Coprinolide, a novel antifungal tricyclic polyketide with a rare furanone-fused chromene skeleton isolated from the mushroom <i>Coprinus comatus</i>

A search for antifungal compounds from the mushroom Coprinus comatus using a bioassay-guided chromatographic fractionation approach led to the discovery of a novel polyketide harboring a rare 3,3a,9,9a-tetrahydro-1H-furo[3,4-b]chromen-1-one skeleton. The novel compound was named coprinolide. The inhibitory activity and fungicidal potential of coprinolide were evaluated against five economically important plant-pathogenic fungi. Coprinolide showed inhibitory effects on conidial germination and germ tube elongation of all tested fungi. The strongest effect was observed for Colletotrichum orbiculare with half-maximal inhibitory concentrations of 7.1 ppm and 8.2 ppm for conidial germination and germ tube elongation, respectively. Furthermore, coprinolide exhibited fungicidal activity against the tested fungi by inhibiting conidial germination to conidial death as confirmed by fluorescence microscopy using fluorescein diacetate and propidium iodide. These findings showed the potential of the mushroom as a source of a novel bioactive compound with promising agricultural application as an antifungal agent against different plant-pathogenic fungi.