Ethnopharmacological relevance: The leaves of Pterocarpus santalinoides are used alone or with other plants by traditional healers in some Southern Nigerian and Ivorian rural villages to treat blood parasitic infections including trypanosomiasis and malaria. However, their efficacy and safety remains doubtful. Aim: To evaluate the antitrypanosomal activity of Pterocarpus santalinoides hydroethanol leaf extract (PSELE) in vitro and in vivo. Materials and methods: The phytochemical and acute toxicity studies of PSELE were performed using standard methods. Eleven different concentrations of the extract were screened for in vitro antitrypanosomal activity. For the in vivo study, twenty-five female albino rats were randomly assigned into five groups of five rats each. Group A was the uninfected and untreated group while groups B - E were infected intraperitoneally with 10(6) trypanosomes. Group C rats were treated once on day 11 post infection (PI) with 7 mg/kg diminazene aceturate while groups D and E rats were also treated on same day with 200 mg/kg and 400 mg/kg PSELE respectively for seven days. The level of parasitaemia (LOP), survivability, packed cell volume (PCV), total leucocyte count (TLC), total erythrocyte count (TEC), body weight and rectal temperature were used to assess the antitrypanosomal effect of PSELE. Results: Phytochemical analysis revealed the presence of flavonoids, tannins, carbohydrates and reducing sugar. No sign of toxicity or mortality was observed following acute toxicity study at a single dose of 2000 mg/kg. The LC50 of PSELE was 0.0625 mg/ml. Parasitaemia was first detected on day 8 and all infected rats became parasitaemic on day 10 (PI). PSELE significantly reduced (p < 0.05) LOP, improved PCV, TEC and prolonged survival time of the rats compared with the infected untreated group B. Conclusion: It was therefore concluded that PSELE is safe, possesses some antitrypanosomal activity and may serve as a lead for the development of an effective alternative antitrypanosomal drug.
