Acute and sub-chronic toxicity studies of an aqueous stem bark extract of Sclerocarya birrea using a rat model. Tariro Mawoza 1* , Dexter Tagwireyi 2 and Charles Nhachi 3 1. Lecturer/PhD Fellow University of Zimbabwe Clinical Pharmacology Department 2. Associate Professor University of Zimbabwe School of Pharmacy 3. Professor University of Zimbabwe Clinical Pharmacology Department University of Zimbabwe, P.O. Box A178, Avondale, Harare *Email: tmawoza@gmail.com 00263774 414 744 Abstract Background: Sclerocarya birrea, a plant that is commonly available in many communities, is used as a source of food and for ethnomedicinal and cultural practices. Stem-bark toxicity studies for the plant are however lacking. This study was therefore conducted in an effort to determine its toxic effects using a rat model. Methods: Acute toxicity was performed using a single oral administration of 50, 100, 200, 400, 800, 1000 and 2000mg/kg body weight of S. birrea to determine the lethal dose. Test animals in the sub-chronic study received 50, 100, 200, 400, 800, 1000 and 2000mg/kg body weight of S. birrea for 28 days. Results: No animal mortality occurred during acute toxicity testing, suggesting that the lethal dose is probably higher than 2000mg/kg body weight. Behavioural and posture changes were however observed with the higher doses. During the sub-chronic test, animals in the 1000mg/kg and 2000mg/kg groups showed a significantly (p<0.05) smaller growth rate as compared to the animals in the other groups. Significant organ to body weight ratio changes were observed only in the livers and kidneys of animals that received 800, 1000mg/kg and 2000mg/kg body weight of S. birrea suggesting possible toxicity. This was supported by increases in direct bilirubin, total protein, albumin, AST and ALT. In addition, histopathological changes to the liver and kidneys were observed with increasing dosages of the plant extract. Conclusions: The results of the study indicate that at doses of ≥1000mg/kg, the extract affects growth rate as well as liver and kidney function. Therefore, high doses should be used with caution. Key words: Acute toxicity, Sclerocayra birrea, Stem bark, Sub-chronic toxicity. Introduction A large percentage of the population in developing countries relies heavily on traditional medicine practitioners and herbal plants to meet their primary healthcare needs. The high cost of medicines, and concurrent shortage of drugs, has necessitated the need for many people in several African countries to go back to the old ways of using traditional herbal concoctions and decoctions for their ailments [1]. The disadvantage however, is that most of the traditional medicinal plants have never been exposed to toxicological tests such as those required for modern pharmaceutical compounds [2,3], and little to no research has been carried out based on WHO guidelines on the safety and efficacy of herbal medicines. The reason for this is that medicinal plants are often assumed to be safe based on their past traditional use, and they also provide a cheaper alternative as compared to modern medicine [4]. Phytochemical studies by numerous researchers have however, shown that a large number of these plants have in vitro toxic, mutagenic and/or carcinogenic effects [5,6]. The toxicity and adverse effects of African medicinal plant use may arise due to a number of factors or issues including inherent poisonous phytochemicals, adulteration of the medicines, contamination with various chemicals and heavy metals, herb-drug interactions, and poor quality control of herbal products [7]. As a result, there has been increased emphasis on research and development focused on the safety, efficacy and quality of medicinal plants as they might be developed into medicinally useful drugs. Sclerocarya birrea, a tree that grows abundantly in southern Africa, is an example of a plant commonly used by local communities whose toxicity profile is still lacking. Numerous communities use the plant as a source of food, and for ethnomedicinal and cultural practices [8]. The tree is one of the greatest trees indigenous to Africa, with different species occurring from Ethiopia in the north, to KwaZulu-Natal Province in the south [9]. Every part of the plant is utilised either for nutrition or medicinally. The stem bark, roots and leaves of S birrea are used traditionally to treat malaria and fevers, diarrhoea and dysentery, headaches, toothache, backache and body pains, schistosomiasis, epilepsy, general musculo-skeletal system disorders, diabetes mellitus, circulatory Tariro Mawoza et al./ International Journal of Pharma Sciences and Research (IJPSR) ISSN : 0975-9492 Vol 7 No 01 Jan 2016 9