Antihypertensive actions of methylripariochromene a from Orthosiphon aristatus, an Indonesian traditional medicinal plant

Methylripariochromene A (MRC) was isolated from the leaves of Orthosiphon a ristatus (Lamiaceae) and subjected to the examination of several pharmacolo gical actions related to antihypertensive activity. The following four find ings were revealed from the present study: 1) MRC caused a continuous decre ase in systolic blood pressure and a decrease in heart rate after subcutane ous administration in conscious male SHRSP, 2) MRC exhibited the concentrat ion-dependent suppression of contractions induced by high K+, l-phenylephri ne or prostaglandin F-2 alpha in endothelium-denuded rat thoracic aorta, 3) MRC showed a marked suppression of contractile force without a significant reduction in the beating rate in isolated bilateral guinea pig atria, and 4) MRC increased urinary volume and the excretion of Na+, K+ and Cl- for 3 h after oral administration with a load of saline in fasted rats. These fin dings indicate that MRC possesses some actions related to a decrease in blo od pressure, i.e. vasodilating action, a decrease in cardiac output and diu retic action. Furthermore, it is presumed that the traditional use of this plant in the therapy of hypertension may be partially supported by these ac tions with MRC.