Evaluation of delivery form of eicosapentaenoic and docosahexaenoic acids during quality control of fish oil supplements

Fish oils (FO) omega-3 supplements containing eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids are extensively consumed due to their beneficial health effects. Fatty acids (FA) are mainly available as triacylglycerols (TAG) and ethyl esters (EE) in FO supplements, and EE is known to be less bioavailable. Then, the evaluation of FA in FO should comprise not only omega-3 content but also the delivered form. This research aimed to approach in detail a set of chromatographic analytical methods employing TLC, GC-FID, and GC-MS for FO quality control, considering both FA contents and form. TAG and EE FA were differentiated by GC-FID, due to the difference in the retention times of compounds, and also by GC-MS, as a result of the different m/z spectra observed. TLC also distinguished both FA forms, but a mixture of TAG and EE in FO concentrates was not observed, as evidenced by GC techniques. Ten FO supplements available in the Brazilian market were analyzed, and the FA profiles of natural and concentrated FO were compared. EPA + DHA label claim compliance was also accessed. Their contents varied from 78 to 113% of labeled content, and only one supplement had FA in EE form. Brazilian FO supplements analyzed were a source of EPA and DHA and most products (except one sample) were accurately labeled according to current Brazilian regulation, which permits a variation in 20% of the declared content. Furthermore, the methodologies approached can be used in future researches considering FO analyses and bioavailability studies approaching the different FA forms.