Inhibition of pancreatic α-amylase by Lonicera caerulea berry polyphenols in vitro and their potential as hyperglycemic agents

Natural food-derived hypoglycemic molecules hold potential for decreasing the postprandial increase in blood glucose and preventing type 2 diabetes along with its associated comorbidities. This study investigated the inhibitory effects of Lonicera caerulea berry polyphenols (LCBP) on the activity of alpha-amylase and the involved mechanisms. We used an enzyme inhibition assay, enzyme kinetics analysis, fluorescence quenching, and molecular docking to assess the effects of LCBP and its primary constituents. LCBP significantly inhibited the activity of alpha-amylase (IC50 301.5 mu g/mL) and exhibited a higher inhibitory effect than acarbose, a positive control for carbohydrate digestion. The enzyme kinetics and Lineweaver - Burk plot analyses revealed a reversible competitive inhibition of alpha-amylase activity by LCBP and its main constituent components cyanidin-3-glucoside (C-3-G), catechins, and chlorogenic acid (CA). Fluorescence quenching experiments revealed that LCBP exerted a dose-dependent quenching effect on alpha-amylase and produced an emission wavelength redshift due to static quenching. The computer simulation-assisted molecular docking study showed that the binding of C-3-G, catechins, and CA disrupts enzyme conformation, while the formation of the polyphenol-enzyme complex inhibits enzyme activity. Together, these results suggest that LCBP effectively reduces postprandial hyperglycemia and type 2 diabetes and thus, exhibits potential for application as a functional food additive.