1. Helmholtz-Institute for Pharmaceutical Research Saarland (HIPS), Helmholtz Centre for Infection Research (HZI), Department of Microbial Natural Products, Saarland University, Campus E8 1, 66123 Saarbrücken, Germany
2. Department of Pharmacy, Saarland University, Campus E8 1, 66123 Saarbrücken, Germany
3. German Center for Infection Research (DZIF), Partner Site Hannover-Braunschweig, 38124 Braunschweig, Germany
4. Helmholtz International Laboratories, Department of Microbial Natural Products, Saarland University, Campus E8 1, 66123 Saarbrücken, Germany
5. Department of Chemistry, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon