1. Institute for Pharmaceutical Biology, University of Bonn, Nussallee 6, D-53115 Bonn, Germany
2. Current address: Pharmacognosy Department, Faculty of Pharmacy, Minia University, 61519 Minia, Egypt
3. Current address: Kekulé Institute of Organic Chemistry and Biochemistry, University of Bonn, Gerhard-Domagk-Straße 1, D-53121 Bonn, Germany
4. College of Pharmacy, University of Hawaii at Hilo, 34 Rainbow Drive, Hilo 96720, Hawaii, USA. Fax: +1 80 89 33 29 74