Antifungal effects of trans-anethole, the main constituent of Illicium verum fruit volatiles, on Aspergillus flavus in stored wheat

Natural gaseous fungicides have great application potential for controlling the fungal decay of postharvest agroproducts. In fact, the fruit of Illicium verum has traditionally been buried in household grain piles to prevent fungal infection in China. However, the antifungal effects of the I. verum fruit against fungi in storage grains remain unclear. In this study, the volatile compounds from I. verum fruit were analyzed, and trans-anethole was found to be the main constituent, accounting for 87.9%. The antifungal potency of trans-anethole on the fungus Aspergillus flavus was then tested. Trans-anethole completely inhibited the growth of A. flavus at concentrations of 0.286 and 0.4 μL/mL in the vapor and liquid phases, respectively. Fumigation with 0.8 μL/mL trans-anethole prevented A. flavus proliferation in wheat grains with 20% moisture content. Further biochemical and transcriptomic analyses revealed the inhibitory effect of trans-anethole on A. flavus spores. Using scanning electron microscopy, we observed that trans-anethole could affect spore morphology in a dose-dependent manner. Transcriptomic analyses showed that 8722 genes, mainly those related to oxidative phosphorylation, citric acid cycle, mitogen-activated protein kinase signaling, ABC transport, and autophagy, were significantly differentially expressed in A. flavus spores exposed to trans-anethole. Trans-anethole treatment also increased mitochondrial membrane potential and induced intracellular accumulation of reactive oxygen species and DNA damage in A. flavus spores. This study provides new insights into the antifungal effect of trans-anethole on A. flavus in postharvest grains and promotes the use of natural volatile compounds in protecting agroproducts from fungal decay.