Isolation and structure elucidation of bioactive secondary metabolites from microbial sources

Microbial organisms often produce biologically active and chemically intriguing secondary metabolites. To isolate and characterize compounds of novel activity and structure, bioassay-guided fractionations were employed on a variety of natural products sources. Active compounds were characterized by spectroscopic analysis and X-ray diffraction methods.;As a result of these studies, six projects were completed, resulting in the purification of a diverse range of compounds containing activity in a variety of assays. A coumarin and parahydroxyphenylethanol were determined to possess phytotoxic activity from fungal pathogens. Two novel C-glycosidic compounds from a bacterial plant pathogen were found to be the first low molecular weight elicitors of the hypersensitive response in plants. A verticillin of the epi-polythiodiketopiperazine class isolated from a soil fungus was discovered to be responsible for inhibition of ras farnesylation transferase. Leafcutter ants were found to be deterred by the presence of a novel sesquiterpenoid in epiphylls. Finally, inhibitors of the PDGF receptor were isolated and characterized from a lichen.;All of the compounds have potential uses as herbicides or pharmaceutical leads, but they also exemplify the information that can be gained through understanding the interactions of natural products with receptors in biological systems.