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Chapter: Modern Medical Toxicology: Food Poisons: Food Poisoning

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Fungi: Aflatoxins - Food Poisoning

Aflatoxins are naturally occurring bis-furanocoumarin compounds produced by the fungus Aspergillus flavus (and related species: A. parasiticus), and occur as contaminants of several nuts, grains, and seeds, such as peanuts, cottonseed, rye, barley, corn, etc.

Aflatoxins

Aflatoxins are naturally occurring bis-furanocoumarin compounds produced by the fungus Aspergillus flavus (and related species: A. parasiticus), and occur as contaminants of several nuts, grains, and seeds, such as peanuts, cottonseed, rye, barley, corn, etc. They are composed of highly substituted coumarin compounds that contain a fused dihydrofurofuran configuration. A dozen or more of these compounds have been identified: Aflatoxin, Aflatoxin B1, Aflatoxin B2, Aflatoxin B2a, Aflatoxin B3, Aflatoxin G1, Aflatoxin G2, Aflatoxin G2a, Aflatoxin M1, Aflatoxin M2, Aflatoxin P, and Aflatoxin T2. The aflatoxins are highly fluorescent. The “B” refers to blue, the “G” signifies green fluorescence, while “M” aflatoxins are fungal metabolites present in milk, and “T” compounds are found in tobacco. Most of them are associated with various types of liver damage. Aflatoxin B1 is a potent hepatotoxin and carcinogen.

Consumption of dietary aflatoxins varies from 10 to 200 ng/kg/day, though the recommended maximum daily intake should be less than 50 ng/kg/day.

Aflatoxins are usually encountered in the context of chronic exposure, via food intake or secondary to the handling of food-stuffs. Aflatoxins have been incriminated in the pathogenesis of the following conditions:

■■   Hepatitis, fatty liver, cirrhosis

■■   Hepatocellular carcinoma

■■   Hepatic failure

■■   Reye’s syndrome

■■   Kwashiorkor.

Aflatoxins accumulate in the presence of liver disease, and the association with hepatic cancer is confounded by the occurrence of hepatitis-B. The latter is not only a risk factor for liver cancer, but may also impair excretion of aflatoxins, causing further liver injury and DNA damage. Thus, it must be admitted that in these conditions it is not clear whether aflatoxin is a primary cause of the disease, is an incidental product which accumulates secondary to the disease process, or is a contrib-uting cause in association with other factors.

Aflatoxins can be detected in body fluids and tissues by RIA and ELISA. HPLC with fluorescence detection has also been used to detect and quantify aflatoxins in blood or tissue. Elevation of serum alkaline phosphatase is a good indicator of aflatoxin toxicity. In one study, there was a significant correla-tion between urinary levels of aflatoxins and the presence of hepatitis B surface antigen in serum, with risk of an increased incidence of heptatocellular carcinoma.

Treatment is mostly supportive. In one experimental study involving ducklings which were given 5 micrograms of aflatoxin and 50 mg of turmeric for 14 days, increased weight gain was seen compared to controls. Almost complete reversal of fatty changes, granular degeneration, and necrosis was observed. Antioxidants such as vitamin A have been shown in vitro to inhibit aflatoxin-induced DNA adduct formation.


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