Linalool, the main volatile constituent from Zanthoxylum schinifolium pericarp, prevents growth of Aspergillus flavus in post-harvest grains

Abstract

Plant volatile organic compounds (PVOCs) have shown great potential as alternatives to synthetic insecticides or fungicides for stored grain management. Zanthoxylum schinifolium pericarp, a traditional Chinese spice, is conventionally buried in grain piles to prevent fungal spoilage of stored grains in China. However, the chemical basis and antifungal mechanism of PVOCs from Z. schinifolium pericarp by which they inhibit spoilage remain unclear. In this study, the effectiveness of PVOCs from Z. schinifolium pericarp against Aspergillus flavus growth in high-moisture wheat grains was studied under simulated storage conditions. The growth of A. flavus in the grains was inhibited in a dose-dependent manner. The chemical composition of PVOCs from Z. schinifolium pericarp was determined using gas chromatography-mass spectrometry; linalool (50.31%) and d-limonene (20.92%) were the two main components. An antifungal experiment showed that 0.571 and 1.2 μL/mL concentrations of linalool completely inhibited A. flavus growth upon vapor and liquid contact, respectively. d-limonene showed much lower antifungal activity, indicating that linalool is responsible for the antifungal activity of PVOCs from Z. schinifolium pericarp. Linalool treatment disrupted the cell membrane of A. flavus, resulting in increased electrolyte leakage and A260nm in the culture supernatant. After 6 h of exposure to 1.2 μL/mL linalool, metabolomic analysis revealed 90 differentially expressed metabolites in A. flavus mycelia, including 69 upregulated and 21 downregulated metabolites. It was speculated that linalool inhibited A. flavus by disrupting the permeability and integrity of cell membranes, tricarboxylic acid cycle, and ATP binding cassette transport and by inducing mitochondrial dysfunction and oxidative stress. This study shows the potential of PVOCs from Z. schinifolium pericarp as biofumigants for stored grain management and provides a new perspective on their antifungal mechanism against A. flavus growth.