Antidiarrheal activities of methanolic crude extract and solvent fractions of the root of Verbascum sinaiticum Benth. (Scrophularaceae) in mice

BACKGROUND: In Ethiopian traditional medicine, V. sinaiticum is one of the most often utilized medicinal herbs for the treatment of diarrhea. Therefore, this study was conducted to validate the use of the plant for the treatment of diarrhea in the traditional medical practice of Ethiopia. METHODS: Castor oil-induced diarrhea, enteropooling, and intestinal motility test models in mice were used to evaluate the antidiarrheal properties of the 80% methanol crude extract and the solvent fractions of the root component of V. sinaiticum. The effects of the crude extract and the fractions on time for onset, frequency, weight, and water content of diarrheal feces, intestinal fluid accumulation, and intestinal transit of charcoal meal were evaluated and compared with the corresponding results in the negative control. RESULTS: The crude extract (CE), aqueous fraction (AQF), and ethyl acetate fraction (EAF) at 400 mg/kg (p < 0.001) significantly delayed the onset of diarrhea. Besides, the CE and AQF at 200 and 400 mg/kg (p < 0.001) of the doses, and EAF at 200 (p < 0.01) and 400 mg/kg (p < 0.001) significantly decreased the frequency of diarrheal stools. Furthermore, CE, AQF, and EAF at their three serial doses (p < 0.001), significantly reduced the weights of the fresh diarrheal stools as compared to the negative control. The CE and AQF at 100 (p < 0.01), and 200 and 400 mg/kg (p < 0.001) of their doses and EAF at 200 (p < 0.01) and 400 mg/kg (p < 0.001) significantly decreased the fluid contents of diarrheal stools compared to the negative control. In the enteropooling test, the CE at 100 (p < 0.05), and 200 and 400 mg/kg (p < 0.001), AQF at 200 (P < 0.05) and 400 mg/kg (p < 0.01), and EAF at 200 (p < 0.01) and 400 mg/kg (p < 0.001) significantly decreased the weights of intestinal contents compared to the negative control. Additionally, the CE at 100 and 200 (p < 0.05) and 400 mg/kg (p < 0.001), AQF at 100 (p < 0.05), 200 (p < 0.01), and 400 mg/kg (p < 0.001) of the doses, and EAF at 400 mg/kg (p < 0.05), produced significant reductions in the volumes of intestinal contents. In the intestinal motility test model, the CE, AQF, and EAF at all their serial doses (p < 0.001), significantly suppressed the intestinal transit of charcoal meal and peristaltic index compared to the negative control. CONCLUSION: Overall, the results of this study showed that the crude extract and the solvent fractions of the root parts of V. sinaiticum had considerable in vivo antidiarrheal activities. Besides, the crude extract, especially at 400 mg/kg, produced the highest effect followed by the aqueous fraction at the same dose. This might indicate that the bioactive compounds responsible for the effects are more of hydrophilic in nature. Moreover, the antidiarrheal index values were increased with the doses of the extract and the fractions, suggesting that the treatments might have dose-dependent antidiarrheal effects. Additionally, the extract was shown to be free of observable acute toxic effects. Thus, this study corroborates the use the root parts of V. sinaiticum to treat diarrhea in the traditional settings. Furthermore, the findings of this study are encouraging and may be used as the basis to conduct further studies in the area including chemical characterization and molecular based mechanism of actions of the plant for its confirmed antidiarrheal effects.