Mycotoxin is a convenient generic term describing the toxic secondary metabolites produced by fungi. "Myco" means fungal (mold) and "toxin" represents poison. They encompass a considerable variety of low molecular weight compounds with diverse chemical structures and biological activities. Some mycotoxins could also be toxic to plants or other microorganisms; but these compounds are not classified as antibiotics of fungal origin. Like most microbial secondary metabolites, the benefit of mycotoxins for the fungi themselves is still not clearly defined. In considering the effects of mycotoxins on animals, it is important to distinguish between "mycotoxicosis" and "mycosis." Myco-toxicosis is used to describe the action of mycotoxin(s) and is frequently mediated through a number of organs, notably the liver, kidney, lungs, and the nervous, endocrine, and immune systems. On the other hand, "mycosis" refers to a generalized invasion of living tissue(s) by growing fungi (CAST 2003; Chu 1998). Due to their diverse chemical structures, mycotoxins may exhibit a number of biological effects, including both acute and chronic toxic effects as well as carcinogenic, mutagenic /genotoxic, teratogenic, and immunotoxic effects (Bhatnagar et al. 2002; Chu 1998; 2002; Wogan 1992). Modulation of the animal immunosystem, either immunosuppressive (most often) or immuno-stimulatory, also plays an important role for the overall toxic effects (Bondy and Pestka 2000). The interaction of mycotoxins with cellular macromolecules plays a dominant role in their toxic actions (Chu 2002; Hussein and Brasel 2001). Recent studies on the effect of mycotoxins on apoptosis have further revealed their mode of action at the cellular level (Chu 2002). The complexity of the biological effects of mycotoxins has led to a scientific discipline named "mycotoxicology" for the study of various issues that are encountered with this group of toxins.
Mycotoxins have been the subject of many reviews, and recently several comprehensive reviews have discussed various aspects of this topic (Bhatnagar et al. 2002; CAST 2003; Chu 2002; Scudmore 2000). Due to a limitation of space, in this chapter we have tried to cover, as much as possible, the most recent advances achieved in the field, and refered primarily to reviews listing all the previous landmark references in the field.
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