| Extracts of Anogeissus leiocarpus, Fagara zanthoxyloides, Pseudocedrela kotschyi, and Terminalia glaucescens were evaluated for their in vitro antiproliferative properties against Trypanosoma cruzi and for cytotoxicity on control NIH 3T3 fibroblast cells. The methanol root bark extract of A.leiocarpus showed a significantly higher potency (IC50 = 0.82 mug/ml) than the other three extracts and nifurtimox, which was used as a positive control. However, no significant differences in the antitrypanosomal activity were found among the other three treatments. F.zanthoxyloides had an IC50 of 6.42 mug/ml. P.kotschyi showed an IC50 of 8.94 mug/ml, with 9.04 mug/ml for T.glaucescens and 7.70 mug/ml for nifurtimox. The cytoxicity experiments indicated that extracts of A. leiocarpus and P.kotschyi are significantly less toxic for fibroblasts than extracts of F.zanthoxyloides, T.glaucescens and nifurtimox. The oral acute toxicity results revealed that methanol extracts of A.leiocarpus and P.kotschyi were also not toxic in BAL/C mice, as aspartate aminotransferase (AST) and alanine aminotransferase (ALT) measurements were within normal ranges. A.leiocarpus and P.kotschyi extracts were, therefore, selected for subsequent experiments because of their higher selectivity values. Also treatment of T.cruzi epimastigotes with the extracts yielded minimum inhibitory concentrations (MICs) of 36.82 mug/ml for A.leiocarpus and 540 mug/ml for P.kotschyi. The results of other experiments indicated that the trypanocidal activity of the extracts may be mediated by apoptosis, as evident from the demonstration of in situ DNA nicking of treated parasites, the detection of a caspase-3 like activity and the externalization of phosphatidylserine on surface membranes of treated parasites. Morphological studies by electron microscopy showed swelling of surface membrane and disruption of the flagellum in parasites that were treated with the two extracts. These results collectively demonstrate that A.leiocarpus and P.kotschyi extracts are very active against T.cruzi and should be considered as sources for the isolation of potential anti-trypanosomal compounds. |
