aflatoxin

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Aflatoxin

Any of a group of secondary metabolites produced by the common molds Aspergillus flavus and A. parasiticus that cause a toxic response in vertebrates when introduced in low concentration by a natural route. The group constitutes a type of mycotoxin. The naturally occurring aflatoxins are identified in physicochemical assays as intensely blue (aflatoxins B1 and B2) or blue-green (aflatoxins G1 and G2) fluorescent compounds under long-wave ultraviolet light. The common structural feature of the four major aflatoxins is a dihydrodifurano or tetrahydrodifurano group fused to a substituted coumarin group (see illustration). The relative proportions of the four major aflatoxins synthesized by Aspergillus reflect the genetic constitution of the producing strain and the parameters associated with fungal growth. In addition, derivative aflatoxins are produced as metabolic or environmental products. See Toxin

Structures of major naturally occurring aflatoxinsenlarge picture
Structures of major naturally occurring aflatoxins

Aflatoxins are formed through a polyketide pathway involving a series of enzymatically catalyzed reactions. In laboratory cultures, aflatoxins are biosynthesized after active growth has ceased, as is typical for secondary metabolites. By using blocked mutants and metabolic inhibitors, many of the intermediates have been identified as brightly colored anthraquinones.

Aflatoxins are potent molecules with many biological effects. They are toxigenic, carcinogenic, mutagenic, and teratogenic in various animal species. Aflatoxin B1 is usually the most abundant naturally occurring member of the family, and most studies on the pharmacological activity of aflatoxin have been conducted with this congener. Aflatoxin B1 is the most potent hepatocarcinogenic agent known, although the liver by no means is the only organ susceptible to aflatoxin carcinogenesis. Aflatoxin is listed as a probable human carcinogen by the International Agency for Research on Cancer. See Plant pathology

Aflatoxins are a major agricultural problem. Contamination can occur in the field, during harvest, or in storage and processing. Corn, rice, cottonseed, and peanuts are the major crops regularly displaying high levels of aflatoxin contamination. Since A. flavus and A. parasiticus are nearly ubiquitous in the natural environment, numerous other grain, legume, nut, and spice crops, as well as coffee and cocoa, have been reported to contain aflatoxins. Given the potential of aflatoxins as human carcinogens and their known activity as toxins in animal feeds, many international regulatory agencies monitor aflatoxin levels in susceptible crops. Prevention is the main line of defense against aflatoxins entering the food chain. Moisture, temperature, and composition of the substrate are the chief factors affecting fungal growth and toxin production. In the field, insect damage is often involved. Detoxification is a last line of defense. Several commercially feasible methods of ammoniation have been developed for reducing levels of aflatoxin contamination in animal feeds. See Agronomy, Mycotoxin

aflatoxin

[‚af·lə′täk·sin]
(biochemistry)
The toxin produced by some strains of the fungus Aspergillus flavus, the most potent carcinogen yet discovered.
References in periodicals archive ?
In the European Union, the limit for aflatoxin M1 is 50ppt in raw milk, heat treated milk, and milk for the manufacture of milk-based products.
The AuroFlow Aflatoxin M1 Strip Test Kit is Bioo Scientific's latest addition to its line of kits for mycotoxin detection.
By yesterday, milk from four dairy farms and three sheep farms was found with higher than permissible levels of aflatoxin M1.
He claimed the feed had arrived in Cyprus already contaminated with aflatoxin M1, in full knowledge of veterinary service officials, and been sold on the cheap.
Unfortunately there is still no clear-cut answer, four days after it was first reported that there were increased levels of the carcinogenic substance aflatoxin M1 in quantities of milk that had been tested.
At booth number 617, Bioo Scientific is showcasing testing solutions for a number of applications including rapid strip tests for histamine detection in seafood, milk, wine and cheese, aflatoxin M1 in milk, and fluoroquinolone in milk and meat.