Correlation Between 1H NMR and Traditional Methods for Determining Lipid Oxidation of Ethyl Docosahexaenoate.

Lipid oxidation includes a complex set of chemical reactions; and no single analytical method is available to give a satisfactory description of lipid oxidation status. High-resolution NMR spectroscopy techniques were tested to establish possible correlations with traditional analytical methods and to study lipid oxidation products. Ethyl esters of all-cis 4, 7,10,13,16,19-docosahexaenoic acid (DHA) (22:6n-3), with and without added α-tocopherol, were oxidized in the dark at 25°C in an air-circulating oven. Correlations were found between primary oxidation products (PV and conjugated dienes) and the appearance of peaks in the 8.0-10.5 ppm chemical shift region of the ¹H NMR spectra. Multivariate data analysis (partial least squares; principal component regression) and the study of specific regions of the spectra obtained made it possible to easily separate samples of esters with and without α-tocopherol based on the oxidation products formed. Based on knowledge about lipid oxidation products formed in marine lipids, selected oxidation products have been studied in the ¹H NMR spectra with the aim of finding detection limits and their chemical shift values. [ABSTRACT FROM AUTHOR]