Engidawork, Ephrem (PhD)Shibeshi, Workineh(PhD)Degu, Amsalu2018-06-212023-11-062018-06-212023-11-062014-10http://etd.aau.edu.et/handle/123456789/2460Traditional healers in Ethiopia use a wide range of medicinal plants with antidiarrheal properties. Among these, Croton macrostachyus is one such plant claimed to have an antidiarrheal activity in Ethiopian folklore medicine. Previous studies showed that the crude extract is endowed with the claimed property and this study was undertaken to further the claim by screening different fractions for the said activity so that it could serve as a basis for subsequent studies. The fractions were obtained by successive soxhlet extraction with solvents of differing polarity (chloroform & methanol) followed by cold maceration of the marc of the methanol fraction with distilled water. The antidiarrheal activity was evaluated using castor oil induced diarrheal model, charcoal meal test and anti-enteropooling test in mice. The test groups received various doses (300, 400, 500 mg/kg and an additional dose of 1000 mg/kg for the aqueous fraction) of the fractions, whereas positive controls received either Loperamide (3 mg/kg) or Atropine (5 mg/kg) and negative controls received vehicle (10 ml/kg). In the castor oil induced model, the chloroform (at all test doses) and methanol (at 400 & 500 mg/kg) fractions significantly prolonged diarrheal onset, decreased the frequency of stooling and weight of feces. The aqueous fraction was, however, devoid of significant effect at all doses tested. Similarly, in the enteropooling test, whilst the chloroform and methanol fractions produced a significant dose dependent decline in the weight and volume of intestinal contents, the aqueous fraction was without appreciable effect. Results from the charcoal meal test revealed that all the fractions produced a significant anti-motility effect either at all iv doses (chloroform fraction) or at middle and higher doses (methanol and aqueous fractions). Taken together, the present study demonstrated that the chloroform and methanol fractions possessed significant anti-diarrheal activity due to its inhibitory effect on castor oil induced gastrointestinal propulsion and fluid secretion. Nevertheless, the aqueous fraction showed only significant anti-motility effect at the higher dose (1000 mg/kg) employed in the study. Key words: Antidiarrheal activity, Castor oil induced diarrhea, gastrointestinal transit, anti-enteropooling, Croton macrostachyusenAntidiarrheal activity, Castor oil induced diarrhea; Gastrointestinal transit; Anti-enteropooling; Croton macrostachyusThesis