Antifungal properties and inhibitory effects upon aflatoxin production of Thymus vulgaris L. by Aspergillus flavus Link

Assessment of Trachyspermum ammi essential oil against Aspergillus flavus, aflatoxin B1 contamination, and post-harvest quality of Sorghum bicolor

The present investigation explored the antifungal effectiveness of Trachyspermum ammi essential oil (TAEO) against Aspergillus flavus, aflatoxin B1 (AFB1) contamination, and its mechanism of action using biochemical and computational approaches. The GC-MS result revealed the chemical diversity of TAEO with the highest percentage of γ-terpinene (39 %). The TAEO exhibited minimum inhibitory concentration against A. flavus growth (0.5 µL/mL) and AFB1 (0.4 µL/mL) with radical scavenging activity (IC50 = 2.13 µL/mL). The mechanism of action of TAEO was associated with the alteration in plasma membrane functioning, antioxidative defense, and carbon source catabolism. The molecular dynamic result shows the multi-regime binding of γ-terpinene with the target proteins (Nor1, Omt1, and Vbs) of AFB1 biosynthesis. Furthermore, TAEO exhibited remarkable in-situ protection of Sorghum bicolor seed samples against A. flavus and AFB1 contamination and protected the nutritional deterioration. Hence, the study recommends TAEO as a natural antifungal agent for food protection against A. flavus mediated biodeterioration.

Essential oils: An eco-friendly alternative for controlling toxigenic fungi in cereal grains

Fungi are widely disseminated in the environment and are major food contaminants, colonizing plant tissues throughout the production chain, from preharvest to postharvest, causing diseases. As a result, grain development and seed germination are affected, reducing grain quality and nutritional value. Some fungal species can also produce mycotoxins, toxic secondary metabolites for vertebrate animals. Natural compounds, such as essential oils, have been used to control fungal diseases in cereal grains due to their antimicrobial activity that may inhibit fungal growth. These compounds have been associated with reduced mycotoxin contamination, primarily related to reducing toxin production by toxigenic fungi. However, little is known about the mechanisms of action of these compounds against mycotoxigenic fungi. In this review, we address important information on the mechanisms of action of essential oils and their antifungal and antimycotoxigenic properties, recent technological strategies for food industry applications, and the potential toxicity of essential oils.

Thyme Extract Alleviates High-Fat Diet-Induced Obesity and Gut Dysfunction

Prolonged intake of a high-fat diet (HFD) disturbs the composition of gut microbiota, contributing to the development of metabolic diseases, notably obesity and increased intestinal permeability. Thyme (Thymus vulgaris L.), an aromatic plant, is known for its several therapeutic properties. In this study, we explored the potential of thyme extract (TLE) to mitigate HFD-induced metabolic derangements and improve the gut environment. Eight-week-old C57BL/6 mice were administered 50 or 100 mg/kg TLE for eight weeks. Administration of 100 mg/kg TLE resulted in decreased weight gain and body fat percentage, alongside the regulation of serum biomarkers linked to obesity induced by a HFD. Moreover, TLE enhanced intestinal barrier function by increasing the expression of tight junction proteins and ameliorated colon shortening. TLE also altered the levels of various metabolites. Especially, when compared with a HFD, it was confirmed that 2-hydroxypalmitic acid and 3-indoleacrylic acid returned to normal levels after TLE treatment. Additionally, we investigated the correlation between fecal metabolites and metabolic parameters; deoxycholic acid displayed a positive correlation with most parameters, except for colon length. In contrast, hypoxanthine was negatively correlated with most parameters. These results suggest a promising role for thyme in ameliorating obesity and related gut conditions associated with a HFD.

The significance of essential oils and their antifungal properties in the food industry: A systematic review

Essential oils (EOs) are natural products called volatile oils or aromatic and ethereal oils derived from various parts of plants. They possess antioxidant and antimicrobial properties, which offer natural protection against a variety of pathogens and spoilage microorganisms. Studies conducted in the last decade have demonstrated the unique applications of these compounds in the fields of the food industry, agriculture, and skin health. This systematic article provides a summary of recent data pertaining to the effectiveness of EOs and their constituents in combating fungal pathogens through diverse mechanisms. Antifungal investigations involving EOs were conducted on multiple academic platforms, including Google Scholar, Science Direct, Elsevier, Springer, Scopus, and PubMed, spanning from April 2000 to October 2023. Various combinations of keywords, such as "essential oil," "volatile oils," "antifungal," and "Aspergillus species," were used in the search. Numerous essential oils have demonstrated both in vitro and in vivo antifungal activity against different species of Aspergillus, including A. niger, A. flavus, A. parasiticus, A. fumigatus, and A. ochraceus. They have also exhibited efficacy against other fungal species, such as Penicillium species, Cladosporium, and Alternaria. The findings of this study offer novel insights into inhibitory pathways and suggest the potential of essential oils as promising agents with antifungal and anti-mycotoxigenic properties. These properties could make them viable alternatives to conventional preservatives, thereby enhancing the shelf life of various food products.

Recent advancements on use of essential oils as preservatives against fungi and mycotoxins spoiling food grains

Spoilage of grains by mycotoxigenic fungi poses a great threat to food security and human health. Conventionally used chemical agents to prevent grain fungi contamination cause increasingly significant problems such as microbial resistance, residual toxicity and environmental unfriendliness. In recent years, plant essential oils (EOs) have become a hot spot in the research of control of grain fungi and mycotoxins, due to their extensive sources, non-toxicity, environmental friendliness and good antifungal efficiency. The current review aims to provide an overview of the prevention of fungi and mycotoxins in grain through EOs. The antifungal and toxin inhibition efficiency of different EOs and their effective components are investigated. The inhibition mechanism of EOs on fungi and mycotoxins in grains is introduced. The influence of EOs treatment on the change of grain quality is also discussed. In addition, the formulations and techniques used to overcome the disadvantages of EOs application are introduced. The results of recent studies have confirmed that EOs provide great potential for controlling common fungi and mycotoxins in grains, and enhancing quantity and quality safety of grains.

Antioxidant Potential of Spray- and Freeze-Dried Extract from Oregano Processing Wastes, Using an Optimized Ultrasound-Assisted Method

Origanum vulgare is recognized worldwide for its numerous applications, in the food industry and beyond. However, the extraction of its essential oils generates a significant amount of waste. The aim of this research was to achieve the valorization of solid waste from oregano hydro-distillation, by (i) optimizing the ultrasound extraction of antioxidants, (ii) evaluating the effect of spray and freeze drying on the extract's physicochemical properties, and (iii) characterizing the obtained powder by its antioxidant capacity. A central composite design of experiments was used to optimize the sample/solvent ratio, ethanol/water ratio, and extraction time. The extract was analyzed for its antioxidant potential by determining the percentage of DPPH inhibition, FRAP, and total phenolic content (TPC). The GAB model best fit the data for the moisture sorption isotherm of the resulting powder. The antioxidant activity of the powders was tested in a ground-beef food system. The TPC was maximized at times longer than 58 min, a sample/solvent ratio between 0.058 and 0.078, and a ratio of ethanol/water around 1. Neither drying method significantly affected the antioxidant properties of the extract, even though the resulting powders from each showed a different morphology (determined using SEM). Encapsulation with maltodextrin protected the spray-dried extract during a 6-month storage period. Powders from both drying methods equally retarded lipid oxidation, and were comparable to the synthetic antioxidant BHT. It is concluded that oregano processing waste is a potent source of antioxidants, and that its dried extract, via an ultrasound-assisted process, can potentially be used as a natural alternative to synthetic antioxidants.

Lavandula x intermedia-A Bastard Lavender or a Plant of Many Values? Part II. Biological Activities and Applications of Lavandin

This review article is the second in a series aimed at providing an in-depth overview of Lavandula x intermedia (lavandin). In part I, the biology and chemistry of lavandin were addressed. In part II, the focus is on the functional properties of lavandin and its applications in industry and daily life. While reviewing the biological properties, only original research articles employing lavandin were considered. Lavandin essential oil has been found to have antioxidant and biocidal activity (antimicrobial, nematicidal, antiprotozoal, insecticidal, and allelopathic), as well as other potential therapeutic effects such as anxiolytic, neuroprotective, improving sleep quality, antithrombotic, anti-inflammatory, and analgesic. Other lavandin preparations have been investigated to a much lesser extent. The research is either limited or inconsistent across all studies, and further evidence is needed to support these properties. Unlike its parent species-Lavandula angustifolia (LA)-lavandin essential oil is not officially recognized as a medicinal raw material in European Pharmacopeia. However, whenever compared to LA in shared studies, it has shown similar effects (or even more pronounced in the case of biocidal activities). This suggests that lavandin has similar potential for use in medicine.

Antifungal Activity of Essential Oil and Plant-Derived Natural Compounds against Aspergillus flavus

Aspergillus flavus is a facultative parasite that contaminates several important food crops at both the pre- and post-harvest stages. Moreover, it is an opportunistic animal and human pathogen that causes aspergillosis diseases. A. flavus also produces the polyketide-derived carcinogenic and mutagenic secondary metabolite aflatoxin, which negatively impacts global food security and threatens human and livestock health. Recently, plant-derived natural compounds and essential oils (EOs) have shown great potential in combatting A. flavus spoilage and aflatoxin contamination. In this review, the in situ antifungal and antiaflatoxigenic properties of EOs are discussed. The mechanisms through which EOs affect A. flavus growth and aflatoxin biosynthesis are then reviewed. Indeed, several involve physical, chemical, or biochemical changes to the cell wall, cell membrane, mitochondria, and related metabolic enzymes and genes. Finally, the future perspectives towards the application of plant-derived natural compounds and EOs in food protection and novel antifungal agent development are discussed. The present review highlights the great potential of plant-derived natural compounds and EOs to protect agricultural commodities and food items from A. flavus spoilage and aflatoxin contamination, along with reducing the threat of aspergillosis diseases.

Inhibition of Essential Oils on Growth of Aspergillus flavus and Aflatoxin B1 Production in Broth and Poultry Feed

Aflatoxin B1 (AFB1), a common contaminant in food and feed during storage, does great harm to human and animal health. Five essential oils (thymol, carvacrol, cinnamaldehyde, eugenol, and citral) were tested for their inhibition effect against Aspergillus flavus (A. flavus) in broth and feed. Cinnamaldehyde and citral were proven to be most effective against A. flavus compared to others and have a synergistic effect when used simultaneously. The broth supplemented with cinnamaldehyde and citral was inoculated with A. flavus (106 CFU/mL) by using the checkerboard method, and mold counts and AFB1 production were tested on days 0, 1, 3, and 5. Similarly, 100 g poultry feed supplemented with the mixture of cinnamaldehyde and citral at the ratio 1:1 was also inoculated with A. flavus, and the same parameters were tested on days 0, 7, 14, and 21. In poultry feed, cinnamaldehyde and citral significantly reduced mold counts and AFB1 concentrations (p < 0.05). Results showed that cinnamaldehyde and citral have a positive synergy effect and could both inhibit at least 90% the fungal growth and aflatoxin B1 production at 40 μg/mL in broth and poultry feed, and could be an alternative to control aflatoxin contamination in food and feed in future.

A methanolic extract of Zanthoxylum bungeanum modulates secondary metabolism regulator genes in Aspergillus flavus and shuts down aflatoxin production

Aflatoxin B1 (AFB1) is a food-borne toxin produced by Aspergillus flavus and a few similar fungi. Natural anti-aflatoxigenic compounds are used as alternatives to chemical fungicides to prevent AFB1 accumulation. We found that a methanolic extract of the food additive Zanthoxylum bungeanum shuts down AFB1 production in A. flavus. A methanol sub-fraction (M20) showed the highest total phenolic/flavonoid content and the most potent antioxidant activity. Mass spectrometry analyses identified four flavonoids in M20: quercetin, epicatechin, kaempferol-3-O-rhamnoside, and hyperoside. The anti-aflatoxigenic potency of M20 (IC₅₀: 2-4 µg/mL) was significantly higher than its anti-proliferation potency (IC₅₀: 1800-1900 µg/mL). RNA-seq data indicated that M20 triggers significant transcriptional changes in 18 of 56 secondary metabolite pathways in A. flavus, including repression of the AFB1 biosynthesis pathway. Expression of aflR, the specific activator of the AFB1 pathway, was not changed by M20 treatment, suggesting that repression of the pathway is mediated by global regulators. Consistent with this, the Velvet complex, a prominent regulator of secondary metabolism and fungal development, was downregulated. Decreased expression of the conidial development regulators brlA and Medusa, genes that orchestrate redox responses, and GPCR/oxylipin-based signal transduction further suggests a broad cellular response to M20. Z. bungeanum extracts may facilitate the development of safe AFB1 control strategies.

Anti-mycotoxigenic and antifungal activity of ginger, turmeric, thyme and rosemary essential oils in deoxynivalenol (DON) and zearalenone (ZEA) producing Fusarium graminearum

This study aimed to evaluate the antimycotoxigenic effect of essential oils (EOs) obtained from four different aromatic plants on the production of deoxynivalenol (DON) and zearalenone (ZEA) by Fusarium graminearum. The EOs from ginger (GEO), turmeric (TEO), thyme (ThEO) and rosemary (REO) were obtained by hydrodistillation and identified by gas chromatography/mass spectrometry (GC/MS). The major compounds found were mostly monoterpenes and sesquiterpenes. The minimum inhibitory concentration (MIC) and minimum fungicide concentration (MFC) were 11.25, 364, 366 and 11,580 µg mL-1 for ThEO, GEO, REO and TEO, respectively. The results evidenced that the assessed EOs inhibited DON and partially ZEA production by F. graminearum. ThEO and GEO were the EOs with most potent antimycotoxigenic action for DON and ZEA, respectively. These EOs have shown promising results in vitro regarding inhibition of mycotoxin production and might be used in the future as substitutes for synthetic fungicides.

Combinational inhibitory action of essential oils and gamma irradiation for controlling Aspergillus flavus and Aspergillus parasiticus growth and their aflatoxins biosynthesis in vitro and in situ conditions

The purpose of this study was to investigate the effects of certain essential oils (star anise, lemon leaves, marjoram, fennel, and lavender) on the fungal growth of Aspergillus flavus and Aspergillus parasiticus and their production of aflatoxin B1 (AFB1). The degree of suppression of the aflatoxigenic strains' growth and their production of AFB1 is mainly affected by the kind and the concentration of the tested essential oils (EOs). Star anise essential oil had the lowest minimum inhibitory concentration (0.5 and 1.0 μL/mL) against A. flavus and A. parasiticus, respectively, so it was the best among the five different oils. The study of liquid chromatography with tandem mass spectrometry revealed that star anise EO resulted in a 98% reduction in AFB1 without a breakdown of AFB1 products after treatment thus the complete removal of AFB1 was done without any toxic residues. The combination showed a synergistic effect, the combinational treatment between γ-irradiation at a low dose (2 kGy) and star anise EO at concentrate 0.5 μL/g destroyed A. flavus and A. parasiticus inoculated (individually) in sorghum and peanut, respectively throughout the storage period (8 weeks).

Effect of the essential oils of Satureja montana L., Myristica fragrans H. and Cymbopogon flexuosus S. on mycotoxin-producing Aspergillus flavus and Aspergillus ochraceus antifungal properties of essential oils

Essential oils can be a useful alternative to the use of synthetic fungicides because they have biological potential and are relatively safe for food and agricultural products. The objectives of the present study were to evaluate the antifungal and antimycotoxigenic activities of the essential oils from Satureja montana L., Myristica fragrans H. and Cymbopogon flexuosus S. against Aspergillus flavus and Aspergillus ochraceus, as well as their effects on ergosterol synthesis and membrane morphology. The antifungal potential was evaluated by mycelial growth analysis and scanning electron microscopy. Fungicidal effects against A. flavus, with MFC of 0.98, 15.62 and 0.98 µL/mL, respectively, were observed for the essential oils from S. montana, M. fragrans and C. flexuosus. Aspergillus ochraceus did not grow in the presence of concentrations of 3.91, 15.62 and 0.98 µL/mL of the essential oils from S. montana, M. fragrans and C. flexuosus, respectively. The essential oils significantly inhibited the production of ochratoxin A by the fungus A. ochraceus. The essential oils also inhibited the production of aflatoxin B1 and aflatoxin B2. The biosynthesis of ergosterol was inhibited by the applied treatments. Biological activity in the fungal cell membrane was observed in the presence of essential oils, given that deleterious effects on the morphologies of the fungi were detected. The essential oils under study are promising as food preservatives because they significantly inhibit toxigenic fungi that contaminate food. In addition, the essential oils hindered the biosynthesis of mycotoxins.

Antiaflatoxigenic potential of essential oils of spices – a review

Mycotoxins are important food contaminants posing a significant threat to food and feed safety and public health. Among the mycotoxins, aflatoxins are deemed to be a more significant contaminant due to their potent carcinogenic, and hepatotoxic effects, and their levels are highly regulated in the international food trade. Phytochemicals are considered a major source of natural antifungal agents. The volatile nature of essential oil of plants makes them ideal candidates for antifungal agents due to their ability to distribute in free air spaces in closed containers and penetrate through heterogeneous food materials. In these, essential oils in spices attain special attention due to their commercial availability and low toxicity. This article reviews the antiaflatoxigenic capacity of spice essential oils and the effect of essential oil composition on the activity and mechanism of antifungal action and is expected to be useful for the planning of further research in the subject area.

A Novel Sulfone Derivative Controls Lasiodiplodia theobromae in Tea Leaf Spot by Reducing the Ergosterol Content

Diseases caused by fungi can affect the quality and yield of the leaves of tea [Camellia sinensis (L.) Kuntze]. At present, the availability of highly effective and safe fungicides for controlling tea plants remains limited. The objectives of this study were to identify novel compounds with antifungal activities and to determine their molecular mechanisms. A series of sulfone compounds containing 1,3,4-oxadiazole were evaluated in China for their antifungal activities against several pathogens causing foliar diseases and high production losses. Transcriptomics and bioinformatics were used to analyze the differentially expressed genes of Lasiodiplodia theobromae treated with a representative compound, jiahuangxianjunzuo (JHXJZ). Moreover, the effects of JHXJZ on ergosterol content, membrane permeability, cell structure, and seven key genes involved in the ergosterol biosynthetic pathway were investigated. JHXJZ had a strong antifungal activity against L. theobromae in vitro, with an effective concentration giving 50% inhibition of 3.54 ± 0.55 μg/ml, and its curative efficacies on detached tea leaves reached 41.78% at 100 μg/ml. JHXJZ upregulated 899 genes (P < 0.05) and downregulated 1,185 genes (P < 0.05) in L. theobromae. These genes were found to be associated with carbohydrate metabolic processes, which are closely related to steroid biosynthesis in the Kyoto Encyclopedia of Genes and Genomes pathways. Because JHXJZ regulates the key genes of sterol biosynthesis, it decreased the ergosterol content, increased cell-membrane permeability, changed the cellular structure, enhanced the roughness of the surface of the hyphae, and resulted in degradation of the hyphal nuclei and necrosis of the hyphal cytoplasm. Our study demonstrates that JHXJZ is a fungicide with a novel mechanism of action that differs from that of triazole fungicides. JHXJZ has potential for applications in controlling tea plant diseases.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Inhibition of Fungal Strains Isolated from Cereal Grains via Vapor Phase of Essential Oils

Fungal contamination in stored food grains is a global concern and affects food economics and human and animal health. It is clear that there is a need to develop new technologies with improved performances that are also eco-friendly in nature. Due to the bioactivity of essential oils (EOs) in the vapor phase, their low toxicity for humans, and their biodegradability and antifungal properties, EOs could be a suitable solution. In this study, we explored the potential of thyme, oregano, lemongrass, clove, and cajeput EOs in the vapor phase. For 17 days, inhibitory activity was assessed against five strains of postharvest pathogens-Aspergillus spp., Fusarium s. l. spp., and Penicilliumochrochloron-isolated from cereal grains. A modified disc volatilization method was used, which is more effective in comparison to traditional screening methods. Three concentrations were tested (250, 125, and 62.5 μL/L). The two highest concentrations resulted in complete inhibition of fungal growth; however, even 62.5 μL/L showed a significant antifungal effect. The efficiency of EOs followed this order: thyme > oregano > lemongrass > clove > cajeput. From our findings, it appears that the use of EOs vapors is a better option not only for laboratory experiments, but for subsequent practice.

A review of the methods used to determine the target site or the mechanism of action of essential oils and their components against fungi

Essential oils (EOs) are complex mixtures of compounds derived from plants that exhibit antimicrobial activity. Several studies have demonstrated their antifungal activity in food matrices or in vitro via vapor phase or direct addition. Recently, researchers are focusing on elucidating the target site or the mechanism of action of various EOs. Past research has suggested evidence of how EOs act in the fungal cells via assays assessed from cell wall alterations or gene expression modifications. However, no previous reports have summarized most methods for finding the target site of the mechanism of action for EOs. Therefore, this review presents the methods and assays used to discover the target site or the mechanism of action of EOs against fungal cells. Researchers commonly analyze the plasma membrane integrity using various techniques as well as the changes in cell morphology. Meanwhile, the quantification of the activity of the mitochondrial enzymes, ROS species, and gene expression are less assayed.

Nanoencapsulated Essential Oils with Enhanced Antifungal Activity for Potential Application on Agri-Food, Material and Environmental Fields

Nanotechnology is a new frontier of this century that finds applications in various fields of science with important effects on our life and on the environment. Nanoencapsulation of bioactive compounds is a promising topic of nanotechnology. The excessive use of synthetic compounds with antifungal activity has led to the selection of resistant fungal species. In this context, the use of plant essential oils (EOs) with antifungal activity encapsulated in ecofriendly nanosystems could be a new and winning strategy to overcome the problem. We prepared nanoencapsules containing the essential oils of Origanum vulgare (OV) and Thymus capitatus (TC) by the nanoprecipitation method. The colloidal suspensions were characterized for size, polydispersity index (PDI), zeta potential, efficiency of encapsulation (EE) and loading capacity (LC). Finally, the essential oil nanosuspensions were assayed against a panel of fourteen fungal strains belonging to the Ascomycota and Basidiomycota phyla. Our results show that the nanosystems containing thyme and oregano essential oils were active against various fungal strains from natural environments and materials. In particular, the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were two to four times lower than the pure essential oils. The aqueous, ecofriendly essential oil nanosuspensions with broad-spectrum antifungal activity could be a valid alternative to synthetic products, finding interesting applications in the agri-food and environmental fields.

Antibacterial, Antifungal, Antimycotoxigenic, and Antioxidant Activities of Essential Oils: An Updated Review

The interest in using natural antimicrobials instead of chemical preservatives in food products has been increasing in recent years. In regard to this, essential oils-natural and liquid secondary plant metabolites-are gaining importance for their use in the protection of foods, since they are accepted as safe and healthy. Although research studies indicate that the antibacterial and antioxidant activities of essential oils (EOs) are more common compared to other biological activities, specific concerns have led scientists to investigate the areas that are still in need of research. To the best of our knowledge, there is no review paper in which antifungal and especially antimycotoxigenic effects are compiled. Further, the low stability of essential oils under environmental conditions such as temperature and light has forced scientists to develop and use recent approaches such as encapsulation, coating, use in edible films, etc. This review provides an overview of the current literature on essential oils mainly on antifungal and antimycotoxigenic but also their antibacterial and antioxidant activities. Additionally, the recent applications of EOs including encapsulation, edible coatings, and active packaging are outlined.

Effect of thermal processing and traditional flavouring mixture on mycotoxin reduction in pistachio

The effect of heating (roasting and microwave radiation heating) along with a traditional pistachio flavouring mixture (containing verjuice, thyme extract, and sodium chloride) was investigated on reducing aflatoxins (AFs) and ochratoxin A (OTA) in pistachios. The naturally and artificially contaminated samples were soaked in the flavouring mixture (for 5, 10 and 24 h) and then subjected to roasting (at 120 and 150 °C for 50 min) and heating by microwave radiation (6 and 10 min). The residual mycotoxins were determined by high-performance liquid chromatography. The results showed that all treatments were able to reduce mycotoxin content (aflatoxin B1, B2, G1, G2 and OTA) significantly (P<0.05), up to 85.7±2.5% (during roasting) and up to 72.5±2.6% (during heating by microwave radiation). The highest reduction of AFs and OTA (ranging from 51.7±2.3 to 85.7±2.5%) was found when the contaminated (naturally and artificially) samples were soaked in the traditional mixture for 24 h and roasted at 150 °C. It could be concluded that the traditional flavouring method in combination with the roasting process or heating by microwave radiation could be applied as a useful and safe method for mycotoxin degradation in pistachio. Although, complete elimination of mycotoxins was not achieved, the method reduced mycotoxins more than 60% without adverse effect on the taste and appearance of pistachios.

Thyme Antimicrobial Effect in Edible Films with High Pressure Thermally Treated Whey Protein Concentrate

Application of high pressure-thermal treatment (600 MPa and 70 °C, 20 min) for obtaining edible films functionalized with thyme extracts have been studied in order to evaluate the antimicrobial capacity of films structure to retain and release the bioactive compounds. The high pressure-thermally treated films (HPT) were compared with the thermally treated (TT) ones (80 ± 0.5 °C, 35 min). The film structures were analyzed and the sorption isotherms, water vapor permeability, antimicrobial activity and the volatile fingerprints by GC/MS were performed. The HPT film presented more binding sites for water chemi-sorption than TT films and displayed significantly lower WVP than TT films (p < 0.05). TT films displayed slightly, but significant higher, antimicrobial activity (p < 0.05) against Geotrichum candidum in the first day and against Bacillus subtilis in the 10th day of storage. The HPT film structure had ~1.5-fold higher capacity to retain volatiles after drying compared to TT films. From the HPT films higher amount of p-cymene and α-terpinene was volatilized during 10 days of storage at 25 °C, 50% RH while from the TT films higher amount of caryophyllene and carvacrol were released. During storage HPT films had a 2-fold lower capacity to retain monoterpenes compared to TT films.

Plant Bioactive Compounds in Pre- and Postharvest Management for Aflatoxins Reduction

Aflatoxins (AFs) are secondary metabolites produced by Aspergillus spp., known for their hepatotoxic, carcinogenic, and mutagenic activity in humans and animals. AF contamination of staple food commodities is a global concern due to their toxicity and the economic losses they cause. Different strategies have been applied to reduce fungal contamination and AF production. Among them, the use of natural, plant-derived compounds is emerging as a promising strategy to be applied to control both Aspergillus spoilage and AF contamination in food and feed commodities in an integrated pre- and postharvest management. In particular, phenols, aldehydes, and terpenes extracted from medicinal plants, spices, or fruits have been studied in depth. They can be easily extracted, they are generally recognized as safe (GRAS), and they are food-grade and act through a wide variety of mechanisms. This review investigated the main compounds with antifungal and anti-aflatoxigenic activity, also elucidating their physiological role and the different modes of action and synergies. Plant bioactive compounds are shown to be effective in modulating Aspergillus spp. contamination and AF production both in vitro and in vivo. Therefore, their application in pre- and postharvest management could represent an important tool to control aflatoxigenic fungi and to reduce AF contamination.

Nanoencapsulated Monarda citriodora Cerv. ex Lag. essential oil as potential antifungal and antiaflatoxigenic agent against deterioration of stored functional foods

In vitro antifungal activity of the essential oil from Monarda citriodora (MCEO) with possible mode of action was evaluated against A. flavus (AF-LHP-SH1) and 15 other storage molds for controlling postharvest deterioration of stored functional food samples. The chemical profiling of MCEO as done through GC-MS analysis revealed caryophyllene (19.15%) as the major component. The MCEO showed broad spectrum fungitoxicity and completely inhibited the growth of all tested molds and aflatoxin B₁ (AFB₁) production by AF-LHP-SH1 at 1.40 and 1.20 µL/mL, respectively. Plasma membrane damage and methylglyoxal inhibition was confirmed as the possible antifungal and antiaflatoxigenic mode of action of MCEO. MCEO exhibited remarkable antioxidant activity with IC₅₀ value 2.24 μL/mL as determined through DPPH assay and did not cause adverse effect on seed germination. In addition, the MCEO was encapsulated into chitosan nanoparticle, characterized (SEM, FTIR, XRD) and assessed for their potential against inhibition of growth and AFB₁ production. MCEO after encapsulation exhibited enhanced efficacy inhibiting fungal growth and AFB₁ production by AF-LHP-SH1 at 0.6 and 0.5 µL/mL, respectively. Encapsulated MCEO may be recommended as novel preservative to extend the shelf life of stored functional food samples.

Dextran-Thyme Magnesium-Doped Hydroxyapatite Composite Antimicrobial Coatings

The dextran-thyme magnesium-doped hydroxyapatite (10MgHAp-Dex-thyme) composite layers were prepared by a dip-coating procedure from stable suspensions and further analyzed for the first time. Different characterization techniques were employed to explore the physical-chemical features of the 10MgHAp-Dex-thyme suspensions and derived coatings. Information regarding the 10MgHAp-Dex-thyme suspensions was extracted on the basis of dynamic light scattering, zeta potential, and ultrasound measurements. The crystalline quality of the biocomposite powders—resulting after the centrifugation of suspensions—and the layers deposited on glass was assessed by X-ray diffraction in symmetric and grazing incidence geometries, respectively. The chemical structure and presence of functional groups were evaluated for both powder and coating by Fourier transform infrared spectroscopy in attenuated total reflectance mode. The extent of the antimicrobial effect range of the biocomposite suspensions and coatings was tested against different Gram-positive and Gram-negative bacteria (Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Pseudomonas aeruginosa) and fungus (Candida albicans) strains with promising results.

Essential Oils of Lamiaceae Family Plants as Antifungals

The incidence of fungal infections has been steadily increasing in recent years. Systemic mycoses are characterized by the highest mortality. At the same time, the frequency of infections caused by drug-resistant strains and new pathogens e.g., Candida auris increases. An alternative to medicines may be essential oils, which can have a broad antimicrobial spectrum. Rich in the essential oils are plants from the Lamiaceae family. In this review are presented antifungal activities of essential oils from 72 Lamiaceae plants. More than half of these have good activity (minimum inhibitory concentrations (MICs) < 1000 µg/mL) against fungi. The best activity (MICs < 100) have essential oils from some species of the genera Clinopodium, Lavandula, Mentha, Thymbra, and Thymus. In some cases were observed significant discrepancies between different studies. In the review are also shown the most important compounds of described essential oils. To the chemical components most commonly found as the main ingredients include β-caryophyllene (41 plants), linalool (27 plants), limonene (26), β-pinene (25), 1,8-cineole (22), carvacrol (21), α-pinene (21), p-cymene (20), γ-terpinene (20), and thymol (20).

Comparison of the Antifungal and Antiaflatoxigenic Potential of Liquid and Vapor Phase of Thymus vulgaris Essential Oil against Aspergillus flavus

The antifungal and antiaflatoxigenic activity of Thymus vulgaris essential oil (EO) against Aspergillus flavus was evaluated over a range of concentrations in vapor- and liquid-phase contact tests. Total reduction in mycelial growth in the vapor- and liquid-phase tests was detected at EO concentrations of 20 and 400 μg/mL, respectively. Treatment with 10 μg/mL EO reduced aflatoxin production by 97.0 and 56.4% in the vapor- and liquid-phase tests, respectively. Greater inhibition of the expression of both fungal development-related genes (brlA, abaA, and wetA) and aflatoxin biosynthesis-related genes (aflR, aflD, and aflK) was also observed in the vapor-phase test. A substantial reduction in aflatoxin production was also observed in brown rice (72.7%) and white rice (18.0%). Our results indicate that the way this EO contacts fungal cells significantly affects its antifungal activity and that T. vulgaris EO in vapor phase might be a good strategy to control fungal contamination.

Essential oils and their bioactive compounds as green preservatives against fungal and mycotoxin contamination of food commodities with special reference to their nanoencapsulation

Fungal and mycotoxin contamination of stored food items is of utmost concern throughout the world due to their hazardous effects on mammalian systems. Most of the synthetic chemicals used as preservatives have often been realised to be toxic to humans and also cause adverse environmental effects. In this respect, use of different plant products especially essential oils (EOs) and their bioactive compounds has been recognized as a green strategy and safer alternatives to grey synthetic chemicals in view of their long traditional use. The current nanoencapsulation technology has strengthened the prospective of EOs and their bioactive compounds in food preservation by enhancing their bioactivity and mitigating other problems regarding their large-scale application. Although, the antimicrobial potential of EOs and their bioactive compounds has been reviewed time to time by different food microbiologists, but very less is known about their mode of action. Based on these backgrounds, the present article provides an account on the antifungal and antimycotoxigenic mode of action of EOs as well as their bioactive compounds. In addition, the article also deals with the application of currently used nanoencapsulation approach to improve the stability and efficacy of EOs and their bioactive compounds against mycotoxigenic fungi causing deterioration of stored food items so as to recommend their large-scale application for safe preservation and enhancement of shelf life of food items during storage.

Antimicrobial and antioxidant activities of hydrocarbon and oxygenated monoterpenes against some foodborne pathogens through in vitro and in silico studies

The present work describes the antimicrobial action of 25 monoterpenes (six hydrocarbons, five ketones, two aldehydes, six alcohols and six acetate analogues) against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus and antifungal activity against Aspergillus flavus. The antibacterial activity was evaluated by broth microdilution technique as a minimum inhibitory concentration (MIC) and the antifungal activity was performed by mycelia radial growth technique as the effective concentration causing 50% inhibition of the mycelial growth (EC₅₀). The results showed that thymol and α-terpineol were the most potent against E. coli (MIC = 45 and 55 mg/L, respectively) and S. aureus (MIC = 135 and 225 mg/L, respectively). The results also showed that thymol displayed the maximum antifungal action against A. flavus with EC₅₀ 20 mg/L. Furthermore, the antioxidant activity was determined using N,N-dimethyl-1,4-phenylenediamine (DMPD) and the results showed that geraniol were the most potent compound (IC₅₀ = 19 mg/L). Molecular docking studies indicated that the compounds displayed different binding interactions with the amino acid residues at the catalytic sites of N5-carboxyaminoimidazole synthetase and oxysterol binding protein Osh4 enzymes. Non-covalent interactions including van der Waals, hydrogen bonding as well as hydrophobic were observed between the compounds and the enzymes. A significant relationship was found between the docking score and the biological activity of the tested monoterpenes compared to the ceftriaxone and carbendazim as standard bactericide and fungicide, respectively. In silico ADMET properties were also performed and displayed potential for the development of promising antimicrobial agents. For these reasons, these compounds may be considered as potential ecofriendly alternatives in food preservation to delay or prevent the microbial infection and prolong the shelf life of food products.

Essential Oils as Antimicrobial Agents-Myth or Real Alternative?

Herbs and the essential oils derived from them have been used from the beginning of human history for different purposes. Their beneficial properties have been applied to mask unpleasant odors, attract the attention of other people, add flavor and aroma properties to prepared dishes, perfumes, and cosmetics, etc. Herbs and essential oils (EOs) have also been used in medicine because of their biological properties, such as larvicidal action, analgesic and anti-inflammatory properties, antioxidant, fungicide, and antitumor activities, and many more. Many EOs exhibit antimicrobial properties, which is extremely important in fields of science and industry, such as medicine, agriculture, or cosmetology. Among the 250 EOs which are commercially available, about a dozen possess high antimicrobial potential. According to available papers and patents, EOs seem to be a potential alternative to synthetic compounds, especially because of the resistance that has been increasingly developed by pathogenic microorganisms. In this review we summarize the latest research studies about the most-active EOs that are known and used because of their antimicrobial properties. Finally, it is noteworthy that the antimicrobial activities of EOs are not preeminent for all strains. Further investigations should, thus, focus on targeting EOs and microorganisms.

( E)-2-Hexenal, as a Potential Natural Antifungal Compound, Inhibits Aspergillus flavus Spore Germination by Disrupting Mitochondrial Energy Metabolism

Fungal contamination imposes threats to agriculture and food production and human health. A method to safely and effectively restrict fungal contamination is still needed. Here, we report the effect and mode of action of ( E)-2-hexenal, one of the green leaf volatiles (GLVs), on the spore germination of Aspergillus flavus, which can contaminate a variety of crops. The EC₅₀ value, minimum inhibitory concentration (MIC), and minimum fungicidal concentration (MFC) of ( E)-2-hexenal were 0.26, 1.0, and 4.0 μL/mL, respectively. As observed by scanning electron microscopy (SEM), the surface morphology of A. flavus spores did not change after treatment with the MIC of ( E)-2-hexenal, but the spores were shrunken and depressed upon treatment with the MFC of ( E)-2-hexenal. The MIC and MFC of ( E)-2-hexenal induced evident phosphatidylserine (PS) externalization of A. flavus spores as detected by double staining with Annexin V-FITC and propidium iodide, indicating that early apoptosis was potentially induced. Furthermore, sublethal doses of ( E)-2-hexenal disturbed pyruvate metabolism and reduced the intracellular soluble protein content of A. flavus spores during the early stage of germination, and MIC treatment decreased acetyl-CoA and ATP contents by 65.7 ± 3.7% and 53.9 ± 4.0% ( P < 0.05), respectively. Additionally, the activity of mitochondrial dehydrogenases was dramatically inhibited by 23.8 ± 2.2% ( P < 0.05) at the MIC of ( E)-2-hexenal. Therefore, the disruption of mitochondrial energy metabolism and the induction of early apoptosis are involved in the mechanism of action of ( E)-2-hexenal against A. flavus spore germination.

Effect of Zingiber officinale Roscoe essential oil in fungus control and deoxynivalenol production of Fusarium graminearum Schwabe in vitro

Members of the Fusarium genus are capable of contaminating agricultural commodities, compromising the quality of maize and other grains, which leads to severe quality and yield losses. Contamination with mycotoxins is also a concern. Essential oils are possible alternatives to the use of synthetic pesticides for control of fungal contamination, as many have antifungal and anti-mycotoxigenic properties and are innocuous to human health. They also do not cause any sort of microbial resistance and do not promote environmental pollution. The aim of this study was to evaluate the antifungal and anti-mycotoxigenic effects of Zingiber officinale Roscoe essential oil (GEO) upon Fusarium graminearum Schwabe in vitro. The essential oil was extracted by hydrodistillation and analysed by GC/MS. Antifungal and anti-mycotoxigenic activities were assessed by HPLC/UV by quantifying ergosterol and deoxynivalenol (DON), respectively. Results indicated that GEO inhibited ergosterol production at a concentration of 1000 µg/mL and DON production at a concentration of 500 µg/mL, evidencing that the anti-mycotoxigenic effect is independent of the antifungal effect due to its probable direct action upon toxin biosynthesis.

Probiotics and plant-derived compounds as eco-friendly agents to inhibit microbial toxins in poultry feed: a comprehensive review

Some of pathogenic bacteria and fungi have the ability to produce fetal toxins which may be the direct causes of cytotoxicity or cellular dysfunction in the colonization site. Biological and non-biological environmental factors, challenge and microbes influence the effect of toxins on these pathogens. Modern research mentions that many natural materials can reduce the production of toxins in pathogenic microbes. However, researches that explain the mechanical theories of their effects are meager. This review aimed to discuss the ameliorative potential role of plant-derived compounds and probiotics to reduce the toxin production of food-borne microbes either in poultry bodies or poultry feedstuff. Moreover, studies that highlight their own toxicological mechanisms have been discussed. Adding natural additives to feed has a clear positive effect on the enzymatic and microbiological appearance of the small intestine without any adverse effect on the liver. Studies in this respect were proposed to clarify the effects of these natural additives for feed. In conclusion, it could be suggested that the incorporation of probiotics, herbal extracts, and herbs in the poultry diets has some beneficial effects on productive performance, without a positive impact on economic efficiency. In addition, the use of these natural additives in feed has a useful impact on the microbiological appearance of the small intestine and do not have any adverse impacts on intestinal absorption or liver activity as evidenced by histological examination.

A review on antifungal activity and mode of action of essential oils and their delivery as nano-sized oil droplets in food system

An escalated demand of minimally processed food and increased negative perception for synthetic preservative has led to a lookout for a natural preservative. Essential oils (EOs) are volatile and aromatic secondary metabolites of plants that have been tapped mainly for its flavour and fragrances and various biological properties such as antimicrobial and antioxidant. The constituents and antifungal potential of EOs have been reported widely in the present scientific literature. Moreover, the current scientific research dealing with the mode of action of EOs on fungal spores and mycelial cells are very scarce, unlike bacteria. The antimicrobial efficacy of EO in real food system may alter due to interaction with food matrix components. Besides, minimum alteration in sensory qualities while retaining its maximum activity is the most sought-after criteria for food preservation with EOs. If the oil is applied in excess to have better antimicrobial activity, it may end up having an unacceptable organoleptic impact on the food. Appropriate edible delivery systems of EOs as an emulsion is a probable approach to retain the maximum efficacy of EOs in the food system. Nano-emulsification of EO could increase its bioactivity due to increased bioavailability in the food matrix. The basis of this review is to provide an overview of current knowledge about the antifungal properties and antifungal mode of action of EOs, and to recognize the application of EO as nano-sized oil droplets in the food system.

Current methods for mycotoxins analysis and innovative strategies for their reduction in cereals: an overview

Mycotoxins are secondary metabolites produced by moulds in food that are considered a substantial issue in the context of food safety, due to their acute and chronic toxic effects on animals and humans. Therefore, new accurate methods for their identification and quantification are constantly developed in order to increase the performance of extraction, improve the accuracy of identification and reduce the limit of detection. At the same time, several industrial practices have shown the ability to reduce the level of mycotoxin contamination in food. In particular, a decrease in the amount of mycotoxins could result from standard processes naturally used for food processing or by procedures strategically introduced during processing, with the specific aim of reducing the amount of mycotoxins. In this review, the current methods adopted for accurate analyses of mycotoxins in cereals (aflatoxins, ochratoxins, trichothecenes, fumonisins) are discussed. In addition, both conventional and innovative strategies adopted to obtain safer finished products from common cereals intended for human consumption will be explored and analysed. © 2018 Society of Chemical Industry.

Antifungal, Anti-aflatoxigenic, Antioxidant Activity and in vivo Efficacy of Essential Oil of the Aerial Parts of Thymus capitatus (L.) Hoffmanns & Link

Aspergillus flavus has been reported to be the most common fungus used as food by human beings. This fungus may have the potential to produce aflatoxin B1 (AFB1), which is reported as being the most hepatotoxic, teratogenic, mutagenic, and immunosuppressive to humans and other livestock. Therefore, the objective of this work was to study the chemical profile of Thymus capitatus essential oil (EO) and the inhibition of growth of Aspergillus flavus E73 and AFB1 production by the EO. The antioxidant activity and phytotoxicity were also evaluated. The gas chromatography– mass spectrometry (GC–MS) analysis showed that the major components of Thymus capitatus EO were thymol (25.82%), linalool (23.40%), geraniol (14.22%), pcymen- 3-ol (8.93%), and p-cymene (6.76%). The results showed that the EO could inhibit the growth of Aspergillus flavus E73 in the range of 40.72 to 87.00%. The minimal inhibitory concentration (MIC) of Thymus capitatus EO against Aspergillus flavus E73 was found to be at 1.00 mg/ml. The oil revealed complete inhibition of dry mycelium weight and AFB1 production at 1.00 mg/ml. The EO revealed a broad spectrum of fungitoxicity against some fungi. The antioxidant activity was also assessed where IC50 (when initial concentration is reduced to half) and β- carotene/linoleic acid inhibition percentage of Thymus capitatus EO were 619.16 ± 3.94 μg/ml and 65.55%, respectively, while the total phenolic content was 21.45 μg/mg. The EO showed non-phytotoxicity on two varieties of wheat seeds. These findings demonstrated that EO could be good alternative to protect food.

Effect of pseudolaric acid B on biochemical and physiologic characteristics in Colletotrichum gloeosporioides

In our previous study on natural products with fungicidal activity, pseudolaric acid B (PAB) isolated from Pseudolarix amabilis was examined to inhibit significantly mango anthracnose (Colletotrichum gloeosporioides) in vivo and in vitro. In the current study, sensitivity of 17 plant pathogenic fungi to PAB was determined. Mycelial growth rate results showed that PAB possessed strong antifungal activities to eleven fungi with median effective concentration (EC₅₀) values ranging from 0.087 to 1.927μg/mL. EC₅₀ of PAB against spore germination was greater than that of mycelium growth inhibition, which suggest that PAB could execute antifungal activity through mycelial growth inhibition. Further action mechanism of PAB against C. gloeosporioides was investigated, in which PAB treatment inhibited mycelia dry weight, decreased the mycelia reducing sugar and soluble protein. Furthermore, PAB induced an increase in membrane permeability, inhibited the biosynthesis of ergosterol, caused the extreme alteration in ultrastructure as indicated by the thickened cell wall and increased vesicles. These results will increase our understanding of action mechanism of PAB against plant pathogenic fungi.

Synergistic Antifungal, Allelopatic and Anti-Proliferative Potential of Salvia officinalis L., and Thymus vulgaris L. Essential Oils

The current study aimed to investigate the chemical composition and the synergistic potential of two essential oils (EOs), as obtained from Salvia officinalis L. (SEO), and Thymus vulgaris L. (TEO). The antifungal potential was tested in vitro against Fusarium graminearum (Fg 06_17), the herbicidal effect was studied using weed seeds of Amaranthus retroflexus (ARET), Chenopodium album (CALB), Echinochloa crus-galli (EGAL), but also wheat seeds (WS) of the Lovrin variety and tomato seeds Saint-Pierre of the variety. The GC-MS profile highlights that the mains compounds identified in SEO were: caryophyllene (25.364%), camphene (14.139%), eucalyptol (13.902%), and β-pinene (11.230%), while in TEO, the predominant phytochemicals were: γ-terpinene (68.415%) and p-thymol (24.721%). The results indicated that the tested EOs alone as well as in combination have allelopathic effect against investigated seeds, while the synergistic effect of TEO and SEO in terms of fungal growth was demonstrated at a level of 0.06%. Thyme and sage EOs exhibited in vitro anti-proliferative activity on two melanoma cell lines, namely A375 human melanoma and B164A5 mouse melanoma alone, as well as in combination. SEO was most effective in terms of decreasing the cell viability of murine and human melanoma cell lines when compared to TEO.

Thymus vulgaris L. extract has antimicrobial and anti-inflammatory effects in the absence of cytotoxicity and genotoxicity

OBJECTIVES

This study evaluated the biological effects of the T. vulgaris L. extract., such as antimicrobial activity on planktonic cultures and mono- and polymicrobial biofilms, cytotoxicity, anti-inflammatory activity and genotoxicity.

METHODS

Monomicrobial biofilms of Candida albicans, Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans and Pseudomonas aeruginosa and polymicrobial biofilms composed by C. albicans with each bacterium were formed for 48h and exposed for 5min to the plant extract. Murine macrophages (RAW 264.7), human gingival fibroblasts (FMM-1), human breast carcinoma cells (MCF-7) and cervical carcinoma cells (HeLa) were also exposed to the plant extract for 5min and the cell viability were analyzed by MTT, neutral red (NR) and crystal violet (CV) assays. Interleukin-1 beta (IL-1β) and tumor necrosis factor alpha (TNF-α) produced by RAW 264.7 was quantified by ELISA, after 24h exposure to the plant extract, both in the absence and presence of lipopolysaccharide (LPS) from Escherichia coli. Genotoxicity of the plant extract was evaluated by micronucleus formation (MN) in 1000 cells. The results were analyzed by T-Test or ANOVA and Tukey's Test (P≤0.05).

RESULTS

All biofilms showed significant reductions in CFU/mL (colony-forming units per milliliter). Cell viability was above 50% for all cell lines. Anti-inflammatory effect on the synthesis of IL-1β and TNF-α was observed. The MN was similar or lower than the control group in all cells.

CONCLUSIONS

T. vulgaris L. extract was effective against all biofilms, promoted high cell viability, anti-inflammatory effect and presented no genotoxicity.

Synergistic effects of some essential oils against fungal spoilage on pear fruit

The development of natural protective agents as alternatives to chemical fungicides is currently in the spotlight. In the present investigation, chemical composition and antifungal activities of thyme, cinnamon, rosemary and marjoram essential oils (EO), as well as synergism of their possible double and triple combinations were investigated. The compositions of the oils were determined by GC/MS. For determination of antifungal activity against Penicillium expansum and Botrytis cinerea, a broth microdilution method was used. The possible interactions of some essential oil combinations were performed by the two and three-dimensional checkerboard assay and isobologram construction. An in vivo antifungal assay was performed by artificial wounding of pear fruits. The maximum antifungal activity was demonstrated by thyme and cinnamon oils which displayed lower MIC values whereas rosemary and marjoram oils with MIC range between 2500 and 10,000μg/mL exhibited weak antifungal activities against tested fungi. In synergy testing, some double combinations (thyme/cinnamon, thyme/rosemary, cinnamon/rosemary) were found to be synergistic (FICi≤0.5). The triple combination of thyme, cinnamon and rosemary was synergistic for B. cinerea and P. expansum (FICi values of 0.5 and 0.375, respectively); while combination of cinnamon, marjoram and thyme exhibited additive and synergistic effect against P. expansum (FIC=0.625) and B. cinerea (FIC=0.375) respectively. The usage of a mathematical Gompertz model in relation to fungal kinetics, showed that the model could be used to predict growth curves (R²=0.993±0.05). For B. cinerea, Gompertz parameters for double and triple combination treatments showed significant increase in lag phase (1.92 and 2.92days, respectively) compared to single treatments. Increase lag time up to 2.82days (P<0.05) also observed in P. expansum treated by triple combination of EOs. Base on the results, the lowest maximum growth rate (0.37mm/day) was observed in B. cinerea treated by triple combination of thyme, cinnamon and rosemary. The in vivo test also demonstrated considerable inhibitory effects of EO combination treatments. Average lesion diameter of pears treated with triple combination of cinnamon/rosemary/thyme (78, 1250, 39μg/mL) was 6mm and 8mm against B. cinerea and P. expansum respectively, in 10days at 25°C. Results also showed that double combination of thyme/cinnamon (78, 156μg/mL) has more inhibitory effect than single EO treatments.

Innovative technologies to manage aflatoxins in foods and feeds and the profitability of application - A review

Aflatoxins are mainly produced by certain strains of Aspergillus flavus, which are found in diverse agricultural crops. In many lower-income countries, aflatoxins pose serious public health issues since the occurrence of these toxins can be considerably common and even extreme. Aflatoxins can negatively affect health of livestock and poultry due to contaminated feeds. Additionally, they significantly limit the development of international trade as a result of strict regulation in high-value markets. Due to their high stability, aflatoxins are not only a problem during cropping, but also during storage, transport, processing, and handling steps. Consequently, innovative evidence-based technologies are urgently required to minimize aflatoxin exposure. Thus far, biological control has been developed as the most innovative potential technology of controlling aflatoxin contamination in crops, which uses competitive exclusion of toxigenic strains by non-toxigenic ones. This technology is commercially applied in groundnuts maize, cottonseed, and pistachios during pre-harvest stages. Some other effective technologies such as irradiation, ozone fumigation, chemical and biological control agents, and improved packaging materials can also minimize post-harvest aflatoxins contamination in agricultural products. However, integrated adoption of these pre- and post-harvest technologies is still required for sustainable solutions to reduce aflatoxins contamination, which enhances food security, alleviates malnutrition, and strengthens economic sustainability.

4-Hydroxy-7-methyl-3-phenylcoumarin Suppresses Aflatoxin Biosynthesis via Downregulation of aflK Expressing Versicolorin B Synthase in Aspergillus flavus

Naturally occurring coumarins possess antibacterial and antifungal properties. In this study, these natural and synthetic coumarins were used to evaluate their antifungal activities against Aspergillus flavus, which produces aflatoxins. In addition to control antifungal activities, antiaflatoxigenic properties were also determined using a high-performance liquid chromatography in conjunction with fluorescence detection. In this study, 38 compounds tested and 4-hydroxy-7-methyl-3-phenyl coumarin showed potent antifungal and antiaflatoxigenic activities against A. flavus. Inhibitory mode of antiaflatoxigenic action by 4-hydroxy-7-methyl-3-phenyl coumarin was based on the downregulation of aflD, aflK, aflQ, and aflR in aflatoxin biosynthesis. In the cases of coumarins, antifungal and aflatoxigenic activities are highly related to the lack of diene moieties in the structures. In structurally related compounds, 2,3-dihydrobenzofuran exhibited antifungal and antiaflatoxigenic activities against A. flavus. The inhibitory mode of antiaflatoxigenic action by 2,3-dihydrobenzofuran was based on the inhibition of the transcription factor (aflS) in the aflatoxin biosynthesis pathway. These potent inhibitions of 2,3-dihydrobenzofuran and 4-hydroxy-7-methyl-3-phenyl coumarin on the Aspergillus growth and production of aflatoxins contribute to the development of new controlling agents to mitigate aflatoxin contamination.

Identification of the Anti-Aflatoxinogenic Activity of Micromeria graeca and Elucidation of Its Molecular Mechanism in Aspergillus flavus

Of all the food-contaminating mycotoxins, aflatoxins, and most notably aflatoxin B₁ (AFB₁), are found to be the most toxic and economically costly. Green farming is striving to replace fungicides and develop natural preventive strategies to minimize crop contamination by these toxic fungal metabolites. In this study, we demonstrated that an aqueous extract of the medicinal plant Micromeria graeca—known as hyssop—completely inhibits aflatoxin production by Aspergillus flavus without reducing fungal growth. The molecular inhibitory mechanism was explored by analyzing the expression of 61 genes, including 27 aflatoxin biosynthesis cluster genes and 34 secondary metabolism regulatory genes. This analysis revealed a three-fold down-regulation of aflR and aflS encoding the two internal cluster co-activators, resulting in a drastic repression of all aflatoxin biosynthesis genes. Hyssop also targeted fifteen regulatory genes, including veA and mtfA, two major global-regulating transcription factors. The effect of this extract is also linked to a transcriptomic variation of several genes required for the response to oxidative stress such as msnA, srrA, catA, cat2, sod1, mnsod, and stuA. In conclusion, hyssop inhibits AFB₁ synthesis at the transcriptomic level. This aqueous extract is a promising natural-based solution to control AFB₁ contamination.