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

Chenling Qu,Zhuozhen Li,Xiupin Wang

doi:10.3390/foods11010093

Abstract

Aspergillus flavus is 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 of Aspergillus flavus. Carvacrol (CV) was reported as a potent antifungal monoterpene derived from plants. In this paper, the antifungal effects and mechanism of CV on Aspergillus flavus were investigated. CV was shown good inhibition on the growth of Aspergillus flavus and 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 AFB1 production dose-dependently. To explore the antifungal mechanism of CV on Aspergillus flavus, we also detected the ergosterol content of Aspergillus flavus mycelia, 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 of Aspergillus 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 in Aspergillus flavus treated with CV (200 µg/mL). In positive ion mode, 21 lipids of Aspergillus flavus mycelium were downregulated, and 11 lipids were upregulated after treatment with 200-µg/mL CV. In negative ion mode, nine lipids of Aspergillus flavus mycelium 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.

Highlights

As a pathogenic fungus, Aspergillus flavus Link (A. flavus) frequently contaminates grains, oil and nuts, resulting in a significant reduction of nutritional quality and a serious loss of food commodities [1,2]
Similar results for the antifungal effect of CV were found in Fusarium oxysporum, Neocosmospora solani and Microdochium nivale, and CV at a 0.2–0.4-mg/mL concentration inhibited the spore germination in a dose-dependent manner [37]
CV made the mycelia of A. flavus shrink and form a rough surface

Summary

Introduction

Aspergillus flavus Link (A. flavus) frequently contaminates grains, oil and nuts, resulting in a significant reduction of nutritional quality and a serious loss of food commodities [1,2]. Since A. flavus could produce hazardous secondary metabolite aflatoxins (AFTs), it causes contamination of food commodities during storage and processing and endangers human health [3]. Using synthetic preservatives and fungicides was an effective way to inhibit the growth of A. flavus and the production of AFTs. the application of synthetic antifungal agents had led to a series of problems, such as drug resistances, and was harmful to human health [6,7]. Investigators had been searching for new natural products to control A. flavus reproduction and to reduce AFTs contamination

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