The infusion of the stem-bark of Exostema caribaeum (ECSB) is widely used to treat malaria fevers and diabetes. Herein, we report the preclinical toxicity and efficacy as antidiabetic agent of this widely used preparation. According to the Lorke criteria, the infusion was not toxic to mice since the LD50 was higher than 5000 mg/kg. The aqueous extract of E. caribaeum (ECSB; 500 mg/kg) caused a significant hypoglycemic effect in NA/STZ-diabetic mice (-41.4%) in a classical nine hours experiment, showing an action similar to glibenclamide (positive control). In the oral sucrose tolerance test, ECSB (100, 300 and 500 mg/kg) caused significant decrease of the postprandial peak in both normal and NA/STZ-diabetic mice; the maximum antihyperglycemic effect was observed at the dose of 100 mg/kg (62% of postprandial peak reduction), similar to the activity provoked by acarbose (positive control). The antihyperglycemic and hypoglycemic actions demonstrated for ECSB are due to the presence of 4-phenylcoumarins.
