A Drug used in Traditional Medicine: Harpagophytum procumbens DC. II. Cardiovascular Activity

In conscious normotensive rats the dried crude methanolic extract of Harpagophytumprocumbens secondary roots caused a significant dosedependent reduction of arterial blood pressure. The decrease was significant only at higher doses given by gavage (dried extract = 400 ). At the same time a decrease of heart rate was observed. In the same experimental conditions, harpagoside presented an activity lower than doses of Harpagophytumprocumbens extract containing corresponding quantities of harpagoside. In spontaneously beating Langendorff preparations of rabbit heart, the Harpagophytumprocumbens methanolic extract caused a mild decrease in the heart rate with a concomitant mild positive inotropic effect at lower doses but a marked negative inotropic effect at higher doses. The coronary flow decreased at higher doses only. The negative chronotropic and positive inotropic effects of harpagoside were comparatively higher with respect to that of the extract, whereas harpagide had only a slight negative chronotropic effect and a considerable negative inotropic one. Both in experiments on intact rats and on isolated rabbit heart, the Harpagophytumprocumbens extract also demonstrated a protective action with regard to arrhythmias induced by aconitine, and particularly to those provoked by calcium chloride and epinephrine—chloroform.