Resolution of the <i>Hypoxylon fuscum</i> Complex (Hypoxylaceae, Xylariales) and Discovery and Biological Characterization of Two of Its Prominent Secondary Metabolites
Christopher Lambert | Mohammad Javad Pourmoghaddam | Marjorie Cedeño-Sanchez | Frank Surup | Seyed Akbar Khodaparast | Irmgard Krisai-Greilhuber | Hermann Voglmayr | Theresia E. B. Stradal | Marc Stadler
<i>Hypoxylon,</i> a large, cosmopolitan genus of Ascomycota is in the focus of our current poly-thetic taxonomic studies, and served as an excellent source for bioactive secondary metabolites at the same time. The present work concerns a survey of the <i>Hypoxylon fuscum</i> species complex based on specimens from Iran and Europe by morphological studies and high performance liquid chromatography coupled to mass spectrometry and diode array detection (HPLC-MS-DAD). Apart from known chemotaxonomic markers like binaphthalene tetrol (BNT) and daldinin F, two unprece-dented molecules were detected and subsequently isolated to purity by semi preparative HPLC. Their structures were established by nuclear-magnetic resonance (NMR) spectroscopy as 3′-malonyl-daldinin F (<b>6</b>) and pseudofuscochalasin A (<b>4</b>). The new daldinin derivative <b>6</b> showed weak cytotoxicity towards mammalian cells but bactericidal activity. The new cytochalasin <b>4</b> was compared to cytochalasin C in an actin disruption assay using fluorescence microscopy of human osteo-sarcoma U2OS cells, revealing comparable activity towards F-actin but being irreversible compared to cytochalasin C. Concurrently, a multilocus molecular phylogeny based on ribosomal and proteinogenic nucleotide sequences of <i>Hypoxylon</i> species resulted in a well-supported clade for <i>H. fuscum</i> and its allies. From a comparison of morphological, chemotaxonomic and phylogenetic evidence, we introduce the new species <i>H. eurasiaticum</i> and <i>H. pseudofuscum</i>.
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