Three stilbenes make difference to the antifungal effects on ochratoxin A and its precursor production of Aspergillus carbonarius.

The present study demonstrated the toxic effects of stilbenes on fungi, which were related to the structures of the stilbenes. Pterostilbene with methoxy had the best antifungal properties, followed by piceatannol, which has a catechol structure, and finally resveratrol. The inhibitory effects of stilbenes at 0.1, 0.2, 0.4, 0.8, 1.6 mM on A. carbonarius mycelia growth and spore germination were assessed by plate inhibition tests and poisoned food technique. Predicted by SPSS software, the IC50 values of resveratrol, piceatannol, and pterostilbene were 5.10, 1.80, and 0.28 mM, respectively. In addition, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that 0.4 mM pterostilbene treatment induced incompleteness of the sporangium and distortion of the mycelial structure. Antitoxic activities of stilbenes were positively correlated with their antifungal activities. 1.6 mM pterostilbene suppressed OTA synthesis better (63.48%) than 1.6 mM piceatannol (25.91%) and 1.6 mM resveratrol (22.98%). Furthermore, in the presence of stilbenes, the examined biosynthetic genes, and regulatory factors like NRPS, PKS, LaeA, HAL, bZIP, and P450 were remarkably downregulated to reduce OTA/OTB production. Increased levels of total stilbenes in grapes after fungal infestation can slow down the increased rate in OTA levels. It indicated stilbenes could be used as naturally safe and efficient compounds in food active packaging or preservatives against OTA in food.

Alginate with citrus pectin and pterostilbene as healthy food packaging with antioxidant property.

A new type of film packaging made from natural polysaccharide materials, with its environmental safety and friendliness, is considered as a potential substitute for plastics. Novel polysaccharide composite films based upon citrus pectin (CP) and sodium alginate (SA) were successfully prepared and characterized, containing pterostilbene (PTE) at various concentrations (0.2, 0.4, 0.8, 1.6, 3.2 mM). The rheological analysis displayed that all film-forming liquids performed no gelation behavior with G" > G' at low frequency and weak gelation with G" < G' at high frequency. The SA-CP films had good tensile strength (TS) and elongation at break (EB), while adding PTE as an antioxidant to the film reduced both the values. Of note, the SA-CP films with PTE had better moisture resistance than that of the pure SA-CP films, which was related to the changes of its microstructure. The increased roughness of the films containing PTE was observed by microscope. After calcium chloride cross-linking, the water solubility of the films was reduced, while its thermal stability was improved. Notably, the accretion of PTE expressively enhanced the antioxidant properties of the SA-CP films. Thus, the SA-CP composite films containing PTE could be utilized as an excellent antioxidant packaging material.

Peppermint Essential Oil Suppresses Geotrichum citri-aurantii Growth by Destructing the Cell Structure, Internal Homeostasis, and Cell Cycle.

Peppermint essential oil (Peo) is an efficient antifungal agent, and 2.0 µL of Peo per milliliter culture medium can completely inhibit the mycelium growth and spore germination of Geotrichum citri-aurantii. In vitro experiments showed that the main functional component in Peo was l-menthol, which could lead to changes in sugar and protein contents, reduce the content of alkaline phosphatase (AKP), and destroy the spore membrane structure, with a significant increase in electrical conductivity. Meanwhile, the content of reactive oxygen (ROS) accumulated sharply, and the enzyme activity changed significantly with the change in the gene expression level. In addition, l-menthol could cause degradation in spore genetic material differently. Furthermore, a total of 1704 differentially expressed genes (DEGs) in G. citri-aurantii after 1.6 µL/mL l-menthol exposure for 2 h were obtained by the transcriptome sequencing. These DEGs were involved in transmembrane transport, carbohydrate transmembrane transport protein activity, and mitogen-activated protein kinase (MAPK) signaling pathway. The protein-protein interaction (PPI) analysis of DEGs yielded 10 highly cross-linked nodes, and these genes were associated with DNA replication and cell cycle. The expression level of the hub gene was confirmed by real-time quantitative PCR (RT-qPCR), with the most significant changes in POL 30 (5.9-fold). Molecular simulation was performed and it was found that the binding site between l-menthol and POL 30 was the 44th ARG residue in POL 30, and it was speculated that l-menthol and POL 30 may be combined by hydrogen bonding interaction. The results of flow cytometry assay showed that l-menthol blocked the replication process in the S-phase of G. citri-aurantii. This study provides new insights into the development and application of Peo in food safety.