Natural food flavour (E)-2-hexenal, a potential antifungal agent, induces mitochondria-mediated apoptosis in Aspergillus flavus conidia via a ROS-dependent pathway

Authors: MA, WEIBIN - Henan University Of Technology; ZHAO, LULING - Henan University Of Technology; Johnson, Eric; XIE, YANLI - Henan University Of Technology; ZHANG, MINGMING - Henan University Of Technology

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2022
Publication Date: 3/15/2022
Citation: Ma, W., Zhao, L., Johnson, E.T., Xie, Y., Zhang, M. 2022. Natural food flavour (E)-2-hexenal, a potential antifungal agent, induces mitochondria-mediated apoptosis in Aspergillus flavus conidia via a ROS-dependent pathway. International Journal of Food Microbiology. 370. Article 109633. https://doi.org/10.1016/j.ijfoodmicro.2022.109633.
DOI: https://doi.org/10.1016/j.ijfoodmicro.2022.109633

Interpretive Summary: Agricultural commodities can become contaminated with fungi at harvest. These fungi can proliferate during post-harvest storage and inflict damage to the commodity. In addition, some contaminating fungi synthesize mycotoxins which are harmful for livestock and humans. It is important to identify bioactive molecules that can reduce post-harvest contamination of commodities that are safe and effective. A volatile molecule produced by plants causes fungal spores to die at a specific concentration. A number of experiments were completed that suggested that the mitochondria inside the spores, which produce energy for the spores, became dysfunctional after six hours of treatment with the volatile molecule. Reactive oxygen species in the fungal spores also increased after six hours of exposure with the volatile molecule; these reactive oxygen species can readily damage membranes and other molecules in the spores, and ultimately trigger the spore to commit itself to programmed cell death. This study indicated that the volatile molecule causes significant damage to important structures in the fungal spores. The volatile chemical is used in the food industry, and generally recognized as safe. This research is an important demonstration that a safe, volatile chemical can be used to control fungal contamination of food during storage.

Technical Abstract: Natural food flavour (E)-2-hexenal, a green leaf volatile, exhibits potent antifungal activity on Aspergillus flavus, but its antifungal mechanism has not been fully elucidated. In this study, we evaluated (E)-2-hexenal-induced apoptosis in A. flavus conidia and explored the underlying mechanisms of action. Evidence of apoptosis in A. flavus conidia were investigated by methods including fluorescent staining, flow cytometry, confocal laser scanning microscope, and spectral analysis. Results indicated that 4.0 µL/mL (minimum fungicidal concentration, MFC) of (E)-2-hexenal application induced early markers of apoptotic cell death in A. flavus conidia with a rate of 38.4% after 6 h exposure. Meanwhile, typical hallmarks of apoptosis, such as decreased mitochondrial membrane potential (MMP), activated metacaspase activity, fragmented DNA, mitochondrial permeability transition pore (MPTP) opening and cytochrome c (Cyt C) release from mitochondria to the cytosol were also confirmed. Furthermore, intracellular ATP levels were reduced by 63.3 ± 3.6% and reactive oxygen species (ROS) positive cells increased by 31.1 ± 3.1% during A. flavus apoptosis induced by (E)-2-hexenal. L-Cysteine (Cys), an antioxidant, could strongly block the excess ROS generation caused by (E)-2-hexenal, which correspondingly resulted in a significant inhibition of MPTP opening and decrease of apoptosis in A. flavus, indicating that ROS palys a pivotal role in (E)-2-hexenal-induced apoptosis. These results suggest that (E)-2-hexenal exerts its antifungal effect on A. flavus conidia via a ROS-dependent mitochondrial apoptotic pathway.