Antifungal mechanism and ultrasonic nanoemulsion of Litsea cubeba (Lour.) Pers. essential oil against Aspergillus niger

Citral-based essential oils (EO), such as Litsea cubeba (Lour.) Pers. EO (LCEO), exhibit potent inhibitory activity against Aspergillus Niger , positioning them as promising natural preservatives. This study aimed to further develop LCEO nanoemulsion by first elucidating the antifungal mechanism of its major component, citral, against A. niger . The antifungal mechanism of citral against A. niger was investigated by measuring the indices related to apoptosis, including reactive oxygen species (ROS), enzyme activities, amount of apoptosis, integrity of cell membrane and cell wall. After the composition was analyzed by gas chromatography-mass spectrometry (GC-MS), the LCEO nanoemulsion was prepared by ultrasonic, and the antifungal effect was monitored by hyperspectral microscopy. Citral, as the main component of LCEO (62.61%), was found to induce apoptosis by increasing ROS content, increasing the activity of enzymes associated with Nitric oxide (NO) synthesis and apoptosis, and disrupting the integrity of the cell membrane and cell wall of A. niger . The optimized LCEO nanoemulsion exhibited desirable physicochemical properties, including a milky-white appearance, nearly spherical and evenly dispersed droplets with an average particle size of 119.8 nm (PDI = 0.216), high encapsulation efficiency, and enhanced water solubility. Furthermore, it demonstrated excellent storage stability, sustained release behavior, and potent inhibitory activity against A. niger . The results demonstrated that citral-based EO can inhibit the growth of A. niger , providing a broad prospect for the development of environmentally friendly antifungal products.