MYCOTOXINS

Mycotoxins are exotoxins produced by fungi. The area of microbiology that studies fungi and the toxins they produce (i.e. mycotoxins) is known as mycotoxicology. The disease condition provoked by the intake of mycotoxins in human or animal hosts is generally known as mycotoxicoses.

Mycotoxins are pharmacologically active secondary metabolites produced by toxin-producing fungi in food, and which has the potential to stimulate lethal reactions in humans or animals that consume such toxin-infested food. When taken in large doses and allowed to accumulate in the body system, mycotoxins can elicit several acute and chronic intoxifications and other physiological reactions in human hosts.

Mycotoxins are mainly secreted by some specific fungal species especially moulds and some mushrooms such as Aspergillus species, Penicillium species, Fusarium species, Claviceps species and Acremonium coenophialum (Table 1). Apart from secreting potent harmful toxins, most Aspergillus species especially A. niger are common contaminants found in the microbiology; and they are notorious in colonizing culture media plates that are not properly stored (Figure 1). Mushrooms (e.g. Amanita species) produce a variety of mycotoxins; and the disease condition they cause is known as mycetismus.

The main route of entry of mycotoxins into the body is via the ingestion of mycotoxin-contaminated foods. Most fungal mycotoxins are produced in dried food products such as nuts, cereals, maize and other grains and food products. Other groups of food especially fruits (e.g. oranges, apple, mangoes) as well as vegetables are not left out as they could be contaminated by fungal toxins.

Mycotoxins are heat-stable or resistant to heating, and thus most food preparation techniques such as boiling may have little or no effect on their in vivo effectiveness. Thus, it is critical to avoid fungal infestation of food products instead of exposing them to conditions that encourage the growth of moulds in them, a factor that stimulate the production of mycotoxins. Utmost care is required in the processing and preparation of food meant for human consumption because of the ubiquity of fungal spores in the natural environment.

They are produced during the normal metabolic activities of fungi. High humidity and moist environment as well as high temperature are some of the factors that encourage the growth of moulds in food products. Fungi easily contaminate food products especially crop plants because fungi are ubiquitous in the soil.

Table 1. Synopsis of mycotoxins produced by fungi

Organism	Mycotoxin produced	Effect
Aspergillus flavus	Aflatoxins	Mutagenic, teratogenic, immunosuppressive and carcinogenic activity
Penicillium species	Ochatoxin A and patulin	Carcinogenic and protein synthesis inhibitor. Patulin promotes apoptosis
Fusarium species	Fumonisins, deoxynivalenol, zearalenone	Promotes cellular damage and oxidative stress. Carcinogenic activity
Claviceps species	deoxynivalenol, zearalenone	Carcinogenic activity
Acremonium coenophialum	Ergopeptine alkaloids	Causes abortion, gangrene, convulsion, and suppression of lactation in animals such as sheep and cattle
Amanita phalloides	Amatoxins	Toxic lethal peptides that causes severe vomiting and diarrhea. Degenerative changes occur in the kidney and liver; and death may occur few days after intoxifications.
Amanita verna	Amatoxins	Same as above

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