New tetrahydroanthraquinones and γ-butenolides from the fungus Auxarthron umbrinum DSM3193

Nine novel compounds, comprising seven tetrahydroanthraquinones (auxarthrolones A−G, 1−7), a γ-butenolide glycoside (malfilamentoside E, 26), and a γ-butenolide (auxarthrolide A, 27), together with eighteen known compounds (8−25) were isolated from rice-based solid culture of Auxarthron umbrinum (A. umbrinum) DSM3193 using the one strain many compounds (OSMAC) approach. The structural elucidation of these compounds was accomplished through nuclear magnetic resonance (NMR), mass spectrometry (MS), and NMR calculation combined with DP4+ analysis or MAEΔΔδ parameter, while the absolute configurations of new compounds were established through single-crystal X-ray diffraction, electronic circular dichroism (ECD) spectroscopic data analysis and/or chemical derivatization. Austrocortilutein (10) and auxarthrol H (14) demonstrated moderate cytotoxicity against U87 and U251 [half maximal inhibitory concentration (IC₅₀) 3.5−12.1 μmol·L⁻¹]. Additionally, auxarthrolone A (1), auxarthrol H (14), eupolyphagin B (15), and 7-hydroxy-2-(2-hydroxypropyl)-5-methylchromone (17) exhibited torsional effects on fibroblast proliferation challenges induced by oleic acid, thus demonstrating fibroblast proliferation-promoting activity.