| Summary: | A fungal endophyte originating from the Canary Islands was identified as a potent antagonist against the fungal phytopathogen <i>Hymenoscyphus fraxineus</i>, which causes the devastating ash dieback disease. This endophyte was tentatively identified as <i>Pezicula</i> cf. <i>ericae</i>, using molecular barcoding. Isolation of secondary metabolites by preparative high-performance liquid chromatography (HPLC) yielded the known compounds CJ-17,572 (<b>1</b>), mycorrhizin A (<b>3</b>) and cryptosporioptides A–C (<b>4</b>–<b>6</b>), besides a new <i>N</i>-acetylated dihydroxyphenylalanin derivative <b>2</b>, named peziculastatin. Planar structures were elucidated by NMR and HRMS data, while the relative stereochemistry of <b>2</b> was assigned by H,H and C,H coupling constants. The assignment of the unknown stereochemistry of CJ-17,572 (<b>1</b>) was hampered by the broadening of NMR signals. Nevertheless, after semisynthetic conversion of <b>1</b> into its methyl derivatives <b>7</b> and <b>8</b>, presumably preventing tautomeric effects, the relative configuration could be assigned, whereas comparison of ECD data to those of related compounds determined the absolute configuration. Metabolites <b>1</b> and <b>3</b> showed significant antifungal effects in vitro against <i>H. fraxineus</i>. Furthermore, <b>4</b>–<b>6</b> exhibited significant dispersive effects on preformed biofilms of <i>S. aureus</i> at concentrations up to 2 µg/mL, while the biofilm formation of <i>C. albicans</i> was also inhibited. Thus, cryptosporioptides might constitute a potential source for the development of novel antibiofilm agents.
|
|---|