Studies on the secondary metabolism of Rosellinia and Dematophora strains (Xylariaceae) from Iran

The xylariaceous genus Dematophora has recently been resurrected and segregated from Rosellinia based on a molecular
phylogeny and morphological characters. This was an important taxonomic change because Dematophora in the current sense
contains several important pathogens, while Rosellinia is limited to mainly saprotrophic species that have an endophytic stage in
their life cycle and may even have beneficial effects on the host plants. During our ongoing work on the functional biodiversity of
the Xylariales, we have encountered new strains of rosellinoid Xylariaceae from Iran and have studied their mycelial cultures for
secondary metabolites in an attempt to establish further chemotaxonomic affinities. In the process, we isolated and identified 13
compounds, of which rosellisteroid (1), the cichorine derivative 2, and the alkaloid 3 are new. Out of these, nine were tested for
their antimicrobial affinities with cytochalasin E (6) exhibiting weak activity against Schizosaccharomyces pombe. The cytotoxicity
of three cytochalasin derivatives was examined and their effects on the F-actin cytoskeletal organization studied by
fluorescence microscopy using fluorescent phalloidin. Cytochalasin E (6) and Δ6,12-cytochalasin E (7) showed strong and
irreversible action on actin, while cytochalasin K (8) exhibited weaker, reversible effects.