RESUMO
Hyaluronidase (HAase) is an important enzyme involved in a promoting inflammation pathway. Flavonoids are a group of major polyphenols including flavonols (such as myricetin and rutin), dihydroflavones (such as naringin and hesperidin), and isoflavones (such as genistein and puerarin), which have been proved to possess anti-inflammatory effects. In this study, the binding of the six flavonoids to HAase was investigated by steady state and time-resolved fluorescence, circular dichroism (CD) spectroscopy and molecular docking methods. Fluorescence data reveal that the fluorescence quenching mechanism of HAase by flavonoids is all static quenching procedure regardless of their core structure. The binding affinity is strongest for rutin and ranks in the order rutin > hesperidin > myricetin > puerarin > genistein > naringin. The thermodynamic analysis implies that hydrophobic interaction, electrostatic force and hydrogen bonding are the main interaction forces. Synchronous fluorescence spectroscopy and CD spectroscopy indicate that flavonoids have the same core structure and have similar effects on the microenvironment around Trp and Tyr residues and the secondary structure of HAase. The results of molecular docking show that the binding of flavonoids with the catalytic amino acid residues of HAase may lead to the decrease of enzyme activity.