1. Department of Plant Science, University of Pretoria, Pretoria, 0002, South Africa, Smithsonian Tropical Research Institute, Ancon Panama, Republic of Panama, Department of Chemistry, University of Pretoria, Pretoria, 0002, South Africa, Chemistry of Medicinal Plants Department, National Research Centre, Dokki, Cairo, Egypt, and Instituto de Química Orgánica, Consejo Superior de Investigaciones Científicas (CSIC), Juan de la Cierva 3, E-28006 Madrid, Spain