Metabolomics-Guided Discovery, Isolation, Structure Elucidation, and Bioactivity of Myropeptins C–E from <i>Myrothecium inundatum</i>

The saprotrophic filamentous fungus <i>Myrothecium inundatum</i> represents a chemically underexplored ascomycete with a high number of putative biosynthetic gene clusters in its genome. Here, we present new linear lipopeptides from nongenetic gene activation experiments using nutrient and salt variations. Metabolomics studies revealed four myropeptins, and structural analyses by NMR, HRMS, Marfey's analysis, and ECD assessment for their helical properties established their absolute configuration. A myropeptin biosynthetic gene cluster in the genome was identified. The myropeptins exhibit general nonspecific toxicity against all cancer cell lines in the NCI-60 panel, larval zebrafish with EC₅₀ concentrations of 5-30 μM, and pathogenic bacteria and fungi (MICs of 4-32 μg/mL against multidrug-resistant <i>S. aureus</i> and <i>C. auris</i>). <i>In vitro</i> hemolysis, cell viability, and ionophore assays indicate that the myropeptins target mitochondrial and cellular membranes, inducing cell depolarization and cell death. The toxic activity is modulated by the length of the lipid side chain, which provides valuable insight into their structure-activity relationships.