Phospholipids of pork muscle tissues

Phospholipids of Animal and Marine Origin: Structure, Function, and Anti-Inflammatory Properties

In this review paper, the latest literature on the functional properties of phospholipids in relation to inflammation and inflammation-related disorders has been critically appraised and evaluated. The paper is divided into three sections: Section 1 presents an overview of the relationship between structures and biological activities (pro-inflammatory or anti-inflammatory) of several phospholipids with respect to inflammation. Section 2 and Section 3 are dedicated to the structures, functions, compositions and anti-inflammatory properties of dietary phospholipids from animal and marine sources. Most of the dietary phospholipids of animal origin come from meat, egg and dairy products. To date, there is very limited work published on meat phospholipids, undoubtedly due to the negative perception that meat consumption is an unhealthy option because of its putative associations with several chronic diseases. These assumptions are addressed with respect to the phospholipid composition of meat products. Recent research trends indicate that dairy phospholipids possess anti-inflammatory properties, which has led to an increased interest into their molecular structures and reputed health benefits. Finally, the structural composition of phospholipids of marine origin is discussed. Extensive research has been published in relation to ω-3 polyunsaturated fatty acids (PUFAs) and inflammation, however this research has recently come under scrutiny and has proved to be unreliable and controversial in terms of the therapeutic effects of ω-3 PUFA, which are generally in the form of triglycerides and esters. Therefore, this review focuses on recent publications concerning marine phospholipids and their structural composition and related health benefits. Finally, the strong nutritional value of dietary phospholipids are highlighted with respect to marine and animal origin and avenues for future research are discussed.

Phospholipid oxidation in emulsions

The autoxidation of purified phosphatidyl ethanolamine (PE) and phosphatidyl choline (PC), extracted from egg and soybean lipids, was followed by oxygen uptake measurements in emulsified systems. All emulsified phospholipid fractions had comparable activation energies. Measurement by various physico‐chemical tests was made of specific changes in the phospholipid molecule during autoxidation. PE oxidized more rapidly and absorbed more oxygen than PC. Higher 2‐thiobarbituric acid test and diene and triene conjugation absorbance values were observed for PE than for PC. Of the two major polyunsaturated fatty acids in egg phospholipids, arachidonic acid disappeared at a more rapid rate during oxidation while the concentration of linoleic acid decreased to a level that was relatively constant. Although typical unsaturated fatty acid oxidation appeared to occur in all phospholipid fractions, oxidation in aqueous emulsions was only partly a function of fatty acid composition. The nitrogen moieties, ethanolamine and choline influenced the induction period for the oxidation of PE and PC respectively.

Determination of plasmalogens after treating with a 2,4-dinitrophenylhydrazine-phosphoric acid reagent

A method for the quantitative determination of plasmalogens is described. Glycerophosphatide fractions from animal and plant sources were treated with a 2,4-dinitrophenylhydrazine-phosphoric acid reagent. The plasmalogen content was estimated by two different procedures after a single treatment with reagent: a) by determining the phosphorus content of diacyl phospholipid and (2-acyl) lysophospholipid separated by thin-layer chromatography, b) by spectrophotometric determination of the 2,4-dinitrophenylhydrazones and phosphorus assay of the original untreated sample. The total plasmalogen content of an unfractionated extract may be determined easily by the latter procedure.The method described gives results comparable with those from the p-nitrophenylhydrazine method and iodination procedure. The usefulness of this 2,4-dinitrophenylhydrazine-phosphoric acid treatment for further structural analyses of plasmalogens is discussed.

Fatty acids in phospholipids isolated from human red cells

Total lipids of packed erythrocytes from healthy men 22 to 25 years old were extracted with chloroform-methanol mixture. Phospholipid classes were separated from neutral lipids and pigments on a silicic acid column. Phosphatidyl inositol (PI) was freed of its contaminants phosphatidyl ethanolamine (PE) and phosphatidyl serine (PS) on an aluminum oxide column. Additional silicic acid columns with modified solvent systems were needed for complete separation of other overlapped phospholipid classes. The identification of phospholipids in each eluted fraction was accomplished by TLC, using the appropriate spray tests and reference compounds, and confirmed on each of the isolated phospholipids by IR spectrophotometry.The total content of phospholipids as determined by phosphorus analysis was found to be 2.63 mg/ml of packed cells. These phospholipids were found to have the following composition (in per cent of total phospholipid): PI, 2.3; PE, 13.4; ethanolamine plasmalogen (EP), 14.5; PS, 3.9; lecithin (L), 34.2; choline plasmalogen (CP), 1.4; sphingomyelin (Sph), 28.4 and lysolecithin (LL), 1.7. The fatty acid composition of each phospholipid was determined by GLC. The average number of double bonds per fatty acid in the isolated phospholipids was found to be as follows: PI, 1.5; PE, 1.9; EP, 3.6; PS, 2.1; L, 1.0; CP, 2.0; Sph, 0.2 and LL, 0.5. The positional distribution of fatty acids in both L and PE was ascertained by selective enzymatic hydrolysis with phospholipase A. Saturated fatty acids of L were esterified predominantly in the alpha'-position, whereas in PE only 63.9 mole per cent of the saturated fatty acids were found in this position.

Low temperature direct methylation of lipids in biological materials

The procedure for low temperature methylation of fatty acids in lipids by sulfuric acid-methanol has been adapted to direct methylation of fatty acids of lipids in biological materials without prior extraction of the lipids. Successful application requires a solution or a suspension of fine particles of the lipid bearing material in ether. Concentrated sulfuric acid is added to the solution or suspension at low temperatures followed by addition of absolute methanol. The acid is neutralized by methanolic KOH and the esters extracted. Application of the method to prepare methyl esters of lipids in cream, blood serum, swine liver and kidney tissue, and cells of yeast onStaphylococcus aureus show that fatty acid composition based on this method compares with that determined by methylation of extracted lipids.

Phospholipids of human serum

Phospholipids extracted from normal human serum were fractionated into lecithin, lysolecithin, sphingomyelin, phosphatidyl ethanolamine, lysophosphatidyl ethanolamine, phosphatidyl serine, and phosphatidyl inositol. Identification of each was established by thin-layer chromatography and infrared spectrophotometry. The content of plasmalogen was determined in both lecithin and phosphatidyl ethanolamine fractions. The composition of fatty acids and fatty aldehydes in isolated phospholipids is presented. The degree of unsaturation as reflected in the average content of double bonds per molecule of the fatty acids in phospholipids was: lecithin 1.2, choline plasmalogen 2.1, lysolecithin 0.6, sphingomyelin 0.2, phosphatidyl ethanolamine 2.8, lysophosphatidyl ethanolamine 1.0, phosphatidyl serine 1.0, and phosphatidyl inositol 1.8. Both chlline and ethanolamine plasmalogen aldehydes were predominantly saturated. Molecular weight of each phospholipid was calculated from determined fatty acid and fatty aldehyde compositions; the phosphorus factor for each phospholipid was computed. On a weight percent basis, lecithin, sphingomyelin, and lysolecithin accounted for 95% of the total phospholipids. The ethanolamine-containing phospholipids accounted for 2.5%, and the remainder was divided among phosphatidyl inositol, choline plasmalogen and phosphatidyl serine.