Antihypertensive effect of methanol leaf extract of Anacardium occidentale against L‐Nitro Arginine Methyl Ester (L‐NAME)‐induced hypertension in male Wistar rats

Abstract

The Anacardium occidentale plant; commonly known as Cashew has been widely reported for its efficacy in the treatment of various ailments such as hypertension. The efficacy of the plant has been attributed to its phytochemical constituents. Hypertension was induced in rats via oral administration of L‐Nitro Arginine Methyl Ester (L‐NAME); a non‐selective nitric oxide synthase inhibitor. To examine the antihypertensive properties of the Anacardium occidentale extract, twenty‐five (25) male Wistar rats were divided into 5 groups of 5 animals each and were grouped as follows: Group A (Distilled water), Group B (L‐NAME 40 mg/kg), Group C (100 mg/kg extract, 40 mg/kg L‐NAME), Group D (200 mg/kg extract, 40 mg/kg L‐NAME), Group E (10 mg/kg of Lisinopril, 40 mg/kg L‐NAME) orally for a duration of 4 weeks. Blood pressure parameters, markers of oxidative stress and antioxidant enzymes were determined. Immunohistochemistry of the angiotensin converting enzyme, mineralocorticoid receptor, angiotensin II type 1 receptor, and kidney injury molecule‐1 (Kim‐1) expressions were also determined. Treatment of hypertensive rats with Anacardium occidentale methanol leaf extract normalised systolic, diastolic and mean arterial blood pressure compared to hypertensive untreated rats. There was significant improvement in serum nitric oxide bioavailability of hypertensive rats treated with Anacardium occidentale methanol leaf extract in comparison to hypertensive untreated rats. Furthermore, there was a significant reduction in markers of oxidative stress and concurrent increase in the levels of renal antioxidant enzymes of hypertensive treated rats. Immunohistochemistry revealed significant reduction in the renal expressions of angiotensin converting enzyme, mineralocorticoid receptor, angiotensin II type 1 receptor, and kidney injury molecule‐1 of hypertensive treated rats. The results of this study suggest that Anacardium occidentale methanol leaf extract holds promise for the management of hypertension through the inhibition of angiotensin converting enzyme as its novel mechanism of action