Structural and digestive characteristics of high amylose maize starch-flavonoid complexes: Role played by the flavonoids in enhancing resistant starch and inhibiting enzymes

Diabetes and obesity are global health challenges, regulating starch digestion offers a promising strategy. High amylose maize starch (HAMS)-flavonoid complexes were synthesized using five classes of flavonoids with distinct conformations. The structures and digestibility of complexes were characterized to elucidate the interaction mechanisms between flavonoids and HAMS. All complexes exhibited complexing indices exceeding 43%, with the HAMS-catechin complex (HAMS-CAT) achieving the highest index of 67.6%. The degree of short-range molecular order, helical structures, and crystallinity of complexes were significantly influenced by the flavonoids. Notably, the HAMS-CAT exhibited the highest resistant starch content at 51.8%, which was 24.4% higher than that of the control sample. Enzyme inhibition assays revealed that CAT inhibited α-amylase by 77.9%, while naringenin inhibited α-glucosidase by 90.3% at 10 mg/mL. The interaction between flavonoids and HAMS impeded the complexes contact with enzymes, and the released flavonoids inhibited the activities of enzymes to further reduced digestibility. This interaction also protected the antioxidant activity of flavonoids during heating. Among the five flavonoids, CAT exhibits a flexible conformation with five hydroxyl groups and lacks carbonyl group on the C4 chain. Consequently, CAT interacted with HAMS effectively by forming multidentate hydrogen bonds and enhanced the degree of short-range molecular order and crystallinity of HAMS-CAT. This work systematically compares the potential of flavonoids with various conformations in modulating starch structure and digestibility. These findings provide a feasible idea for the application of flavonoids in food ingredients to reduce starch digestibility and offer theoretical support for the industrialization of starch-based healthy foods.