Study on the antifungal activity and mechanism of tea saponin from Camellia oleifera cake

The purpose of this study was to isolate tea saponin from defatted C. oleifera cake and explore its potential antifungal activity and mechanism. UHPLC–MS/MS identified the compounds, and the antibacterial activity of tea saponin was determined by the inhibition zone method and double dilution method. In addition, the influence of tea saponin on the cell membrane, hyphae, and biofilm was studied to explore the antifungal mechanism of tea saponin. The results showed that the purity of tea saponin was 90.61%, and the main components of C. oleifera saponins were oleiferasaponin D3. Tea saponin has an apparent inhibitory effect on fungus. The minimum inhibitory concentrations (MIC) of the tea saponin against C. albicans, S. cerevisiae, and Penicillium were 0.078, 0.156, and 0.156 mg/mL, while the minimum fungicidal concentrations (MFC) were 0.312, 0.625, and 0.625 mg/mL, respectively. Tea saponin could destroy the cell membrane structure, which led to the leakage of cell contents and inhibited the growth of mycelium, reduced cell adhesion and aggregation, and effectively inhibited the formation of biofilm of C. albicans. Transcriptomic analyses indicated that tea saponin could down-regulate the expression of several hyphae- and biofilm-related genes (ALS3, ECE1, HWP1, EFG1, and UME6). This study confirmed that tea saponin from C. oleifera cake can be used as an effective source of natural antifungal agents and provide guidance on their utilization in the field of food safety.