Biosynthesis of the trichothecene 3-acetyldeoxynivalenol: cell-free hydroxylations of isotrichodermin

3-Acetyldeoxynivalenol is the major trichothecene produced by the fungus Fusarium culmorum. Studies in vivo with F. culmorum have established the following biosynthetic precursors of 3-acetyldeoxynivalenol: isotrichool?→?isotrichodiol?→?isotrichodermin?→?15-deacetylcalonectrin, 7α-hydroxyisotrichodermin, 8α-hydroxyisotrichodermin?→?calonectrin?→?deoxynivalenol. In this paper, we describe in vitro investigations of one of these metabolic steps. The cell-free system of F. culmorum that converts isotrichodermin into 15-deacetylcalonectrin, 7α-hydroxyisotrichodermin, and 8α-hydroxyisotrichodermin is described here. This preparation requires NADPH but not NADH for activity and is not inhibited by carbon monoxide, cyanide, or known oxygenase inhibitors, such as SKF-525-A or ancymidol.Key words: trichothecene, Fusarium culmorum, cell-free system, isotrichodermin, 15-deacetylcalonectrin.     

Heterologous expression of two trichothecene P450 genes in Fusarium verticillioides

Fusarium graminearum Z-3639 and F. sporotrichioides NRRL3299 produce the trichothecene mycotoxins 15-acetyldeoxynivalenol and T-2 toxin, respectively. These toxins differ in oxygenation at C-4, C-7, and C-8. In F. sporotrichioides, Tri1 (FsTri1) controls C-8 hydroxylation. To determine the function of an apparent F. graminearum Tri1 (FgTri1) homolog, both FsTri1 and FgTri1 genes were heterologously expressed in the trichothecene-nonproducing species F. verticillioides by fusing the Tri1 coding regions to the promoter of the fumonisin biosynthetic gene FUM8. FsTri1 and FgTri1 have been partially characterized by disruption analysis, and the results from these analyses suggest that FsTri1 most likely has a single function but that FgTri1 may have two functions. Transgenic F. verticillioides carrying the FsTri1 (FvF8FsTri1) converted exogenous isotrichodermin and calonectrin to 8-hydroxyisotrichodermin and 8-hydroxycalonectrin, respectively. Transgenic F. verticillioides carrying FgTri1 (FvF8FgTri1) converted isotrichodermin to a mixture of 7-hydroxyisotrichodermin and 8-hydroxyisotrichodermin but converted calonectrin to a mixture of 7-hydroxycalonectrin, 8-hydroxycalonectrin, and 3,15-diacetyldeoxynivalenol. A fourth compound, 7,8-dihydroxycalonectrin, was identified in large-scale F. verticillioides FvF8FgTri1 cultures fed isotrichodermin. Our results indicate that FgTri1 controls both C-7 and C-8 hydroxylation but that FsTri1 controls only C-8 hydroxylation. Our studies also demonstrate that F. verticillioides can metabolize some trichothecenes by adding an acetyl group to C-3 or by removing acetyl groups from C-4 or C-15. In addition, wild-type F. verticillioides can convert 7,8-dihydroxycalonectrin to 3,15-diacetyldeoxynivalenol.     

Accumulation of Trichothecenes in Liquid Cultures of a Fusarium sporotrichioides Mutant Lacking a Functional Trichothecene C-15 Hydroxylase

A mutant strain of Fusarium sporotrichioides NRRL 3299 produced by disruption of Tri11, a gene encoding a cytochrome P-450 monooxygenase, was shown to be altered in its ability to biosynthesize T-2 toxin. This mutant strain produced four trichothecenes that were not observed in cultures of the parent strain. The compounds were identified as isotrichodermin, 8-hydroxyisotrichodermin, 8-hydroxyisotrichodermol, and 3,4,8-trihydroxytricothecene on the basis of their nuclear magnetic resonance and mass spectra. This is the first report of these 8-hydroxytrichothecenes as metabolites of F. sporotrichioides. The accumulation of isotrichodermin and the results of whole-cell feeding experiments with a Tri11(sup-) strain confirm that oxygenation of C-15 is blocked.     

Fusarium Tri4 encodes a multifunctional oxygenase required for trichothecene biosynthesis

Fusarium graminearum and Fusarium sporotrichioides produce the trichothecene mycotoxins 15-acetyldeoxynivalenol and T-2 toxin, respectively. In both species, disruption of the P450 monooxygenase-encoding gene, Tri4, blocks production of the mycotoxins and leads to the accumulation of the trichothecene precursor trichodiene. To further characterize its function, the F. graminearum Tri4 (FgTri4) was heterologously expressed in the trichothecene-nonproducing species Fusarium verticillioides. Transgenic F. verticillioides carrying the FgTri4 converted exogenous trichodiene to the trichothecene biosynthetic intermediates isotrichodermin and trichothecene. Conversion of trichodiene to isotrichodermin requires seven biochemical steps. The fifth and sixth steps can occur nonenzymatically. Precursor feeding studies done in the current study indicate that wild-type F. verticillioides has the enzymatic activity necessary to carry out the seventh step, the C-3 acetylation of isotrichodermol to form isotrichodermin. Together, the results of this study indicate that the Tri4 protein catalyzes the remaining four steps and is therefore a multifunctional monooxygenase required for trichothecene biosynthesis.     

Biosynthesis of 3-acetyldeoxynivalenol and sambucinol. Identification of the two oxygenation steps after trichodiene

The first two oxygenation steps post-trichodiene in the biosyntheses of the trichothecenes 3-acetyldeoxynivalenol and sambucinol were investigated. The plausible intermediates 2-hydroxytrichodiene (2alpha- and 2beta-) and 12,13-epoxytrichodiene and the dioxygenated compounds 12,13-epoxy-9,10-trichoene-2-ol (2alpha- and 2beta-) were prepared specifically labeled with stable isotopes. They were then fed separately and/or together to Fusarium culmorum cultures, and the derived trichothecenes were isolated, purified, and analyzed. The stable isotopes enable easy localization of the labels in the products by 2H NMR, 13C NMR, and mass spectrometry. We found that 2alpha-hydroxytrichodiene is the first oxygenated step in the biosynthesis of both 3-acetyldeoxynivalenol and sambucinol. The stereoisomer 2beta-hydroxytrichodiene and 12,13-epoxytrichodiene are not biosynthetic intermediates and have not been isolated as metabolites. We also demonstrated that the dioxygenated 12, 13-epoxy-9,10-trichoene-2alpha-ol is a biosynthetic precursor to trichothecenes as had been suggested in a preliminary work. Its stereoisomer was not found in the pathway. A further confirmation of our results was the isolation of both oxygenated trichodiene derivatives 2alpha-hydroxytrichodiene and 12,13-epoxy-9, 10-trichoene-2alpha-ol as natural metabolites in F. culmorum cultures.     

13C NMR study of the biosynthesis of toxins by Fusarium graminearum

13C NMR spectroscopic investigations on the biosynthesis of mycotoxins produced by Fusarium graminearum (M69) were carried out through the incorporation of [1-13C]- and [2-13C]acetate precursors. The major secondary metabolites produced by this species in still culture were deoxynivalenol (3,7,15-trihydroxy-12,13-epoxytrichothec-9-en-one), 15-acetyldeoxynivalenol, zearalenone, and butenolide. [1-13C]- and [2-13C]acetate were incorporated in alternate carbon atoms in zearalenone, consistent with the head to tail condensation of nine acetate units. The trichothecenes were enriched in a manner consistent with the condensation of three mevalonate units. 13C/13C couplings, observed between C-5 and C-12, as well as between C-6 and C-15 of 15-acetyldeoxynivalenol, confirms the current hypothesis of formation of the trichothecene ring system by cyclization of farnesyl pyrophosphate. The incorporation pattern in ergosterol is also consistent with a mevalonate origin, while the adjacent incorporation of acetate methyl groups in butenolide suggests a glutamate precursor. The degree of enrichment in the secondary metabolites, which ranged from 3 to 10% at each carbon site, was observed in the 13C NMR spectra of the crude fungal extracts to be dependent on the timing of acetate addition to the culture. The specific toxins produced together with the quantity of each, were also found to be dependent on the timing of acetate addition. Competition between the three biosynthetic pathways of secondary metabolism, i.e. polyketide, mevalonate, and amino acid for the labeled acetate in this organism is a complex function of culture conditions.     

Production of culmorin compounds and other secondary metabolites by Fusarium culmorum and F. graminearum strains isolated from Norwegian cereals

Twenty-three Fusarium culmorum and 21 F. graminearumisolates were studied for their ability to produce mycotoxins and other secondary metabolites. The strains were cultivated on rice, and the extracts analysed by gas chromatography mass spectrometry (GC-MS) after derivatization with pentafluoropropionic (PFP) reagent. Two F. culmorum strains formed nivalenol and its acetylated derivatives (chemotype II), while all F. graminearum and the otherF. culmorum isolates produced deoxynivalenol (DON) via 3-acetyldeoxynivalenol (3-acetyl-DON) (chemotype IA). 15-hydroxy-culmorin, followed by 5-hydroxy-culmorin were the main other metabolites produced F. culmorum, while 5-, 12- and an unidentified hydroxy-culmorin, suggested to be 14-hydroxy-culmorin, were the main metabolites of F. graminearum. The hydroxy-culmorin profile was found to be significantly different for the two Fusarium species. Minor amounts of about ten other hydroxy-culmorins, four hydroxy-culmorones and 3,13-dihydroxy-epiapotrichothecene were also detected in most cultures. Traces of sambucinol seemed to be present in some of the isolates, but were not detected in any significant amounts. The precursors in the biosynthetic sequence to 3-acetyldeoxynivalenol,7,8-dihydroxycalonectrin and 15-deacetyl-7,8-dihydroxycalonectrin,were detected in most cultures. We also report the assignment of both the ¹H and¹³C NMR data of 15-deacetyl-7,8-dihydroxycalonectrin, which has only been reported incorrectly before. This revised version was published online in August 2006 with corrections to the Cover Date.     

Structural identification of methyl protodioscin metabolites in rats' urine and their antiproliferative activities against human tumor cell lines

Methyl protodioscin (MPD), a furostanol saponin, is a preclinical drug shown potent antiproliferative activities against most cell lines from leukemia and solid tumors. The metabolites of MPD in rats' urine after single oral doses of 80 mg/kg were investigated in this research. Ten metabolites were isolated and purified by liquid-liquid extraction, open-column chromatography, medium-pressure liquid chromatography, and preparative high-performance liquid chromatography. The structural identification of the metabolites was carried out by high resolution mass spectra, NMR spectroscopic methods including (1)H NMR, (13)C NMR and 2D NMR, as well as chemical ways. The 10 metabolites were elucidated to be dioscin (M-1), pregna-5,16-dien-3beta-ol-20-one-O-alpha-l-rhamnopyranosyl-(1-->2)-[alpha-l-rhamnopyranosyl-(1-->4)]-beta-d-glucopyranoside (M-2), diosgenin (M-3), protobioside (M-4), methyl protobioside (M-5), 26-O-beta-d-glucopyrannosyl(25R)-furan-5-ene-3beta, 22alpha, 26-trihydroxy-3-O-alpha-l-rhamnopyranosyl-(1-->4)-beta-d-glucopyranoside(M-6),26-O-beta-d-glucopyranosyl(25R)-furan-5-ene-3beta,26-dihydroxy-22-methoxy-3-O-alpha-l-rhamnopyranosyl-(1-->4)-beta-d-glucopyranoside (M-7), prosapogenin A of dioscin (M-8), prosapogenin B of dioscin (M-9), and diosgenin-3-O-beta-d-glucopyranoside (M-10), respectively. M-1 was the main urinary metabolite of MPD in rats. Some metabolites showed potent antiproliferative activities against HepG2, NCI-H460, MCF-7 and HeLa cell lines in vitro.     

Biosynthesis,isolation, purification and seperation of Zearalenone,deoxynivalenol and 15-Acetyldeoxynivalenol

Fusarium graminearum KF-376 isolate was found to be able to form simultaneously three toxic metabolites: zearalenone (FF-2), deoxynivalenol (DON) and 15-acetyldeoxynivalenol (15-AcDON). Toxins were extracted with methanol — water 3:1 (v/v) and purified by liquid chromatography on charcoal — Kieselgel 60 column (preliminary) and Aluminiumoxid 90 column. Final separation of the metabolites was achived on Kieselgel 60 — Aluminiumoxid 90 column.     

Is Fusarium culmorum isotrichodermin-15-hydroxylase different from other fungal species?

Fusarium spp. are ubiquitous fungi infecting cereals and grains, and therefore constitute a major problem for agriculture. Their trichothecene metabolites, and in particular deoxynivalenol and its 3-acetylated derivative, are the mycotoxins involved. The major metabolite produced by Fusarium culmorum is 3-acetyldeoxynivalenol. Studies in vivo with Fusarium culmorum have established that its tricyclic intermediate, isotrichodermin, is a major biosynthetic precursor, which is hydroxylated at position 15 to give 15-deacetylcalonectrin, prior to being converted to the product. In a preliminary in vitro investigation of the cell-free system involved in this transformation, we suggested that cytochrome P450 enzymes are not involved. In this paper, the isotrichodermin-15-hydroxylase from the microsomal fraction of Fusarium culmorum was solubilized and partially purified (60 fold). Our studies with cofactors indicate that this enzyme is a flavoprotein, and the inducers tested highly indicate that indeed the hydroxylase is not attached to cytochrome P450. This is particularly interesting, since the only other enzyme catalyzing the same reaction isolated from Fusarium sporotrichiodes is attached to cytochrome P450.     

Simultaneous determination of major B-trichothecenes and the de-epoxy-metabolite of deoxynivalenol in pig urine and maize using high-performance liquid chromatography-mass spectrometry

A selective analytical method based on high-performance liquid chromatography (HPLC), combined with atmospheric pressure chemical ionisation (APCI-) mass spectrometry (MS), has been developed for simultaneous determination of B-trichothecenes and the major metabolites of deoxynivalenol. The method allows simultaneous analysis of nivalenol (NIV), deoxynivalenol (DON), 15-acetyldeoxynivalenol (15-AcDON), 3-acetyldeoxynivalenol (3-AcDON), fusarenon X (Fus-X) and de-epoxydeoxynivalenol (DOM-1). The method is based on one-step sample clean-up using a multifunctional MycoSep column. A linear gradient mobile phase system, consisting of water:acetonitrile:methanol (H2O:ACN:MeOH) at a flow-rate of 1 ml/min, and a Polar-RP C18 column, were utilised to obtain the best resolution of all tested compounds along with column and equilibrating within 30 min. Dexamethasone (Dex) was used as internal standard. The developed method shows good repeatability for inter- and intra-day precisions as well as good linearity of calibration curves (r2 ranged from 0.9936 to 0.9998). Average recoveries for tested compounds in both matrices have been determined ranging from 63.7 to 102.3% and limit of quantification (LOQ) ranged from 25 to 150 ng/g. The utility and practical impact of the method is demonstrated using contaminated pig urine and maize samples.     

Hydroxylated 2-amino-3H-phenoxazin-3-one derivatives as products of 2-hydroxy-1,4-benzoxazin-3-one (HBOA) biotransformation by Chaetosphaeria sp., an endophytic fungus from Aphelandra tetragona

The biotransformation of the phytoanticipin HBOA and its major degradation metabolites 2-hydroxy-N-(2-hydroxyphenyl)acetamide (7) and N-(2-hydroxyphenyl)acetamide (8) by Chaetosphaeria sp., an endophytic fungus isolated from Aphelandra tetragona, was studied. Three new metabolites could be identified as 2-amino-7-hydroxy-3H-phenoxazin-3-one (12), 2-acetylamino-7-hydroxy-3H-phenoxazin-3-one (13) and 7-hydroxy-2-(2-hydroxyacetyl)-amino-3H-phenoxazin-3-one (14). Structure elucidation of 12 and 13 was performed by MS, 1H, 13C NMR and 2D NMR techniques and confirmed by chemical transformation.     

Formation of C21 bile acids from plant sterols in the rat

Formation of bile acids from sitosterol in bile-fistulated female Wistar rats was studied with use of 4-14C-labeled sitosterol and sitosterol labeled with 3H in specific positions. The major part (about 75%) of the 14C radioactivity recovered as bile acids in bile after intravenous administration of [4-14C]sitosterol was found to be considerably more polar than cholic acid, and only trace amounts of radioactivity had chromatographic properties similar to those of cholic acid and chenodeoxycholic acid. It was shown that polar metabolites were formed by intermediate oxidation of the 3 beta-hydroxyl group (loss of 3H from 3 alpha-3H-labeled sitosterol) and that the most polar fraction did not contain a hydroxyl group at C7 (retention of 3H in 7 alpha,7 beta-3H2-labeled sitosterol). Furthermore, the polar metabolites had lost at least the terminal 6 or 7 carbon atoms of the side chain (loss of 3H from 22,23-3H2- and 24,28-3H2-labeled sitosterol). Experiments with 3H-labeled 7 alpha-hydroxysitosterol and 4-14C-labeled 26-hydroxysitosterol showed that none of these compounds was an efficient precursor to the polar metabolites. By analysis of purified most polar products of [4-14C] sitosterol by radio-gas chromatography and the same products of 7 alpha,7 beta-[2H2]sitosterol by combined gas chromatography-mass spectrometry, two major metabolites could be identified as C21 bile acids. One metabolite had three hydroxyl groups (3 alpha, 15, and unknown), and one had two hydroxyl groups (3 alpha, 15) and one keto group. Considerably less C21 bile acids were formed from [4-14C]sitosterol in male than in female Wistar rats. The C21 bile acids formed in male rats did not contain a 15-hydroxyl group. Conversion of a [4-14C]sitosterol into C21 bile acids did also occur in adrenalectomized and ovariectomized rats, indicating that endocrine tissues are not involved. Experiments with isolated perfused liver gave direct evidence that the overall conversion of sitosterol into C21 bile acids occurs in this organ. Intravenously injected 7 alpha,7 beta-3H-labeled campesterol gave a product pattern identical to that of 4-14C-labeled sitosterol. Possible mechanisms for hepatic conversion of sitosterol and campesterol into C21 bile acids are discussed.     

Microbiological transformation of diosgenin by resting cells of filamentous fungus,Cunninghamella echinulata CGMCC 3.2716

Microbial transformation of the steroidal sapogenin diosgenin (1) by resting cells of the filamentous fungus, Cunninghamella echinulata CGMCC 3.2716 was studied. Four metabolites were isolated and unambiguously characterized as (25R)-spirost-5-ene-3β,7β-diol-11-one (2), (25R)-spirost-5-ene-3β,7β-diol (3), (25R)-spirost-5-ene-3β,7β,11α-triol (4), and (25R)-spirost-5-ene-3β,7β,12β-triol (5), by various spectroscopic methods (¹H, ¹³C NMR, DEPT, ¹H–¹H COSY, HMBC, HSQC and NOESY). Compound 2 is a new metabolite. The NMR data and full assignment for the known metabolites (25R)-spirost-5-ene-3β,7β-diol (3) and (25R)-spirost-5-ene-3β,7β,11α-triol (4) are described here for the first time. The biotransformation characteristics observed included were C-7β, C-11α and C-12β hydroxylations. Compounds 1–5 exhibited no significant cytotoxic activity to human glioma cell line U87.     

Kinetic pulse-labeling study of Fusarium culmorum. Biosynthetic intermediates and dead-end metabolites

A kinetic pulse-labeling method was utilized in Fusarium culmorum to detect plausible biosynthetic intermediates and differentiate them from dead-end metabolites. The ultimate test to demonstrate a precursor relies on feeding experiments. We now report the detection of four new metabolites, one of them (compound 1) behaves as a dead-end metabolite, whereas compounds 2, 3, and 4 seem to be putative intermediates: they metabolize with time just when 3-acetyldeoxynivalenol (3-ADN) and/or sambucinol (SOL) start to be produced. Feeding experiments confirmed these results: compound 1 is not converted to 3-ADN or SOL, and compounds 2-4 are precursors to 3-ADN. In addition 3 is a precursor to SOL.     

Biological Modification of Trichothecene Mycotoxins: Acetylation and Deacetylation of Deoxynivalenols by Fusarium spp

Attempts were made to elucidate the acetyl transformation of novel trichothecene mycotoxins, 3a,7a,15-trihydroxy-12,13-epoxytrichothec-9-en-8-one (deoxynivalenol) and its derivatives, by trichothecene-producing strains of Fusarium nivale, F. roseum, and F. solani. In the peptone-supplemented Czapek-Dox medium, F. roseum converted 3a-acetoxy-7a,15-dihydroxy-12,13-epoxytrichothec-9-en-8-one (3-acetyldeoxynivalenol) to deoxynivalenol. 3-Acetyldeoxynivalenol was also deacetylated by intact mycelia of the three strains in sugar-free Czapek-Dox medium. The growing F. nivale acetylated deoxynivalenol to afford a small amount of 3-acetyldeoxynivalenol. 3a,7a,15-Triacetoxy-12,13-epoxytrichothec-9-en-8-one (7,15-diacetyl-deoxynivalenol), which was then deacetylated to give 7a-acetoxy-3a,15-dihydroxy-12,13-epoxytrichothec-9-en-8-one (7-acetyldeoxynivalenol). It was noted that the ester at C-7 was not hydrolyzed by the fungal mycelium.     

Occurrence of Gibberella zeae strains that produce both nivalenol and deoxynivalenol

By single ascospore isolation, several sets of asci containing eight ascospores were isolated from perithecia of Gibberella zeae. Of these sets, seven were investigated for their ability to produce 8-ketotrichothecene mycotoxins on rice grains. Analyses were made with gas chromatography-mass spectrometry and gas chromatography with 63Ni electron capture detection. Of 56 total isolates, 11 produced nivalenol, 4-acetylnivalenol, and deoxynivalenol, 1 produced nivalenol and deoxynivalenol, 7 produced deoxynivalenol and 3-acetyldeoxynivalenol, 19 produced deoxynivalenol and 15-acetyldeoxynivalenol, and 6 produced deoxynivalenol and both 15- and 3-acetyldeoxynivalenol. The remaining 12 isolates produced nivalenol and 4-acetylnivalenol. All isolates of G. zeae that we examined could produce 8-ketotrichothecenes in this investigation. This report is the first to demonstrate the presence of G. zeae isolates producing both nivalenol and deoxynivalenol. In addition, differences in the production between 3-acetyldeoxynivalenol and 15-acetyldeoxynivalenol are discussed in relation to culture conditions.     

Occurrence of Gibberella zeae strains that produce both nivalenol and deoxynivalenol.

By single ascospore isolation, several sets of asci containing eight ascospores were isolated from perithecia of Gibberella zeae. Of these sets, seven were investigated for their ability to produce 8-ketotrichothecene mycotoxins on rice grains. Analyses were made with gas chromatography-mass spectrometry and gas chromatography with 63Ni electron capture detection. Of 56 total isolates, 11 produced nivalenol, 4-acetylnivalenol, and deoxynivalenol, 1 produced nivalenol and deoxynivalenol, 7 produced deoxynivalenol and 3-acetyldeoxynivalenol, 19 produced deoxynivalenol and 15-acetyldeoxynivalenol, and 6 produced deoxynivalenol and both 15- and 3-acetyldeoxynivalenol. The remaining 12 isolates produced nivalenol and 4-acetylnivalenol. All isolates of G. zeae that we examined could produce 8-ketotrichothecenes in this investigation. This report is the first to demonstrate the presence of G. zeae isolates producing both nivalenol and deoxynivalenol. In addition, differences in the production between 3-acetyldeoxynivalenol and 15-acetyldeoxynivalenol are discussed in relation to culture conditions.     

Natural occurrence of Fusarium toxins in barley harvested during five years in an area of southwest Germany

A total of 44, 40, 47, 51, and 58 barley samples for feed use were collected randomly after the 1987, 1989, 1990, 1991, and 1992 crops, respectively, from farms located in an area of southwest Germany. The sum of precipitation from May to September was high in 1987 and markedly lower in 1989–1992. Deoxynivalenol, 3-. and 15-acetyldeoxynivalenol, nivalenol, fusarenon-X, T-2 toxin, HT-2 toxin and diacetxyscirpenol were determined by gas chromatography with mass selective detection (GC-MS), zearalenone,α- and β-zearalenol by GC-MS or by HPLC. Deoxynivalenol was the major toxin with incidences at 71–98% and mean contents at 42–400 μg/kg. In contrast, incidences of zearalenone, 3-acetyldeoxynivalenol, nivalenol, HT-2 toxin, and T-2 toxin were at 7–68, 7–48, 11–41, 0–9, and 2–29%, respectively; with mean contents at 3–146 μg/kg. α- and β-zearalenol and diacetoxyscirpenol were not detected in any sample. 15-acetyldeoxynivalenol and fusarenon-X were assayed in samples from 1987, 1991 and 1992. 15-acetyldeoxynivalenol was detected in 30, 0 and 2% of samples, respectively, with an average content of positive samples at 8 and 4 μg/kg, fusarenon-X was not detected. Over the years, incidences and levels of toxins remained constant, decreased or increased. The correlation between the occurrence of toxins and level of precipitation is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Isolation of 15-acetoxyscirpendiol from culture ofFusarium poae on corn

The main toxic metabolites of a strain ofFusarium poae, isolated from oats, were diacetoxyscirpenol (DAS) and a monoacetoxyscirpendiol. An accurate¹H and 13C NMR analysis allowed to identify the monoacetoxyscirpendiol as the 15-acetoxy-3α, 4 β - di hydroxy -12,13 - epoxy trichothec - 9 - ene (15-acetoxyscirpendiol). This is the first report on the production of 15 - acetoxyscirpendiol byFusarium poae.