Demethoxyviridiol

Three furanosteroids were isolated from the ash dieback causing fungus Hymenoscyphus pseudoalbidus along with the known compounds viridiol and demethoxyviridiol. The compounds were characterized by 1D and 2D NMR spectroscopy, LC-HRMS and polarimetry.

A new tetrasubstituted octanoic acid, named hyfraxinic acid (1), was isolated together with known 1-deoxyviridiol (2), viridiol (3), nodulisporiviridin M (4), and demethoxyviridiol (5) from the organic extract ofHymenoscyphus fraxineusresponsible for ash (Fraxinus excelsiorL.) dieback in Europe. Hyfraxinic acid (1) was characterized, using spectroscopic methods, as 2,4-dihydroxy-7-methyl-6-methyleneoctanoic acid. Furthermore, the advanced Mosher method was used to determine the absolute configuration (3R) of 1-deoxyviridiol. Nodulisporiviridin M (4) was isolated for the first time fromH. fraxineus. The phytotoxicity of each compound was tested by a leaf puncture assay onCeltis australisL.,Quercus suberL.,Hedera elixL.,Juglans regiaL., andFraxinus angustifoliaL. leaves. Compounds1,3, and5exhibited remarkable phytotoxicity on all plants tested, inducing necrotic lesions at concentrations of 1.0 and 0.5 mg/mL, while compounds2and4were found to be inactive in this bioassay. These results could contribute to a deeper understanding of the pathogenicity ofH. fraxineus.