Stephan Seip

Concentricol, a taxonomically significant triterpenoid from Daldinia concentrica

In the course of a chemotaxonomic study of xylariaceous Ascomycetes, a major metabolite was isolated and identified from the ascostromata of Daldinia concentrica. The compound, for which the name concentricol is proposed, constitutes a highly oxidised squalene derivative. A survey of several Daldinia spp. from around the world (including several type materials), employing analytical HPLC-UV/Vis (with diode array detection) and positive electrospray HPLC-MS of stromatal MeOH extracts revealed that concentricol was omnipresent in the stromata of D. concentrica, as well as in those of several collections of the pantropical Daldinia eschscholzii. All other investigated Daldinia spp. were found devoid of concentricol but contained binaphthalenes, benzophenones and/or azaphilones as further taxonomically relevant main metabolites.

Macrocarpones, novel metabolites from stromata of Hypoxylon macrocarpum, and new evidence on the chemotaxonomy of Hypoxylon species

Several species of the genus Hypoxylon (Xylariaceae) were studied for morphological characters and HPLC-based secondary metabolite profiles. It was confirmed that Hypoxylon is divided into two groups of species, containing either Mitorubrin type azaphilones or binaphthyls, respectively, as main metabolites. In Hypoxylon species of the latter group, some metabolites that are known from the allied genus Daldinia (i.e., Daldinal A in H. fuscum and Daldinin C in H. fuscopurpureum), were encountered for the first time. Moreover, three novel aromatic polyketides, for which the trivial names Macrocarpones A, B and C are proposed, were isolated from ascostromata of Hypoxylon macrocarpum and identified by high resolution mass spectrometry and 2D-NMR spectroscopy. Orsellinic Acid was also identified from ascostromata of H. howeianum and detected by HPLC-MS and HPLC-UV/Vis fingerprinting methodology in H. fragiforme and H. rubiginosum, but not in other examined Hypoxylon species. Due to these studies, H. fuscopurpureum sensu Y.-M. Ju & J.D. Rogers 1996 was identified as a new record for Germany.