Inhibition of α-amylase activity by quercetin via multi-spectroscopic and molecular docking approaches

The quercetin-induced inhibition of alpha-amylase activity was comprehensively studied using various spectroscopic methods, including UV-Visible, fluorescence, and Fourier-transform infrared spectroscopy. Quercetin acted as a mixed-type inhibitor, and its binding altered the kinetic properties of alpha-amylase. Quercetin exhibited static binding with alpha-amylase, as evidenced by a higher Stern-Volmer constant (KSV) K SV ) at 298 K (9.56 +/- 0.63 x 103 3 L/ mol) compared to the K SV value at 318 K (5.56 +/- 0.48 x 103 3 L/mol). Additionally, quercetin induced conformational changes in the hydrophobic micro-environment surrounding the tryptophan and tyrosine residues of alpha-amylase, as indicated by fluorescence spectroscopy. Hydrophobic interactions primarily drove the spontaneous binding between alpha-amylase and quercetin from thermodynamic data. Molecular docking studies supported the role of hydrogen bonds (Asp197 and Gln63) and hydrophobic interactions (with active site residues Ala198, Leu165, and Trp59) in the complex formation. These findings provide a detailed understanding of how quercetin inhibits alpha-amylase activity, reinforcing its potential as a glycemic controller in food formulations.