UHPLC-HRMS-Based Untargeted Lipidomics Reveal Mechanism of Antifungal Activity of Carvacrol against Aspergillus flavus

Aspergillus flavusis a common contaminant in grain, oil and their products. Its metabolite aflatoxin B1(AFB1) has been proved to be highly carcinogenic. Therefore, it is of great importance to find possible antifungal substances to inhibit the growth and toxin production ofAspergillus flavus. Carvacrol (CV) was reported as a potent antifungal monoterpene derived from plants. In this paper, the antifungal effects and mechanism of CV onAspergillus flavuswere investigated. CV was shown good inhibition on the growth ofAspergillus flavusand the production of AFB1. CV used in concentrations ranging from 0, 50, 100 and 200 μg/mL inhibited the germination of spores, mycelia growth and AFB1production dose-dependently. To explore the antifungal mechanism of CV onAspergillus flavus, we also detected the ergosterol content ofAspergillus flavusmycelia, employed Scanning Electron Microscopy (SEM) to observe mycelia morphology and utilized Ultra-High-Performance Liquid Chromatography-High-Resolution Mass Spectrometry (UHPLC-HRMS) to explore the lipidome profiles ofAspergillus flavus. The results showed that the production of ergosterol of mycelia was reduced as the CV treatment concentration increased. SEM photographs demonstrated a rough surface and a reduction in the thickness of hyphae inAspergillus flavustreated with CV (200 µg/mL). In positive ion mode, 21 lipids ofAspergillus flavusmycelium were downregulated, and 11 lipids were upregulated after treatment with 200-µg/mL CV. In negative ion mode, nine lipids ofAspergillus flavusmycelium were downregulated, and seven lipids upregulated after treatment with 200-µg/mL CV. In addition, the analysis of different lipid metabolic pathways between the control and 200-µg/mL CV-treated groups demonstrated that glycerophospholipid metabolism was the most enriched pathway related to CV treatment.Keywords:Aspergillus flavus;carvacrol;untargeted lipidomics;ultra-high-performance liquid chromatography-high-resolution mass spectrometry (UHPLC-HRMS);antifungal activity