1. Department of Anatomy, Histology and Embryology, Medical Faculty, Medical University-Plovdiv, 4000 Plovdiv, Bulgaria
2. Department of Medical Physics and Biophysics, Faculty of Pharmacy, Medical University-Plovdiv, 4000 Plovdiv, Bulgaria
3. Laboratory of Biologically Active Substances, Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, 139 Ruski Blvd., 4000 Plovdiv, Bulgaria