Abstract: This study aimed to investigate the antifungal activity and underlying mechanism of perillaldehyde thiosemicarbazone (PAT), a compound synthesized using perillaldehyde as the lead compound, against Penicillium italicum. In vitro experiments showed that PAT exhibited good antifungal activity against P. italicum, with both minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) determined to be 12.5 μg/mL. PAT treatment effectively delayed the progression of postharvest blue mold in citrus fruits in a concentration-dependent manner. PAT exhibited extremely low hemolytic toxicity, and its safety was superior to that of prochloraz at the same concentration. Scanning electron microscopy (SEM) observation revealed that PAT treatment induced substantial deformation and shrinkage of P. italicum mycelia. Physiological assays showed that treatment with PAT at 1/2 MIC and MIC levels disrupted cell membrane integrity, reduced ergosterol content, and induced leakage of extracellular nucleic acids and proteins. Furthermore, PAT treatment induced significant loss of the mitochondrial membrane potential of the mycelia and inhibited adenosine triphosphate (ATP) synthesis, thereby impairing normal energy metabolism. Meanwhile, PAT interfered with respiratory metabolism primarily by inhibiting the tricarboxylic acid cycle (TCA) pathway. Molecular docking and enzyme activity assays revealed that PAT might target and bind to succinate dehydrogenase (SDH) to inhibit its activity. In conclusion, PAT may suppress the growth of P. italicum by interacting with SDH in the TCA, thereby leading to mitochondrial dysfunction, aberrant energy metabolism, and disruption of cell membrane structure.

Key words: perillaldehyde; perillaldehyde thiosemicarbazone; Penicillium italicum; citrus; antifungal mechanism