1. Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev str., bl.9, 1113 Sofia, Bulgaria
2. Institute of Chemistry, Faculty of Science, P. O. Box 162, 1001 Skopje, R. Macedonia
3. Department of Food Science and Technology, CEBAS (CSIC), P.O. Box 164, Espinardo (Murcia) 30100, Spain
4. Institute of Botany, Bulgarian Academy of Sciences, Sofia, Bulgaria