Tremorgenic Mycotoxins: Structure Diversity and Biological Activity

Biochemical characterization of a multiple prenyltransferase from Tolypocladium inflatum

Prenylation plays a pivotal role in the diversification and biological activities of natural products. This study presents the functional characterization of TolF, a multiple prenyltransferase from Tolypocladium inflatum. The heterologous expression of tolF in Aspergillus oryzae, coupled with feeding the transformed strain with paxilline, resulted in the production of 20- and 22-prenylpaxilline. Additionally, TolF demonstrated the ability to prenylated the reduced form of paxilline, β-paxitriol. A related prenyltransferase TerF from Chaunopycnis alba, exhibited similar substrate tolerance and regioselectivity. In vitro enzyme assays using purified recombinant enzymes TolF and TerF confirmed their capacity to catalyze prenylation of paxilline, β-paxitriol, and terpendole I. Based on previous reports, terpendole I should be considered a native substrate. This work not only enhances our understanding of the molecular basis and product diversity of prenylation reactions in indole diterpene biosynthesis, but also provides insights into the potential of fungal indole diterpene prenyltransferase to alter their position specificities for prenylation. This could be applicable for the synthesis of industrially useful compounds, including bioactive compounds, thereby opening up new avenues for the development of novel biosynthetic strategies and pharmaceuticals. KEY POINTS: • The study characterizes TolF as a multiple prenyltransferase from Tolypocladium inflatum. • TerF from Chaunopycnis alba shows similar substrate tolerance and regioselectivity compared to TolF. • The research offers insights into the potential applications of fungal indole diterpene prenyltransferases.

Antiviral and cytotoxic indole diterpenoids from the antarctic sponge-derived fungus Aspergillus candidus HDN15-152

One new indole diterpenoid, ascandinine T (1), and three known analogues (2-4) were isolated from an Antarctic sponge-derived fungus Aspergillus candidus HDN15-152. The structures, including absolute configurations, were established based on NMR, HRESIMS, and electronic circular dichroism (ECD) calculations. All isolated compounds were tested for antiviral and anticancer activity. Compound 4 displayed antiviral activity against influenza A virus (IAV) of A/PR/8/34(H1N1) strain with an IC50 value of 39.2 μM, while compound 2 showed cytotoxicity against NCI-H446, NCI-H446/EP and L-02 cells with IC50 values ranging from 9.77 to 13.91 μM.

Synthesis of the indeno[1,2-b]indole core of janthitrem B

The tetracyclic core structure of the majority of indole diterpenoids features a trans-hydrindane moiety that is fused to an indole unit. We report here a novel synthetic route that includes a photo-Nazarov cyclization of a 3-acylindole precursor initially providing the thermodynamically preferred cis-hydrindanone. After reduction and conversion to the cyclopentadiene, dihydroxylation and hydrogenation provided the indoline. The key step generated the trans-system by stereospecific hydride shift on a dioxaphospholane under Grainger's conditions, for the first time applied to an N-heterocycle. When starting from the corresponding indole, we observed the formation of hitherto unknown methanocyclohepta[b]indolones. Deoxygenation of the trans-hydrindanone was achieved after conversion to the 1,3-dithiolane, followed by RANEY® Ni reduction.

Indole Diterpenes from Mangrove Sediment-Derived Fungus Penicillium sp. UJNMF0740 Protect PC12 Cells against 6-OHDA-Induced Neurotoxicity via Regulating the PI3K/Akt Pathway

In our chemical investigation into Penicillium sp. UJNMF0740 derived from mangrove sediment, fourteen indole diterpene analogs, including four new ones, are purified by multiple chromatographic separation methods, with their structures being elucidated by the analyses of NMR, HR-ESIMS, and ECD data. The antibacterial and neuroprotective effects of these isolates were examined, and only compounds 6 and 9 exhibited weak antibacterial activity, while compounds 5, 8, and 10 showed protective effects against the injury of PC12 cells induced by 6-hydroxydopamine (6-OHDA). Additionally, compound 5 could suppress the apoptosis and production of reactive oxygen species (ROS) in 6-OHDA-stimulated PC12 cells as well as trigger the phosphorylation of PI3K and Akt. Taken together, our work enriches the structural diversity of indole diterpenes and hints that compounds of this skeleton can repress the 6-OHDA-induced apoptosis of PC12 cells via regulating the PI3K/Akt signaling pathway, which provides evidence for the future utilization of this fascinating class of molecules as potential neuroprotective agents.

Single Seed Near-Infrared Hyperspectral Imaging for Classification of Perennial Ryegrass Seed

The detection of beneficial microbes living within perennial ryegrass seed causing no apparent defects is challenging, even with the most sensitive and conventional methods, such as DNA genotyping. Using a near-infrared hyperspectral imaging system (NIR-HSI), we were able to discriminate not only the presence of the commercial NEA12 fungal endophyte strain but perennial ryegrass cultivars of diverse seed age and batch. A total of 288 wavebands were extracted for individual seeds from hyperspectral images. The optimal pre-processing methods investigated yielded the best partial least squares discriminant analysis (PLS-DA) classification model to discriminate NEA12 and without endophyte (WE) perennial ryegrass seed with a classification accuracy of 89%. Effective wavelength (EW) selection based on GA-PLS-DA resulted in the selection of 75 wavebands yielding 88.3% discrimination accuracy using PLS-DA. For cultivar identification, the artificial neural network discriminant analysis (ANN-DA) was the best-performing classification model, resulting in >90% classification accuracy for Trojan, Alto, Rohan, Governor and Bronsyn. EW selection using GA-PLS-DA resulted in 87 wavebands, and the PLS-DA model performed the best, with no extensive compromise in performance, resulting in >89.1% accuracy. The study demonstrates the use of NIR-HSI reflectance data to discriminate, for the first time, an associated beneficial fungal endophyte and five cultivars of perennial ryegrass seed, irrespective of seed age and batch. Furthermore, the negligible effects on the classification errors using EW selection improve the capability and deployment of optimized methods for real-time analysis, such as the use of low-cost multispectral sensors for single seed analysis and automated seed sorting devices.

Quantitation and Distribution of Epichloë-Derived Alkaloids in Perennial Ryegrass Tissues

Perennial ryegrass (Lolium perenne L.), an economically important pasture and turf grass, is commonly infected with asexual Epichloë species endophytes. Endophytes provide enhanced bioprotection by producing alkaloids, and research often focusses on the negative impact on grazing animals. However, alkaloid distribution throughout the plant and their role in biocontrol of insect pests and diseases are less well understood. Additionally, intermediate compounds have not been investigated for their impacts on animal welfare and biological control in pasture-based scenarios. Here, a single liquid chromatography-mass spectrometry (LC-MS) method was used to measure seven alkaloids in different perennial ryegrass tissues infected with SE or NEA12 endophytes. High alkaloid recoveries and a clear plant matrix effect emphasize the importance of using matrix-matched standards for accurate quantitation. The method is sensitive, detecting alkaloids at low concentrations (nanogram levels), which is important for endophyte strains that produce compounds detrimental to livestock. Concentrations were generally highest in seeds, but distribution differed in the shoots/roots: peramine, terpendole E, terpendole C and lolitrem B were higher in shoots, whilst ergovaline, paxilline and epoxy-janthitrem I were more evenly distributed throughout the two tissues. Knowledge of alkaloid distribution may allow for concentrations to be predicted in roots based on concentrations in the shoots, thereby assisting future determinations of resistance to insects, especially subterranean root-feeding pests.

The chemical structures and biological activities of indole diterpenoids

Indole diterpenoids (IDTs) are an essential class of structurally diverse fungal secondary metabolites, that generally appear to be restricted to a limited number of fungi, such as Penicillium, Aspergillus, Claviceps, and Epichloe species, etc. These compounds share a typical core structure consisting of a cyclic diterpene skeleton of geranylgeranyl diphosphate (GGPP) and an indole ring moiety derived from indole-3-glycerol phosphate (IGP). 3-geranylgeranylindole (3-GGI) is the common precursor of all IDTs. On this basis, it is modified by cyclization, oxidation, and prenylation to generate a large class of compounds with complex structures. These compounds exhibit antibacterial, anti-insect, and ion channel inhibitory activities. We summarized 204 compounds of IDTs discovered from various fungi over the past 50 years, these compounds were reclassified, and their biological activities were summarized. This review will help to understand the structural diversity of IDTs and provide help for their physiological activities.

Paspalines C-D and Paxillines B-D: New Indole Diterpenoids from Penicillium brefeldianum WZW-F-69

Five new indole diterpenoids named paspaline C-D (1-2) and paxilline B-D (3-5), as well as eleven known analogues (6-16), were identified from fungus Penicillium brefeldianum strain WZW-F-69, which was isolated from an abalone aquaculture base in Fujian province, China. Their structures were elucidated mainly through 1D- and 2D-NMR spectra analysis and ECD comparison. Compound 1 has a 6/5/5/6/6/8 hexacyclic ring system bearing 2,2-dimethyl-1,3-dioxocane, which is rare in natural products. Compound 2 has an unusual open F-ring structure. The cytotoxic activities against 10 cancer cell lines and antimicrobial activities against model bacteria and fungi of all compounds were assayed. No compound showed antimicrobial activity, but at a concentration of 1 μM, compounds 1 and 6 exhibited the highest inhibition rates of 71.2% and 83.4% against JeKo-1 cells and U2OS cells, respectively.

The Biosynthesis Related Enzyme, Structure Diversity and Bioactivity Abundance of Indole-Diterpenes: A Review

Indole diterpenes are a large class of secondary metabolites produced by fungi, possessing a cyclic diterpenoid backbone and an indole moiety. Novel structures and important biological activity have made indole diterpenes one of the focuses of synthetic chemists. Although the discovery, identification, structural diversity, biological activity and especially structure–activity relationship of indole diterpenes have been reported in some papers in recent years, they are absent of a systematic and comprehensive analysis, and there is no elucidation of enzymes related to this kind of natural product. Therefore, it is necessary to summarize the relevant reports to provide new perspectives for the following research. In this review, for the first time, the function of related synthases and the structure–activity relationship of indole diterpenes are expounded, and the recent research advances of them are emphasized.

Indole-diterpenes alkaloid profiles of native grasses involved in tremorgenic syndromes in the Argentine Patagonia

One of the main intoxications to livestock in the Patagonia region of Argentina is the tremorgenic disease "Mal de Huecú", attributed to the consumption of the native grasses Poa huecu and/or Festuca argentina. In this report, five outbreaks of spontaneous intoxications were investigated. Several indole-diterpene alkaloids were identified in Poa huecu and Festuca argentina including the known tremorgen terpendole C and are likely the cause of "Mal de Huecú" disease.

A Satellite dsRNA Attenuates the Induction of Helper Virus-Mediated Symptoms in Aspergillus flavus

Aspergillus flavus is an important fungal pathogen of animals and plants. Previously, we reported a novel partitivirus, Aspergillus flavus partitivirus 1 (AfPV1), infecting A. flavus. In this study, we obtained a small double-stranded (ds) RNA segment (734 bp), which is a satellite RNA of the helper virus, AfPV1. The presence of AfPV1 altered the colony morphology, decreased the number of conidiophores, created significantly larger vacuoles, and caused more sensitivity to osmotic, oxidative, and UV stresses in A. flavus, but the small RNA segment could attenuate the above symptoms caused by the helper virus AfPV1 in A. flavus. Moreover, AfPV1 infection reduced the pathogenicity of A. flavus in corn (Zea mays), honeycomb moth (Galleria mellonella), mice (Mus musculus), and the adhesion of conidia to host epithelial cells, and increased conidial death by macrophages. However, the small RNA segment could also attenuate the above symptoms caused by the helper virus AfPV1 in A. flavus, perhaps by reducing the genomic accumulation of the helper virus AfPV1 in A. flavus. We used this model to investigate transcriptional genes regulated by AfPV1 and the small RNA segment in A. flavus, and their role in generating different phenotypes. We found that the pathways of the genes regulated by AfPV1 in its host were similar to those of retroviral viruses. Therefore, some pathways may be of benefit to non-retroviral viral integration or endogenization into the genomes of its host. Moreover, some potential antiviral substances were also found in A. flavus using this system.

Sub-acute feeding study of a tall fescue endophyte in a perennial ryegrass host using mice

Epichloë endophytes in grass associations express a myriad of secondary metabolites which can affect the health of grazing animals and reduce the impact of insect pests on pasture. The ideal endophyte-grass association must have a favourable chemical profile such that the impact on animal health is minimised while the beneficial, deterrent effect on insect pests is maximised. A number of endophyte-perennial ryegrass associations have been successfully commercialised but research is on-going to further improve production in farming systems. Secondary metabolites expressed by endophyte-infected tall fescue include lolines, an animal-safe class of compound which imparts a potent effect on insects. Since endophyte-infected perennial ryegrass does not express lolines, a tall fescue endophyte, AR501, was inoculated into perennial ryegrass in an attempt to improve the insect resistance of this pasture type. In addition to animal safety, it is imperative that consideration is given to the safety of humans consuming animal products derived from livestock grazing the novel pasture. Although pure loline alkaloids have previously been tested on mice it is essential that the entire AR501 endophyte-infected perennial ryegrass matrix is tested since this will result in the exposure of both known and unknown secondary metabolites to mice. Three treatment groups each containing 6 male and 6 female mice were fed diets containing AR501 endophyte-infected perennial ryegrass seed (30%), perennial ryegrass seed containing no endophyte (30%) or a diet without seed (control) for 3 weeks. Mice fed control diet ate more than either of the treatment groups fed a diet containing seed. Male mice fed diet containing Nil endophyte seed ate more than those eating AR501 endophyte-infected perennial ryegrass seed although there was no difference observed in the food intake of female mice. While a few statistically significant differences were observed in the haematology and serum biochemical data, in every instance the difference was restricted to only one gender so is considered unlikely to be of toxicological significance. Mice fed AR501 endophyte-infected perennial ryegrass seed remained healthy throughout the experimental period despite consuming 62,000 mg/kg lolines and 4600 mg/kg peramine per day as well as the wide array of other unknown secondary metabolites expressed by this endophyte. Although animal products may contain additional metabolites as a result of animal metabolism, this experiment raises no food safety concerns for AR501 endophyte-infected perennial ryegrass.

Branching and converging pathways in fungal natural product biosynthesis

In nature, organic molecules with great structural diversity and complexity are synthesized by utilizing a relatively small number of starting materials. A synthetic strategy adopted by nature is pathway branching, in which a common biosynthetic intermediate is transformed into different end products. A natural product can also be synthesized by the fusion of two or more precursors generated from separate metabolic pathways. This review article summarizes several representative branching and converging pathways in fungal natural product biosynthesis to illuminate how fungi are capable of synthesizing a diverse array of natural products.

Near-Infrared Hyperspectral Imaging Pipelines for Pasture Seed Quality Evaluation: An Overview

Near-infrared (800–2500 nm; NIR) spectroscopy coupled to hyperspectral imaging (NIR-HSI) has greatly enhanced its capability and thus widened its application and use across various industries. This non-destructive technique that is sensitive to both physical and chemical attributes of virtually any material can be used for both qualitative and quantitative analyses. This review describes the advancement of NIR to NIR-HSI in agricultural applications with a focus on seed quality features for agronomically important seeds. NIR-HSI seed phenotyping, describing sample sizes used for building high-accuracy calibration and prediction models for full or selected wavelengths of the NIR region, is explored. The molecular interpretation of absorbance bands in the NIR region is difficult; hence, this review offers important NIR absorbance band assignments that have been reported in literature. Opportunities for NIR-HSI seed phenotyping in forage grass seed are described and a step-by-step data-acquisition and analysis pipeline for the determination of seed quality in perennial ryegrass seeds is also presented.

A Metabolomic Study of Epichloë Endophytes for Screening Antifungal Metabolites

Epichloë endophytes, fungal endosymbionts of Pooidae grasses, are commonly utilized in forage and turf industries because they produce beneficial metabolites that enhance resistance against environmental stressors such as insect feeding and disease caused by phytopathogen infection. In pastoral agriculture, phytopathogenic diseases impact both pasture quality and animal production. Recently, bioactive endophyte strains have been reported to secrete compounds that significantly inhibit the growth of phytopathogenic fungi in vitro. A screen of previously described Epichloë-produced antifeedant and toxic alkaloids determined that the antifungal bioactivity observed is not due to the production of these known metabolites, and so there is a need for methods to identify new bioactive metabolites. The process described here is applicable more generally for the identification of antifungals in new endophytes. This study aims to characterize the fungicidal potential of novel, ‘animal friendly’ Epichloë endophyte strains NEA12 and NEA23 that exhibit strong antifungal activity using an in vitro assay. Bioassay-guided fractionation, followed by metabolite analysis, identified 61 metabolites that, either singly or in combination, are responsible for the observed bioactivity. Analysis of the perennial ryegrass-endophyte symbiota confirmed that NEA12 and NEA23 produce the prospective antifungal metabolites in symbiotic association and thus are candidates for compounds that promote disease resistance in planta. The “known unknown” suite of antifungal metabolites identified in this study are potential biomarkers for the selection of strains that enhance pasture and turf production through better disease control.

Metabolic Potential of Epichloë Endophytes for Host Grass Fungal Disease Resistance

Asexual species of the genus Epichloë (Clavicipitaceae, Ascomycota) form endosymbiotic associations with Pooidae grasses. This association is important both ecologically and to the pasture and turf industries, as the endophytic fungi confer a multitude of benefits to their host plant that improve competitive ability and performance such as growth promotion, abiotic stress tolerance, pest deterrence and increased host disease resistance. Biotic stress tolerance conferred by the production of bioprotective metabolites has a critical role in an industry context. While the known antimammalian and insecticidal toxins are well characterized due to their impact on livestock welfare, antimicrobial metabolites are less studied. Both pasture and turf grasses are challenged by many phytopathogenic diseases that result in significant economic losses and impact livestock health. Further investigations of Epichloë endophytes as natural biocontrol agents can be conducted on strains that are safe for animals. With the additional benefits of possessing host disease resistance, these strains would increase their commercial importance. Field reports have indicated that pasture grasses associated with Epichloë endophytes are superior in resisting fungal pathogens. However, only a few antifungal compounds have been identified and chemically characterized, and these from sexual (pathogenic) Epichloë species, rather than those utilized to enhance performance in turf and pasture industries. This review provides insight into the various strategies reported in identifying antifungal activity from Epichloë endophytes and, where described, the associated antifungal metabolites responsible for the activity.

Novel Alkaloids from Marine Actinobacteria: Discovery and Characterization

The marine environment is an excellent resource for natural products with therapeutic potential. Its microbial inhabitants, often associated with other marine organisms, are specialized in the synthesis of bioactive secondary metabolites. Similar to their terrestrial counterparts, marine Actinobacteria are a prevalent source of these natural products. Here, we discuss 77 newly discovered alkaloids produced by such marine Actinobacteria between 2017 and mid-2021, as well as the strategies employed in their elucidation. While 12 different classes of alkaloids were unraveled, indoles, diketopiperazines, glutarimides, indolizidines, and pyrroles were most dominant. Discoveries were mainly based on experimental approaches where microbial extracts were analyzed in relation to novel compounds. Although such experimental procedures have proven useful in the past, the methodologies need adaptations to limit the chance of compound rediscovery. On the other hand, genome mining provides a different angle for natural product discovery. While the technology is still relatively young compared to experimental screening, significant improvement has been made in recent years. Together with synthetic biology tools, both genome mining and extract screening provide excellent opportunities for continued drug discovery from marine Actinobacteria.

A novel chemical marker of tremorgenic mycotoxicosis detected by gas-chromatography/mass-spectrometry

Tremorgenic mycotoxicosis can arise from dietary exposure to secondary metabolite products of various fungal species, particularly those from the Penicillium genus. Although general toxin screens often rely on gas chromatography-mass spectrometry (GC/MS) and well-developed mass spectral library databases, two principal representative Penicillium mycotoxins, roquefortine and penitrem A, are unamenable to GC/MS owing to high molecular weights, low volatilities and/or high thermal instabilities. Reliance on GC/MS screens alone could therefore inadvertently result in failure to collect evidence of exposure to such tremorgenic mycotoxins. In this report we describe a newly discovered tremorgenic marker compound (TMC), the presence of which correlates highly with conclusive exposure to Penicillium toxins in explanation of clinical manifestations of tremorgenic mycotoxicosis. According to detailed mass spectral deconvolution, the compound is 210.0892 molecular weight, and amenable to GC/MS whether chemically underivatized or derivatized by methylation or trimethylsilylation. 1D and 2D NMR (nuclear magnetic resonance) studies on the isolated compound determined the TMC to be the Penicillium product terrestric acid, C11H14O4, which matches the molecular formula determined by high resolution mass spectrometry and thus provides an excellent target for assessment of mycotoxicosis by GC/MS.

The Known Antimammalian and Insecticidal Alkaloids Are Not Responsible for the Antifungal Activity of Epichloë Endophytes

Asexual Epichloë sp. endophytes in association with pasture grasses produce agronomically important alkaloids (e.g., lolitrem B, epoxy-janthitrems, ergovaline, peramine, and lolines) that exhibit toxicity to grazing mammals and/or insect pests. Novel strains are primarily characterised for the presence of these compounds to ensure they are beneficial in an agronomical setting. Previous work identified endophyte strains that exhibit enhanced antifungal activity, which have the potential to improve pasture and turf quality as well as animal welfare through phytopathogen disease control. The contribution of endophyte-derived alkaloids to improving pasture and turf grass disease resistance has not been closely examined. To assess antifungal bioactivity, nine Epichloë related compounds, namely peramine hemisulfate, n-formylloline-d3, n-acetylloline hydrochloride, lolitrem B, janthitrem A, paxilline, terpendole E, terpendole C, and ergovaline, and four Claviceps purpurea ergot alkaloids, namely ergotamine, ergocornine, ergocryptine, and ergotaminine, were tested at concentrations higher than observed in planta in glasshouse and field settings using in vitro agar well diffusion assays against three common pasture and turf phytopathogens, namely Ceratobasidium sp., Drechslera sp., and Fusarium sp. Visual characterisation of bioactivity using pathogen growth area, mycelial density, and direction of growth indicated no inhibition of pathogen growth. This was confirmed by statistical analysis. The compounds responsible for antifungal bioactivity of Epichloë endophytes hence remain unknown and require further investigation.

Asymmetric Total Synthesis of Indole Diterpenes Paspalicine, Paspalinine, and Paspalinine-13-ene

Paspaline-derived indole diterpenes (IDTs) are structurally complex mycotoxins with unique tremorgenic activity. Reported are asymmetric total syntheses of three paspaline-derived IDTs paspalicine, paspalinine and paspalinine-13-ene. Our synthesis features a green Achmatowicz rearrangement/bicycloketalization for the efficient construction of FG rings (75 % yield) and a cascade ring-closing metathesis of dienyne for highly regioselective formation of CD rings (72 % yield). Other highlights include four palladium-mediated reactions (Stille, aza-Wacker, Suzuki, and Heck) to forge the BE rings and the installation of two continuous all-carbon quaternary stereocenters via reductive ring-opening of cyclopropane and α-methylation of the conjugate ester. Our new synthetic strategy is expected to be applicable to the chemical synthesis of other paspaline-derived IDTs and will facilitate the bioactivity studies of these agriculturally and pharmacologically important IDTs.

The role of mycotoxins in neurodegenerative diseases: current state of the art and future perspectives of research

Mycotoxins are fungal metabolites that can cause various diseases in humans and animals. The adverse health effects of mycotoxins such as liver failure, immune deficiency, and cancer are well-described. However, growing evidence suggests an additional link between these fungal metabolites and neurodegenerative diseases. Despite the wealth of these initial reports, reliable conclusions are still constrained by limited access to human patients and availability of suitable cell or animal model systems. This review summarizes knowledge on mycotoxins associated with neurodegenerative diseases and the assumed underlying pathophysiological mechanisms. The limitations of the common in vivo and in vitro experiments to identify the role of mycotoxins in neurotoxicity and thereby in neurodegenerative diseases are elucidated and possible future perspectives to further evolve this research field are presented.

Roquefortine C in blue-veined and soft-ripened Cheeses in the USA

Certain fungi can produce secondary metabolites that are toxic, mycotoxins. Two groups of cheeses where fungi are used for ripening are the blue-veined cheeses (Penicillium roqueforti) and the "soft-ripened" cheeses (P. camemberti). An enzyme-linked immunosorbent assay was used to screen for the mycotoxin roquefortine C (ROQC) in 202 samples of cheeses sold in the United States. Of these 152 were blue-veined cheeses, 46 were soft-ripened cheeses and 4 were other varieties of mould-ripened cheeses. ROQC was not detected in any of the soft-ripened cheeses, at a limit of detection of 1.8 µg/kg. ROQC was found in 151 of 152 blue-veined cheeses. The maximum level found was 6,630 µg/kg (median 903 µg/kg, average of positives 1430 µg/kg, limit of quantitation 6.9 µg/kg). These levels are consistent with the levels found previously in blue-veined cheeses in the United Kingdom and Europe, which have generally been considered non-hazardous for human consumption.

Unraveling the Ergot Alkaloid and Indole Diterpenoid Metabolome in the Claviceps purpurea Species Complex Using LC-HRMS/MS Diagnostic Fragmentation Filtering

The plant parasitic fungus Claviceps purpurea sensu lato produces sclerotia containing toxic ergot alkaloids and uncharacterized indole diterpenoids in grasses including cereals. The aim of this study was to detect as many peptide ergot alkaloids and indole diterpenoids in ergot sclerotia as possible by using a liquid chromatography-high-resolution mass spectrometry (LC-HRMS/MS) approach and applying filtering of diagnostic fragment ions for data extraction. The sample set consisted of 66 Claviceps sclerotia from four different geographic locations in southeastern Norway as well as Saskatchewan, Canada. The host plants included both wild grasses and important cereal grains such as rye. DNA sequencing showed that the sclerotia were from three Claviceps species, i.e., Claviceps purpurea sensu stricto (s.s.), Claviceps humidiphila, and Claviceps arundinis (former C. purpurea genotypes G1, G2, and G2a, respectively). All sclerotia from cereal grains were from C. purpurea s.s. Diagnostic fragment filtering was based on detecting specific product ions in MS/MS data sets that are well-conserved across the different ergot alkaloid subgroups and indole diterpenoids of the paspaline/paxilline type. The approach extracted mass spectra from 67 peptide ergot alkaloids (including C-8 epimers and lactam variants) and five indole diterpenoids. In addition, three clavines were detected by using targeted analysis. The sum of the peak areas for ergot alkaloids, which have been assigned as "major" analogues by the European Food Safety Authority (ergometrine, ergosine, ergotamine, α-ergocryptine, ergocornine, ergocristine, and their 8-S epimers), accounted for at least 50% of the extracted total ergot alkaloid metabolome. Univariate and multivariate statistical analyses showed that several of the alkaloids were specific for certain species within the C. purpurea species complex and could be used as chemotaxonomic markers for species assignment.

Global Changes in Asexual Epichloë Transcriptomes during the Early Stages, from Seed to Seedling, of Symbiotum Establishment

Asexual Epichloë fungi are strictly seed-transmitted endophytic symbionts of cool-season grasses and spend their entire life cycle within the host plant. Endophyte infection can confer protective benefits to its host through the production of bioprotective compounds. Inversely, plants provide nourishment and shelter to the resident endophyte in return. Current understanding of the changes in global gene expression of asexual Epichloë endophytes during the early stages of host-endophyte symbiotum is limited. A time-course study using a deep RNA-sequencing approach was performed at six stages of germination, using seeds infected with one of three endophyte strains belonging to different representative taxa. Analysis of the most abundantly expressed endophyte genes identified that most were predicted to have a role in stress and defence responses. The number of differentially expressed genes observed at early time points was greater than those detected at later time points, suggesting an active transcriptional reprogramming of endophytes at the onset of seed germination. Gene ontology enrichment analysis revealed dynamic changes in global gene expression consistent with the developmental processes of symbiotic relationships. Expression of pathway genes for biosynthesis of key secondary metabolites was studied comprehensively and fuzzy clustering identified some unique expression patterns. Furthermore, comparisons of the transcriptomes from three endophyte strains in planta identified genes unique to each strain, including genes predicted to be associated with secondary metabolism. Findings from this study highlight the importance of better understanding the unique properties of individual endophyte strains and will serve as an excellent resource for future studies of host-endophyte interactions.

Aspergillus derived mycotoxins in food and the environment: Prevalence, detection, and toxicity

Aspergillus species are the paramount ubiquitous fungi that contaminate various food substrates and produce biochemicals known as mycotoxins. Aflatoxins (AFTs), ochratoxin A (OTA), patulin (PAT), citrinin (CIT), aflatrem (AT), secalonic acids (SA), cyclopiazonic acid (CPA), terrein (TR), sterigmatocystin (ST) and gliotoxin (GT), and other toxins produced by species of Aspergillus plays a major role in food and human health. Mycotoxins exhibited wide range of toxicity to the humans and animal models even at nanomolar (nM) concentration. Consumption of detrimental mycotoxins adulterated foodstuffs affects human and animal health even trace amounts. Bioaerosols consisting of spores and hyphal fragments are active elicitors of bronchial irritation and allergy, and challenging to the public health. Aspergillus is the furthermost predominant environmental contaminant unswervingly defile lives with a 40-90 % mortality risk in patients with conceded immunity. Genomics, proteomics, transcriptomics, and metabolomics approaches useful for mycotoxins' detection which are expensive. Antibody based detection of toxins chemotypes may result in cross-reactivity and uncertainty. Aptamers (APT) are single stranded DNA (ssDNA/RNA), are specifically binds to the target molecules can be generated by systematic evolution of ligands through exponential enrichment (SELEX). APT are fast, sensitive, simple, in-expensive, and field-deployable rapid point of care (POC) detection of toxins, and a better alternative to antibodies.

Study of enzymatic activity in human neuroblastoma cells SH-SY5Y exposed to zearalenone's derivates and beauvericin

Beauvericin (BEA), α-zearalenol (α-ZEL) and β-zearalenol (β-ZEL), are produced by several Fusarium species that contaminate cereal grains. These mycotoxins can cause cytotoxicity and neurotoxicity in various cell lines and they are also capable of produce oxidative stress at molecular level. However, mammalian cells are equipped with a protective endogenous antioxidant system formed by no-enzymatic antioxidant and enzymatic protective systems such as glutathione peroxidase (GPx), glutathione S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD). The aim of this study was evaluating the effects of α-ZEL, β-ZEL and BEA, on enzymatic GPx, GST, CAT and SOD activity in human neuroblastoma cells using the SH-SY5Y cell line, over 24 h and 48 h with different treatments at the following concentration range: from 1.56 to 12.5 μM for α-ZEL and β-ZEL, from 0.39 to 2.5 μM for BEA, from 1.87 to 25 μM for binary combinations and from 3.43 to 27.5 μM for tertiary combination. SH-SY5Y cells exposed to α-ZEL, β-ZEL and BEA revealed an overall increase in the activity of i) GPx, after 24 h of exposure up to 24-fold in individual treatments and 15-fold in binary combination; ii) GST after 24 h of exposure up to 10-fold (only in combination forms), and iii) SOD up to 3.5- and 5-fold in individual and combined treatment, respectively after 48 h of exposure. On the other hand, CAT activity decreased significantly in all treatments up to 92% after 24 h except for β-ZEL + BEA, which revealed the opposite.

The Impact of Alkaloid-Producing Epichloë Endophyte on Forage Ryegrass Breeding: A New Zealand Perspective

For 30 years, forage ryegrass breeding has known that the germplasm may contain a maternally inherited symbiotic Epichloë endophyte. These endophytes produce a suite of secondary alkaloid compounds, dependent upon strain. Many produce ergot and other alkaloids, which are associated with both insect deterrence and livestock health issues. The levels of alkaloids and other endophyte characteristics are influenced by strain, host germplasm, and environmental conditions. Some strains in the right host germplasm can confer an advantage over biotic and abiotic stressors, thus acting as a maternally inherited desirable ‘trait’. Through seed production, these mutualistic endophytes do not transmit into 100% of the crop seed and are less vigorous than the grass seed itself. This causes stability and longevity issues for seed production and storage should the ‘trait’ be desired in the germplasm. This makes understanding the precise nature of the relationship vitally important to the plant breeder. These Epichloë endophytes cannot be ‘bred’ in the conventional sense, as they are asexual. Instead, the breeder may modulate endophyte characteristics through selection of host germplasm, a sort of breeding by proxy. This article explores, from a forage seed company perspective, the issues that endophyte characteristics and breeding them by proxy have on ryegrass breeding, and outlines the methods used to assess the ‘trait’, and the application of these through the breeding, production, and deployment processes. Finally, this article investigates opportunities for enhancing the utilisation of alkaloid-producing endophytes within pastures, with a focus on balancing alkaloid levels to further enhance pest deterrence and improving livestock outcomes.

Marine-derived fungi as a source of bioactive indole alkaloids with diversified structures

Marine-derived fungi are well known as rich sources of bioactive natural products. Growing evidences indicated that indole alkaloids, isolated from a variety of marine-derived fungi, have attracted considerable attention for their diverse, challenging structural complexity and promising bioactivities, and therefore, indole alkaloids have potential to be pharmaceutical lead compounds. Systemic compilation of the relevant literature. In this review, we demonstrated a comprehensive overview of 431 new indole alkaloids from 21 genera of marine-derived fungi with an emphasis on their structures and bioactivities, covering literatures published during 1982-2019.

Ascandinines A-D, Indole Diterpenoids, from the Sponge-Derived Fungus Aspergillus candidus HDN15-152

Four new indole diterpenoids, ascandinines A-D (1-4), were isolated from an Antarctic sponge-derived fungus Aspergillus candidus HDN15-152. Their structures, including absolute configurations, were established based on NMR data, computational calculations, and biosynthetic considerations. Ascandinine A (1) possesses an unprecedented 2-oxabicyclo[2.2.2]octan-3-ol motif embedded in a pentacyclic ring system, while compounds 2-4 represent a rare type of indole diterpenoid featuring the 6/5/5/6/6/6/6-fused ring system. Compound 3 displayed anti-influenza virus A (H1N1) activity with an IC₅₀ value of 26 μM, while compound 4 showed cytotoxicity against HL-60 cells with an IC₅₀ value of 7.8 μM.

Olive Oil Lignan (+)-Acetoxypinoresinol Peripheral Motor and Neuronal Protection against the Tremorgenic Mycotoxin Penitrem A Toxicity via STAT1 Pathway

Penitrem A, PA, is an indole diterpene alkaloid produced by several fungal species. PA acts as a selective Ca²⁺-dependent K-channels (Maxi-K, BK) antagonist in brain, causing motor system dysfunctions including tremors and seizures. However, its molecular mechanism at the peripheral nervous system (PNS) is still ambiguous. The Mediterranean diet key ingredient extra-virgin olive oil (EVOO) provides a variety of minor bioactive phenolics. (+)-Pinoresinol (PN) and (+)-1-acetoxypinoresinol (AC) are naturally occurring lignans in EVOO with diverse biological activities. AC exclusively occurs in EVOO, unlike PN, which occurs in several plants. Results suggest that PA neurotoxicity molecular mechanism is mediated, in part, through distortion of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway. PA selectively activated the STAT1 pathway, independently of the interferon-γ (IFN-γ) pathway, in vitro in Schwann cells and in vivo in Swiss albino mice sciatic nerves. Preliminary in vitro screening of an EVOO phenolic compounds library for the ability to reverse PA toxicity on Schwann cells revealed PN and AC as potential hits. In a Swiss albino mouse model, AC significantly minimized the fatality after intraperitoneal administration of PA fatal doses and normalized most biochemical factors by modulating the STAT1 expression. The olive lignan AC is a novel lead that can prevent the neurotoxicity of food-contaminating tremorgenic indole alkaloid mycotoxins.

Ruminant Mycotoxicosis: An Update

This review focuses on factors associated with mold production in feedstuffs and major mycotoxins affecting ruminants in North America. Ruminants are often considered less sensitive to mycotoxins owing to rumen microflora metabolism to less toxic compounds. However, ruminants occupy wide agricultural niches that expose animals to diverse toxins under widely different environmental and nutritional conditions. Often the moldy and potentially highly contaminated feeds end up at feedlots. Less than optimal feedstuffs creating suboptimal rumen microbial flora could result in decreased ruminal capacity to detoxify certain mycotoxins and adverse effects. Numerous mycotoxins and clinical effects in ruminants are discussed.

Chemical repertoire and biosynthetic machinery of the Aspergillus flavus secondary metabolome: A review

Filamentous fungi represent a rich source of extrolites, including secondary metabolites (SMs) comprising a great variety of astonishing structures and interesting bioactivities. State-of-the-art techniques in genome mining, genetic manipulation, and secondary metabolomics have enabled the scientific community to better elucidate and more deeply appreciate the genetic and biosynthetic chemical arsenal of these microorganisms. Aspergillus flavus is best known as a contaminant of food and feed commodities and a producer of the carcinogenic family of SMs, aflatoxins. This fungus produces many SMs including polyketides, ribosomal and nonribosomal peptides, terpenoids, and other hybrid molecules. This review will discuss the chemical diversity, biosynthetic pathways, and biological/ecological role of A. flavus SMs, as well as their significance concerning food safety and security.

Fatal stagger poisoning by consumption of Festuca argentina (Speg.) Parodi in goats from Argentine Patagonia

The present study describes the spontaneous and experimental poisoning of goats by Festuca argentina in Argentine Patagonia. In April 2017, eight seven-month-old Creole male goats were accidentally introduced into a paddock that contained F. argentina. After four days, two of the goats were found dead and four out of the six remaining goats were clinically affected. Two of the latter had to be later euthanized in extremis. The main clinical signs were progressive nervous signs, starting with moderate muscle tremors, wide-based stance and ataxia. Postmortem examination was performed on the two euthanized goats. Epidermal fragments of F. argentina were found in the rumen samples from the necropsied goats and the fecal samples from the four affected goats. For the experimental poisoning, fresh sheaths of F. argentina collected from the paddock were offered to two goats at 10 g/kg body weight for 3 days. After 24-36 h, both animals exhibited severe muscle tremors, reluctance to move, tetanic convulsions, and opisthotonus. In both the spontaneously and experimentally poisoned goats, gross lesions were similar and consisted of dehydration, petechial hemorrhages in the epicardium and congestion. The main microscopic findings consisted of degeneration and loss of Purkinje cells and torpedoes in the granular layer of the cerebellum. The F. argentina sheaths collected from the pasture were found to contain tremorgenic indole-diterpene alkaloids. Taken together, the results of the present study suggest that the tremorgenic syndrome observed in the spontaneously poisoned goats was due to poisoning by F. argentina.

Development and characterisation of a monoclonal antibody to detect the mycotoxin roquefortine C

Roquefortine, also known as roquefortine C (ROQC) is a fungal secondary metabolite (mycotoxin) that is produced by some of the same Penicillia as the tremorgen penitrem-A (PEN-A). The two mycotoxins have been linked to sporadic cases of toxicosis in dogs, cattle, and humans, leading some to consider ROQC as a biomarker of PEN-A. Reported here are the development of a monoclonal antibody (mAb) and associated competitive enzyme-linked immunosorbent assay (ELISA) for the screening of ROQC in extracts of nuts (nut "milks"), and dog serum. The ELISA was sensitive for ROQC, with a level of 0.117 ng ml^-1 inhibiting colour development by 50% (IC₅₀), a limit of detection of 0.026 ng ml^-1, and a dynamic range (IC₂₀ to IC₈₀) of 0.038 to 0.289 ng ml^-1 in buffer. The assay was tolerant to significant levels of methanol. Recoveries from 4 types of nut milks spiked over the range of 0.25 to 2 ng ml^-1 were in the range of 83.5% to 116%. A small survey of commercial nut "milks" and "creamers" indicated 4 of 35 samples contained ROQC at levels so low that they are unlikely to be significant to human health (<0.6 ng ml^-1). The assay was also applied to canine serum. Recoveries from serum spiked over the range of 0.2 to 5 ng ml^-1 ranged from 98.1% to 123%. The results suggest the ELISA can be applied to the screening of food products, such as nut extracts, as well as for the screening of serum from dogs suspected to be suffering from mycotoxin-induced tremors.

Molecular mechanisms in grass-Epichloë interactions: towards endophyte driven farming to improve plant fitness and immunity

All plants harbor many microbial species including bacteria and fungi in their tissues. The interactions between the plant and these microbes could be symbiotic, mutualistic, parasitic or commensalistic. Mutualistic microorganisms are endophytic in nature and are known to play a role in plant growth, development and fitness. Endophytes display complex diversity depending upon the agro-climatic conditions and this diversity could be exploited for crop improvement and sustainable agriculture. Plant-endophyte partnerships are highly specific, several genetic and molecular cascades play a key role in colonization of endophytes in host plants leading to rapid changes in host and endophyte metabolism. This results in the accumulation of secondary metabolites, which play an important role in plant defense against biotic and abiotic stress conditions. Alkaloids are one of the important class of metabolites produced by Epichloë genus and other related classes of endophytes and confer protection against insect and mammalian herbivory. In this context, this review discusses the evolutionary aspects of the Epichloë genus along with key molecular mechanisms determining the lifestyle of Epichloë endophytes in host system. Novel hypothesis is proposed to outline the initial cellular signaling events during colonization of Epichloë in cool season grasses. Complex clustering of alkaloid biosynthetic genes and molecular mechanisms involved in the production of alkaloids have been elaborated in detail. The natural defense and advantages of the endophyte derived metabolites have also been extensively discussed. Finally, this review highlights the importance of endophyte-arbitrated plant immunity to develop novel approaches for eco-friendly agriculture.

Alkaloids from Marine Fungi: Promising Antimicrobials

Resistance of pathogenic microorganisms against antimicrobials is a major threat to contemporary human society. It necessitates a perpetual influx of novel antimicrobial compounds. More specifically, Gram⁻ pathogens emerged as the most exigent danger. In our continuing quest to search for novel antimicrobial molecules, alkaloids from marine fungi show great promise. However, current reports of such newly discovered alkaloids are often limited to cytotoxicity studies and, moreover, neglect to discuss the enigma of their biosynthesis. Yet, the latter is often a prerequisite to make them available through sufficiently efficient processes. This review aims to summarize novel alkaloids with promising antimicrobial properties discovered in the past five years and produced by marine fungi. Several discovery strategies are summarized, and knowledge gaps in biochemical production routes are identified. Finally, links between the structure of the newly discovered molecules and their activity are proposed. Since 2015, a total of 35 new antimicrobial alkaloids from marine fungi were identified, of which 22 showed an antibacterial activity against Gram⁻ microorganisms. Eight of them can be classified as narrow-spectrum Gram⁻ antibiotics. Despite this promising ratio of novel alkaloids active against Gram⁻ microorganisms, the number of newly discovered antimicrobial alkaloids is low, due to the narrow spectrum of discovery protocols that are used and the fact that antimicrobial properties of newly discovered alkaloids are barely characterized. Alternatives are proposed in this review. In conclusion, this review summarizes novel findings on antimicrobial alkaloids from marine fungi, shows their potential as promising therapeutic candidates, and hints on how to further improve this potential.

Mycotoxicoses in veterinary medicine: Aspergillosis and penicilliosis

Molds and mycotoxins are contaminants of animal feed causing spoilage and clinical intoxication. Animal exposure to mycotoxins reflects diet composition with major differences occurring between animals kept predominantly of pastures, i.e. ruminants and horses, and those consuming formulated feed like pigs and poultry. Mixed feeds are composed of several ingredients, often sourced from different continents. Subsequently, practitioners may confront endemic diseases and signs of toxin exposure related to toxins imported accidentally with contaminated feed materials from other countries and continents. Mycotoxins comprise more than 300 to 400 different chemicals causing a variety of clinical symptoms. Mycotoxin exposure causes major economic losses due to reduced performance, impaired feed conversion and fertility, and increased susceptibility to environmental stress and infectious diseases. In acute cases, clinical symptoms following mycotoxin ingestion are often non-specific, hindering an immediate diagnosis. Furthermore, most mold species produce more than one toxin, and feed commodities are regularly contaminated with various mold species resulting in complex mixtures of toxins in formulated feeds. The effects of these different toxins may be additive, depending on the level and time of exposure, and the intensity of the clinical symptoms based on age, health, and nutritional status of the exposed animal(s). Threshold levels of toxicity are difficult to define and discrepancies between analytical data and clinical symptoms are common in daily practice. This review aims to provide an overview of Aspergillus and Penicillium toxins that are frequently found in feed commodities and discusses their effects on animal health and productivity.

Identification and Distribution of Novel Metabolites of Lolitrem B in Mice by High-Resolution Mass Spectrometry

Lolitrem B is the most potent indole-diterpene mycotoxin produced by Epichloë festucae var. lolii (termed LpTG-1), with severe intoxication cases reported in livestock. To date, there are no in vivo metabolism studies conducted for the mycotoxin. A mouse model assay established for assessing toxicity of indole-diterpenes was used to investigate metabolic products of lolitrem B. Mice were administered lolitrem B at 0.5 and 2.0 mg/kg body weight (b.wt) intraperitoneally before body and brain tissues were collected at 6 h and 24 h post-treatment. Samples were cryoground and subjected to a biphasic or monophasic extraction. The aqueous and lipophilic phases were analysed using liquid chromatography high-resolution mass spectrometry (LC–HRMS); data analysis was performed with Compound Discoverer™ software. A total of 10 novel phase I metabolic products were identified in the lipophilic phase and their distribution in the liver, kidney and various brain regions are described. The biotransformation products of lolitrem B were found to be present in low levels in the brain. Based on structure–activity postulations, six of these may contribute towards the protracted tremors exhibited by lolitrem B-exposed animals.