Ethnopharmacological relevance encompasses the aqueous bark extract of Lannea welwitschii (Hiern), LW is used in Traditional African Medicine (TAM) for the treatment of diarrhea. However, the scientific basis for this usage has not been established. To evaluate the antidiarrhoel activity of LW using various pharmacological methods. The intestinal transit, castor oil induced diarrhea, enteropooling and gastric emptying methods were used in this study. LW (50 - 400 mg/kg per oral (p.o)) produced significant (P < 0.05) dose dependant reduction in propulsive movement in both the normal and castor oil induced intestinal transit tests in mice. Peak effect was elicited at 200 mg/kg but this effect was lower than that produced by morphine (10 mg/kg, s.c). The effect of LW on castor oil induced intestinal transit was antagonized by isosorbide dinitrate, IDN (150 mg/kg, P.O.), but not by yohimbine (1 mg/kg s.c.) LW produced a significant decrease in the frequency of defecation, severity of diarrhea and protection from diarrhea in mice treated with castor oil. Also, LW at the dose of 400 mg/kg, significantly (P < 0.05) inhibited the castor oil induced intraluminal fluid content. The acute toxicity tests carried out showed a well tolerated effect of the drug via the oral route, a dose of 20 g/kg produced no death in the animals. The LD₅₀ was 631 mg/kg given i.p. Phytochemical analysis revealed the presence of alkaloids, saponins, tannins, anthraquinones and reducing sugars. The results obtained in this study suggest that the aqueous bark extract of L. welwitschii possesses antidiarrhoel property due to inhibition of gastrointestinal propulsion and fluid secretion possibly mediated through inhibition of the nitric oxide pathway. This justifies the use of the plant extract in TAM for the treatment of diarrhea.

 

Key words: Lannea welwitschii, diarrhea, antidiarrhoeal activity, intestinal transit, enteropooling, gastric emptying.