Aflatoxins: Contamination, Analysis and Control

Abstract

Aflatoxins are toxic metabolites produced by different species of toxigenic fungi, called mycotoxins. Humans can be exposed to aflatoxins by the periodic consumption of contaminated food, contributing to an increase in nutritional deficiencies, immunosuppresion and hepatocellular carcinoma (Wagacha & Muthomi, 2008). Aflatoxins (AFs) have a wide occurrence in different kind of matrices, such as spices, cereals, oils, fruits, vegetables, milk, meat, etc. Among the 18 different types of aflatoxins identified, the major members are aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2), M1 (AFM1) and M2 (AFM2) which are produced by Aspergillus flavus and/or Aspergillus parasiticus. Strains of A. flavus can vary from non-toxic to highly toxigenic and are more likely to produce AFB1 than AFG1. Strains of A. parasiticus generally have less variation in toxigenicity and produce AFB1 and varying amounts of AFB2, AFG1 and AFG2 (Coppock & Christian, 2007). Other fungi have been described in the literature as aflatoxins’ producers such as A. bombycis, A. ochraceoroseus and A. pseudotamari (Klich et al, 2000; Mishra & Das, 2003). A. flavus and A. fumigatus have also been identified as pathogens for animals and humans (Zain, 2011). The order of acute and chronic toxicity is AFB1 > AFG1 > AFB2 > AFG2, reflecting the role played by epoxidation of the 8,9-double bond and also the greater potency associated with the cyclopentenone ring of the B series, when compared with the six-membered lactone ring of the G series. AFM1 and AFM2 are hydroxylated forms of AFB1 and AFB2 (Mclean & Dutton, 1995; Wogan, 1966). In the primary fungi metabolism a lot of interrelated reactions catalyzed by enzymes occur, with the objective of promoting energy and primary metabolites (synthetic intermediates and macromolecules), ensuring the growth and reproduction of fungi. Secondary