Separation, identification, and design of α-glucosidase inhibitory peptides based on the molecular mechanism from Paeonia ostii 'Feng Dan' seed protein

Peptides are considered promising sources of nutraceuticals. In this study, a mixture of peptides was prepared from Paeonia ostii 'Feng Dan' seed meal protein by continuous enzymolysis. Successive separation and purification procedures, including ultrafiltration and reversed-phase high-performance liquid chromatography (RP-HPLC), were performed, and six novel peptides were identified by liquid chromatography-electrospray ionization source-mass spectrometry/mass spectrometry (LC-ESI-MS/MS). In an in vitro antidiabetic activity test, Tyr-Phe-Phe-Met exhibited stronger alpha-glucosidase inhibitory activity (48.17 +/- 3.34% at 1 mg/mL) than the other peptides. Docking studies of this peptide into the active site of alpha-glucosidase showed that the formation of hydrogen bonds could be critical for the enzymatic trapping of inhibitory peptides. Furthermore, two novel peptides, Phe-Phe-Phe-Met (IC50 = 245.46 +/- 44.01 mu M) and Tyr-Tyr-Phe-Met (IC50 = 306.71 +/- 48.17 mu M), with improved alpha-glucosidase inhibitory activity, were designed based on molecular docking. Therefore, the seed meal of Paeonia ostii could be considered a functional food ingredient for the management of hyperglycemia, and three novel peptides were identified as alpha-glucosidase inhibitors.