Diarrhoea is a leading cause of deaths in developing countries, especially in children, and contributes to one in five deaths of children all over the world. The burden and mortality due to diarrhoea diseases have encouraged the development and the patronage of herbal alternatives. In this study we investigated the methylene chloride-methanol leaf extract of Pterocarpus santalinoides (PSE), a plant believed to possess potent antidiarrhoeal properties in folk medical practice. The antidiarrhoeal and anti-enteropooling activity of PSE were investigated in castor oil induced diarrhoea in rats. The effect on gastrointestinal motility was studied by the charcoal meal transit in mice. Smooth muscle activity of the extract was investigated in isolated guinea pig ileum. P. santalinoides extract (100-500 µg/ml) caused a significant and dose-related inhibition of the frequency of diarrhoeic drops in rats (P< 0.05) and prolonged the time for diarrhoea induction. The extract also exhibited significant anti-enteropooling activity (P<0.05). The extract (500 mg/kg) inhibited propulsion of the charcoal meal through the gastrointestinal tract in mice, and this effect was comparable to that of atropine (2.5 mg/kg). In vitro, the contractile responses produce by histamine and acetylcholine were inhibited by PSE with IC50 of 59.93 and 57.01 µg/ml, respectively; but serotonin-evoked contraction was unaffected. The claimed benefits of P. santalinoides in traditional medical management of diarrhoea could be supported by the results of this investigation.
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