Vasorelaxant and antihypertensive effect of Cocos nucifera Linn. endocarp on isolated rat thoracic aorta and DOCA salt-induced hypertensive rats.

ABSTRACT

ETHNOPHARMACOLOGICAL RELEVANCE The fruits of Cocos nucifera Linn. (Arecaceae) have long been used in traditional medicine for the treatment of cardio-metabolic disorders. AIM OF THE STUDY To evaluate the ethanolic extract of Cocos nucifera Linn. endocarp (CNE) for its vasorelaxant activity on isolated rat aortic rings and antihypertensive effects in deoxycorticosterone acetate (DOCA) salt-induced hypertensive rats. MATERIALS AND METHODS: Cocos nucifera Linn. endocarp was extracted with ethanol and characterized by HPLC. CNE was examined for its in vitro vascular relaxant effects in isolated norepinephrine, phenylephrine or potassium chloride pre-contracted aortic rings (both intact endothelium and denuded). In vivo anti-hypertensive studies were conducted in DOCA salt-induced uninephrectomized male Wistar rats. RESULTS: Removal of endothelium or pretreatment of aortic rings (intact endothelium) with l-NNA (10µM) or ODQ (10 µM) followed by addition of contractile agonists prior to CNE significantly blocked the CNE-induced relaxation. Indomethacin (10µM) and atropine (1 µM) partially blocked the relaxation, whereas glibenclamide (10 µM) did not alter it. CNE significantly reduced the mean systolic blood pressure in DOCA salt-induced hypertensive rats (from 185.3 ± 4.7 mmHg to 145.6±6.1 mmHg). The activities observed were supported by the polyphenols, viz. chlorogenic acid, vanillic acid and ferulic acid identified in the extract. CONCLUSIONS: These findings reveal that the vasorelaxant and antihypertensive effects of CNE, through nitric oxide production in a concentration and endothelium-dependent manner, is due to direct activation of nitric oxide/guanylate cyclase pathway, stimulation of muscarinic receptors and/or via cyclooxygenase pathway.