High blood pressure is a chronic cardiovascular disease caused by an increase in blood pressure above normal. Poorly treated high blood pressure can damage the arteries of the brain, heart and kidneys, leading to serious complications. Long considered a disease of the rich, hypertension is now a real public health problem in Africa. The treatment of this disease is not only long term, but it is also expensive for many patients. To overcome this, the African populations resort to herbal treatments. Among these plants we have Gnetum africanum which is a food plant from Gabon which has medicinal properties. Our work aims to validate the pharmacological effect of the aqueous extract of Gnetum africanum by a study on the isolated rat aorta. The rings aorta are kept in an oxygenated Mac Ewen solution and maintained at a temperature of 37°C. At the beginning of the experiment, the aortic band is subjected to a tension of 1 g force. We then balance the device for 1 hour to have stable contractile movements. The aqueous extract of the leaves showed a relaxing action on the smooth muscles of the isolated rat aorta. This relaxation of the isolated rat aorta is similar to that obtained by the action of amlodipine. These observations suggest that decoction of Gnetum africanum have a relaxant effect on rat isolated aorta. This justifies its use by traditional therapists in the treatment of arterial hypertension.