OSMAC strategy and LC–MS profiling reveal metabolic diversity and bioactivities of Xylaria thienhirunae SWUF17-44.1

Xylariaceous fungi represent a promising source of secondary metabolites with diverse biological functions. However, their metabolic capacity often remains underestimated under conventional cultivation. The One Strain–Many Compounds (OSMAC) strategy enhances metabolite diversity by altering culture conditions. This study investigated the metabolic potential and bioactivities of Xylaria thienhirunae SWUF17-44.1 using the OSMAC approach. The strain was cultured under four conditions: Czapek yeast extract agar (CYA), Modified Norkrans’s C (MNC), potato dextrose broth (PDB), and soluble malt yeast extract agar (SMYA). Extracts were evaluated for antimicrobial activity against bacteria and fungi, antioxidant capacity by DPPH radical scavenging and total phenolic content (TPC), and anti-inflammatory activity via nitric oxide inhibition. Metabolite profiling was performed by thin-layer chromatography and liquid chromatography–mass spectrometry (LC–MS). Culture media markedly influenced growth, metabolite yield, and bioactivity. Crude extracts displayed broad-spectrum antimicrobial properties, with stronger activity against Gram-positive bacteria. Antioxidant activity was higher in PDB, whereas TPC was higher in the nutrient-deficient media (CYA and SMYA). This indicates that compounds contributing to TPC do not necessarily drive antioxidant activity. The anti-inflammatory activity was highest in SMYA extracts. LC–MS analysis revealed common and unique metabolites across media, including alkaloids, aminoglycosides, fatty acid derivatives, and phenolics. Identified compounds included p-acetamidophenol, di-homo-γ-linolenoyl-EA, kolanone, and netilmicin. Several unassigned peaks indicated the presence of potentially novel metabolites. The OSMAC strategy successfully enhanced the metabolic diversity of X. thienhirunae SWUF17-44.1, leading to extracts with antimicrobial, antioxidant, and anti-inflammatory properties. These findings highlight the strain as a promising source of bioactive compounds and underscore the utility of OSMAC in fungal natural product discovery.