The sn-position of FA in membrane lipids has an influence on the physiological function of cells, is predictive for diseases, and therefore is useful for diagnostics. The current study compares the compositions of acyl chain substituents in the sn-1 and sn-2 positions of the glycerol backbones of phospholipids derived from human erythrocytes by using RP-HPLC coupled with on-line electrospray ionization ion trap MS. Preferential loss of the acyl group in the sn-1 position was used to determine the degree of regiospecific preference exhibited by the phospholipid molecules. The identities of the molecular species and the positions of the acyl substituents were identified using product-ion spectra of major precursor ions selected from the mass spectra averaged across peaks in the total ion chromatogram. Saturated FA were found to be located mainly in the sn-1 position of the glycerol backbones of erythrocyte phospholipids, whereas PUFA were found primarily in the sn-2 position. All measured phospholipids revealed palmitic acid (16:0) at the sn-1 position. Linoleic acid (18:2n-6) and arachidonic acid (20:4n-6) were found to be attached exclusively to the sn-2 position of the backbone, whereas eicosadienoic (20:2n-6) and eicosatrienoic acid (20:3n-9) occurred in both positions of the backbone of PC. Oleic (18:1n-9), linoleic (18:2n-6), and octadecatrienoic (18:3) acids of PE and PS were linked to both positions. Lignoceric acid (24:1 n-9) was found to be strictly localized at the sn-2 position, whereas nervonic (24:1n-9) acid of PS was associated with both positions of the backbone. A detailed analysis of the blood cell membrane lipids by MS might be helpful to characterize postprandial kinetics of pharmacological or dietary lipid applications, as well as environmental influences on cell membranes.
A reliable HPLC method was established to evaluate the lipid composition of useful plants modified by breeding techniques. This study focused on the polar lipid distribution and polar lipid FA compositions of four rapeseed varieties. Structure and quantity of the distinct lipid classes were compared by HPLC using ELSD followed by a GC FA analysis. A baseline separation of 14 lipid classes could be achieved within one step by using an eluent gradient of hexane, tert-methylbutyl ether, isopropanol, acetonitrile, chloroform, triethylamine, acetic acid, and water supplemented with ammonium sulfate with a polyvinyl alcohol column. After automatic fractionation, the FA compositions of the distinct lipid classes were characterized by a subsequent complementary GC FA analysis through direct acetylchloride methylation. The rape varieties analyzed showed diversity in polar lipid content and distribution, dominated by PC, PE, PI, monoglycosyldiacylglycerols, and phytosterols. Extensive variations were detected in FA within the lipid classes of rape varieties with predominantly oleic acid, linoleic acid, and α-linolenic acid observed followed by palmitic acid and gondoic acid. Oleic acid was mainly connected to PC and linoleic acid to PE, whereas α-linolenic acid and γ-linolenic acid were predominantly linked to PI in all varieties.The effort to refine vegetable sources for dietary, cosmetic, or technical applications often requires compositional modification of plant constituents. Many of those modifications refer to the FA composition of vegetable oil sources. One of the most common sources for traditional and modified vegetable oils is the rape plant (Brassica sp.). In Central Europe both Brassica napus L. and B. rapa L. are grown extensively and have even become two of the most important oilseeds worldwide. Several studies have been conducted to alter the pattern of protein and fat metabolism of seed oil from B. napus L. by traditional breeding techniques as well as by genetic modifications such as antisense expression (1,2) and gene transformation (3-6). The originally dark yellow oil of the unmodified rapeseed is dominated by erucic acid glycerides (22:1n-9), followed by oleic acid (18:1n-9) and linoleic acid (18:2n-6) (7). However, erucic acid and seed glucosinolates can cause adverse health effects and negatively affect the taste of this vegetable oil for dietary use. Therefore, both plant components have been eliminated by conventional plant breeding techniques to create dietary rapeseed oil, which is low in erucic acid (0-Rape) as well as seed glucosinolates (00-Rape). The substances have been replaced by oleic acid and linoleic acid (7). These new oil varieties are now mainly used as edible vegetable oils and as raw material for margarine formulations. In addition to the nutritive value of the oil as a caloric source, other possible applications of lipids and FA are attractive. Those alternative applications are basically related to the molecular structure of the polar lipids, because polar lipids and their physio...
Many different analytical procedures for fatty acid analysis of infant formulae and human milk are described. The objective was to study possible pitfalls in the use of different acid-catalyzed procedures compared to a base-catalyzed procedure based on sodium-methoxide in methanol. The influence of the different methods on the relative fatty acid composition (wt% of total fatty acids) and the total fatty acid recovery rate (expressed as % of total lipids) was studied in two experimental LCP-containing formulae and a human milk sample. MeOH/HCl-procedures were found to result in an incomplete transesterification of triglycerides, if an additional nonpolar solvent like toluene or hexane is not added and a water-free preparation is not guaranteed. In infant formulae the low transesterification of triglycerides (up to only 37%) could result in an 100%-overestimation of the relative amount of LCP, if these fatty acids primarily derive from phospholipids. This is the case in infant formulae containing egg lipids as raw materials. In formula containing fish oils and in human milk the efficacy of esterification results in incorrect absolute amounts of fatty acids, but has no remarkable effect on the relative fatty acid distribution. This is due to the fact that in these samples LCP are primarily bound to triglycerides. Furthermore, in formulae based on butterfat the derivatization procedure should be designed in such a way that losses of short-chain fatty acids due to evaporation steps can be avoided. The procedure based on sodium methoxide was found to result in a satisfactory (about 90%) conversion of formula lipids and a reliable content of all individual fatty acids. Due to a possibly high amount of free fatty acids in human milk, which are not methylated by sodium-methoxide, caution is expressed about the use of this reagent for fatty acid analysis of mothers milk. It is concluded that accurate fatty acid analysis of infant formulae and human milk requires a careful and quantitative derivatization of both polar and nonpolar lipid classes. Sodium methoxide seems to be a reliable and time-saving method for routine fatty acid analysis of infant formulae, which should be validated by interlaboratory comparison. Anhydrous procedures based on methanolic hydrogen chloride including an additional nonpolar solvent are also suitable for infant formulae but seem to be preferable for human milk samples.
The sn position of fatty acids in seed oil lipids affects physiological function in pharmaceutical and dietary applications. In this study the composition of acyl-chain substituents in the sn positions of glycerol backbones in triacylglycerols (TAG) have been compared. TAG from native and transgenic medium-chain fatty acid-enriched rape seed oil were analyzed by reversed-phase high performance liquid chromatography coupled with online atmospheric-pressure chemical ionization ion-trap mass spectrometry. The transformation of summer rape with thioesterase and 3-ketoacyl-[ACP]-synthase genes of Cuphea lanceolata led to increased expression of 1.5% (w/w) caprylic acid (8:0), 6.7% (w/w) capric acid (10:0), 0.9% (w/w) lauric acid (12:0), and 0.2% (w/w) myristic acid (14:0). In contrast, linoleic (18:2n6) and alpha-linolenic acid (18:3n3) levels decreased compared with the original seed oil. The TAG sn position distribution of fatty acids was also modified. The original oil included eleven unique TAG species whereas the transgenic oil contained sixty. Twenty species were common to both oils. The transgenic oil included trioctadecenoyl-glycerol (18:1/18:1/18:1) and trioctadecatrienoyl-glycerol (18:3/18:3/18:3) whereas the native oil included only the latter. The transgenic TAG were dominated by combinations of caprylic, capric, lauric, myrisitic, palmitic (16:0), stearic (18:0), oleic (18:1n9), linoleic, arachidic (20:0), behenic (22:0), and lignoceric acids (24:0), which accounted for 52% of the total fat. In the original TAG palmitic, stearic, oleic, and linoleic acids accounted for 50% of the total fat. Medium-chain triacylglycerols with capric and lauric acids combined with stearic, oleic, linoleic, alpha-linolenic, arachidic, and gondoic acids (20:1n9) accounted for 25% of the transgenic oil. The medium-chain fatty acids were mainly integrated into the sn-1/3 position combined with the essential linoleic and alpha-linolenic acids at the sn-2 position. Eight species contained caprylic, capric, and lauric acids in the sn-2 position. The appearance of new TAG in the transgenic oil illustrates the extensive effect of genetic modification on fat metabolism by transformed plants and offers interesting possibilities for improved enteral applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.