In neonatal jaundice, β-glucuronidase converts conjugated bilirubin into the unconjugated form and increases its level in the blood. Many natural compounds have been identified as β-glucuronidase inhibitors. The aim of this study was to evaluate the effect of hydro-methanolic extracts of 100 plants on β-glucuronidase. The β-glucuronidase activity was measured by a spectrophotometric method using Phenolphthalein glucuronide and 4-nitrophenyl β-D-glucuronide. Kinetic study of the enzyme was performed in the presence and absence of the plant extract. It was revealed that from hydro-methanolic (70%) extracts, Rosa damascena and Ipomoea tricolor showed more than 85% inhibitory effect on β-glucuronidase. Rosa damascena showed competitive inhibition, and Ipomoea tricolor showed non-competitive inhibition. The Km and Vmax values for β-glucuronidase were 23.32 mM and 0.814 mM min-1, respectively. When using 4-nitrophenyl β-D-glucuronide, Stevia and Cerasus avium showed more than 65% inhibitory effect on β-glucuronidase. Both Stevia and Cerasus avium showed non-competitive inhibition. The Km and Vmax values for β-glucuronidase were 16.98 mM and 0.936 mM min-1, respectively. None of the plant extracts showed an activation effect on the enzyme. The data suggest that these plants might be good candidates for the treatment of neonatal jaundice and its related diseases.
Inhibitory Effect of Bile Constituents upon Bacterial β-Glucuronidase Activity
