The cytosporones, new octaketide antibiotics isolated from an endophytic fungus

Organic extracts from cultures of endophytic fungi collected in the Guanaca ste Conservation Area of Costa Rica were screened for antibiotic activity. Two endophytes CR200 (Cytospora sp,) and CR146 (Diaporthe sp,) were found t o have potent antibiotic activity. Bioassay guided fractionation of the ext racts from these fungi led to the identification of cytosporones D and E, a ntibacterial active trihydroxybenzene lactones, and three related but inact ive metabolites, The five new octaketides were characterized using X-ray cr ystallography and NMR.