Vascular mechanisms underlying the hypotensive effect of Rumex acetosa.

CONTEXT

Rumex acetosa L. (Polygonaceae) is well known in traditional medicine for its therapeutic efficacy as an antihypertensive.

OBJECTIVE

The study investigates antihypertensive potential of crude methanol extract (Ra.Cr) and fractions of Rumex acetosa in normotensive and hypertensive rat models and probes the underlying vascular mechanisms.

MATERIALS AND METHODS

Ra.Cr and its fractions were tested in vivo on normotensive and hypertensive Sprague-Dawley rats under anaesthesia for blood pressure lowering effect. In vitro experiments on rat and Oryctolagus cuniculus rabbit aortae were employed to probe the underlying vasorelaxant mechanism.

RESULTS

In normotensive rats under anaesthesia, Ra.Cr caused fall in MAP (40 mmHg) at 50 mg/kg with % fall of 27.88 ± 4.55. Among the fractions tested, aqueous fraction was more potent at the dose of 50 mg/kg with % fall of 45.63 ± 2.84. In hypertensive rats under similar conditions, extract and fractions showed antihypertensive effect at same doses while aqueous fraction being more potent, exhibited 68.53 ± 4.45% fall in MAP (70 mmHg). In isolated rat aortic rings precontracted with phenylephrine (PE), Ra.Cr and fractions induced endothelium-dependent vasorelaxation, which was partially blocked in presence of l-NAME, indomethacin and atropine. In isolated rabbit aortic rings pre-contracted with PE and K-(80 mM), Ra.Cr induced vasorelaxation and shifted Ca concentration-response curves to the right and suppressed PE peak formation, similar to verapamil, in Ca-free medium.

DISCUSSION AND CONCLUSIONS

The data indicate that l-NAME and atropine-sensitive endothelial-derived NO and COX enzyme inhibitors and Ca entry blocking-mediated vasodilator effect of the extract explain its antihypertensive potential.