| Summary: | <i>Piper amalago</i> L. is used in Brazilian traditional medicine to treat inflammation, chest pain, and anxiety. This study aimed to investigate the safety and the renal and cardiovascular effects of the volatile oil (VO) and the aqueous (AE) and hydroalcoholic (HE) extracts from <i>P. amalago</i>. The gas chromatography-mass spectrometry analyses identified 47 compounds in the VO, with β-cyclogermacrene, spathulenol, β-phellandrene, and α-pinene standing out. Among the 47 compounds also found in AE and HE by liquid chromatography-mass spectrometry, glycosylated flavones, organic acids, amino acids, and amides were highlighted. Some examples of these compounds are methoxy-methylenedioxy <i>cis</i>-cinnamoyl pyrrolidine, methoxy-methylenedioxy <i>trans</i>-cinnamoyl pyrrolidine, and cyclobutene-2,4-<i>bis</i>-(1,3-benzodioxol-5-methoxy-6-yl)-1,3-dicarboxapyrrolidide. The acute toxicity experiments were conducted on female rats (<i>n</i> = 5). The cardiorenal assays (<i>n</i> = 8) and evaluations of vasodilatory effects on the mesenteric vascular bed (<i>n</i> = 5) were conducted on male rats. In either extract or VO, there were no mortality or changes in relative weights or histopathological analysis of the organs. Urinary volume and renal electrolyte excretion were elevated significantly during repeated dose 7-day treatment with different preparations from <i>P. amalago</i>. None of the preparations induced hypotension or changes in cardiac electrical activity. Only HE promoted significant vasodilatory effects in rats’ isolated mesenteric vascular beds. These effects were completely abolished in the presence of L-NAME <i>plus</i> 4-aminopyridine. Therefore, <i>P. amalago</i> leaves are safe and present diuretic activity after acute and repeated dose administration over 7 days. Moreover, the HE induced significant vasodilator response in rats’ mesenteric vascular beds by NO/cGMP pathway and voltage-dependent K<sup>+</sup> channels activation.
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