Monday, June 14, 2021

Aflatoxin B1

Aflatoxins are a class of carcinogenic mycotoxins produced by Aspergillus fungi and are known to contaminate a large portion of the world's food supply.

The aflatoxins consist of about 20 similar compounds belonging to a group called the difuranocoumarins, but only four are naturally found in foods.

These are aflatoxins B1, B2, G1 and G2. They are particularly dangerous to humans and animals as they have been found in all major food crops; but most human exposure comes from contaminated nuts, grains and their derived products.

Aflatoxin B1 (AFB1) is the most potent of these compounds and has been well-characterized to lead to the development of hepatocellular carcinoma (HCC) in humans and animals.

Its carcinogenicity and immunosuppression capacity have been extensively reported in all kind of animals, including poultry, trout, cattle and rats with different incidence across species, gender and age.

Additionally, aflatoxin M1 (AFM1), a product of aflatoxin B1 (AFB1) metabolism, can be found in milk in areas of high aflatoxin exposure. Subsequently humans may be exposed to this aflatoxin through milk and milk products, including breast milk, especially in areas where the poorest quality grain is used for animal feed.

Aflatoxin B1 (AFB1) is a secondary metabolite produced by Aspergillus flavus and Aspergillus parasiticus when environmental factors are favourable. It has also been characterized as a biological toxin.

AFB1 is characterized by the fusion of a cyclopentenone ring to the lactone ring of the coumarin structure and by strong fluorescence emission in the blue region (hence the designation B) when exposed to ultraviolet light.

AFB1 which is the most prevalent and most potent, a human health hazard globally, has a peculiar double bond in the cyclic ring which is also observed in G1 and M1. For activation, AFB1 requires epoxidation to aflatoxin B1 2,3-epoxide. The microsomal cytochrome P450 (CYP450) monoxygenases biotransform the toxin to the less toxic metabolites aflatoxins M1 and G1.

Currently, many countries employ strict regulations to keep levels of AFB1 (and other aflatoxins) low in foods. Acceptable limits of AFB1 in foods intended for human consumption range from approximately 0 - 40 parts per billion (ppb) whereas levels in animal feed are allowed to be much higher, reaching upwards of 300 ppb.
Aflatoxin B1

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