Other Fusarium Toxins

Fusarium species produce various other toxic metabolites. Fusarin C (9.10) is a mutagenic metabolite of F. monoliforme. The fumonisins, e.g. 9.11, are another group of mycotoxins that have been isolated from this fungus. They have been associated with a high incidence of esophageal cancer and several animal diseases. The simple molecule monoliformin (9.12) is also a toxin. 

Zearalenone (9.13) is a mycotoxin with estrogenic activity and suspected 

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Detection methods for T-2 toxin and other Fusarium toxins have been recently reviewed (Krska et al., 2007 Ler et al., 2006). Trichothecene analysis can be done by screening methods such as thin layer chromatography (TLC) and ELISA or analytical methods such as gas chromatography (GC) and high performance hquid chromatography (HPLC). GC instrumentation has been the most frequently used method for experimental work with trichothecenes. Newer methodologies, such as GC-MS and LC-MS, have an excellent lowest level of detection (LOD) of 5 ng/g for T-2 toxin in cereals and food, and wheat flour respectively (Ler et al., 2006). Improved sensitivity for... 

To conclude, DON occurrence is almost exclusively associated with cereals, and the levels of occurrence are in the order of hxmdreds of pg/kg upwards. DON occurs as a field (preharvest) rather than a storage contarninant, and almost always co-occurs with other Fusarium toxins. Preventive measures are difficult to implement, and even the effect of fungicide treatment on DON levels is controversial (Edwards et al., 2001). As seasonal variations significantly influence the extent of Fusarium infections, levels of DON tend to... 

The maximum levels for T-2 and HT-2 are still under consideration. An indicative level for the sum of T2 and HT-2 was set in 2013 (Commission Recommendation 2013/165/ EU, European Commission, 2013). It is 200 gg/kg for barley (including malting barley) and 50 gg/kg for processed cereals. According to this recommendation, member states should also collect more data on the occurrence of T-2 and HT-2 in cereal and cereal products. Furthermore, more information is needed on year-to-year variation, the effects of food processing and agronomic factors on the presence of these toxins. It is also encouraged that samples be simultaneously analysed for the presence of T-2 and HT-2 and other Fusarium toxins, since they often co-occur in the samples. 

Miller, J.O., Young, I.C. and Trenholm, H.L., Fusarium toxins in field corn. I. Parameters associated with fungal growth and production of deoxynivaneol and other mycotoxins. Can. J. Bot., 61, 3080, 1983. 

Several surveys suggest that the most prevalent trichothecenes are deoxynivalenol (DON), nivalenol, 3-acetyl-DON (3-AcDON) and 15-acetyl-DON (15-AcDON), as type-B trichothecenes, and HT-2 toxin and T-2 toxin, as type-A trichothecenes. They are mainly found on maize, oats, barley, and wheat. The latter, espedally durum wheat, which is used nearly exclusively for the production of pasta, is susceptible to Fusaria infection and is often highly contaminated with DON. In European agricultural commodities type-A trichothecenes usually occur less frequently and at lower concentrations than DON. The simultaneous occurrence of DON with other Fusarium mycotoxins mainly type-B trichothecenes and zearalenone, has been reported for a variety of agricultural commodities (Gareis et al., 1989 Petterson, 1992, as cited in Krska et al., 2001). 

Fusarium toxins, also called trichothecenes. Other mycotoxins are also encountered but to a lesser extent, and consecutively they are of less concern for public authorities cyclotropiazonic acid, sterigmatocystin, pe-nitrem A, and tenuazonic acid. The structures of these mycotoxins are shown in Figures 1-10. 

Several Fusarium toxins such as DON, fumonisins, fusarenon-x, fusaric acid, nivalenol, T-2, HT-2 and ZEA are prone to masking biofransformations or binding by plants (Berthiller et al., 2013). In addition, other mycotoxins such as OTA and patulin have been found in conjugated forms. The major form of modified DON is deoxynivalenol-3-p-D-glucopyranoside (D3G), which is perhaps the most widely studied cereal-associated modified mycotoxin so far. 

However, for surveillance studies, trichothecene mycotoxins coexist with other trichothecenes, and a simultaneous analytical method for the determination of some trichothecenes and Fusarium toxins is considered to be more practical than a single method. A decade ago, GC was very popular to analyze some trichothecene mycotoxins in food, but for GC analysis, various derivatives are needed that are sometimes troublesome. 

C]-4-hydroxymyoporone with the fungus, Fusarium solani, a common fungal contaminant of sweet potatoes, demonstrated that 49 can serve as a precursor to the lung toxins (Burka et al, 1977). A retroaldol reaction would convert 4-hydroxymyoporone (49) into ipomeanine (47). Reduction of 47 would then lead to the other lung toxins, 45, 46, and 48. 

T2 mycotoxin was used as the antigen. Fusarium tricinctum during cultivation may form about 9 g of T2 toxin per 1 kg of the solid or liquid substrate with the final output of the crystalline product about 2-3 g/kg [24-26]. T2 mycotoxin is sometimes referred to as the biological weapon of omnicide [27-29] since its toxicity is more than 400 times higher than most other biological warfare agents [30]. 

Phomopsin A (83 in Figure 18) was isolated from Phomopsis leptostromiformis as the hepatotoxic metabolite responsible for lupinosis, which is a disease in animals caused by ingestion of Lupinus species infected with the fungus.169 Penicillium species produce other significant mycotoxins such as penitrem A (84), PR toxin (85), and rubratoxin B (86).170 Fusarin C (87) and fusaproliferin (88) are known as mycotoxins produced by Fusarium... 

Trichothecene 3-O-acetyltransferase encoded by a noncluster gene, TrilOl, readily converts isotrichodermol (130) into isotrichodermin (ITD, 131) (Figure 30).262 263 This acetylation step is important for the selfprotection of trichothecene-producing Fusarium species. The C-3 acetyl is also essential for subsequent biosynthetic steps to proceed. Indeed, the 7W/0/--targeted gene disruption mutant of F. sporotrichioides could not metabolize 3-hydroxytrichothecenes, but efficiently converted exogenously added ITD (131) and other C-3 acetylated intermediates into T-2 toxin.264 After ITD (131), the biosynthetic pathways are different between type A and type B trichothecenes. 

The regulatory issues are less well-defined for mycotoxins other than aflatoxins. But with increasing data on specific toxicity of Fusarium mycotoxins such as fiimonisins, regulatory guidelines are being considered for these toxins as well. For example, in the USA, advisory limits exist for deoxynivalenol (DON) at 5-lOmg/kg (5-10 parts per million ppm) in animal feeds [7]. 

Fumonisins are a group of toxins produced primarily by Fusarium verticil-lioides (formerly called F moniliforme), Eprolifemtum and other related species which readily colonize corn all over the world [120-124]. Nine structurally related fumonisins including Bj, B2, B3, B4, A, and A2, have been described (fig. 8). Chemically, fiimonisin Bj is a derivative (diester) of propane-1,2,3-tricarboxylic acid of 2-amino-12,16-dimethyl-3,5,10,14,15-pentahydroxy-icosane [121-130]. The other fumonisins lack the tricarballylic acid or other ester groups [121, 131, 132]. Fumonisins are chemically similar in structure to toxins (AAL) produced by Altemaria altemata [133]. Production of fumonisins hy Altermria has also been reported [134,135], and some fumonisin-producing Fusaria have been knovm to produce AAL toxins [136]. 

Trichothecenes occur worldwide in grains and other commodities grown in cooler climates. Colonization and toxin production by Fusarium spp. occur in the field however, some toxin production can also occur in storage. Mild temperatures tend to encourage fungal growth and cool temperatures increase toxin production (0-15°C). Trichothecenes tend to be produced in toxic concentrations in years of wet weather when harvests are delayed and prolonged. 

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