Aflatoxins

A family of bisfuranocoumarin metabolites of toxigenic strains of Aspergillus flavus and A. parasiticus.  The name derives from Aspergillus (a-), flavus (-fla-) and toxin. The major aflatoxins (AFs) are AFB1, B2, G1 and G2. The AFs are bioactivated by hepatic enzymes to toxic metabolites including AFB1-8,9-epoxide, and AFM1 (in milk). The AFs occur in the field in seeds (maize, cottonseed, groundnuts) and in storage of grains (maize, soybeans).

Biological effects are liver damage (acute and chronic) and liver cancer (chronic), reduced growth, impaired lipid absorption, with induced deficiencies of vitamins A, D and K, causing impaired blood coagulation, haemorrhage and bruises (poultry), and adverse reproductive effects. Differences in susceptibility between species of animals relate to the activity of hepatic cytochrome P450 enzymes, which bioactivate AF to the toxic metabolites. Rabbits, ducks and turkeys are highly susceptible to AF toxicity, while rats and sheep are

less sensitive. Chronic AF intoxication is caused by 0.25 ppm (dietary) in ducks and turkeys, 1.5 ppm in broilers, 0.4 ppm in swine and 7–10 ppm in cattle. AF metabolites in liver cross-link DNA strands, impairing cell division and protein synthesis. AFB1 metabolites form DNA adducts, causing liver cancer. AF has immunosuppressive effects, impairing cell-mediated immunity.