Mechanisms involved on the antihypertensive effect from leaves of a standardized fraction from Hancornia Speciosa

Aim: to investigate the antihypertensive effect and its mechanism of action of a standardized fraction of Hancornia speciosa leaves (SFH) in hypertensive mice. Methods: Male Swiss mice were submitted surgery doca-salt. Systolic blood pressure (SBP) was measured by tail pletismography. Each mouse (SBP 183±6mmHg) received single dose of SFH by oral (po) route and SBP was monitored every hour until 5 hours. First branch of small mesenteric arteries mounted in myograph were used for vasorelaxation procedures. Nitrite levels were measured by spectrophotometry in the serum 1 hour after po administration of SFH (1mg/kg) or L-NAME (20mg/kg, ip). Results: SFH at doses from 0.03, 0.1 and 1mg/Kg induced significant and long-lasting reductions (5.1±2, 25±5, 60±6mmHg, up to 4 hours) on SBP compared to saline. In resistance vessel SFH produced a concentration-dependent vasorelaxation (IC₅₀=–4.58±0.16µg/mL) in mesenteric arteries pre-contracted with phenylephrine (3µM). SFH induced a significant increase on plasmatic content of nitrite in mice (98±8µM). Pre-treatment of mice with L-NAME blunted the effect of SFH. The relevance of this effect was confirmed by the inhibitory effect of L-NAME on the antihypertensive effect of SFH. Conclusions: we showed that a SFH is an antihypertensive drug, reduced the SBP through vasodilatation in resistance artery and by increase on plasmatic level of NO. Therefore, these results strongly suggest that SFH possess a great potential for its use on the treatment of hypertension.