Antifungal activity and mechanism of grape seed polyphenol-copper complex

In this study, grape seed polyphenol-copper complex (GSPCC) was successfully prepared by complexing grape seed polyphenols (GSP) with divalent copper ions. A systematic investigation was conducted on its antifungal activity and mechanism of action against Gloeophyllum trabeum and Aspergillus niger . The inhibition zone assay showed that the minimum inhibitory concentrations (MIC) of GSPCC against Gloeophyllum trabeum and Aspergillus niger were 0.078 mg/mL and 0.156 mg/mL, respectively, while the minimum fungicidal concentration (MFC) against both fungi were 0.312 mg/mL. Its antifungal activity was superior to that of GSP and copper ions alone. GSPCC increases the permeability of fungal cell membranes, leading to the leakage of intracellular nucleic acids and proteins, while significantly inhibiting the activities of cellulase and hemicellulase. Furthermore, metabolomic analysis indicated that GSPCC interferes with key metabolic pathways of fungi, including amino acid synthesis (especially inhibiting the production of L-arginine and L-glutamate), carbohydrate metabolism (disrupting the tricarboxylic acid cycle and glycolysis process), and lipid metabolism (reducing unsaturated fatty acids and decreasing membrane fluidity). This study confirms that GSPCC is an effective antifungal agent, providing a theoretical foundation for developing novel plant polyphenol-based antifungal agents.