Kontakt 2012, 14(1):85-93 | DOI: 10.32725/kont.2012.010

Aflatoxins - toxic effects in manBiomedicine - Review

František Malíř^1,*, Vladimír Ostrý²

¹ Univerzita Hradec Králové, Přírodovědecká fakulta, katedra biologie

² Státní zdravotní ústav Praha, Centrum zdraví, výživy a potravin v Brně

Aflatoxins are secondary metabolites of toxinogenic fibrous microscopic fungi (moulds) of the genus Aspergillus, particularly of the species Aspergillus flavus (producer of aflatoxin B1/ (henceforth AFB1/ and AFB2) and Aspergillus parasiticus (producer of AFB1, AFB2, AFG1 and AFG2), which occur in foodstuffs and forages. Aflatoxins are obviously most known and most thoroughly examined mycotoxins worldwide. In terms of their chemical nature, they are polycyclic, unsaturated, high-substituted coumarins. About 20 aflatoxins have been still identified, among which only AFB1, AFB2, AFG1 and AFG2 occur in nature. AFB1 occurs most frequently and is most important in terms of toxicology. The mechanism of its action is rather complicated. It becomes toxic only after a metabolic activation with microsomal cytochrome P-450-dependent oxidases to active metabolite AFB1-8,9-epoxide. This form is very reactive and is bound to cellular macromolecules - proteins, RNA and DNA. In the case of DNA, it exerts preference binding to the site of N7-guanine and forms a stable adduct with this base, which is responsible for AFB1 mutagenic and carcinogenic effects. The development of primary hepatocellular carcinoma after nutritional exposure to AFB1 is obviously caused by the point mutation of codone 249 of the tumour suppressor gene p53. In addition, aflatoxins are associated with different diseases - aflatoxicoses in farm animals, domestic animals and man. The contamination of food raw materials and foodstuffs with aflatoxins occurs in natural ways and cannot be prevented or completely eliminated before the harvest, after the harvest and in technology processing even when adhering to the good agricultural and technology practice. Higher attention is being paid to aflatoxins compared to other mycotoxins, particularly given the fact that their carcinogenity and acute toxic effects were demonstrated in susceptible laboratory animals and humans. The medicine Oltipraz [5-(2-pyrazinyl)-4-metyl-l,2-dithiol-3-thione] considerably blocks the aflatoxin B1-mediated carcinogenesis in the liver of laboratory rats in the course of their exposure. Oltipraz has not yet been sufficiently tested as a medicine for the treatment of aflatoxin B1-induced hepatocarcinoma in humans.

Keywords: aflatoxins; moulds; toxicity; aflatoxicosis; mechanism of action; carcinogenity; therapy; Oltipraz

Received: December 17, 2011; Accepted: February 22, 2012; Published: March 16, 2012  Show citation