1. Laboratory of Pharmacognosy, Institute of Pharmacy, University of Liège, CHU, Tour 4, Avenue de l'Hôpital 1, B-4000 Liège, Belgium, Laboratory of Medical Microbiology, University of Liège, CHU, Tour 3, Avenue de l'Hôpital 1, B 4000 Liège, Belgium, and Laboratory of NMR, Institute of Physics, Sart Tilman, B 4000 Liège, Belgium