Minutellins E-I and daldinone L, new secondary metabolites from different species of the Hypoxylaceae (Xylariales, Ascomycota)

Fungi of the family Hypoxylaceae (Xylariales, Ascomycota) are ubiquitously distributed and fulfil important ecological roles as saprobes, pathogens, and endophytes. Members of this family tend to store large amounts of secondary metabolites in their carbonaceous stromatal tissue commonly formed on colonised wood. This feature is of both taxonomic and chemical value by serving as chemotaxonomic markers and sources of potential new and bioactive compounds. Despite tremendous progress in the characterisation of Hypoxylaceae both in terms of genomics and secondary metabolomics, many unknown metabolites remain to be identified or elucidated. Here, we report on the polyphasic, i.e. morphological, chemical, and genetical analysis of Hypoxylon and Annulohypoxylon spp. collected from the Iranian shore of the Caspian Sea and a chemotaxonomic study of the constituents of a concurrently studied specimen of A. michelianum. A new daldinone derivative and five new minutellin-type azaphilones from stromatal tissues of A. substygium and H. lateripigmentum, respectively, were identified in the course of this study by high-performance liquid chromatography/mass spectrometry coupling (HPLC-MS) and structurally elucidated by nuclear magnetic resonance (NMR) spectroscopy. We realised that the structure of daldinone A was misassigned and in fact equals daldinone C. Finally yet importantly, the distribution of minutellin-type azaphilones throughout the Hypoxylaceae is discussed.