Chemotherapeutic effects of Annona senegalensis in Trypanosoma brucei brucei

Abstract

Mice infected with Trypanosoma brucei brucei 8/18 strain were treated orally and intramuscularly (im) with aqueous root extracts of Annona senegalensis, in doses of 27.8 mg kg⁻¹ and 9.5 mg kg⁻¹ respectively, for four consecutive days commencing 72 hours after the mice were infected. At these dosages the parasites were cleared from the circulation and no relapse was recorded over 60 days. The plant extract, however, had no effect on the trypanosomes when therapy was initiated at the late stages of infection, that is, about the sixth day when the parasitaemia level was 0·9 × 10⁶; and all the animals died a day or two later. The herbal extracts also did not show any prophylactic action when given prior to infection.

The root extract possesses different margins of safety in the mice depending on the route of administration. The therapeutic index for oral administration was 5·13, and that for im administration was 1·8. Chemical tests revealed that the plant extract contains alkaloids, saponins and tannins.

Adverse reactions, especially to doses of 2·3–5·76 mg kg⁻¹, were noted in animals that received the drug parenterally, but not when the drug was administered orally. However, A. senegalensis is shown to be therapeutically effective against T. b. brucei in mice, which agrees with the claims of Nigerian practitioners of Traditional Medicine that it is effective against trypanosomiasis in man.