BackgroundIn Ethiopia, Calpurnia aurea is used for the treatment of syphilis, malaria, rabies, diabetes, hypertension, diarrhoea, leishmaniasis, trachoma, elephantiasis, fungal diseases and different swellings. However, despite its traditional usage as an antidiarrhoeal and antimicrobial agent, there is limited or no information regarding its effectiveness and mode of action in diarrhoea which may be caused by Shigella flexneri, Staphylococcus aureus, Escherichia coli and Salmonella typhi. Hence, we evaluated the 80% methanol (MeOH) extract of dried and powdered leaves of C. aurea for its antidiarrhoeal and antimicrobial activities.MethodsSwiss albino mice of either sex were divided into five groups (five/group): Group I served as control and received vehicle (1% Tween 80) at a dose of 10 ml/kg orally; Group II served as standard and received loperamide at the dose of 3 mg/kg orally; Groups III, IV and V served as test groups and received the 80% MeOH leaf extract of C. aurea at doses of 100, 200 and 400 mg/kg orally, respectively. Diarrhoea was induced by oral administration of 0.5 ml castor oil to each mouse, 1 h after the above treatments. During an observation period of 4 h, time of onset of diarrhea, total number of faecal output (frequency of defecation) and weight of faeces excreted by the animals were recorded. Data were analyzed using one way analysis of variance followed by Tukey post test. Antimicrobial activity test was conducted using agar well diffusion assay. Clinical isolates tested were Salmonella typhi, Salmonella paratyphi, Salmonella typhimurium, Shigella species, Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli.ResultsIn castor oil induced diarrhea model, the 80% methanol leaf extract of C. aurea at 100, 200 and 400 mg/kg and the standard drug loperamide (3 mg/kg) significantly reduced the time of onset of diarrhea, the frequency of defecation (total number of faecal output) and weight of faeces. C. aurea leaf extract also showed good antimicrobial activity against all tested organisms.ConclusionsC. aurea possesses good antidiarrhoeal and antimicrobial activity which support the traditional use of the plant in the treatment of diarrhea in Ethiopia.