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Mycotoxins are natural secondary metabolism products of mould fungi which are part of the foodstuff contaminants as a result of their toxic effect. Some mycotoxins always act against other micro-organisms, with the result that distinction from antibiotics is not always unambiguous. The risk to humans is primarily from the consumption of contaminated, i.e. mouldy foodstuffs. Some toxins can also be resorbed by inhalation or skin contact. The danger of mycotoxins is to be found in their chronically toxic properties of cancerogenicity, mutagenicity and teratogenicity. Acute poisoning with symptoms like vomiting and diarrhoea are only observed in toxins which belong to the group of the ? trichothecenes. The mycotoxins are absorbed by animals via their fodder and partly transmitted to animal foodstuffs (meat, eggs, milk). As a matter of principle, foodstuffs matured with mould fungi such as cheese and cooked meat as well as enzymes generated with mould fungi, vitamins and many more can be affected. The most important of the about 300 known mycotoxins are aflatoxins, citrinin, patulin, ochratoxin A, fumonisin and trichothecene ( desoxynivalenol, nivalenol, T2-toxin, HT2-toxin) and Zearalenon. However, mycotoxins are not only a problem for the health of man and animals. In agricultural production, considerable losses in yield and quality are caused all over the world by mould fungus infections. Above all, grain, oil seeds, coffee, fruit, vegetables and spices are affected. In more moderate climatic zones, it is mainly fungi of the Fusarium species which attack maize and grain. The measures for intensification and rationalisation in agriculture favour the propagation of the Fusarium fungi. The fusarium toxins formed by them include the large group of the àtrichothecenes, the àfumonisins and àZearalenon. The representatives of the B-trichothecenes àdesoxynivalenol and ànivalenol are found particularly frequently on grain. The A-trichothecene T2-toxin and HT2-toxin are proven above all in oats. In hotter areas, it is above all fungi of the Aspergillus species which contaminate peanuts, pistachios, figs, coffee, oil seeds and spices with à aflatoxins, the strongest orally effective natural cancerogens.
Aflatoxins (B1, B2, G1, G2) are exclusively formed by Aspergillus flavus and Aspergillus parasiticus cultures, which prosper particularly well with higher temperatures and air humidity. All examinations up to now indicate that Aflatoxin B1 is the main toxin, frequently occurring with B2 and/or G1/G2. particularly contaminated foodstuffs are peanuts, hazel nuts, almonds, pistachios, walnuts, dried fruit and spices. If fodder containing toxins (as a rule imported) is used, Aflatoxin M1 can be found in milk and milk products of the hydroxylated metabolite. Aflatoxin B1 is one of the strongest known carcinogens and has led to the formation of liver tumours in all test animals. Aflatoxin M1 is only slightly more weakly toxic, the cancer-forming effect is however distinctly reduced. For peanuts, husk fruits, dried fruits and grain intended for direct consumption or as a foodstuff ingredient, admissible maximum contents of 2 µg/kg Aflatoxin B1 and 4 µg/kg as an accumulation for B1 +B2 +G1+G2 have been stipulated. For Aflatoxin M1 in milk, the maximum figure of 0.05µg/kg applies. The maximum figure for baby and child nutrition is 0.05µg/kg B1 and 0,01 µg/kg M1 according to the Diet Ordinance.
Citrinin is a mycotoxin which is formed by many species of penicillium and aspergillus, some of them togetehr with àOchratoxin A. Rice is particularly frequently contaminated with the toxin; but it is also formed on other species of grain and in bread. Citrinin has phytotoxic, mutagenic, teratogenic and cancerogenic properties.
Desoxynivalenol (Vomitoxin) belongs to the group of the à B-Trichothecene mycotoxins. It is formed by fungi of the Fusarium species on wheat, maize, oats and barley. As a rule, the infection takes place on the field and leads to loss of harvest, reduction in quality, problems in the baking properties and in beer. In fodder, it leads to vomiting, diarrhoea, rejection of nutrition, inflammation of the gastrointestinal tract and many more besides in animals. However, it is very quickly metabolised in the body, and so there is no carry-over to meat products. In some states, maximum figures for grain of between 0.5 and 2 mg/kg have been stipulated. For baby food, maximum contents of 0.1 mg/kg are aimed for.
Fumonisins is the term used for a group of mycotoxins and phytotoxins formed by Fusaria. Up to now, these toxins have been almost exclusively proven on maize. As a result of infections on the field, particularly after maize as the first fruit, other species of grain can however also be affected. In animal tests, a cancerogenic effect was established on rats and mice for Fumonisin B1, the main representative of this group. In addition, fumonisins have neuro, nephro and pneumotoxic properties in various species of animals. In man, a connection with liver cell and oesophagus cancer is being discussed.
Nivalenol (NIV) belongs to the group of the à B-Trichothecene mycotoxins, which are metabolic products of fungi of the Fusarium species. It is mainly formed on oats, wheat and barley. Nivalenol has a strongly haemorrhagic and skin-irritating effect. Consumption of contaminated foods leads to dizziness, vomiting and internal haemorrhages, which can be fatal. Like all trichothecenes, Nivalenol inhibits protein biosynthesis. The LD50 for mice is 4.1 mg/kg (i.p.).
Ochratoxin A (OTA), a chlorinated natural material, can be formed by Aspergillus and Penicillium species on practically all foodstuffs, in particular during storage. Most OTA producers can form further mycotoxins such as à Citrinin and penicillin acid. With an LD50 of 1 mg/kg in dogs and 0.62 mg/kg in pigs, OTA has a high acute toxicity. In chronic consumption, it has a damaging effect on the kidneys and the immune system and caused cancer in animal tests. Examinations by the Federal Institute for Concumer Protection in Health Matters and Veterinary Medicine (BgVV) show that not only grain and grain products, but also coffee and beer are amongst the foodstuffs which make a considerable contribution to OTA contamination. Via moulded fodder, OTA enters animals and, finally, meat and animal products, but not beef and milk, as OTA is decomposed in the paunch of cattle. The Scientific Foodstuffs Commission of the EU has set the tolerable daily OTA consumption at 5 ng/kg body weight. According to latest examinations, this figure is only reached on average by about 10% of cases in Germany. In the EU, a maximum figure of 3 µg/kg for foodstuffs is currently being discussed.
The mycotoxin Patulin is a metabolic product of a number of different mould fungi such as Penicillium patulum, P urticae, P. chrysogenum, P. roqueforti, Aspergillus clavatus, A. terreus und Byssochlamys nivea, which can be found on grain, bakery and meat products. It is often formed together with à Citrinin. Patulin is found relatively frequently in putrefied fruit and thus enters the corresponding fruit juices. Patulin is destroyed during fermentation or in addition of SO2, which means that wine and fruit wines are free of Patulin as a rule. Patulin has a damaging effect on the genotype by initiating breakages in the DNA. In addition, enzymes containing SH are deactivated. Many European countries have set the maximum figure at 50 µg/l. In Germany, there is not yet such a regulation.
Zearalenon is a estrogenically active mycotoxin which is formed by various species of Fusarium. The preferred substrate for fungi forming Zearalenon is maize and oats, but other species of grain can also be strongly attacked. As Zearalenon is formed in a very late phase of development of the fungus, it can be found above all in grain with large amounts of fungus. Higher contents are found in maize as a rule, as removal of strongly attacked corns is not so effective as in bread grain. Zearalenon is not acutely toxic, but a carcinogenic effect is assumed. For meadow animals, it results in disturbances of fertility, miscarriages and foetal deaths.
Trichothecenes is the name given to a group of about 100 mycotoxins which can be formed by Fusaria on grain and grain products. Trichothecenes have a broad spectrum of biological effects - they can be phytotoxic, insecticide, fungicide, anti-viral and cytotoxic. The common thing for all of them is contact toxicity. Generally, trichothecenes inhibit protein biosynthesis in mammals' cells, partly from concentrations of 1 ng/ml. Poisoning with trichothecenes leads to vomiting, diarrhoea, rejection of food, inflammations of the gastrointestinal tract, impairment of nerve cells, heart muscle, lymphatic system, testes, thymus and formation of tissue necroses. Poisoning of animals and man have been described in various countries, e.g. "moldy corn toxicose" in the USA, "bean-hull toxicose" in Japan or "alimentary toxic aleukia" in the USSR. According to their chemical structure, the trichothecenes are divided into Groups A-D. Important representatives are à Nivalenol, à Desoxynivalenol, à Fusarenon-X, T-2-toxin and HT-2-toxin.
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