Vasorelaxant activity and acute toxicity of the ethanolic extract of Zanthoxylum rhoifolium Lam leaves

The study evaluated the vasorelaxant effect induced by the ethanolic extract of the leaves of Zanthoxylum rhoifolium Lam (EEtOH-Zr/leaves). Wistar rats were treated with the leaf extract containing a single dose of 2,000 mg / kg, v.o. After 14 days, the animals were anesthetized for blood collection and subsequent analysis of the biochemical parameters; they were then euthanized (sodium pentobarbital-100 mg/kg, i.p.) for the removal and morphological analysis of the heart, lung, liver and kidney. The vasorelaxation activity the and vascular reactivity of EEtOH-Zr/leaves were evaluated on artery mesenteric rings isolated from rats. The extract showed no signs of toxicity and no significant difference in the values of the biochemical parameters between the control group and the group of treated animals. In the evaluation of pharmacological activity in the smooth muscle, the EEtOH-Zr/leaves caused vasorelaxant effect on the tonic contraction induced by phenylephrine in mesenteric artery preparations in the presence (pD2=2.17±0.05 µg/mL; Emax=99.8±5.2%) and absence (pD2=2.14±0.05 µg/mL; Emax=95.3±6.4%) of the vascular endothelium. Oral administration of EEtOH-Zr/leaves reduced the contraction induced by the cumulative addition of PHE. It is concluded that the EEtOH-Zr/leaves promote vasorelaxation and reduce vascular reactivity of adrenergic alpha-1 agonist in the mesenteric artery. The results did not show toxic effects of the extract.

Antihypertensive and vasorelaxant effects of ethanol extract of stem barks from Zanthoxylum rhoifolium Lam in rats.

Administration of ethanol extract of stem bark from Z. rhoifolium (EEtOH-ZR) induced hypotension associated with a dual effect in heart rate in normotensive rats. This response was highlighted in spontaneously hypertensive rats (SHR). In rat superior mesenteric artery rings, the cumulative addition of EEtOH-ZR (0.1–750 µg/mL) on a phenylephrine-induced pre-contraction (10-5 M) promoted a vasorelaxant effect by a concentration-dependent manner and independent of vascular endothelium. A similar effect was obtained on KCl-induced pre-contractions (80 mM). EEtOH-ZR attenuated contractions induced by cumulative addition of CaCl2 (10-6–3 × 10-2 M) in depolarizing medium without Ca2+ only at 500 or 750 µg/mL. Likewise, on S-(–)-Bay K 8644-induced pre-contractions (10-7 M), the EEtOH-ZR-induced vasorelaxant effect was attenuated. EEtOH-ZR (27, 81, 243 or 500 µg/mL) inhibited contractions induced by cumulative addition of phenylephrine (10-9 - 10-5 M) in endothelium-denuded preparations or by a single concentration (10-5 M) in a Ca2+-free medium. The involvement of K+ channels was evaluated by tetraethylammonium (3 mM); the EEtOH-ZR-induced vasorelaxation was not attenuated. Thus, calcium influx blockade through voltage-operated calcium channels (CaVL) and inhibition of calcium release from intracellular stores are probably underlying EEtOH-ZR-induced cardiovascular effects.