1. Department of Ecology and Evolutionary Biology, Tulane University, 6823 St. Charles Avenue, New Orleans, Louisiana 70118, Division of Pharmacognosy, Department of Medicinal Chemistry, Uppsala University, Biomedical Center, Box 574, 751 23 Uppsala, Sweden, and Department of Pharmacology, School of Medicine, Tulane University, 1430 Tulane Avenue, New Orleans, Louisiana 70112