Investigation of Black and Brown Rice as Inhibitors of Tyrosinase and Xanthine Oxidase Enzymes: An in vitro and in silico Investigation

Abstract

Background Xanthine oxidase and tyrosinase are enzymes involved in various functions in the body. Tyrosinase and xanthine oxidase have high activity levels in various diseases like gout hyperpigmentation and neurodegradative disease. In our study, we checked for the ability of locally available black and brown rice varieties to inhibit the two enzymes. Materials and Methods We carried out in vitro assay of the activity of the two enzymes in the presence of rice extracts. To identify the phytochemicals potentially responsible for inhibitory activity we carried out in silico docking investigation using Auto dock followed by molecular dynamics simulation analysis. Results and Discussion The in vitro assays showed reduction in the enzyme activity of xanthine oxidase and tyrosinase in the presence of the rice extracts. The molecular docking analysis showed that the major polyphenols of the rice extracts showed good binding with the two enzymes. Molecular dynamics simulation showed that catechin hydrate from black rice and β-sitosterol from brown rice showed steady binding with xanthine oxidase and tyrosinase respectively. Conclusion From our studies we can conclude that both rice extracts had inhibitory activity towards the enzymes and catechin hydrate and β-sitosterol could potentially be the compounds responsible for inhibition of xanthine oxidase and tyrosinase respectively.

Keywords: Black rice; Brown rice; Xanthine oxidase; Tyrosinase; Enzyme activity; Docking