1. Natural Products Center, School of Natural Resources and the Environment, College of Agriculture and Life Sciences, University of Arizona, 250 E. Valencia Road, Tucson, Arizona 85706, United States
2. Basic Research Program, Leidos Biomedical Research Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland 21702, United States
3. Cancer and Inflammation Program, National Cancer Institute-Frederick, Frederick, Maryland 21702, United States