Large-scale production of selected type A trichothecenes: the use of HT-2 toxin and T-2 triol as precursors for the synthesis of d 3-T-2 and d 3-HT-2 toxin

Biosynthesis of the Isocoumarin Derivatives Fusamarins is Mediated by the PKS8 Gene Cluster in Fusarium

Fusarium mangiferae causes the mango malformation disease (MMD) on young mango trees and seedlings resulting in economically significant crop losses. In addition, F. mangiferae produces a vast array of secondary metabolites (SMs), including mycotoxins that may contaminate the harvest. Their production is tightly regulated at the transcriptional level. Here, we show that lack of the H3 K9-specific histone methyltransferase, FmKmt1, influences the expression of the F. mangiferae polyketide synthase (PKS) 8 (FmPKS8), a so far cryptic PKS. By a combination of reverse genetics, untargeted metabolomics, bioinformatics and chemical analyses including structural elucidation, we determined the FmPKS8 biosynthetic gene cluster (BGC) and linked its activity to the production of fusamarins (FMN), which can be structurally classified as dihydroisocoumarins. Functional characterization of the four FMN cluster genes shed light on the biosynthetic pathway. Cytotoxicity assays revealed moderate toxicities with IC50 values between 1 and 50 μM depending on the compound.

Semisynthetic Approach toward Biologically Active Derivatives of Phenylspirodrimanes from S. chartarum

The phenylspirodrimanes (PSDs) from Stachybotrys chartarum represent a structurally diverse group of meroterpenoids, which, on the one hand, exhibit a structural exclusivity since their occurrence is not known for any other species and, on the other hand, offer access to chemically and biologically active compounds. In this study, phenylspirodrimanes 1-3 were isolated from S. chartarum and their water-mediated Cannizzaro-type transformation was investigated using quantum chemical DFT calculations substantiated by LC-MS and NMR experiments. Considering the inhibitory activity of PSDs against proteolytic enzymes and their modulatory effect on plasminogen, PSDs 1-3 were used as a starting material for the synthesis of their corresponding biologically active lactams. To access the library of the PSD derivatives and screen them against physiologically relevant serine proteases, a microscale semisynthetic approach was developed. This allowed us to generate the library of 35 lactams, some of which showed the inhibitory activity against physiologically relevant serine proteases such as thrombin, FXIIa, FXa, and trypsin. Among them, the agmatine-derived lactam 16 showed the highest inhibitory activity against plasma coagulation factors and demonstrated the anticoagulant activity in two plasma coagulation tests. The semisynthetic lactams were significantly less toxic compared to their parental natural PSDs.

Detection of Mycotoxins in Highly Matrix-Loaded House-Dust Samples by QTOF-HRMS, IM-QTOF-HRMS, and TQMS: Advantages and Disadvantages

The analysis of (trace) contaminants in environmental samples represents an important tool for exposure assessment and for the evaluation of potential risks to human health. Currently, mass spectrometric detection using triple quadrupole (TQMS) systems is the established method of choice. However, screening methods using high resolution mass spectrometry (HRMS) find increasing application as they provide advantages such as enhanced selectivity. A complex composition of environmental samples is known to have enormous effects on mass analyzers. The present work therefore compares the impact of a highly matrix-loaded sample material like house-dust on the performance of mass spectrometric detection of the emerging indoor contaminant group of mycotoxins by quadrupole time-of-flight (QTOF) and TQMS after ultrahigh-performance liquid chromatographic separation. Furthermore, the role of ionization efficiencies of different ion sources in instrument sensitivity was compared using an electrospray ionization source and a newly developed heated electrospray ion source (Bruker VIP-HESI) during QTOF experiments. Finally, it was evaluated whether an additional dimension of separation enables increased sensitivity in QTOF-HRMS detection by applying mycotoxins in house-dust to an (trapped) ion mobility spectrometry instrument. The sensitivity of the QTOF detection was positively influenced by the application of the VIP-HESI ion source, and overall HRMS instruments provided enhanced selectivity resulting in simplified data evaluation compared to the TQMS. However, all performed experiments revealed strong signal suppression due to matrix components. QTOF results showed more severe effects, enabling a more sensitive detection of mycotoxins in house-dust by applying TQMS detection.

Insights into Ergochromes of the Plant Pathogen Claviceps purpurea

Claviceps purpurea is an ergot fungus known for its neurotropic alkaloids, which have been identified as the main cause of ergotism, a livestock and human disease triggered by ergot consumption. Tetrahydroxanthone dimers, the so-called ergopigments, presumably also contribute to this toxic effect. Overexpression of the cluster-specific transcription factor responsible for the formation of these pigments in C. purpurea led to the isolation of three new metabolites (8-10). The new pigments were characterized utilizing HRMS, NMR techniques, and CD spectroscopy and shown to be xanthone dimers. Secalonic acid A and its 2,4'- and 4,4'-linked isomers were also isolated, and their absolute configuration was investigated. The contribution of secalonic acid A, its isomers, and new metabolites to the toxicity of C. purpurea was investigated in HepG2 and CCF-STTG1 cells. Along with cytotoxic properties, secalonic acid A was found to inhibit topoisomerase I and II activity.

Efflux at the Blood-Brain Barrier Reduces the Cerebral Exposure to Ochratoxin A, Ochratoxin α, Citrinin and Dihydrocitrinone

Recent studies have implied that environmental toxins, such as mycotoxins, are risk factors for neurodegenerative diseases. To act directly as neurotoxins, mycotoxins need to penetrate or affect the integrity of the blood-brain barrier, which protects the mammalian brain from potentially harmful substances. As common food and feed contaminants of fungal origin, the interest in the potential neurotoxicity of ochratoxin A, citrinin and their metabolites has recently increased. Primary porcine brain capillary endothelial cells were used to investigate cytotoxic or barrier-weakening effects of ochratoxin A, ochratoxin α, citrinin and dihydrocitrinone. The transfer and transport properties of the mycotoxins across the barrier formed by porcine brain capillary endothelial cell monolayers were analysed using HPLC-MS/MS. High levels of Ochratoxin A caused cytotoxic and barrier-weakening effects, whereas ochratoxin α, citrinin and dihydrocitrinone showed no adverse effects up to 10 µM. Likely due to efflux transporter proteins, the transfer to the brain compartment was much slower than expected from their high lipophilicity. Due to their slow transfer across the blood-brain barrier, cerebral exposure of ochratoxin A, ochratoxin α, citrinin and dihydrocitrinone is low and neurotoxicity is likely to play a subordinate role in their toxicity at common physiological concentrations.

Dried urine spots as sampling technique for multi-mycotoxin analysis in human urine

A simple and effective approach for HPLC-MS/MS based multi-mycotoxin analysis in human urine samples was developed by application of dried urine spots (DUS) as alternative on-site sampling strategy. The newly developed method enables the detection and quantitation of 14 relevant mycotoxins and mycotoxin metabolites, including citrinin (CIT), dihydrocitrinone (DH-CIT), deoxynivalenol (DON), fumonisin B₁ (FB₁), T-2 Toxin (T-2), HT-2 Toxin (HT-2), ochratoxin A (OTA), 2′R-ochratoxin A (2′R-OTA), ochratoxin α (OTα), tenuazonic acid and allo-tenuazonic acid (TeA + allo-TeA), zearalenone (ZEN), zearalanone (ZAN), α-zearalenol (α-ZEL), and β-zearalenol (β-ZEL). Besides the spotting procedure, sample preparation includes enzymatic cleavage of glucuronic acid conjugates and stable isotope dilution analysis. Method validation revealed low limits of detection in the range of pg/mL urine and excellent apparent recovery rates for most analytes. Stability investigation of DUS displayed no or only slight decrease of the analyte concentration over a period of 28 days at room temperature. The new method was applied to the analysis of a set of urine samples (n = 91) from a Swedish cohort. The four analytes, DH-CIT, DON, OTA, and TeA + allo-TeA, could be detected and quantified in amounts ranging from 0.06 to 0.97 ng/mL, 3.03 to 136 ng/mL, 0.013 to 0.434 ng/mL and from 0.36 to 47 ng/mL in 38.5%, 70.3%, 68.1%, and 94.5% of the samples, respectively. Additional analysis of these urine samples with an established dilute and shoot (DaS) approach displayed a high consistency of the results obtained with both methods. However, due to higher sensitivity, a larger number of positive samples were observed using the DUS method consequently providing a suitable approach for human biomonitoring of mycotoxin exposure.

Intestinal Metabolism of α- and β-Glucosylated Modified Mycotoxins T-2 and HT-2 Toxin in the Pig Cecum Model

The type A trichothecene mycotoxins T-2 and HT-2 toxin are fungal secondary metabolites produced by Fusarium fungi, which contaminate food and feed worldwide. Especially as a result of the high toxicity of T-2 toxin and their occurrence together with glucosylated forms in cereal crops, these mycotoxins are of human health concern. Particularly, it is unknown whether and how these modified mycotoxins are metabolized in the gastrointestinal tract and, thus, contribute to the overall toxicity. Therefore, the comparative intestinal metabolism of T-2 and HT-2 toxin glucosides in α and β configuration was investigated using the ex vivo pig cecum model, which mimics the human intestinal metabolism. Regardless of its configuration, the C-3 glycosidic bond was hydrolyzed within 10-20 min, releasing T-2 and HT-2 toxin, which were further metabolized to HT-2 toxin and T-2 triol, respectively. We conclude that T-2 and HT-2 toxin should be evaluated together with their modified forms for risk assessment.

Matrix binding of T-2 toxin: structure elucidation of reaction products and indications on the fate of a relevant food-borne toxin during heating

This study deals with the influence of food matrix components on the degradation of the mycotoxins T-2 toxin (T-2) and HT-2 toxin (HT-2) and with the binding of T-2 to starch during thermal food processing. Both mycotoxins were heated in a simulated food environment and subsequently analyzed via HPLC-HRMS to generate degradation curves and to draw conclusions regarding the thermal degradation under food processing conditions. Thermal degradation increased generally with increasing time and temperature with a maximum degradation rate of 93% (T-2) and 99% (HT-2). Furthermore, HRMS data were exploited to screen the samples for degradation products. In model heating experiments, T-2 was bound to 1-O-methyl-α-D-glucopyranoside, a model compound that was used to simulate starch. The formed reaction products were isolated and identified by NMR, giving detailed insights into a potential binding of T-2 to starch. In the next step, further model heating experiments were performed, which proved the covalent binding of T-2 to starch. Finally, the amount of matrix-bound T-2 was estimated roughly in a semi-quantitative approach in the model heating experiments as well as during cookie-making via GC-MS analysis of the isovaleric acid ester moiety of T-2, released after alkaline hydrolysis.

Thermal stability of T-2 and HT-2 toxins during biscuit- and crunchy muesli-making and roasting

The mycotoxins T-2 and HT-2 toxin are frequently occurring food contaminants which are produced by Fusarium species. Humans and animals are mainly exposed to these substances by the consumption of contaminated oats, maize and wheat. For the production of crunchy muesli, bread and bakery products, these cereals undergo multiple processing steps, including baking, roasting and extrusion cooking. However, the influence of food processing on T-2 and HT-2 toxin levels is to date poorly understood. Thus, the effects of baking and roasting on both mycotoxins were evaluated during biscuit-, crunchy muesli- and toasted oat flakes-production under precise variation of various parameters: heating time and temperature as well as recipe formulation were varied in the range they are applied in the food processing industry. Therefore, oatmeal or flaked oats were artificially contaminated individually with both toxins and processed at the laboratory scale. T-2 toxin generally showed a higher degradation rate than HT-2 toxin. During biscuit-making up to 45% of T-2 toxin and 20% of HT-2 toxin were thermally degraded, showing a dependency on water content, baking time and temperature. The preparation of crunchy muesli yielded no significant toxin degradation which is probably due to the low temperatures applied. Roasting led to a degradation of 32% of T-2 toxin and 24% of HT-2 toxin. Taken together, both mycotoxins are partially degraded during thermal food processing; the degradation rates are influenced by the food composition and processing parameters.

Glucosylation of T-2 and HT-2 toxins using biotransformation and chemical synthesis: Preparation, stereochemistry, and stability

Plant-derived phase II metabolites of T-2 toxin (T2) and HT-2 toxin (HT2) were first described in 2011 and further characterized in the following years. Since then, some efforts have been made to understand their biosynthesis, occurrence, toxicity, toxicokinetics, and finally relevance for consumers. Thus, the probably most important question is whether and how these metabolites contribute to toxicity upon hydrolysis either during food processing or the gastrointestinal passage. To answer this question, firstly, knowledge on the correct stereochemistry of T2 and HT2 glucosides is important as this affects hydrolysis and chemical behavior. So far, contradictory results have been published concerning the number and anomericity of occurring glucosides. For this reason, we set up different strategies for the synthesis of mg-amounts of T2, HT2, and T2 triol glucosides in both α and ß configuration. All synthesized glucosides were fully characterized by NMR spectroscopy as well as mass spectrometry and used as references for the analysis of naturally contaminated food samples to validate or invalidate their natural occurrence. Generally, 3-O-glucosylation was observed with two anomers of HT2 glucoside being present in contaminated oats. In contrast, only one anomer of T2 glucoside was found. The second aspect of this study addresses the stability of the glucosides during thermal food processing. Oat flour was artificially contaminated with T2 and HT2 glucosides individually and extruded at varying initial moisture content and temperature. All four glucosides appear to be more stable during food extrusion than the parent compounds with the glucosidic bond not being hydrolyzed.

Impact of Mechanical and Thermal Energies on the Degradation of T-2 and HT-2 Toxins during Extrusion Cooking of Oat Flour

The type A trichothecenes T-2 toxin (T-2) and HT-2 toxin (HT-2) are naturally occurring toxic food contaminants, with the highest concentrations found in contaminated oats. The influence of thermal food processing on these toxins is poorly understood, and only a few publications address the degradation rates. Therefore, we systematically investigated the degradation of T-2 and HT-2 during both laboratory and industrial-scale extrusion cooking of oats. Extrusion cooking under laboratory conditions was performed with oats fortified with T-2 or HT-2 as well as with naturally contaminated oat flour dust. The experiments were designed according to industrial conditions in terms of temperature, water content, pressure, residence time, and oat content. Flour mixtures containing naturally contaminated oats were used for industrial-scale processing. Degradation rates under laboratory conditions were up to 59.6 ± 1.51 and 47.2 ± 0.53% for T-2 and HT-2, respectively, in fortified extrudates but were decreased to 35.1 ± 1.55 and 22.0 ± 4.68% when naturally contaminated flour samples were used. The results show a higher degradation of T-2 during extrusion cooking than of HT-2. Moisture content, mechanical shear, and temperature showed an impact on the toxin degradation and can be optimized to counteract food contamination.

Multi-mycotoxin analysis using dried blood spots and dried serum spots

In this study, a rapid multi-mycotoxin approach was developed for biomonitoring and quantification of 27 important mycotoxins and mycotoxin metabolites in human blood samples. HPLC-MS/MS detection was used for the analysis of dried serum spots (DSS) and dried blood spots (DBS). Detection of aflatoxins (AFB₁, AFB₂, AFG₁, AFG₂, AFM₁), trichothecenes (deoxynivalenol, DON; DON-3-glucoronic acid, DON-3-GlcA; T-2; HT-2; and HT-2-4-GlcA), fumonisin B₁ (FB₁), ochratoxins (OTA and its thermal degradation product 2'R-OTA; OTα; 10-hydroxychratoxin A, 10-OH-OTA), citrinin (CIT and its urinary metabolite dihydrocitrinone, DH-CIT), zearalenone and zearalanone (ZEN, ZAN), altenuene (ALT), alternariols (AOH; alternariol monomethyl ether, AME), enniatins (EnA, EnA₁, EnB, EnB₁) and beauvericin (Bea) was validated for two matrices, serum (DSS), and whole blood (DBS). HPLC-MS/MS analysis showed signal suppression as well as signal enhancement due to matrix effects. However, for most analytes LOQs in the lower pg/mL range and excellent recovery rate were achieved using matrix-matched calibration. Besides validation of the method, the analyte stability in DBS and DSS was also investigated. Stability is a main issue for some analytes when the dried samples are stored under common conditions at room temperature. Nevertheless, the developed method was applied to DBS samples of a German cohort (n = 50). Besides positive findings of OTA and 2'R-OTA, all samples were positive for EnB. This methodical study establishes a validated multi-mycotoxin approach for the detection of 27 mycotoxins and metabolites in dried blood/serum spots based on a fast sample preparation followed by sensitive HPLC-MS/MS analysis. Graphical Abstract ᅟ.

Cytotoxicity of T-2 and modified T-2 toxins: induction of JAK/STAT pathway in RAW264.7 cells by hepatopancreas and muscle extracts of shrimp fed with T-2 toxin

T-2 can be biotransformed in animal tissues to modified T-2s (mT-2s). Food contaminated with T-2 and/or mT-2s is a hazard to both animals and humans, including the immune system. In this study, Litopenaeus vannamei were fed T-2 orally for 20 d, and hepatopancreas and muscle extracts, T-2, and T-2-glucuronide (T-2-GluA) were added to RAW264.7 in vitro and their effects on the JAK/STAT pathway were examined. STAT2 mRNA gene expression induced by hepatopancreas and muscle extracts was markedly higher compared with that of T-2 or T-2-GluA group. SCOSs, IL-6 and IL-1β mRNA gene expressions induced by hepatopancreas extract were greater than those induced by muscle extract. Muscle extract significantly activated STAT3 phosphorylation but inhibited STAT1 phosphorylation. Activation of the JAK/STAT pathway by hepatopancreas mT-2s was significantly higher than that by muscle extracts. Muscle and hepatopancreas extracts and T-2 also significantly induced IL-6 mRNA gene expression. With reference to phosphorylation levels, significant activation of JAK1 and STAT2 occurred with T-2 and JAK3 by muscle extract, JAK2 by hepatopancreas extract and STAT1 by T-2-GluA. This study showed that both T-2 and mT-2s are cytotoxic but the activation of the JAK/STAT pathway in RAW264.7 cells by T-2 was greater than that by mT-2s in hepatopancreas and muscle extracts from T-2-fed Litopenaeus vannamei.

Blood-Brain Barrier Effects of the Fusarium Mycotoxins Deoxynivalenol, 3 Acetyldeoxynivalenol, and Moniliformin and Their Transfer to the Brain

BACKGROUND

Secondary metabolites produced by Fusarium fungi frequently contaminate food and feed and have adverse effects on human and animal health. Fusarium mycotoxins exhibit a wide structural and biosynthetic diversity leading to different toxicokinetics and toxicodynamics. Several studies investigated the toxicity of mycotoxins, focusing on very specific targets, like the brain. However, it still remains unclear how fast mycotoxins reach the brain and if they impair the integrity of the blood-brain barrier. This study investigated and compared the effects of the Fusarium mycotoxins deoxynivalenol, 3-acetyldeoxynivalenol and moniliformin on the blood-brain barrier. Furthermore, the transfer properties to the brain were analyzed, which are required for risk assessment, including potential neurotoxic effects.

METHODS

Primary porcine brain capillary endothelial cells were cultivated to study the effects of the examined mycotoxins on the blood-brain barrier in vitro. The barrier integrity was monitored by cellular impedance spectroscopy and 14C radiolabeled sucrose permeability measurements. The distribution of the applied toxins between blood and brain compartments of the cell monolayer was analyzed by high performance liquid chromatography-mass spectrometry to calculate transfer rates and permeability coefficients.

RESULTS

Deoxynivalenol reduced the barrier integrity and caused cytotoxic effects at 10 μM concentrations. Slight alterations of the barrier integrity were also detected for 3-acetyldeoxynivalenol. The latter was transferred very quickly across the barrier and additionally cleaved to deoxynivalenol. The transfer of deoxynivalenol and moniliformin was slower, but clearly exceeded the permeability of the negative control. None of the compounds was enriched in one of the compartments, indicating that no efflux transport protein is involved in their transport.

Countercurrent Separation of Natural Products: An Update

This work assesses the current instrumentation, method development, and applications in countercurrent chromatography (CCC) and centrifugal partition chromatography (CPC), collectively referred to as countercurrent separation (CCS). The article provides a critical review of the CCS literature from 2007 since our last review (J. Nat. Prod. 2008, 71, 1489-1508), with a special emphasis on the applications of CCS in natural products research. The current state of CCS is reviewed in regard to three continuing topics (instrumentation, solvent system development, theory) and three new topics (optimization of parameters, workflow, bioactivity applications). The goals of this review are to deliver the necessary background with references for an up-to-date perspective of CCS, to point out its potential for the natural product scientist, and thereby to induce new applications in natural product chemistry, metabolome, and drug discovery research involving organisms from terrestrial and marine sources.

A comparative study of the human urinary mycotoxin excretion patterns in Bangladesh, Germany, and Haiti using a rapid and sensitive LC-MS/MS approach

An improved "dilute and shoot" LC-MS/MS multibiomarker approach was used to monitor urinary excretion of 23 mycotoxins and their metabolites in human populations from Asia (Bangladesh), Europe (Germany), and the Caribbean region (Haiti). Deoxynivalenol (DON), deoxynivalenol-3-glucuronide (DON-3-GlcA), T-2-toxin (T-2), HT-2-toxin (HT-2), HT-2-toxin-4-glucuronide (HT-2-4-GlcA), fumonisin B1 (FB1), aflatoxins (AFB1, AFB2, AFG1, AFG2, AFM1), zearalenone (ZEA), zearalanone (ZAN), their urinary metabolites α-zearalanol (α-ZEL) and β-zearalanol (β-ZEL), and corresponding 14-O-glucuronic acid conjugates (ZEA-14-GlcA, ZAN-14-GlcA, β-ZEL, α/β-ZEL-14-GlcA), ochratoxin A (OTA), and ochratoxin alpha (OTα) as well as enniatin B (EnB) and dihydrocitrinone (DH-CIT) were among these compounds. Eight urinary mycotoxin biomarkers were detected (AFM1, DH-CIT, DON, DON-GLcA, EnB, FB1, OTA, and α-ZEL). DON and DON-GlcA were exclusively detected in urines from Germany and Haiti whereas urinary OTA and DH-CIT concentrations were significantly higher in Bangladeshi samples. AFM1 was present in samples from Bangladesh and Haiti only. Exposure was estimated by the calculation of probable daily intakes (PDI), and estimates suggested occasional instances of toxin intakes that exceed established tolerable daily intakes (TDI). The detection of individual mycotoxin exposure by biomarker-based approaches is a meaningful addition to the classical monitoring of the mycotoxin content of the food supply.

Influence of T-2 and HT-2 toxin on the blood-brain barrier in vitro: new experimental hints for neurotoxic effects

The trichothecene mycotoxin T-2 toxin is a common contaminant of food and feed and is also present in processed cereal derived products. Cytotoxic effects of T-2 toxin and its main metabolite HT-2 toxin are already well described with apoptosis being a major mechanism of action. However, effects on the central nervous system were until now only reported rarely. In this study we investigated the effects of T-2 and HT-2 toxin on the blood-brain barrier (BBB) in vitro. Besides strong cytotoxic effects on the BBB as determined by the CCK-8 assay, impairment of the barrier function starting at low nanomolar concentrations were observed for T-2 toxin. HT-2 toxin, however, caused barrier disruption at higher concentrations compared to T-2 toxin. Further, the influence on the tight junction protein occludin was studied and permeability of both toxins across the BBB was detected when applied from the apical (blood) or the basolateral (brain) side respectively. These results clearly indicate the ability of both toxins to enter the brain via the BBB.

Cytotoxicity and fluorescence visualization of ergot alkaloids in human cell lines

The ergot alkaloids as secondary metabolites from fungi of the genus Claviceps are the focus of many investigations because of their pharmacological and toxicological properties. The main effects of ergot alkaloids are referred to an interaction with several receptor systems in the human body. It is well-known that ergot alkaloids are able to isomerize with one isomer being biologically active and one being only weakly active, whereas the activity is restricted to receptor interactions. Latest investigations have proven that ergot alkaloids also show cytotoxic effects and induce apoptosis in human primary cells. These effects seem to correlate with accumulation properties. It was the aim of our current study to determine such effects in cancer cell lines, because ergot derivatives are also used in tumor therapy. Our results confirm the apoptotic effects in two cancer cell lines (HepG2 and HT-29) in a high range, and accumulation measurements show an interesting correlation between the alkaloid concentration in the cell lysate of the receptor-inactive isomers and cytotoxicity. In addition, the strong accumulative effects were first visualized by fluorescence microscopy by taking advantage of the natural fluorescence properties of ergot alkaloids.

HT-2 toxin 4-glucuronide as new T-2 toxin metabolite: enzymatic synthesis, analysis, and species specific formation of T-2 and HT-2 toxin glucuronides by rat, mouse, pig, and human liver microsomes

Glucuronides of the mycotoxin T-2 toxin and its phase I metabolite HT-2 toxin are important phase II metabolites under in vivo and in vitro conditions. Since standard substances are essential for the direct quantitation of these glucuronides, a method for the enzymatic synthesis of T-2 and HT-2 toxin glucuronides employing liver microsomes was optimized. Structure elucidation by nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry revealed that besides T-2 toxin glucuronide and HT-2 toxin 3-glucuronide also the newly identified isomer HT-2 toxin 4-glucuronide was formed. Glucuronidation of T-2 and HT-2 toxin in liver microsomes of rat, mouse, pig, and human was compared and metabolites were analyzed directly by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). A distinct, species specific pattern of glucuronidation of T-2 and HT-2 toxin was observed with interesting interindividual differences. Until recently, glucuronides have frequently been analyzed indirectly by quantitation of the aglycone after enzymatic cleavage of the glucuronides by β-glucuronidase. Therefore, the hydrolysis efficiencies of T-2 and HT-2 toxin glucuronides using β-glucuronidases from Helix pomatia, bovine liver, and Escherichia coli were compared.

New approach via gene knockout and single-step chemical reaction for the synthesis of isotopically labeled fusarin c as an internal standard for the analysis of this fusarium mycotoxin in food and feed samples

The gold standard for quantitation of contaminants with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) is the use of isotopically labeled standards. Herein, we report a new strategy for the synthesis of isotopically labeled 21-d3-fusarin C via a genetically modified Fusarium strain, followed by a one-step derivatization reaction. Fusarin C is a Fusarium mycotoxin, which is mutagenic after metabolic activation. Its occurrence has been demonstrated recently in corn-based samples, but up to now, little is known about the contamination of other grain samples. To collect further data, the quantitation method was enhanced by application of the 21-d3-fusarin C and the use of a QTRAP 5500 mass spectrometer. This new method has a limit of detection (LOD) of 1 μg/kg, a limit of quantitation (LOQ) of 4 μg/kg, and a recovery rate of 99%. A total of 21 corn samples and 13 grain samples were analyzed, with resulting fusarin C levels varying from not detectable to 24.7 μg/kg.

Identification and apoptotic potential of T-2 toxin metabolites in human cells

The mycotoxin T-2 toxin, produced by various Fusarium species, is a widespread contaminant of grain and grain products. Knowledge about its toxicity and metabolism in the human body is crucial for any risk assessment as T-2 toxin can be detected in processed and unprocessed food samples. Cell culture studies using cells of human origin represent a potent model system to study the metabolic fate of T-2 toxin as well as the cytotoxicity in vitro. In this study the metabolism of T-2 toxin was analyzed in a cell line derived from human colon carcinoma cells (HT-29) and primary human renal proximal tubule epithelial cells (RPTEC) using high-performance liquid chromatography coupled with Fourier transformation mass spectrometry (HPLC-FTMS). Both cell types metabolized T-2 toxin to a variety of compounds. Furthermore, cell cycle analysis in RPTEC proved the apoptotic effect of T-2 toxin and its metabolites HT-2 toxin and neosolaniol in micromolar concentrations.

Cytotoxicity and accumulation of ergot alkaloids in human primary cells

Ergot alkaloids are secondary metabolites produced by fungi of the species Claviceps. Toxic effects after consumption of contaminated grains are described since mediaeval times. Of the more than 40 known ergot alkaloids six are found predominantly. These are ergotamine, ergocornine, ergocryptine, ergocristine, ergosine and ergometrine, along with their corresponding isomeric forms (-inine-forms). Toxic effects are known to be induced by an interaction of the ergot alkaloids as neurotransmitters, like dopamine or serotonin. Nevertheless data concerning cytotoxic effects are missing and therefore a screening of the six main ergot alkaloids was performed in human primary cells in order to evaluate the toxic potential. As it is well known that ergot alkaloids isomerize easily the stability was tested in the cell medium. Based on these results factors were calculated to correct the used concentration values to the biologically active lysergic (-ine) form. These factors range from 1.4 for the most stable compound ergometrine to 5.0 for the most unstable ergot alkaloid ergocristine. With these factors, reflecting the instability, several controverse literature data concerning the toxicity could be explained. To evaluate the cytotoxic effects of ergot alkaloids, human cells in primary culture were used. These cells remain unchanged in contrast to cell lines and the data allow a better comparison to the in vivo situation than using immortalized cell lines. To characterize the effects on primary cells, renal proximal tubule epithelial cells (RPTEC) and normal human astrocytes (NHA) were used. The parameters necrosis (LDH-release) and apoptosis (caspase-3-activation, DNA condensation and fragmentation) were distinguished. The results show that depending on the individual structure of the peptide ergot alkaloids the toxic properties change. While ergometrine as a lysergic acid amide did not show any effect, the peptide ergot alkaloids revealed a different toxic potential. Of all tested ergot alkaloids ergocristine was the most cytotoxic compound inducing apoptosis in human kidney cells starting at a concentration of 1μM in RPTEC. Uptake studies underline the cytotoxic properties, with an accumulation of peptide ergot alkaloids and no uptake of ergometrine. The results represent a new description of effects of ergot alkaloids regarding cytotoxicity and accumulation in human primary cells. For the first time apoptosis has been identified besides well described receptor effects. This gives a hint for a more complex mode of action of ergot alkaloids than described in literature so far.