Wax esters of n-3 polyunsaturated fatty acids: A new stable formulation as a potential food supplement. 1 - Digestion and absorption in rats

Fish oils (FO) and their ethyl ester derivatives (EE) are proposed as rich sources of n-3 polyunsaturated fatty acids (PUFA), in view of their nutritional and therapeutic effects. However, they have drawbacks due to their high degree of susceptibility to oxidation, both during manufacturing and in living organisms. We prepared wax esters (WE) by transesterification of stoichiometric amounts of ethyl esters enriched with n-3 PUFA and long-chain alcohols (18-22 carbon atoms). They are waxy solids, with melting points from 30 to 52°C, depending on the degree of unsaturation in the acidic and alcoholic moieties of the molecules. We studied their bioavailability in comparison with commercially available products, namely EE and FO, using an animal model (rat). WE have a low degree of susceptibility to oxidation and a high degree of enzymatic hydrolysis in vitro. After an oral load, rats hydrolyse and absorb WE to a greater extent than EE, resulting in significant enrichment of n-3 PUFA in plasma triglycerides. After dietary supplementation with WE (0.15 g/d/rat) for 4 weeks, n-3 PUFA in plasma phospholipid were comparable to those of rats receiving diets supplemented with FO and EE in equimolar concentrations of n-3 PUFA. Body weight, lipid profile and intestinal transit were not affected by 4 weeks' treatment with WE. These formulations offer a potential advantage as food supplements over products in current use, on account of their greater stability.