Interaction between active compounds from Rosa roxburghii Tratt and β-glucosidase: Characterization of complexes and binding mechanism

Abstract

Understanding the molecular mechanisms underlying protein-flavonoid interactions is crucial for the application of protein-flavonoid complexes in food. The purpose of this study was to explore the factors that influence the efficient release of rutin (Rut) and isoquercitrin (Iso) from Lactobacillus acidophilus β-glucosidase (BGL) and the interaction mechanism among rutin, isoquercitrin and β-glucosidase. Spectroscopic analysis, atomic force microscopy and molecular docking studies showed that Rut or Iso quenched the intrinsic fluorescence of β-glucosidase in a static manner through the formation of a flavonoid-β-glucosidase complex. Atomic force microscopy and circular dichroism measurements confirmed that the conformation of β-glucosidase changed slightly. Molecular docking further proved that the interaction force of Rut or Iso with β-glucosidase was hydrogen bonding, hydrophobic interactions and electrostatic interactions, and the binding free energies of the interactions were −180.54 kcal mol−1 and -119.35 kcal mol−1, respectively. Substituted groups on the glycosylation of quercetin glycoside compounds are crucial for their binding to β-glucosidase. This study provides a theoretical basis for the design of natural flavonoid-protein complex functional foods.