Determination of five Alternaria toxins in wolfberry using modified QuEChERS and ultra-high performance liquid chromatography-tandem mass spectrometry.

A modified quick, easy, cheap, effective, rugged, and safe method coupled with ultra-high performance liquid chromatography-tandem mass spectrometry was established for the simultaneous detection of five Alternaria toxins (tenuazonic acid, alternariol, alternariol monomethyl ether, altenuene, and tentoxin) in wolfberry. The sample pretreatment conditions including the dilution solvent, the extraction solvent and the QuEChERS purification parameters were optimized. Detection of the five Alternaria toxins was performed in MRM mode under ESI + conditions. The results showed that the five Alternaria toxins exhibitedgood linearity (1-200 µg/L, with correlation coefficients > 0.999). The limits of detection were 0.07-0.24 µg/kg, and the limits of quantification were 0.32-0.77 µg/kg. The trueness was between 73.8% and 111.5%, and the precision was lower than 10%. The established method was effectively used for the determination of five Alternaria toxins in 155 wolfberry samples from Northwest China.

Aminotenuazonic Acid: Isolation, Structure Elucidation, Total Synthesis and Herbicidal Activity of a New Tetramic Acid from Fruiting Bodies of Laccaria Species.

(5S,6S)-Aminotenuazonic acid, a new 3-acyltetramic acid, related to the well-known mycotoxin tenuazonic acid has been isolated from fruiting bodies of Laccaria bicolor. Its structure was mostly established by analysis of its 2D NMR and HR-(+)-ESI-MS spectra. A total synthesis starting from N-Boc-l-isoleucine gave (5S,6S)-aminotenuazonic acid in 8 % yield over nine steps (67 % de). The key steps of the total synthesis are a light-initiated Hofmann-Löffler-Freytag radical chain reaction and a Dieckmann cyclisation. The relative and absolute configurations of the natural product were determined by comparison of its NMR and CD spectra with those of the corresponding enantiopure synthetic compounds. Metabolic profiling of crude extracts of different mushrooms showed that aminotenuazonic acid is present in all four of the investigated Laccaria species. Aminotenuazonic acid shows phytotoxic activities against the root and shoot growth of Lepidium sativum, Pinus sylvestris and Arabidopsis thaliana comparable to those of tenuazonic acid.

Determination of Exposure to the Alternaria Mycotoxin Tenuazonic Acid and Its Isomer allo-Tenuazonic Acid in a German Population by Stable Isotope Dilution HPLC-MS(3).

The content of the Alternaria toxin tenuazonic acid and its isomer allo-tenuazonic acid was quantitated in urine of a German cohort (n = 48) using a newly developed and successfully validated solid phase extraction based stable isotope dilution HPLC-MS(3) method. Tenuazonic acid was detected in all of the samples and quantifiable in 97.9% of these samples in a range of 0.16-44.4 ng/mL (average = 6.58 ng/mL) or 0.07-63.8 ng/mg creatinine (average = 8.13 ng/mg creatinine). allo-Tenuazonic acid was for the first time detected in human urine (95.8% of the samples positive) and quantitated in 68.8% of the samples in a range of 0.11-5.72 ng/mL (average = 1.25 ng/mL) or 0.08-10.1 ng/mg creatinine (average = 1.52 ng/mg creatinine), representing 3.40-25.0% of the sum of both isomers (average = 12.4%). Food-frequency questionnaires were used to document food consumption of study participants to correlate mycotoxin exposure to nutritional habits. Although no statistically significant correlation between consumption of a specific food and urinary excretion of tenuazonic acid could be determined, a trend regarding elevated intake of cereal products and higher excretion of tenuazonic acid was evident. On the basis of these results, a provisional mean daily intake (PDI) for both tenuazonic acid and allo-tenuazonic acid was calculated, being 0.183 and 0.025 µg/kg body weight, respectively. A combined mean PDI for both isomers amounts to 0.208 µg/kg body weight with the highest individual PDI for one of the participants (1.582 µg/kg body weight) slightly exceeding the threshold of toxicological concern assumed for tenuazonic acid by the European Food Safety Authority of 1.500 µg/kg body weight. This is the first study to investigate the tenuazonic acid content in human urine of a larger sample cohort enabling the calculation of PDIs for tenuazonic acid and allo-tenuazonic acid.

Detection and Quantitative Analysis of the Non-cytotoxic allo-Tenuazonic Acid in Tomato Products by Stable Isotope Dilution HPLC-MS/MS.

Tenuazonic acid (1) is a mycotoxin produced mainly by fungi of the genus Alternaria. It occurs in a variety of agricultural products. allo-Tenuazonic acid (2) is an isomer of 1 that is not chromatographically separated from 1 in most analytical methods. Therefore, both isomers are quantitated as a sum parameter. In this study a QuEChERS (quick, easy, cheap, effective, rugged and safe) based stable isotope dilution HPLC-MS/MS method including the chromatographic separation of both isomers was developed and applied to 20 tomato products from the German market. All products showed contamination with both toxins. 1 was found in a range from 5.3 ± 0.1 to 550 ± 15 µg/kg (average = 120 µg/kg) and 2 in a range from 1.5 ± 0.4- to 270 ± 0.8 µg/kg (average = 58 µg/kg). 2 represents 7.0-44% of the sum of both isomers (average = 29%). This is the first reported occurrence of 2 in food samples. To evaluate and compare the cytotoxicities of 1 and 2, both compounds were isolated from a synthetic racemic mixture. 1 showed moderate cytotoxic effects on HT-29 cells starting at 100 µM, whereas 2 exhibited no activity. 2 was not produced in liquid cultures of Alternaria alternata in yeast extract sucrose (YES) medium, but could be detected in small amounts in tomato puree inoculated with the fungus.

Brazil nuts are subject to infection with B and G aflatoxin-producing fungus, Aspergillus pseudonomius.

The exploitation of the Brazil nut is one of the most important activities of the extractive communities of the Amazon rainforest. However, its commercialization can be affected by the presence of aflatoxins produced by fungi, namely Aspergillus section Flavi. In the present study, we investigated a collection of Aspergillus nomius strains isolated from Brazil nuts using different approaches, including morphological characters, RAPD and AFLP profiles, partial ß-tubulin and calmodulin nucleotide sequences, aflatoxin patterns, as well as tolerance to low water activity in cultured media. Results showed that most of the isolates do belong to A. nomius species, but a few were re-identified as Aspergillus pseudonomius, a very recently described species. The results of the analyses of molecular variance, as well as the high pairwise FST values between A. nomius and A. pseudonomius suggested the isolation between these two species and the inexistence of gene flow. Fixed interspecific nucleotide polymorphisms at ß-tubulin and calmodulin loci are presented. All A. pseudonomius strains analyzed produced aflatoxins AFB1, AFB2, AFG1 and AFG2. This study contains the first-ever report on the occurrence in Brazil nuts of A. pseudonomius. The G-type aflatoxins and the mycotoxin tenuazonic acid are reported here for the first time in A. pseudonomius.

Real-time PCR quantification of the AM-toxin gene and HPLC qualification of toxigenic metabolites from Alternaria species from apples.

Some Alternaria species are able to produce plant pathogenic as well as toxic metabolites. In both agriculture and the food industry it is important know if toxigenic Alternaria are present to rapidly employ the correct corrective actions. The purpose of this work was to establish a real-time PCR method, which can detect and quantify apple pathogenic and toxigenic Alternaria. An AM-toxin I primer set, which could recognize Alternaria DNA only, was designed by using primers complementary to the AM-toxin I gene. The method could detect small amounts of DNA (4 pg) and still obtain a large dynamic range (4 decades) without interference from apple material. Eight Alternaria isolates were analyzed for the presence of AM-toxin I gene and their production of secondary metabolites. Then analyses showed that all eight isolates contained the AM toxin gene and were able to produce the plant pathogenic tentoxin in addition to AM toxin I. The analyses also showed the production of tenuazonic acid, alternariols, Altenuene, altenusin and/or altertoxin I in pure culture. Analyses of inoculated apples showed that both the AM-toxin gene and alternariol monomethyl ether could be detected. Morphological analyses suggested that the eight Alternaria strains, though they all carried the AM toxin genes, probably belong to different but closely related un-described Alternaria taxa in the A. tenuissima species-group based on morphological and chemical differences.

[The detection of Alternaria mycotoxins in laboratory culture]. / Nachweis von Alternaria-Mykotoxinen in Laborkulturen.

Analytical methods are described for detection of the Alternaria mycotoxins alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT) and tenuazonic acid (TeA) in natural and semisynthetic laboratory cultures. After extraction and purification of the crude extract by column chromatography on silica gel the qualitative and quantitative analyses were carried out by thin layer (TLC)- and high performance liquid chromatography (HPLC). HPLC separations were achieved using a Hypersil ODS column with methanol/water containing a complexing agent as eluent. Detection at 340 nm (AOH, AME, ALT) and 280 nm (TeA), respectively, has proved to be favourably. AME and TeA were produced in high purity and high yields as standard substances by two Alternaria strains. The identity of the toxins could be confirmed by EI-, CI- and FAB-mass spectrometry.