1. Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Yamashiro-cho, Tokushima 770-8514, Japan, Bayer AG, Pharma Research, Life Science Center Natural Products, P.O.B. 101709, D-42096 Wuppertal, Germany, and Mainz University, Angewandte Toxikologie, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany