pH-Responsive Chitosan–Alginate Hydrogel Beads Co-Encapsulating Jujube Polysaccharides and cAMP: Enhanced Antioxidant Activity and Gastrointestinal Controlled Release

Abstract

Jujube polysaccharides (ZJPA) and cyclic adenosine monophosphate (cAMP) are bioactive compounds with antioxidant and health-promoting potential, and their combination exhibits enhanced antioxidant activity. However, their limited stability and susceptibility to gastrointestinal environmental stresses restrict their applications in functional foods. In this study, a pH-responsive composite hydrogel bead delivery system was developed using chitosan (CS) and sodium alginate (SA) as wall materials to co-encapsulate ZJPA and cAMP, aiming to protect these bioactive compounds during gastrointestinal digestion while maintaining their enhanced functionality. The hydrogel beads were fabricated via the ionotropic gelation method, and the formulation parameters were optimized using single-factor experiments combined with response surface methodology (RSM). The optimized hydrogel beads were obtained under the conditions of calcium chloride concentration of 3%, CS concentration of 0.5%, SA concentration of 3%, and core-to-wall ratio of 1:6, with a cAMP microencapsulation yield (MEY) of 97.79%. Structural characterization confirmed that ZJPA and cAMP were successfully incorporated into the CS-SA network through electrostatic interactions and intermolecular hydrogen bonding without the formation of new covalent bonds. Furthermore, the hydrogel beads exhibited distinct pH-responsive swelling and gastrointestinal release behaviors, providing effective protection under acidic gastric conditions and enabling sustained release under intestinal conditions. Importantly, the DPPH radical scavenging assay demonstrated that the co-encapsulation strategy preserved the enhanced antioxidant activity between ZJPA and cAMP. Overall, this study establishes a multifunctional hydrogel bead delivery strategy integrating enhanced bioactivity preservation, gastrointestinal protection, and controlled release, providing new opportunities for the application of jujube-derived bioactive compounds in functional foods.