The fight against malaria encounters a problem of resistance of plasmodium to available molecules. The most effective antimalarials, quinine and artemisinin, come from the plants Cinchona calisaya Weed and Artemisia annua L. used in the traditional Peruvian and Chinese pharmacopoeia, respectively. It is therefore important to             have scientific data on traditional remedies. These scientific data could contribute to the discovery of new antimalarial molecules. With this in mind, we conducted a phytochemical study, evaluating the antiplasmodial activity and the acute toxicity of the extracts of the stem bark of Alstoniaboonei De Wild, a plant used in the treatment of malaria, in traditional medicine in Congo. Secondary metabolites were characterized by color and precipitation reactions according to conventional methods. Total alkaloids were obtained after maceration with water acidified with concentrated sulfuric acid, and extraction with chloroform. The antiplasmodial activity of the aqueous extract and of the total alkaloids was evaluated, In-Vitro, by the optical micro-test method, on blood parasitized by Plasmodium falciparum. The study of the acute toxicity of the aqueous extract was carried out according to the method described by OECD guideline No. 423. The chemical families identified in the aqueous extract of the stem bark of Alstoniaboonei are alkaloids, tannins, flavonoids and saponosides. Quantitative analysis of the alkaloids gave a yield of 6.33 ± 0.02%. For antiplasmodial activity, the 50% inhibitory concentrations (IC50) of our extracts are 111.2 µg / mL for the aqueous extract and 116.4 µg / mL for the alkaloid extract. These results allow us to conclude that, the antiplasmodial activity is linked to the presence of alkaloids in the plant. Regarding the acute toxicity of the aqueous extract, the lethal dose at 50% (LD50) is greater than 5000 mg/kg, the plant is not toxic.

Keywords: Alstoniaboonei, Aqueous extract; Phytochemistry, Total alkaloids,  Antiplasmodial,  Acute toxicity