共查询到20条相似文献,搜索用时 15 毫秒
1.
N. Nicolaides 《Lipids》1971,6(12):901-905
By combined gas liquid chromatography-mass spectrometry a series of monomethyl branched fatty acids was found in the fatty
acid moiety of the wax esters of vernix caseosa. The methyl branch occurred on the even C-atoms of chains ranging from C11 to C17 (some 43 compounds in all). Except for the iso acids and possibly some of the anteiso acids, these could be formed by replacement
of malonyl CoA with a molecule of methyl malonyl CoA at the point of the branch. Smaller amounts of fatty acids also were
found with two methyl branches occurring on the even C-atoms of chains ranging from C9 to C15. 相似文献
2.
N. Nicolaides Evelyn C. Santos Konstantine Papadakis Edward C. Ruth Luciano Müller 《Lipids》1984,19(12):990-993
A group of long chain α,ω-diols (C29 to C34) has been identified in the lipids of steer and human meibomian gland excreta (meibum). These new lipids were isolated from
the steer meibum unsaponifiables. Proof of structure was provided by 1) the column chromatographic behavior and TLC of the
diols and their diacetates; 2) GLC on glass capillary columns; 3) fragmentation patterns in GC-MS; 4) NMR data, and 5) ozonolysis
studies of the unsaturates. Chain types for the steer sample were 51% straight monoenes, 8.5% straight saturates, 39% iso
and anteiso saturates and 1.5% iso and anteiso unsaturates. GC for the human sample gave straight monoenes 83%, straight saturates
8%, and iso plus anteiso saturates 9%. Close correspondence of the α,ω-diol chain lengths and types with meibum ω-hydroxy
fatty acids suggests a biochemical precursor relationship. 相似文献
3.
The fatty acids of rat skin surface lipids comprise four main skeletal types of chains which occur both as saturates and monoenes
and range from C12 to C38: straight even, straight odd, iso and anteiso (the latter two identified by GC retention data only). Two unidentified series
of branched monoenes also occur in trace amounts.
Reductive ozonolysis of monoenes reveals two characteristic double-bond position patterns, one for the straight even chain
series and the other for the straight odd chain series. The straight even chain pattern comprises four series, of which ω7
≫ω9>ω5>ω11; the straight odd chain series in contrast shows a large number of ω series with irregular distribution. The biosynthesis
of the even chain fatty acid monoenes can be thought of as occurring in two stages: synthesis of 14∶Δ9, 16∶Δ9, 18∶Δ9 and 20∶Δ9,
with 16∶Δ9 predominating; elongation of these chains mostly by 1, 2, or 3 C2 units but up to the unusually long lengths by 11 C2 units. For the formation of the former, two schemes by known pathways are proposed.
Iso and anteiso chains which are nearly all saturated comprised 1/3 the total fatty acids.
Special terms and abbreviations: Normal even=a straight chain with an even number of carbon atoms, normal odd=a straight chain
with an odd number of carbon atoms, ω=terminal carbon atom, iso=a straight chain with a methyl group at the ω−1 position,
anteiso=a straight chain with a methyl group at the w−2 position, Δn=a double bond between the nth and the (n+1)th carbon atom from the carbonyl group of the fatty acid or ester, ωn=a double bond between the ω∩nth and the ω-(n−1)th carbon atom where n is an integer, aldester=aldehyde methyl ester, Me=methyl, GLC=gas-liquid chromatography, TLC=thin-layer
chromatography. 相似文献
4.
Separation of sterol esters from wax esters in the lipids of vernix caseosa and adult human skin surface was accomplished
by column chromatography on MgO. The fatty acids of the sterol esters and wax esters of both samples were separated into saturates
and monoenes, and examined in detail by gas liquid chromatography (GLC). The saturated fatty acids of the wax esters of vernix
caseosa and of adult human skin surface were remarkably similar. They ranged in chain length from at least C11 to C30, six skeletal types being present: straight even, straight odd, iso, anteiso, other monomethyl branched and dimethyl branched.
A large number of patterns of monoenes were observed, each pattern consisting of desaturation of a specific chain at Δ6 or
Δ9 plus its extension or degradation products. The mole per cent of the total Δ6 and Δ9 patterns of wax ester fatty acid monoenes
of vernix caseosa were 87% and 12%, respectively, and 98% and 1%, respectively, for adult human skin surface lipid. The sterol
ester fatty acids of vernix caseosa were much different from those of adult human skin surface: vernix caseosa saturates were
largely branched and of lengths greater than C18, whereas the saturates of adult human surface lipid resembled the wax ester fatty acids. Of the vernix caseosa monoene patterns,
the mole per cent was 30% Δ6 and 70% Δ9, whereas of the adult human skin surface sterol ester fatty acids 89% were Δ6 and
11% Δ9. Chain extension was particularly pronounced in the sterol ester fatty acid monoenes of vernix caseosa amounting to
7–8 C2 units in some cases. The fatty acids of the sterol esters of both vernix caseosa and adult human skin surface appear to be
derived from the sebaceous gland and from the keratinizing epidermis, but those of the wax esters are from the sebaceous glands
only. 相似文献
5.
Characterization of branched chain fatty acids from subcutaneous triacyglycerols of barley-fed lambs 总被引:1,自引:0,他引:1
The fatty acids of subcutaneous triacylglycerols (containing ca. 11% of branched chain components) from lambs fed on barley-rich diets were fractionated by treatment with mercuric acetate and by urea adduct formation to yield concentrates rich in the branched chain components, all of which were saturated. The concentrates were subjected to analysis by high resolution gas liquid chromatography in conjunction with mass spectrometry. The branched chain fatty acids consisted of a complex mixture of mono-, di-, and trimethyl substituted components. The greater part of the mixture comprised monomethyl substituted acids of chain length 10–17 carbon atoms. Within each of these molecular species, a number of positional isomers was identified, notably in respect of methyltetradecanoic acid (methyl substituent on carbon 2, 4, 6, 8, 10, and 12) and methylhexadecanoic acid (methyl substituent on carbon 2, 4, 6, 8, 12, and 14). Homologous series also could be recognized of one of which all eight members from 4-methyldecanoic acid to 4-methylheptadecanoic acid were identified; together they accounted for ca. 39% of the branched chain fatty acids which were sampled for mass spectrometry. The dibranched acids identified consisted of five members of a homologous series, ranging in chain length from 11–15 carbon atoms and with substituent methyl groups at positions 4 and 8. Though the identity of only one tribranched acid (2,6,10-trimethyltetradecanoic acid) was established, others also apparently were present in the mixture. The probable involvement of methylmalonate in the biosynthesis of these branched chain acids is discussed briefly, with particular reference to the availability of vitamin B12 in relation to the activity of methylmalonyl coenzyme A mutase. 相似文献
6.
《Fuel》1987,66(5):587-593
Green River shale kerogen was degraded by a careful five-step oxidation with sodium dichromate in glacial acetic acid. Products isolated from each oxidation step were examined by capillary gas chromatography and combined gas chromatography-mass spectrometry. The analyses revealed the presence of several homologous series. Saturated normal monocarboxylic acids (C6C35) and saturated normal α,ω-dicarboxylic acids (C4C33) were the major constituent series, while isoprenoid acids (C14C21, except C18), iso and anteiso acids (C6C16), branched dicarboxylic acids (C20C29), triterpenoidal acids (C27C33), cyclic, and oxo-acids were the minor constituent series. Moreover, a few aromatic acids, branched ketones, heterocyclic compounds, as well as a series of (C25C30) n-alkanes were identified. The results were discussed in terms of the qualitative and quantitative variations of the products with duration of oxidation. The data corroborate the conclusion of a predominantly open chain crosslinked aliphatic structure for Green River kerogen, and indicate that aromatic structures are mainly in the form of isolated phenyl and tolyl groups. The results further confirm the presence of etioporphyrin as a significant constituent in the kerogen studied. 相似文献
7.
Ozonolysis studies of the monoenes of the fatty chain types in lipids of steer meibomian gland excreta (meibum) have confirmed
earlier structural assignments based on gas liquid chromatography (GLC) retention data and have assisted in assigning complete
structures to a group of recently identified ω-hydroxy fatty acids. The ω-hydroxy acids include straight-chain monoenoic acids
(85%), saturated anteiso and iso acids (13%), monoenoic acids of the latter group (1%) and, finally, saturates of the normal
monoenoic acids (1%). All the fatty chains of meibum can be biosynthesized by a unified process of chain buildup to primary
chain lengths of 12∶0–20∶0 for the straight evens, with 16∶0 predominating, 13∶0–21∶0 for the straight odds with 17∶0 predominating,
i16∶0 to i28∶0 for the iso and ai17∶0 to ai29∶0 for the anteiso chain types; then Δ9 desaturation of each of these chain types;
and finally chain elongation of 1–10 C2 units. Some chain degradation may also occur. The meibum lipid components involved are unsubstituted fatty acids, α-OH fatty
acids, ω-OH fatty acids, fatty alcohols and some other lipid components incompletely characterized. The carbon skeletons are
straight even, straight odd, iso and anteiso except that the α-OH fatty acids are only straight even and straight odd and
these chains are not elongated. All fatty chains are almost entirely saturated and monoenoic, the polyenes occurring in only
trace amounts. Biosynthesis of the fatty chains of human meibum evidently occurs similarly, except that considerably more
18∶0 than 16∶0 fatty acids are built up by the fatty acid synthetase, before desaturation and extension. 相似文献
8.
Helen L. Ngo Robert O. Dunn Eunha Hoh 《European Journal of Lipid Science and Technology》2013,115(6):676-683
Iso‐oleic acid is a mixture of C18‐unsaturated branched‐chain fatty acid isomers with a methyl group on various positions of the alkyl chain, which is the product of the skeletal isomerization reaction of oleic acid and is the intermediate used to make isostearic acid (C18‐saturated branched‐chain fatty acid isomers). Methyl iso‐oleate, a mixture of C18‐unsaturated branched‐chain fatty acid methyl ester isomers, is obtained via acid catalyzed esterification of iso‐oleic acid with methanol. The branched‐chain materials are liquid at room temperature and their “oiliness” property makes them an attractive candidate for the lubricant industry. In this paper, we report characterization of these branched‐chain materials using comprehensive two‐dimensional GC with time‐of‐flight mass spectrometry (GC × GC/TOF‐MS) and their physical and lubricity properties using tribology measurements. 相似文献
9.
Branched-chain fatty acids of perinephric triacylglycerols of semi-feral fallow deer (Dama dama dama) were analyzed by high resolution gas chromatography-mass spectrometry. Of the total fatty acids, 15.50% were Branched-chain
components including 8.96% iso acids, mostly 14-methylpentacanoic acid, 2.85% anteiso acids and 1.73% of other monomethyl-substituted
acids; dimethyl-branched acids with an iso structure (1.05%) and with an anteiso structure (0.18%) were also present. Whereas
the predominant iso acids and methyl-substituted iso acids had chain lengths of 13 and 15 carbon atoms, the anteiso acids
and methyl-substituted anteiso acids had chain lengths of 14 and 16 carbon atoms. Methyl substitution occurred on the even
numbered carbon atoms relative to the carboxyl group. The general composition is also given of the fatty acids comprising
the triacylglycerols of subcutaneous (rump area) and perinephric adipose tissue. 相似文献
10.
Isomeric methyl esters of fatty acids in three groups (C15, C17, C19) have been isolated from ruminant fats. Basic structural analysis by physiochemical techniques indicated that these odd-numbered
fatty acids were even chain with a single methyl branch on the chain. High resolution open-tubular gas liquid chromatographic
studies indicate that, with the exception of iso acid impurities in these fractions, only even-numbered carbons of the fatty
acid chains bear the methyl branch. 相似文献
11.
Buchang Shi Lin Wu Yunxin Liao Chunfen Jin Alexandra Montavon 《Topics in Catalysis》2014,57(6-9):451-459
After completely hydrogenation of Fischer–Tropsch synthesis (FTS) products on Pt/C catalyst, the branched C8, C10, C11, and C12 alkanes were identified using authentic samples to be methyl branched alkanes in both Co and Fe catalyzed reactions. No detectable ethyl branched and dimethyl branched alkanes were observed. The total amount of branched hydrocarbons in Co catalyzed FTS is about 5 % while the amount of branched hydrocarbons in Fe catalyzed FTS is about 25 %. The branched hydrocarbon distribution of Co catalyzed FTS does not obey the Anderson–Schulz–Flory (ASF) kinetics and the branched hydrocarbon distribution of Fe catalyzed FTS shows larger α value than that of straight chain alkanes. These results were explained by the formation of 2-alkylidene through readsorbed 1-alkenes, which can grow to form methyl branched hydrocarbons. Since the rate of propagation of 2-alkylidene is much slower than that of ethylidene and 1-alkylidenes, a “kink” will result in C2 in the FT product distribution plot. 相似文献
12.
Nstor M. Carballeira Aikomari Guzmn Jordan T. Nechev Kantcho Lahtchev Albena Ivanova Kamen Stefanov 《Lipids》2000,35(12):1371-1376
The lipid composition of a Bacillus sp., isolated from Lake Pomorie in Bulgaria, was unusual and consisted of 26 different fatty acids between C12 and C26, with anteiso C15−C17 saturated fatty acids predominating. The furan fatty acid, 10,13-epoxy-11-methyloctadeca-10,12-dienoic acid, was also identified,
a new finding for this genus. The hydrocarbons consisted of 30 different monounsaturated hydrocarbons, between C25 and C30, with the iso-iso, iso-anteiso, anteiso-anteiso, iso-normal, and anteiso-normal methyl branching for odd-numbered chains,
and the iso-iso, iso-anteiso, iso-normal, and anteiso-normal methyl branching for even-numbered chains. The double bond positions
in these hydrocarbons were determined by dimethyl disulfide derivatization followed by GC-MS, and the double-bond cis configuration was confirmed by infrared spectroscopy. Some previously unknown hydrocarbons in bacteria, such as (Z)-3,21-dimethyl-9-tricosene,
(Z)-3,21-dimethyl-10-tricosene, (Z)-2,24-dimethyl-11-pentacosene, and (Z)-2,25-dimethyl-13-hexacosene were identified. Sterols
were detected and were based on the sitosterol nucleus. 相似文献
13.
Debasish Pal Dipankar Banerjee Tarun K. Patra Amarendra Patra Amitabha Ghosh 《Journal of the American Oil Chemists' Society》1998,75(10):1373-1378
The sting ray, Dasyatis bleekeri (Blyth), has been studied for lipids and fatty acids of its liver. The neutral lipids identified were hydrocarbons, wax esters,
steryl esters, 1-O-alkyl-2,3-diacylglycerols, triacylglycerols, and sterols. Neutral lipids were predominant (91.8%), major components being
triacylglycerols (92.7%). Polyenoic fatty acids of n-3 series, viz. eicosapentaenoic acid and docosahexaenoic acid, were high in the phospholipid and neutral lipid fractions. Cholesterol was
the major component (67.9%) in the steryl ester fraction. Glyceryl ethers, with chainlengths up to 30 carbons, were recorded
with unsaturated, anteiso, iso, and normal chains. In wax ester alcohols, up to 32-carbon chains were recorded. Hydrocarbons
were up to 36-carbon chains with anteiso, iso, and normal chains. Among branched chain hydrocarbons, pristane was the major
component (6.7%) and squalene was present at the level of 3.5%. Chimyl and batyl alcohol backbones were the major components
found in 1-O-alkyl-diacylglycerols. 相似文献
14.
Tomoko Nishimaki-Mogami Ken-ichiro Minegishi Atushi Takahashi Yasushi Kawasaki Yuji Kurokawa Mitsuru Uchiyama 《Lipids》1988,23(9):869-877
Skin-surface lipids from the monkeyMacaca fascicularis are composed of sterol esters (38%), cholesterol (4%) and two types of wax diesters, identified as Type II (IIa and IIb,
17% and 40%, respectively). Type IIa contained diesters of 1,2-alkanediols esterified with two molecules of long-chain (C14−C34) fatty acids having straight and branched chains. In the diesters IIa, fatty acids shorter than C19 predominated in position 1, and fatty acids longer than C20 predominated in position 2. Type IIb contained diesters of 1,2-alkanediols esterified with C4 and C5 branched-chain fatty acids (predominantly isovaleric acid) at position 1 and long-chain (C14−C27) acids, having straight and branched chains, at position 2. The shortchain acids were converted to 2-nitrophenylhydrazides
and analyzed by high-performance liquid chromatography (HPLC). Ammonia chemical ionization (CI)-gas chromatography (GC)-mass
spectrometry (MS) resolved the intact diesters IIb into 12 peaks corresponding to molecular weights ranging from 597 to 748,
and showed that the molecular species, such as C21−C16−C5 (diol, fatty acid in position 2, fatty acid in position 1), C22−C16−C5 and C23−C16−C5, were prevalent. The fatty acids from both diesters were mostly (>98%) saturated. The 1,2-alkanediols from both diesters
consisted of C16−C26 saturated straight- and branched-chain components. The acyl groups of sterol esters contained 86% C14−C34 branched-chain acids. The unsaturated fatty acids (5.4%) belonged to a straight-chain monoenoic series having extremely long
chains (C18−C34). The branched-chain structures in the fatty acids and diols were iso and anteiso. These results show the species-specific
profile for the skin-surface lipid synthesis. 相似文献
15.
Robert O. Dunn Helen L. Ngo Michael J. Haas 《Journal of the American Oil Chemists' Society》2015,92(6):853-869
Biodiesel is an alternative diesel fuel derived mainly from the transesterification of plant oils with methanol or ethanol. This fuel is generally made from commodity oils such as canola, palm or soybean and has a number of properties that make it compatible in compression‐ignition engines. Despite its many advantages, biodiesel has poor cold flow properties that may impact its deployment during cooler months in moderate temperature climates. This work is a study on the use of skeletally branched‐chain‐fatty acid methyl esters (BC‐FAME) as additives and diluents to decrease the cloud point (CP) and pour point (PP) of biodiesel. Two BC‐FAME, methyl iso‐oleate and methyl iso‐stearate isomers (Me iso‐C18:1 and Me iso‐C18:0), were tested in mixtures with fatty acid methyl esters (FAME) of canola, palm and soybean oil (CaME, PME and SME). Results showed that mixing linear FAME with up to 2 mass% BC‐FAME did not greatly affect CP, PP or kinematic viscosity (ν) relative to the unmixed biodiesel fuels. In contrast, higher concentrations of BC‐FAME, namely between 17 and 39 mass%, significantly improved CP and PP without raising ν in excess of limits in the biodiesel fuel standard specification ASTM D 6751. Furthermore, it is shown that biodiesel/Me iso‐C18:0 mixtures matched or exceeded the performance of biodiesel/Me iso‐C18:1 mixtures in terms of decreasing CP and PP under certain conditions. This was taken as evidence that additives or diluents with chemical structures based on long‐chain saturated chains may be more effective at reducing the cold flow properties of mixtures with biodiesel than structures based on long‐chain unsaturated chains. 相似文献
16.
Fatty Acids from a Glass Sponge <Emphasis Type="Italic">Aulosaccus</Emphasis> sp. Occurrence of New Cyclopropane-Containing and Methyl-Branched Acids
下载免费PDF全文
![点击此处可从《Lipids》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In order to identify new structures, the free fatty acids from an extract of a glass sponge Aulosaccus sp. (from the north‐west Pacific) belonging to one of the least chemically investigated classes (Hexactinellida), were fractionated by RP‐HPLC and analyzed by NMR spectroscopy and GC–MS of their pyrrolidine derivatives, methyl(ethyl) esters and their dimethyl disulfide adducts. One hundred and twenty‐three C12–C31 acids (including nine new compounds) were detected, one hundred and ten of these compounds have not been found previously in glass sponges. The levels of common methylene‐interrupted polyenes, monoenes of the (n–7) family and less common branched‐chain components proved to be high. New acids were shown to be 5,13‐dimethyl‐tetradec‐4‐enoic, cis‐10,11‐methylene‐heptadecanoic, 10,12‐dimethyl‐octadecanoic, cis‐12,13‐methylene‐nonadecanoic, (14E)‐13‐methyl‐eicos‐14‐enoic, 19‐methyl‐eicos‐13‐enoic, cis‐20,21‐methylene‐heptacosanoic, 27‐methyl‐octacos‐21‐enoic and (22Z)‐nonacos‐22‐enoic. Some important mass spectrometric characteristics of pyrrolidides of homologous cyclopropane fatty acids are reported and discussed. 相似文献
17.
A Comprehensive Evaluation of the Melting Points of Fatty Acids and Esters Determined by Differential Scanning Calorimetry 总被引:1,自引:0,他引:1
The melting point is one of the most important physical properties of a chemical compound and it plays a significant role
in determining possible applications. For fatty acid esters the melting point is essential for a variety of food and non-food
applications, the latter including biodiesel and its cold-flow properties. In this work, the melting points of fatty acids
and esters (methyl, ethyl, propyl, butyl) in the C8–C24 range were determined by differential scanning calorimetry (DSC), many of which for the first time. Data for triacylglycerols
as well as ricinoleic acid and its methyl and ethyl esters were also acquired. For some compounds whose melting points have
been previously reported, data discrepancies exist and a comprehensive determination by DSC has not been available. Variations
in the present data up to several °C compared to data in prior literature were observed. The melting points of some methyl-branched
iso- and anteiso-acids and esters were also determined. Previously unreported systematic effects of compound structure on
melting point are presented, including those for ω-9 monounsaturated fatty acids and esters as well as for methyl-branched
iso and anteiso fatty acids and esters. The melting point of a pure fatty acid or ester as determined by DSC can vary up to
approximately 1 °C. Other thermal data, including heat flow and melting onset temperatures are briefly discussed.
Product names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
18.
Comparative studies on the fatty acid composition of moderately and extremely thermophilic bacteria 总被引:11,自引:0,他引:11
The fatty acids of three strains of extremely thermophilic bacteria and three strains of moderately thermophilic bacteria
were examined by gas liquid chromatography. All the thermophiles contained straight, iso, and ante-iso branched fatty acids.
Iso C17∶0 acid was abundant in both the moderately thermophilic strains (10–33%) and the extremely thermophilic strains (50–61%). The
pair of fatty acids iso C15∶0 and iso C17∶0 was the predominant pair in both the moderately (34–64%) and extremely (76–87%) thermophilic strains. The pair of fatty acids
ante-iso C15∶0 and ante-iso C17∶0 was present in larger amount in moderately (25–34%) than in extremely (8.5–15%) thermophilic strains. No hydroxy cyclopropane,
or unsaturated fatty acids were found. One extreme thermophile,Flavobacterium thermophilum HB-8 was grown at 6 different culture temperatures from 49–82 C, and the changes of its fatty acid composition were studied.
The ratios of iso C17∶0/iso C15∶0 and ante-iso C17∶0/ante-iso C15∶0 were much greater at higher culture temperatures, indicating chain elongation. 相似文献
19.
Mass Spectrometric Identification of Branched Chain Fatty Acids and Alcohols from Preen Gland Lipids The preen gland lipids of some birds were isolated, the waxes separated and resolved into fatty acid and alcohol fractions. The alcohols were oxidised with chromic acid to form the corresponding fatty acids. After methylation with methanolic HCl, the fatty acid methyl esters were investigated by capillary gas chromatography-mass spectrometry. The fatty acids possess mainly mono-, di- and trimethyl branched structures, the branching positions being located preferentially on C–2/–3/–4/–6, C–2,4/–2,6/–2,8/–3,7 C–2,4,6/–2,6,10 and C–6/C–10 or C–14. The mass spectrometric fragmentations which are significant for the structure elucidation of these fatty acid methyl esters are discussed in detail. The investigations indicate a correlation between the composition of the birds to defined orders of the natural system (chemotaxonomy). 相似文献
20.
cis-5,cis-9-Octadecadienoic acid (2.7%) andcis-5,cis-9,cis-12-octadecatrienoic acid (24.9%) are present in the seed oil ofLarix leptolepis. The double bond positions were identified by ozonolysis and by gas chromatography-mass spectrometry of methoxy derivatives. Small quantities of branched chain acids of various chain lengths were indicated by gas chromatography. The presence of C17 and C19 branched methyl esters was confirmed by gas chromatography-mass spectrometry. 相似文献