A new α-amylase inhibitory peptide from Gynura medica extract

In this study, we discovered a novel peptide, Gymepeptide A, with α-amylase inhibitory activity in the water extract of Gynura medica. The structure of Gymepeptide A was determined as CGDREETR using HR-MS, ¹H NMR, ¹³C NMR, and 2D-NMR techniques. Notably, Gymepeptide A possesses a rare double arginine residue structure and exhibits strong α-amylase inhibitory activity. Enzyme dynamic assays, molecular docking experiments, and isothermal titration calorimetry indicated that the double arginine residue structure of Gymepeptide A interacts with amino acid residues in the nearby active site region of α-amylase through hydrogen bonds and van der Waals forces. This interaction effectively inhibits the hydrolysis activity of α-amylase. Furthermore, in vitro starch digestion tests revealed that Gymepeptide A significantly reduced the digestion rate of starch and the concentration of glucose produced after starch digestion. These findings highlight the great potential of Gymepeptide A in decreasing postprandial blood glucose levels.