1. Faculty of Medicine, Sofia University “St. Kliment Ohridski”, 1 Koziak Street, 1407 Sofia, Bulgaria
2. Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia
3. Faculty of Chemistry and Pharmacy, Sofia University “St. Kliment Ohridski”, 1 James Boucher Boulevard, 1164 Sofia, Bulgaria