Mycotoxins and Classes

Mycotoxins and Classes

Defination of Mycotoxins

          Mycotoxin is a toxin produced by a fungus under special conditions of moisture and temperature. Mycotoxins are toxic substances produced by fungi (molds) growing on crops/grains in the field or in storage.

Myco = of fungal origin

These toxins are secondary metabolites.

Origin of Mycotoxins

The Mycotoxins were first reported in birds in 1960’s in Brazil. The first mycotoxin was Alfatoxins.

Major Classes of Mycotoxins

 1 Aspergillus
 2 Penicillium
 3. Fusarium
Table Shows Mycotoxins belonging to various Fungi

Fungi	Substrate	Mycotoxin
Aspergillus flavus	Maize, groundnut, oilseed, cotton seed	Aflatoxin
Aspergillus parasiticus	Maize, groundnut, oilseed, cotton seed	Aflatoxin
Aspergillus nomius	Maize, groundnut, oilseed, cotton seed	Aflatoxin
Aspergillus ochraceus	Barkey wheat	Ochratoxin
Aspergillus carbonerius	Grapes wine coffee	Ochratoxin
Fusarium oxysporum	Wheat barley maize	Fumonisins
Fusarium sp.	Wheat barley maize	T-2 toxin
Penicillium verrucosum	Wheat barley maize	Ochratoxin
Claviceps purpurea	Rye	Ergot alkaloids
Stachybotrys	hay	satratoxins

                 Mycotoxins are toxic compounds produced by different types of fungus, belonging mainly to the Aspergillus, Penicillium andFusarium genera. Under favourable environmental conditions, when temperature and moisture are conducive, these fungi proliferate and may produce mycotoxins. They commonly enter the food chain through contaminated food and feed crops, mainly cereals.

                The presence of mycotoxins in food and feed may affect human and animal health as they may cause many different adverse health effects such as induction of cancer and mutagenicity, as well as estrogenic, gastrointestinal and kidney disorders. Some mycotoxins are also immunosuppressive reducing resistance to infectious disease.

Major groups

           Aflatoxins are a type of mycotoxin produced by Aspergillus species of fungi, such as A. flavus and A. parasiticus. The umbrella term aflatoxin refers to four different types of mycotoxins produced, which are B1, B2, G1, and G2. Aflatoxin B1, the most toxic, is a potentcarcinogen and has been directly correlated to adverse health effects, such as liver cancer, in many animal species. Aflatoxins are largely associated with commodities produced in the tropics and subtropics, such as cotton, peanuts, spices, pistachios and maize. 

           Ochratoxin is a mycotoxin that comes in three secondary metabolite forms, A, B, and C. All are produced by Penicillium and Aspergillusspecies. The three forms differ in that Ochratoxin B (OTB) is a nonchlorinated form of Ochratoxin A (OTA) and that Ochratoxin C (OTC) is an ethyl ester form Ochratoxin A.  Aspergillus ochraceus is found as a contaminant of a wide range of commodities including beveragessuch as beer and wine. Aspergillus carbonarius is the main species found on vine fruit, which releases its toxin during the juice making process. OTA has been labeled as a carcinogen and a nephrotoxin, and has been linked to tumors in the human urinary tract, although research in humans is limited by confounding factors. 

          Citrinin is a toxin that was first isolated from Penicillium citrinum, but has been identified in over a dozen species of Penicillium and several species of Aspergillus. Some of these species are used to produce human foodstuffs such as cheese (Penicillium camemberti), sake,miso, and soy sauce (Aspergillus oryzae). Citrinin is associated with yellow rice disease in Japan and acts as a nephrotoxin in all animal species tested. Although it is associated with many human foods (wheat, rice, corn, barley, oats, rye, and food colored with Monascuspigment) its full significance for human health is unknown. Citrinin can also act synergistically with Ochratoxin A to depress RNA synthesisin murine kidneys. 

       Ergot Alkaloids are compounds produced as a toxic mixture of alkaloids in the sclerotia of species of Claviceps, which are common pathogens of various grass species. The ingestion of ergot sclerotia from infected cereals, commonly in the form of bread produced from contaminated flour, cause ergotism the human disease historically known as St. Anthony's Fire. There are two forms of ergotism: gangrenous, affecting blood supply to extremities, and convulsive, affecting the central nervous system. Modern methods of grain cleaning have significantly reduced ergotism as a human disease, however it is still an important veterinary problem. Ergot alkaloids have been used pharmaceutically. 

          Patulin is a toxin produced by the P. expansum, Aspergillus, Penicillium, and Paecilomyces fungal species. P. expansum is especially associated with a range of moldy fruits and vegetables, in particular rotting apples and figs. It is destroyed by the fermentationprocess and so is not found in apple beverages, such as cider. Although patulin has not been shown to be carcinogenic, it has been reported to damage the immune system in animals. In 2004, the European Community set limits to the concentrations of patulin in food products. They currently stand at 50 μg/kg in all fruit juice concentrations, at 25 μg/kg in solid apple products used for direct consumption, and at 10 μg/kg for children's apple products, including apple juice.

        Fusarium toxins are produced by over 50 species of Fusarium and have a history of infecting the grain of developing cereals such as wheatand maize. They include a range of mycotoxins, such as: the fumonisins, which affect the nervous systems of horses and may cause cancer in rodents; the trichothecenes, which are most strongly associated with chronic and fatal toxic effects in animals and humans; and zearalenone, which is not correlated to any fatal toxic effects in animals or humans. Some of the other major types ofFusarium toxins include: beauvercin and enniatins, butenolide, equisetin, and fusarins.