High effective proteinaceous α-amylase inhibitors from grains and control release

Plant-derived α-amylase inhibitors exhibit great capacity in glycaemic control by restraining dietary starch digestion. However, natural α-amylase inhibitors with strong inhibitory activity and good stability are still scarce. In this study, the inhibitory activity and stability of proteinaceous α-amylase inhibitors derived from eleven grains were examined, and microencapsulation was carried out to protect the inhibitors in gastric fluid. We found that the highland barley protein extract (HBPE) showed the most potent α-amylase inhibitory activity (IC50 = 1.11 mg/mL). HBPE is a reversible noncompetitive α-amylase inhibitor and displayed good stability across various pH and temperatures. It showed high trypsin tolerance but low pepsin tolerance. Thus HBPE-encapsulated microspheres were prepared by the composite of sodium alginate/gellan gum with the internal ionic gelation method. The optimum encapsulation condition was determined, and the prepared microspheres displayed discrete, uniform and regular sphericities with diameters around 53 μm, and better mechanical strength with more than 81% activity retention rate. Moreover, the microspheres protected the HBPE in gastric fluid and extended HBPE release in the small intestinal fluid, revealing excellent control release of HBPE in simulated gastrointestinal digestion. Our study provides a new and effective strategy for the management of postprandial blood glucose.