Bioactive eremophilane meroterpenoids produced by the soil fungus Stchigelomyces brunnescens gen. et comb. nov

The emergence of antimicrobial resistance has created an urgent demand for novel antibiotics. Fungi in the order Sordariales represent a rich source of chemically diverse and bioactive secondary metabolites. However, many taxa within this order remain insufficiently explored. During our ongoing search for novel taxa and bioactive compounds, we isolated a soil-borne fungus initially identified as Cladorrhinum brunnescens. The multigene phylogenetic inference using four DNA loci (ITS, LSU, rpb2, and tub2) revealed that this species represents a distinct lineage within the family Podosporaceae, herein transferred to the new genus Stchigelomyces. Investigation of its secondary metabolites led to the discovery of four novel eremophilane meroterpenoids (1–4) and two previously undescribed salicyloid derivatives (6–7), together with a known triene fatty acid (5). The structures of all compounds were elucidated by comprehensive spectroscopic analyses, and their antimicrobial properties were assessed. Among the tested compounds, stchigelomycin C (3) exhibited strong inhibitory effects against some Gram-positive bacteria, yeast, and filamentous fungi, particularly Bacillus subtilis and Mucor hiemalis, at a concentration of 8.3 μg/mL. These findings further demonstrate the potential of taxa belonging to the Sordariales as promising sources for the discovery of new bioactive compounds.