Antioxidative Effect of Dihydrosphingosine (d18:0) and α-Tocopherol on Tridocosahexaenoin (DHA-TAG).

Sphingoid bases have shown promise as effective antioxidants in fish oils together with α-tocopherol, and the effect has been attributed to products resulting from amino-carbonyl reactions (lipation products) between the sphingoid base amine group and carbonyl compounds from lipid oxidation. In this study, the synergistic effect of dihydrosphingosine (d18:0) and α-tocopherol was studied on pure docosahexaenoic acid (DHA) triacylglycerols with an omics-type liquid- and gas-chromatographic mass spectrometric approach to verify the synergistic effect, to get a comprehensive view on the effect of d18:0 on the oxidation pattern, and to identify the lipation products. The results confirmed that d18:0 rapidly reacts further in the presence of lipid oxidation products and α-tocopherol. α-Tocopherol and d18:0 showed an improved antioxidative effect after 12 h of oxidation, indicating the formation of antioxidants through carbonyl-amine reactions. Imines formed from the carbonyls and d18:0 could be tentatively identified.

Lipid Structure Influences the Digestion and Oxidation Behavior of Docosahexaenoic and Eicosapentaenoic Acids in the Simulated Digestion System.

Omega-3 fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are essential for human health but prone to oxidation. While esterification location is known to influence the stability of omega-3 in triacylglycerols (TAGs) in oxidation trials, their oxidative behavior in the gastrointestinal tract is unknown. Synthesized ABA- and AAB-type TAGs containing DHA and EPA were submitted to static in vitro digestion for the first time. Tridocosahexaenoin and DHA as ethyl esters were similarly digested. Digesta were analyzed by gas chromatography, liquid chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy. Besides the formation of di- and monoacylglycerols, degradation of hydroperoxides was detected in ABA- and AAB-type TAGs, whereas oxygenated species increased in tridocosahexaenoin. Ethyl esters were mainly unaffected. EPA was expectedly less susceptible to oxidation prior to and during the digestion process, particularly in sn-2. These results are relevant for the production of tailored omega-3 structures to be used as supplements or ingredients.

Docosahexaenoic acid in regio- and enantiopure triacylglycerols: Oxidative stability and influence of chiral antioxidant.

Docosahexaenoic acid (DHA) is essential for health but easily oxidized. Yet the influence of DHA's exact location (sn-1, sn-2, or sn-3) in triacylglycerols on oxidative stability is currently unknown. This is the first study comparing oxidative stability of DHA in regio- and enantiopure triacylglycerols with or without RRR-α-tocopherol. Headspace solid-phase micro-extraction with gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy were applied. DHA in sn-2 was the most stable with or without added RRR-α-tocopherol resulting in differences in hydroperoxide formation. Without antioxidant, stability of DHA in sn-1 and sn-3 was mainly similar, with slight tendency towards better stability in sn-3. With RRR-α-tocopherol higher stability in sn-1 compared to sn-3 was observed. This points to diastereomeric interactions between RRR-α-tocopherol and DHA in sn-1. These results are highly relevant for enzymatic restructuring processes of DHA-rich fish or microalgae oil concentrates aimed for food supplements or food fortification.

Oxidative stability, oxidation pattern and α-tocopherol response of docosahexaenoic acid (DHA, 22:6n-3)-containing triacylglycerols and ethyl esters.

DHA is most often used in supplements either in its triacylglycerol or ethyl ester form. Currently, there is only little published data on the differences in the oxidative stability and α-tocopherol response between the two lipid structures, as well as on the oxidation patterns of pure DHA. This study investigated the oxidative stability, α-tocopherol response and oxidation pattern of DHA incorporated in triacylglycerols and as ethyl esters with an untargeted approach after oxidation at 50 °C in the dark. Liquid and gas chromatographic methods with mass spectrometric detection and nuclear magnetic resonance spectroscopy were applied. DHA was more stable in triacylglycerols than as ethyl esters without α-tocopherol addition. With α-tocopherol added the opposite was observed. The oxidation products formed during triacylglycerol and ethyl ester oil oxidation were mostly similar, but also some structure-related differences were detected in both volatile and non-volatile oxidation products.

Evaluation of the composition and oxidative status of omega-3 fatty acid supplements on the Finnish market using NMR and SPME-GC-MS in comparison with conventional methods.

Previous studies disagree on the oxidative status of omega-3 supplements. The great deviation raises concerns about quality and the methods used to monitor it. This study investigated 49 omega-3 products for their fatty acid content, lipid class and oxidative status using official methods, gas and liquid chromatography with mass spectrometry and nuclear magnetic resonance spectroscopy. With minor deviations, omega-3 fatty acid content and lipid class of all products were as declared. 24% of studied products exceeded thresholds set by The Global Organization for EPA and DHA Omega-3s for peroxide and/or p-anisidine value suggesting a compromised oxidative status. However, peroxide and/or p-anisidine value were only suitable for detection of lipid oxidation in 90% or 73%, respectively, of the products. Analysis of volatile oxidation compounds can be an alternative method for p-anisidine value. Nuclear magnetic resonance spectroscopy was shown to be a rapid method for determination of oil type and lipid class.