Bioactive natural products from mycoparasitic and fungicolous fungi

Mycoparasitism involves a competitive interaction between fungal species that results in one species gaining nutrients directly from another. This process often causes damage to the host. Some fungi that colonize others are more generally categorized as fungicolous fungi, i.e., those for which true mycoparasitism has not been demonstrated. The damage such colonists cause to host fungi is due at least in part to the production of antifungal agents. Thus, mycoparasites may be viewed as logical potential sources of antifungal secondary metabolites.; This thesis describes chemical studies of several colonist species. These studies resulted in the isolation of over twenty known and new natural products. Most of them displayed antifungal activity, and some possess previously undescribed ring structures. Chemical investigations of a Mycelia sterilia resulted in the isolation of three new polyketide-derived tropolones containing a new ring system. A fourth new biogenetically related compound containing a second novel ring system was also isolated. One of these compounds showed potent activity against Aspergillus flavus, three displayed activity against Candida albicans, and all of them were active against Bacillus subtilis and Staphylococcus aureus .; Chemical investigations of Fusarium merismoides, Fusarium oxysporum, and others led to the isolation of a number of other new compounds that represent diverse structural classes, along with some known metabolites. For instance, a new antibacterial dioxomorpholine-containing metabolite related to equisetin was isolated from F. merismoides. An unusual new antimicrobial compound comprised of modified terpenoid and mannitol units joined by an ether linkage was isolated from F. oxysporum . Studies of an unidentified Verticillium sp. afforded two new structurally interesting polyketide-derived natural products with antifungal activity against A. flavus and C. albicans . These two compounds possess an unusual structure incorporating a tetrahydrofurandione ring linked to a furylidene ring.; The structures of all of these compounds were elucidated by extensive analysis of NMR and mass spectral data. In some cases, chemical derivatization or single-crystal X-ray diffraction methods were employed to confirm structures and stereochemistry. Details of the isolation, structure determination, and biological activity of these compounds are presented in this thesis.