Phytochemical Profiling and Antifungal Activity of Mullein (Verbascum thapsus) Tissue Oils

Mullein (Verbascum thapsus) is a medicinal plant known for its traditional uses and health benefits; however, the composition and bioactivity of its tissue oils from the leaf, stem, and root are underexplored. This study investigated the phytoconstituents, fatty acid profiles, and antifungal activities of mullein oils. Oil was extracted, and samples were analyzed for refractive index, total phenolic content, and antioxidant activity (DPPH). Volatile organic compounds and nontargeted metabolites were identified via GC-MS and UHPLC-QToF-IMS, while FTIR characterized functional groups and NMR quantified fatty acids. Leaf tissue yielded higher oil content and superior antioxidant activity, with distinct fatty acid profiles, including 9,12,15-octadecatrienoic acid. UHPLC-QToF-IMS revealed metabolite profiles, with leaf rich in amino acids and lipids, and root in sugars. Pathway analysis highlighted purine metabolism and terpenoid-quinone biosynthesis as the primary pathways based on the metabolites present in the oils. Notably, root oil exhibited the strongest antifungal activity (MIC 31.2-62.5 µg/mL) against Candida species. This comprehensive characterization identified the leaf oil and stem oil as the most promising for health applications and antifungal properties, respectively. Future work should prioritize isolating active compounds, validating medicinal properties in vivo, and exploring sustainable extraction methods to unlock their full therapeutic and commercial potential.