Stereochemistry of olefin and fatty acid oxidation. Part 3. The allylic hydroperoxides from the autoxidation of methyl oleate

Frankel, E. N.; Garwood, R. F.; Khambay, B. P. S.; Moss, G. P.; Weedon, B. C. L.

doi:10.1039/p19840002233

Cited by 46 publications

(37 citation statements)

References 5 publications

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“…1 Hz larger in the unusual cis,trans isomers than in the other geometric isomers. These findings agree with the 1 H and 13 C NMR data on cis and trans monoene allylic hydroperoxides from the autoxidation of methyl oleate Frankel et al 1984;Porter et al 1994a The 13 C N M R d a t a o n t e n p ur e C L A m e t hy l e s t e r hy d r o pe r o x i d e s e n a b l e d t h e determination of the effects of the hydroperoxyl group on the carbon chemical shifts of CLA isomers (IV , Table 2) and the determination of chemical shift differences of olefinic resonances (IV,p. 113) that may help assignment of structure to as yet unknown lipid hydroperoxides produced, for example, from other geometric and positional isomers of CLA methyl esters.…”

Section: Nmr Properties the 13 C N M R D A T A F O R T H E T E N I S supporting

confidence: 90%

“…1 Hz stronger in the unusual cis,trans hydroperoxide than in the more common cis,trans and trans,trans isomers. These findings agree with the 1 H and 13 C NMR data on hydroxy derivatives of cis and trans monoene allylic hydroperoxides from methyl oleate autoxidation Frankel et al 1984;Kim et al 2000).…”

Section: Characterization T H E P O S I T I O N O F T H E H Y D R O Xsupporting

confidence: 90%

“…Autoxidation of methyl oleate produces eight geometric isomers of 8-, 9-, 10-, and 11-hydroperoxyoctadecenoates as pairs of enantiomers (Chan & Levett 1977b;Frankel et al 1977Frankel et al , 1984. Quantification of the relative proportions of the four positional isomers as corresponding hydroxystearates by HPLC (Chan & Levett 1977b) and as trimethyl silyl ethers of the hydroxystearates by GC-MS ) showed a small preference for formation of 8-and 11-hydroperoxide isomers.…”

Section: Hydroperoxide Formation During Autoxidation Of Monoene Fattymentioning

confidence: 98%

“…Frankel et al (1984) constructed a mechanism for methyl oleate autoxidation (Fig. 4) based on the autoxidation of the simple model compound 3-cis-hexene (Frankel et al 1982).…”

Section: Hydroperoxide Formation During Autoxidation Of Monoene Fattymentioning

confidence: 99%

“…Proposed mechanism for methyl oleate autoxidation (modified from Frankel et al 1984 andFrankel 1998b); 1 Me 8-OOH-9c/Me 11-OOH-9c; 2 Me 10-OOH-8t/Me 9-OOH-10t; 3 Me 10-OOH-8c/Me 9-OOH-10c; 4 Me 8-OOH-9t/Me 11-OOH-9t.…”

Section: Figurementioning

confidence: 99%

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Autoxidation of Conjugated Linoleic Acid Methyl Ester in the Presence of α‐Tocopherol: The Hydroperoxide Pathway

Pajunen

Johansson

Hase

et al. 2008

Lipids

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The autoxidation of conjugated linoleic acid (CLA) is poorly understood in spite of increasing interest in the beneficial biological properties of CLA and growing consumption of CLA-rich foods. In this thesis, the autoxidation reactions of the two major CLA isomers, 9-cis,11-transoctadecadienoic acid and 10-trans,12-cis-octadecadienoic acid, are investigated. The results contribute to an understanding of the early stages of the autoxidation of CLA methyl ester, and provide for the first time a means of producing and separating intact CLA methyl ester hydroperoxides as well as basic knowledge on lipid hydroperoxides and their hydroxy derivatives.Conjugated diene allylic monohydroperoxides were discovered as primary autoxidation products formed during autoxidation of CLA methyl esters in the presence and absence oftocopherol. This established that one of the autoxidation pathways of CLA methyl ester is the hydroperoxide pathway.Hydroperoxides were produced from the two major CLA methyl esters by taking advantage of the effect of -tocopherol to promote hydroperoxide formation. The hydroperoxides were analysed and separated first as methyl hydroxyoctadecadienoates and then as intact hydroperoxides by HPLC. The isolated products were characterized by UV, GC-MS, and NMR techniques. In the presence of a high amount of -tocopherol, the autoxidation of CLA methyl ester yields six kinetically-controlled conjugated diene monohydroperoxides and is diastereoselective in favour of one particular geometric isomer as a pair of enantiomers. The primary autoxidation products produced from the two major CLA isomers include new positional isomers of conjugated diene monohydroperoxides, the 8-, 10-, 12-, and 14-hydroperoxyoctadecadienoates. Furthermore, two of these new positional isomers have an unusual structure for a cis,trans lipid hydroperoxide where the allylic methine carbon is adjacent to the cis instead of the usual trans double bond.The 1 H and 13 C NMR spectra of nine isomeric methyl hydroxyoctadecadienoates and of ten isomeric methyl hydroperoxyoctadecadienoates including the unusual cis,trans hydroperoxides, i.e. Me 8-OOH-9c,11t and Me 14-OOH-10t,12c, were fully assigned with the aid of 2D NMR spectroscopy. The assigned NMR data enabled determination of the effects of the hydroxyl and hydroperoxyl groups on the carbon chemical shifts of CLA isomers, identification of diagnostic signals, and determination of chemical shift differences of the olefinic resonances that may help with the assignment of structure to as yet unknown lipid hydroperoxides either as hydroxy derivatives or as intact hydroperoxides.A mechanism for the hydroperoxide pathway of CLA autoxidation in the presence of a high amount of -tocopherol was proposed based on the characterized primary products, their relative distribution, and theoretical calculations. This is an important step forward in CLA research, where exact mechanisms for the autoxidation of CLA have not been presented before. Knowledge of these hydroperoxide formation steps is of cr...

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Section: Nmr Properties the 13 C N M R D A T A F O R T H E T E N I S supporting

confidence: 90%

Section: Characterization T H E P O S I T I O N O F T H E H Y D R O Xsupporting

confidence: 90%

Section: Hydroperoxide Formation During Autoxidation Of Monoene Fattymentioning

confidence: 98%

“…Frankel et al (1984) constructed a mechanism for methyl oleate autoxidation (Fig. 4) based on the autoxidation of the simple model compound 3-cis-hexene (Frankel et al 1982).…”

Section: Hydroperoxide Formation During Autoxidation Of Monoene Fattymentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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