1. Department of Chemistry of Natural Compounds, University of Chemistry and Technology in Prague, Technická 5, CZ-16028 Prague 6, Czech Republic
2. Institute of Experimental Botany AS CR, Isotope Laboratory, Vídeňská 1083, CZ-14220 Prague 4, Czech Republic
3. Faculty of Engineering and Natural Sciences, Tampere University, FI-33101 Tampere, Finland