Characterization of volatile compounds and triacylglycerol profiles of nut oils using SPME‐GC‐MS and MALDI‐TOF‐MS

Several nut oil varieties mainly used as culinary and overall healthy food ingredients were subject of the present study. Headspace solid‐phase microextraction combined with gas chromatography‐mass spectrometry was employed in order to determine the qualitative composition of volatile compounds. Furthermore, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry was used in order to assess the profiles and relative composition of the prevalent triacylglycerols (TAG) within the oils. The headspace of the majority of oil samples was dominated by high contents of acetic acid (up to 42%) and hexanal (up to 32%). As nut oils are typically gained by cold‐pressing from previously roasted nuts, characteristic pyrazine derivatives as well as degradation products of long‐chain fatty acids were detected. TAG analysis of these oils revealed a quite homogeneous composition dominated by components of the C₅₂ and C₅₄ group composed mainly of oleic (18:1), linoleic (18:2), stearic (18:0) and palmitic (16:0) acid residues representing together between 65 and 95% of the investigated nut oils. The TAG profiles showed characteristic patterns which can be used as ‘fingerprints’ of the genuine oils. Nut oils exhibiting quite similar fatty acid composition (e.g. hazelnut, pistachio and beech oil) could be clearly discriminated based on TAG showing significant differences between the oils.     

Characterization of the biocide polyhexamethylene biguanide by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry

The biocide polyhexamethylene biguanide (PHMB) has been characterized by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS). Previously, no method has been able to provide a detailed structural characterization of PHMB. MALDI‐TOF MS was able to detect PHMB oligomers with n ≤ 6. Six different PHMB product types were identified, which possess combinations of amine, cyanoamine, guanidine, or cyanoguanidine end‐groups. Postsource decay (PSD) fragmentation was used to confirm the correct assignment of PHMB structure for the dominant PHMB molecular ion. MALDI‐TOF MS analysis of a ¹⁵N‐labeled PHMB confirmed the correct assignment of PHMB molecular ions, and also indicated the existence of a polymerization–depolymerization equilibrium during melt polymerization of the polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4928–4936, 2006     

Reversed‐Phase Liquid Chromatography–Quadrupole‐Time‐of‐Flight Mass Spectrometry for High‐Throughput Molecular Profiling of Sea Cucumber Cerebrosides

Usually, the chemical structures of cerebrosides in sea creatures are more complicated than those from terrestrial plants and animals. Very little is known about the method for high‐throughput molecular profiling of cerebrosides in sea cucumbers. In this study, cerebrosides from four species of edible sea cucumbers, specifically, Apostichopus japonicas, Thelenota ananas, Acaudina molpadioides and Bohadschia marmorata, were rapidly identified using reversed‐phase liquid chromatography–quadrupole‐time‐of‐flight mass spectrometry (RPLC‐QToF‐MS). [M + H]⁺ in positive electrospray ionization (ESI) mode were used to obtain the product ion spectra. The cerebroside molecules were selected according to the neutral loss fragments of 180 Da and then identified according to pairs of specific products of long‐chain bases (LCB) and their precursor ions. A typical predominant LCB was 2‐amino‐1,3‐dihydroxy‐4‐heptadecene (d17:1), which was acylated to form saturated and monounsaturated non‐hydroxy and monohydroxy fatty acids with 17–25 carbon atoms. Simultaneously, the occurrence of 2‐hydroxy‐tricosenoic acid (C23:1h) was characteristic of sea cucumber cerebrosides, whereas this molecule was rarely discovered in plants, mammals, or fungi. The profiles of LCB and fatty acids (FA) distribution might be related to the genera of sea cucumber. These data will be useful for identification of cerebrosides using RPLC‐QToF‐MS.     

Mono‐Estolide Synthesis from trans‐8‐Hydroxy‐Fatty Acids by Lipases in Solvent‐Free Media and Their Physical Properties

Pseudomonas aeruginosa 42A2 is known to produce two hydroxy‐fatty acids, 10(S)‐hydroxy‐8(E)‐octadecenoic and 7,10(S,S)‐dihydroxy‐8(E)‐octadecenoic acids, when cultivated in a mineral medium using oleic acid as a single carbon source. These compounds were purified, 91 and 96 % respectively, to produce two new families of estolides: trans‐8‐estolides and saturated estolides from the monohydroxylated monomer. trans‐8‐estolides were produced by three different lipases (Novozym 435, Lipozyme RM IM and Lipozyme TL IM) with reaction yields between 68.4 ± 2.1 and 94.7 ± 2.4 % in a solvent‐free medium at 80 °C in 168 h under vacuum. Novozym 435 was found to be the most efficient biocatalyst for both hydroxy‐fatty acids with reaction yields of 71.7 ± 2.3 and 94.7 ± 2.4 %, respectively. Moreover, saturated estolides were also produced from a saturated 10(S)‐hydroxy‐8(E)‐octadecenoic. These estolides were chemically and enzymatically synthesized with Novozym 435, under the previous described reaction conditions with yields of 60.7 ± 2.1 and 71.2 ± 2.3 % respectively. Finally, viscosity, glass transition temperature, decomposition temperatures and enthalpies were determined to characterize both types of estolides. Thermal applications for both types of polyesters were improved since glass transition temperatures were lowered and decomposition temperatures were increased, with respect to their corresponding substrates.     

Ultra‐Performance Liquid Chromatography‐Mass Spectrometry Analysis of Free and Esterified Oxygenated Derivatives from Docosahexaenoic Acid in Rat Brain

Docosahexaenoic acid (DHA), a prominent long‐chain fatty acid of the omega‐3 family, is present at high amount in brain tissues, especially in membrane phospholipids. This polyunsaturated fatty acid is the precursor of various oxygenated lipid mediators involved in diverse physiological and pathophysiological processes. Characterization of DHA‐oxygenated metabolites is therefore crucial for better understanding the biological roles of DHA. In this study, we identified and measured, by ultrahigh‐performance liquid chromatography coupled with tandem mass spectrometry, a number of oxygenated products derived from DHA in exsanguinated and nonexsanguinated brains. These metabolites were found both in free form and esterified in phospholipids. Interestingly, both (R)‐ and (S)‐monohydroxylated fatty acid stereoisomers were observed free and esterified in phospholipids. Monohydroxylated metabolites were the main derivatives; however, measurable amounts of dihydroxylated products such as protectin DX were detected. Moreover, exsanguination allowed discriminating brain oxygenated metabolites from those generated in blood. These results obtained in healthy rats allowed an overview on the brain oxygenated metabolism of DHA, which deserves further research in pathophysiological conditions, especially in neurodegenerative diseases.     

TPD‐TG‐MS Investigations of the Catalytic Conversion of Glycerol over MOx‐Al2O3‐PO4 Catalysts

The catalytic performance of bifunctional catalysts, MO_x‐Al₂O₃‐PO₄, that contain acidic centers and different transition metal oxide components were evaluated in the gas‐phase dehydration of glycerol using the TPD‐TG‐MS technique and a continuous flow reactor experiment. The initial catalytic activity and selectivity to acrolein and acetol significantly depends on the acidity and the type of transition metal oxide. The higher the total acidity, the higher the acrolein selectivity in the order W > Mo > Cu > V~ Fe ~Cr > Ce. On the other hand, Mn‐, Cr‐, and Fe‐containing catalysts favor the formation of products of oxidative C‐C cleavage. TPD‐TG‐MS investigations of catalysts loaded with glycerol are useful tools for fast‐screening of initial activities of catalysts in the gas‐phase dehydration of glycerol.     

On‐line LC‐NMR‐MS characterization of sesame oil extracts and assessment of their antioxidant activity

Sesame lignans were isolated by solvent extraction and subsequently purified by solvent crystallization from crude, unroasted sesame oil, and a sesame oil deodorizer distillate. In addition, an aliquot of the purified sesame oil extract was treated with camphorsulfonic acid to obtain a sesaminol‐enriched extract. The sesame lignan composition of the extracts was characterized by on‐line liquid chromatography nuclear magnetic resonance spectroscopy mass spectrometry coupling (LC‐NMR‐MS). The effect of the sesame oil extracts as well as pure sesame lignans and γ‐tocopherol on the oxidative stability of sunflower oil (lignan‐free) was studied by the Rancimat assay. The Rancimat assay revealed the following oxidative stability order: sesame oil extract < sesame oil deodorizer distillate < sunflower oil (no added sesame oil extracts) < sesamol < sesaminol‐enriched sesame oil extract. In addition, the radical‐scavenging capacity of these extracts was assessed by the Trolox® equivalent antioxidant capacity (TEAC) assay. The TEAC assay revealed a slightly different AOX activity order: sesamin < sesame oil extract < sesaminol‐enriched sesame oil extract < sesamol. In conclusion, the sesaminol‐enriched extract revealed strong antioxidant activity and is therefore suitable to increase the oxidative stability of edible oils high in polyunsaturated fatty acids.     

Effect of cationization reagents on the matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrum of Chinese gallotannins

In this study, Chinese gallotannins were characterized by MALDI‐TOF MS, and effects of cationization reagents on the quality of spectra were investigated. The trideca‐ and tetradeca‐galloyl glucoses were observed in Chinese gallotannins, which could not be detected in earlier studies. When Cs⁺ was used as the cationization reagent, Chinese gallotannins gave a relatively simple MALDI‐TOF spectrum, three series of quasimolecular ions [M + Cs]⁺, [M + 2Cs–H]⁺, and [M + 3Cs–2H]⁺ and a series of metastable ion peaks with minimum abundance were detected. Selection of Na⁺ as the cationization reagent, additional three series of ion peaks including two patterns from the fragmentation and complex 2M adducts [2M + Na]⁺ can be distinguished. In the case of no deionization or addition of cationization reagent to the analyte/matrix, naturally abundant Na⁺ and K⁺ as the cationization reagent, [M + Na]⁺ and [M + K]⁺ molecular ions both appeared in the complicated spectrum. Therefore, we conclude that cationization reagents affect the MALDI‐TOF MS spectrum of Chinese gallotannins significantly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Copper‐Catalyzed Coupling of (E)‐Bromostilbene with Phenols/Azole: ESI‐MS Detection of Intermediates by Using an Ionically‐Tagged Ligand

A system based on copper/1,10‐phenanthroline efficiently promotes the coupling between phenols or pyrazole with (E)‐bromostilbene. (E)‐1‐Aryloxy‐1,2‐diphenylethenes were obtained from the coupling with phenols in good to excellent yields (69–90%). The exception was the reaction involving a phenol containing an electron‐withdrawing cyano group that required a longer reaction time and gave only 49% yield. Kinetic studies indicated the participation of the vinyl halide in the rate‐determining step. Under the conditions employed, the activation of the vinyl halide via a radical pathway was discarded using a radical scavenger test. By using an ionically‐tagged 1,10‐phenanthroline derivative as the ligand, various copper‐based ions were detected through ESI(+)‐MS. These ions suggested that formation of the active species [phenCuOAr(HOAr)₂] precedes the vinyl halide activation.     

Occurrence of Hexacosapolyenoic Acids 26:7(n‐3), 26:6(n‐3), 26:6(n‐6) and 26:5(n‐3) in Deep‐Sea Brittle Stars from Near the Kuril Islands

Significant amounts of polyunsaturated fatty acids (PUFA) with a chain length of 26 carbon atoms were detected in lipids of five deep water species of Ophiuroidea besides common fatty acids with chain lengths between 14 and 24. By means of hydrogenation, GC–MS of the methyl esters, and 4,4‐dimethyloxazoline (DMOX) derivatives of these C26 acids were characterized as 5,8,11,14,17,20,23‐hexacosaheptaenoic [26:7(n‐3)]; 8,11,14,17,20,23‐hexacosahexaenoic [26:6(n‐3)]; 5,8,11,14,17,20‐ hexacosahexaenoic [26:6(n‐6)]; and 11,14,17,20,23‐hexacosapentaenoic [26:5(n‐3)]. Concentrations of these acids varied from 0.3 to 4.5 mol% of the total FA. In all the samples investigated, the main component of C26PUFA was hexacosaheptaenoic acid 26:7(n‐3). These C26PUFA are localized mainly in polar lipids. The presence of the possible biosynthesis precursors suggests that the C26PUFA are produced by the brittle stars, and are not accumulated from food sources. This finding can also explain the presence of small amounts of the 26:7(n‐3) acid detected earlier in flesh lipids of the roughscale sole Clidoderma asperrimum, which feeds on deep water brittle stars. We suggest a possible scheme of the biosynthesis of C26 PUFA.     

Lipid Oxidation and Degradation Products in Raw Materials: Low‐Fat Topical Skin‐Care Formulations

Topical skin formulations with a lipid content below 15% were stored for 6 months at 5, 20, or 40 °C or for 2 weeks at 50 °C in darkness or at 20 °C with exposure to light for 6 months. The volatile lipid‐oxidation compounds formed during this storage period were compared to those formed in the raw materials during 3 months of accelerated stability storage at 40 °C. The volatile compounds were collected by dynamic headspace and analyzed using gas chromatography–mass spectrometry. It was possible to link eight out of nine volatile compounds detected during storage of topical skin formulations to the raw materials. In addition, a possible link between the appearance of butane nitrile and the decomposition of an initiator used for polyacrylate crosspolymer‐6 production was observed. The polymer may originate from texture modifiers added to the topical skin formulation or from plastics used for packaging of topical skin formulations. Furthermore, six well‐known lipid‐oxidation and nonenzymatic browning products were suggested to originate from the two raw materials, tricaprylin/tricaprin and coconut oil.     

Analysis of triacylglycerols in refined edible oils by isocratic HPLC‐ESI‐MS

A simple, fast and reproducible reversed‐phase high performance liquid chromatography (HPLC) method coupled to electrospray ionization mass spectrometry (ESI‐MS) for the analysis of triacylglycerols (TAGs) species in the commercial edible oils has been developed. The TAGs species were separated using isocratic 18% isopropanol in methanol and a Phenomenex C18 column. The ESI‐MS conditions were optimized using flow injection analysis of standard TAG. Fifteen, fourteen, and sixteen TAGs were separated and identified in corn oil, rapeseed oil, and sunflower oil, respectively. The presence of intense protonated molecular (M + H⁺), ammonium (M + ${\rm NH}_{4}^{ + } $ ), and sodium (M + Na⁺) adducts ions and their respective diacylglycerols ions in the ESI‐MS spectra showed correct identification of TAGs. Some minor potassium adducts (M + K⁺) were also found. In addition, the identity of the fatty acid, position of each fatty acid, and the location of the double bond in the fatty acid moiety were explained. It was found that this isocratic method is useful for fast screening and identification of triacylglycerols in lipids.     

Synthesis and characterization of a novel acetylene‐ and maleimide‐terminated benzoxazine and its high‐performance thermosets

A novel acetylene‐ and maleimide‐terminated benzoxazine, 3‐(3‐ethynylphenyl)‐3,4‐dihydro‐2H‐6‐(N‐maleimido)‐1,3‐benzoxazine (MBZ‐apa), was successfully synthesized with N‐(4‐hydroxyphenyl)maleimide, paraformaldehyde, and 3‐aminophenylacetylene. The structure of the benzoxazine is confirmed by FTIR and ¹H‐NMR spectroscopies. MBZ‐apa is easily dissolved in common organic solvents. Differential scanning calorimetry (DSC) was used to study thermal cross‐linking behavior of MBZ‐apa. The DSC curve shows only a single exothermic peak due to the oxazine ring‐opening polymerization and the polymerization of the acetylene and maleimide groups occurring simultaneously in the same temperature range. Dynamic mechanical analyses (DMA) reveals that the novel polybenzoxazine exhibits high glass‐transition temperature (T_g) (ca. 348°C). The storage modulus arrives at 4.5 GPa in the range of room temperature to 330°C. The polybenzoxazine exhibits good thermal stability as evidenced by thermogravimetric analysis (TGA). Pyrolysis‐gas chromatography/mass spectrometry (Pyrolysis‐GC/MS) was employed to characterize the polybenzoxazine. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Accurate determination of hexanal in beef bouillons by headspace solid‐phase microextraction gas‐chromatography mass‐spectrometry

Lipid oxidation has great impact on the quality of food products through flavor and taste deterioration, reduction in nutritive value, and potential toxicity of the oxidized food components. Flavor and taste deterioration can be easily perceived and it represents one of the major causes of consumer complaints in the food industry. The deterioration of sensory properties is due to the decomposition products of hydroperoxides that easily isomerize and degrade into volatile compounds. Volatile products are responsible for flavor and taste deterioration. In this study, we present the development of the solid‐phase microextraction gas chromatography‐mass spectrometry (SPME‐GC‐MS) technique to quantify low amounts (μg/g range) of secondary oxidation products, i.e. hexanal. The optimization of SPME parameters is a difficult task because of the possibility of further formation of volatile products during analysis. Different parameters such as type of fiber, exposure time of the fiber to the sample headspace and the optimal temperature of absorption have also been investigated. The complete validation of the method was achieved by the determination of linearity, limits of detection and quantification and repeatability. We demonstrated that the SPME method is a valuable tool for the quantification of low amounts of secondary oxidation products such as hexanal. Therefore, this technique can be used to detect early formation of volatiles.     

Pyrolysis GC‐MS of chlorinated natural rubber

High‐resolution pyrolysis gas chromatography‐mass spectrometry (HRPyGC‐MS) and Fourier transform infrared spectrometry (FTIR) were used to study the structures of the chlorinated natural rubbers (CNR) prepared by two different processes. The results indicate that the fine structures of CNR prepared from “latex” and “solution” processes are different, whereas their basic structures are similar. The molecule of CNR from the “latex” process contains a few carboxyl and carbonyl groups. The rings on CNR molecular chains should be hexatomic rings. The optimum pyrolytic temperature for CNR is 445°C, with an available range from 386 to 590°C. The characteristic pyrolytic products are cyclohexane homologues. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 199–204, 2003     

9‐Oxo‐10(E),12(Z),15(Z)‐Octadecatrienoic Acid Activates Peroxisome Proliferator‐Activated Receptor α in Hepatocytes

The peroxisome proliferator‐activated receptor (PPAR)α is mainly expressed in the liver and plays an important role in the regulation of lipid metabolism. It has been reported that PPARα activation enhances fatty acid oxidation and reduces fat storage. Therefore, PPARα agonists are used to treat dyslipidemia. In the present study, we found that 9‐oxo‐10(E),12(Z),15(Z)‐octadecatrienoic acid (9‐oxo‐OTA), which is a α‐linolenic acid (ALA) derivative, is present in tomato (Solanum lycopersicum) extract. We showed that 9‐oxo‐OTA activated PPARα and induced the mRNA expression of PPARα target genes in murine primary hepatocytes. These effects promoted fatty acid uptake and the secretion of β‐hydroxybutyrate, which is one of the endogenous ketone bodies. We also demonstrated that these effects of 9‐oxo‐OTA were not observed in PPARα‐knockout (KO) primary hepatocytes. To our knowledge, this is the first study to report that 9‐oxo‐OTA promotes fatty acid metabolism via PPARα activation and discuss its potential as a valuable food‐derived compound for use in the management of dyslipidemia.     

13‐Oxo‐9(Z),11(E),15(Z)‐octadecatrienoic Acid Activates Peroxisome Proliferator‐Activated Receptor γ in Adipocytes

Peroxisome proliferator‐activated receptor (PPAR)γ is expressed in adipose tissue and plays a key role in the regulation of adipogenesis. PPARγ activators are known to have potent antihyperglycemic activity and are used to treat insulin resistance associated with diabetes. Therefore, many natural and synthetic agonists of PPARγ are used in the treatment of glucose disorders. In the present study, we found that 13‐oxo‐9(Z),11(E),15(Z)‐octadecatrienoic acid (13‐oxo‐OTA), a linolenic acid derivative, is present in the extract of tomato (Solanum lycopersicum), Mandarin orange (Citrus reticulata), and bitter gourd (Momordica charantia). We also found that 13‐oxo‐OTA activated PPARγ and induced the mRNA expression of PPARγ target genes in adipocytes, thereby promoting differentiation. Furthermore, 13‐oxo‐OTA induced secretion of adiponectin and stimulated glucose uptake in adipocytes. To our knowledge, this is the first study to report that 13‐oxo‐OTA induces adipogenesis through PPARγ activation and to present 13‐oxo‐OTA as a valuable food‐derived compound that may be applied in the management of glucose metabolism disorders.