Abstract
Multicomponent high-resolution 1H and 13C NMR analysis has been employed for the purpose of detecting and quantifying a wide range of fatty acids (as triacylglycerols or otherwise) in encapsulated marine cod liver oil supplements. The 1H NMR technique provided quantitative data regarding the docosahexaenoic acid content of these products, which serves as a valuable index of fish oil quality, and a combination of both 1H and 13C spectroscopies permitted the analysis of many further components therein, including sn-1 monoacylglycerols, sn-1,2 and -1,3 diacylglycerol adducts, together with a range of minor components, such as trans-fatty acids, free glycerol and cholesterol, and added vitamins A and E. The identities of each of the above agents were confirmed by the application of two-dimensional 1H-1H spectroscopies. The NMR techniques employed also uniquely permitted determinations of the content of nonacylglycerol forms of highly unsaturated (or other) fatty acids in these products (i.e., ethyl esters), and therefore served as a means of distinguishing "natural" sources of cod liver oils from those subjected to chemical modification to and/or supplementation with synthetic derivatives such as ethyl docosahexaenoate or eicosopentaenoate. The analytical significance and putative health effects of the results acquired are discussed.
Highlights
Multicomponent high-resolution 1H and 13C NMR analysis has been employed for the purpose of detecting and quantifying a wide range of fatty acids in encapsulated marine cod liver oil supplements
The F␣ and F methylene (-CH2-) groups (C2 and C3 positions, respectively) located between the deshielding carboxylic acid function {esterified to glycerol [1(3)- or 2-positions] or otherwise} and the C4–C5 position double bond of DHA exclusively give rise to 1H NMR signals downfield of and well resolved from those arising from the C2 (F␣) -CH2- groups of all the other fatty acids (Fig. 1), and this phenomenon readily permits the quantification of DHA in the fish oil supplements examined here, both as a molar proportion of all fatty acids present and as mol·kgϪ1 or mg·gϪ1 units as outlined in the Materials and Methods section
Expression of the 0.940 ppm resonance intensity to that corresponding to the sum of both the terminal-CH3 group signals provides a useful index regarding the ratio of total n-3 to non-n-3 fatty acids, and the molar percentage of the former present in the samples examined
Summary
Multicomponent high-resolution 1H and 13C NMR analysis has been employed for the purpose of detecting and quantifying a wide range of fatty acids (as triacylglycerols or otherwise) in encapsulated marine cod liver oil supplements. With respect to coronary heart disease, the protective actions of these highly unsaturated fatty acids (HUFAs) were originally believed to be ascribable to their roles in impairing platelet function [5], and two in vivo investigations have shown that the feeding of fish oils to animals markedly alleviated platelet accumulation at sites of arterial injury [6] These n-3 fatty acids have been demonstrated to exert many striking effects on cellular function that indicate their anti-atherosclerotic, anti-inflammatory and antithrombotic properties [7,8,9], the inhibition of leukotriene synthesis, protein kinase C activity, and cellular adhesion to surfaces, the stimulation of nitric oxide synthesis (a phenomenon causing vasodilation), and impairment of the production of inflammatory cytokines (e.g., interleukin-1 and tumor necrosis factor) by monocytes. It should be noted that the antithrombotic and vasodilatory actions exerted by n-3 fatty acids may enhance local myocardial oxygen supply, a process that would synchronously diminish the possibility of arrhythmia
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