Ex vivo trypanostatic effect of stem-bark extracts of Securidaca longipedunculata (Fres. Holl) against Trypanosoma brucei brucei

Abstract

Current treatment of trypanosomosis in sub-Saharan Africa is associated with widespread inefficiency.
There is therefore the need to find more effective drugs against the disease from promising traditional
medicinal herbs. This work is aimed at evaluating ex vivo anti-trypanosomal effect of stem-bark extracts of S. longipedunculata against T. brucei brucei. One hundred microlitre of crude methanol, ethyl acetate and aqueous methanol extracts of S. longipedunculata at concentrations of 3 and 6 mg/ml each were mixed with 50 μl of blood containing 8.1 × 106 trypanosomes and incubated at 37°C for 90 min. Similarly, diminazene aceturate (10 μg/ml), physiological saline solution (50 μl) and blood (100 μl) containing trypanosomes only served as treated, negative and untreated controls, respectively. Motility of the parasite was monitored under light microscope (×400) at 5 min interval throughout the 90 min
observation period. All experiments were done in duplicate. The mixtures were subsequently inoculated
into rats that were not previously infected with trypanosomes. Phytochemical screening of the extracts
revealed the presence of carbohydrates, cardiac glycosides, saponins, steroid, triterpenes, flavonoids
and tannins. However, aqueous and ethyl acetate fractions were devoid of flavonoids. The crude methanol immobilized the parasites within 75 min, while ethyl acetate and aqueous extracts induced
slight reduction in motility of the parasite at 90 min of incubation. However, inoculated rats developed
infection and succumbed to the infection. It is concluded that the stem-bark of the plant possesses
trypanostatic, but not trypanocidal, activity against the parasite.

Key words: Antitrypanosomal, drug incubation infectivity test, in vitro, phytochemical screening, stem-bark.