Studies on the hypotensive, cardio-suppressant, vasodilator and antiplatelet activities of betel nut crude extract and its constituents

This study reported the hypotensive, cardio-suppressant, endothelium-dependent vasodilator and antiplatelet activities of the crude extract of Areca catechu (Ac.Cr), commonly known as betel nut. Ac.Cr tested positive for the presence of terpenoids, flavonoids, amines, tannins, phenols, alkaloids and saponins and exhibited a dose-dependent (0.1 to 1 mg kg^-1) atropine-sensitive fall in the arterial blood pressure of normotensive rats under anaesthesia. In isolated guinea-pig atria, Ac.Cr (0.1 to 10 μg mL^-1) showed an atropine-sensitive inhibitory effect on the force and rate of spontaneous atrial contractions. In the endothelium-intact rat aorta, Ac.Cr showed inhibition of the phenylephrine-induced contractions. This relaxant effect was blocked by atropine and L-NAME and was found absent in endothelium-denuded preparations. Ac.Cr (1.0-1.75mg mL^-1) also inhibited arachidonic acid (1.7 mM)-induced human platelet aggregation. Among all the known constituents of betel nut tested, only arecoline showed atropine-sensitive cardio-suppressant and vasodilator effects while catechin exhibited atropine-insensitive vasodilator and also antiplatelet activities. This study shows that betel nut exhibits blood pressure lowering and antiplatelet activities mediated at least partly through the presence of known constituents such as arecoline and catechin, respectively.