G. Schmeda-Hirschmann , J. I. Loyola 1, S. Reyes 1, E. Hubert, M. Rodriguez , J. Rodriguez. Departamento de Ciencias Biológicas, Universidad de Talca, Casilla 747, Talca, Chile.The hydroalcoholic extract of Fabiana imbricata inhibited the enzyme -glucuronidase (-gluc) in vitro. Bioassay-guided isolation led to scopoletin as the main active constituent of F. imbricata. Scopoletin was a noncompetitive inhibitor of -D-glucuronidase with a Ki value of 4 × 10-5 M. A single oral dose of 250 mg/kg body weight F. imbricata extract produced a significant increase (p<0.05) in the urine output of rats. The diuretic effect of the extract was weak in comparison with hydrochlorothiazide at 25 mg/kg. In the acute oral toxicity study in rats, Pichi was shown to be a low toxicity crude drug at doses up to 5 g crude extract/kg body weight. At concentrations up to 0.50 mg/mL, the crude extract did not increase the number of chromosome aberrations in the in vitro human lymphocyte assay.