Multispectral and Computational Modeling Analysis of the Kinetic Inhibition and Binding Properties of Inonotus obliquus Extract on Xanthine Oxidase

ABSTRACT

Xanthine oxidase (XO) is a key enzyme in uric acid (UA) metabolism. The extracts of Inonotus obliquus ( I. obliquus ) have the potential to inhibit the activity of XO. In this study, the contents of protocatechuic aldehyde (PAH) and protocatechuic acid (PA) from I. obliquus were quantitatively analyzed using high‐performance liquid chromatography (HPLC). The two compounds are similar in structure, but the difference in their substituents may lead to variations in their ability to interact with enzymes. Spectroscopic analyses of fluorescence quenching, synchrotron fluorescence, three‐dimensional fluorescence, and circular dichroism show that PAH/PA has an obvious quenching effect on XO due to hydrogen bonding and van der Waals forces, and it is capable of altering the secondary structure of XO. Docking studies reveal that PAH/PA targets the Mo‐Pt domain within XO's active center, with hydrogen bonds and hydrophobic forces being essential for the binding process. The molecular dynamics simulation revealed that the PAH + XO complex exhibited greater stability, compactness and stronger hydrogen bonding interactions compared with the PA + XO complex, indicating its potential as a more stable therapeutic candidate. Results from this study delineate the XO‐inhibitory capacity of PAH and PA derived from I. obliquus , forming a rationale for subsequent inhibitor development.