1. Natural Products Utilization Research Unit, Agricultural Research Service, U.S. Department of Agriculture, P.O. Box 8048, University, Mississippi 38677; Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy (m/c 877), University of Illinois at Chicago, 833 South Wood Street, Chicago, Illinois 60612; IQUIMEFA-CONICET, School of Pharmacy and Biochemistry, University of Buenos Aires, Junín 956, Buenos Aires, Argentina; and Department of Surgical Oncology, College of Medicine, University...