1. Southwest Center for Natural Products Research and Commercialization, Office of Arid Lands Studies, College of Agriculture and Life Sciences, University of Arizona, 250 E. Valencia Road, Tucson, Arizona 85706-6800, Departments of Surgery and Pediatrics, Arizona Health Sciences Center, University of Arizona, Tucson, Arizona 85724, and Department of Phytochemistry, China Pharmaceutical University, Nanjing 10003, People's Republic of China