1. Department of Chemistry, Faculty of Natural Sciences, Trg D. Obradovica 3, University of Novi Sad, 21000 Novi Sad, Serbia and Montenegro, Department of Pharmacy, Faculty of Medicine, Hajduk Veljkova 3, University of Novi Sad, 21000 Novi Sad, Serbia and Montenegro, and Institute for Biological Research “Sinisa Stankovic” Belgrade, 11000 Belgrade, Serbia and Montenegro