Corresponding Author Daniela Pechlivanova Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria Faculty of Medicine, Sofia University “St. Kliment Ohridski”, Sofia, Bulgaria Correspondence Petar Todorov, Department of Organic Chemistry, University of Chemical Technology and Metallurgy, 1756 Sofia, Bulgaria. Email: pepi_37@abv.bg Daniela Pechlivanova, Institute of Neurobiology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.