The antidiarrhoeal activity of the aqueous root extract of Aristolochia ringens (Vahl.) Aristolochiaceae.

Background: Aristolochia ringens, an ornamental plant native to tropical America that now grows in a number of African countries has been reported to be used in African traditional medicine for the management of snake bite venom, gastrointestinal disturbances, rheumatoicd arthritis and insomnia among others.

Objective: Based on its use in traditional African medicine, the antidiarrhoeal activity of the aqueous root extract of Aristolochia ringens (AR) was evaluated to determine the pharmacological basis of its use in the management of diarrhoea.

Methods: Normal and castor oil (CO) induced intestinal transit, castor oil induced diarrhoea, gastric emptying and enteropooling models were carried out in mice and rats. Preliminary phytochemical screening and acute toxicity tests were also carried out.

Results: AR (100-400 mg/kg, p.o.) produced a dose-dependent and significant decrease in normal and castor oil-induced intestinal transit compared to the vehicle group. This effect was significantly (p < 0.001) inhibited by pilocarpine (10 mg/kg, s.c.), phentolamine and propranolol (1 mg/kg, i.p.) respectively but neither significantly inhibited by yohimbine (1 mg/kg, s.c.) nor significantly enhanced by isosorbide dinitrate (150 mg/kg, p.o.). AR produced a dose-dependent and significant increase in the latency of diarrhoeal onset. AR also reduced the diarrhoeal score, number and weight of wet stools. The in vivo antidarrhoeal index (ADI(in vivo)) of 81.79 produced by AR (400 mg/kg) is comparable to the 86.85 ADI(in vivo). produced by morphine (10 mg/kg, s.c.). AR also reduced the gastric enteropooling and emptying effects of castor oil. Preliminary screening showed the presence of tannins, saponins and alkaloids. In the acute toxicity study, no mortality was observed with AR administered orally up to 10,000 mg/kg, but an LD50 of 407.38 mg/kg was obtained with the intraperitoneal route of administration in mice.

Conclusion: Results show that the aqueous root extract of Aristolochia ringens possesses antidiarrhoeal activity possibly mediated by its non selective action on adrenoceptors in the GIT and physiological antagonism of the parasympathetic nervous system.