Quercetin-Hovenia dulcis polysaccharide complexes inhibit α-glucosidase and mitigate hyperglycemia

Polysaccharides and polyphenols are major bioactive constituents of plant-based foods, and their efficacy is often modulated by intermolecular interactions. In this study, non-covalent binary complexes of Hovenia dulcis polysaccharides (HDPs) and quercetin were synthesized via molecular self-assembly. Structural characterization confirmed the successful non-covalent association of quercetin onto alcohol-precipitated HDP fractions-HDPs30, HDPs50, and HDPs70. In vitro assays showed that all binary complexes exhibited significantly stronger α-glucosidase inhibition than the individual components. Acting as mixed-type inhibitors, the complexes bound reversibly to α-glucosidase via hydrogen bonding and van der Waals interactions, forming stable enzyme-inhibitor complexes. HDPs alone interacted through hydrophobic forces to form similarly stable complexes. Additionally, all inhibitors induced static fluorescence quenching of α-glucosidase, suggesting conformational changes upon binding. The binary complexes also demonstrated significant α-glucosidase inhibition in Caco-2 cells. These results highlight the potential of polysaccharide-polyphenol interactions to enhance bioactivity and provide a promising strategy for modulating glucose metabolism through synergistic multi-component systems.