The effects of an aqueous leaf extract of Clausena anisata (Willd.) Hook.f.ex Benth. on blood pressure, urine output, angiotensin II levels and cardiac parameters in spontaneously hypertensive rats

Clausena anisata (Willd.) Hook.f. ex Benth (Rutaceae) is a medicinal plant indigenous to Southern Africa and scientific studies report on its biomedical activities and possible antihypertensive property by demonstrating in vitro angiotensin converting enzyme  inhibition. This study investigated the antihypertensive effects of an aqueous leaf extract of Clausena anisata in a spontaneously hypertensive rat model, and determined whether these blood pressure lowering effects could be attributed to diuresis, the inhibition of the renin-angiotensin-aldosterone blood pressure control system and/or possible negative inotropic or chronotropic cardiac effects. Aqueous extracts were prepared from ground leaves of Clausena anisata. Four groups of ten rats each received 50, 100, 200 or 400 mg/kg.bw of aqueous extracts intra-arterially respectively to obtain a dose response relationship. Another two groups of fifteen rats each received either plain water (control group) or the plant extract added to their drinking water (experimental group) for 40 days. Urine output was measured at 10 day intervals. All cardiovascular data was recorded with a Powerlab 200 recording system in anaesthetised rats that were catheterised via the carotid artery. Plasma angiotensin II levels were determined using a commercially available enzyme immunosorbent assay kit. The results showed that Clausena anisata  was effective in reducing aortic blood pressure at the highest dose tested (400 mg/kg.bw). Furthermore, Clausena anisata significantly reduced the blood pressure over 40 days.  This appears to have occurred via a mechanism that causes a reduction in plasma angiotensin II levels and not via  diuresis or negative chronotropic effects.  Key words: angiotensin-converting-enzyme inhibitor (ACE inhibitor), negative inotropic effect, diuresis, antihypertensive agents, traditional medicinal plants, lethal dose 50  cardiac contractility, South Africa.