A number of 235 crude extracts originally obtained from plants reputed as antiparasitic in the traditional medicine in Sudan have been solicited from the depository of the Faculty of Pharmacy, University of Science & Technology. The extracts were screened against Plasmodium falciparum, Trypanosoma brucei rhodesiense, T. cruzi trypomastigote forms, and Leishmania donovani. Assays were based on Alamar blue protocols for T. brucei and L. donovani, β-glactosidase assay for T.cruzi, and [3H]-hypoxanthine incorporation protocol for P. falciparum. Assays were performed in 96-well format, and standard reference drugs for each parasite were used as positive controls [1]. Of the 235 plant extracts tested, 161 samples showed inhibitory activity > 80% at 10 μg/ml, and > 50% at 2 μg/ml against one or more of the selected parasites. Among them, 23% fulfilled activity criteria against T. b. rhodesiense, L. donovani and P. falciparum; 18% were active against both L. donovani and P. falciparum, and 17% were active against both T. b. rhodesiense and P. falciparum with few extracts (< 3%) exhibited activity against T. cruzi.
Ethyl acetate fractions of the leaves of Acacia nilotica, Guiera senegalensis, Ziziphus spina-christi, Anogeissus leiocarpus and the bark of Terminalia laxiflora were among the most active samples. In order to associate bioactivity of the extracts with their HPLC chromatographic profiles coupled with their corresponding on-line spectroscopic data, the bioactive samples were submitted to HPLC-based activity profiling [2]. The isolation and structure elucidation of the antiparasitic compounds is well under progress.
References:
1. Adams, M., et al., A protocol for HPLC-based activity profiling for natural products with activities against tropical parasites. Natural product communications, 2009. 4(10): p. 1377-1381.
2. Potterat, O. and M. Hamburger, Combined use of extract libraries and HPLC-based activity profiling for lead discovery: potential, challenges, and practical considerations. Planta medica, 2014. 80(14): p. 1171-1181.