Study on the interaction of hyaluronidase with certain flavonoids

In this study, the binding of baicalin, liquiritin and isoliquiritigenin to hyaluronidase (HAase) was investigated by computational modeling approaches as well as steady state fluorescence, time-resolved fluorescence and circular dichroism (CD) spectroscopy. The molecular docking results reveal that the three flavonoids bind in the internal cavity of HAase. The catalytic activity of amino acid residues near the binding site indicates that HAase activity will be inhibited by the three flavonoids. The results of molecular docking and thermodynamic analysis show that hydrophobic interaction, electrostatic force and hydrogen bond are the main interaction forces. Fluorescence data reveal that the fluorescence quenching mechanism of HAase by the three flavonoids is all static quenching procedure. The binding affinity is strongest for baicalin and ranks in the order baicalin >i soliquiritigenin > liquiritin. The binding energy values for the interaction of HAase with baicalin, liquiritin and isoliquiritigenin are -26.634 kJ mol −1 , -23.762 kJ mol −1 and -25.929 kJ mol −1 at 298.15 K, respectively. Synchronous fluorescence spectroscopy indicates that the addition of baicalin and liquiritin increases the polarity and decreases the hydrophobicity of HAase around Trp-and/or Tyr. The addition of isoliquiritigenin has no significant effect on the microenvironment of Trp-and Tyr-of HAase. The results of CD show that the binding of the three flavonoids with HAase leads to changes in the secondary structure of HAase.