1. Department of Entomology and Nematology and UC Davis Comprehensive Cancer Center, University of California Davis, One Shields Avenue, Davis, California 95616, United States
2. Department of Pharmacology, University of California Davis, One Shields Avenue, Davis, California 95616, United States
3. VA Northern California Health Care System, Mather, California 95655, United States
4. Institute of Pharmaceutical Chemistry, Goethe-University Frankfurt, Max-von-Laue-Strasse 9, D-60438 Frankfurt am Main, Germany