Mining Sudanese Medicinal Plants for Antiprotozoal Agents

Neglected tropical diseases are major health hazards in developing countries. Annually, up to 30 million people are affected by either Chagas disease, African trypansomiasis or leishmaniasis, and more than 200 million by malaria. Most of the currently available drugs have drawbacks in terms of toxicity, limited oral availability, development of resistance, or non-affordability. Tropical plants of the arid zones are a treasure chest for the discovery of bioactive secondary metabolites. This study aims to compile Sudanese medicinal plants, validate their antiprotozoal activities, and identify active molecules. We have performed a survey of medicinal plants of Sudan and selected 62 that are being used in Sudanese traditional medicine. From these, we collected materials such as leaves, stem, bark, or fruit. The plant materials were extracted in 70% ethanol and further fractionated by liquid-liquid partitioning using solvents of increasing polarity. This resulted in a library of 235 fractions. The library was testedin vitroagainstPlasmodium falciparum(erythrocytic stages),Trypanosoma brucei rhodesiense(bloodstream forms),Trypanosoma cruzi(intracellular amastigotes), andLeishmania donovani(axenic amastigotes). Active fractions were also tested for cytotoxicity. Of the 235 fractions, 125 showed growth inhibitory activity >80% at 10 mu g/ml, and >50% at 2 mu g/ml against at least one of the protozoan parasites.Plasmodium falciparumwas the most sensitive of the parasites, followed byT. b. rhodesienseandL. donovani. Only few hits were identified forT. cruzi, and these were not selective. Contrary to expectation based on phylogeny, but in agreement with previous results, a large number of extracts displayed mutual activity againstT. bruceiandP. falciparum. HPLC-based activity profiling for selected active extracts was performed to identify the bioactive principles. Active compounds identified by dereplication were guieranone A fromGuiera senegalensisJ.F.Gmel.; pseudosemiglabrin fromTephrosia apollinea(Delile) DC; ellagic acid and quercetin fromTerminalia leiocarpa(DC.) Baill.; and catechin, ethyl gallate, and epicatechin gallate fromVachellia nilotica(L.) P.J.H.Hurter & Mabb. Also the extracts ofCroton gratissimusvar.gratissimusandCuscuta hyalinaRoth ex Schult. exhibited promising antitrypanosomatid activity. This assessment provides a comprehensive overview of Sudanese medicinal plants and supports the notion that they are a potential source of bioactive molecules against protozoan parasites.