Effect of essential oils on Aspergillus spore germination, growth and mycotoxin production: a potential source of botanical food preservative

The potential of antifungal peptides derived from Lactiplantibacillus plantarum WYH for biocontrol of Aspergillus flavus contamination

Aspergillus flavus is a notorious fungus that contaminates food crops with toxic aflatoxins, posing a serious threat to human health and the agricultural economy. To overcome the inadequacy of traditional control methods and meet consumer preferences for natural-sources additives, there is an urgent demand for novel biocontrol agents that are safe and efficient. This study aims to investigate the antifungal properties of a novel antifungal agent derived from the biologically safe Lactiplantibacillus plantarum WYH. Firstly, antifungal peptides (AFPs) with a molecular weight of less than 3kD, exhibiting remarkable temperature stability and effectively retarding fungal growth in a dose-dependent manner specifically against A. flavus, were concentrated from the fermentation supernatant of L. plantarum WYH and were named as AFPs-WYH. Further analysis demonstrated that AFPs-WYH might exert antifungal effects through the induction of oxidative stress, disruption of mitochondrial function, alteration of membrane permeability, and cell apoptosis in A. flavus. To further validate our findings, a transcriptomics analysis was conducted on A. flavus treated with 2 and 5 mg/mL of AFPs-WYH, which elucidated the potential effect of AFPs-WYH administration on the regulation of genes involved in impairing fungal development and preventing aflatoxin biosynthesis pathways. Overall, AFPs-WYH reduced the A. flavus proliferation and affected the AFB1 biosynthesis, exhibiting a promising potential for food industry applications as a biopreservative and biocontrol agent.

Genome analysis of Pseudomonas strain 4B with broad antagonistic activity against toxigenic fungi

Pseudomonas sp. 4B isolated from the effluent pond of a bovine abattoir was investigated as antifungal against toxigenic fungi. The complete genome of Pseudomonas 4B was sequenced using the Illumina MiSeq platform. Phylogenetic analysis and genome comparisons indicated that the strain belongs to the Pseudomonas aeruginosa group. In silico investigation revealed gene clusters associated with the biosynthesis of several antifungals, including pyocyanin, rhizomide, thanamycin, and pyochelin. This bacterium was investigated through antifungal assays, showing an inhibitory effect against all toxigenic fungi tested. Bacterial cells reduced the diameter of fungal colonies, colony growth rate, and sporulation of each indicator fungi in 10-day simultaneous growing tests. The co-incubation of bacterial suspension and fungal spores in yeast extract-sucrose broth for 48 h resulted in reduced spore germination. During simultaneous growth, decreased production of aflatoxin B1 and ochratoxin A by Aspergillus flavus and Aspergillus carbonarius, respectively, was observed. Genome analysis and in vitro studies showed the ability of P. aeruginosa 4B to reduce fungal growth parameters and mycotoxin levels, indicating the potential of this bacterium to control toxigenic fungi. The broad antifungal activity of this strain may represent a sustainable alternative for the exploration and subsequent use of its possible metabolites in order to control mycotoxin-producing fungi.

Antifungal Properties of Essential Oils Derived from the Genus Cymbopogon: A Systematic Review

Essential oils (EOs) are products of secondary metabolism with recognized organoleptic characteristics and biological properties. Recently, there has been a growing demand for EOs in the national and international market, mainly due to the recognition of their use as complementary medicine practices, and the increased use in the industries of pharmaceutics, cosmetics, well-being, veterinary and agroecology, boosting the productive sector. In this context, EOs from grasses of the Cymbopogon (Poaceae) are promising sources of bioactive compounds, due to their recognized biological properties, such as anti-inflammatory, antibacterial, antifungal, antidiabetic, repellent, and larvicide. Thus, the present study aims to carry out a review of the scientific literature of the main works related to the evaluation of the antifungal action of essential oils extracted from plants of the Cymbopogon genus, compiling the species that showed the best results and relating them to their main chemical constituents. This review covers the following species: C. citratus, C. flexuosus, C. winterianus, C. martinii, C. nardus, C. giganteus, C. schoenanthus, C. khasans, and C. proximus. Among them, C. citratus was the most assessed, being associated with the vast majority of studies (61.9 %), and it was also the species that showed the best results in terms of MIC.

Antifungal effects of selected menthol and eugenol in vapors on green coffee beans during long-term storage

Nowadays, coffee (Coffea Arabica L.) is among the most significant agricultural products of the world and drinking coffee has become one of the most popular habits in the world. The main contamination of stored coffee beans is related with the mycotoxin produced by the toxigenic fungi belonging the genus Aspergillus. Fungal infection followed by mycotoxin biosynthesis in coffee results in notable financial losses. subsequent mycotoxin biosynthesis in coffee leads to major economic losses. Complications ranging from mild to severe can be caused by the mycotoxins produced by this genus. The aim of this investigation was to determine the effect of menthol and eugenol on Aspergillus parasiticus (CBS 100926^T) growth, spore germination, and their potential use as green coffee beans preservative during long-term storage (12 months). The minimum inhibitory concentrations (MICs) values of the menthol and eugenol were recorded to completely inhibit the growth of A. parasiticus in 400 μg/ml and 300 μg/ml, respectively. Both reduced spore germination by 9.33% and 5.66% at 300 μg/ml and 200 μg/ml, respectively. They showed efficacy in fumigated green coffee beans sample during the storage for up to 12 months providing an increase in the protection level of 62.5% for menthol and 73.21% for eugenol against the A. parasiticus contamination. This suggests that menthol and eugenol could be used as good alternatives for decreasing the deteriorations due to the fungal infections in green coffee beans during long-term storage.

Antifungal Activity of Menthol, Eugenol and Their Combination against Aspergillus ochraceus and Aspergillus niger In Vitro and in Stored Cereals

Aspergillus ochraceus and Aspergillus niger are spoilage and mycotoxin-producing fungi that can contaminate agricultural commodities and derived products. In the present study, menthol, eugenol, and their combination (mix 1:1) were tested to determine their contact and fumigation toxicity against the two fungi. Menthol, eugenol, and their mixture significantly reduced mycelial growth and spore germination at concentrations from 300 to 600 µg/mL, and the inhibitory effects showed clear dose dependence. The minimum inhibitory concentration (MIC) values against A. ochraceus were 500 µg/mL (menthol), 400 µg/mL (eugenol), and 300 µg/mL (mix 1:1), while the MIC values for A. niger were 500 µg/mL (menthol), 600 µg/mL (eugenol), and 400 µg/mL (mix 1:1). Additionally, the analyzed compounds exhibited more than 50% protection against A. ochraceus and A. niger by fumigation of stored cereal grains (maize, barley, and rice) in sealed containers. The binary mixture of menthol and eugenol showed synergistic effects against both fungi in both in vitro direct contact and stored grain fumigation trials. The results of the present study provide a scientific basis for the application of a combination of natural antifungals in food preservation.

Simulated Microgravity Created Using a Random Positioning Machine Induces Changes in the Physiology of the Fusarium solani Species Complex

Fusarium is a phytopathogenic fungus involved in human pathology and is present in space stations. It is essential to understand the effects of microgravity on the physiology of this fungus to determine the potential risks to the health of crew members and to propose the necessary countermeasures. This study aimed to determine changes in the physiological parameters of the Fusarium solani species complex under simulated microgravity generated using a random positioning machine (RPM) and phenotypic approaches. We observed increased growth, spore production, and germination while biofilm production was reduced under RPM exposure. These in vitro data show the importance of further studying this fungus as it has been repeatedly demonstrated that microgravity weakens the immune system of astronauts.

Antifungal Role of Common Indian Spices & Herbs: A Narrative Review

Abstract:

A large variety of spices can be found in kitchens worldwide. The usage varies from region to region as per the cuisine. They hold nutritional values and are being exploited for their anticancer, antifungal, antibacterial, antiulcer, anti-inflammatory properties. This study highlights some of the commonly used Indian spices for their antifungal properties and summarizes their potential antifungal activity. Fungal diseases are deep-rooted and cause acute/chronic infections in humans, mainly Aspergillus and Candida species. As the tropical climate provides a breeding ground for fungal infections, such regions share a huge load of mycoses. Various spices have been shown to be effective against treating fungal diseases. The current study focuses on the potential anti-fungal role of the spices and reviews the current literature on the possible mechanism of action of the active compounds of these spices concerning the commonly used antifungal drugs. The spices consist of essential oils that work by inhibition mycotoxin biosynthesis, or disrupting and inhibiting cell wall formation and inhibiting efflux pumps and are comparable to the currently available antifungal drugs.

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.

A Design of Experiment (DoE) Approach to Model the Yield and Chemical Composition of Ajowan (Trachyspermum ammi L.) Essential Oil Obtained by Microwave-Assisted Extraction

Ajowan (Trachyspermum ammi L.) is a spice traditionally used in Middle Eastern medicine and contains a valuable essential oil (EO) exploited in different fields, such as pharmaceutics, agrochemicals and food additives. This EO is mostly characterized by the thymol to which most of its biological properties are related. Given the economic value of ajowan and its increasing demand across the globe, the extraction method used for its EO is of paramount importance in terms of quality and quantity of the final product. In the present study, we used the design of experiment (DoE) approach to study and optimize the extraction of the ajowan EO using the microwave-assisted extraction (MAE), a novel extraction technique with high efficiency, low energy consumption, short process length and low environmental impact. A two-step DoE (screening followed by surface response methodology) was used to reduce the number of experiments and to improve the cost/benefit ratio. Reliable mathematical models, relating the more relevant EO features with the extraction conditions, were obtained and used to identify the best experimental conditions able to maximize the yield and thymol concentration. The optimized MAE procedure assures an EO with a higher yield and thymol amount compared with the standard hydrodistillation procedure.

Actividad antifúngica in vitro del aceite esencial de Swinglea glutinosa Merr sobre Colletotrichum sp. patógeno de mango (Mangifera indica L.)

Se evaluó la actividad antifúngica del aceite esencial de limón de cerca (Swinglea glutinosa) sobre el hongo Colletotrichum sp. aislado de frutos de mango (Mangifera indica L). El aceite esencial, se obtuvo por hidrodestilación de hojas y corteza del fruto, y mediante cromatografía de gases acoplada a espectrometría de masas se determinó la fitoquímica. Se identificaron presuntivamente 41 metabolitos secundarios, siendo los compuestos mayoritarios β–pineno (31.3 %), α–pineno (15.1%) y germacreno D (14.4 %). El aceite esencial inhibió el crecimiento del hongo en un 31.16 %, 52.77 % y 82.41 % en ensayo de dilución en agar, a las concentraciones de 0.3, 1 y 2 % respectivamente, con diferencias entre todos los tratamientos evaluados (p=0.000). En ensayo de dilución en caldo se registró inhibición de la germinación de esporas de 0, 19.47, 41.03 y 100 % (p=0.000) a concentraciones de 0, 2, 4 y 8 µL/mL. Adicionalmente, en ensayo de microatmósfera se presentó una inhibición de máxima de 22,97 % del crecimiento micelial con adición de 20 µL de aceite esencial por caja de Petri (p=0.000). Este trabajo encontró que el aceite esencial de S. glutinosa ejerce inhibición dosis-dependiente sobre el crecimiento micelial y la germinación de esporas de Colletotrichum sp.

Volatiles and Antifungal-Antibacterial-Antiviral Activity of South African Salvia spp. Essential Oils Cultivated in Uniform Conditions

Spontaneous emissions of S. dentata Aiton and S. scabra Thunb., as well as the essential oil (EO) composition of the cited species, together with S. aurea L., were investigated. The chemical profile of the first two species is reported here for the first time. Moreover, in vitro tests were performed to evaluate the antifungal activity of these EOs on Trichophyton mentagrophytes, Microsporum canis, Aspergillus flavus, Aspergillus niger, and Fusarium solani. Secondly, the EO antibacterial activity against Escherichia coli, Staphylococcus aureus, and Staphylococcus pseudointermedius was examined, and their antiviral efficacy against the H1N1 influenza virus was assessed. Leaf volatile organic compounds (VOCs), as well as the EOs obtained from the arial part of Salvia scabra, were characterized by a high percentage of sesquiterpene hydrocarbons (97.8% and 76.6%, respectively), mostly represented by an equal amount of germacrene D (32.8% and 32.7%, respectively). Both leaf and flower spontaneous emissions of S. dentata, as well as the EO composition, showed a prevalence of monoterpenes divided into a more or less equal amount of hydrocarbon and oxygenated compounds. Interestingly, its EO had a non-negligible percentage of oxygenated sesquiterpenes (29.5%). S. aurea EO, on the contrary, was rich in sesquiterpenes, both hydrocarbons and oxygenated compounds (41.5% and 33.5%, respectively). S. dentata EO showed good efficacy (Minimal Inhibitory Concentration (MIC): 0.5%) against M. canis. The tested EOs were not active against E. coli and S. aureus, whereas a low inhibition of S. dentata EO was observed on S. pseudointermedius (MIC = 10%). Once again, S. dentata EO showed a very good H1N1 inhibition; contrariwise, S. aurea EO was completely inactive against this virus. The low quantity of S. scabra EO made it impossible to test its biological activity. S. dentata EO exhibited interesting new perspectives for medicinal and industrial uses.

Antifungal Activity of Essential Oil From Zanthoxylum armatum DC. on Aspergillus flavus and Aflatoxins in Stored Platycladi Semen

The major objective of this study was to evaluate the inhibitory effect of essential oil (EO) from Zanthoxylum armatum DC. on Aspergillus flavus. The chemical composition of the EO was identified by gas chromatography–mass spectrometer. The minimum inhibitory concentration (MIC) of EO was investigated by liquid fermentation. The morphology, colony number, and aflatoxin content of A. flavus in platycladi semen were investigated by stereomicroscopy, scanning electron microscopy, plate counting, and high-performance liquid chromatography. The results indicated that the MIC of EO was 0.8 μL⋅mL^–1, and the main components were β-phellandrene (7.53%), D-limonene (13.24%), linalool (41.73%), terpinen-4-ol (5.33%), and trans-nerolidol (6.30%). After the EO fumigated the platycladi semen, the growth of A. flavus slowed, and the mycelium shrank considerably. The number of colonies after EO treatment at room temperature and cold storage was significantly reduced, the inhibition effect was better under cold storage, and the aflatoxin B1 content did not exceed the standard within 100 days. Therefore, this study demonstrated the good potential of A. flavus growth inhibition during the storage of platycladi semen.

Characterisation of the antifungal effects of a plant-based compound, CIN-102, on the main septal filamentous fungi involved in human pathology

OBJECTIVES

Today, the increase of invasive fungal infections and the emergence of resistant strains are observed in medical practice. New antifungals are expected, and the plant world offers a panel of potentially active molecules. CIN-102 is a mixture of seven different compounds of plant origin developed from the formulation of cinnamon essential oil.

METHODS

The in vitro activity of CIN-102 was characterised against Aspergillus spp., Fusarium spp. and Scedosporium spp. by studying the minimum inhibitory concentration (MIC), inoculum effect, germination inhibition, fungal growth, post-antifungal effect (PAFE) and synergy.

RESULTS

MICs determined for the three genera followed a unimodal distribution and their mean values ranged from 62-250 μg/mL. CIN-102 demonstrated an inoculum effect similar to voriconazole and amphotericin B, 100% inhibition of spore germination and a PAFE.

CONCLUSION

CIN-102 has significant activity against filamentous fungi involved in human pathologies and should be further explored as a potential new treatment. Other studies regarding its mechanisms of action as well as animal investigations are awaited.

Recent advances on the efficacy of essential oils on mycotoxin secretion and their mode of action

Essential oils, as extracted compounds from plants, are volatile and aromatic liquids which their unique aromatic compounds give each essential oil its distinctive essence. Fungi toxins can induce various adverse health effects like allergy, cancer, and immunosuppression. Moreover, fungal spoilage impacts pharmaceutical and food industries economic state. A drop in the utilization of synthetic compounds as food prophylaxis has occurred due to several factors such as hygiene agents' alerts and stricter legal regulations. Therefore, the applications of natural substances such as essential oils have increased in recent years. Oregano, cinnamon, thyme, rosemary, fennel, clove, palmarosa, and eucalyptus have been the highest employed essential oils against mycotoxigenic fungi and their mycotoxins in studies conducted in the past decade. Essential oils inhibit fungi growth and mycotoxin synthesis via diverse pathways including modified fungal growth rate and extended lag phase, disruption of cell permeability, disruption of the electron transport chain and manipulating gene expression patterns and metabolic processes. In the present review, we will investigate the implications and efficacy of essential oils in preventing the growth of mycotoxigenic fungi, eliminating mycotoxins and their mechanism of actions conducted in the last decade. HighlightsThe most investigated toxigenic genera are Aspergillus, Fusarium and Penicillium Spp.AB1, AG1, OTA and AB2 are the most frequently studied toxinsOregano, cinnamon and thyme are mostly exploited EOs on toxigenic fungi & mycotoxinsOregano, thyme & cinnamon are the most significant antifungals on toxigenic generaCinnamon, oregano & cinnamaldehyde are the fittest antimycotoxins on DON, OTA & AFB1.

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

Aspergillus species are known to cause damage to food crops and are associated with opportunistic infections in humans. In the United States, significant losses have been reported in peanut production due to contamination caused by the Aspergillus species. This study evaluated the antifungal effect and anti-aflatoxin activity of selected plant-based essential oils (EOs) against Aspergillus flavus in contaminated peanuts, Tifguard, runner type variety. All fifteen essential oils, tested by the poisoned food technique, inhibited the growth of A. flavus at concentrations ranging between 125 and 4000 ppm. The most effective oils with total clearance of the A. flavus on agar were clove (500 ppm), thyme (1000 ppm), lemongrass, and cinnamon (2000 ppm) EOs. The gas chromatography-mass spectrometry (GC-MS) analysis of clove EO revealed eugenol (83.25%) as a major bioactive constituent. An electron microscopy study revealed that clove EO at 500 ppm caused noticeable morphological and ultrastructural alterations of the somatic and reproductive structures. Using both the ammonia vapor (AV) and coconut milk agar (CMA) methods, we not only detected the presence of an aflatoxigenic form of A. flavus in our contaminated peanuts, but we also observed that aflatoxin production was inhibited by clove EO at concentrations between 500 and 2000 ppm. In addition, we established a correlation between the concentration of clove EO and AFB1 production by reverse-phase high-performance liquid chromatography (HPLC). We demonstrate in our study that clove oil could be a promising natural fungicide for an effective bio-control, non-toxic bio-preservative, and an eco-friendly alternative to synthetic additives against A. flavus in Georgia peanuts.

A study on correlations between antimicrobial effects and diffusion coefficient, zeta potential and droplet size of essential oils

It was hypothesized that inhibition zone of an essential oil (EO) in a Petri dish might be relevant to its diffusion coefficient (DC) into agar medium, which may be calculated from the Fick’s diffusion. Antibacterial activities of cumin, dill weed, fennel, ginger and oregano EOs were evaluated against Campylobacter jejuni and Campylobacter coli. DCs, zeta potential and droplet sizes of EOs were measured. The inhibition zones of EOs had in accordance with DCs whereas they had a reverse relation with droplet size. The measured DCs were in the range of 0.82–1.50 × 10−12 m2 s−1. The effective DC of EOs calculated from the total flux exhibited good correlations with measured DCs. Outcomes of this study may provide a pre-assessment for the antimicrobial activity of any EOs from its DC. Furthermore, it may help to understand the studies on how EOs pass through a bacterium cell and show antimicrobial effects.

Assessing the antifungal and aflatoxin B1 inhibitory efficacy of nanoencapsulated antifungal formulation based on combination of Ocimum spp. essential oils

The aim of the study was to explore the antifungal and aflatoxin B₁ inhibitory efficacy of nanoencapsulated antifungal formulation. Mixture design response surface methodology (RSM) was utilized to design the antifungal formulation (SBC 4:1:1) based on the combination of chemically characterized Ocimum sanctum (S), O. basilicum (B), and O. canum (C) against Aspergillus flavus. The SBC was incorporated inside the chitosan nanomatrix (Ne-SBC) using an ultrasonic probe (40 kHz) and interactions were confirmed by SEM, FTIR and XRD analysis. The results showed that the Ne-SBC possessed enhanced antifungal and aflatoxin B₁ inhibitory effect over the free form of SBC. The biochemical and in silico results indicate that the antifungal and aflatoxin B₁ inhibitory effect was related to perturbance in the plasma membrane function (ergosterol biosynthesis and membrane cation) mitochondrial membrane potential, C-sources utilization, antioxidant defense system, and the targeted gene products Erg 28, cytochrome c oxidase subunit Va, and Nor-1. In-situ observation revealed that Ne-SBC effectively protects the Avena sativa seeds from A. flavus and AFB₁ contamination and preserves its sensory profile. The findings suggest that the fabrication of SBC inside the chitosan nano-matrix has promising use in the food industries as an antifungal agent.

Cardamom, Cumin, and Dill Weed Essential Oils: Chemical Compositions, Antimicrobial Activities, and Mechanisms of Action against Campylobacter spp

Natural antimicrobials as well as essential oils (EOs) have gained interest to inhibit pathogenic microorganisms and to control food borne diseases. Campylobacter spp. are one of the most common causative agents of gastroenteritis. In this study, cardamom, cumin, and dill weed EOs were evaluated for their antibacterial activities against Campylobacter jejuni and Campylobacter coli by using agar-well diffusion and broth microdilution methods, along with the mechanisms of antimicrobial action. Chemical compositions of EOs were also tested by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The results showed that cardamom and dill weed EOs possess greater antimicrobial activity than cumin with larger inhibition zones and lower minimum inhibitory concentrations. The permeability of cell membrane and cell membrane integrity were evaluated by determining relative electric conductivity and release of cell constituents into supernatant at 260 nm, respectively. Moreover, effect of EOs on the cell membrane of Campylobacter spp. was also investigated by measuring extracellular ATP concentration. Increase of relative electric conductivity, extracellular ATP concentration, and cell constituents' release after treatment with EOs demonstrated that tested EOs affected the membrane integrity of Campylobacter spp. The results supported high efficiency of cardamom, cumin, and dill weed EOs to inhibit Campylobacter spp. by impairing the bacterial cell membrane.

Evaluation of the Effect of Two Volatile Organic Compounds on Barley Pathogens

This study aimed to determine the effect of Volatile Organic Compounds (VOCs) on some pathogens, these VOCs were emitted during interactions of barley with Fusarium culmorum Schltdl and/or Cochliobolus sativus Shoemaker, two common root rot pathogens. Our work shows that two organic esters: methyl propanoate (MP) and methyl prop-2-enoate (MA) significantly reduced the development of fungi in vitro. Additional tests showed that the esters significantly inhibited spore germination of these pathogens. The activity of these VOCs on a wide range of fungal and bacterial pathogens was also tested in vitro and showed inhibitory action. The effect of the VOCs on infected barley seeds also showed plantlets growing without disease symptoms. MA and MP seem to have potential value as alternative plant protection compounds against barley bioagressors.

Inhibition of mycotoxin-producing fungi by Bacillus strains isolated from fish intestines

Bacillus strains isolated from the aquatic environment of the Brazilian Amazon region were tested for their activity against mycotoxigenic fungi. All tested bacteria showed antifungal activity, inhibiting at least 7 indicator fungi. Four Bacillus strains showing promising antifungal results were subsequently evaluated for their activity in reducing mycelial growth rate, sporulation, spore germination percentage, and mycotoxin production. Bacillus sp. P1 and Bacillus sp. P11 had a remarkable antifungal effect on toxigenic fungi. Washed bacterial cell suspension of strains P1 and P11 (10⁷CFU/ml) reduced by >70% the fungal colony diameters, including a complete inhibition of ochratoxin A (OTA) producing Aspergillus spp. Significant reduction of growth rate, sporulation and spore germination were also observed. The bacteria influenced the production of mycotoxins, causing a reduction around 99 and 97% in AFB1 and OTA concentration, respectively. Chromatographic analysis revealed the presence of lipopeptides (iturin A and surfactin isomers) in butanol extracts of cell-free supernatants and cell pellets of strains P1 and P11. Furthermore, antifungal activity of these extracts was confirmed against A. flavus A12 and A. carbonarius ITAL293, producers of AFB1 and OTA, respectively. These bacterial strains could be promising biocontrol agents against toxigenic fungi.

Thymol-based submicron emulsions exhibit antifungal activity against Fusarium graminearum and inhibit Fusarium head blight in wheat

AIMS

Fusarium graminearum is a very destructive fungal pathogen that leads to Fusarium head blight (FHB) in wheat, a disease which costs growers millions of dollars annually both in crop losses and in remediation efforts. Current countermeasures include the deployment of wheat varieties with some resistance to FHB in conjunction with timed fungicide treatments. In this article, we introduce a fungicide based on thymol, a naturally occurring plant phenolic derived from essential oils. To overcome the hydrophobicity of thymol, the thymol active was incorporated into a low-surfactant submicron emulsion with and without a carrier oil.

METHODS AND RESULTS

The minimum fungicidal concentration of F. graminearum was found to be both 0·02% for thymol emulsions with and without an oil component. Time-to-kill experiments showed that thymol emulsions were able to inactivate F. graminearum in as little as 10 s at concentrations above 0·06%. Spraying the thymol emulsions (~0·1% range) on the wheat variety Bobwhite demonstrated significant reductions in FHB infection rate (number of infected spikelets). However, with 0·5% thymol, the wheat heads exhibited premature senescence. Transmission and scanning electron micrographs suggest that the mechanism of antifungal action is membrane mediated, as conidia exposed to thymol showed complete organelle disorganization and evidence of lipid emulsification.

CONCLUSION

The collective experimental data suggest that thymol emulsions may be an effective naturally derived alternative to the current thymol treatments, and chemical fungicides in ameliorating FHB.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first thymol-derived nanoemulsion particles resuspended into water and not DMSO, exhibiting the same antibacterial/antifungal activity as previously described thymol and thyme oil treatments. This drastically reduces the environmental footprint thymol will leave if utilized as a fungicide treatment on field crops.

In vitro effect of seven essential oils on the reproduction of the cattle tick Rhipicephalus microplus

The acaricidal effect of seven essential oils was examined in vitro against the cattle tick (Rhipicephalus microplus). Engorged female ticks were manually collected in farms of Southern Brazil and placed into petri dishes (n = 10) in order to test the following oils: juniper (Juniperus communis), palmarosa (Cymbopogon martinii), cedar (Cedrus atlantica), lemon grass (Cymbopogon citratus), ginger (Zingiber officinale), geranium (Pelargonium graveolens) and bergamot (Citrus aurantium var bergamia) at concentrations of 1%, 5%, and 10% each. A control group was used to validate the tests containing Triton X-100 only. Treatment effectiveness was measured considering inhibition of tick oviposition (partial or total), egg’s weight, and hatchability. C. martinii, C. citratus and C. atlantica essential oils showed efficacy higher than 99% at all concentrations tested. In addition, J. communis, Z. officinale, P. graveolens, and C. aurantium var bergamia oils showed efficiency ranging from 73% to 95%, depending on the concentration tested, where higher concentrations showed greater efficacy. It was concluded that essential oils can affect tick reproduction in vitro by inhibiting oviposition and hatchability.

Structural Elucidation and Toxicity Assessment of Degraded Products of Aflatoxin B1 and B2 by Aqueous Extracts of Trachyspermum ammi

In this study aqueous extract of seeds and leaves of Trachyspermum ammi were evaluated for their ability to detoxify aflatoxin B1 and B2 (AFB1; 100 μg L(-1) and AFB2; 50 μg L(-1)) by in vitro and in vivo assays. Results indicated that T. ammi seeds extract was found to be significant (P < 0.05) in degrading AFB1 and AFB2 i.e., 92.8 and 91.9% respectively. However, T. ammi leaves extract proved to be less efficient in degrading these aflatoxins, under optimized conditions i.e., pH 8, temperature 30°C and incubation period of 72 h. The structural elucidation of degraded toxin products by LCMS/MS analysis showed that eight degraded products of AFB1 and AFB2 were formed. MS/MS spectra showed that most of the products were formed by the removal of double bond in the terminal furan ring and modification of lactone group indicating less toxicity as compared to parent compounds. Brine shrimps bioassay further confirmed the low toxicity of degraded products, showing that T. ammi seeds extract can be used as an effective tool for the detoxification of aflatoxins.

Combating pathogenic microorganisms using plant-derived antimicrobials: a minireview of the mechanistic basis

The emergence of antibiotic resistance in pathogenic bacteria has led to renewed interest in exploring the potential of plant-derived antimicrobials (PDAs) as an alternative therapeutic strategy to combat microbial infections. Historically, plant extracts have been used as a safe, effective, and natural remedy for ailments and diseases in traditional medicine. Extensive research in the last two decades has identified a plethora of PDAs with a wide spectrum of activity against a variety of fungal and bacterial pathogens causing infections in humans and animals. Active components of many plant extracts have been characterized and are commercially available; however, research delineating the mechanistic basis of their antimicrobial action is scanty. This review highlights the potential of various plant-derived compounds to control pathogenic bacteria, especially the diverse effects exerted by plant compounds on various virulence factors that are critical for pathogenicity inside the host. In addition, the potential effect of PDAs on gut microbiota is discussed.