Investigation of the Antifungal and Anti-Aflatoxigenic Potential of Plant-Based Essential Oils against Aspergillus flavus in Peanuts

Antifungal Activity of Cyperus articulatus, Cyperus rotundus and Lippia alba Essential Oils against Aspergillus flavus Isolated from Peanut Seeds

Aspergillus flavus is a cosmopolitan saprophytic fungus that infests several foodstuffs and is associated with adverse effects in humans. In Senegal, significant losses of groundnut production are mainly due to contamination caused by this species. This study evaluated in vitro antifungal activities of Cyperus articulatus, Cyperus rotundus and Lippia alba essential oils against A. flavus isolated from peanut seeds. Essential oils obtained by hydrodistillation of rhizomes of the two Cyperus species and leaves of L. alba were analyzed with GC-DIF and GC-MS. The essential oil yields from C. articulatus, C. rotundus and L. alba were 1.1%, 1.3% and 1.7%, respectively. These three samples had the following chemotypes: (i) mustakone (21.4%)/eudesma-4(15)-7-dien-1β-ol (8.8%)/caryophyllene oxide (5.9%), (ii) caryophyllene oxide (25.2%)/humulene epoxyde 2 (35.0%) and (iii) geranial (46.6%)/neral (34.6%). The three oils tested inhibited the growth of A. flavus at concentrations between 100 and 1000 ppm. The L. alba oil was the most effective with total clearance of A. flavus on PDA. For the essential oils of C. rotundus (93.65%) and C. articulatus (78.11%), the highest inhibition rates were obtained with a 1000 ppm dose. Thus, L. alba oil could be used safely as an effective protector of groundnuts against A. flavus.

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.

The performance of plant essential oils against lactic acid bacteria and adverse microorganisms in silage production

Plant essential oils have played an important role in the field of antibiotic alternatives because of their efficient bacteriostatic and fungistatic activity. As plant essential oils are widely used, their activity to improve the quality of plant silage has also been explored. This review expounds on the active ingredients of essential oils, their bacteriostatic and fungistatic activity, and mechanisms, as well as discusses the application of plant essential oils in plant silage fermentation, to provide a reference for the development and application of plant essential oils as silage additives in plant silage fermentation feed.

Estragole Inhibits Growth and Aflatoxin Biosynthesis of Aspergillus flavus by Affecting Reactive Oxygen Species Homeostasis

A variety of essential oils and edible compounds have been widely recognized for their antifungal activity in recent years. In this study, we explored the antifungal activity of estragole from Pimenta racemosa against Aspergillus flavus and investigated the underlying mechanism of action. The results showed that estragole had significant antifungal activity against A. flavus, with a minimum inhibitory concentration of 0.5 μL/mL against spore germination. Additionally, estragole inhibited the biosynthesis of aflatoxin in a dose-dependent manner, and aflatoxin biosynthesis was significantly inhibited at 0.125 μL/mL. Pathogenicity assays showed that estragole had potential antifungal activity against A. flavus in peanut and corn grains by inhibiting conidia and aflatoxin production. Transcriptomic analysis showed that the differentially expressed genes (DEGs) were mainly related to oxidative stress, energy metabolism, and secondary metabolite synthesis following estragole treatment. Importantly, we experimentally verified reactive oxidative species accumulation following downregulation of antioxidant enzymes, including catalase, superoxide dismutase, and peroxidase. These results suggest that estragole inhibits the growth and aflatoxin biosynthesis of A. flavus by modulating intracellular redox homeostasis. These findings expand our knowledge on the antifungal activity and molecular mechanisms of estragole, and provide a basis for estragole as a potential agent against A. flavus contamination. IMPORTANCE Aspergillus flavus contaminates crops and produces aflatoxins, carcinogenic secondary metabolites which pose a serious threat to agricultural production and animal and human health. Currently, control of A. flavus growth and mycotoxin contamination mainly relies on antimicrobial chemicals, agents with side effects such as toxic residues and the emergence of resistance. With their safety, environmental friendliness, and high efficiency, essential oils and edible compounds have become promising antifungal agents to control growth and mycotoxin biosynthesis in hazardous filamentous fungi. In this study, we explored the antifungal activity of estragole from Pimenta racemosa against A. flavus and investigated its underlying mechanism. The results demonstrated that estragole inhibits the growth and aflatoxin biosynthesis of A. flavus by modulating intracellular redox homeostasis.

Effects and mechanisms of plant bioactive compounds in preventing fungal spoilage and mycotoxin contamination in postharvest fruits: A review

Spoilage and mycotoxin contamination of fruits cause significant economic losses and food safety issues. Synthetic chemical fungicide treatment as primary postharvest management has attracted increasing public concern in recent years, because it may cause negative effects on the environment and human health. Numerous bioactive compounds from plants have demonstrated excellent control effects on fruit spoilage and mycotoxin contamination. Plant bioactive compounds have been considered one of the most promising alternatives, because they are generally regarded as safe and environmentally friendly. Here, we reviewed the most recent advances in plant bioactive compounds in the prevention of fungal spoilage and mycotoxin contamination in fruits. The control effects of these compounds and the mechanisms involved were summarized, and current limitations and future perspectives were discussed.

Preparation and application of cinnamon-Litsea cubeba compound essential oil microcapsules for peanut kernel postharvest storage

This research developed a novel, efficient and safe antimildew for peanut kernel postharvest storage. The antimildew, cinnamon-Litsea cubeba compound essential oil (CLCEO) microcapsule (CLCEOM), was synthesized with CLCEO as core materials and β-cyclodextrin as wall materials. Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry analyses indicated that major antifungal compounds of CLCEO were encapsulated in the cavity of β-cyclodextrin. The inhibition zone experiment showed that CLCEOM retained antifungal effect on Aspergillus spp. strains even after storage for 2 months at 4 ℃. Besides, CLCEOM reduced total number of fungal colonies, relative abundance of Aspergillus spp., and aflatoxin B₁ content of peanut kernels, and had positive effect on slowing down the increase in acid value of peanut oil without causing any adverse effect on the viability and sensory properties during storage process. Overall, CLCEOM presented good preservative effects on peanut kernels, providing evidence for its potential use as antimildew for peanut storage.

Antifungal activity of probiotic strain Lactiplantibacillus plantarum MYSN7 against Trichophyton tonsurans

The primary objective of this study was to assess the probiotic attributes and antifungal activity of lactic acid bacteria (LAB) against the fungus, Trichophyton tonsurans. Among the 20 isolates screened for their antifungal attributes, isolate MYSN7 showed strong antifungal activity and was selected for further analysis. The isolate MYSN7 exhibited potential probiotic characteristics, having 75 and 70% survival percentages in pH3 and pH2, respectively, 68.73% tolerance to bile, a moderate cell surface hydrophobicity of 48.87%, and an auto-aggregation percentage of 80.62%. The cell-free supernatant (CFS) of MYSN7 also showed effective antibacterial activity against common pathogens. Furthermore, the isolate MYSN7 was identified as Lactiplantibacillus plantarum by 16S rRNA sequencing. Both L. plantarum MYSN7 and its CFS exhibited significant anti-Trichophyton activity in which the biomass of the fungal pathogen was negligible after 14 days of incubation with the active cells of probiotic culture (10⁶ CFU/ml) and at 6% concentration of the CFS. In addition, the CFS inhibited the germination of conidia even after 72 h of incubation. The minimum inhibitory concentration of the lyophilized crude extract of the CFS was observed to be 8 mg/ml. Preliminary characterization of the CFS showed that the active component would be organic acids in nature responsible for antifungal activity. Organic acid profiling of the CFS using LC-MS revealed that it was a mixture of 11 different acids, and among these, succinic acid (9,793.60 μg/ml) and lactic acid (2,077.86 μg/ml) were predominant. Additionally, a scanning electron microscopic study revealed that CFS disrupted fungal hyphal structure significantly, which showed scanty branching and bulged terminus. The study indicates the potential of L. plantarum MYSN7 and its CFS to control the growth of T. tonsurans. Furthermore, in vivo studies need to be conducted to explore its possible applications on skin infections.

Comparing the effects of essential oils and methanolic extracts on the inhibition of Aspergillus flavus and Aspergillus parasiticus growth and production of aflatoxins

The antifungal and antiaflatoxigenic effects of four distinct plant species against Aspergillus flavus and Aspergillus parasiticus were investigated. Essential oils and methanolic extracts were prepared from aerial parts of Lippia javanica, Ocimum gratissimum, Satureja punctata, and stem barks of Toddalia asiatica by hydro-distillation and maceration, respectively. The poisoned food method was used to confirm the antifungal activity of essential oils and methanolic extracts from four different plant species against Aspergillus flavus and Aspergillus parasiticus, and high-performance liquid chromatography was used to quantify the antiaflatoxigenic activity. The essential oils of Satureja punctata and Lippia javanica showed the highest antiaflatoxigenic activity against the fungi strains tested at concentrations of 1.25, 2.5, and 5 µL/mL, followed by Ocimum gratissimum essential oil while Toddalia asiatica essential oil exerted moderate antiaflatoxigenic activity. Meanwhile, the methanolic extracts showed a wide spectrum of low to high antifungal and antiaflatoxigenic activities at concentrations of 125, 250, and 500 µg/mL against A. flavus and A. parasiticus. This study has indicated that the essential oils of Satureja punctate, Lippia javanica, and Ocimum gratissimum had substantial antifungal and antiaflatoxigenic activities compared to their methanolic extracts, while Toddalia asiatica methanolic extract had a moderate antifungal activity compared to its essential oil.

Phenolic-Rich Extracts from Circular Economy: Chemical Profile and Activity against Filamentous Fungi and Dermatophytes

Fungal infections represent a relevant issue in agri-food and biomedical fields because they could compromise quality of food and humans' health. Natural extracts represent a safe alternative to synthetic fungicides and in the green chemistry and circular economy scenario, agro-industrial wastes and by-products offer an eco-friendly source of bioactive natural compounds. In this paper, phenolic-rich extracts from Olea europaea L. de-oiled pomace, Castanea sativa Mill. wood, Punica granatum L. peel, and Vitis vinifera L. pomace and seeds were characterized by HPLC-MS-DAD analysis. Finally, these extracts were tested as antimicrobial agents against pathogenic filamentous fungi and dermatophytes such as Aspergillus brasiliensis, Alternaria sp., Rhizopus stolonifer, and Trichophyton interdigitale. The experimental results evidenced that all extracts exhibited a significant growth inhibition for Trichophyton interdigitale. Punica granatum L., Castanea sativa Mill., and Vitis vinifera L. extracts showed a high activity against Alternaria sp. and Rhizopus stolonifer. These data are promising for the potential applications of some of these extracts as antifungal agents in the food and biomedical fields.

A Review of Regulatory Standards and Advances in Essential Oils as Antimicrobials in Foods

As essential oils (EOs) possess GRAS status, there is a strong interest in their application to food preservation. Trends in the food industry suggest consumers are drawn to environmentally friendly alternatives and less synthetic chemical preservatives. Although the use of EOs has increased over the years, adverse effects have limited their use. This review aims to address the regulatory standards for EO usage in food, techniques for delivery of EOs, essential oils commonly used to control pathogens and molds, and advances with new active compounds that overcome sensory effects for meat products, fresh fruits and vegetables, fruit and vegetable juices, seafood, dairy products, and other products. This review will show adverse sensory effects can be overcome in various products by the use of edible coatings containing encapsulated EOs to facilitate the controlled release of EOs. Depending on the method of cooking, the food product has been shown to mask flavors associated with EOs. In addition, using active packaging materials can decrease the diffusion rate of the EOs, thus controlling undesirable flavor characteristics while still preserving or prolonging the shelf life of food. The use of encapsulation in packaging film can control the release of volatile or active ingredients. Further, use of EOs in the vapor phase allows for contact indirectly, and use of nanoemulsion, coating, and film wrap allows for the controlled release of the EOs. Research has also shown that combining EOs can prevent adverse sensory effects. Essential oils continue to serve as a very beneficial way of controlling undesirable microorganisms in food systems.

Recent advances in nutritional composition, phytochemistry, bioactive, and potential applications of Syzygium aromaticum L. (Myrtaceae)

Syzygium aromaticum is an aromatic plant native to Indonesia, and introduced to tropical regions worldwide. As an ingredient in perfumes, lotions, and food preservation, it is widely used in the food and cosmetic industries. Also, it is used to treat toothache, ulcers, type 2 diabetes, etc. A variety of nutrients such as amino acids, proteins, fatty acids, and vitamins are found in S. aromaticum. In addition to eugenol, isoeugenol, eugenol acetate, β-caryophyllene and α-humulene are the main chemical constituents. The chemical constituents of S. aromaticum exhibit a wide range of bioactivities, such as antioxidant, antitumor, hypoglycemic, immunomodulatory, analgesic, neuroprotective, anti-obesity, antiulcer, etc. This review aims to comprehend the information on its taxonomy and botany, nutritional composition, chemical composition, bioactivities and their mechanisms, toxicity, and potential applications. This review will be a comprehensive scientific resource for those interested in pursuing further research to explore its value in food.

Antifungal Activities of Essential Oils in Vapor Phase against Botrytis cinerea and Their Potential to Control Postharvest Strawberry Gray Mold

Essential oils (EOs) from aromatic plants seem to have the potential to control several fungal pathogens and food contaminants. Botrytis cinerea is the main strawberry fruit contaminant causing high losses during storage. Here, thirteen EOs applied in the vapor phase were evaluated for their potential to inhibit the growth of three different strains of B. cinerea isolated from strawberry fruits. Eight EOs (lemongrass, litsea, lavender, peppermint, mint, petitgrain, sage, and thyme) were able to completely inhibit the growth of B. cinerea for 7 days when applied at a concentration of 625 μL·L⁻¹. Four EOs with the lowest minimal inhibition concentrations (thyme, peppermint, lemongrass, and litsea) have been tested on strawberry fruits intentionally inoculated by B. cinerea. All four EOs showed high inhibition at a concentration of 250 or 500 μL·L⁻¹, but only peppermint EO was able to completely inhibit B. cinerea lesion development at a concentration of 125 μL·L⁻¹. The sensory evaluation of strawberries treated by EOs at a concentration 125 μL·L⁻¹ resulted in a statistically significant decrease in taste, aftertaste, aroma, and overall quality. Lemongrass and litsea EOs scored better than thyme and peppermint ones, thus forming two viable methods for B. cinerea suppression and the extension of packed strawberries’ shelf life.

Prevention of Aflatoxin Occurrence Using Nuts-Edible Coating of Ginger Oil Nanoemulsions and Investigate the Molecular Docking Strategy

The modern utilization of essential oils such as ginger oil (GO) as an anti-aflatoxin represents a potential target for food preservation and safety; however, the mechanism of action is still unclear. Nanoemulsions, through an edible coating, can enhance the oil’s bioactivity, increase its hydrophilicity, and extend the final product’s shelf-life. In the present study, two edible films for the GO nanoemulsion were prepared by ultrasonication using carboxymethyl cellulose (FB1-GO) and sodium alginate (FB2-GO). The droplet size of FB2-GO was finer (126.54 nm) compared to FB1-GO (289.77 nm). Meanwhile, both had high stability proved by z-potential; +31.54 mV (FB1-GO) and +46.25 mV (FB2-GO) with low PDI values (<0.4). Using gas chromatography-mass spectrometry, the hydrodistilled GO showed 25 compounds, representing 99.17% of the total oil, with α-zingiberene (29.8%), geranial (10.87%), β-bisabolene (8.19%), and ar-curcumene (5.96%) as the predominant. A dramatic increase in α-zingiberene, α-bisabolene and ar-curcumene was due to the homogenization conditions in both FB1-GO and FB2-GO compared to the GO. The FB1-GO exhibited superior antibacterial activity against the examined strains of bacterial pathogens, while FB2-GO was more effective as an antifungal agent on the tested Aspergillus fungi strains. In a simulated liquid media, FB2-GO inhibited the total growth of fungi by 84.87−92.51% and showed the highest reduction in the aflatoxin amount produced. The in silico study presented that, among the GO volatile constituents, sesquiterpenes had the highest binding free energies against the enzymes responsible for aflatoxin production compared to monoterpenes. α-Bisabolene showed the highest affinity toward polyketide synthase (−7.5 Kcal/mol), while ar-curcumene was the most potent against cytochrome P450 monooxygenase (−8.3 Kcal/mol). The above findings clarify the reasons for aflatoxin reduction in simulated media during incubation with FB1-GO and FB2-GO.

Antifungal and antimycotoxic activities of 3 essential oils against 3 mycotoxinogenic fungi

Fungal toxins can have various adverse health effects, including carcinogenic, teratogenic or hepatotoxic impacts. In addition, fungal alteration has also a negative impact on agricultural plant production. The use of chemical fungicides to control mycotoxin contamination is increasingly controversial and regulated. More environmentally friendly methods are therefore being explored. Essential oils, as compounds extracted from plants, are liquids whose specific aromatic compounds give each essential oil its own unique characteristics. Due to their rich chemical composition, essential oils (EOs) have many interesting properties, including antifungal activities. The objective of the present study was to analyze volatile chemical composition of EOs (Cymbopogon schoenanthus, Cymbopogon nardus and Eucalyptus camaldulensis) by GC/MS and to investigate their effects on the growth, sporulation and mycotoxin production of Aspergillus flavus, Aspergillus carbonarius and Fusarium verticillioides (aflatoxin B1, ochratoxin A and fumonisin B1, respectively). In addition, EOs influence on aflatoxin B1 (AFB1) and fumonisin B1 (FB1) biosynthesis pathways was explored using real-time qRT-PCR. The results obtained in vitro, by direct contact with the EOs and by diffusion of their volatile compounds, showed that the essential oils had inhibitory effects on the growth and the production of mycotoxins of the 3 fungal strains and modified the expression of some toxin synthesis genes. We conclude that the recorded effects were dependent on the combined effects of the EOs type, the fungal strains and the doses studied.

The Antifungal Activity of Cinnamon-Litsea Combined Essential Oil against Dominant Fungal Strains of Moldy Peanut Kernels

The antifungal activity of cinnamon (Cinnamomum cassia Presl), litsea [Litsea cubeba (Lour.) Pers.], clove (Syzygium aromaticum L.), thyme (Thymus mongolicus Ronn.) and citronella (Cymbopogon winterianus Jowitt) essential oils (EOs) against the dominant fungi isolated from moldy peanuts was investigated in this research. Firstly, strain YQM was isolated and identified by morphological characterization and 18S rRNA gene sequence analysis to be Aspergillus flavus (A. flavus). Next, antifungal effects of single or mixed EOs on strain YQM were evaluated by the inhibition zone test. The cinnamon-litsea combined essential oil (CLCEO, V_{cinnamon oil}:V_{litsea oil} = 3:5) displayed the best antifungal effect on strain YQM. The chemical composition of CLCEO was identified and quantified by gas chromatograph-mass spectrometry (GC-MS), and results revealed that the major components of CLCEO were cinnamaldehyde and citral. Finally, the effect of EOs on the microstructure of strain YQM mycelia was observed under scanning electron microscope (SEM). The mycelia exposed to cinnamon essential oil (CEO) and litsea essential oil (LEO) were partly deformed and collapsed, while the mycelia treated with CLCEO were seriously damaged and the deformation phenomena such as shrinking, shriveling and sinking occurred. Therefore, CLCEO has great potential for using as anti-mildew agents during peanut storage.

Therapeutic Potential of Green Synthesized Gold Nanoparticles Using Extract of Leptadenia hastata against Invasive Pulmonary Aspergillosis

Gold nanoparticles are widely used in the biomedical field for the treatment of several diseases, including cancer, inflammatory diseases, and immune system disorders, due to their distinctive physicochemical characteristics. In this study, we investigated the therapeutic potential of green synthesized gold nanoparticles using ethanolic leaf extract of Leptadenia hastata (LH-AuNPs) against invasive pulmonary aspergillosis (IPA) in mice. UV/visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and zeta potential were used to characterize the biofabricated LH-AuNPs. Antifungal activity of LH-AuNPs was determined by MTT assay, (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide), time-kill assay, and radial growth inhibition. TEM and SEM were used to examine the mode of the antifungal action of LH-AuNPs. The in vivo activity of LH-AuNPs against IPA was studied using a well-established IPA mouse model. LH-AuNPs excreted antifungal activity against Aspergillus fumigatus with MIC 64 µg/mL and inhibited the radial growth of A. fumigatus by 30% compared to the control. LH-AuNPs caused distortion and collapse of fungal hyphae and deterioration of cell walls. Interestingly, LH-AuNPs did not display any cytotoxicity on cultured primary bone marrow stem cells (BMSCs) or A549 human lung cell line in vitro at MIC concentration. IPA mice treated with LH-AuNPs displayed significant lung tissue repair without any in vivo cytotoxicity. LH-AuNPs administration showed significant suppression of fungal burden and gliotoxin production in the lung. In addition, LH-AuNPs inhibited IPA-induced pro-inflammatory cytokines production, including interleukin-1 (IL-1), interleukin-17 (IL-17), and tumor necrosis factor-alpha (TNF-α), and reduced oxidative stress in lung. In conclusion, our data provide LH-AuNPs as a novel nanoparticle therapy for IPA.

Uncovering the Industrial Potentials of Lemongrass Essential Oil as a Food Preservative: A Review

The food industry is growing vastly, with an increasing number of food products and the demand of consumers to have safe and pathogen-free food with an extended shelf life for consumption. It is critical to have food safe from pathogenic bacteria, fungi, and unpleasant odors or tastes so that the food may not cause any health risks to consumers. Currently, the direction of food industry has been shifting from synthetically produced preservatives to natural preservatives to lower the unnecessary chemical burden on health. Many new technologies are working on natural prevention tools against food degradation. Lemongrass is one such natural preservative that possesses significant antimicrobial and antioxidant activity. The essential oil of lemongrass contains a series of terpenes that are responsible for these activities. These properties make lemongrass acceptable in the food industry and may fulfill consumer demands. This article provides detailed information about the role of lemongrass and its essential oil in food preservation. The outcomes of the research on lemongrass offer room for its new technological applications in food preservation.

Antifungal and synergistic activities of some selected essential oils on the growth of significant indoor fungi of the genus Aspergillus

The study aimed to assess the antifungal activity of twenty-five essential oils (EOs) and the potential synergistic activity of the most effective EOs against significant indoor fungi of the genus Aspergillus [A. fumigatus (KBio-122), A. flavus (KBio-134), A. terreus (KBio-145) and A. niger (KBio-202)]. The chemical composition of all EOs was evaluated by the gas chromatography coupled with mass spectrometry (GC/MS) and gas chromatography with flame ionization detector (GC-FID) analysis. The antifungal susceptibility of EOs was evaluated by using the broth microdilution method. The most effective EOs were selected to determine the minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) at a concentration range from 256 to 0.125 μg/mL. For the synergistic activities, the most effective EOs were tested using the chessboard pattern. The most sensitive strain to treatments with essential oils alone and in the combination of EOs was A. flavus (KBio-134). The chessboard assay showed that combinations of lemongrass and thyme EOs proved the most potent synergistic antifungal activity (FICI = 0.1875) against A. fumigatus (KBio-122). The synergy displayed by a combination of some EOs may be used to control fungal growth or increasing resistance to available synthetic antifungals, consequently permitting the reduction of their most active doses.