An invitro study on inhibition of Tyrosinase and Xanthine oxidase by alkaloid rich fraction from Indigofera aspalathoides

To assay the in vitro xanthine oxidase and Tyrosinase inhibitory activity of the alkaloid fractions of the leaves of Indigofera spalathoides and to determine its enzyme inhibition mechanism. Xanthine oxidase and Tyrosinase inhibitory activity was assayed spectrophotometrically under aerobic conditions and the degree of enzyme inhibition was determined by measuring the increase in absorbance at 295nm associated with uric acid and Tyrosine formation respectively. Enzyme kinetics was carried out using Lineweaver-Burk plots using xanthine and Tyrosine as the substrate. The alkaloid fractions exhibited highest potency (82.3±1.5) at 100 μl/ml in Xanthine oxidase followed by Tyrosinase inhibitory diphenolase 50±1.2 and monophenalase 60.05 ± 1.4 fractions. Enzyme inhibition mechanism indicated that the mode of inhibition was of a mixed type. These results suggest that the use of Indigofera spalathoides for the treatment of gout could be attributed to its xanthine oxidase inhibitory activity and Tyrosinase inhibitors have become increasingly important as cosmetic and medicinal products, primarily to control melanin pigmentation.