Inhibition mechanism of baicalein and baicalin on xanthine oxidase and their synergistic effect with allopurinol

Suppression of xanthine oxidase (XO) may contribute to control hyperuricemia and gout. In this study, baicalein and baicalin, two dietary flavones, were found to inhibit the formation of uric acid and generation of superoxide anion (O 2 − ) catalysed by XO through interaction with primary amino acid residues located in flavin adenine dinucleotides center of XO. Baicalein or baicalin binding to XO mainly facilitated by hydrophobic interactions and hydrogen bonds resulted in more compact of XO structure. The concentration profiles and pure spectra of the components extracted from highly overlapping spectral signal by multivariate curve resolution–alternating least squares chemometrics algorithm confirmed the formation of complexes and monitored the reaction kinetics process between XO and these flavones. Furthermore, the isobolographic analysis found that baicalein or baicalin exhibited a moderate synergy on the inhibition of XO when it combined with allopurinol as well as the joint use of baicalein and baicalin.