Cohaerins A and B, azaphilones from the fungus Hypoxylon cohaerens, and comparison of HPLC-based metabolite profiles in Hypoxylon sect. Annulata

Azaphilones, cohaerins A and B, were isolated from the fungus Hypoxylon cohaerens. Stromatal metabolite profiles of several taxa of Hypoxylon sect. Annulata were generated using analytical HPLC-MS and studied for their prevailing metabolites and chemotaxonamonal classification. Azaphilones, named cohaerins A and B were isolated from stromata of the xylariaceous ascomycete Hypoxylon cohaerens. Their absolute structures were determined by spectroscopic methods (2D NMR, MS, IR, UV CD), and subsequently confirmed by acetylation. Stromatal metabolite profiles of several taxa of Hypoxylon sect. Annulata were also generated using analytical HPLC with diode array and MS detection. The cohaerins were neither found in other Hypoxylon spp., nor in other Xylariaceae. However, they were present even in holotype material of H. cohaerens, collected over 200 years ago. The binaphthalene BNT was also omnipresent in sect Annulata, and its derivatives, the benzo[ j]fluoranthenes daldinone A and truncatone, as well as presumably related compounds. These fungi were found devoid of other types of azaphilone pigments of the Xylariaceae, such as mitorubrins and daldinins, the latter of which are widespread in certain groups of Hypoxylon sect. Hypoxylon. Hence, chemotaxonomic data largely support the current generic concept. The original source of truncatone was identified as Hypoxylon annulatum.