Programmed Sequential Release Behavior and Bioavailability of Curcumin and Fucoxanthin Co-Encapsulated in Solid-In-Oil-In-Water Multilayer Emulsions

Food-grade co-delivery systems have garnered significant attention for their ability to deliver two or more bioactive components simultaneously. Co-delivery systems possessing programmed sequential release properties allow sequential delivery of bioactive components to different sites in the gastrointestinal tract (GIT) to enhance their bioavailability. This study constructed solid-in-oil-in-water multilayer emulsions (S/O/W-E) using carboxymethyl konjac glucomannan-coated gliadin nanoparticles as the solid phase, coconut oil as the oil phase, and carboxymethyl starch/propylene glycol alginate complexes as the aqueous phase, which realized the co-encapsulation of curcumin (Cur) and fucoxanthin (FUC) and their programmed sequential release in the GIT. The programmed sequential release behavior of S/O/W-E was further evaluated by in vitro digestion models. It was demonstrated that both Cur and FUC released less than 16.5% in simulated gastric fluid, following a Fickian diffusion. The Cur located in the oil phase was released in large quantities (67.3%) in simulated intestinal fluid, predominantly through erosion. Owing to the action of β-mannanase, 60.3% of FUC located in the solid phase was released into simulated colonic fluid and dominated by the erosive mechanism. In addition, in vivo bioavailability evaluation and fluorescence imaging experiments confirmed that S/O/W-E enhanced Cur bioavailability by 6.4-fold through delivering it to the small intestine and inhibited FUC release in the upper GIT by delivering substantial amounts of FUC to the colon. This study is beneficial for effectively expanding the application of S/O/W-E in co-delivery systems.