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1.
The hydroperoxides in oxidized mixtures of methyl oleate, linoleate and linolenate were analyzed by reducing the hydroperoxides
to the corresponding hydroxyesters and separating the hydroxyesters from the unoxidized esters by thin layer chromatography
(TLC). The hydroxyesters from linolenate were separated from the other hydroxyesters by TLC on silver ion plates. The hydroxyesters
were converted to TMS-hydroxy derivatives. The TMS-hydroxyoleate and TMS-hydroxylinoleate were separated by gas chromatography
(GC), and all the TMS-derivatives were quantified by GC. The relative rates of oxidation of methyl oleate, linoleate and linolenate
in mixtures were ca. 1∶10.3∶21.6. The hydroperoxides formed in the oxidation of soybean and olive oils were similar before
and after randomization and similar to corresponding methyl ester mixtures.
Journal Paper No. J-9657 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project 2143. 相似文献
2.
To clarify the sources of undesirable flavors, pure hydroperoxides from autoxidized and photosensitized oxidized fatty esters
were thermally decomposed in the injector port of a gas chromatograph-mass spectrometer system. Major volatile products were
identified from the hydroperoxides of methyl oleate, linoleate and linolenate. Although the hydroperoxides from autoxidized
esters are isomerically different in position and concentration than those from photosensitized oxidized esters, the same
major volatile products were formed but in different relative amounts. Distinguishing volatiles were, however, produced from
each type of hydroperoxide. The 9- and 10-hydroperoxides of photosensitized oxidized methyl oleate were thermally isomerized
in the injector port into a mixture of 8-, 9-, 10- and 11-hydroperoxides similar to that of autoxidized methyl oleate. Under
the same conditions, the hydroperoxides from autoxidized linoleate and linolenate did not undergo significant interconversion
with those from the corresponding photosensitized oxidized esters. The compositions of the major volatile decomposition products
are explained by the classical scheme involving carboncarbon scission on either side of alkoxy radical intermediates. Secondary
reactions of hydroperoxides are also postulated, and the hydroperoxy cyclic peroxides from methyl linoleate (photosensitized
oxidized) and methyl linolenate (both autoxidized and photosensitized oxidized) are suggested as important precursors of volatiles. 相似文献
3.
A high pressure liquid chromatography (HPLC) method is described for the determination of the isomeric hydroxysterates from
hydroperoxides of oxidized fatty esters. The samples are hydrogenated and the mixtures of hydroxystearates are concentrated
by partial removal of unoxidized esters and complete removal of polar materials. Isomeric hydroxystearates are then separated
on a porous microparticulate adsorption (10 μ) column and elution with 0.25% isopropyl alcohol inn-hexane is monitored at 212 nm. The 8-OH, 9-OH, 10-OH, 11-OH and 16-OH isomers were completely separated, but the 12-OH, 13-OH
and 15-OH were only partly resolved by HPLC. The relative percentages of isomeric hydroxy esters were analyzed quantitatively
by a computer integration method. Accuracy of the method was checked with known mixtures of synthetic hydroxystearates. The
isomeric hydroperoxide composition of oxidized methyl oleate, linoleate, linolenate and soybean methyl esters determined by
HPLC were in good agreement with previous analyses by gas chromatography-mass spectrometry.
Presented at ISF-OACS Meeting, New York, NY, April 27–May 1, 1980. 相似文献
4.
R. W. Riemenschneider D. H. Wheeler 《Journal of the American Oil Chemists' Society》1939,16(11):219-221
Summary Iodine numbers by the Hanus and Wijs methods and thiocyanogen numbers using various absorption periods, were determined on
methyl oleate and methyl linoleate and on mixtures of these esters. It is concluded that iodine numbers by the Wijs method
and three-hour thiocyanogen numbers are more satisfactory for methyl linoleate and for mixtures containing large amounts of
this ester.
Small amounts of higher saturated acids were determined with a precision of about 0.1 unit-percent by means of the Bertram
procedure. A purified specimen of methyl oleate was found to contain about 0.2 percent of saturated ester by this method.
Food Research Division Contribution No. 428. 相似文献
5.
The mixture of conjugated diene hydroperoxide isomers obtained from autoxidation of methyl linoleate was separated by high
performance liquid chromatography (HPLC). Four major isomers were obtained from adsorption chromatography and identified as
the 9 and 13 positional isomers having thetrans-trans andcis-trans configurations. The latter geometrical isomers have thetrans double bond adjacent to the hydroperoxide group. The hydroxy compounds (methyl hydroxylinoleates) obtained from the hydroperoxides
by NaBH4 reduction were similarly separated but with improved resolution. This is the first instance of the complete separation of
these compounds and provides a rapid method for their analysis. Unlike adsorption chromatography, reversed-phase chromatography
separates the mixtures only according to the geometrical isomerism of the double bonds and not according to the position of
the hydroxy or hydroperoxide function. 相似文献
6.
Structure of monohydroperoxides formed by chlorophyll photo-sensitized oxidation of methyl linoleate
The structures of the hydroperoxides prepared by photochemical oxidation of methyl linoleate in the presence of chlorophyll
were determined by gas liquid chromatography-mass spectrometry (GLC-MS) of the trimethylsilyl (TMS) derivatives of the hydroxyesters.
The position of the double bonds were deduced via hydroxylation with OsO4, followed by GLC-MS analysis of the TMS derivatives. Structures of the original hydroperoxides were elucidated from these
data.
One of 28 papers presented at the Symposium “Metal-Catalyzed Lipid Oxidation,” ISF-AOCS World Congress, Chicago, September
1970. 相似文献
7.
A. W. Schwab W. K. Rohwedder L. W. Tjarks L. E. Gast 《Journal of the American Oil Chemists' Society》1973,50(9):364-366
Sulfur compounds derived from photochemical addition of hydrogen sulfide to methyl oleate and linoleate were separated by
preparative gas chromatography. The major compounds were investigated by NMR, mass and IR spectroscopy and by elemental analysis.
The primary product of the methyl oleate reaction was methyl 9(10)-mercaptostearate. Gas chromatograms of the product from
methyl linoleate showed four principal peaks. From mass spectra and NMR data, we identified methyl 9-(2-pentyl-1-thiolan-5-yl)nonanoate,
methyl 8-(2-hexyl-1-thiolan-5-yl)octanoate and methyl 9-(3-hexyl-1,2-dithiolan-5-yl)nonanoate. Evidence for the formation
of methyl mercapto-octadecenoates and methyl dimercaptostearates was also obtained.
ARS, USDA. 相似文献
8.
The mixture of diene hydroperoxides from methylene blue-sensitized oxidation of methyl linoleate was reduced with NaBH4 and the resulting alcohols were separated by high pressure liquid chromatography (HPLC). Four diene alcohols were isolated
in approximately equal yields from adsorption and reversed phase HPLC; the isomers were identified as methyl esters of 9-hydroxy-10,12-,
10-hydroxy-8,12-, 12-hydroxy-9,13- and 13-hydroxy-9,11-octadecadienoate. Formation of equal yields of both conjugated and
nonconjugated diene alcohols from methyl linoleate is characteristic of singlet oxygen oxidations. The detection of the easily
separated nonconjugated isomer methyl 10-hydroxy-trans-8,cis-12-octadecadienoate from methyl linoleate is proposed as a test to probe the involvement of singlet oxygen in biological
oxidations.
A preliminary report of these results was presented at the 177th meeting of the American Chemical Society, Honolulu, HI, April
1–6, 1979; see abstracts of papers, paper No. ORGN-375. 相似文献
9.
E. N. Frankel W. E. Neff W. K. Rohwedder B. P. S. Khambay R. F. Garwood B. C. L. Weedon 《Lipids》1977,12(11):908-913
The gas chromatography-mass spectrometry (GC-MS) approach developed in the preceding paper was applied for qualitative and
quantitative investigations of autoxidation products of methyl linoleate. A GC-MS computer summation method was standardized
with synthetic 9- and 13-hydroxyoctadecanoate. Equal amounts of 9- and 13-hydroperoxides were found in all samples of linoleate
autoxidized at different temperatures and peroxide levels. The results are consistent with the classical free radical mechanism
of autoxidation involving a pentadiene intermediate having equivalent sites for oxygen attack at carbon-9 and carbon-13. Minor
oxygenated products of autoxidation indicated by GC-MS include keto dienes, epoxyhydroxy monoenes di- and tri-hydroxy monoenes.
These hydroxy compounds are presumed to be present in the form of hydroperoxides. The quantitative GC-MS method was found
suitable for the analysis of autoxidized mixtures of oleate and linoleate. By this method, it is possible to determine the
origin of the hydroperoxides formed in mixtures of these fatty esters.
Presented at the AOCS Meeting, Chicago, September 1976. 相似文献
10.
A previous study of autoxidation products by high pressure liquid chromatography (HPLC) of methyl oleate and linoleate was
extended to methyl linolenate. Autoxidized methyl linolenate was fractionated by HPLC either after reduction to allylic alcohols
on a reverse phase system, or directly on a micro silica column. Isolated oxidation products were characterized by thin layer
and gas liquid chromatography and by ultraviolet, infrared, nuclear magnetic resonance and mass spectrometry. Secondary products
from the autoxidation mixtures (containing 3.5–8.5% monohydroperoxides) included epoxy unsaturated compounds (0.2–0.3%), hydroxy
or hydroperoxy-cyclic peroxides (3.8–7.7%), epoxy-hydroxy dienes (<0.1%), dihydroxy or dihydroperoxides with conjugated diene-triene
and conjugated triene systems (0.9–2.9%). Cyclization of the 12- and 13-hydroperoxides of linolenate would account for their
lower relative concentration than the 9- and 16-hydroperoxides. Dihydroperoxides may be derived from the 9- and 16-linolenate
hydroperoxides. Cyclic peroxides and dihydroperoxides are suggested as important flavor precursors in oxidized fats. 相似文献
11.
The oxidation kinetics of conjugated methyl linoleate was compared with that of non-conjugated methyl linoleate under mild
oxidation conditions (30 °C in the dark). Samples of methyl 9-cis,11-trans-linoleate, methyl 10-trans,12-cis linoleate and methyl 9-cis,12-cis linoleate were assayed separately and in mixtures. For comparative purposes, methyl α-linolenate and methyl oleate were also
used. Two complementary analytical approaches were selected to monitor the progress of oxidation, (1) the traditional follow-up
of residual substrate by gas liquid chromatography, and (2) an analytical procedure by high-performance size-exclusion chromatography
(HPSEC) for direct measurement of the oxidation compounds formed. The HPSEC method enabled us to quantitate oxidized monomers,
dimers and polymers concomitantly in a rapid and direct analysis. Results showed that conjugated methyl linoleate samples
oxidized later than their non-conjugated counterparts, and showed a very different oxidation pattern. Thus, formation of oxidized
monomers was negligible and the first and major compounds formed were polymerization products. Also, under the conditions
used, non-conjugated and conjugated methyl linoleate samples in 1:1 mixtures led to decreased oxidation rate of non-conjugated
methyl linoleate and increased oxidation rate of conjugated methyl linoleate. This study supports the view that oxidation
kinetics of conjugated dienes differ substantially from that of methylene-interrupted dienes. 相似文献
12.
Inhibition of Hydroperoxy-, Keto- and Hydroxy-FAME by Alpha- and Delta-Tocopherol at Rancimat Conditions
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Susana Marmesat Arturo Morales M. Victoria Ruiz-Méndez Gloria Márquez-Ruiz Joaquín Velasco 《Journal of the American Oil Chemists' Society》2016,93(1):93-103
The effects of α‐ and δ‐tocopherol on inhibition of hydroperoxides, keto and hydroxy compounds under Rancimat conditions, i.e. 100 °C and air bubbling, were studied in samples of fatty acid methyl esters (FAME) obtained from high linoleic (HL) and high oleic (HO) sunflower oils. Primary hydroperoxides from methyl linoleate and methyl oleate and secondary keto and hydroxy compounds derived from methyl linoleate hydroperoxides were analyzed by HPLC–UV‐ELS. Different tocopherol concentrations, namely, 10, 50, 100, 500 and 1000 mg/kg, were tested. Irrespective of the lipid substrate and the initial concentration of tocopherol, results showed that the content of hydroperoxides accumulated during the induction period was remarkably higher in the samples containing δ‐tocopherol. The relative concentrations of oleate hydroperoxides in the HO samples were also higher in the presence of δ‐tocopherol. α‐Tocopherol was more effective in inhibiting hydroperoxides at low levels, with 100 mg/kg as optimal concentration, while δ‐tocopherol displayed optimal protection at 1000 mg/kg. Under the oxidation conditions applied, neither α‐ nor δ‐tocopherol showed a protective effect on hydroperoxide decomposition at any level assayed. Formation of keto‐ and hydroxy‐dienes was more related to the concentration of their hydroperoxide precursors. Furthermore, both tocopherols gave rise to increased concentrations of ketodienes at 500 and 1000 mg/kg compared to the controls. Such an effect was more pronounced for α‐tocopherol and in the HL samples. 相似文献
13.
N. A. Khan W. E. Tolberg D. H. Wheeler W. O. Lundberg 《Journal of the American Oil Chemists' Society》1954,31(11):460-466
- It has been confirmed that the principal products formed in the oxidation of methyl oleate by oxygen under a variety of conditions are predominantlytrans hydroperoxides. However no inversion of the double bond occurs in unoxidized oleate. Hence the conversion ofcis totrans double bonds and peroxide formation occur together in the same molecules.
- The autoxidation of methyl linoleate at low temperature yields predominantlycis,trans conjugated hydroperoxides. Autoxidation at 25°C., oxidation catalyzed by visible light, or ultraviolet light and copper soap catalyzed oxidation at temperatures appreciably above 0°C., lead to the formation primarily oftrans,trans conjugated hydroperoxides. The inversion of the second double bond in this case appears to be independent of the peroxide-forming reactions.
- The photochlorophyll oxidation of methyl linoleate leads to the formation of some unconjugated hydroperoxides, some of which containtrans double bonds.
- Under all of the conditions employed in the present investigation, the oxidation of methyl oleate and linoleate led primarily to the formation of monomeric peroxides which retained most of the unsaturation of the parent compound.
14.
A comparison between the determination of the peroxide value by the methods of Wheeler and Sully (iodometric titration) and
that of Stine, et al. (ferric thiocyanate method) was made. Some oxidized vegetable oils, H2O2, t-butyl hydroperoxide, cumene hydroperoxide, methyl oleate hydroperoxides, and methyl linoleate hydroperoxides were used
as substrates. One-hundred percent of the methyl linoleate hydroperoxides were recovered by the Wheeler reduction, 85% by
the Sully method. The Wheeler method was used to reduce the methyl linoleate hydroperoxides to the corresponding hydroxy acids.
In the Sully procedure, the hydroxy acids are only intermediates which are dehydrated to octadecatrienoic acids. One equivalent
methyl linoleate hydroperoxide oxidized two equivalents of I− (Wheeler) and four equivalents of Fe2+ (Stine, et al.). By way of contrast, H2O2 needs only two equivalents I− or Fe2+ for reduction. The excess consumption of reduction equivalents in the ferric thiocyanate method probably is caused by secondary
reactions of the methyl linoleate hydroperoxide acyl residue. 相似文献
15.
Ulla I. Brimberg 《Journal of the American Oil Chemists' Society》1993,70(11):1063-1067
The autoxidation of methyl oleate and oleic acid shows some differences as compared to the autoxidation of linoleate,e.g., the formation of water at an early stage. Linearization of experimental data on the autoxidation to high oxidation degrees
of methyl oleate and other monounsaturated substrates shows that the rate equations previously derived for methyl linoleate
in the range of 1–25% oxidation are valid, provided the correct expression for the remaining unreacted substrate is used.
With monounsaturated substrates, part of the oxygen is consumed by a secondary oxidation reaction almost from the beginning,
and only a certain constant fraction α of the total O2 consumption is consumed in hydroperoxide formation. The fraction α is different for methyl oleate, oleyl alcohol, oleic acid
andcis 9-octadecene, but the rate constant for the hydroperoxide formation is the same for all of them when experimental conditions
are the same. The main difference between oleate and linoleate autoxidation is the much faster decomposition of the oleate
hydroperoxides relative to their slow formation. 相似文献
16.
Limitations of the method using peroxidase activity of hemoglobin for detecting lipid hydroperoxides
The method using peroxidase activity of hemoglobin (Hb) for the determination of lipid peroxides was examined by using pure
methyl linoleate hydroperoxides, trilinoleoylglycerol hydroperoxides and egg yolk phosphatidylcholine hydroperoxides as substrates
and tetramethyl benzidine as electron donor for the peroxidase reaction of Hb. The reactivities of these substrates were quite
varied. Furthermore, some electron donors were tested for peroxidase activity of Hb, but none showed a complete reduction
of methyl linoleate hydroperoxides. From these results, it seems the Hb method needs to be carefully applied to biological
materials that contain mixtures of different types of lipid classes. 相似文献
17.
The formation of dimers was demonstrated in methyl linoleate hydroperoxides decomposed by bubbling with dry air at 30 C. The
dimer fraction isolated by gel permeation chromatography was further fractionated by successive silicic acid column and high
performance liquid chromatography. Major components were analyzed after derivatizations by gas chromatography-mass spectrometry
with several ionization methods, i.e., electron impact, chemical ionization and field desorption.
After aeration for 90 min, 1.4% of the hydroperoxides were decomposed. However, almost all of the secondary products were
dimers, while polar monomeric and low molecular products were negligible. After aeration for 390 min, both polar monomeric
(5.0%) and low molecular (0.8%) compounds formed, but dimers and polymers (18.1%) were still the major products. These results
show the importance of polymerization in the aerobic breakdown of hydroperoxides.
The dimers isolated from hydroperoxides aerated 90 min could be separated into two fractions according to their polarities.
The dimers identified usually were composed of octadecadienoate and oxygenated octadecenoate moieties crosslinked through
either ether or peroxy linkages across C-9 or C-13 positions. The oxygen-containing functional groups found in the dimers
include hydroperoxy, hydroxy and oxo groups. The polar dimers had two of these groups per molecule, while the less polar dimers
had one. The main constituents of dimers were linked through peroxy bridges and found to be similar to the dimers previously
identified in autoxidized methyl linoleate. These dimers are suggested as important intermediates in linoleate oxidation and
as precursors of flavor deterioration. 相似文献
18.
E. N. Frankel W. E. Neff W. K. Rohwedder B. P. S. Khambay R. F. Garwood B. C. L. Weedon 《Lipids》1977,12(12):1055-1061
The gas chromatography-mass spectrometry (GC-MS) method developed in the preceding papers was extended to the analysis of
autoxidation products of methyl linolenate. Four isomeric hydroxy allylic trienes with a conjugated diene system were identified
after reduction of the linolenate hydroperoxides. All eight geometrictrans,cis- andtrans, trans-conjugated diene isomers of these hydroxy allylic compounds were identified and partially separated by GC of the trimethylsilyl
(TMS) ether derivatives. The proportion found of 9- and 16-hydroperoxides was significantly higher (75–81%) than the 12- and
13-hydroperoxides (18–25%). The tendency of the 12- and 13-hydroperoxides to form cyclic peroxides, cyclic peroxidehydroperoxides,
and prostaglandin-like endoperoxides was supported by indirect evidence for the presence of 9,10,12- and 13,15,16-trihydroxyoctadecanoate
in hydrogenated derivatives of the highly oxygenated products. The quantitative GC-MS method was used to determine the relative
contribution of linolenate, linoleate, and oleate in mixtures to the formation of hydroperoxides.
Presented at the AOCS Meeting, New York, May 1977. 相似文献
19.
M. Morita M. Tanaka Y. Takayama Y. Yamamoto 《Journal of the American Oil Chemists' Society》1976,53(7):487-488
During the autoxidation of methyl linoleate, peroxide-containing substances are formed which, when added to unoxidized methyl
linoleate, will catalyze oxygen uptake. Materials active only in the presence of added metal ions (MCs) were not inactivated
during aerobic thin-layer chromatography on silicic acid or alumina but were selectively inactivated by treatment with triphenylphosphine.
Catalysts not requiring added metal ions for activity (NCs) are not affected by triphenylphosphine, but the catalytic activity
is lost during aerobic thin-layer chromatography. Autoxidized methyl linoleate was separated into four peroxide-containing
fractions by elution from a silicic acid column with hexane-diethyl ether mixtures. Each fraction was found to contain both
MCs and NCs.
Presented at the 4th International Symposium on Metal Catalyzed Lipid Oxidation, London, April 1975. 相似文献
20.
Schwab A. W. Gast L. E. Rohwedder W. K. 《Journal of the American Oil Chemists' Society》1975,52(7):236-239
Hydrogen sulfide was added to methyl oleate, methyl linoleate, and soybean oil at −70 and 25 C in the presence of boron trifluoride. Major reaction compounds were identified by gas liquid chromatography and mass spectrometry. At −70 C with a 200 molar ratio of hydrogen sulfide to ester, the reactions were complete in 4 hr. Primary reaction product from methyl oleate was methyl 9(10)-mercaptostearate. Methyl linoleate gave ca. equal amounts of methyl 9-(2-pentyl-1-thiolan-5-yl) nonanoate and methyl 8-(2-hexyl-1-thiolan-5-yl) octanoate. At 25 C, the reaction of methyl oleate and linoleate with hydrogen sulfide was less complete, and more side reactions were noted. When equimolar amounts of methyl oleate and methyl 9(10)-mercaptostearate were reacted in the presence of boron trifluoride at 25 C, a new compound was formed, bis(methyl n-octadecanoate 9[10]-yl) sulfide. The addition of liquid hydrogen sulfide to soybean oil at −70 C in the presence of boron trifluoride yields a product which, upon saponification, acidification, and methylation analyzes by gas liquid chromatography as ca. 52% thiolan, 27% mercaptostearate, 10% palmitate, 6% stearate, and 5% unidentified compounds. 相似文献