1. Department of Natural Drugs and Department of Chemical Drugs, University of Veterinary and Pharmaceutical Sciences Brno, Palackého 1-3, CZ-612 42 Brno, Czech Republic, National Center for Biomolecular Research, Faculty of Science, Masaryk University, Kamenice 5/A4, CZ-625 00 Brno, Czech Republic, and Mass Spectrometry Research Unit, Department of Chemistry, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium