ABSTRACT
Among natural chemicals present in foods, toxins appear as one of the most harmful threats to human health. Some of these natural toxins are synthesized by plants as a means to protect themselves from insects or to create resistance to certain diseases, and thus may be present in fruits and vegetables. Other natural toxins are produced as a consequence of the damage to a plant or the growth of molds on it. Another kind of natural toxin is those produced by microalgae in the sea or in fresh water. In the former case, bivalves, due to their condition from ‘lter-feeding mollusks, are more likely to contain these toxins than ‘sh. In the latter case, cyanotoxins such as microcystins, which are hepatotoxins produced by cyanobacteria, can be present in water for agriculture, cattle breeding, or human consumption (Carmichael et al. 2001). Microbial toxins produced by microorganisms such as bacteria may also contaminate foodstuffs. Some examples are botulinum neurotoxin, the most potent toxin known, which induces botulism, a potentially fatal paralysis (Singh 2000); cholera toxin, which is responsible for the harmful effects of cholera infection; and enterotoxin, which causes the death of the cells of the intestinal wall.
