The mass spectra of the 4,4-dimethyloxazoline derivatives of some conjugated hydroxy ene-yne C17 and C18 fatty acids

The mass spectra of the 4,4-dimethyloxazoline derivatives from various fatty acids with a hydroxy group in conjugation with conjugated double-triple bonds (7-hydroxy-trans-10-heptadecene-8-ynoic acid; 7-hydroxy-trans-10, 16-heptadecadiene-8-ynoic acid; 8-hydroxy-rans-11-octadecene-9-ynoic acid; 8-hydroxy-trans-11, 17-octadecadiene-9-ynoic acid) have been examined and compared with their analogous nonhydroxy derivatives. The position of the hydroxy group was unequivocally proven by characteristic odd-numbered fragment peaks, explainable by α-cleavage at the hydroxy group at the oxazoline end of the molecule. The weak ions produced by α-cleavage at the other side of the hydroxy group indicated that the hydroxy group must be in conjugation with the ene-yne system. Fragments that allow one to distinguish between ene-yne or yne-ene systems were absent. In conjunction, the weak molecular ion and the more intense M-18 ion could confirm the molecular weight of each fatty acid. This work was presented in parts at the Second International Symposium of Natural Products and Their Applications in Concepción/Chile (30.11.-2.12.94). (Title of the symposium in Spanish is II Simposio internacional de productos naturales y sus applicaciones.)     

Gas-liquid chromatography-mass spectrometry of the 4,4-dimethyloxazoline derivatives of Δ5-unsaturated polymethylene-interrupted fatty acids from conifer seed oils

The fatty acids from the seed oils of three Conifer species (one Pinaceae,Pinus pinaster, and two Cupressaceae,Chamaecyparis lawsoniana andBiota orientalis) have been analyzed as their 4,4-dimethyloxazoline (DMOX) derivatives by gas-liquid chromatography coupled with mass spectrometry. The structures of six Δ5-unsaturated polymethylene-interrupted fatty acids (Δ5-UPIFA) were established, confirming previous studies in which they were identified by their equivalent chainlengths (ECL) and by comparison with related authentic standards. These acids were:cis-5,cis-9 18∶2,cis-5,cis-9,cis-12 18∶3 (P. pinaster),cis-5,cis-9,cis-12,cis-15 18∶4 (C.lawsoniana),cis-5,cis-11 20∶2,cis-5,cis-11,cis-14 20∶3 (all species),cis-5,cis-11,cis-14,cis-17 20∶4 (B. orientalis) acids. In addition,cis-9 18∶1,cis-9,cis-12 18∶2 (all species) andcis-9,cis-12,cis-15 18∶3 (Cupressaceae) acids, together with their elongation products [cis-11 20∶1,cis-11,cis-14 20∶2 (all species) andcis-11,cis-14,cis-17 20∶3 (B. orientalis) acids] were also identified. In the mass spectra, DMOX derivatives of all Δ5-UPIFA showed an intense peak atm/z 153, which is a diagnostic ion of fatty acid derivatives with a Δ5-ethylenic bond. Other double bonds were localized by ion pairs that differed by 12 atomic mass units. The present study fully justifies the use of ECL to identify Δ5-UPIFA in Conifer seed oils, in which they are ordinary components.     

Electron impact mass spectra of the oxazoline derivatives of some conjugated diene and triene C18 fatty acids

The location of the double-bond systems of some conjugated diene and triene C₁₈ fatty acids (C18∶2[9,11], C18∶2[10,12], C18∶3[9,11,13] and C18∶3[10,12,14]) derived from alkaline isomerization has been determined by gas chromatography/mass spectroscopy analysis of their 4,4-dimethyloxazoline derivatives. The positions of the double bonds were indicated by a characteristic mass separation of 12 atomic mass units for each olefinic bond. Furthermore, the structure assignments were supported by the presence of prominent formal allylic cleavage peaks.     

Analysis of C18:1 cis and trans fatty acid isomers by the combination of gas-liquid chromatography of 4,4-dimethyloxazoline derivatives and methyl esters

Trans fatty acids in foods are usually analyzed by gas-liquid chromatography (GLC) of fatty acid methyl esters (FAME). However, this method may produce erroneously low values because of insufficient separation between cis and trans isomers. Separation can be optimized by preceding silver-ion thin-layer chromatography (Ag-TLC), but this is laborious. We have developed an efficient method for the separation of 18-carbon trans fatty acid isomers by combining GLC of FAME with GLC of fatty acid 4,4-dimethyloxazoline (DMOX) derivatives. We validated this method against conventional GLC of FAME, with and without preceding Ag-TLC. Fatty acid isomers were identified by comparison with standards, based on retention times and mass spectrometry. Analysis of DMOX derivatives allowed the 13t, 14t, and 15t isomers to be separated from the cis isomers. The combination of the GLC analyses of FAME and DMOX derivatives gave results comparable with those obtained by GLC of FAME after preceding Ag-TLC, while saving about 100 h of manpower per 25 samples. It allowed the identification and quantitation of 11 trans and 8 cis isomers and resulted in 25% higher values for total C_18:1 trans, compared with the analysis of FAME alone. The combination of DMOX and FAME analyses, as applied to the analysis of 14 foods that contained ruminant fat and partially hydrogenated vegetable and fish oils, indicated that the most common isomers were 11t in ruminant fats, 9t in partially hydrogenated fish fats, and either 9t or 10t in partially hydrogenated vegetable fats. The combination of GLC analyses of FAME and DMOX derivatives of fatty acids improves the quantitation of 18-carbon fatty acid isomers and may replace the laborious and time-consuming Ag-TLC.     

Cyclopropenoid fatty acids of six seed oils from malvaceae

The seeds ofAlyogine hakeifolia, Alyogine huegelii,Gossypium australe, Hibiscus coatesii, Lawrencia viridigrisea andRadyera farragei (Malvaceae) contained 13.5-18.6% oil. Linoleic acid predominated (60.0-68.2%) in the component fatty acids of all the oils, followed by palmitic (9.9-18.1%) and oleic acids (7.8-15.8%). Cyclopropene fatty acids, malvalic and sterculic, were present in small concentrations (1.0-4.4%, 0.1-1.5% respectively). Dihydrosterculic acid was present in small quantities (trace-2.1%). *To whom correspondence should be addressed at Department of Chemistry, P.O. Box 320, University of Papua New Guinea, Papua, New Guinea.     

Identification of nine acetylenic fatty acids, 9-hydroxystearic acid and 9,10-epoxystearic acid in the seed oil ofJodina rhombifolia hook et arn. (Santalaceae)

In addition to some usual fatty acids, the seed oil ofJodina rhombifolia (Santalaceae) contains nine acetylenic fatty acids [9-octadecynoic acid (stearolic acid) (1.1%),trans-10-heptadecen-8-ynoic acid (pyrulic acid) (20.1%), 7-hydroxy-trans-10-heptadecen-8-ynoic acid (2.3%),trans-10,16-heptadecadien-8-ynoic acid (0.7%), 7-hydroxy-trans-10,16-heptadecadien-8-ynoic acid (0.1%),trans-11-octadecen-9-ynoic acid (ximenynic acid) (20.3%), 8-hydroxy-trans-11-octadecen-9-ynoic acid (12.2%),trans-11,17-octadecadien-9-ynoic acid (1.5%), 8-hydroxy-trans-11,17-octadecadien-9-ynoic acid (1.3%), 9-hydroxystearic acid (<0.1%) and 9,10-epoxystearic acid (0.7%)]. The fatty acids have been analyzed by gas chromatography/mass spectrometry of their methyl ester and 4,4-dimethyloxazoline derivatives. The hydroxy fatty acid methyl esters have been examined also as trimethyl-silyl ethers. Furthermore, the fatty acid methyl esters (FAME) have been fractionated according to their polarity (FAME-A: nonhydroxy; FAME-B: hydroxy fatty acids) and to their degree of unsaturation (FAME-A1/A2; FAME-B1/B2) by preparative thin-layer chromatography and argentation chromatography, respectively. All of these fractions have been analyzed by ultraviolet and infrared spectroscopy, and the fractions FAME-A and FAME-B have been analyzed further by nuclear magnetic resonance (¹H,¹³C, 2D H/C, attached proton test) spectroscopy and gas chromatography/mass spectrometry. This work is dedicated to the 65th birthday of Prof. Dr. K. Pfeilsticker, Institut of Food Science, University Bonn (Germany).     

Separation and identification of ximenynic acid isomers in the seed oil ofSantalum spicatum R.Br. as their 4,4-dimethyloxazoline derivatives

The seed oil ofSantalum spicatum contains a significant amount of ximenynic acid,trans-11-octadecen-9-ynoic acid, a long-chain acetylenic fatty acid, as a major component (34%). The identity oftrans-ximenynic acid was confirmed after isolation by ultraviolet, infrared, and nuclear magnetic resonance (NMR) (¹H- and¹³C-) spectroscopy and by gas chromatography/mass spectrometry (GC/MS). Thecis isomer of ximenynic acid was also found (<1%) in some samples. Thecis andtrans isomers were characterized by GC/MS comparison of their methyl esters and 4,4-dimethyloxazoline derivatives.     

A minor source of vernolic,malvalic, and sterculic acids inPithecollobium dulce (syn.Inga dulcis) seed oil

Pithecollobium dulce, Benth (syn.Inga dulcis, Willd) seed oil, belonging to the Leguminosae plant family, contains minor amounts of vernolic acid (12,13-epoxy-octadec-cis-9-enoic acid, 10.0%), malvalic acid [7-(2-octacyclopropen-1-yl)heptanoic acid, 3.2%], and sterculic acid [8-(2-octacyclopropen-1-yl)octanoic acid, 2.0%]. The other normal fatty acids are palmitic (12.1%), stearic (4.2%), behenic (10.6%), oleic (34.1%), and linoleic (23.8%). These fatty acids have been characterized by Fourier transform infrared,¹H nuclear magnetic resonance, mass spectrometry and gas-liquid chromatography techniques and by chemical degradations.     

Polyhydroxy fatty acids and their derivatives from plant oils

A novel process for the industrial production of hydroxylated fatty acids involves epoxidation of plant oils and their derivatives, followed by catalytic epoxy ring opening in the presence of water or other hydrogen donors, such as alcohols, diols, and amines. Depending on the starting material, epoxidation followed by opening of the oxirane ring leads to fatty acids that contain vicinal diol groups or to other substituted hydroxylated fatty acid derivatives. As an example for the preparation of a substituted hydroxylated fatty acid derivative, the reaction of epoxidized rapeseed oil with monobutylamine as hydrogen donor is described. Apart from the intended formation of hydroxyl groups with vicinal aminoalkyl groups, partial aminolysis of the ester compound was also observed. Another example describes the reaction of epoxidized rapeseed oil with different molar proportions of 1,4-butanediol as hydrogen donor. Depending on the molar proportion of the hydrogen donor, interesterification, or intermolecular ether formation were observed as side reactions. The properties of various technical hydroxylated fatty acids and their derivatives, prepared according to this novel process, are given, and potential applications of these products are suggested.     

Preparation of malvalic and sterculic acid methyl esters from Bombax munguba and Sterculia foetida seed oils

A method has been developed for the preparation of highly pure malvalic (cis-8,9-methyleneheptadec-8-enoic) and sterculic (cis-9,10-methyleneoctadec-9-enoic) acid methyl esters starting from Bombax munguba and Sterculia foetida seed oils. The methyl esters of these oils were prepared by sodium methylate-catalyzed transmethylation followed by cooling (6°C) the hexane solution of crude methyl esters and separation of insoluble fatty acid methyl esters by centrifugation in the case of B. munguba and by column chromatography in the case of S. foetida. Subsequently, the saturated straight-chain fatty acid methyl esters were almost quantitatively removed by urea adduct formation. Finally, methyl malvalate and methyl sterculate were separated from the remaining unsaturated fatty acid methyl esters, in particular methyl oleate and methyl linoleate, by preparative high-performance liquid chromatography on C₁₈ reversed-phase using acetonitrile isocratically. Methyl malvalate and methyl sterculate were obtained with purities of 95–97 and 95–98%, respectively.     

The structures of cyclopentenyl fatty acids in the seed oils of flacourtiaceae species by GC-MS of their 4,4-dimethyloxazoline derivatives

The structures of cyclopentenyl fatty acids in the seed oils ofHydnocarpus anthelmintica Pierre et Laness.,H. alphina Wight,H. hainanensis (Merr.) andTaraktogenos merrilliana C.Y. Wu, all belonging to the family Flacourtiaceae, have been identified by GC-MS of the mixed 2-substituted 4,4-dimethyloxazoline (DMOX) derivatives. These variations are characterized by the presence of key fragments at (M-43), (M-55) and (M-67), while the location of a double bond in the chain is indicated by a 12-mass interval between the highest peaks of two adjacent homologous ion clusters. The unique fragmentation pattern coupled with the good gas chromatographic qualities of these derivatives enable convenient structure determination of cyclopentenyl fatty acids in complex mixtures. Chemical Modification in Mass Spectrometry 9. For preceding paper (Part 8) of this series, see (1).     

Location of triple bonds in the fatty acids from the kernel oil ofPyrularia edulis by GC-MS of their 4,4-dimethyloxazoline derivatives

Location of triple bond in long-chain fatty acids has been effected by mass spectrometry or gas chromatography-mass spectrometry of their 4,4-dimethyloxazoline (DMOX) derivatives. The position of acetylenic linkage, either isolated or conjugated with olefinic bond(s) is indicated by a clear separation of 10 atomic mass units between the highest peaks of two neighboring fragment clusters. The acetylenic acid components of the kernel oil ofPyrularia edulis were found to be 17:1(8a), 18:1(9a), 18:2(9a,11), 18:2(9a,17) and 18:3(9a,11,17). Chemical Modification in Mass Spectrometry. 10. For preceding paper of this series, see (1).     

Bis‐methylene‐interrupted octadecadienoic fatty acids in Bulgarian bovine butter fats

Preparative silver nitrate thin‐layer chromatography of fatty acid methyl esters and gas chromatography‐mass spectrometry of 4,4‐dimethyloxazoline derivatives were applied in combination to analyze the cis,cis octadecadienoic (18:2) fraction in commercial samples of bovine butter fat in Bulgaria. The main component, 9,12–18:2 was accompanied by a series of bis‐methylene‐interrupted isomers, cis,cis‐5,9‐; 6,10‐; 9,13‐ and 11,15–18:2, which were unambiguously identified by their specific mass spectra. The latter are characterized by the presence of very intensive diagnostic fragments which help to correctly locate the position of the double bond system in the carbon chain. The cis,cis‐5,9–18:2 isomer was found for the first time in butter fat, and the 6,10–18:2 isomer has not been described as yet.     

Lipase-catalyzed reactions involving thia fatty acids and ester derivatives

Enzymatic hydrolysis of synthetic methyl 5-, 9-, and 12-thiastearates in aqueous media withCandida cyclindracea or porcine pancreatic lipases gave the corresponding fatty acids in 70–100% yield. Hydrolysis of the 3- and 4-positional isomers gave only 15–25% of the free thia fatty acids, suggesting discrimination against these isomers by lipases. No lipolysis was achieved with methyl 2-thialaurate under a range of reaction conditions. Esterification of the 3-, 4-, 5-, 9-, and 12-thiastearic acids withn-butanol inn-hexane using Lipozyme (immobilizedRhizomucor miehei) as the biocatalyst gave the corresponding butyl esters in 80–95% yield. Interesterification (acyl exchange) of triolein with methyl 9-thiastearate in the presence of Lipozyme showed the incorporation of 9-thiastearoyl chain at only one of the α-positions of triolein. In the case of methyl 2-thialaurate, no lipase-catalyzed acyl exchange reaction was possible. This study showed that the position of the sulfur atom in thia fatty esters affects the lipase-catalyzed hydrolysis and interesterification reactions.     

Renewable linear alpha olefins by selective ethenolysis of decarboxylated unsaturated fatty acids

A two‐step concept for the production of linear alpha olefins from biomass is reported. As a starting material an internally unsaturated C17 alkene was used, which was obtained by the decarboxylation of oleic acid. Here, we report on the ethenolysis of this bio‐based product, using commercially available metathesis catalysts. The desired alpha olefin products, 1‐nonene and 1‐decene, were obtained in excellent yield (96%) and selectivity (96%). Practical applications: The two‐step conversion described in this contribution, starting from unsaturated fatty acids, provides a method for the production of industrially important linear alpha olefins. These valuable products are widely used as starting materials for the production of surfactants and polymers such as linear low density polyethylene (LLDPE).     

Metabolic engineering strategies in biosynthesis of amino acids and their derivatives

The industrial production of amino acids has a history of more than 100 years, and is mostly used in animal feed and food additives. Many types of amino acids such as L-cysteine, β-alanine, S-adenosylmethionine, 4-hydroxyisocyanine acid and homoserine also have broad applications. Plant extraction and chemical synthesis are the commonly used methods to produce these amino acids and their derivatives. Compared with the way of chemical synthesis or separation and extraction, the use of microbial cells as a platform for the production of amino acids and derivatives has unique advantages such as green safety and sustainability. This review highlights the recent advances in developing metabolic engineering strategies including increase of the carbon sources uptake rate, elimination of the rate-limiting steps, enhancement of the carbon flux through the target pathway, remove of the feed-back inhibition effect and regulation of the intermediates and products transportation for biological production of amino acids and their derivatives. Our goals are to provide a landscape of current works and present guidelines to address future challenges in biosynthesis of amino acids and their derivatives using engineered microorganisms.     

代谢工程调控策略在生物合成氨基酸及其衍生物中的应用

氨基酸的工业化生产已有上百年历史,多用于动物饲料和食品添加剂;很多种类的氨基酸如L-半胱氨酸、β-丙氨酸、S-腺苷甲硫氨酸、4-羟基异亮氨酸和高丝氨酸等也具有很高的应用价值。相较于化工合成或分离提取的方式,利用微生物细胞作为平台生产氨基酸及其衍生物具有绿色安全、可持续等独特的优势。本文综述了近年来微生物合成氨基酸及其衍生物的研究进展,分别介绍了碳源的高效利用、限速步骤的调节、碳通量的调节、转录和反馈抑制调节以及转运调节等代谢调控策略在提高微生物生产氨基酸及其衍生物效率的研究及应用,分析了不同调控策略的优势和缺点,总结了不同氨基酸及其衍生物的应用价值,最后展望了微生物作为细胞工厂生产各类氨基酸及其衍生物的广阔前景。     

怒江漆油中高级脂肪酸成分

对云南怒江漆油 (漆树籽油 )进行皂化得到了漆油的总脂肪酸 ,将总脂肪酸甲酯化得到总脂肪酸甲酯 ,用GC MS联用仪测定了所含高级脂肪酸的成分 ,结果表明云南怒江漆树油中高级脂肪酸分别为棕榈酸、油酸、硬脂酸、花生酸、二十烷二酸。其中 ,棕榈酸的质量分数高达 76.9%。     

The synthesis of silicon oleochemicals by hydrosilylation of unsaturated fatty acid derivatives

The hydrosilylation of fatty acid esters with terminal or internal double bonds catalysed by H₂ PtCl₆ is described. The reaction was carried out with good yields at ambient pressure under mild conditions. Methyl undec‐10‐enoate was reacted with chloro‐ or alkoxyhydrosilanes giving moderate to good yields (41—77%) and even its reaction with alkylhydrosilanes produced low yields (below 20%). Under optimised conditions the hydrosilylation of methyl linoleate gave only with reactive chlorohydrosilanes acceptable yields, between 25 to 83%, of regioisomers. The hydrosilylation of methyl α‐linolenate with dimethylchlorosilane gave a mixture of regioisomeric 1:1‐ and 2:1‐hydrosilylation adducts in a total yield of 40%. The hydrosilylation of ethyl oleate did not proceed at all under our conditions. In the case of methyl undec‐10‐enoate a biphasic solvent system permitted the simple separation and reuse of the homogeneous catalyst.     

新鲜椰子果肉脂肪酸成分的GC-MS分析

以海南产新鲜高种椰为原料,参照国家标准GB/T 14772-93和GB5009.6-85,分别采用索氏抽提法和酸水解法提取新鲜椰肉脂肪酸成分,再经过氢氧化钾碱催化法进行脂肪酸的甲酯化处理后,通过气相色谱/质谱联用技术分析测定脂肪酸的组成。共检出9种脂肪酸成分,主要成分为以月桂酸为主的C6至C18系列饱和脂肪酸。