207
with the addition of corn oil. The levels of AFB1 in full-fat substrates were also
higher than in the defatted substrates. Therefore processing complementary foods
from full-fat cereals and legumes may increase the potential of aflatoxin contamination (Achaglinkame et al. 2017).
12.9.3 Classification of Aflatoxin
Among the mycotoxins, aflatoxins are most intensively sought because of their
immunotoxicity acting on phagocytes and cell-mediated immunity (Bondy & Pestka
2000). Among 18 different types of the identified AFs, the major ones are AFB1 and
AFB2. Due to hazardous nature of AFs to humans and animals, the European Union
in the Commission Regulation No. 1881/2006 has set the maximum levels (MLs) of
AFs in cereals and their derivatives as 2 g kg
−1
for AFB1 and 4 g kg
−1
for total AFs
(AFs B1, B2, G1, and G2) (Hashemi et al. 2014). Aflatoxin M1 (AFM1) is the major
oxidized metabolite of AFB1, and milk and dairy products may be contaminated by
feed carry-over contamination (Campone et al. 2016).
Aflatoxins are classified according to their physical–chemical and toxicological
characters in the most dangerous row of the mycotoxins. These aflatoxins are in part
responsible of irreversible medical disasters that are not easily manageable such as
cancer of the liver and kidneys and, in the other part, of losses in the stored cereal
products (Gacem and El Hadj-Khelil 2016).
Aflatoxins (AFs) are dihydrofuranocoumarin metabolites of food fungi
Aspergillus flavus, and A. parasiticus, well known for AFB1 which is most toxic.
Aflatoxins B1, B2, G1, and G2 are most significant contaminants to rice. Two other
metabolites, aflatoxins M1 and M2, can be separated from milk (Sun et al. 2017).
12.9.4 Structure and Function of Aflatoxin Molecules
Aflatoxins are chemically difurocoumarin derivatives derived from polyketide pathway. Recently, genetic studies by Payne and Brown (1998) on aflatoxin-producing
fungi have given an interesting insight and led to the cloning of 17 genes responsible for 12 enzymatic conversions in the aflatoxin biosynthetic pathway. The physical factors influencing the pathway have been found out, but the exact role played
by them is not yet clear. The pathway-specific regulation occurs by a Zn(II) 2 Cys 6
DNA binding protein that regulates the transcription of all pathway genes. Presently,
18 different types of aflatoxins have been identified, with aflatoxins B1, B2, G1, G2,
M1, and M2 being the most common. Of these, aflatoxin B1 (AFB1) and G1 (AFG1)
occur most frequently, with AFB1 being the most potent. Physicochemical and biochemical characteristics of the AFB1 molecule reveal two important sites for toxicological activity. The first site is the double bond in position 8,9 of the furofuran
12 Fungal Mycotoxins
with the addition of corn oil. The levels of AFB1 in full-fat substrates were also
higher than in the defatted substrates. Therefore processing complementary foods
from full-fat cereals and legumes may increase the potential of aflatoxin contamination (Achaglinkame et al. 2017).
12.9.3 Classification of Aflatoxin
Among the mycotoxins, aflatoxins are most intensively sought because of their
immunotoxicity acting on phagocytes and cell-mediated immunity (Bondy & Pestka
2000). Among 18 different types of the identified AFs, the major ones are AFB1 and
AFB2. Due to hazardous nature of AFs to humans and animals, the European Union
in the Commission Regulation No. 1881/2006 has set the maximum levels (MLs) of
AFs in cereals and their derivatives as 2 g kg
−1
for AFB1 and 4 g kg
−1
for total AFs
(AFs B1, B2, G1, and G2) (Hashemi et al. 2014). Aflatoxin M1 (AFM1) is the major
oxidized metabolite of AFB1, and milk and dairy products may be contaminated by
feed carry-over contamination (Campone et al. 2016).
Aflatoxins are classified according to their physical–chemical and toxicological
characters in the most dangerous row of the mycotoxins. These aflatoxins are in part
responsible of irreversible medical disasters that are not easily manageable such as
cancer of the liver and kidneys and, in the other part, of losses in the stored cereal
products (Gacem and El Hadj-Khelil 2016).
Aflatoxins (AFs) are dihydrofuranocoumarin metabolites of food fungi
Aspergillus flavus, and A. parasiticus, well known for AFB1 which is most toxic.
Aflatoxins B1, B2, G1, and G2 are most significant contaminants to rice. Two other
metabolites, aflatoxins M1 and M2, can be separated from milk (Sun et al. 2017).
12.9.4 Structure and Function of Aflatoxin Molecules
Aflatoxins are chemically difurocoumarin derivatives derived from polyketide pathway. Recently, genetic studies by Payne and Brown (1998) on aflatoxin-producing
fungi have given an interesting insight and led to the cloning of 17 genes responsible for 12 enzymatic conversions in the aflatoxin biosynthetic pathway. The physical factors influencing the pathway have been found out, but the exact role played
by them is not yet clear. The pathway-specific regulation occurs by a Zn(II) 2 Cys 6
DNA binding protein that regulates the transcription of all pathway genes. Presently,
18 different types of aflatoxins have been identified, with aflatoxins B1, B2, G1, G2,
M1, and M2 being the most common. Of these, aflatoxin B1 (AFB1) and G1 (AFG1)
occur most frequently, with AFB1 being the most potent. Physicochemical and biochemical characteristics of the AFB1 molecule reveal two important sites for toxicological activity. The first site is the double bond in position 8,9 of the furofuran
12 Fungal Mycotoxins