Carvacrol nanoemulsion achieves potent suppression of Aspergillus niger on high-moisture fruits by disrupting carbon-nitrogen metabolic homeostasis and triggering oxidative stress

Aspergillus niger is the principal postharvest spoilage fungus of high-moisture fruits, causing substantial food waste and economic losses. Carvacrol, a plant‑derived phenolic, exhibits significant antifungal potential against A. niger , while the specific target and molecular mechanism requires further elucidation, and poor solubility hinders application. Here, we developed a carvacrol nanoemulsion (CN) stabilized by OSA-modified starch nanoparticles to overcome this limitation and elucidated the antifungal mechanism against A. niger . Compared to ethanol-dissolved carvacrol (CE), CN exhibited superior antifungal efficacy with nano-sized droplets enhancing cell membrane penetration, resulting in a lower MIC (156.25 mg/L) than CE (312.5 mg/L). CN induced more severe hyphal membrane and ultrastructural damage, as well as severe ultrastructural damage, ROS accumulation, electrolyte leakage, reduced ergosterol and ATP contents, and elevated MDA levels in A. niger . Furthermore, in vivo experiments demonstrated that CN reduced the lesion diameter of representative fruits (kiwifruit and strawberries) during storage. Integrated transcriptomics and proteomics revealed that CN profoundly disrupted the metabolic homeostasis of A. niger . Specifically, while A. niger upregulated ABC transporters to efflux carvacrol, mitochondrial oxidative phosphorylation downregulation caused ATP deficiency. Meanwhile, CN treatment suppressed key genes/proteins in alanine, aspartate, glutamate metabolism, and propanoate metabolism, blocking nitrogen assimilation, nucleotide synthesis, and toxic intermediate detoxification. The oxidative damage, biosynthetic arrest, and impaired DNA replication and repair functions induced by CN resulted in membrane damage and macromolecule leakage, ultimately causing irreversible cell death. This study elucidated the antifungal mechanism of carvacrol at physiological and molecular levels, providing a theoretical basis for controlling postharvest decay using nanoemulsion technology.