Potentially High Value Conjugated Linolenic Acids (CLnA) in Melon Seed Waste

Paternò-Büchi Reaction Mass Spectrometry Enables Positional Assignment of Polymethylene-Interrupted Double Bonds in Food-Derived Lipids

Fatty acids (FAs) containing polymethylene-interrupted (PMI) double bonds are a component of human foods; however, they present a significant analytical challenge for de novo identification. Covalent adduct chemical ionization and ozone-induced dissociation mass spectrometry (MS) methods enable unambiguous assignment of PMI-FA double bond positions, however, no method has been reported with electrospray ionization (ESI) platform using off-the-shelf systems. In the current work, we studied the Paternò-Büchi (PB) fragmentation patterns of PMI-FA and triacylglycerol (TG) by analyzing several known food sources. PB-MS/MS and MS3 enabled complete double bond location assignments, including the isolated double bond in PMI-FA and triacylglycerols. Sea urchin ("uni"), oyster, pine nut, and ginkgo nut were characterized for their signature PMI-FA, 20:2(5Z,11Z), 22:2(7Z, 15Z), 18:3(5Z,9Z,12Z), and 20:3(5Z,11Z,14Z), respectively. Quantitative analyses of the relative abundance of these PMI-FA led to results similar to reference methods. 18:3(5Z,9Z,12Z) was enriched at the sn-1/sn-3 position in pine nut major TG.

Fatty acid isomerism: analysis and selected biological functions

The biological functions of fatty acids and the lipids in which they are esterified are determined by their chain length, double bond position and geometry and other structural motifs such as the presence of methyl branches. Unusual isomeric features in fatty acids of human foods such as conjugated double bonds or chain branching found in dairy products, some seeds and nuts, and marine foods potentially have important effects on human health. Recent advancements in identifying fatty acids with unusual double bond positions and pinpointing the position of methyl branches have empowered the study of their biological functions. We present recent advances in fatty acid structural elucidation by mass spectrometry in comparison with the more traditional methods. The double bond position can be determined by purely instrumental methods, specifically solvent-mediated covalent adduct chemical ionization (SM-CACI) and ozone induced dissociation (OzID), with charge inversion methods showing promise. Prior derivatization using the Paternò-Büchi (PB) reaction to yield stable structures that, upon collisional activation, yield the double bond position has emerged. The chemical ionization (CI) based three ion monitoring (MRM) method has been developed to simultaneously identify and quantify low-level branched chain fatty acids (BCFAs), unattainable by electron ionization (EI) based methods. Accurate identification and quantification of unusual fatty acid isomers has led to research progress in the discovery of biomarkers for cancer, diabetes, nonalcoholic fatty liver disease (NAFLD) and atherosclerosis. Modulation of eicosanoids, weight loss and the health significance of BCFAs are also presented. This review clearly shows that the improvement of analytical capacity is critical in the study of fatty acid biological functions, and stronger coupling of the methods discussed here with fatty acid mechanistic research is promising in generating more refined outcomes.

Jacaranda oil administration improves serum biomarkers and bioavailability of bioactive conjugated fatty acids, and alters fatty acid profile of mice tissues

Jacaric acid, a conjugated linolenic acid (CLNA) present in jacaranda oil (JO), is considered a potent anticarcinogenic agent. Several studies have focused on its biological effects, but the metabolism once consumed is not clear yet. The aim of this work was to evaluate the effects of two different daily doses of JO on serum parameters and fatty acid (FA) profile of mice tissues after 4 weeks of feeding. No significant changes on body weight gain, food intake, or tissue weight were determined after 0.7 or 2 ml/kg of JO supplementation compared to control animals. Significantly lower blood low-density lipoproteins-cholesterol (20 mg/dl) and glucose (~147-148 mg/dl) levels were detected in both oil-treated groups compared to control (31.2 and 165 mg/dl, respectively). Moreover, jacaric acid was partially converted into cis9, trans11 conjugated linoleic acid (CLA) and thus further incorporated into tissues. Liver evidenced the highest total conjugated fatty acid content (1.1%-2.2%), followed by epididymal (0.7%-1.9%) and mesenteric (1.4%-1.8%) fat. Lower saturated and higher unsaturated fatty acid content was detected in both oil-treated groups compared to control. Our results support the safety of JO and its potential application with a functional or nutraceutical propose, by increasing human CLNA consumption and further availability of CLA.

Toward Quantitative Sequencing of Deuteration of Unsaturated Hydrocarbon Chains in Fatty Acids

No general method currently is available for the quantitative determination of deuterium (D) at C positions along a hydrocarbon chain. Bis-allylic deuterated highly unsaturated fatty acids (D-HUFA) are a novel class of drugs stabilized against H-abstraction-mediated oxidation by deuteration at the most labile positions. Ru-based catalytic deuteration overcomes the limited scale of bis-allylic D-HUFA production by total organic synthesis; however, it produces a complex mixture of bis-allylic D isotopologues and isotopomers, requiring detailed sequencing for characterization. We report here adaptation and application of the Paternó-Büchi (PB) reaction of 2-acetylpyridine to a series of D-HUFA with analysis by shotgun lipidomics to determine position-specific quantitative D abundances. Sodiated ^PBD-HUFA result in diagnostic ions of high abundance upon collision-induced dissociation (CID) activation, enabling sensitive differentiation and quantification of D fraction at each bis- and mono-allylic position for each isotopologue. Catalytically deuterated isotopologues D5-7 linolenic acid (D5-7 LnA), D6-8 arachidonic acid (D6-8 ARA), D7-9 eicosapentaenoic acid (D7-9 EPA), and D9-11 docosahexaenoic acid (D9-11 DHA) incorporate 80-98, 95-100, 81-100, and 83-100% D at their bis-allylic positions, respectively. D-HUFA isotopologues having D number greater than or equal to bis-allylic sites (e.g., D10-DHA or D11-DHA) deuterated >95% at bis-allylic positions, except for D-LnA. The mono-allylic position near the methyl end deuterates to a much greater extent than the mono-allylic position near the carboxyl end, and both positions deuterate only when bis-allylic D is near-saturated. This method enables rapid, accurate characterization of position and isotopomer-specific D composition and enables sequencing along the chain.

GC Analysis of Seven Seed Oils Containing Conjugated Fatty Acids

The fatty acid compositions, including isomer compositions, of seven seed oils containing conjugated fatty acids (CFA) were determined. Seed oils were extracted using a modified Folch extraction, converted to fatty acid methyl esters, and analyzed by gas chromatography (GC) with mass spectrometry and flame ionization detection. The MS detector was operated in positive-ion chemical ionization mode using methane reagent gas. GC was performed using two columns providing different retention characteristics: a poly(ethylene glycol) column and a more polar biscyanopropyl column. The complimentary information provided by the two columns was crucial to peak identification in several cases. The major CFA species in the samples are well known but all contained lesser amounts of additional CFA that have not been widely reported. All samples contained multiple species of conjugated linolenic acid, and two samples also contained small amounts of conjugated linoleic acid. The seed oils of Jacaranda mimosifolia and Calendula officinalis were found to contain 8c,10t,12t-18:3, the natural occurrence of which has only been recently reported in some other samples. The seed oil of Impatiens balsamina has been reported to contain four conjugated 18:4 species, and we present evidence for a fifth conjugated 18:4 isomer.

Giblets and abdominal fat of pomegranate seed oil fed chickens as a source of bioactive fatty acids

The aim of present study was to determine whether chickens' (broilers Ross 308, n = 180, sex ratio 1:1) diet modification with different doses of grape or pomegranate seed oil will favourable change fatty acids and cholesterol content in selected giblets (liver and heart) or wastes (adipose tissue). It was also verify whether generated changes would make the giblets and wastes more valuable as dietary components or by-products for food industry. From 22 to 42 day of life, five diets were administered to chickens. Control grower diet (CON) contained 5% of soy oil, whereas in the experimental grower diets part of soy oil (1.5% or 2%) was replaced with specific amount of grape or pomegranate seed oil (GRAP 1.5; GRAP 2.0; POM 1.5; POM 2.0 respectively). Fatty acids and cholesterol content were determined with gas chromatography with flame-ionization detection. Pomegranate seed oil improved fatty acids profile more favourably than grape seed oil, which makes it a valuable additive in chickens' feeding. Abdominal fat of pomegranate seed oil supplemented chickens appeared to be the richest sources of rumenic acid and n3 polyunsaturated fatty acids, which allows to suggest its use in manufacturing of meat products to obtain foodstuffs rich in those essential nutrients. In principal component analysis (PCA), two principal components: PC1 and PC2, which were enough to explain 29.91% of variance of initial variables, allowed to a good separation of chickens fed with both doses of pomegranate seed oil from animals from control and grape seed oil fed groups. Because poultry addresses all nutritional, institutional and consumer requirements, enrichment of giblets in rumenic acid by pomegranate seed oil incorporation into chickens' diet may provide a valuable dietary source of bioactive fatty acids for consumers, especially of low-income countries.

Structure determination of conjugated linoleic and linolenic acids

Conjugated linoleic and linolenic acids (CLA and CLnA) can be found in dairy, ruminant meat and oilseeds, these types of unsaturated fatty acids consist of various positional and geometrical isomers, and have demonstrated health-promoting potential for human beings. Extensive reviews have reported the physiological effects of CLA, CLnA, while little is known regarding their isomer-specific effects. However, the isomers are difficult to identify, owing to (i) the similar retention time in common chromatographic methods; and (ii) the isomers are highly sensitive to high temperature, pH changes, and oxidation. The uncertainties in molecular structure have hindered investigations on the physiological effects of CLA and CLnA. Therefore, this review presents a summary of the currently available technologies for the structural determination of CLA and CLnA, including the presence confirmation, double bond position determination, and the potential stereo-isomer determination. Special focus has been projected to the novel techniques for structure determination of CLA and CLnA. Some possible future directions are also proposed.

Characterization and Semiquantitative Analysis of Novel Ultratrace C10-24 Monounsaturated Fatty Acid in Bovine Milkfat by Solvent-Mediated Covalent Adduct Chemical Ionization (CACI) MS/MS

The net action of ruminal bacteria and endogenous bovine enzymes are responsible for cow's milk having the most complex fatty acid profiles among common foods. About 40 monounsaturated fatty acids below 1.5% w/w are known. Analysis of trace and ultratrace fatty acids is a challenge to the highest resolution chromatography even with prior fractionation. We employ solvent-mediated covalent adduct chemical ionization (CACI) tandem mass spectrometry (MS/MS) to enable rapid, unambiguous identification of unsaturated fatty acid methyl esters (FAME) at high sensitivity. Fifty-four monounsaturated fatty acids (C_10-24) were completely characterized, with the discovery of 15 novel fatty acids including nine at ultratrace levels 10-100 ppm, g/10⁶ g fatty acids (lowest concentration 19:1n-6 (10 ± 11 ppm, w/w (0.001%, w/w))). Ultratrace monoenes were typically odd chain lengths and all analyzed in a single 20 min analysis. These data establish the abundance of 15 new monoene fatty acids in bovine milkfat and a strategy for rapid unambiguous analysis of ultratrace monounsaturated fatty acids.

Identification of Polymethylene-Interrupted Polyunsaturated Fatty Acids (PMI-PUFA) by Solvent-Mediated Covalent Adduct Chemical Ionization Triple Quadrupole Tandem Mass Spectrometry

Pine nuts and other edible gymnosperm seeds contain unusual, bioactive polymethylene-interrupted polyunsaturated fatty acids (PMI-PUFAs), a subset of nonmethylene-interrupted PUFA with (-CH₂-)_n≥2 intervening between double bonds. Conventional methods for structure elucidation of PMI-PUFAs require special derivatization risking rearrangement artifacts. Here we introduce a facile solvent-mediated (SM) covalent adduct chemical ionization (CACI) system modified with a triple quadrupole MS, which distinguishes PMI-PUFAs from their analogues in direct methyl ester form. The prominent Δ5 desaturated PMI-PUFAs exhibit characteristic fragmentation at C_6-7 to yield ω diagnostic ions and share their fragmentation pattern with normal methylene interrupted PUFAs for the α diagnostic ion. H^• transfer upon CID dissociation of PMI-PUFAs was found to be dependent on the relative position of isolated lone double bonds and cleavage points. Ginkgo and five species of pine nuts were characterized for their unique Δ5 fatty acid profile, without the need for chemical standards.