1. Division of Pharmacognosy, Section Metabolomics, Institute of Biology, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Division of Plant Cell Physiology, Institute of Biology, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Division of NMR, Institute of Chemistry, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden, The Netherlands, and Laboratoire de Pharmacognosie, FRE CNRS 2715, IFR 53 Biomolecules, CPCBAI, B.P. 1039, Moulin de la Housse, 51687 Reims Cedex, France