Isolation of Chromanone and Isobenzofuran Derivatives from a Fungicolous Isolate of Epicoccum purpurascens

Abstract

Mycoparasitic and fungicolous fungi are those which attack and colonize other fungal species, and often cause damage to the host fungi. In many cases, at least part of this damage appears to be caused by antifungal metabolites. In spite of such observations, these commonly occurring fungi remain relatively unexplored from a chemical standpoint. As a part of our ongoing studies of mycoparasitic and fungicolous fungi as sources of new antifungal metabolites, a fungicolous isolate of Epicoccum purpurascens (MYC 1097 = NRRL 37031) was selected for investigation. Epicoccum purpurascens Ehrenb. Ex Schlecht (syn. E. nigrum Link) has been recorded as a colonist of decaying basidiocarps of larger fungi and has been studied as an antagonist that produces antibiotics and/or parasitizes the mycelium of fungal pathogens of crop plants. Studies of an organic extract from cultures of E. purpurascens MYC 1097 afforded two new metabolites: 7-methoxy-4-oxo-chroman-5carboxylic acid methyl ester (1) and 1,3-dihydro-5-methoxy7-methylisobenzofuran (2). The known compounds 4,5,6trihydroxy-7-methyl-3H-isobenzofuran-1-one (3) and 1,3dihydro-4,6-dihydroxy-7-methylisobenzofuran (4) were also obtained. Details of these studies are presented here. The EtOAc extract of solid-substrate fermentation cultures of E. purpurascens was fractionated by Sephadex LH-20 column chromatography. Chromanone metabolite 1 was obtained from the least polar fraction by subsequent silica gel column chromatography. HPLC separation of more polar fractions led to the isolation of the isobenzofuran derivatives 2-4.