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Hydroperoxide formation during autoxidation of conjugated linoleic acid methyl ester
Author(s) -
Hämäläinen Taina I.,
Sundberg Susanna,
Mäkinen Marjukka,
Kaltia Seppo,
Hase Tapio,
Hopia Anu
Publication year - 2001
Publication title -
european journal of lipid science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.614
H-Index - 94
eISSN - 1438-9312
pISSN - 1438-7697
DOI - 10.1002/1438-9312(200109)103:9<588::aid-ejlt5880>3.0.co;2-l
Subject(s) - autoxidation , chemistry , conjugated linoleic acid , conjugated system , heteronuclear molecule , nuclear magnetic resonance spectroscopy , linoleic acid , ozonolysis , organic chemistry , nmr spectra database , medicinal chemistry , fatty acid , spectral line , polymer , physics , astronomy
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 D 2 O exchange and by chemoselective reduction of the hydroperoxide groups into hydroxyl groups using NaBH 4 . These experiments were followed by nuclear magnetic resonance (NMR) spectroscopy. The 13 C and 1 HNMR 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 13 CNMR 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 13 C and 1 H 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.