Introduction. Diarrheal diseases are associated with an estimated 1.3 million deaths annually, with most occurring in resource-limited countries; up to 25% of deaths in young children living in Africa and southeast Asia are attributable to acute gastroenteritis. Due to limitations associated with various treatments available, the need for developing newer drugs is imperative. Objective. This study was aimed to evaluate the antidiarrheal activity of root extract and fractions of C. abyssinica Jaub. & Spach. (Euphorbiaceae) in mice. Methods. After plant extraction and subsequent fractionation of the crude extract, the antidiarrheal activity was screened in castor oil induced diarrhea, castor oil induced enteropooling, and gastrointestinal motility test models accordingly. Result. The root extract of C. abyssinica produced neither visible signs of toxicity nor death at a single dose of 2000 mg/kg, suggesting the LD50 > 2000 mg/kg. In the castor oil induced diarrheal model, the highest dose of the extract (400 mg/kg) showed a maximal inhibition in the onset (158.00 ± 14.64, , in minutes) of wet feces as compared to the negative control. In the enteropooling model, 400 mg/kg treated mice showed a significant reduction in volume (0.47 ± 0.02 ml, ) and weight (0.50 ± 0.02 g, ) of intestinal content as compared to the vehicle treated group. In the gastrointestinal motility test, the hydromethanolic root extract of C. abyssinica significantly inhibited the intestinal transit of charcoal meal at 400 mg/kg. In addition, chloroform and n-butanol fractions significantly reduced the distance moved by charcoal at doses of 200 mg/kg and 400 mg/kg, whereas aqueous fraction showed a significant effect at all test doses. The highest antidiarrheal index was observed at the maximal dose of extract and each fraction. Conclusion. The results obtained showed that the findings provide scientific support for the folkloric repute of C. abyssinica roots as treatment of diarrhea.

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