1. Brazilian forests show high diversity of medicinal plants and several are used in folk medicine for the treatment of hypertension and asthma. The aim of the present study was to investigate the effects of a methanol extract (ME) of Cecropia lyratiloba and its flavonoid fraction (FF) on the contractility of cardiac, vascular and tracheal smooth muscles. 2. Twitches of rat papillary muscles were obtained with electrical stimulation and were recorded before and after exposure to increasing concentrations of ME and FF. 3. Cardiac depression was induced by FF. At 500 microg/mL FF, the amplitude of twitches was reduced to 56.7 +/- 5.1% of control values (P < 0.05). 4. The contractile response to a single concentration of adrenaline (10 micromol/L) was measured before and after exposure to ME and FF in rat aorta rings with intact endothelium. Both ME and FF inhibited adrenaline-induced contractions of the aorta in a concentration-dependent manner. Adrenaline-induced contractions were reduced to 46.4 +/- 9.9 and 34.2 +/- 6.9% (P < 0.05) of control in the presence of 500 microg/mL ME and FF, respectively. 5. The flavonoids isolated from FF, namely isoorientin and a mixture of orientin and isovitexin, were also tested in the aorta. These flavonoid do not seem to be responsible for the vasorelaxant effects of ME and FF. 6. No changes were observed in acetylcholine-precontracted trachea when exposed to ME or FF. 7. Endothelium-dependent vasodilation induced by FF is likely to be mediated by the release of nitric oxide because vascular relaxation was abolished in the presence of N(omega)-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase. 8. In conclusion, vascular relaxation induced by ME and FF could explain the traditional use of the extract of C. lyratiloba for treatment of arterial hypertension.

Several plants from the Brazilian Tropical Forest are used in folk medicine for treatment of hypertension and asthma. In this study, we investigated the effects of hexanic extracts of leaves (HLE) and stems (HSE) from Piper truncatum on the contractility of cardiac, vascular and tracheal smooth muscles. Twitches of cardiac muscles obtained with electrical stimulation were recorded before and after exposure to increasing concentrations of hexanic extracts. HLE and HSE respectively reduced significantly the amplitude of twitches to 57.05 +/- 11.63 and 61.58 +/- 5.70% of control in the presence of 100 microg mL(-1). Contractile response to a single concentration of adrenaline (epinephrine) was measured before and after exposure of rat aorta rings to HLE and HSE. Both extracts inhibited aorta contraction in a concentration-dependent manner. The concentration of 50% inhibitory effect (IC50) was 32.3 +/- 13.8 and 47.0 +/- 23.8 microg mL(-1) for HLE and HSE, respectively, in aorta with intact endothelium. HLE and HSE also reduced the acetylcholine-precontracted trachea in a concentration-dependent manner with maximal effect observed at 250 and 350 microg mL(-1), respectively. Vasodilatation and trachea relaxation induced by HLE and HSE could explain the use of Piper extracts to reduce blood pressure and bronchospasm.