Impedance analysis of a phosphatidylcholine-phosphatidylethanolamine system in bilayer lipid membranes

Electrochemical impedance spectroscopy was used for the study of two-component lipid membranes. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were to be investigated, because of their presence in biological membranes. Capacitance values of pure components are 0.62 and 0.32 μF cm⁻², respectively. The 1:1 complex was formed during formation of the PC-PE lipid membrane. Formation of the complex can explain the deviation from the additivity rule. This equilibrium was described by mathematical equations and was further verified experimentally. Adequate equations let us calculate such parameters as: capacitance of the complex molecule, area occupied by the complex molecule as well as the stability constant of the complex.     

Influence of deep-fat frying process on phospholipid molecular species composition of Sardina pilchardus fillet

The effects of deep-fat frying performed using different culinary fats (extra virgin olive oil, conventional sunflower oil and high-oleic sunflower oil) and different frying temperatures (160 and 180 °C) on the composition of the preponderant fish phospholipid classes, phosphatidylethanolamine (PE) and phosphatidylcholine (PC), were investigated on Sardina pilchardus. The total fish lipid fraction was injected into the HPLC system coupled on line with a second order mass spectrometer (MS–MS) by means of electronebulization interface (ESI), without a prior clean-up of the phospholipid fraction.The deep-fat frying process caused significant changes on PE and PC molecular species composition of the fish fillet.In all cases, the deep-fat frying process caused a significant (P < 0.05) increase in the relative proportions of the PE and PC species constituted by the combination of palmitic and docosahexaenoic acids. At the same time, a depletion of the percentage of the PE and PC species formed by two docosahexaenoic acid residues in fried fillets was registered. Anyway, this depletion was statistically significant for PC, but not for PE.Both PE and PC compositions were not influenced by the frying temperature, whereas the nature of the culinary fat had an effect on the PC composition. Particularly, the frying tests with conventional sunflower oil produced a statistically significant increase of PC species containing saturated/polyunsaturated fatty acids and a significant decrease of PC species formed by the combination of two polyunsaturated fatty acids.     

Tocopherol Content and Fatty Acid Distribution of Peas (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

The positional distribution of fatty acids (FA) of triacylglycerols (TAG) and major phospholipids (PL) prepared from four cultivars of peas (Pisum sativum L.) were investigated as well as their tocopherol contents. The lipids extracted from these peas were separated by thin-layer chromatography (TLC) into seven fractions. The major lipid components were PL (52.2–61.3%) and TAG (31.2–40.3%), while the other components were also present in minor proportions (5.6–9.2%). γ-Tocopherol was present in the highest concentration, and α- and δ-tocopherols were very small amounts. The main PL components isolated from the four cultivars were phosphatidylcholine (42.3–49.2%), followed by phosphatidylinositol (23.3–25.2%) and then phosphatidylethanolamine (17.7–20.5%). Small but significant differences (P < 0.05) in FA distribution existed when different pea cultivars were determined. However, the principal characteristics of the FA distribution in the TAG and the three PL were evident among the four cultivars; unsaturated FA were predominantly located in the sn-2 position, and saturated FA primary occupied the sn-1 or sn-3 position in the oils of the peas. These results suggest that the regional distribution of tocopherols and fatty acids in peas is not dependent on the climatic conditions and the soil characteristics of the cultivation areas during the growing season.     

Seasonal Variations of Lipid Content and Composition in <Emphasis Type="Italic">Perna viridis</Emphasis>

The total lipid content, composition of main lipid classes, composition of sterols and composition of fatty acids in the main glycerolipids of Perna viridis were analyzed through four seasons using TLC-FID and GLC. Mussel samples were collected during different seasons between 2003 and 2004 from Shengsi Island, Zhejiang Province, China and stored frozen prior to freeze-drying and lipid extraction. Ten grams of dried mussel powder of each season were analyzed. Total lipid content ranged from 14.5 g/100 g in spring month to 7.8 g/100 g dried mussel powder in autumn month. The predominant lipid in spring month was triacylglycerol (TAG), however, in the other three seasons the phospholipids (PL) was the main lipid class. The most abundant fatty acid in TAG, PL and phosphatidylcholine (PC) was 16:0, with the summer samples having the highest proportion (24-30% of total fatty acid) and winter the lowest (14-22%). In phosphatidylethanolamine (PE), the spring samples had the highest proportions of 16:0. The predominant polyunsaturated fatty acids (PUFA) were 22:6n-3 and 20:5n-3 in TAG, PL, PE and PC (25-40%). The proportions of 22:6n-3 and 20:5n-3 were higher in spring than in other seasons in PL and PE. There were nine sterols identified, with cholesterol being the predominant sterol, and other main ones were desmostersol/brassicasterol and 24-methylenecholesterol. Proportions of other fatty acids in different lipid fractions and the sterol compositions as well also varied seasonally. There were subject to the seasonal variations. Differences in lipid content and composition, fatty acid composition in different lipid fractions may be caused by multiple factors such as lifecycle, sex, variation of plankton in different seasons and temperature, which could influence physiological activities and metabolism.     

A Simple Enzymatic Approach for Selective Acetylation of Phosphatidylethanolamine

Acetylation of lecithin improves the fluid properties, water dispersibility and emulsifying properties of a variety of food formulations. Acetylation of lecithin is usually carried out chemically using acetic anhydride in the presence of tertiary amine. In the present study acetylation of soybean lecithin and egg yolk lecithin was carried out using lipozyme IM 20 having 1,3-specificity from Mucor miehei and vinyl acetate at 70–75 °C. Vinyl acetate played a dual role as acetylating agent and also as the solvent medium. This method selectively acetylated phosphatidylethanolamine without effecting phosphatidylinositol since the enzyme employed was 1,3-specific.     

Indene Compounds Synthetically Derived from Vitamin D Have Selective Antibacterial Action on Helicobacter pylori

Helicobacter pylori infects the human stomach and is closely linked with the development of gastric cancer. When detected, this pathogen can be eradicated from the human stomach using wide‐spectrum antibiotics. However, year by year, H. pylori strains resistant to the antibacterial action of antibiotics have been increasing. The development of new antibacterial substances effective against drug‐resistant H. pylori is urgently required. Our group has recently identified extremely selective bactericidal effects against H. pylori in (1R,3aR,7aR)‐1‐[(1R)‐1,5‐dimethylhexyl]octahydro‐7a‐methyl‐4H‐inden‐4‐one (VDP1) (otherwise known as Grundmann's ketone), an indene compound derived from the decomposition of vitamin D₃ and proposed the antibacterial mechanism whereby VDP1 induces the bacteriolysis by interacting at least with PtdEtn (dimyristoyl‐phosphatidylethanolamine [di‐14:0 PtdEtn]) retaining two 14:0 fatty acids of the membrane lipid constituents. In this study, we synthesized new indene compounds ((1R,3aR,7aR)‐1‐((2R,E)‐5,6‐dimethylhept‐3‐en‐2‐yl)‐7a‐methyloctahydro‐4H‐inden‐4‐one [VD2‐1], (1R,3aR,7aR)‐1‐((S)‐1‐hydroxypropan‐2‐yl)‐7a‐methyloctahydro‐1H‐inden‐4‐ol [VD2‐2], and (1R,3aR,7aR)‐7a‐methyl‐1‐((R)‐6‐methylheptan‐2‐yl)octahydro‐1H‐inden‐4‐ol [VD3‐1]) using either vitamin D₂ or vitamin D₃ as materials. VD2‐1 and VD3‐1 selectively disrupted the di‐14:0 PtdEtn vesicles without destructing the vesicles of PtdEtn (dipalmitoyl‐phosphatidylethanolamine) retaining two 16:0 fatty acids. In contrast, VD2‐2, an indene compound lacking an alkyl group, had no influence on the structural stability of both PtdEtn vesicles. In addition, VD2‐1 and VD3‐1 exerted extremely selective bactericidal action against H. pylori without affecting the viability of commonplace bacteria. Meanwhile, VD2‐2 almost forfeited the bactericidal effects on H. pylori. These results suggest that the alkyl group of the indene compounds has a crucial conformation to interact with di‐14:0 PtdEtn of H. pylori membrane lipid constituents whereby the bacteriolysis is ultimately induced.     

Plasma Phosphatidylethanolamine and Triacylglycerol Fatty Acid Concentrations are Altered in Major Depressive Disorder Patients with Seasonal Pattern

Disturbances in peripheral and brain lipid metabolism, including the omega-3 fatty acid docosahexaenoic acid (DHA), have been reported in major depressive disorder (MDD). However, these changes have yet to be confirmed in MDD with seasonal pattern (MDD-s), a subtype of recurrent MDD. The present exploratory study quantified plasma plasmalogen and diacyl-phospholipid species, and fatty acids within total phospholipids, cholesteryl esters, triacylglycerols and free fatty acids in non-medicated MDD-s participants (n = 9) during euthymia in summer or fall, and during depression in winter in order to screen for potential high sensitivity lipid biomarkers. Triacylglycerol alpha-linolenic acid concentration was significantly decreased, and myristoleic acid concentration was significantly increased, during winter depression compared to summer-fall euthymia. 1-stearyl-2-docosahexaenoyl-sn-glycero-3-phosphoethanolamine, a diacyl-phospholipid containing stearic acid and DHA, was significantly decreased in winter depression. Concentrations of cholesteryl ester oleic acid and several polyunsaturated fatty acids between summer/fall and winter increased in proportion to the increase in depressive symptoms. The observed changes in lipid metabolic pathways in winter-type MDD-s offer new promise for lipid biomarker development.     

Regiospecific distribution of fatty acids in triacylglycerols and phospholipids from broad beans (Vicia faba)

Regiospecific distributions of fatty acids of triacylglycerols (TAG) and phospholipids (PL) separated from broad beans (Vicia faba) of four cultivars (Minpo, Sanuki, Nintoku and Sanren) were investigated. The major lipid components were PL (47.5–50.5 wt‐%) and TAG (47.7–50.1 wt‐%), while steryl esters, hydrocarbons, free fatty acids, diacylglycerols and monoacylglycerols were present in minor proportions (1.6–2.4 wt‐%). The PL components isolated from the four cultivars were phosphatidylcholine (56.4–58.4 wt‐%), phosphatidylethanolamine (20.3–21.7 wt‐%) and phosphatidylinositol (16.6–18.6 wt‐%). Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among these PL. The principal characteristics of the fatty acid distribution in the TAG and PL were evident in the beans: Unsaturated fatty acids were predominantly concentrated in the sn‐2 position while saturated fatty acids primarily occupied the sn‐1 or sn‐3 position in these lipids. The lipid components and fatty acid distributions were almost the same in the four cultivars and were not influenced by genetic variability and planting location. These results could be useful information to both consumers and producers for the manufacture of traditional broad bean foods in Japan.     

An Improved High-Throughput Lipid Extraction Method for the Analysis of Human Brain Lipids

We have developed a protocol suitable for high-throughput lipidomic analysis of human brain samples. The traditional Folch extraction (using chloroform and glass–glass homogenization) was compared to a high-throughput method combining methyl-tert-butyl ether (MTBE) extraction with mechanical homogenization utilizing ceramic beads. This high-throughput method significantly reduced sample handling time and increased efficiency compared to glass–glass homogenizing. Furthermore, replacing chloroform with MTBE is safer (less carcinogenic/toxic), with lipids dissolving in the upper phase, allowing for easier pipetting and the potential for automation (i.e., robotics). Both methods were applied to the analysis of human occipital cortex. Lipid species (including ceramides, sphingomyelins, choline glycerophospholipids, ethanolamine glycerophospholipids and phosphatidylserines) were analyzed via electrospray ionization mass spectrometry and sterol species were analyzed using gas chromatography mass spectrometry. No differences in lipid species composition were evident when the lipid extraction protocols were compared, indicating that MTBE extraction with mechanical bead homogenization provides an improved method for the lipidomic profiling of human brain tissue.