Avaliação das atividades antidiarréica e antiespamódica de Solanum asterophorum Mart. (Solanaceae).

Abstract

Solanum asterophorum is a shrub popularly known as "jurubeba-de-fogo . In Brazil, is distributed in the states of Paraíba and Bahia and its roots are popularly used in the treatment of liver diseases. Several species of Solanum are used in folk medicine to treat diarrhea. Oliveira et al. (2006a) showed that the methanol extract from the leaves of S. asterophorum (Sast-MeOHF) has antispasmodic effect in guinea-pig ileum. Therefore, the objective of this study was to investigate and to compare a possible toxic effect and antispasmodic in guinea-pig ileum of the methanol extract obtained from roots of this species (Sast-MeOHR) in guinea-pig ileum, beyond to evaluate the antidiarrhoeal activity of both extracts in mice. Sast- MeOHR (500 mg/mL) induced low hemolytic activity (Emax = 5.2 ± 1.2%). In guineapig ileum, Sast-MeOHR antagonized the phasic contractions induced by 10-6 M carbachol (IC50 = 48.1 ± 8.7 mg/mL) and histamine (IC50 = 105.0 ± 16.2 mg/mL) in a significant and concentration-dependent manner, being Sast-MeOHR 2 times more potent against the carbachol. Sast-MeOHR also presented concentrationdependent spasmogenic effect (EC50 = 137.1 ± 2.8 mg/mL) when applied on the basal tone, which was inhibited in the presence of atropine, a nonselective muscarinic antagonist. Sast-MeOHR inhibited the cumulative curves to carbachol (CCh) and these were shifted to the right of a non-parallel with a reduction in Emax, suggesting a non-competitive antagonism, and relax in a significant and concentration-dependent manner the guinea-pig ileum pre-contracted with 40 mM KCl (EC50 = 52.9 ± 11.5 mg/mL) and with 10-6 M carbachol (EC50 = 20.1 ± 8.6 mg/mL) or histamine (EC50 = 79, 0 ± 15.0 mg/mL), suggestive of the blockade Ca2+ influx through the Cav. Sast-MeOHR antagonized the CaCl2-induced contractions in depolarizing medium nominally without Ca2+ only at concentrations of 500 and 750 mg/mL, suggesting a blockage of the indirect Cav. The fact that the relaxation curve of Sast-MeOHR in guinea-pig ileum pre-contracted with carbachol (EC50 = 20.1 ± 8.6 mg/mL) have been displaced in the presence of 5 mM CsCl, a potassium channels non-selective blocker (EC50 = 92.8 ± 46.1 mg/mL), suggests activation of these channels. In vivo experiments demonstrated a lack of acute toxicity to the dose of 2 g/kg vo and 5 g/kg for i.p to Sast-MeOHR. Besides Sast-MeOHR present an inhibition on both frequency of defecation (ED50 = 309.6 ± 28.5 mg/kg) as liquid stools (ED50 = 152.1 ± 32.5 mg/kg) in a significant and dose-dependent manner. In contrast, Sast-MeOHF presents significant inhibitory effect on the frequency of defecation only in doses of 500 and 750 mg/kg (48.7 ± 7.4 and 42.3 ± 9.8%, respectively). In relation to liquid stools, the Sast-MeOHF showed significant (ED50 = 268.4 ± 35.2 mg/kg) and dose-dependent inhibition, being Sast-MeOHR 2 times more potent to inhibit diarrhea. Both extracts (until 500 mg/kg) did not inhibit intestinal transit. In contrast, both inhibited in a significant and dose-dependent manner, the contents of intestinal fluid induced by castor oil, being Sast-MeOHR (ED50 = 38.3 ± 10.4 mg/kg) 2 times more potent than Sast-MeOHF (ED50 = 78.6 ± 6.4 mg/kg). Suggest that the antidiarrhoeal effect of Sast-MeOHR and Sast-MeOHF involves changes in intestinal secretion, however other studies must be carried out to elucidate the mechanisms involved in these activity. Thus, the extract obtained from the roots was more potent both in vitro experiments and in vivo, suggesting that the active principles with antispasmodic and antidiarrheal action may be more concentrated in roots.