Methyl linoleate, products from

Product characterization provides further insight on the course of diene carboxylation. The monocarboxy acids were identified as methyl carboxyoctadecenoate (1) from chromatographic, IR, mass spectral, and selective hydrogenation studies. The double bond of 1 from carboxylated linoleate is 40% trans in configuration (IR), and its carboxy group is located mainly on carbon-10 and -12 positions (Table II). In contrast,... 

Figure C4.2.4 (A) SP-HPLC of methyl hydroxyoctadecadienoates obtained from linoleic acid hydroperoxide products. Peak 1, methyl 13-hydroxy-9(Z),11( )-octadecadienoate peak 2, methyl 13-hydroxy-9( ),11(E)-octadecadienoate peak 3, methyl 9-hydroxy-10(E),12(Z)-octadecadi-enoate peak 4, methyl 9-hydroxy-10( ),12( )-octadecadienoate. In this chromatogram, peaks 2 and 4 are more abundant than ordinarily encountered retention times may vary (but not the order of elution) depending on the type of silica HPLC column. (B) CP-HPLC of peak 1 from A. The 13(R)-stereoisomer elutes before the 13(S)-stereoisomer. Elution times may vary. (C) CP-HPLC of peak 3 from A. The 9(S)-stereoisomer elutes before the 9(R)-stereoisomer. Elution times may vary.

Sie67 allowed methyl linoleate to react with gaseous styrene at 28o°C and isolated an addition compound by molecular fractionation of the reaction products in the cascade fractionating still (Fig. 78). From the analytical data of the addition compound he concluded that a Diels-Alder mechanism was involved in the copolymerization reaction of styrene with the primarily conjugated linoleic ester (c/. Table XVI) ... 

Horvat, R.J., McFadden, W.H., Hawkins, N.G., Black, D.R., Lane, W.G., Teeter, R.M. 1965. Volatile products from mild oxidation of methyl linoleate. Analysis by combined mass spectrometry-gas chromatography. J. Am. Oil Chem. Soc. 42, 1112-1115. 

Hydrogenation of methyl p-eleostearate (methyl frani,fran5,fra s-9,ll,13-octadecatrienoate) with [Cr(CO)3(arene)] yields the diene products from 1,4-addition trans-9-cis- 2- and CK-10-fran5-13-oc-tadecadienoates). With a-eleostearate (methyl d5,fran5,fra i-9,ll,13-octadecatrienoate), stereoselective 1,4-reduction of the trans,trans-diene moiety yields linoleate (cis,cis-9,l2) accompanied by cm,Irani-1,4-dienes which are formed from the isomerization of a- to p-eleostearate. ... 

The carbon dioxide was supplied by Air Products and Chexxiicals, Inc., with a stated purity of 99.99% and research grade ethane was obtained from MG Industries. Crude methyl oleate (KODAK T.G. containing 65%-75% methyl oleate) was purified to 98%-99% (including methyl linoleate) using vacuum distillation. 

Ha, K.-H. and Igarashi, O. 1990. The Oxidation Products from Two Kinds of Tocopherols Co-Existing in Autoxidation System of Methyl Linoleate. J. Nutr. Sci. Vitaminol. 36 411—421. 

Makinen, M., Kamal-Eldin, A., Lampi, A.-M., and Hopia, A. 2000. Effects of a- and y-Tocopherols on Formation of Hydroperoxides and Two Decomposition Products from Methyl Linoleate. J. Am. Oil Chem. Soc. 77 801-806. 

Oleuropein appears to interfere with some biological processes such as lipoprotein oxidation, platelet aggregation, platelet and leukocyte eicosanoid production and cardiovascular control too. As previously described, oleuropein and hydroxy-tyrosol are characterised by a catechol moiety that appears to be needed for their scavenger and antioxidant activities. In fact, it was demonstrated that these compounds prevent thermally initiated autoxidation of methyl linoleate in homogenous solutions [56], protect LDL from oxidation [57] and inhibit production of... 

Polyunsaturated eompounds, such as methyl linoleate (13) and methyl linolenate (14) offer some interesting possibilities. There are three main sets of products (hydrocarbons, monoesters and diesters), identified by mass spectroscopy (MS) and listed in Table 7.3 (Ast 1976a Verkuijlen 1974, 1976). Cyclohexa-1,4-diene and traees of higher cyclopolyenes are formed. These must clearly result from secondary intramolecular metathesis reactions such as (6). 

The hypothesis of a bimolecular initiation reaction for liquid phase autoxida-tions was extended beyond cyclohexanone as a reaction partner. Also other substances featuring abstractable H-atoms are able to assist in this radical formation process. The initiation barrier was found to be linearly dependent on the C-H bond strength, ranging from 30 kcal/mol for cyclohexane to 5 kcal/mol for methyl linoleate [14, 15]. Substrates that yield autoxidation products that lack weaker C-H bonds than the substrate (e.g., ethylbenzene) do not show an exponential rate increase as the chain initiation rate is not product enhanced [16]. 

HPODE (methyl ester) was isolated from an autoxidation reaction of methyl linoleate conducted using a higher than usual amount of a-tocopherol [31]. a-Tocopherol was included in order to drive the reaction toward formation of the aUyUc 8- and 14-hydroperoxides, as had been described to occur earlier [33]. While these products were not found, the bis-sA y ic ll(9Z,12Z)-HPODE was obtained as one of the major... 

Autoxidation and photo-oxygenation are two aspects of the non-enzymic reaction between oxygen and unsaturated fatty acids. The enzymic reactions are discussed in Section 10.3. Oxidation of lipids during storage and handling, involving complex substrates and ill-defined reaction conditions, proved difficult to understand. This difficulty is enhanced by the fact that the primary oxidation products are labile and readily converted to secondary oxidation products of several kinds. Understanding of these processes has come from studies of simpler substrates such as methyl oleate or methyl linoleate under clearly defined reaction conditions. 

In contrast, methyl linoleate gives only two autoxidation products in equivalent amount. These are the 9- and 13-hydroperoxides and there is no evidence of any other hydroperoxide. These individual compounds, however, can change from Cyt to tyt dienes with exchange of the hydroperoxide group from C9 to C13 or vice versa (see following section). 

Figure 4.12. Cleavage products from 9- and 13-hydroperoxides formed by autoxidation of methyl linoleate (Frankel etaL, 1981). Relative percent values shown in parentheses are for autoxidation and photosensitized oxidation respectively ( ) = not detected.

Volatile decomposition products from autoxidized linoleic acid and methyl linoleate were characterized for their intense aroma and flavor impact by capillary gas chromatography-olfactometry. This technique involves sniffing the gas chromatograph effluent after stepwise dilution of the volatile extract. The most intense volatiles included hexanal, c/ -2-octenal, /ra. s-2-nonenal, l-octene-3-one, 3-octene-2-one and trans-l-ociQmX (Table 4.2). This analytical approach does not, however, consider the effects of complex interactions of volatiles occurring in mixtures produced in oxidized food lipids. 

The hydroperoxy epidioxides formed from photosensitized oxidized methyl linoleate are important precursors of volatile compounds, which are similar to those formed from the corresponding monohydroperoxides. Thus, 13-hydroperoxy-10,12-epidioxy-tra 5 -8-enoic acid produces hexanal and methyl lO-oxo-8-decenoate as major volatiles (Figure 4.24). The 9-hydroperoxy-10,12-epidioxy-rrans-13-enoic acid produces 2-heptenal and methyl 9-oxononanoate. Other minor volatile products include two volatiles common to those formed from the monohydroperoxides, pentane and methyl octanoate, and two that are unique, 2-heptanone and 3-octene-2-one. The hydroperoxy epidioxides formed from autoxidized methyl linolenate produce the volatiles expected from the cleavage reactions of linolenate hydroperoxides, and significant amounts of the unique compound 3,5-octadiene-2-one. This vinyl ketone has a low threshold value or minimum detectable level, and may contribute to the flavor impact of fats containing oxidized linolenate (Chapter 5). 

Figure 4.24. Volatile decomposition products from hydroperoxy epidioxides of methyl linoleate oxidized with singlet oxygen (Frankel etal, 1982).

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