In-Vitro Dynamic Bioaccessibility and Bioavailability as Key Parameters for Rational Engineering of Novel Curcumin Delivery Systems

The healthy properties of a functional food not only depend on its content in bioactive compounds—such as curcumin—but also on the changes that it undergoes during the digestive process that affect its bioaccessibility and bioavailability. This research aims to study oral in vitro bioaccessibility and bioavailability as key design variables for the rational design of three novel delivery systems (oleogel vs. Og/W simple emulsion vs. W1/Og/W2 multiple emulsion) with the dual purpose of facilitating the transport and controlled release of curcumin and simultaneously encapsulating and safeguarding the carried lipid phase (ω-3 PUFAs) against oxidation processes (the latter was previously optimized). To this end, a dynamic in vitro simulating system (SimuGIT) was used to mimic the release and absorption mechanisms throughout the gastrointestinal tract, including the oral (2 min), gastric (30 min) and intestinal phases (180 min). The oleogelified (not emulsified) system turned out to be the least bioaccessible and bioavailable, although the most promising strategy in terms of efficiency once released, with 41.8 ± 1.8% of the bioaccessible curcumin after the digestion phase being bioavailable at the end of the gastrointestinal tract. On the other hand, both emulsified systems, Og/W and W1/Og/W2, showed similar final bioavailability up to the colonic simulated stage of around 20.2 ± 2.5%, 1.7 times higher than that of the oleogel (p < 0.05) and 2.5 greater as compared to other in vitro values reported in the literature for free curcumin. Surprisingly, the curcumin in the W1/Og/W2 multiple emulsion was absorbed faster than the one vectorized in the Og/W system; thus, in terms of net values, both Og/W and W1/Og/W2 emulsions provided the same bioavailable curcumin. However, in terms of controlled release, the multiple emulsion would be the most suitable encapsulation system for rapid delivery, and the single emulsion for longer-term release applications. Thus, information obtained from this study could be useful in designing functional foods for the controlled delivery of lipophilic bioactive compounds.