[1] Univ Liege, Lab Chem Nat Mol, Gembloux Agro Biotech, B-5030 Gembloux, Belgium
[2] Univ Yaounde I, Fac Sci, Dept Organ Chem, POB 812, Yaounde, Cameroon
[3] Univ Maroua, Higher Teachers Training Coll, Dept Chem, POB 55, Maroua, Cameroon
[4] Univ Liege, Ctr Interdisciplinary Res Med CIRM, Lab Pharmacognosy, B-4000 Liege, Belgium
[5] Univ Tubingen, Inst Trop Med, D-72074 Tubingen, Germany
[6] German Ctr Infect Res, Partner Site Tubingen, D-72074 Tubingen, Germany