Litsea cubeba essential oil as the potential natural fumigant: Inhibition of Aspergillus flavus and AFB1 production in licorice

Abstract The study aimed to investigate the inhibitory activities of Litsea cubeba essential oil (LC-EO) on Aspergillus flavus and aflatoxin B1 production in licorice. The main chemical compositions of LC-EO, analyzed by gas chromatography–mass spectrometry (GC–MS), were (Z)-Limonene oxide (30.14%), (E)-Limonene oxide (27.92%) and D-Limonene (11.86%). The “ in vitro ” antifungal and antiaflatoxigenic properties of LC-EO were evaluated upon A. flavus . The headspace volatile assay showed more effective inhibition against A. flavus mycelial growth than contact assay with tested different concentrations of LC-EO. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of LC-EO were 0.5 and 1.0 μL/mL with fumigation, respectively. The EO exhibited a high toxicity against three toxigenic isolates of A. flavus . Morphological investigation performed by the scanning electron microscopy (SEM) showed that the hyphae and conidiophores structures underwent alterations, following the treated with LC-EO. The fumigated hyphae grow abnormally, were introcession, enation and wilting of the cell surface, featuring the flat strip shape. Meanwhile, in view of the antifungal and antiaflatoxigenic activities, LC-EO was also assessed the inhibitory effect of AFB 1 production “ in situ ” investigation on Chinese herbal medicines (CHMs) system by volatile assay. The results showed that LC-EO could strongly inhibit the accumulation of aflatoxin B 1 in licorice after being inoculated and incubated with A. flavus for 20 days. Thus, LC-EO can potentially be used as a highly efficient and eco-friendly antifungal fumigant to control post-harvest fungi and AFB 1 production in licorice in the storage process.