BIOLOGICAL-ACTIVITY OF A HEPTAKETIDE METABOLITE FROM PLEIOCHAETA-SETOSA

An uncommon heptaketide metabolite, setosol (2,8-dimethyl-4 methoxy-6, 10,11-trihydroxy-benzooxaonin), was isolated from a liquid culture fil trate of the fungus Pleiochaeta setosa. The biological activity of the molecule was studied by using 12 microbial strains consisting of thre e bacteria, three yeasts and six fungi. The level of activity was comp ared with those of known antibiotics and antifungal agents. The metabo lite exhibited antifungal and antibiotic activity against Drechslera o ryzae, Gerlachia oryzae, Pyricularia oryzae, Cryptococcus neoformans, and Staphylococcus aureus. The acetylated derivative of setosol did no t inhibit the growth of any of the target pathogens. Phytotoxicity stu dies on whole lupine leaves show that setosol is implicated in the pat hogenesis of the brown spot disease of lupines since artificial inocul ation of the leaves with the metabolite provoked lesions similar to th e characteristic brown spots and lesions on lupine leaves infected by the fungus.