Exploration of xanthine oxidase producing microorganisms from hypoxanthine supplemented soil and their inhibitors from plants employing nitroblue tetrazolium based colorimetric assay method

Xanthine oxidase is a member of molybdoenzyme family and has catalytic role in purine degradation, metabolizing hypoxanthine and xanthine to uric acid with the generation of superoxides. In the present study, microtitre plate based colorimetric assay was used to screen the xanthine oxidase producing microorganisms from the soil treated with hypoxanthine with different concentrations (2mM, 4mM, 6mM) for six weeks daily and at an interval of seven days. The basic principle of assay is that the superoxides produced by microbial cultures, grown in xanthine rich medium interacts with Nitroblue tetrazolium (NBT) solution and produces dark blue color, showing the presence of xanthine oxidase. Furthermore, the plant extracts were assessed for their xanthine oxidase inhibitory activity. The inhibitory effect of polyphenolic rich fractions of Juniperus recurva and Chukrasia tabularis was determined to find out the natural inhibitors of xanthine oxidase. The inhibitory effect of allopurinol on xanthine oxidase was also observed.