Inhibition of in-vitro growth of Plasmodium falciparum by Pseudocedrela kotschyi extract alone and in combination with Fagara zanthoxyloides extract.

Roots of Pseudocedrela kotschyi are commonly used as chewing sticks in West Africa. This study examined the effects of the plant extract on the in-vitro growth of Plasmodium falciparum. Ring-stage synchronised cultures of the malaria parasite were exposed to 30 and 60 microg/ml of P. kotschyi extract for 51 h. Aliquots were taken from the cultures every 3 h for preparation of Giemsa-stained thin films, which were evaluated by light microscopy for degree of parasitaemia and stage distribution of parasite development. The extracts did not show any inhibitory effects on the emergence of trophozoites in treated cultures. However, the results indicate that 80% of inhibition of the parasite transformation into schizont was obtained for both tested concentrations (30 and 60 microg/ml). Experiments with (3)H-hypoxanthine incorporation showed an IC(50) of 16 microg/ml for the Pseudocedrela extract. Pseudocedrela was combined with extract of Fagara zanthoxyloides in various concentrations to determine their interactive effects on the in-vitro cultures. Isobologram analysis of the results indicated a synergistic interaction between the two extracts at low concentrations, while interactions at higher concentrations showed antagonistic effects.