Chapter 30
Mycotoxins
A very large number of molds produce toxic substances designated mycotoxins. Some are mutagenic
and carcinogenic, some display specific organ toxicity, and some are toxic by other mechanisms.
Although the clear-cut toxicity of many mycotoxins for humans has not been demonstrated, the effect
of these compounds on experimental animals and their effect in in vitro assay systems leaves little
doubt about their real and potential toxicity for humans. At least 14 mycotoxins are known to be
carcinogens, with the aflatoxins being the most potent.
84 It is generally accepted that about 93% of
mutagenic compounds are carcinogens. With mycotoxins, microbial assay systems reveal an 85%
level of correlation between carcinogenicity and mutagenesis.
84
Mycotoxins are produced as secondary metabolites. The primary metabolites of fungi as well as for
other organisms are those compounds that are essential for growth. Secondary metabolites are formed
during the end of the exponential growth phase and have no apparent significance to the producing
organism relative to growth or metabolism. In general, it appears that they are formed when large
pools of primary metabolic precursors such as amino acids, acetate, pyruvate, and so on, accumulate.
The synthesis of mycotoxins represents one way the fungus has of reducing the pool of metabolic
precursors that it no longer requires for metabolism.
Some methods for the detection of mycotoxins in foods can be found in Chapter 11. For an extensive
review of these substances in fruits, fruit juices, and dried fruits, see reference 27.
AFLATOXINS
Aflatoxins are clearly the most widely studied of all mycotoxins. Knowledge of their existence dates
from 1960, when more than 100,000 turkey poults died in England after eating peanut meal imported
from Africa and South America. From the poisonous feed were isolated Aspergillus flavus, and a
toxin produced by this organism that was designated aflatoxin (Aspergillus flavus toxin—A-fla-toxin).
Studies on the nature of the toxic substances revealed the following four components:
709
Mycotoxins
A very large number of molds produce toxic substances designated mycotoxins. Some are mutagenic
and carcinogenic, some display specific organ toxicity, and some are toxic by other mechanisms.
Although the clear-cut toxicity of many mycotoxins for humans has not been demonstrated, the effect
of these compounds on experimental animals and their effect in in vitro assay systems leaves little
doubt about their real and potential toxicity for humans. At least 14 mycotoxins are known to be
carcinogens, with the aflatoxins being the most potent.
84 It is generally accepted that about 93% of
mutagenic compounds are carcinogens. With mycotoxins, microbial assay systems reveal an 85%
level of correlation between carcinogenicity and mutagenesis.
84
Mycotoxins are produced as secondary metabolites. The primary metabolites of fungi as well as for
other organisms are those compounds that are essential for growth. Secondary metabolites are formed
during the end of the exponential growth phase and have no apparent significance to the producing
organism relative to growth or metabolism. In general, it appears that they are formed when large
pools of primary metabolic precursors such as amino acids, acetate, pyruvate, and so on, accumulate.
The synthesis of mycotoxins represents one way the fungus has of reducing the pool of metabolic
precursors that it no longer requires for metabolism.
Some methods for the detection of mycotoxins in foods can be found in Chapter 11. For an extensive
review of these substances in fruits, fruit juices, and dried fruits, see reference 27.
AFLATOXINS
Aflatoxins are clearly the most widely studied of all mycotoxins. Knowledge of their existence dates
from 1960, when more than 100,000 turkey poults died in England after eating peanut meal imported
from Africa and South America. From the poisonous feed were isolated Aspergillus flavus, and a
toxin produced by this organism that was designated aflatoxin (Aspergillus flavus toxin—A-fla-toxin).
Studies on the nature of the toxic substances revealed the following four components:
709