1. Faculty of Pharmacy, University of Khartoum, Khartoum 11111, Sudan
2. Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Allschwil, 4123 Basel, Switzerland
3. Faculty of Science, University of Basel, 4001 Basel, Switzerland
4. Department of Microbial Natural Products, Helmholtz Institute for Pharmaceutical Research Saarland, 66123 Saarbruecken, Germany
5. Department of Microbial Drugs, Helmholtz Centre for Infection Research (HZI), 38124 Braunschweig, Germany