Evaluation of the antidiarrhoeal activity of Byrsocarpus coccineus

Based on its use in traditional African medicine, the antidiarrhoeal activity of the aqueous leaf extract of Byrsocarpus coccineus, Connaraceae, was evaluated on normal and castor oil-induced intestinal transit, castor oil-induced diarrhoea, enteropooling and gastric emptying. The extract (50, 100, 200 and 400 mg/kg, p.o.) produced a significant (P<0.05) dose dependent decrease in propulsion in the castor oil-induced intestinal transit in mice. The mean peristaltic index (%) for these doses of extract, control (distilled water; 10 ml/kg, p.o.) and morphine (10 mg/kg, s.c.) were 55.27+/-1.86, 53.12+/-3.73, 38.60+/-3.79, 30.25+/-1.27, 89.33+/-5.62 and 20.29+/-3.38, respectively. The effect of the extract at the highest dose was significantly (P<0.05) lower than that of the standard drug. This effect was antagonised by yohimbine (1 mg/kg, s.c.) but not by isosorbide dinitrate (IDN, 150 mg/kg, p.o.). At 200 mg/kg, the extract produced a significant decrease in propulsion in normal intestinal transit. In a dose dependent manner, it delayed the onset of diarrhoea, produced a significant decrease in the frequency of defaecation, severity of diarrhoea and protected the mice treated with castor oil. Mean diarrhoea scores were 30.83+/-1.72, 22.40+/-1.71, 21.43+/-1.32, 13.80+/-0.33, 18.00+/-3.94 and 7.67+/-2.41 for control, extract (50, 100, 200 and 400 mg/kg) and morphine, respectively. This effect was not antagonized by IDN. The extract (400 mg/kg) significantly decreased the volume (ml) of intestinal fluid secretion induced by castor oil (0.60+/-0.23) compared with 1.27+/-0.12 for control. However, there was no significant effect on gastric emptying. The results obtained suggest that Byrsocarpus coccineus possesses antidiarrhoeal activity due to its inhibitory effect on gastrointestinal propulsion, mediated through alpha(2) adrenoceptors, and also inhibition of fluid secretion. Preliminary phytochemical analysis revealed the presence of alkaloids, tannins, saponins, reducing sugars, glycosides and anthraquinones.