The distribution and relative hydrolysis of tocopheryl acetate in the different matrices coexisting in the lumen of the small intestine during digestion could explain its low bioavailability

Abstract : Scope: Vitamin E is present in feed and food mainly as d--tocopherol (d--TOL) but also as all-rac--tocopheryl acetate (rac-alpha-TAC) through supplementation. Its absorption efficiency is low compared to that of triacylglycerols. The aim of this work was thus to study the fate of TAC during digestion. Methods and results: Using an in vitro digestion model, we showed that TAC was distributed between mixed micelles (36%), liposomes (9%), and nonsolubilized food debris (52%). A significant fraction of TAC was also found in emulsions when fat hydrolysis was not complete. Among the candidate esterases tested, i.e. cholesteryl ester hydrolase, pancreatic lipase, and pancreatic lipase-related protein 2, only cholesteryl ester hydrolase was able to hydrolyze TAC to all-rac-alpha-TOL, about five times more efficiently when it was incorporated into mixed micelles or liposomes than into emulsions or in the food matrix. Caco-2 cells were able to hydrolyze TAC and to uptake TOL when TAC was incorporated into mixed micelles but not into emulsions. Conclusion: During digestion, most TAC is recovered in matrices where its hydrolysis and its uptake by intestinal cells are markedly less efficient than in mixed micelles.