Revealing the inhibition mechanism of ultrasound-assisted purified dried apricot polyphenols on α-amylase: Insights from multispectral and computational analyses

Ultrasound-assisted purification was employed to extract and refine polyphenols from dried apricots. The inhibitory mechanism of these ultrasonically purified polyphenols against porcine pancreatic α-amylase (PPA) was investigated through inhibition kinetics, fluorescence spectroscopy, circular dichroism (CD) spectroscopy, molecular docking, and molecular dynamics (MD) simulations. UHPLC–MS/MS analysis identified 19 phenolic compounds in the purified polyphenols (PP), with rutin, morin, and isoquercetin as the predominant constituents. Enzyme inhibition assays demonstrated that PP exhibited strong inhibitory activity (IC 50  = 3.46 ± 0.20 mg/mL) and acted as a mixed-type inhibitor, whereas the three monomeric polyphenols showed competitive inhibition. Fluorescence and CD analyses revealed that both PP and its major monomeric components induced conformational changes in the secondary structure of PPA by altering the hydrophobic microenvironment surrounding tryptophan and tyrosine residues, thereby reducing enzymatic activity. MD simulations confirmed the structural stability of the polyphenol-PPA complexes, and binding free-energy calculations indicated that rutin and isoquercetin exhibited stronger binding affinity and higher complex stability than morin, primarily mediated by hydrogen bonding and hydrophobic interactions. Collectively, this work provides a comprehensive understanding of the inhibitory mechanism of ultrasonically purified dried apricot polyphenols and their key constituents against PPA. These findings establish a theoretical basis for the efficient purification of polyphenolic compounds and their potential application as natural hypoglycemic agents.