Isomerization Of Polyunsaturated Fatty Acids Research Articles

Geometrical isomerization of arachidonic acid during lipid peroxidation interferes with ferroptosis.

Geometrical mono-trans isomers of arachidonic acid (mtAA) are endogenous products of free radical-induced cis-trans double bond isomerization occurring to natural fatty acids during cell metabolism, including lipid peroxidation (LPO). Very little is known about the functional roles of mtAA and in general on the effects of mono-trans isomers of polyunsaturated fatty acids (mtPUFA) in various types of programmed cell death, including ferroptosis. Using HT1080 and MEF cell cultures, supplemented with 20μM PUFA (i.e., AA, EPA or DHA) and their mtPUFA congeners, ferroptosis occurred in the presence of RSL3 (a direct inhibitor of glutathione peroxidase 4) only with the PUFA in their natural cis configuration, whereas mtPUFA showed an anti-ferroptotic effect. By performing the fatty acid-based membrane lipidome analyses, substantial differences emerged in the membrane fatty acid remodeling of the two different cell fates. In particular, during ferroptosis mtPUFA formation and their incorporation, together with the enrichment of SFA, occurred. This opens new perspectives in the role of the membrane composition for a ferroptotic outcome. While pre-treatment with AA promoted cell death for treatment with H2O2 and RSL3, mtAA did not. Cell death by AA supplementation was suppressed also in the presence of either ferroptosis inhibitors, such as the lipophilic antioxidant ferrostatin-1, or NADPH oxidase (NOX) inhibitors, including diphenyleneiodonium chloride and apocynin. Our results confirm a more complex scenario for ferroptosis than actually believed. While LPO processes are active, the importance of environmental lipid levels, balance among SFA, MUFA and PUFA in lipid pools and formation of mtPUFA influence the membrane phospholipid turnover, with crucial effects in the occurrence of cell death by ferroptosis.

Bioavailability and Functionality of Conjugated Fatty Acids in Foods

Dietary conjugated fatty acids are associated with heart disease, obesity, diabetes, cancer and others; in addition, many functions of cell membranes are dependent on lipid composition and lipids ingested through the diet can modify this composition and their biochemical activity. Due to the discoveries of their chemical and physiological properties, there is a growing interest in conjugated fatty acids as well as in the properties of their isomers. Conjugated fatty acids (CFAs) are the general term to describe the positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds, which are separated by a single carbon-carbon bond rather than being separated by a methylene group (CH2). Theoretically, several isomers of conjugated fatty acids are possible, with multiple combinations of numerical, positional and geometric configurations of the conjugation of double bonds, which may present as conjugated linoleic and α-linolenic acids and may have different functionalities in the body.

Conjugated Fatty Acids in Muscle Food Products and Their Potential Health Benefits: A Review.

Conjugated fatty acids (CFAs) are a group of positional and geometric isomers of polyunsaturated fatty acids (PUFAs) with conjugated double bonds. There are several subgroups of CFAs including conjugated linoleic acids (CLAs), conjugated linolenic acids (CLNAs), conjugated eicosapentaenoic acids (CEPAs), and conjugated docosahexaenoic acids (CDHAs). CFAs, especially CLAs, have been studied in recent years both for their health benefits and factors that affect their level in muscle food products. CFAs have been reported in numerous studies as having antitumor, antiobesity, antidiabetes, anticardiovascular disease, and modulating immune system effects. These biological activies are involved in changes of lipid peroxidation and energy expenditure, as well as inhibitory effects on the hormone receptor, lipid metabolism, lipoprotein lipase activity, and adiponectin production. A large body of studies has revealed that the diet, processing, storage conditions, slaughter season, and age are common factors that affect CFA content in muscle food products, as detailed in this review. Recommendations are made regarding animal farming and meat product processing to obtain high CFA content meat products and to optimize the benefits of CFA for health promotion.

Enzymatic Study of Linoleic and Alpha-Linolenic Acids Biohydrogenation by Chloramphenicol-Treated Mixed Rumen Bacterial Species.

In the rumen, dietary polyunsaturated fatty acids (PUFA) are reduced by a multistage reaction called biohydrogenation (BH). BH leads to a high proportion of saturated fat in ruminant products, but also products some potential bioactive intermediates like conjugated linoleic and linolenic acids. BH is composed of two kinds of reactions: first an isomerization of PUFA followed by reductions (two for linoleic acid, C18:2n-6; three for α-linolenic acid, C18:3n-3). There is little knowledge about BH enzymes as BH bacterial species are the subject of a lot of studies. Nevertheless, both aspects must be explored to control BH and enhance the fatty acids profile of ruminant products. In the present study, an alternative approach was developed to study the enzymes produced in vivo by mixed ruminal bacteria, using inactivation of bacteria by chloramphenicol, an inhibitor of protein synthesis in prokaryotes, before in vitro incubation. To study C18:2n-6 and C18:3n-3 BH several experiments were used: (1) with different incubation durations (0 to 3) to estimate average rates and efficiencies of all BH reactions, and intermediates production; and (2) with different initial quantities of PUFA (0.25 to 2 mg) to estimate Michaelis–Menten enzymatic parameters, Km and Vmax. A last experiment explored the effect of pH buffer and donor cow diet on C18:2n-6 isomerization pathways. Concerning C18:2n-6 BH, this study confirmed the high saturability of its isomerization, the inhibition of both trans11 and trans10 pathways by a low pH, and the last reduction to stearic acid as the limiting-step. Concerning C18:3n-3, its BH was faster than C18:2n-6, in particular its isomerization (Vmax = 3.4 vs. 0.6 mM/h, respectively), and the limiting-step was the second reduction to t11-C18:1. Besides, our mixed isomerases had a higher affinity for C18:2n-6 than for C18:3n-3 (Km = 2.0 × 10-3 vs. 4.3 × 10-3 M, respectively), but due to their high saturability by C18:2n-6, they had a lower efficiency to isomerize C18:2n-6 than C18:3n-3. Chloramphenicol-treated ruminal fluid would be a meaningful method to study the BH enzymes activities.

Awesome Attributes of Pomegranate in Diet

Conjugated fatty acid, the general term of positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds, has attracted considerable attention because of its beneficial biological effects. In the present study, dietary effect of pomegranate seed oil rich in punicic acid (9cis, 11trans, 13cis-conjugated linolenic acid; 9c, 11t, 13c-CLNA) on lipid metabolism was investigated in obese, hyperlipidemic Male albino Wistar (MAWR) rats. After 4 weeks feeding period, MAWR rats revealed obesity and hyperlipidemia compared with their progenitor AELM rats. Feeding of the diet supplemented with 9% safflower oil and 1% pomegranate seed oil (9c, 11t, 13c-CLNA diet) did not affect abdominal white adipose tissue weights and serum lipid levels compared with the diet supplemented with 10% safflower oil (control diet) in MAWR rats. However, the accumulated hepatic triacylglycerol was markedly decreased by 9c, 11t, 13c-CLNA diet in MAWR rats. Activities of hepatic enzymes related to fatty acid synthesis and fatty acid β-oxidation were not altered by 9c, 11t, 13c-CLNA diet. Levels of monounsaturated fatty acid (MUFA), major storage form of fatty acid, in serum triacylglycerol were markedly higher in obese, hyperlipidemic MAWR rats than in lean LETO rats. In addition, 9c, 11t, 13c-CLNA diet significantly decreased MUFA levels in MAWR rats. This is the first study showing that 9c, 11t, 13c-CLNA suppresses delta-9 desaturation in vivo, and we suggest that the alleviation of hepatic triacylglycerol accumulation by 9c, 11t, 13c-CLNA diet was, at least in part, attributable to the suppression of delta-9 desaturation in MAWR rats.

Production of conjugated linoleic acid-rich cottonseed oil by supported Ru catalyzed isomerization

Supported metal (e.g. Ruthenium (Ru)) is capable to catalyze the isomerization of polyunsaturated fatty acids in plant oils into conjugated fatty acids. Conjugated linoleic acids (CLAs) produced from plant oils have not only been associated with diverse health and physiological effects, but also been interesting renewable compounds in producing industrial products such as paints, glues, and polymers, due to the presence of very reactive conjugated double bonds. To explore the industrial potential of heterogeneous supported metal catalyst in converting food-use limited cottonseed oil (CSO) into conjugated linoleic acid (CLA)-rich plant oil, Ru/C (J.M.), Ru/C (Sigma), Ru/Al2O3 and Ru black are examined for their catalytic efficiency/selectivity in decane and solvent-free systems. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) are employed for their surface chemical composition and morphology analyses. Deconvolution of Ru 3p and 3d spectra are executed by Gaussian and Lorentzian fitting; and a qualitative correlation between oxidation states of Ru and catalytic activity/selectivity of Ru catalysts are delineated. In 24h in solvent-free system Ru black is capable to achieve 51.3% conversion of linoleic acid (LA) in CSO with excellent selectivity (83.7%) towards CLA formation (CLA-rich CSO can be easily obtained by simple filtration); conversion of LA doesnot show any Sn-2/Sn-1,3 region-preference; however, the reaction activity/selectivity is pronouncedly correlated to the content of Ru (IV) in catalysts.

Sterolic Composition of Neutralized Oils Bleached with Clays Activated with Ultrasound

Clays are activated by a classic process and realized in relatively high temperatures. Increasing the clay surface acidity leads to the increase of the specific surfaces of clays with deeper destruction of their crystal lattice; with the training of amorphous silica. This later can cause many degradation reactions such as isomerization of polyunsaturated fatty acids, decomposition of unsaturated fatty acids and sterols, and to dehydration of sterols which leads to steradienes formation. With the aim to prepare bleaching earths with high efficiency, and having less negative effects, ultrasonic waves were introduced during activation process. The experimental conditions of this new activation process allowed the acid concentration and activation time to be considerably reduced. The influence of activated clays with ultrasound on physico-chemical properties of bleached oils, mainly on fatty acid composition, sterols, and steradienes was investigated. It was proved that these clays, activated with the new technique, led to the removal of unacceptable compounds with the least possible losses of oil and desirable fractions. The noticed losses in sterols were suggested to be strongly dependent on the influence of activation process, mainly on surface acidity of bleaching earths.

A Promising Raman Spectroscopy Technique for the Investigation of trans and cis Cholesteryl Ester Isomers in Biological Samples.

Lipid geometry is an important issue in biology and medicine. The cis-trans geometry conversion of double bonds in lipids is an endogenous process that can be mediated by sulfur-centered free radicals. Trans isomers of polyunsaturated fatty acids can be used as biological markers of free radical stress, and their presence in biological samples can be determined by synthesis and characterization of appropriate reference compounds. Fractions of plasma lipids, such as cholesteryl linoleate and arachidonate esters, are interesting targets because of their connection with membrane phospholipid turnover and their roles in cardiovascular health. In this context, Raman spectroscopy can provide a useful contribution, since Raman analysis can be performed directly on the lipid extracts without any derivatization reaction, is nondestructive, and can rapidly supply biochemical information. This study focused on the build up of Raman spectral libraries of different cis and trans isomers of cholesteryl esters to be used as references for the examination of complex biological samples and to facilitate isomer recognition. Unsaturated cholesteryl esters obtained by chemical synthesis and with different alkyl chain lengths, double bond numbers, or both, were analyzed. The potential of Raman analysis for trans isomer detection in biological samples was successfully tested on some cholesteryl ester lipid fractions from human serum. The data suggest promising applications of Raman spectroscopy in metabolomics and lipidomics.

A Quick, Optimized Method for Routine Analysis of Essential and Trans-Octadecenoic Acids in Edible Fats and Oils by GLC

A gas chromatography procedure using a 30-m capillary column (VF-23ms) has been optimized for quick analysis (run time less than 20 min). The method is suitable for routine analysis of the fatty acid composition of edible fat and oil samples (milk, fish, vegetal and synthetic origin). The results were comparable with those obtained with a 100-m-long CP-Sil 88 column (run times between 60 and more than 100 min) in the analysis of geometric and positional isomers of polyunsaturated fatty acids. The achieved resolution of compounds from 4 to 26 carbon atoms with 0-6 double bonds, as omega-3 and omega-6 fatty acids, major trans-octadecenoic isomers and conjugated linoleic acid isomers, was higher than those reported in other proposed and reference methods for similar samples using short-length columns. The response factors obtained from the fatty acid composition of reference milk fat exhibited high feasibility and the inter-assay (VF23ms versus CP-Sil 88) and intra-assays based on relative standard deviation showed good accuracy, because they were lower than 10%.

Chemical and physiological aspects of isomers of conjugated fatty acids

Conjugated fatty acid (CFA) is the general term to describe the positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds. The CFAs of linoleic acid (CLAs) are found naturally in foods derived from ruminant animals, meat, or dairy products. The CFAs of α-linolenic acid (CLNAs) are found exclusively in various types of seed oils of plants. There are many investigations to assess the effects to health from CFAs consumption, which have been associated with physiological processes that are involved with non transmissible chronic diseases such as cancer, atherosclerosis, inflammation, and obesity. Conclusive studies about the CFAs effects in the body are still scarce and further research about their participation in physiological processes are necessary. This review aimed to discuss the influence of conjugated fatty acids on physiological processes in animal organism.

Geometrical isomerization of polyunsaturated fatty acids in physically refined rapeseed oil during plant‐scale deodorization

AbstractThe effect of the operating temperature (between 220 and 270 °C) on the formation of trans isomers of linoleic and linolenic acids in physically refined rapeseed oil during deodorization in a plant‐scale semicontinuous tray‐type deodorizer (capacity 10 t/h) was investigated. The industrial procedures of physical refining consisted of a two‐step bleaching and deodorization process. The degree of isomerization of linoleic acid ranged from 0.33 to 4.77% and that of linolenic acid from 4.43 to 45.22% between 220 and 270 °C, respectively. A relation between the logarithm of the degree of isomerization and the deodorization temperature can be approximated by statistically highly significant linear functions for both linoleic and linolenic acids. Oleic acid was resistant to the heat‐induced geometrical isomerization. The values found for the ratio between the degrees of isomerization of linolenic and linoleic acids, slightly decreasing with increasing temperature, were equal to 13.6 and 12.9 at 230 and 240 °C, respectively. Two trans isomers of linoleic acid, exclusively with one double bond isomerized into trans configuration, and four trans isomers of linolenic acid, mostly with one double bond isomerized into trans configuration, were determined in deodorized rapeseed oils. Linolenic acid was observed to be the main source responsible for the formation of nearly all trans fatty acids in physically refined rapeseed oil. At 235 °C, a deodorization temperature considered as a reasonable technological compromise, the content of trans fatty acids in plant‐scale physically refined rapeseed oil was less than 1% of total fatty acids, which would be acceptable for further application.

Dietary effect of pomegranate seed oil rich in 9cis, 11trans, 13cis conjugated linolenic acid on lipid metabolism in obese, hyperlipidemic OLETF Rats

Conjugated fatty acid, the general term of positional and geometric isomers of polyunsaturated fatty acids with conjugated double bonds, has attracted considerable attention because of its potentially beneficial biological effects. In the present study, dietary effect of pomegranate seed oil rich in punicic acid (9cis, 11trans, 13cis-conjugated linolenic acid; 9c, 11t, 13c-CLNA) on lipid metabolism was investigated in obese, hyperlipidemic Otsuka Long-Evans Tokushima Fatty (OLETF) rats. After 2 weeks feeding period, OLETF rats revealed obesity and hyperlipidemia compared with their progenitor LETO rats. Feeding of the diet supplemented with 9% safflower oil and 1% pomegranate seed oil (9c, 11t, 13c-CLNA diet) did not affect abdominal white adipose tissue weights and serum lipid levels compared with the diet supplemented with 10% safflower oil (control diet) in OLETF rats. However, the accumulated hepatic triacylglycerol was markedly decreased by 9c, 11t, 13c-CLNA diet in OLETF rats. Activities of hepatic enzymes related to fatty acid synthesis and fatty acid β-oxidation were not altered by 9c, 11t, 13c-CLNA diet. Levels of monounsaturated fatty acid (MUFA), major storage form of fatty acid, in serum triacylglycerol were markedly higher in obese, hyperlipidemic OLETF rats than in lean LETO rats. In addition, 9c, 11t, 13c-CLNA diet significantly decreased MUFA levels in OLETF rats. This is the first study showing that 9c, 11t, 13c-CLNA suppresses delta-9 desaturation in vivo, and we suggest that the alleviation of hepatic triacylglycerol accumulation by 9c, 11t, 13c-CLNA diet was, at least in part, attributable to the suppression of delta-9 desaturation in OLETF rats.

In Vitro Versus in Situ Ruminal Biohydrogenation of Unsaturated Fatty Acids from a Raw or Extruded Mixture of Ground Canola Seed/Canola Meal

Raw or extruded blends of ground canola seeds and canola meal were used to compare in vitro and in situ lag times and rates of disappearance due to ruminal biohydrogenation of unsaturated fatty acids. The in situ study resulted in higher lag times for biohydrogenation for polyunsaturated fatty acids and lower rates of biohydrogenation of unsaturated fatty acids than the in vitro study, so the in situ biohydrogenation of polyunsaturated fatty acids was not complete at 24h of incubation. With both methods, rates of biohydrogenation of polyunsaturated fatty acids were higher than for cis-▵9C18:1. Extrusion did not affect the rate of biohydrogenation of cis-▵9C18:1, but resulted in higher rates of biohydrogenation of polyunsaturated fatty acids with higher proportions of trans intermediates of biohydrogenation at 4h of incubation in vitro and at 8h of incubation in situ. These results suggest that extrusion affects the isomerization of polyunsaturated fatty acids, rather than the hydrogenation steps. In conclusion, in vitro and in situ methods can both show differences of ruminal metabolism of unsaturated fatty acids due to processing, but the methods provide very different estimates of the rates of disappearance due to biohydrogenation.

Deodorization of vegetable oils: Prediction of trans polyunsaturated fatty acid content

AbstractKinetics of the formation of trans linoleic acid and trans linolenic acid were compared. Pilot plant‐scale tests on canola oils were carried out to validate the laboratory‐scale kinetic model of geometrical isomerization of polyunsaturated fatty acids described in our earlier publication. The reliability of the model was confirmed by statistical calculations. Formation of the individual trans linoleic and linolenic acids was studied, as well as the effect of the degree of isomerization on the distribution of the trans fatty acid isomers. Oil samples were deodorized at temperatures from 204 to 230°C from 2 to 86 h. Results showed an increase in the relative percentage of isomerized linolenic and linoleic acid with an increase in either the deodorization time or the temperature. The percentage of trans linoleic acid (compared to the total) after deodorization ranged from <1 to nearly 6%, whereas the percentage of trans linolenic acid ranged from <1 to >65%. Applying this model, the researchers determined the conditions required to produce a specially isomerized oil for a nutritional study. The practical applications of these trials are as follows: (i) the trans fatty acid level of refined oils can be predicted for given deodorization conditions, (ii) the conditions to meet increasingly strict consumer demands concerning the trans isomer content can be calculated, and (iii) the deodorizer design can be characterized by the deviation from the theoretical trans fatty acid content of the deodorized oil.

Thiyl radical induced isomerization of unsaturated fatty acids: determination of equilibrium constants

Thiyl radical-induced isomerization of polyunsaturated fatty acids (PUFAs) have been studied in homogeneous solution and in liposomes. Four one-trans isomers of arachidonic acid have been assigned with the help of 13C NMR spectroscopy. At a dose of 132 Gy, the trans fraction amounts to 9.2 ± 1.2% in each of the four isomers. Therefore, all the four double bonds are equally susceptible to isomerization, which can be achieved by means of gamma radiolysis or chemolysis (AAPH) using both lipophilic and hydrophilic thiols. The equilibrium is characterised by a cis/trans ratio of 19 : 81, far away from the composition of the natural fatty acids (cis fraction 100%). However, compared to the linoleate isomerization in the homogeneous solution, we observed a preferential formation of trans-trans isomers if linoleate is incorporated in the bilayer of liposomes. This difference might be explained by the better fitting of the all-trans isomer into the parallel-aligned acyl chains. The isomerization step takes place within an adduct of the thiyl radical to an olefinic bond. Using a competition method, the numerical value of the equilibrium constant for the adduct formation was determined by pulse radiolysis to be (15 ± 5) dm3 mol-1. This value does not depend on the number of double bonds and holds for all fatty acids under investigation.

Physical refining of edible oils

Crude oils obtained by oilseed processing have to be refined before the consumption in order to remove undesirable accompanying substances. The traditional alkali refining is often replaced by physical refining in which the use of chemicals is reduced. The most widely used method is steam refining. The crude oil quality is very important in order to obtain high quality refined oil. Furthermore, the oil should be efficiently degummed to remove phospholipids as well as heavy metals and bleached to remove pigments. The most important step consists of the application of superheated steam under low pressure and at temperatures higher than 220 °C. Both free fatty acids and objectionable volatiles, formed by cleavage of lipid oxidation products, are removed. A disadvantage is the partial loss of tocopherols. Side reactions, particularly isomerization of polyunsaturated fatty acids, should be minimized. The quality of physically refined oil is close to that of alkali refined oils, but losses of neutral oil are lower and the environment is less polluted. Among other methods of physical refining the application of selective membranes is promising.

Deodorization of vegetable oils. Part I: Modelling the geometrical isomerization of polyunsaturated fatty acids

AbstractLaboratory‐scale treatments of canola oils similar to deodorization were carried out by applying the following conditions: reduced pressure with nitrogen or steam stripping at different temperatures ranging from 210 to 270°C for 2–65 h. The formation of the group of trans linolenic acid isomers follows a first‐order reaction and the kinetic constant varies according to the Arrhenius’ law. Similar results were observed for the trans isomerization of linoleic acid. Based on these experiments, a mathematical model was developed to describe the isomerization reaction steps occurring in linoleic and linolenic acids during deodorization. The calculated degrees of isomerization are independent of the composition of the oil but related to both time and temperature of deodorization. The degree of isomerization of linolenic acid is unaffected by the decrease of this acid content observed during the deodorization. Deodorization at about 220–230°C appears to be a critical limit beyond which the linolenic isomerization increases very strongly. The newly established model can be a tool for manufacturers to reduce the total trans isomer content of refined oils, and was applied to produce a special selectively isomerized oil for a European Nutritional Project.

Abomasal Infusion of Cis or Trans Fatty Acid Isomers and Energy Metabolism of Lactating Dairy Cows1,2,3

Diets for dairy cows that provide or induce formation of trans isomers of polyunsaturated fatty acids result in reduced percentages of milk fat. The effect of abomasal infusion of trans-C18:1 fatty acid isomers on energy utilization by mature cows was determined. Six multiparous Holstein cows in midlactation had ad libitum access to a basal diet containing 50% forage and 50% concentrate. Treatments were 1) no infusion, 2) infusion of 630 g/d of a fat mixture high in cis-C18:1 isomers (64% cis-C18:1 68% high oleic sunflower oil and 32% cocoa butter), and 3) infusion of 623 g/d of a fat mixture high in trans-C18:1 isomers (42% trans-C18:1 90% partially hydrogenate soybean oil and 10% high linoleic safflower oil). The experiment was a replicated 3 x 3 Latin square design with 4-wk periods. Measurements of energy balance were made in open circuit respiration chambers during wk 4 of each period. Fat infusion increased milk production by 2.5 kg/d; apparent digestibility of DM, OM, energy, ADF, and ash by 1 to 4 percentage units; metabolizable energy by 11%; and NEL of the diet by 15%. Milk fat percentage and yield were higher when cows were infused with cis-C18:1 than when they were infused with trans-C18:1 (4.12% and 1.41 kg/d vs. 3.15% and 1.06 kg/d, respectively). Infusion of fat increased milk production, but trans-C18:1 reduced milk fat and energy output.

EFFECTS OF DIETARY 18:3 N‐3 TRANS ISOMERS ON THE Δ6 DESATURATION OF α‐LINOLENIC ACID

ABSTRACT Trans isomers of polyunsaturated fatty acids (PUFA) are formed during heat treatment of oils. In the present work, the effect of dietary geometrical isomers of α‐linolenic acid (18:3 n‐3) on the Δ6 desaturation of all cis 18:3 n‐3 was investigated, using rat liver microsomes. The desaturation rates were higher in microsomes from animals fed a cis n‐3 deficient diet, as compared to those from the control group or those from rats fed 18:3 n‐3 and its trans isomers. These data and the incorporation of long chain trans PUFA in microsomal lipids suggest that geometrical isomers of 18:3 n‐3 are probably slowly desaturated and elongated into long chain trans polyunsaturated fatty acids compared to 18:3 n‐3.

Differentiation of monoepoxide isomers of polyunsaturated fatty acids and fatty acid esters by low-energy charge exchange mass spectrometry

Differentiation of monoepoxide isomers of polyunsaturated fatty acids and fatty acid esters by low-energy charge exchange mass spectrometry