Interference Competition among Coprophilous Fungi: Production of (+)-Isoepoxydon by Poronia punctata.

(+)-Isoepoxydon has been established as the major causative agent of interference competition between Poronia punctata (NRRL 6457), a late fungal colonist of cattle dung, and two early-occurring dung colonists, Ascobolus furfuraceus (NRRL 6460) and Sordaria fimicola (NRRL 6459). This compound was isolated from ethyl acetate extracts of liquid cultures of P. punctata by silica gel chromatography and identified by mass spectrometry and proton and carbon nuclear magnetic resonance spectroscopy. The isolation process was guided by in vitro bioassays for antifungal activity against A. furfuraceus and S. fimicola. (+)-Isoepoxydon has been implicated as an intermediate in the biosynthesis of patulin, a mycotoxin produced by Penicillium spp., but no patulin could be detected in cultures of P. punctata.