Bioassay-directed Discovery of Natural Product Leads. Antibacterials and Antifungals From Unusual Sources

Use of bioassay-directed screening and isolation techniques has led to the discovery of the dactylocyclines, novel tetracycline glycosides from a Dactylosporangium sp. The dactylocyclines have activity against tetracycline-resistant bacteria. Analogous techniques have led to the characterization of iporizabin/scammonin I, a complex glycolipid active against methacillin-resistant staphylococci, from the classical medicinal plant Ipomoea orizabensis. Using a testing sequence involving, i. a. , fungal 1,3-β-glucan synthase, a series of known neolignans were isolated from tropical Krameria ixina and K. triandra and were shown to have potentially useful anticandidal and antifungal activity.