1. National Hellenic Research Foundation, Institute of Organic and Pharmaceutical Chemistry, Vas. Constantinou 48, 116 35, Athens, Greece, School of Pharmacy, Department of Pharmacognosy, University of Athens, Panepistimioupoli-Zografou GR-15771 Athens, Greece, School of Pharmacy, Department of Molecular and Cell Biology and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, and Rega Institute for Medical Research, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium