Synthesis of Quaternary Ammonium Derivatives of Eugenol and Their Antifungal Mechanism against Gloeophyllum trabeum Wood-Decaying Fungi

To discover novel preservatives for treating wood-decaying fungi, 48 novel eugenol quaternary ammonium salt derivatives were designed and synthesized. Among them, compounds 3j, 3k, 4j, 4k, 5j, 5k, and 6j showed remarkable antifungal activity against Gloeophyllum trabeum (G. trabeum), affording EC50 values ranging from 2.11–7.50 μg/mL. Notably, 3j demonstrated the most potent activity against G. trabeum (EC50 = 0.14 μg/mL), surpassing the positive control dodecyldimethylbenzylammonium chloride (DDBAC, EC50 = 3.33 μg/mL). Additionally, 3j significantly reduced wood mass loss and decay caused by G. trabeum. Mechanistic studies revealed that 3j disrupted the fungal ultrastructure, increased membrane permeability, and induced cellular leakage. Furthermore, 3j disrupted the antioxidant system and energy metabolism, resulting in the accumulation of reactive oxygen species. The multiomics data revealed the molecular mechanisms by which 3j regulated G. trabeum, including key genes, proteins, metabolites, and pathways. This study elucidates key mechanistic insights into developing a natural-product-derived wood preservative.