Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus, the most notable ones being Aspergillus flavus and Aspergillus parasiticus. Their name is derived from the early work that discovered Aspergillus Flavus toxins. Aflatoxins are toxic and among the most carcinogenic substances known. After entering the body, Aflatoxins may be metabolized by the liver to a reactive epoxide intermediate or hydroxylated to become the less harmful Aflatoxin M1.
Aflatoxin-producing members of Aspergillus are common and widespread in nature. They can colonize and contaminate grain before harvest or during storage. Host crops are particularly susceptible to infection by Aspergillus following prolonged exposure to a high-humidity environment, or damage from stressful conditions such as drought, a condition that lowers the barrier to entry.
The native habitat of Aspergillus is in soil, decaying vegetation, hay, and grains undergoing microbiological deterioration, and it invades all types of organic substrates whenever conditions are favorable for its growth. Favorable conditions include high moisture content (at least 7%) and high temperature.
The toxin can also be found in the milk of animals that are fed contaminated feed.
Major types of Aflatoxins and their metabolites
At least 14 different types of Aflatoxin are produced in nature. Aflatoxin B1 is considered the most toxic and is produced by both Aspergillus flavus and Aspergillus parasiticus. Aflatoxin G1 and G2 are produced exclusively by A. parasiticus. While the presence of Aspergillus in food products does not always indicate harmful levels of Aflatoxin are also present, it does imply a significant risk in consumption
Aflatoxins M1, M2 were originally discovered in the milk of cows that fed on moldy grain. These compounds are products of a conversion process in the animal's liver. However, Aflatoxin M1 is present in the fermentation broth of Aspergillus parasiticus.
Aflatoxin B1 & B2, produced by Aspergillus flavus and A. parasiticus Aflatoxin G1 & G2, produced by Aspergillus parasiticus Aflatoxin M1, metabolite of Aflatoxin B1 in humans and animals (exposure in ng levels can come from a mother's milk) Aflatoxin M2, metabolite of Aflatoxin B2 in milk of cattle fed on contaminated foods Aflatoxicol Aflatoxin Q1 (AFQ1), major metabolite of AFB1 in in vitroliver preparations of other higher vertebrates
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