ANTIDIARRHOEAL AND TOXICITY STUDIES ON METHANOL LEAF EXTRACT OF COMBRETUM HYPOPILINUM DIELS (COMBRETACEAE) IN MICE AND RATS

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Department of Pharmaceutical Sciences

ABSTRACT
The plant Combretum hypopilinum has been used in traditional medicine to treat diarrhoea and other gastrointestinal diseases. This study aimed to investigate the antidiarrhoeal activity and toxicity profile of the methanol leaf extract of Combretum hypopilinum (MECH) in mice and rats. The phytochemical screening was conducted and the oral median lethal dose (LD50) was determined using standard methods. Antidiarrhoeal activity of MECH (250, 500 and 1,000 mg/kg) was evaluated using castor oil-induced diarrhoea, castor oil-induced enteropooling and intestinal motility tests. The probable mechanisms of antidiarrhoeal activity of MECH were investigated following pretreatment with naloxone, prazosin, yohimbine, propranolol, pilocarpine and isosorbide dinitrate. For the sub-acute toxicity study, the extract was orally administered to rats daily for 28-days at the doses of 250, 500, and 1,000 mg/kg. Mortality and weekly body weight were observed. The animals were sacrificed on the 29th day and blood samples were collected into ethylenediaminetetraacetic acid (EDTA) and plain bottles to analyse haematological and biochemical parameters. The liver, kidney, heart, lung, small intestine, and stomach were removed and their relative organ weight was determined. The organs were examined for histopathological changes. Phytochemical screening revealed the presence of flavonoids, cardiac glycosides, saponins, tannins, steroids, triterpenes and alkaloids. The oral LD50 was higher than 5,000 mg/kg in mice and rats. The extract at the dose of 500 and 1,000 mg/kg significantly (p?0.05) reduced the number of diarrhoea stools, intestinal fluid volume (p?0.05 and p?0.01) and charcoal movement (p?0.05 and p?0.001) respectively. The pretreatment of the animals with naloxone, prazosin and propranolol each significantly (p?0.01) reduced the antidiarrhoeal activity of the extract by increasing the charcoal movement. However, pretreatment of the animals with yohimbine, pilocarpine and isosorbide dinitrate did not significantly (p>0.05) change the antidiarrhoeal activity of the MECH. The extract at the dose of 500 mg/kg significantly (p?0.05) reduced the body weights of the animals in the first and second week. There was significant (p?0.05 and p?0.01) reduction in relative kidney weight at the dose of 500 and 1,000 mg/kg. The extract significantly reduced the alkaline phosphatase (ALP) p?0.01 (500mg/kg) and p?0.001 (1,000 mg/kg), glucose p?0.01 (1,000 mg/kg), potassium (p?0.01, p?0.001 and p?0.001), and low density-lipoprotein (LDL) p?0.01 (250 mg/kg), p?0.001 (500 mg/kg) and p?0.05 (1,000 mg/kg). There was no significant (p>0.05) difference in white blood cells, lymphocytes, red blood cells, haemoglobin, haematocrit, mean corpuscular volume, mean corpuscular haemoglobin and mean corpuscular haemoglobin concentration. There was a significant (p?0.05) increase in the percentage of eosinophils, basophils and monocytes and an increase in granulocyte (p?0.01) at the dose of 1,000 mg/kg. The extract significantly (p?0.01) increased the platelet levels at a dose of 500 mg/kg. There were histopathological abnormalities on the kidney, lung, stomach, and small intestine. The MECH possesses antidiarrhoeal activity possibly through its interaction with opioidergic and (α1 and β)- adrenergic systems. The extract is relatively safe on acute exposure but moderately toxic at higher doses on sub-acute administration particularly to the kidney.