Determination of molecular species of ovolecithin using gas chromatography-mass spectrometry

Degradation kinetics study of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) by a validated stability-indicating RP-HPLC method

The chemical stability of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG), a therapeutic agent for neutropenia, was investigated using a validated stability-indicating reversed phase high-performance liquid chromatographic (RP-HPLC) method. The forced degradation of PLAG was carried out under the stress conditions of hydrolysis (alkaline, acidic and various pH buffers), oxidation, photolysis and heat. A simple, sensitive, specific, robust, precise and accurate RP-HPLC method was developed and validated for evaluating the degradation kinetics of PLAG. The chromatographic validation of various parameters, such as system suitability, detection limit, quantification limit, linearity, accuracy, precision, specificity, robustness and stability, was achieved. The method was validated for linearity, accuracy and precision over the concentration range of 0.7813-100μg/mL (r²=0.9999). The proposed method provided excellent stability study of PLAG indicated by the resolution of degradation products from the drug. Degradation of PLAG provided first order kinetics under all experimental conditions. PLAG was catalysed more rapidly in alkaline and acidic conditions than in neutral conditions. PLAG was relatively stable in photolytic and oxidative conditions compared to hydrolysis and thermal conditions, although this drug was not also stable in these conditions. Exposed to high temperature, PLAG was more rapidly catalysed. The activation energy evaluated from the Arrhenius plot was about 110kJ/mol in the thermal conditions. Additionally, PLAG with a t_1/2 of about 400h was very stable at room temperature. Therefore, PLAG was considerably influenced by alkaline and acidic hydrolysis, and thermal degradation.

Monoacetyldiglycerides as new Ca2+ mobilizing agents in rat pancreatic acinar cells

Several monoacetyldiglycerides were synthesized from glycerol in search for new Ca2+ mobilizing agent in vitro. All monoacetyldiglycerides except linolenoyl and phenlycyclopropylcarbonyl derivatives showed activity toward Ca2+ release in pancreatic acinar cells. Linoleoyl and docosahexaenoyl derivatives were chosen for further test and exhibited unique activity.

Yolk lipids

The mature egg yolk of the domestic hen possesses remarkably constant lipid and lipoprotein composition despite much variation in dietary and environmental conditions. The greatest differences are seen in the fatty acid composition of the triacylglycerols which may show significant alterations in the content of the minor acids including certain polyunsaturated acids. The lipid class composition appears to be minimally affected by dietary influences, including the cholesterol content of the diet. The limited dietary influence on the yolk lipid composition extends to different strains of the hens. Genetic selection has led to some increase in the cholesterol content of the egg, but the desired lowering of the cholesterol content of egg yolk has not been realized. Likewise, production of a polyunsaturated fatty acid egg does not appear to be practical. As a result the egg yolk continues to provide a food product of nearly constant composition, which serves to maintain its chemical and physico-chemical properties for reliable utilization in the baking, cosmetic and pharmaceutical industries. The great uniformity in the composition of the egg yolk phospholipids makes them desirable starting materials for partial chemical resynthesis of glycerophospholipids. Partial hydrogenation of the egg yolk lipids promises to further increase the utility of the product as a desirable material for the manufacture of liposomes and liposome based drug products. In contrast, the constancy of the egg yolk composition and the inability to alter it significantly by dietary or genetic means also renders egg yolk undesirable for unlimited human consumption. Excessive ingestion of egg yolk raises plasma lipid and cholesterol levels which are believed to contribute to the development of heart disease. The physico-chemical and biological properties of egg yolk apoproteins have been less extensively investigated and their function is less well understood. The finding that phosvitin is a effective chelator of metal ions and thus an effective antioxidant demonstrates that egg yolk lipoproteins possess as yet unexplored potential for beneficial nutritional, medical and industrial application.

Fast-heating mass spectrometry of phosphatidylcholine, lysophosphatidylcholine, phosphatidylethanolamine, and sphingomyelin

A fast-heating probe and chemical ionization have been used to obtain mass spectra of the synthetic glycerophospholipids 1,2-diacyl-sn-glycero-3-phosphocholine, 1,2-diacyl-sn-glycero-3-phosphoethanolamine, and 1-monoacyl-2-lyso-sn-glycero-3-phosphocholine. The phospholipids investigated gave quasimolecular peaks and fragment ions, with preferential cleavage of the C-O bond (beta position to the phosphorus atom) and loss of phosphoethanolamine or phosphocholine. This technique makes possible the analysis of mixtures of intact phosphatidylethanolamine, phosphatidylcholine, 2-lysophosphatidylcholine, and sphingomyelin isolated from natural sources such as egg yolk or brain. Only minor and inexpensive modifications of a standard mass spectrometer are required.

Molecular analysis of the phospholipids of Escherichia coli k12

Phospholipids from Escherichia coli K12 were converted to 1,2-diacylglycerols with phospholipase C from Bacillus cereus. High-pressure liquid chromatography of 1,2-diacylglycerol p-methoxybenzoates on LiChrosorb RP-18 using 2-propanol/acetonitrile (35:65) as eluant permitted separation of 14 molecular species. The main combinations of fatty acids were 1-16:0-2-16:1, 1-16:0-2-cyclo-17:0 and 1-16:0-2-18:1. Positional isomers were not present. The 1,2-di-16:0 compound was present at a significant level (7-10 mol%). Proportions of molecular species varied between phosphatidylethanolamine, phosphatidylglycerol and cardiolipin. Phospholipid from the outer membrane of E. coli K12 contained a lower level of molecules with two unsaturated chains than was present in the cytoplasmic membrane. The method is sensitive, has good resolving power and employs readily available equipment.

A simple chromatographic method for purification of egg lecithin

Egg lecithin was purified from the CdCl2-lecithin complex by column chromatography on Alumina. The yield from 5 eggs was 2.8 g. The purified lecithin had correct chemical values for pure lecithin and a fatty acid composition similar to lecithin prepared by other methods. The method probably can be adapted for purification of other lipids containing the phosphocholine moiety and for purification of synthetic lecithin.

Studies on trimethylsilyl derivatives of 1,2-dialkylglycerols by gas-liquid chromatography mass spectrometry

Trimethylsilyl derivatives of 1,2-dihexadecyl- and 1,2-dioctadecyl-glycerols were subjected to analysis by a gas chromatograph mass spectrometer system. The mass chromatographic identification of four kinds of glycerophospholipids, 1,2-dihexadecyl, 1-hexadec-1-enyl-2-hexadecanoyl, 1-hexadecyl-2-hexadecanoyl- and 1,2-dihexadecanoyl-glycerol is also described.

Field desorption mass spectrometry of phospholipids. III. Survey of structural types

A survey has been conducted of the behavior of a wide variety of phospholipids and related materials under field desorption mass spectrometric conditions. Phosphatidyl cholines, both acyl and alkyl, phosphatidyl ethanolamies, phosphatidic acids, the corresponding lyso compounds, glycerophosphoryl lipids and sphingolipids are among the species studied. Most of the 50 compounds measured as single species gave M + H as base peak, some associated ions, and fragment ions which became increasingly significant at higher anode temperatures. Problems encountered include interference from organic impurities and alkali metal ions, poor reproducibility of minor ions due to low ion collection rates and potential confusion in structrual assignments caused by reactions occurring on the anode prior to desorption. Various approaches to overcome these difficulties are discussed, and the potential of the field desorption technique for species specific analysis of naturally occurring phsopholipid mixtures is demonstrated by three examples.

Examination of acetolysis products of phosphatidylcholine by gas chromatography-mass spectrometry

A comparison of monoacetyldiglycerides obtained from authentic phosphatidylcholines by acetolysis with those obtained by phospholipase C-acetylation was made to examine the intermolecular acyl migration, the intramolecular acyl migration between C-1 and C-2, and the formation of 1,3-isomer in the acetolysis reaction. Egg yolk phosphatidylcholine also was used. It was revealed that is acetolysis, the intermolecular acyl migration and selective degradation of polyunsaturated fatty acids did not take place at all. The intramolecular acyl migration, including the formation of 1,3-isomer, occurred to a small extent. Appreciable difference was not found in comparison of molecular species compositions of monoacetyldiglycerides derived by both methods from egg yolk phosphatidylcholine, except small differences found in the contents of two kinds of molecular species.

Metabolism of the phosphatidylglycerol molecular species in Escherichia coli

The fractionation, turnover and biosynthesis of the phosphatidylglycerol molecular species of Escherichia coli were studied. Monoacetyldiglycerides derived from phosphatidylglycerol were separated into five subfractions; cis-vaccenyl-palmitoleyl, cis-vaccenyl-cis-vaccenyl, palmityl-palmitoleyl, palmityl-cis-vaccenyl and the disaturated molecular species on a silica gel plate impregnated with silver nitrate. Individual molecular species had different turnover rates. The palmityl-cis-vaccenyl species was metabolized faster than the others. Disaturated species were rather stable. Various phosphatidylglycerol molecular species were synthesized in the presence of sn-glycerol 3-phosphate, palmityl-CoA, palmitoleyl-CoA, cis-vaccenyl-CoA and CTP by the E. coli membrane particulate fraction. When only the proportion of palmityl-CoA among the three acyl-CoAs was increased, the molecular species containing the palmityl residue were increased. Similar results were obtained with the other acyl-CoAs. However, a temperature-sensitive incorporation of unsaturated and saturated fatty acids into phosphatidylglycerol molecular species was observed with no change in the proportions of the three acyl-CoAs, completely reflecting the in vivo unsaturated/saturated ratio.