Cardiovascular effects of ethanolic and aqueous extracts of Pimenta dioica in Sprague-Dawley rats.

The hypotensive activity of ethanolic and aqueous extracts of Pimenta dioica and several fractions of the aqueous extract was observed in anaesthetized normotensive rats. General effects of the extracts and fractions were assessed through Hippocratic screening showing a central nervous system (CNS) depressant effect. The intravenous (i.v.) administration of the aqueous extract of Pimenta dioica (30, 70, 100 mg/kg) produced a dose-related significant fall in mean arterial blood pressure (MAP). The ED50 was 53.94 mg/kg. The hypotensive effect of identical doses (100 mg/kg) of the aqueous extract (95% decrease) was significantly greater (P < 0.05) than the effect of the ethanolic extract (67% decrease). The final aqueous fraction produced the greatest hypotensive activity compared to the other fractions of the total aqueous extract. There were no significant changes in the heart rate and no abnormalities were observed in the EKG. The mechanisms of action of the extracts have not been determined. Structural elucidation of the compounds responsible for this activity is under investigation.