Antifungal effects of the bioactive compounds enniatins A, A(1), B, B(1)

Isolation and Characterization of Fungal Endophytes From Helichrysum oocephalum, Evaluating Their Antimicrobial Activities, and Annotation of Their Metabolites

Antibiotic resistance is one of the biggest threats to global health. Fungal endophytes are important sources of active natural products with antimicrobial potential. The purpose of this study was to characterize the endophytes coexisting with Helichrysum oocephalum, evaluate their antimicrobial activities, and annotate the endophytes metabolites. Six fungal species, including Fusarium avenaceum and Fusarium tricinctum, were identified. Endophytes were cultured, and their metabolites were extracted. The antimicrobial effects of the extracts were tested against Staphylococcus aureus, Bacillus cereus, Staphylococcus epidermidis, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans. In addition, anti-biofilm effects of the extracts were examined against P. aeruginosa and S. epidermidis. The metabolites in the most active extract were annotated on the basis of the LC-ESI-QToF-MS/MS data. In anti-biofilm studies, F. avenaceum extract was effective in destroying and inhibiting the biofilm formation of S. epidermidis. LC-MS analysis showed that most of the identified compounds in the active extracts were enniatins (cyclic hexadepsipeptides). However, apicidin derivatives were also annotated. Our results revealed that these endophytes, especially Fusarium species, have antimicrobial activity against S. aureus, B. cereus, and C. albicans and anti-biofilm activity against S. epidermidis. According to the literature, the observed antimicrobial activity can be attributed to the enniatins. However, further phytochemical and pharmacological studies are necessary in this regard.

Fusarium begoniae metabolites: a promising larvicidal, pupicidal potential, histopathological alterations and detoxifications enzyme profiles of medically important mosquito vector Aedes aegypti, Culex quinquefasciatus and Anopheles stephensi

Endophytic fungal molecules have the potential to be a cost-effective chemical source for developing eco-friendly disease-controlling pharmaceuticals that target mosquito-borne illnesses. The primary aims of the study were to identify the fungus Fusarium begoniae larvicidal ability against Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi. The ethyl acetate extract demonstrated lethal concentrations that kill 50% of exposed larvae (LC50) and 90% of exposed larvae (LC90) for the 1st to 4th instar larvae of An. stephensi (LC50 = 54.821, 66.525, 68.250, and 73.614; LC90 = 104.56, 138.205, 150.415, and 159.466 μg/mL), Cx. quinquefasciatus (LC50 = 64.981, 36.505, 42.230, and 36.514; LC90 = 180.46, 157.105, 140.318, and 153.366 μg/ mL), and Ae. aegypti (LC50 = 74.890, 33.607, 52.173, and 26.974; LC90 = 202.56, 162.205, 130.518, and 163.286 μg/mL). Mycelium metabolites were evaluated for their pupicidal activity towards Ae. aegypti (LC50 = 80.669, LC90 = 119.904), Cx. quinquefasciatus (LC50 = 70.569, LC90 = 109.840), and An. stephensi (LC50 = 73.269, LC90 = 110.590 μg/mL). The highest larvicidal activity was recorded at 300 µg/mL, with 100% mortality against first and second-instar larvae of Cx. quinquefasciatus. Metabolite exposure to larvae exhibited several abnormal behavioral changes. The exposure to F. begoniae metabolite, key esterases such as acetylcholinesterase, α-and-β-carboxylesterase, and acid and alkaline phosphatase activity significantly decreased compared to control larvae. The outcomes of the histology analysis revealed that the mycelium metabolites-treated targeted larvae had a disorganized abdominal mid and hindgut epithelial cells. The is first-hand information on study of ethyl-acetate-derived metabolites from F. begoniae tested against larvae and pupae of Ae. aegypti, Cx. quinquefasciatus and An. stephensi. Bio-indicator toxicity findings demonstrate that A. nauplii displayed no mortality.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04061-z.

Fusarium and Hazelnut: A Story of Twists and Turns

In recent years, the number of reports of Fusarium in association with hazelnut (Corylus avellana) has been increasing worldwide, related to both pathogenic aptitude and endophytic occurrence. However, the assessment of the real ecological role and relevance to plant health of these fungi has been impaired by uncertainty in species identification, deriving from both the evolving taxonomic structure of the genus and an inaccurate use of molecular markers. In this paper, the characterization of two hazelnut endophytic strains isolated in Poland is reported with reference to their secondary metabolite profiles and interactions with pests and pathogens. Our results are indicative of a possible role of these strains in defensive mutualism which could be related to the production of several bioactive compounds, especially cyclohexadepsipeptides of the enniatin family. At the same time, these biochemical properties create some concern for the possible mycotoxin contamination of hazelnut products.

Statistical optimization of environmental factors to produce the cytotoxic enniatins H, I and MK1688 against human multidrug resistance cancer cell lines

The environmental conditions were optimized to produce the enniatin H, I, and MK1688 by Fusarium strain on cereal grain exhibiting anti-carcinogenic potential against MES-SA (human uterine sarcoma cell line), HCT15 (human colorectal carcinoma cancer cell line), and their multidrug resistance sublines. From the statistical optimization by response surface methodology, the optimal condition of independent variables affecting the response variables were 20.85 °C (temperature), 46.85% (w/w, initial moisture content), and 18.42 days (growth time) for ENN H; 23.31 °C, 44.15% (w/w) and 17.23 days for ENN I; 23.08 °C, 43.97% (w/w) and 17.06 days for ENN MK1688. In case of cytotoxic effects, ENNs significantly suppressed growth of cancer cell lines without multidrug resistance, and ENN I inhibited growth of cancer cell lines most strongly. These data will provide valuable point to produce the cyclic hexadepsipeptide exhibiting anti-carcinogenic potential from Fusarium strains.

Fusarium-Derived Secondary Metabolites with Antimicrobial Effects

Fungal microbes are important in the creation of new drugs, given their unique genetic and metabolic diversity. As one of the most commonly found fungi in nature, Fusarium spp. has been well regarded as a prolific source of secondary metabolites (SMs) with diverse chemical structures and a broad spectrum of biological properties. However, little information is available concerning their derived SMs with antimicrobial effects. By extensive literature search and data analysis, as many as 185 antimicrobial natural products as SMs had been discovered from Fusarium strains by the end of 2022. This review first provides a comprehensive analysis of these substances in terms of various antimicrobial effects, including antibacterial, antifungal, antiviral, and antiparasitic. Future prospects for the efficient discovery of new bioactive SMs from Fusarium strains are also proposed.

Impact of Enniatin and Deoxynivalenol Co-Occurrence on Plant, Microbial, Insect, Animal and Human Systems: Current Knowledge and Future Perspectives

Fusarium mycotoxins commonly contaminate agricultural products resulting in a serious threat to both animal and human health. The co-occurrence of different mycotoxins in the same cereal field is very common, so the risks as well as the functional and ecological effects of mycotoxins cannot always be predicted by focusing only on the effect of the single contaminants. Enniatins (ENNs) are among the most frequently detected emerging mycotoxins, while deoxynivalenol (DON) is probably the most common contaminant of cereal grains worldwide. The purpose of this review is to provide an overview of the simultaneous exposure to these mycotoxins, with emphasis on the combined effects in multiple organisms. Our literature analysis shows that just a few studies on ENN-DON toxicity are available, suggesting the complexity of mycotoxin interactions, which include synergistic, antagonistic, and additive effects. Both ENNs and DON modulate drug efflux transporters, therefore this specific ability deserves to be explored to better understand their complex biological role. Additionally, future studies should investigate the interaction mechanisms of mycotoxin co-occurrence on different model organisms, using concentrations closer to real exposures.

Enniatins from a marine-derived fungus Fusarium sp. inhibit biofilm formation by the pathogenic fungus Candida albicans

Candidemia is a life-threatening disease common in immunocompromised patients, and is generally caused by the pathogenic fungus Candida albicans. C. albicans can change morphology from yeast to hyphae, forming biofilms on medical devices. Biofilm formation contributes to the virulence and drug tolerance of C. albicans, and thus compounds that suppress this morphological change and biofilm formation are effective for treating and preventing candidemia. Marine organisms produce biologically active and structurally diverse secondary metabolites that are promising lead compounds for treating numerous diseases. In this study, we explored marine-derived fungus metabolites that can inhibit morphological change and biofilm formation by C. albicans. Enniatin B (1), B1 (2), A1 (3), D (4), and E (5), visoltricin (6), ergosterol peroxide (7), 9,11-dehydroergosterol peroxide (8), and 3β,5α,9α-trihydroxyergosta-7,22-dien-6-one (9) were isolated from the marine-derived fungus Fusarium sp. Compounds 1-5 and 8 exhibited inhibitory activity against hyphal formation by C. albicans, and compounds 1-3 and 8 inhibited biofilm formation by C. albicans. Furthermore, compounds 1-3 decreased cell surface hydrophobicity and expression of the hypha-specific gene HWP1 in C. albicans. Compound 1 was obtained in the highest yield. An in vivo evaluation system using silkworms pierced with polyurethane fibers (a medical device substrate) showed that compound 1 inhibited biofilm formation by C. albicans in vivo. These results indicate that enniatins could be lead compounds for therapeutic agents for biofilm infections by C. albicans.

Metabolites and novel compounds with anti-microbial or antiaging activities from Cordyceps fumosorosea

High-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) analysis revealed that there are 20 main components in spores and mycelia extract of Cordyceps fumosorosea strain RCEF 6672 including mannitol (1), uridine (2), adenine (3). N⁶-(2-hydroxyethyl)-adenosine (4). N⁶-(2-hydroxyethylacetate)-adenosine (5), fumosoroseanoside A (6) and B (7), ovalicin-4α-alcohol (8), 1-linoleoyl-sn-glycero-3-phosphocholine (9) and its isomer (10), fumosoroseain A (11) and its isomer (12), 5 non-ribosomal peptides (13 to 17) and 3 fatty acids (18 to 20). The compounds 5, 6, 7, 9 and 11 were prepared with preparative and semi-preparative HPLC and identified with 1D and 2D NMR. Compounds 4 and 5 were the first time identified from C. fumosorosea. Compounds 6, 7 and 11 are novel compounds. Compounds 6 and 7 showed antibacterial and antifungal activities, and 11 showed antiaging activity. All the secondary metabolites (4 to 8 and 11 to 17) have strong bioactivities indicating that the metabolites have pharmaceutical development potentiality.

Clarified small molecular metabolites of C. fumosorosea for the first time.

Identified three novel compounds with antimicrobial or antiaging activities.

The fungus has development potentiality for rich in bioactive metabolites.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Enniatin B and Deoxynivalenol Activity on Bread Wheat and on Fusarium Species Development

Fusarium head blight (FHB) is a devastating wheat disease, mainly caused by Fusarium graminearum (FG)-a deoxynivalenol (DON)-producing species. However, Fusarium avenaceum (FA), able to biosynthesize enniatins (ENNs), has recently increased its relevance worldwide, often in co-occurrence with FG. While DON is a well-known mycotoxin, ENN activity, also in association with DON, is poorly understood. This study aims to explore enniatin B (ENB) activity, alone or combined with DON, on bread wheat and on Fusarium development. Pure ENB, DON, and ENB+DON (10 mg kg-1) were used to assess the impacts on seed germination, seedling growth, cell death induction (trypan blue staining), chlorophyll content, and oxidative stress induction (malondialdehyde quantification). The effect on FG and FA growth was tested using ENB, DON, and ENB+DON (10, 50, and 100 mg kg-1). Synergistic activity in the reduction of seed germination, growth, and chlorophyll degradation was observed. Conversely, antagonistic interaction in cell death and oxidative stress induction was found, with DON counteracting cellular stress produced by ENB. Fusarium species responded to mycotoxins in opposite directions. ENB inhibited FG development, while DON promoted FA growth. These results highlight the potential role of ENB in cell death control, as well as in fungal competition.

Bioprospecting Trichoderma: A Systematic Roadmap to Screen Genomes and Natural Products for Biocontrol Applications

Natural products derived from microbes are crucial innovations that would help in reaching sustainability development goals worldwide while achieving bioeconomic growth. Trichoderma species are well-studied model fungal organisms used for their biocontrol properties with great potential to alleviate the use of agrochemicals in agriculture. However, identifying and characterizing effective natural products in novel species or strains as biological control products remains a meticulous process with many known challenges to be navigated. Integration of recent advancements in various "omics" technologies, next generation biodesign, machine learning, and artificial intelligence approaches could greatly advance bioprospecting goals. Herein, we propose a roadmap for assessing the potential impact of already known or newly discovered Trichoderma species for biocontrol applications. By screening publicly available Trichoderma genome sequences, we first highlight the prevalence of putative biosynthetic gene clusters and antimicrobial peptides among genomes as an initial step toward predicting which organisms could increase the diversity of natural products. Next, we discuss high-throughput methods for screening organisms to discover and characterize natural products and how these findings impact both fundamental and applied research fields.

Cyclic depsipeptide mycotoxin exposure may cause human endocrine disruption: Evidence from OECD in vitro stably transfected transcriptional activation assays

The presence of cyclic depsipeptide mycotoxins in foods and feedstuffs could potentially cause endocrine disrupting effects on humans and wildlife by their inhibition of active steroidogenesis. Therefore, we attempted to assess the human estrogen receptor (ER) and androgen receptor (AR) agonistic/antagonistic effects of representative cyclic depsipeptide mycotoxins, enniatin A1 (ENN A1), and enniatin B1 (ENN B1), by OECD Performand Based Test Guideline (PBTG) No.455, VM7Luc ER transcriptional activation (TA) assay and OECD TG No. 458, 22Rv1/MMTV_GR-KO AR TA assay. No tested cyclic depsipeptide mycotoxins were found to be ER and AR agonists in VM7Luc ER TA and 22Rv1/MMTV_GR-KO AR TA assays. On the other hand, ENN A1, and ENN B1 exhibited the ER and AR antagonistic effects with IC₃₀ and IC₅₀ values in both TA assays. These two cyclic depsipeptide mycotoxins, which were determined as ER and AR antagonists by two in vitro assays, bound to ERα, and AR. Then ENN A1, and ENN B1 inhibited the dimerization of ERα, and AR. These results, for the first time indicated that ENN A1, and ENN B1 could have potential endocrine disrupting effects mediated by interaction of ERα and AR using international standard testing methods to determine the potential endocrine disrupting chemical.

Beauvericin and Enniatins: In Vitro Intestinal Effects

Food and feed contamination by emerging mycotoxins beauvericin and enniatins is a worldwide health problem and a matter of great concern nowadays, and data on their toxicological behavior are still scarce. As ingestion is the major route of exposure to mycotoxins in food and feed, the gastrointestinal tract represents the first barrier encountered by these natural contaminants and the first structure that could be affected by their potential detrimental effects. In order to perform a complete and reliable toxicological evaluation, this fundamental site cannot be disregarded. Several in vitro intestinal models able to recreate the different traits of the intestinal environment have been applied to investigate the various aspects related to the intestinal toxicity of emerging mycotoxins. This review aims to depict an overall and comprehensive representation of the in vitro intestinal effects of beauvericin and enniatins in humans from a species-specific perspective. Moreover, information on the occurrence in food and feed and notions on the regulatory aspects will be provided.

Enniatin A1, A Natural Compound with Bactericidal Activity against Mycobacterium tuberculosis In Vitro

Background: Tuberculosis remains a global disease that poses a serious threat to human health, but there is lack of new and available anti-tuberculosis agents to prevent the emergence of drug-resistant strains. To address this problem natural products are still potential sources for the development of novel drugs. Methods: A whole-cell screening approach was utilized to obtain a natural compound enniatin A1 from a natural products library. The target compound’s antibacterial activity against Mycobacterium tuberculosis (M. tuberculosis) was evaluated by using the resazurin reduction micro-plate assay (REMA) method. The cytotoxicity of the compound against Vero cells was measured to calculate the selectivity index. The intracellular inhibition activity of enniatin A1 was determined. We performed its time-kill kinetic assay against M. tuberculosis. We first tested its synergistic effect in combination with the first and second-line anti-tuberculosis drugs. Finally, we measured the membrane potential and intracellular ATP levels of M. tuberculosis after exposure to enniatin A1. Results: We identified enniatinA1 as a potential antibacterial agent against M. tuberculosis, against which it showed strong selectivity. Enniatin A1 exhibited a time-concentration-dependent bactericidal effect against M. tuberculosis, and it displayed synergy with rifamycin, amikacin, and ethambutol. After exposure to enniatinA1, the membrane potential and intracellular ATP levels of M. tuberculosis was significantly decreased. Conclusions: Enniatin A1 exhibits the positive potential anti-tuberculosis agent characteristics.

Co-Occurrence of Beauvericin and Enniatins in Edible Vegetable Oil Samples, China

A total of 470 edible vegetable oil samples including peanut, soybean, rapeseed, sesame seed, corn, blend, and others collected from eight provinces of China were analyzed for the concentrations of beauvericin (BEA), enniatin A (ENA), A₁ (ENA₁), B (ENB), and B₁ (ENB₁) by ultraperformance liquid chromatography/electrospray ionization tandem mass spectrometry (UPLC/ESI-MS/MS). Concentrations of BEA, ENB, and ENB₁ (average = 5.59 μg/kg, 5.16 μg/kg, and 4.61 μg/kg) in all positive samples were higher than those for ENA and ENA₁ (average = 0.85 μg/kg and 1.88 μg/kg). Frequencies of BEA and ENNs in all analyzed samples were all higher than 50% with the exception of ENA₁ (36.6%, 172/470). Levels of BEA and ENNs in all analyzed samples varied based on their sample types and geographical distributions (Kruskal–Wallis test, p < 0.05). The soybean and peanut oil samples were found to be more easily contaminated by BEA and ENNs than other oil samples. Concentrations of BEA and ENNs in samples obtained from Heilongjiang, Shandong and Guizhou were higher than those found in samples from other provinces. Besides, frequencies of mycotoxin co-contaminations were high and their co-contamination types also varied by oil types. BEA-ENA-ENA₁-ENB-ENB₁ was the most commonly found toxin combination type, almost in one third of the analyzed samples (30%, 141/470). Overall, these results indicate that co-occurrence of BEA and ENNs in analyzed Chinese edible vegetable oil samples is highly common, and it is vital to monitor them, both simultaneously and on a widespread level.

Natural Occurrence of Beauvericin and Enniatins in Corn- and Wheat-Based Samples Harvested in 2017 Collected from Shandong Province, China

Totals of 158 corn and corn-based samples and 291 wheat and wheat-based samples from Shandong province, China in 2017 were analyzed for five mycotoxins including beauvericin (BEA), enniatin A (ENA), enniatin A₁ (ENA₁), enniatin B (ENB), and enniatin B₁ (ENB₁) by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). BEA was the predominant toxin detected, followed by ENB, ENA₁, ENA, and ENB₁. Corn and corn-based samples were more easily contaminated by BEA with an average concentration of 65.26 µg/kg, compared with that in wheat and wheat-based samples (average = 0.41 µg/kg). Concentrations of BEA, ENA, and ENB₁ in corn kernels, flours, and flakes were significantly different (Kruskal–Wallis Test, p < 0.05), as well as for BEA, ENA, ENB, and ENB₁ in wheat kernels, flours, and noodles (Kruskal–Wallis test, p < 0.05). Furthermore, 59.5% (94/158) and 59.8% (174/291) corn- and wheat-based samples were co-contaminated by at least two mycotoxins, respectively. Positive correlations in concentrations were observed in corn between levels of ENA and ENB₁, ENA and ENB, ENA₁ and ENB₁, as well as in wheat between BEA and ENA, BEA and ENA₁, BEA and ENB, BEA and ENB₁, ENA and ENA₁, ENA and ENB, ENA and ENB₁, ENA₁ and ENB, ENA₁ and ENB₁, and ENB and ENB₁. These results demonstrate that co-contamination of BEA and enniatins (ENNs) in corn- and wheat-based samples from Shandong, China is very common. More data on the contamination of five mycotoxins in cereal and cereal-based samples nationwide are needed.

Isolation and characterization of plumbagin (5- hydroxyl- 2- methylnaptalene-1,4-dione) producing endophytic fungi Cladosporium delicatulum from endemic medicinal plants: Isolation and characterization of plumbagin producing endophytic fungi from endemic medicinal plants

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Diversity of endophytic fungi from endemic medicinal plants in Eastern Ghats.

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Molecular identification and anti-microbial activity of isolated endophytic cultures.

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GCMS analysis and compound identification of potential crud extract.

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Characterization of purified fraction using FTIR spectroscopy, MS and NMR.

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Potentially inhibition of tested pathogens by identified compound 5-hydroxy-2-methylnaphthalene-1, 4-Dione.

The rationale of the present study was to isolate and identify endophytic fungi from endemic medicinal plants in Eastern Ghats and screened for antimicrobial potential of isolated fungal crude extracts. A total of 329 endophytic strains were isolated from 600 infected leaves and stem cuttings of endemic plants. The diversity and species richness was analyzed statistically and found to be higher in leaf segments than in stem segments. From isolated fungal strains, Cladosporium delicatulum was identified using molecular identification methods and selected as the most potent plumbagin-producing endophytic strain. Further the isolation and structural characterization of endophytic fungal plumbagin (5-hydroxyl-2-methylnaptalene-1,4-dione) was purified and confirmed through spectroscopy analysis. The molecular weight was determined as m/z 188 in positive mode by ESI-MS, which confirmed to be plumbagin which potentially inhibited all tested pathogens, therefore the endophytic fungal plumbagin from the current study possesses important biological activities against pathogens.

A Review of the Mycotoxin Enniatin B

Mycotoxin enniatin B (ENN B) is a secondary metabolism product by Fusarium fungi. It is a well-known antibacterial, antihelmintic, antifungal, herbicidal, and insecticidal compound. It has been found as a contaminant in several food commodities, particularly in cereal grains, co-occurring also with other mycotoxins. The primary mechanism of action of ENN B is mainly due to its ionophoric characteristics, but the exact mechanism is still unclear. In the last two decades, it has been a topic of great interest since its potent mammalian cytotoxic activity was demonstrated in several mammalian cell lines. Moreover, the co-exposure in vitro with other mycotoxins enhances its toxic potential through synergic effects, depending on the concentrations tested. Despite its clear cytotoxic effect, European Food Safety Authority stated that acute exposure to ENNs, such as ENN B, does not indicate concern for human health, but a concern might be the chronic exposure. However, given the lack of relevant toxicity data, no firm conclusion could be drawn and a risk assessment was not possible. In fact, very few studies have been carried out in vivo and, in these studies, no adverse effects were observed. So, research on toxicological effects induced by ENN B is still on-going. Recently, some studies are dealing with new advances regarding ENN B. This review summarizes the information on biochemical and biological activity of ENN B, focusing on toxicological aspects and on the latest advances in research on ENN B.

Occurrence of beauvericin and enniatins in wheat flour and corn grits on the Japanese market, and their co-contamination with type B trichothecene mycotoxins

The contamination levels of beauvericin and four enniatins, A, A₁, B and B₁, in 207 samples of wheat flour and corn grits on the Japanese market were determined by an analytical method based on LC-MS/MS. The toxins were extracted from samples with acetonitrile-water (85:15, v/v) and then purified with C18 cartridges. The method was validated in a single laboratory using spiked samples at two levels; the recovery of the five toxins ranged from 91.1% to 113.8%. Enniatin B was frequently detected in imported wheat flour (81.8%) and domestic wheat flour (85.6%), and the highest concentration of enniatin B was present in a domestic wheat sample (633 μg kg^-1). In corn grits, beauvericin was found in 34% of the samples, but enniatins were not detected at all. The maximum concentration of beauvericin in corn grits was 26.1 μg kg^-1. Deoxynivalenol and nivalenol in the same samples were determined by a method using an immunoaffinity column. Co-contamination of deoxynivalenol and enniatins was observed in 61% of the imported wheat samples and in 58% of the domestic wheat samples. These results suggest the need for a risk assessment for cyclic depsipeptide mycotoxins in Japan and a study on the synergistic effect of deoxynivalenol and enniatins.

Lipopeptide surfactants: Production, recovery and pore forming capacity

Lipopeptides are microbial surface active compounds produced by a wide variety of bacteria, fungi and yeast. They are characterized by highly structural diversity and have the ability to decrease the surface and interfacial tension at the surface and interface, respectively. Surfactin, iturin and fengycin of Bacillus subtilis are among the most studied lipopeptides. This review will present the main factors encountering lipopeptides production along with the techniques developed for their extraction and purification. Moreover, we will discuss their ability to form pores and destabilize biological membrane permitting their use as antimicrobial, hemolytic and antitumor agents. These open great potential applications in biomediacal, pharmaceutic and agriculture fields.

Volatile Metabolite Profiling of Durum Wheat Kernels Contaminated by Fusarium poae

Volatile metabolites from mold contamination have been proposed for the early identification of toxigenic fungi to prevent toxicological risks, but there are no such data available for Fusarium poae. F. poae is one of the species complexes involved in Fusarium head blight, a cereal disease that results in significant yield losses and quality reductions. The identification of volatile organic compounds associated with F. poae metabolism could provide good markers to indicate early fungal contamination. To this aim, we evaluated the volatile profile of healthy and F. poae-infected durum wheat kernels by SPME-GC/MS analysis. The production of volatile metabolites was monitored for seven days, and the time course analysis of key volatiles was determined. A total of 29 volatile markers were selected among the detected compounds, and multivariate analysis was applied to establish the relationship between potential volatile markers and fungal contamination. A range of volatile compounds, including alcohols, ketones, esters, furans and aromatics, were identified, both in contaminated and in healthy kernels. However, the overall volatile profile of infected samples and controls differed, indicating that the whole volatile profile, rather than individual volatile compounds, could be used to identify F. poae contamination of durum wheat grains.

FTIR spectroscopic evaluation of changes in the cellular biochemical composition of the phytopathogenic fungus Alternaria alternata induced by extracts of some Greek medicinal and aromatic plants

In this study, the biological activity of aquatic extracts of selected Greek medicinal and aromatic plants to the phytopathogenic fungus Alternaria alternata was investigated. Lamiaceae species (Hyssopus officinalis L., Melissa officinalis L., Origanum dictamnus L., Origanum vulgare L. and Salvia officinalis L.) were found to enhance significantly the mycelium growth whereas Crocus sativus appears to inhibit it slightly. M. officinalis and S. officinalis caused the highest stimulation in mycelium growth (+97%) and conidia production (+65%) respectively. In order to further investigate the bioactivity of plant extracts to A. alternata, we employed Fourier Transform Infrared Spectroscopy (FTIR). Differences of original spectra were assigned mainly to amides of proteins. The second derivative transformation of spectra revealed changes in spectral regions corresponding to absorptions of the major cellular constituents such as cell membrane and proteins. Principal component analysis of the second derivative transformed spectra confirmed that fatty acids of the cell membranes, amides of proteins and polysaccharides of the cell wall had the major contribution to data variation. FTIR band area ratios were found to correlate with fungal mycelium growth.

Antibacterial activity of the emerging Fusarium mycotoxins enniatins A, A₁, A₂, B, B₁, and B₄ on probiotic microorganisms

Enniatins (ENs) are secondary metabolites produced by several Fusarium strains, chemically characterized as N-methylated cyclohexadepsipeptides. These compounds are known to act as antifungal and antibacterial agents, but they also possess anti-insect and phytotoxic properties. In this study, the antimicrobial effect of pure fractions of the bioactive compounds ENs A, A₁, A₂, B, B₁, and B₄ was tested towards nine probiotic microrganisms, twenty-two Saccharomyces cerevisiae strains and nine Bacillus subtilis strains. Antimicrobial analyses were carried out the disc-diffusion method using ENs concentrations ranging from 0.2 to 20,000 ng. Plates were incubated for 24 h at 37 °C before reading the diameter of the inhibition spots. ENs A, A₁, A₂, B, B₁ and B₄, were active against several microorganisms with inhibition halos ranging from 3 to 12 mm in diameter. The most active mycotoxin was the EN A₁, which reduced the microbial growth of 8 strains at the dose of 20,000 ng, with inhibition spots sized between 8 and 12 mm. ENs B and B₄ showed no antimicrobial activity towards the microorganisms tested at doses up to 20,000 ng per disc.

Endophytic fungi isolated from oil-seed crop Jatropha curcas produces oil and exhibit antifungal activity

Jatropha curcas L., a perennial plant grown in tropics and subtropics is popularly known for its potential as biofuel. The plant is reported to survive under varying environmental conditions having tolerance to stress and an ability to manage pest and diseases. The plant was explored for its endophytic fungi for use in crop protection. Endophytic fungi were isolated from leaf of Jatropha curcas, collected from New Delhi, India. Four isolates were identified as Colletotrichum truncatum, and other isolates were identified as Nigrospora oryzae, Fusarium proliferatum, Guignardia cammillae, Alternaria destruens, and Chaetomium sp. Dual plate culture bioassays and bioactivity assays of solvent extracts of fungal mycelia showed that isolates of Colletotrichum truncatum were effective against plant pathogenic fungi Fusarium oxysporum and Sclerotinia sclerotiorum. Isolate EF13 had highest activity against S. sclerotiorum. Extracts of active endophytic fungi were prepared and tested against S. sclerotiorum. Ethyl acetate and methanol extract of C. truncatum EF10 showed 71.7% and 70% growth inhibition, respectively. Hexane extracts of C. truncatum isolates EF9, EF10, and EF13 yielded oil and the oil from EF10 was similar to oil of the host plant, i.e., J. curcas.

Identification and bioactive potential of endophytic fungi isolated from selected plants of the Western Himalayas

This study was conducted to characterize and explore the endophytic fungi of selected plants from the Western Himalayas for their bioactive potential. A total of 72 strains of endophytic fungi were isolated and characterized morphologically as well as on the basis of ITS1-5.8S-ITS2 ribosomal gene sequence acquisition and analyses. The fungi represented 27 genera of which two belonged to Basidiomycota, each representing a single isolate, while the rest of the isolates comprised of Ascomycetous fungi. Among the isolated strains, ten isolates could not be assigned to a genus as they displayed a maximum sequence similarity of 95% or less with taxonomically characterized organisms. Among the host plants, the conifers, Cedrus deodara, Pinus roxburgii and Abies pindrow harbored the most diverse fungi, belonging to 13 different genera, which represented almost half of the total genera isolated. Several extracts prepared from the fermented broth of these fungi demonstrated strong bioactivity against E. coli and S. aureus with the lowest IC₅₀ of 18 μg/ml obtained with the extract of Trichophaea abundans inhabiting Pinus sp. In comparison, extracts from only three endophytes were significantly inhibitory to Candida albicans, an important fungal pathogen. Further, 24 endophytes inhibited three or more phytopathogens by at least 50% in co-culture, among a panel of seven test organisms. Extracts from 17 fungi possessed immuno-modulatory activities with five of them showing significant immune suppression as demonstrated by the in vitro lymphocyte proliferation assay. This study is an important step towards tapping the endophytic fungal diversity from the Western Himalayas and assessing their bioactive potential. Further studies on the selected endophytes may lead to the isolation of novel natural products for use in medicine, industry and agriculture.

Revisiting the enniatins: a review of their isolation, biosynthesis, structure determination and biological activities

Enniatins are cyclohexadepsipeptides isolated largely from Fusarium species of fungi, although they have been isolated from other genera, such as Verticillium and Halosarpheia. They were first described over 60 years ago, and their range of biological activities, including antiinsectan, antifungal, antibiotic and cytotoxic, drives contemporary interest. To date, 29 enniatins have been isolated and characterized, either as a single compound or mixtures of inseparable homologs. Structurally, these depsipeptides are biosynthesized by a multifunctional enzyme, termed enniatin synthetase, and are composed of six residues that alternate between N-methyl amino acids and hydroxy acids. Their structure elucidation can be challenging, particularly for enniatins isolated as inseparable homologs; however, several strategies and tools have been utilized to solve these problems. Currently, there is one drug that has been developed from a mixture of enniatins, fusafungine, which is used as a topical treatment of upper respiratory tract infections by oral and/or nasal inhalation. Given the range of biological activities observed for this class of compounds, research on enniatins will likely continue. This review strives to digest the past studies, as well as, describe tools and techniques that can be utilized to overcome the challenges associated with the structure elucidation of mixtures of enniatin homologs.

ATP citrate lyase 1 (acl1) gene-based loop-mediated amplification assay for the detection of the Fusarium tricinctum species complex in pure cultures and in cereal samples

The combined data set of the acl1 and tef-1α gene sequences of 61 fungal strains assigned to Fusarium tricinctum, Fusarium avenaceum, Fusarium acuminatum, Fusarium arthrosporioides, Fusarium flocciferum and Fusarium torulosum were used to study the phylogenetic relations between taxa. F. tricinctum, F. acuminatum and F. avenaceum formed distinct clades. Members of the F. tricinctum/F. acuminatum clade fall into three well supported lineages, of which the largest includes the epitype of F. tricinctum. Loop-mediated isothermal amplification (LAMP) was used to amplify a 167 bp portion of the acl1 gene in F. tricinctum (Corda) Saccardo. DNA amplification was detected in-tube by indirect calcein fluorescence under black light after 60 min of incubation at 65.5 °C. The assay had a detection limit of 0.95 pg of purified genomic DNA of F. tricinctum CBS 410.86 per reaction, corresponding to ca. 18 genomic copies of the acl1 gene. Specificity of the assay was tested using purified DNA from 67 species and subspecies of Fusarium as well as 50 species comprising 22 genera of other filamentous fungi and yeasts. The assay detected 21 of the 23 F. tricinctum strains tested. Cross reactivity was observed with eight out of 13 strains in F. acuminatum but with none of 17 F. avenaceum strains tested. Specificity was further confirmed by conventional PCR with primers designed from the same gene. Detection of F. tricinctum from culture scrapings directly added to the reaction master mix, in DNA extracts from wheat, in single barley grains or in washings of bulk grain samples are proposed as possible applications showing the suitability of the method for food analysis. Finally it was demonstrated that the LAMP reaction can be run using simple lab equipment such as a heating block, water bath, hybridization oven or household equipment, e.g. a microwave oven.

Enniatin B-induced cell death and inflammatory responses in RAW 267.4 murine macrophages

The mycotoxin enniatin B (EnnB) is predominantly produced by species of the Fusarium genera, and often found in grain. The cytotoxic effect of EnnB has been suggested to be related to its ability to form ionophores in cell membranes. The present study examines the effects of EnnB on cell death, differentiation, proliferation and pro-inflammatory responses in the murine monocyte-macrophage cell line RAW 264.7. Exposure to EnnB for 24 h caused an accumulation of cells in the G0/G1-phase with a corresponding decrease in cyclin D1. This cell cycle-arrest was possibly also linked to the reduced cellular ability to capture and internalize receptors as illustrated by the lipid marker ganglioside GM1. EnnB also increased the number of apoptotic, early apoptotic and necrotic cells, as well as cells with elongated spindle-like morphology. The Neutral Red assay indicated that EnnB induced lysosomal damage; supported by transmission electron microscopy (TEM) showing accumulation of lipids inside the lysosomes forming lamellar structures/myelin bodies. Enhanced levels of activated caspase-1 were observed after EnnB exposure and the caspase-1 specific inhibitor ZYVAD-FMK reduced EnnB-induced apoptosis. Moreover, EnnB increased the release of interleukin-1 beta (IL-1β) in cells primed with lipopolysaccharide (LPS), and this response was reduced by both ZYVAD-FMK and the cathepsin B inhibitor CA-074Me. In conclusion, EnnB was found to induce cell cycle arrest, cell death and inflammation. Caspase-1 appeared to be involved in the apoptosis and release of IL-1β and possibly activation of the inflammasome through lysosomal damage and leakage of cathepsin B.

Stimulation of erythrocyte phospholipid scrambling by enniatin A

SCOPE

Enniatin A, a peptide antibiotic and common food contaminant, triggers mitochondrial dysfunction and apoptosis. Even though lacking mitochondria, erythrocytes may similarly undergo suicidal cell death or eryptosis. Eryptosis is characterized by cell shrinkage and cell membrane phospholipid scrambling. Triggers of phospholipid scrambling include energy depletion and increase in cytosolic Ca(2+) activity ([Ca(2+) ](i) ). The present study explored whether enniatin A triggers phospholipid scrambling.

METHODS AND RESULTS

Phospholipid scrambling was estimated from annexin-V-binding, cell volume from forward scatter (FSC), [Ca(2+) ](i) from Fluo3-fluorescence, cytosolic ATP-concentration ([ATP](i) ) using a luciferase assay and hemolysis from hemoglobin release. Exposure of erythrocytes for 48 h to enniatin A (≥ 2.5 μM) significantly increased [Ca(2+) ](i) , decreased [ATP](i) , decreased FSC, triggered annexin-V-binding and elicited hemolysis. Annexin-V-binding affected 25%, and hemolysis 2% of treated erythrocytes. Decreased [ATP](i) by glucose depletion for 48 h was similarly followed by increased [Ca(2+) ](i) , decreased FSC and annexin-V-binding. Enniatin A augmented the effect on [Ca(2+) ](i) and annexin-V-binding, but not on FSC. Annexin-V-binding was blunted by Ca(2+) removal, by the cation channel inhibitor amiloride (1 mM), by the protein kinase C inhibitor staurosporine (500 nM) but not by the pancaspase inhibitor zVAD (10 μM).

CONCLUSION

The food contaminant enniatin A triggers ATP depletion and increases cytosolic Ca(2+) activity, effects resulting in suicidal erythrocyte death.

Antibacterial effects of enniatins J(1) and J(3) on pathogenic and lactic acid bacteria

Enniatins (ENs) are N-methylated cyclohexadepsipeptides, secondary metabolites produced by various species of the genus Fusarium. They are known to act as antifungal, antiyeast and antibacterial and to possess antiinsecticidal and phytotoxic properties. In this study we evaluated for the first time the antibiotic effect of pure fractions of EN J(1) and J(3) on several pathogenic strains and lactic acid bacteria. The ENs J(1) and J(3) were purified from the fermentation extract of Fusarium solani growth on solid medium of wheat kamut, using the technique of the low pressure liquid chromatography (LPLC) followed by a semipreparative liquid chromatography (LC). The purity and the structure of the isolated compound were confirmed by electrospray ionization-mass spectrometry study-linear ion trap (ESI-MS-LIT). The use of both chromatographic techniques have permitted to produce and purify 47mg of the En J(1) and 50mg of the EN J(3) with a mean purity of 98% completely characterized with the technique of the ESI-MS-LIT. Microbial bioassay analyses were carried out by incubation in MRSA and TSA for acid lactic and pathogenic bacteria, respectively during 24h at 37°C. None of the tested strains were inhibited by a 1ng dose of EN J(1) and J(3). These compounds were only not effective against Listeria monocytogenes, Pseudomonas aeruginosa and Salmonella enteric. This study highlight ENs J(1) and J(3) could be potentially effective antibacterial agents against several pathogenic and lactic acid bacteria.

Low water activity induces the production of bioactive metabolites in halophilic and halotolerant fungi

The aim of the present study was to investigate indigenous fungal communities isolated from extreme environments (hypersaline waters of solar salterns and subglacial ice), for the production of metabolic compounds with selected biological activities: hemolysis, antibacterial, and acetylcholinesterase inhibition. In their natural habitats, the selected fungi are exposed to environmental extremes, and therefore the production of bioactive metabolites was tested under both standard growth conditions for mesophilic microorganisms, and at high NaCl and sugar concentrations and low growth temperatures. The results indicate that selected halotolerant and halophilic species synthesize specific bioactive metabolites under conditions that represent stress for non-adapted species. Furthermore, adaptation at the level of the chemical nature of the solute lowering the water activity of the medium was observed. Increased salt concentrations resulted in higher hemolytic activity, particularly within species dominating the salterns. The appearance of antibacterial potential under stress conditions was seen in the similar pattern of fungal species as for hemolysis. The active extracts exclusively affected the growth of the Gram-positive bacterium tested, Bacillus subtilis. None of the extracts tested showed inhibition of acetylcholinesterase activity.