A1 Refereed original research article in a scientific journal
NMR properties of conjugated linoleic acid (CLA) methyl ester hydroperoxides
Authors: Pajunen TI, Koskela H, Hase T, Hopia A
Publisher: ELSEVIER IRELAND LTD
Publication year: 2008
Journal:: Chemistry and Physics of Lipids
Journal name in source: CHEMISTRY AND PHYSICS OF LIPIDS
Journal acronym: CHEM PHYS LIPIDS
Volume: 154
Issue: 2
First page : 105
Last page: 114
Number of pages: 10
ISSN: 0009-3084
DOI: https://doi.org/10.1016/j.chemphyslip.2008.05.001
Abstract
NMR data on lipid hydroperoxides is scarce. In this study, hydroperoxides were produced from methyl 9-cis, 11-trans-octadecadienoate and from methyl 10-trans,12-cis-octadecadienoate by autoxidation in the presence of 20% of alpha-tocopherol. Ten different hydroperoxides were isolated from the autoxidation mixtures of the two conjugated linoleic acid (CLA) methyl esters by SPE and HPLC. The assignment of the H-1 and C-13 NMR spectra of these hydroperoxides was accomplished by 2D NMR experiments and by spectral simulations. Substitution of a hydroperoxyl group at the allylic position in CLA methyl esters induced a 53.93 ppm downfield shift on the hydroperoxyl-bearing carbon resonance. The effects on the olefinic alpha, beta, gamma, and delta carbon resonances were -3.45, +4.96, -1.22, and +4.42 ppm, respectively. Furthermore, the solvent effects of deuterochloroform, deuteroacetone, and deuterobenzene on the C-13 resonances of the hydroperoxides suggest that deuterochloroform is the appropriate solvent for C-13 NMR studies on mixtures of lipid hydroperoxides. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
NMR data on lipid hydroperoxides is scarce. In this study, hydroperoxides were produced from methyl 9-cis, 11-trans-octadecadienoate and from methyl 10-trans,12-cis-octadecadienoate by autoxidation in the presence of 20% of alpha-tocopherol. Ten different hydroperoxides were isolated from the autoxidation mixtures of the two conjugated linoleic acid (CLA) methyl esters by SPE and HPLC. The assignment of the H-1 and C-13 NMR spectra of these hydroperoxides was accomplished by 2D NMR experiments and by spectral simulations. Substitution of a hydroperoxyl group at the allylic position in CLA methyl esters induced a 53.93 ppm downfield shift on the hydroperoxyl-bearing carbon resonance. The effects on the olefinic alpha, beta, gamma, and delta carbon resonances were -3.45, +4.96, -1.22, and +4.42 ppm, respectively. Furthermore, the solvent effects of deuterochloroform, deuteroacetone, and deuterobenzene on the C-13 resonances of the hydroperoxides suggest that deuterochloroform is the appropriate solvent for C-13 NMR studies on mixtures of lipid hydroperoxides. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
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