Inhibition of Xanthine oxidase by 1-O-methyl chrysophanol, a hydroxyanthraquinone isolated fromAmycolatopsis thermoflavaICTA 103

Abstract

AbstractHyperuricemia caused by elevated levels of serum uric acid is responsible for implication of gout and other associated disorders that influence the human health. So far, Xanthine oxidase (XO) inhibitors are the choice of first line drugs for the treatment of hyperuricemia. The objective of the present study was to isolate a potent XO inhibitor from the actinobacteria and to evaluate its inhibitory mechanism. Initially, XO was isolated from bovine milk using standard protocol and enzyme kinetics were evaluated. Thereafter, culture filtrates of actinobacteria (Amycolatopsis thermoflavaICTA 103),Streptomyces luteireticuliICTA 16,Streptomyces kurssanoviiICTA165 andAmycolatopsis luridaICTA 194) were screened for XO inhibition usingin vitroqualitative NBT plate assay followed by extraction and purification of potent inhibitor 1-O-methyl chrysophanol (OMC), from the culture filtrate ofAmycolatopsis thermoflavaICTA 103, which belongs to hydroxy anthraquinones (HAQ) family. Further,in silicomolecular model building was performed to study the binding affinity of OMC towards XO followed by quantitativein vitrospectroscopic assays. The molecular building study explored the mechanistic view of binding interaction between inhibitor & enzyme and the results were corroborates with thein vitrokinetic study. Thein vitroresults revealed the significant enzyme inhibition potential of OMC with an IC50andKivalue of 24.8 ± 0.072 µM & 2.218 ± 0.3068 µM respectively. These results are comparable to standard allopurinol, however, more significant than its structural analog, chrysophanol. The kinetic analysis revealed that OMC is a reversible slow binding inhibitor and the Lineweaver - Burkplot analysis showed mixed type inhibition of OMC against XO. These results are in agreement with chrysophanol. Findings of this study proposed a new derivative of HAQ in the pipeline of hyperuricemia therapeutic drug candidates.