Deciphering the inhibition effect of thymoquinone on xanthine oxidase activity using differential pulse voltammetry in combination with theoretical studies

摘要

Xanthine oxidase (XO) catalyzes the oxidation of xanthine to uric acid. Over-production of uric acid is a risk factor for hyperuricemia and other diseases. Although allopurinol decreases uric acid levels, it causes severe adverse effects. Therefore, more effort is needed in finding novel XO inhibitors with fewer side effects. In this study, differential pulse voltammetry was used to investigate the inhibitory effect of thymoquinone (TQ) on the XO activity while the major problem was the overlap of the obtained signals. Thus, Parallel Factor Analysis (PARAFAC) was applied to extract the useful information. Also, docking was used to investigate how TQ and the active site of XO fit together. PARAFAC results based on the voltammetry studies revealed that TQ blocks the catalytic centers of XO, which leads to a decrease in the electrochemical signal of Mo center in XO. The results also indicated the dose-dependent inhibition of XO with TQ. Molecular docking studies were shown TQ surrounds the active sites of XO and reduces the oxidation of xanthine to uric acid. Therefore, the electrochemical response of Mo decreases in the presence of TQ. This finding is in good agreement with the results obtained from molecular docking studies.