydes (aldehydes still bound to parent lipid molecules) among the secondary products of peroxidation, we have prepared reference standards of cholesteryl esters, diacylglycerols and the common glycerophospholipids (GPL) containing an aldehyde function. We subjected the unsaturated lipid esters to hydroxylation with osmium tetroxide and to carbon-carbon bond cleavage with periodic acid. The resulting aldehyde esters (mainly 5-oxovalerates and 9-oxononanoates of cholesterol and the glycerolipids) were isolated and purified by thin-layer chromatography (TLC) and reverse-phase high-performance liquid chromatography (HPLC). Liquid chromatography/mass spectrometry (LC/MS) was used to identify the cholesteryl and other neutral lipid ester aldehydes as the dinitrophenylhydrazones (DNPH). The choline (CGPL) and ethanolamine (EGPL) glycerophospholipids containing core aldehydes were identified by fast atom bombardment mass spectrometry (FAB-MS) and by gas chromatography/mass spectrometry (GC/MS) of the aldehyde-containing diacylglycerol moieties following dephosphorylation with phospholipase C and preparation of the methoximes (MOX) and the trimethylsilyl (TMS) ethers. The lipid esters containing the C₅ and C₉ aldehydes are chemically stable compounds with excellent chromatographic properties yielding mass spectra characteristic of the parent compounds. The overall yield of the core aldehydes was 10–20% of the unsaturated starting material. Part of this work was presented at the Annual AOCS Meeting, Chicago, IL, May, 1991 (see ref. 1).     

Hepatoma,host liver,and normal rat liver neutral lipids as affected by diet

Groups of normal and hepatoma (7288CTC) bearing rats were maintained on normal chow and fat-free diets for 4 weeks. Normal liver, host liver, and hepatoma neutral lipids were examined in detail and compared. Water content, unaffected by diet was: hepatoma, 82 percent; host liver, 71 percent; and normal liver, 67 percent. The fat-free diet had no effect upon the hepatoma neutral lipids but elevated the triglyceride level in normal and host liver, shifted the triglyceride carbon number distribution to lower mol wt, and elevated the percentage of monoenoic acids in triglycerides and cholesteryl esters. Host triglyceride concentrations were ca. half, and cholesterol levels were reduced moderately relative to normal liver values. Hepatoma cholesterol levels were higher and triglyceride concentrations lower than normal and host liver values. Hepatoma triglycerides differed dramatically from liver and were characterized by increased concentrations of high mol wt species and a fivefold increase in the percentage of C-20 and C-22 fatty acids. The percentage of C-20 and C-22 fatty acids in hepatoma cholesteryl esters also increased ca. fivefold relative to liver. The data indicate that the systems that regulate triglyceride and cholesteryl ester fatty acid composition in liver do not control the compositions of these lipid classes in this hepatoma. The unchanged high level of essential fatty acids in the hepatoma lipids from the fat-free fed animals demonstrates the hepatoma's ability to absorb and conserve specific fatty acids.     

Fatty acid composition of erythrocyte,platelet, and serum lipids in strict vegans

The fatty acid composition of erythrocytes, platelets, and serum lipids was compared between subjects who had been eating a strict uncooked vegan diet (“living food”) for years and omnivore controls. The vegan diet contains equal amounts of fat but more monounsaturated and polyunsaturated and less saturated fatty acids than the mixed diet of the control group. In vegans, the proportion of linoleic acid was greater in all lipid fractions studied. Also, the levels of other n−6 fatty acids were greater, with the exception of arachidonic acid levels, which were similar in most fractions. In erythrocytes, platelets and serum phospholipid fractions, this increase was mainly at the expense of the n−3 fatty acids. The proportions of eicosapentaenoic and docosahexaenoic acid were only 29–36% and 49–52% of those in controls, respectively. In vegans the ratio of n−3 to n−6 fatty acids was only about half that in omnivores. In addition to the lower levels of n−3 fatty acids, the proportions of palmitic and stearic acids were lower in serum cholesteryl esters, triglycerides and free fatty acids of vegans. The proportion of oleic acid was slightly lower only in serum cholesteryl esters and erythrocyte phosphatidylserine. The results show that, in the long term, the vegan diet has little effect on the proportions of oleic and arachidonic acids, whereas the levels of n−3 fatty acids are depressed to very low levels with prolonged consumption of the high linoleic and oleic acid components of this diet.     

Black currant seed oil feeding and fatty acids in liver lipid classes of guinea pigs

Guinea pigs were fed one of three diets containing 10% black currant seed oil (a source of gamma-linolenic (18∶3 n−6) and stearidonic (18∶4 n−3) acids), walnut oil or lard for 40 days. The fatty acid composition of liver triglycerides, free fatty acids, cholesteryl esters, phosphatidylinositol, phosphatidylserine, cardiolipin, phosphatidylcholine and phosphatidylethanolamine were determined. Dietary n−3 fatty acids found esterified in liver lipids had been desaturated and elongated to longer chain analogues, notably docosapentaenoic acid (22∶5 n−3) and docosahexaenoic acid (22∶6 n−3). When the diet contained low amounts of n−6 fatty acids, proportionately more of the n−3 fatty acids were transformed. Significantly more eicosapentaenoic acid (EPA) (20∶5 n−3) was incorporated into triglycerides, cholesteryl esters, phosphatidylcholine and phosphatidylethanolamine of the black currant seed oil group compared with the walnut oil group. Feeding black currant seed oil resulted in significant increases of dihomogamma-linolenic acid (20∶3 n−6) in all liver lipid classes examined, whereas the levels of arachidonic acid (20∶4 n−6) remained relatively stable. The ratio dihomo-gamma-linolenic acid/arachidonic acid was significantly (2.5-fold in PI to 17-fold in cholesteryl esters) higher in all lipid classes from the black currant seed oil fed group.