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1.
The initial steps in the autoxidation of CLA methyl ester are poorly understood. The aim of this study was to determine the
stereochemistry of the hydroperoxides formed during autoxidation of CLA methyl ester in the presence of a good hydrogen atom
donor. For this purpose, 9-cis, 11-trans CLA methyl ester was autoxidized in the presence of α-tocopherol under atmospheric oxygen at 40°C in the dark. The CLA methyl
ester hydroperoxides were isolated, reduced to the corresponding hydroxy derivatives, and separated by HPLC. The stereochemistry
of seven hydroxy-CLA methyl esters was investigated. The position of the hydroxy group was determined by GC-MS. The geometry
as well as the position of the double bonds in the alkyl chain was determined by NMR. In addition, the 13C NMR spectra of six hydroxy-CLA methyl esters were assigned using COSY, gradient heteronuclear multiple bond correlation,
gradient heteronuclear single quantum correlation, and total correlation spectroscopy experiments. The autoxidation of 9-cis, 11-trans CLA methyl ester in the presence of a good hydrogen atom donor is stereoselective in favor of one geometric isomer, namely
the 13-(R,S)-hydroperoxy-9-cis, 11-trans-octadecadienoic acid methyl ester. Three types of conjugated diene hydroperoxides are formed as primary hydroperoxides: trans,trans hydroperoxides (12-OOH-8t,10t and 9-OOH-10t,12t), a cis,trans hydroperoxide with the trans double bond adjacent to the hydroperoxide-bearing carbon atom (13-OOH-9c,11t), and a new type of cis,trans lipid hydroperoxide with the cis double bond adjacent to the hydroperoxide-bearing carbon atom (8-OOH-9c,11t). In addition, three nonkinetic hydroperoxides (13-OOH-9t,11t, 8-OOH-9t,11t, and 9-OOH-10t,12c) are formed. This study supports the theory that CLA methyl ester autoxidizes at least partly through an autocatalytic free
radical reaction. The complexity of the hydroperoxide mixture is due to formation of two different pentadienyl radicals. Moreover,
the stereoslectivity in favor of one geometric isomer can be explained by the selectivity of the two previous steps: the preferential
formation of a W-conformer of the pentadienyl radical over the Z-conformer, and regioselectivity of the oxygen addition to
the pentadienyl radical. 相似文献
2.
O. Berdeaux W. W. Christie F. D. Gunstone J. -L. Sebedio 《Journal of the American Oil Chemists' Society》1997,74(8):1011-1015
The conjugated linoleic acid methyl cis-9,trans-11-octadecadienoate has been prepared on a large scale from methyl ricinoleate. Methyl ricinoleate was purified from castor
esters by a partition method. It was converted to the mesylate, which was reacted with a base (1,8-diazabicyclo[5,4,0]-undec-7-ene)
to give a product that contained 66% of the desired ester. Two urea crystallizations produced a product containing 83% methyl
cis-9,trans-11-octadecadienoate, the identity of which was confirmed by gas chromatography linked to mass spectrometry and by Fourier
transform infrared spectroscopy. The remaining impurities were methyl cis-9,cis-11- and cis-9-,trans-12-octadecadienoate. 相似文献
3.
Lipase-catalyzed fractionation of conjugated linoleic acid isomers 总被引:14,自引:0,他引:14
Haas MJ Kramer JK McNeill G Scott K Foglia TA Sehat N Fritsche J Mossoba MM Yurawecz MP 《Lipids》1999,34(9):979-987
The abilities of lipases produced by the fungus Geotrichum candidum to selectively fractionate mixtures of conjugated linoleic acid (CLA) isomers during esterification of mixed CLA free fatty
acids and during hydrolysis of mixed CLA methyl esters were examined. The enzymes were highly selective for cis-9,trans-11–18∶2. A commercial CLA methyl ester preparation, containing at least 12 species representing four positional CLA isomers,
was incubated in aqueous solution with either a commercial G. candidum lipase preparation (Amano GC-4) or lipase produced from a cloned high-selectivity G. candidum lipase B gene. In both instances selective hydrolysis of the cis-9,trans-11–18∶2 methyl ester occurred, with negligible hydrolysis of other CLA isomers. The content of cis-9,trans-11–18∶2 in the resulting free fatty acid fraction was between 94 (lipase B reaction) and 77% (GC-4 reaction). The commercial
CLA mixture contained only trace amounts of trans-9,cis-11–18∶2, and there was no evidence that this isomer was hydrolyzed by the enzyme. Analogous results were obtained with these
enzymes in the esterification in organic solvent of a commercial preparation of CLA free fatty acids containing at least 12
CLA isomers. In this case, G. candidum lipase B generated a methyl ester fraction that contained >98% cis-9,trans-11–18∶2. Geotrichum candidum lipases B and GC-4 also demonstrated high selectivity in the esterification of CLA with ethanol, generating ethyl ester fractions
containing 96 and 80%, respectively, of the cis-9,trans-11 isomer. In a second set of experiments, CLA synthesized from pure linoleic acid, composed essentially of two isomers,
cis-9,trans-11 and trans-10,cis-12, was utilized. This was subjected to esterification with octanol in an aqueous reaction system using Amano GC-4 lipase
as catalyst. The resulting ester fraction contained up to 97% of the cis-9,trans-11 isomer. After adjustment of the reaction conditions, a concentration of 85% trans-10,cis-12–18∶2 could be obtained in the unreacted free fatty acid fraction. These lipase-catalyzed reactions provide a means for
the preparative-scale production of high-purity cis-9,trans-11–18∶2, and a corresponding CLA fraction depleted of this isomer. 相似文献
4.
Taina I. Hmlinen Susanna Sundberg Marjukka Mkinen Seppo Kaltia Tapio Hase Anu Hopia 《European Journal of Lipid Science and Technology》2001,103(9):588-593
The aim of this study was to investigate whether hydroperoxides are formed in the autoxidation of conjugated linoleic acid (CLA) methyl ester both in the presence and absence of α‐tocopherol. The existence of hydroperoxide protons was confirmed by D2O exchange and by chemoselective reduction of the hydroperoxide groups into hydroxyl groups using NaBH4. These experiments were followed by nuclear magnetic resonance (NMR) spectroscopy. The 13C and 1HNMR spectra of a mixture of 9‐hydroper‐oxy‐10‐trans,12‐cis‐octadecadienoic acid methyl ester (9‐OOH) and 13‐hydroperoxy‐9‐cis, 11‐trans‐octadecadienoic acid methyl ester (13‐OOH), which are formed during the autoxidation of methyl linoleate, were studied in detail to allow the comparison between the two linoleate hydroperoxides and the CLA methyl ester hydroperoxides. The 13CNMR spectra of samples enriched with one of the two linoleate hydroperoxide isomers were assigned using 2D NMR techniques, namely Correlated Spectroscopy (COSY), gradient Heteronuclear Multiple Bond Correlation (gHMBC), and gradient Heteronuclear Single Quantum Correlation (gHSQC). The 13C and 1H NMR experiments performed in this study show that hydroperoxides are formed during the autoxidation of CLA methyl ester both in the presence and absence of α‐tocopherol and that the major isomers of CLA methyl ester hydroperoxides have a conjugated monohydroperoxydiene structure similar to that in linoleate hydroperoxides. 相似文献
5.
Separation Behavior of Octadecadienoic Acid Isomers and Identification of cis‐ and trans‐Isomers Using Gas Chromatography
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Using a strongly polar cyanopropyl capillary column we have investigated the gas chromatography (GC) separation behaviors of 24 octadecadienoic acid methyl ester (18:2ME) isomers compared against saturated methyl stearate (18:0ME) and arachidic acid methyl ester (20:0ME), and the dependency on the GC column temperature. The 24 isomers were obtained by performing cis‐to trans‐isomerization of six regioisomers: five of the 18:2ME isomers were prepared by the partial reduction of methyl α‐linolenate and methyl γ‐linolenate C18 trienoic acids with different double bond positions, whereas the sixth isomer, 18:2ME (c5, c9), was obtained from a raw constituent fatty acid methyl ester (FAME) sample extracted from Japanese yew seeds. There are no reference standards commercially available for 18:2ME isomers, and in elucidating the elution order of these isomers this study should help the future identification of cis‐ and trans‐type of 18:2ME. We also report the identification method of cis‐ and trans‐type of FAME using equivalent chain lengths and attempt the identification of cis‐ and trans‐type of 18:2ME isomers from partially hydrogenated canola oil. 相似文献
6.
The need for a selective catalyst to hydrogenate linolenate in soybean oil has prompted our continuing study of various model
triunsaturated fats. Hydrogenation of methylβ-eleostearate (methyltrans,trans,trans-9,11,13-octadecatrienoate) with Cr(CO)3 complexes yielded diene products expected from 1,4-addition (trans-9,cis-12- andcis-10,trans-13-octadecadienoates). Withα-eleostearate (cis,trans,trans-9,11,13-octadecatrienoate), stereoselective 1,4-reduction of thetrans,trans-diene portion yielded linoleate (cis,cis-9,12-octadecadienoate). However,cis,trans-1,4-dienes were also formed from the apparent isomerization ofα- toβ-eleostearate. Hydrogenation of methyl linolenate (methylcis,cis,cis-9,12,15-octadecatrienoate) produced a mixture of isomeric dienes and monoenes attributed to conjugation occurring as an intermediate
step. The hydrogenation ofα-eleostearin in tung oil was more stereoselective in forming thecis,cis-diene than the corresponding methyl ester. Hydrogenation of linseed oil yielded a mixture of dienes and monoenes containing
7%trans unsaturation. We have suggested how the mechanism of stereoselective hydrogenation with Cr(CO)3 catalysts can be applied to the problem of selective hydrogenation of linolenate in soybean oil.
No. Market. Nutr. Res. Div., ARS, USDA. 相似文献
7.
Linoleic acid was heated at 200°C under helium. Analysis of degradation products by GC on a long polar open tubular capillary
column showed the presence of CLA isomers. The identified mono trans CLA isomers were cis-9, trans-11, trans-9, cis-11, trans-10, cis-12, cis-10, trans-12, trans-8, cis-10, and cis-11, trans-13 18:2 acids. Oils containing different levels of linoleic acid (peanut, sesame seed, and safflower seed oils) were also
heat treated, resulting in similar CLA distributions. Elution order was confirmed using cis-9, trans-11 and trans-10, cis-12 acid methyl esters standards and their respective configuration isomers (trans-9, cis-11, cis-10, trans-12), obtained after mild selenium-catalyzed isomerization. These results indicated that two conjugated mono trans isomers of 18:2 acid, cis-8, trans-10 and trans-11, cis-13 18:2 were absent from the series, thus strongly suggesting that some constraints were preventing their formation. By heating
pure methyl rumenate (cis-9, trans-11 18:2) under similar conditions, isomerization resulted principally in a nearly equimolar mixture of methyl rumenate and
trans-8, cis-10 18:2. Similarly, the methyl ester of trans-10, cis-12 18:2 acid was partially transformed into cis-11, trans-13 18:2 acid. Respective geometrical isomers were also formed in trace amounts. A concerted pericyclic isomerization mechanism,
a [1,5] sigmatropic rearrangement, is proposed that limits the conjugated system to isomerization from a cis-trans acid to a trans-cis acid, and vice versa. This mechanism is consistent with undetected cis-8, trans-10 and trans-11, cis-13 18:2 isomers in heated oils containing linoleic acid. 相似文献
8.
M. Adam M. Chew S. Wasserman A. McCollum R. E. McDonald M. M. Mossoba 《Journal of the American Oil Chemists' Society》1998,75(3):353-358
An attenuated total reflection infrared spectroscopy procedure was collaboratively studied among two sets of five laboratories
for quantitating the total trans fatty acid levels in neat (without solvent) hydrogenated vegetable oils, measured as triacylglycerols in one study, and as
fatty acid methyl ester derivatives in the other. Unlike the fatty acid methyl esters, the triacylglycerols required no derivatization
but had to be melted prior to measurement. To obtain a symmetric absorption band at 966 cm−1 on a horizontal background, the single-beam spectrum of the trans-containing fat was "ratioed" against that of a refined oil or a reference material that contained only cis double bonds. A single-bounce horizontal attenuated total reflection cell that requires 50 μL of undiluted test samples was
used for oils, melted fats, or their methyl esters. For fatty acid methyl esters, the reproducibility relative standard deviations
were in the range of 0.9 to 18.46% for 39.08 to 3.41% trans, determined as methyl elaidate per total fatty acid methyl esters. For five pairs of triacylglycerol blind duplicates, the
reproducibility and repeatability relative standard deviations were in the ranges of 1.62 to 18.97%, and 1.52 to 13.26%, respectively,
for 39.12 to 1.95% trans, determined as trielaidin per total triacylglycerols. Six pairs of spiked triacylglycerol blind duplicates (quality assurance
standards) exhibited high accuracy in the range of 0.53 to 40.69% trans and averaged a low bias of 1.3%. These statistical analysis results were compared to those collaboratively obtained by the
recently adopted AOCS Cd14-95 and AOAC 994.34 Infrared Official Methods. 相似文献
9.
High-performance liquid chromatography and spectroscopic studies on fish oil oxidation products extracted from frozen atlantic mackerel 总被引:4,自引:0,他引:4
The formation of stable hydroxy derivatives from hydroperoxides produced during the oxidation of linoleic acid methyl ester
and fish oil were studied by reverse-phase high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry
(GC-MS) and 13C nuclear magnetic resonance (NMR) spectroscopy. The oxidation products identified were mixtures of four isomeric hydroxy
derivatives: 13-hydroxy-9-cis,11-trans-octadecadienoic, 13-hydroxy-9-trans,11-trans-octadecadienoic, 9-hydroxy-10-trans,12-cis-octadecadienoic, and 9-hydroxy-10-trans,12-trans-octadecadienoic acids. The presence of hydroxy compounds was confirmed by 13C NMR, which gave rise to a hydroxy carbon peak at 87 ppm, and by GC-MS, which showed three peaks corresponding to isomeric
mixtures of trimethylsilyl ethers of the oxidized linoleic acid methyl ester. The mass spectra scans of the three peaks showed
that they represent isomers of molecular weight 382 and are consistent with the molecular formula C22H42O3Si. In oil extracted from stored frozen mackerel, 13-hydroxy-9-cis,11-trans-octadecadienoic acid was more prominent compared to the model lipid systems. HPLC offered a sensitive means of detection
of hydroxy compounds produced both in the initiation and latter stages of oxidation. The effect of antioxidants added to the
fish mince prior to storage can also be monitored by HPLC. Thus, the monitoring of lipid oxidation hydroxy derivatives by
HPLC is of practical value in the efficient processing and quality control of fish, fish oils, and other fatty foodstuffs
in order to enhance the acceptability, nutritional, and safety aspects. 相似文献
10.
The distribution of hydroperoxide isomers generated by photo-oxidation of natural lipids impregnated on the surface of dried
seaweed previously exposed to visible light and without added photosensitizer were studied. The surface of dried seaweed was
impregnated with linoleic acid methyl ester, and the sample was divided into two parts. One part was exposed to light from
a 100-W tungsten bulb (4500 lux) in a low-temperature room (5°C). The other part was kept in the dark as a control. Positional
isomers of the hydroperoxides generated from the impregnated linoleic acid methyl ester were separated individually by HPLC
and further identified by MS. The dried seaweed kept in the dark contained four hydroperoxide isomers, namely, 13-hydroperoxy-cis-9, trans-11-octadecadienoate, 13-hydroperoxy-trans-9, trans-11-octadecadienoate, 9-hydroperoxy-trans-10,cis-12-octadecadienoate, and 9-hydroperoxy-trans-10, trans-12-octadecadienoate. For the dried seaweed exposed to light, the oxidized lipids contained not only the same four isomers,
but also 12-hydroperoxy-cis-9, trans-13-octadecadienoate and 10-hydroperoxy-trans-8,cis-12-octadecadienoate. When fresh seaweed was dried in the sunlight, the formation of 12-cis,trans- and 10-cis,trans-hydroperoxides of naturally occurring methyl linoleate was verified. Dried seaweed was then impregnated with eicosapentaenoic
acid ethyl ester and exposed to light. Light exposure also generated certain hydroperoxide isomers attributable to singlet
oxygen oxidation, namely, 6-hydroperoxy-trans-4,cis-8, cis-11,cis-14,cis-17-ethyl and 17-hydroperoxy-cis-5,cis-8,cis-11, cis-14,trans-18-ethyl eicosapentaenoate. When dried sea-weed without any impregnated lipids was exposed to the light for 24 h in a cold
room (5°C), characteristic isomers, including both the 20-carbon FA isomers 6-OOH and 17-OOH as well as the 18-carbon FA isomers
10-OOH and 12-OOH, were detected in the light-exposed sample but were not found in the control. These results clearly show
that singlet oxygen oxidation of lipids occurred in the seaweed exposed to light. We concluded that this lipid oxidation was
catalyzed by chlorophyll as a photosensitizer in seaweed. 相似文献
11.
Magdi M. Mossoba Martin P. Yurawecz Richard E. McDonald 《Journal of the American Oil Chemists' Society》1996,73(8):1003-1009
A Fourier transform infrared spectroscopy procedure is described for quantitating the levels of totalrans triglycerides or their fatty acid methyl ester derivatives in neat fats and oils. It requires either warming or no preparation
of the laboratory sample, and about 5 min for spectroscopic measurement, band area integration, and calculation of thetrans content from a linear regression equation. To eliminate the strongly sloping background of the 966-cm−1
trans band, the single-beam spectrum of thetrans-containing fat is “ratioed” against that of an unhydrogenated oil or a reference material that contains onlycis double bonds. Thus, a symmetric absorption band on a horizontal background is obtained. The area under thetrans band can then be accurately integrated between the same limits, 990 and 945 cm−1, for alltrans levels investigated. To speed up the analysis, an attenuated total reflection liquid cell was used, into which oils, melted
fats or their methyl esters were poured without weighing or quantitative dilution with the toxic and volatile carbon disulfide
solvent. Thetrans levels determined by attenuated total reflection were closer to those found by capillary gas chromatography when the hydrogenated
fat was measured against the corresponding unhydrogenated oil than when it was measured against acis reference material. Small differences were found betweentrans levels in hydrogenated fat test samples and the corresponding methyl ester derivatives (9.3 and 2.2% at about 2 and 41%trans, respectively). The lower limits of identification and quantitation were 0.2 and 1%, respectively. 相似文献
12.
Robert L. Wolff Mohamed Nour Corinne C. Bayard 《Journal of the American Oil Chemists' Society》1996,73(3):327-332
To understand thecis-trans isomerization reaction of ethylenic bonds in heated octadecatrienoic acids (occurring during industrial deodorization of
oils), we have prepared a mixture ofcis-9,cis-12,cis-15, andcis-9,cis-15 18:2 acids by partial hydrazine reduction ofcis-9,cis-12,cis-15 18:3 acid present in linseed oil. This mixture (as fatty acid methyl esters) was heated under vacuum at 270°C for 2.25
h. The two methylene-interrupted acids isomerize at a similar rate under such conditions, but the nonmethylene-interruptedcis-9,cis-15 18:2 acid remains unchanged. This means that the mechanism of isomerization does not involve a direct interaction between
the two external ethylenic bonds as previously hypothesized. The centralcis-12 ethylenic bond is apparently necessary for the isomerization of the two externalcis-9 andcis-15 ethylenic bonds. However, this bond is itself rather protected against isomerization in the originalcis-9,cis-12,cis-15 18:3 acid which is mainly isomerized totrans-9,cis-12,trans-15,cis-9,cis-12,trans-15, andtrans-9,cis-12,cis-15 18:3 acids. Thecis-9,trans-12,cis-15 18:3 isomer is less than 10% of totaltrans isomers of α-linolenic acid. As a general rule, only one of the two double bonds in a methylene-interrupted diethylenic system
can undergocis-trans isomerization when submitted to heat treatment, at least for temperatures equal to or less than 270°C. 相似文献
13.
A new conjugated linoleic acid isomer, 7 trans, 9 cis-octadecadienoic acid, in cow milk, cheese, beef and human milk and adipose tissue 总被引:1,自引:0,他引:1
Martin P. Yurawecz John A. G. Roach Najibullah Sehat Magdi M. Mossoba John K. G. Kramer Jan Fritsche Hans Steinhart Youh Ku 《Lipids》1998,33(8):803-809
The identity of a previously unrecognized conjugated linoleic acid (CLA) isomer, 7 trans, 9 cis-octadecadienoic acid (18∶2) was confirmed in milk, cheese, beef, human milk, and human adipose tissue. The 7 trans, 9 cis-18∶2 isomer was resolved chromatographically as the methyl ester by silver ion-high-performance liquid chromatography (Ag+-HPLC); it eluted after the major 9 cis, 11 trans-18∶2 isomer (rumenic acid) in the natural products analyzed. In the biological matrices in-vestigated by Ag+-HPLC, the 7 trans, 9 cis-18∶2 peak was generally due to the most abundant minor CLA isomer, ranging in concentration from 3 to 16% of total CLA. By
gas chromatography (GC) with long polar capillary columns, the methyl ester of 7 trans, 9 cis-18∶2 was shown to elute near the leading edge of the major 9 cis, 11 trans-18∶2 peak, while the 4,4-dimethyloxazoline (DMOX) derivative permitted partial resolution of these two CLA isomers. The DMOX
derivative of this new CLA isomer was analyzed by gas chromatography-electron ionization mass spectrometry (GC-EIMS). The
double bond positions were at Δ7 and Δ9 as indicated by the characteristic mass spectral fragment ions at m/z 168, 180, 194, and 206, and their allylic cleavages at m/z 154 and 234. The cis/trans double-bond configuration was established by GC-direct deposition-Fourier transform infrared as evidenced from the doublet
at 988 and 949 cm−1 and absorptions at 3020 and 3002 cm−1. The 7 trans, 9 cis-18∶2 configuration was established by GC-EIMS for the DMOX derivative of the natural products examined, and by comparison
to a similar product obtained from treatment of a mixture of methyl 8-hydroxy-and 11-hydroxyoctadec-9 cis enoates with BF3, in methanol.
Contribution number S010 from the Food Research Center, Guelph, Ontario, Canada. 相似文献
14.
Preparation, separation, and confirmation of the eight geometrical cis/trans conjugated linoleic acid isomers 8,10-through 11,13–18∶2 总被引:1,自引:0,他引:1
Klaus Eulitz Martin P. Yurawecz Najibullah Sehat Jan Fritsche John A. G. Roach Magdi M. Mossoba John K. G. Kramer Richard O. Adlof Yuoh Ku 《Lipids》1999,34(8):873-877
Conjugated linoleic acid (CLA) mixtures were isomerized with p-toluenesulfinic acid or I2 catalyst. The resultant mixtures of the eight cis/trans geometric isomers of 8,10-, 9,11-, 10,12-, and 11,13-octadecadienoic (18∶2) acid methyl esters were separated by silver ion-high-performance
liquid chromatography (Ag+-HPLC) and gas chromatography (GC). Ag+-HPLC allowed the separation of all positional CLA isomers and geometric cis/trans CLA isomers except 10,12–18∶2. However, one of the 8,10 isomers (8cis, 10trans-18∶2) coeluted with the 9trans,11cis18∶2 isomer. There were differences in the elution order of the pairs of geometric CLA isomers resolved by Ag+-HPLC. For the 8,10 and 9,11 CLA isomers, cis,trans eluted before trans,cis, whereas the opposite elution pattern was observed for the 11,13–18∶2 geometric isomers (trans,cis before cis,trans). All eight cis/trans CLA isomers were separated by GC on long polar capillary columns only when their relative concentrations were about equal.
Large differences in the relative concentration of the CLA isomers found in natural products obscured the resolution and identification
of a number of minor CLA isomers. In such cases, GC-mass spectrometry of the dimethyloxazoline derivatives was used to identify
and confirm coeluting CLA isomers. For the same positional isomer, the cis,trans consistently eluted before the trans,cis CLA isomers by GC. High resolution mass spectrometry (MS) selected ion recording (SIR) of the molecular ions of the 18∶1
18∶2, and 18∶3 fatty acid methyl esters served as an independent and highly sensitive method to confirm CLA methyl ester peak
assignments in GC chromatograms obtained from food samples by flame-ionization detection. The high-resolution MS data were
used to correct for the nonselectivity of the flame-ionization detector. 相似文献
15.
Bengt Åndersson Wayne H. Anderson Jacques R. Chipault Eldon C. Ellison Stuart W. Fenton Joanne L. Gellerman John M. Hawkins Hermann Schlenk 《Lipids》1974,9(8):506-511
Lipids of the moss,Ceratodon purpureus, yield up to 25% of an acetylenic acid which was identified as allcis-9,12,15-octadecatrien-6-ynoic acid. The methyl ester of this acid was isolated in 95% purity by gas liquid chromatography.
Mass spectroscopy provided the mol wt and confirmed methyl stearate as product of hydrogenation. Ozonization indicated a triple
bond in position 6 and a double bond in position 15. UV and IR spectra showedcis-double bonds, no conjugation, and notrans-double bonds. The Raman spectrum provided direct evidence for the triple bond and confirmed the presence of double bonds
and the absence of conjugation. The ratio of intensities indicated 1 triple bond/3 double bonds. 9,12,15-Octadecatrien-6-ynoic
acid has not previously been isolated from biological materials. It was found only in the triglycerides ofCeratodon purpureus and several other mosses. In contrast to arachidonic and eicosapentaenoic acids, the acetylenic acid seems to be restricted
to few moss genera. 相似文献
16.
Column chromatography on silver ion-saturated Amberlyst XN 1010 cation exchange resin gave very good separation of a mixture
of methyl 12-hydroxy-cis-andtrans-9-octadecenoates and of methylthreo-12, 13-dihydroxy-cis- andtrans-9-octadecenoates. Comparison of the retention volumes of nonhydroxy, monohydroxy, and dihydroxy saturated and monoenoic methyl
esters and of dienoic methyl esters shows that the hydroxy group interacts with the column packing to slow passage of the
compound through the column, although the effect of a hydroxy group is less than that of atrans double bond. The effects of the hydroxy groups are additive; the ratio of retention volumes of dihydroxy ester to monohydroxy
ester is slightly larger that that of monohydroxy ester to nonhydroxy ester. The retention volume of a cis monoenoic ester
is equal to that of a hydroxytrans monoenoic ester and that of a hydroxycis monoenoic ester is equal to that of a dihydroxytrans monoenoic ester. 相似文献
17.
A simple method of preparation of methyl trans-10,cis-12- and cis-9,trans-11-octadecadienoates from methyl linoleate 总被引:2,自引:0,他引:2
O. Berdeaux L. Voinot E. Angioni P. Juanéda J. L. Sébédio 《Journal of the American Oil Chemists' Society》1998,75(12):1749-1755
Pure conjugated isomers of linoleic acid were prepared on a large scale by alkali-isomerization of purified methyl linoleate.
The methyl esters of alkali-isomerized linoleic acid contained mainly the methyl cis-9,trans-11- and trans-10,cis-12-octadecadienoates (44 and 47%, respectively). These two isomers were then separated and purified by a series of low-temperature
crystallizations from acetone. The isomeric purity obtained for the cis-9,trans-11-octadecadienoate isomer was >90% and that of the trans-10,cis-12-octadecadienoate isomer was 89 to 97%. The isolated yield of the two isomers corresponded to 18 and 25.7%, respectively,
of the starting material. The structure of the two isomers was confirmed using partial hydrazine reduction, silver nitrate-thin-layer
chromatography of the resulting monoenes and gas chromatography coupled with mass spectrometry of the 4,4-dimethyloxazoline
derivatives. Fourier transform infrared spectroscopy of the monoenes gave the confirmation of the geometry of each double
bond. 相似文献
18.
Akio Kobayashi Shigeo Morimoto Yoshiari Shibata Kyohei Yamashita Makoto Numata 《Journal of chemical ecology》1980,6(1):119-131
cis-Dehydromatricaria ester (cis-DME) inSolidago altissima, andcis-matricaria ester (cis-ME),trans-matricaria ester (trans-ME), andcis-lachnophyllum ester (cis-LE) inErigeron spp. show strong growth inhibitory effects on other plants. Thecis- andtrans-DMEs were found in soil at the border ofS. altissima communities in concentrations that were inhibitory to test plants. Among four species ofErigeron, the most dominant plant,E floribundus, showed the highest concentrations of the esters. From the results of our experiments, we conclude that these polyacetylenes are probably allelopathic substances with ecological importance. 相似文献
19.
The organoiron complex 4 is readily prepared from α-bromopyruvic ester diethyl acetal, and has been shown to serve as an effective α-acrylic ester cation equivalent, in the synthesis of α-methylene-γ-lactones. Cyclohexanone lithium enolate is transformed to either the cis or trans fused lactones 12c , t, and ethyl acetoacetate lithium enolate can be converted to the lactone 21 t. The use of methyl 3-oxohexadecanoate as starting material provides a stereospecific synthesis of protolichesterinic acid methyl ester. 相似文献
20.
Methyl 8-[2-(cis-pent-2′-enyl)-3-oxo-cis-cyclopent-4-enyl] octanoate (I) is the methyl ester of a cyclic fatty acid synthesized enzymically from an incubation of
linolenic acid with an extract of flaxseed (Linum usitatissimum L.). A proposed trivial name for I is methyl 12-oxo-cis-10, 15-phytodienoate (12-oxo-PDA). The evidence presented indicated that compound I has thecis configuration of the carbon chains with respect to the cyclopentenone ring. Treatment with acid, base, or heat isomerized
I to a second product (II) that has thetrans configuration of the carbon chains. Prolonged heat treatment of II yielded a third cyclic product, methyl 12-oxo-9(13),cis-15-phytodienoate (III). 相似文献