Composition of total lipids in rapeseed

Total lipids in medium and low erucic acid cul-tivars of rapeseed(Brassica napus var. Sinus and Janpol, resp.) were fractionated into polar and non-polar constituents. Triglycerides, diglycerides, mono-glycerides, free fatty acids, sterol esters, sterols, phos-pholipids and glycolipids were quantitated and their fatty acid compositions determined. Triglycerides and phospholipids constituted 92 and 3.4%, resp., of the total lipid from each cultivar. Triglycerides were lower in saturated fatty acids but higher in monoun-saturated acids and linolenic acid than other lipid fractions. Phospholipids and glycolipids were higher in linoleic acid content than other lipid classes. Generally, the reduction in long chain, monoenoic, fatty acids was associated with a corresponding increase in oleic acid in most low erucic acid frac-tions.     

Composition of the lipids in cabbage

Cabbage leaves contain 0.16% total lipids of which 51.02% are neutral lipids, 40.78% glycolipids, and 8.18% phospholipids. The predominant fatty acids in the total lipid analysis are linolenic, linoleic, oleic, palmitic, and stearic acids. Linolenic, palmitic, tridecanoic, and oleic are the principal components in the neutral lipid fraction while glycolipids are composed mainly of linolenic, palmitic, lauric, myristic, and tricosanoic acids. Phospholipids are high in palmitic, linolenic, and linoleic acids. Both glucose and galactose were observed in the glycolipid fraction.     

Total and polar lipids in soybean protein meals

Soybean protein meals obtained by various oil extraction methods have different neutral oil content, and they may contain differnet amounts of polar lipids. Three soy protein meals obtained by different processing methods were extracted by two solvents consecutively, chloroform/methanol (2:1, vol/vol) and water-saturated butanol, for total lipid analysis. The organic flour (i.e., ground soybean) containted 15.52% total lipids; the high protein dispersibility index flour from extrusion-expelling processing and the white flour from conventional solvent extraction contained 11.20 and 1.84% total lipids, respectively. Organic flour contained more polar lipids than the other two protein meals on a dry-weight meal basis. Chloroform/methanol extracted most of the lipid from the meals, whereas water-saturated butanol resulted in an extract with more polar lipids than that from chloroform/methanol extraction.     

Quantitative content of total polar lipids in soybean seeds

The exhaustive stepwise extraction of soybean seeds was performed in a specially designed apparatus by a solvent system containing chloroform, methanol, water, mineral acid, and antioxidant in an inert atmosphere. The yield of total lipids was as high as 99.95%. The possible artifact content in the extracted lipids was < 0.5%. Separation of polar lipids and determination of constituent groups of these compounds (fatty acyl groups and phosphate) has shown that 36.7 μmole (±4.6%) of polar lipids may be contained in 1 g dry wt of seeds, 25.9 μmole (±1%) of this amount being phospholipids.     

Fatty acid composition of polar lipids in goats' milk

Silicic acid column chromatography was used to separate the polar lipids of goats' milk into glycolipid, phosphatidylethanolamine, phosphatidylserine plus phosphatidylinositol, phosphatidylcholine, and sphingomyelin fractions. Each fraction was purified by column chromatography and its fatty acid profile determined by gas liquid chromatography and mass spectrometry. The glycerophospholipids each contained 18∶1 as the predominant fatty acid (∼45%). The sphingolipids contained a high percentage of long-chain saturated fatty acids (C₂₂ to C₂₄>45%); the glycolipid fraction also contained ca. 2% 2-hydroxy fatty acids. The data represent a comprehensive cross-sectional study of the major polar lipids found in goats' milks.     

Composition of bovine milk lipids

Recent literature on the composition of milk lipids is reviewed and discussed. Many additional exotic fatty acids, mainly branched chain, keto, hydroxy and isomers containing double bonds, have been identified, often with the aid of mass spectrometry. It is estimated that ca. 500 fatty acids have been found in milk lipids. Components of lipid classes have been isolated and their structure determined, e.g., glucosyl and lactosyl ceramide, sphingomyelin, ether lipids, etc. The fatty acid composition of “protected” milk is discussed. This milk, obtained from cows fed polyunsaturated oils encapsulated with formaldehyde-treated casein, contains about five times more linoleic acid than regular milk. The future of research on milk lipids is promising, as there are still many intriguing problems of separation and identification. One of eight papers presented in the symposium “Milk Lipids,” AOCS Meeting, Ottawa, September 1972. Contribution No. 528, Storrs Agricultural Experiment Station, University of Connecticut, Storrs.     

Chromatographic characterization of internal polar lipids from wool

Wool internal polar lipids were isolated and separated into different fractions based on polarity. Qualitative and quantitative analyses of the different fractions were performed by thin-layer chromatography and thin-layer chromatography coupled to flame-ionization detection, respectively. Cholesterol esters, free fatty acids, sterols, ceramides, glycosylceramides, and cholesterol sulfate were the main components, with ceramides being in the highest proportion. The fatty acid composition of ceramides and glycosylceramides was determined by gas chromatography/mass spectrometry. As for other keratinized tissues, long-chain fatty acids predominated in comparison to either free fatty acids or phospholipid-linked fatty acids; in both cases, stearic and lignoceric acids were the most abundant fatty acids, and a low amount of 18-methyleicosanoic acid was found. This work opens new avenues in the study of lipid rearrangement in more complex and realistic vesicle structures than conventional liposomes.     

Interference of polar lipids with the alkalimetric determination of free fatty acid in fish lipids

An examination of the suitability of an alkalimetric method for the determination of free fatty acid (FFA) contents in fats, oils, and lipid extracts was conducted by comparing AOCS method Ca 5a-40 with a method based on a Chromarod-latroscan thin-layer chromatography-flame-ionization detector (TLC-FID) system. The FFA contents determined by the alkalimetric method were consistently higher than the genuine FFA contents obtained by the latroscan TLC-FID method. Phospholipids were found to be the major components that contributed to the alkali-titratable, nongenuine FFA in the total FFA determined alkalimetrically. Contributions from other polar lipid components were smaller, but they dominated as the proportion of phospholipids fell. The other alkali-titratable polar components may include oxidized lipids and their by-products bound to protein fragments. The accurate determination of FFA contents by alkalimetric methods may only be applicable to those commercially refined fats and oils that contain negligible amounts of phospholipids. Corrections for the alkalimetrically determined FFA contents should be made for those fats and oils with relatively high phospholipid contents by correlating the nongenuine FFA contents and the phospholipid contents.     

Liver lipids of the polar bear,Thalarctos maritimus

The distribution of total and free fatty acids as well as the acids from the glycerides, sterol esters and phospholipids of polar bear liver lipids was ascertained and found to contain somewhat higher levels of unsaturated components as compared to those of such mammals as the pig. Saponification of the liver lipids yielded the hydrocarbons, alcohols and sterols which were analyzed by GLC. The hydrocarbons occurred at an overall level of 55 mg/kg liver or 57.9 mg/100 g total lipids, of which pristane and other saturated hydrocarbons, mainly normal homologs, comprised 2.6 and 5.3 mg/100 g, respectively; the remainder contained squalene (37.7 mg/100 g) and other unsaturated types (12.3 mg/100 g). As based on the total lipids, the levels of fatty alcohols, sterol and glyceryl ethers amounted to 1.65%, 5.9% and 0.03%, respectively. The fatty alcohols displayed about 31 peaks of C₁₂ to C₃₀, of which the hexadecanol and a branched C₂₀ component were prominent.     

Composition of lipids of bovine optic nerve

Lipids from bovine optic nerve were analyzed. The total content of 16.5% by weight included 27.2% nonpolar lipids, 26.1% glycolipids, and 46.7% phospholipids by weight. Free cholesterol was the major component of the nonpolar lipid fraction. The cerebrosides, 73.5% of total glycolipids, were separated by thin layer chromatography (TLC) into two bands (upper and lower) that were present in equal proportion. Cerebroside sulfates comprised about 27.5% of total glycolipids. Gangliosides were also detected in the glycolipid fraction. In order of predominance, choline glycerophospholipids, ethanolamine glycerophospholipids, ethanolamine plasmalogens, serine glycerophospholipids, sphingomyelins, and inositol glycerophospholipids were the major phospholipids. Palmitoyl (16∶0), stearoyl (18∶0), and oleoyl (18∶1) groups were the major acyl groups in all neutral and phospholipid classes. However, ethanolamine glycerophospholipids, serine glycerophospholipids, and inositol glycerophospholipids contained a large percentage of 22∶6 (docosahexaenoyl) group. The major alk-1-enyl groups of the plasmalogens were 16∶0, 18∶0, and 18∶1. Steroyl (18∶0), lignoceroyl (24∶0), and nervonoyl (24∶1) were the major acyl groups in all sphingolipids. Lower cerebroside band and cerebroside sulfates contained large amount of hydroxylignoceroyl (cerebronoyl) and hydroxynervonoyl groups. This investigation was supported by Grants DE-03191 and 2S06-RR-08037 from the National Institutes of Health, Bethesda, MD.     

Total,polar and neutral lipids ofRhizopus arrhizus fischer

The changes in total lipid content, neutral and polar lipids, total fatty acids, and free fatty acids were investigated over a 4 day period in the zygomycete,Rhizopus arrhizus Fischer. The highest concentration of lipids occurred at the 72 hr period. The degree of unsaturation in the total fatty acid fraction increased during the growth period, whereas the degree of unsaturation decreased in the free fatty acid fraction during the same time period. The ratios of neutral to polar lipids over the 4 day period were: 0.75, 0.22, 1.94 and 0.94. The major components of polar lipids were phosphatidyl ethanolamine, lecithin, lysolecithin, and fatty acids. The fatty acids in the mono- and diglycerides were predominately saturated (67–96%). The fatty acids in the triglycerides shifted from a predominately unaturated (69%, 24 hr) to a more saturated pattern (62%, 96 hr).     

Diversity of the polar lipids of the food-borne pathogenListeria monocytogenes

Listeria monocytogenes is a Gram-positive bacterium that can adapt to high salinity and cold. Because the membrane lipids may play a role in its survival and adaptation, we have examined the polar lipids ofL. monocytogenes. Extraction of total lipids fromL. monocytogenes yielded 7±1 mg/mL wet cells. Polar lipids represented 64% of total lipids and contained 9% lipid-phosphorus. Polar lipids were separated into 14 components by two-dimensional thin-layer chromatography. Eight components (88% of polar lipids) contained lipid-phosphorus; among these was one major component (34% of polar lipids). Two other phospholipids were ninhydrin-positive components and accounted for 15% of the polar lipids. Orcinol staining revealed two glyco- or sulfo-lipids accounting for 9% of polar lipids. Five components (4% of polar lipids) were amino components free of phosphorus. The major component contained 46% of its fatty acids as 15:0anteiso, 24% as 17:0anteiso, and 11% as 15:0iso. The fatty acid profile of the remaining polar lipids was variable, consisting primarily of 16:0, 18:0, 15:0anteiso, and 17:0anteiso. Their unsaturation level was ≤20%; however, the major phosphoaminolipid component was 46% unsaturated. The ratios of 15:0anteiso/17:0anteiso and 15:0anteiso/15:0iso were similar in all classes, averaging 1.5 and 4.5, respectively. Since the adaptation process to stressful environments involves activation of a membrane transport system for the protectant glycine betaine, the membrane lipids may play a role in enabling transport.     

Determination of polar lipids: Quantitative column and thin-layer chromatography

The structures of the polar lipid classes of plants and animals are presented, their nomenclature discussed, and suggestions are presented for clarification of nomenclature. The three general types of quantitative chromatographic procedures (column chromatography, thin-layer chromatography, and combinations of column and thin-layer chromatography) available for polar lipids are reviewed and a new quantitative two-dimensional thin-layer chromatographic procedure is presented. Useful quantitative procedures employing columns of cellulose, silicic acid, silicic acid mixed with silicate, magnesium silicate, and ion exchange celluloses are presented. New findings with diethylaminoethyl cellulose columns are described. New quantitative procedures employing silicic acid, magnesium silicate, or diethylaminoethyl cellulose column chromatography with quantitative thin-layer chromatography are described.     

Myocardial lipids and nucleotides of rats fed olive oil or rapeseed oil

After 1 week, the level of myocardial fatty acids was 4 times greater in young rats fed high erucic rapessed oil than in those fed olive oil. The proportion of erucic acid was 5.6% in the mitochondrial fraction, 15.1% in the microsomal fraction, and 34.8% in the floating fat fraction. This incorporation of erucic acid into triglycerides of the floating fat was evidence of esterification. The changes in the mitochondrial lipids did not alter the content of adenine nucleotides of the myocardium nor its apparent capacity to oxidize substrates.     

Antioxidant activity of polar lipids from nitrite-treated cooked and processed meats

Polar lipids having considerable antioxidant effect on linoleic acid have been isolated from nitrite-treated, laboratory-cooked ground pork and beef during and after four weeks’ storage at 4 C. The antioxidant activity of these polar lipids is 1.5–3 times greater than that of untreated meats. Antioxidatively active polar lipids have also been found in commercially processed, nitrite-containing meats, including pepperoni, ham, frankfurters and bacon. The antioxidant activity of active polar lipids was stable on storage and partially survived treatment with acids and bases and conversion to methyl esters. Separation of the active polar lipids or the active methyl esters by classes gave no fraction in which the antioxidant activity was highly concentrated; however, it seemed to be more highly associated with the polyunsaturates fraction of the methyl esters. Indications are that more than one antioxidant factor is involved and that at least one is associated with the acyl portion of the polar lipids.     

Composition of the lipids in human milk: A review

Recent publications on the composition of human milk are reviewed. The importance of proper sampling is discussed. Fat contents of 2.6–4.5% and cholesterol amounts of 200–650 mg/100 g fat were reported. The phytosterols in milk were increased by the consumption of these sterols. Phytosterols could contribute to the “total cholesterol” in milk if analyses are done colorimetrically. The fatty acid composition is remarkably uniform unless bizarre diets are consumed; the amounts of linoleic acid vary the most. Phospholipids contained more long chain polyunsaturated fatty acids than triacylglycerols. Scientific Contribution No. 786, Storrs Agricultural Experiment Station, University of Connecticut, Storrs, CT 06268.     

Rapid separation of neutral lipids,free fatty acids and polar lipids using prepacked silica sep-Pak columns

A method is described for the separation of neutral lipid, free fatty acid and polar lipid classes using small (600 mg), prepacked silica Sep-Pak columns. Combinations of hexane and methyltertiarybutylether were used to progressively elute cholesteryl ester first then triglyceride from the column. After column acidification, fatty acids were eluted followed by cholesterol. Recoveries of these lipids were 96% or greater. Polar lipids were eluted from the column using combinations of methyltertiarybutylether, methanol and ammonium acetate. Phospholipid classes could not be separated completely from each other. Phosphatidylethanolamine and phosphatidylinositol eluted together, whereas the more polar phosphatidylcholine, sphingomyelin and lysophosphatidylcholine were eluted as a second fraction. Recoveries of each phospholipid was greater than 98%.     

Model of interaction of polar lipids,cholesterol, and proteins in biological membranes

Membranes are proposed to consist of a hydrophobic core, two hydrogen belts, and two polar zones. The hydrogen belts consist of hydrogen bond acceptors, i.e. the carbonyl groups of phospholipids and sphingolipids, and hydrogen bond donors, i.e. the labile hydrogens of cholesterol, sphingosine, proteins, and water. The density of anhydrous hydrogen bonding and the impermeability of the membrane increase with increasing concentrations of cholesterol, sphingolipids, α-hydroxy acyl residues, plasmalogens, and ether phospholipids. Cholesterol owes its membrane-closing properties to its rigid longitudinal orientation in the membrane combined with the latitudinal orientation of the O−H bond. It is suggested that the intrinsic proteins of membranes are held in position by hydrogen bonding, as well as by hydrophobic and electrostatic forces, and that hydrogen bonding also mediates the penetration of membranes by proteins.