Masked Mycotoxins

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Who Is That Masked Toxin

Masked mycotoxins are plant metabolites of the parent mycotoxins. Studies have brought up this potential threat to consumer safety from masked forms of mycotoxins, and the possible release of their toxic parents during human and animal digestion. For a very thorough review of masked mycotoxins, I refer you to a wonderful article in Molecular Nutrition And Food Research or read the condensed version below.


 Mycotoxins are secondary metabolites of molds (a fungi) toxic to animals and humans. Toxigenic fungi often grow on edible plants, thus contaminating food and feed. The most important molds producing mycotoxins that are found in food products are Aspergillus, Fusarium, Alternaria and Penicillium.

Plants, as living organisms, can alter the chemical structure of mycotoxins as part of their defense against xenobiotics (foreign substances). The extractable conjugated or non-extractable bound mycotoxins formed by the plant, remain present in the plant tissue, but are currently neither routinely screened for in food nor regulated by legislation, thus they may be considered hidden, or masked.

Mycotoxins  made by Fusarium such as (deoxynivalenol, zearalenone, fumonisins, nivalenol, fusarenon-X, T-2 toxin, HT-2 toxin, fusaric acid) are prone to metabolism or binding by plants, but transformation of other mycotoxins by plants (ochratoxin A, patulin, destruxins) has also been described. Toxicological data are scarce, but several studies highlight the potential threat to consumer safety from these substances. For example, the possible hydrolysis (breaking down with water) of masked mycotoxins back to their toxic parents during human or animal digestion.

Mycotoxins Are A Serious Threat In Food

The threat of mycotoxins in our food may be as serious as the pesticides and herbicides in our food. At least the pesticides and herbicides have some semblance of control around their entrance into the food chain, and we have the choices of purchasing organic food. However, with mycotoxins there is rarely any toxicological assessment of them in the food. We rely on good growing, and storage processes of the farmer, as well as good manufacturing practices of the processor and packager.

Creation Of The Masked Mycotoxins

Chemical transformations that generate hidden, or masked mycotoxins are catalyzed by plant enzymes, most commonly by enzymes involved in the plant's detoxification processes. They may or may not be detectable by analytical techniques since they have been altered by the plant.

Masked Mycotoxins During Food Processing

People also alter mycotoxins during food processing. This alteration is generally thought to make mycotoxins less toxic. However fermentation processes may alter them into chemicals we are not testing for and we do not know exist. Ferments used in making wine, beer, sausages or other foods may contain unknown mycotoxins. That wine that seemed to make you sick might have unknown mycotoxins. It might not be the sulfites. Most people who ferment veggies or other food or drink have had a ferment go bad on them. We use our nose and our taste buds to decide if it is good or not. As a general rule this seems to protect us. However, could there be an occasional non noticed masked mycotoxin in a wine we make that is the real cause of someone drinking a small amt of wine and feeling horrible the next day?

Testing For Mycotoxins

Science has created tests that find only certain mycotoxin configurations in food. When that configuration is changed due to the plant altering it during the plants detox process, or alteration during processing of the food, it may have actually become a less, or more potent toxin, however, our tests will not even notice it since we have no tests for detecting that particular chemical configuration. In fact, we (us humans) have not studied the various possible mycotoxin/masked mycotoxin forms available in food.

Confusion Around Testing And Toxicity

Modifications of mycotoxin molecules that reduce, or eliminate toxicity may lead to apparent overestimation of mycotoxin contamination. This happens when the analytical method detects the modified mycotoxin along with the unmodified molecule, but does not reveal that the analytical signal originated from a less toxic, or non-toxic derivative. This is particularly relevant for methods based on antigen–antibody binding because epitopes recognized by antibodies, and toxicity determinants destroyed by the modification are not necessarily identical.


Transformations Generating Masked Mycotoxins May Lead To A Decreased Toxicity

When the scientists detect non-toxic forms of mycotoxins in food products they may still call them masked mycotoxins. Bound mycotoxins (bound to binders) may be regarded as detoxified as long as they cannot be released from the matrix during food processing, or in the digestive system. Classification of mycotoxin transformations as masking, or detoxification is therefore only possible when the fate of the substances during food processing and digestion is understood. Toxicity assessment for all mycotoxin derivatives that occur in food is important for the estimation of the health risk posed by the sum of different forms of a given mycotoxin.


Monitoring of zearalenone (ZEN) in animal feeds illustrates this problem. The risk of hyperestrogenic effects is underestimated because α-zearalenol (α-ZEL), which is a more estrogenic derivative of ZEN, is neither determined nor regulated.

Looking At Glutathione Conjugation In Plants And The Use Of Herbicide Safeners

It is thought that glutathione (GSH) conjugation is irreversibile. Degradation of GSH conjugates is possible but the products are different from the original xenobiotic. The only potential exception is addition of GSH to a double bond next to an electron withdrawing group. Conjugations of glutathione with epoxides, lactones or aldehyde groups, which are more relevant for mycotoxins, are likely to be irreversible. This situation is very different from the conjugation of mycotoxins to glucose, which can be reversed by numerous glycosidases present in plants and/or in the digestive system of animals. While most conjugates generated by glutathione-S-transferases (GSTs) in plants contain GSH, some members of the plant GST super family accept GSH derivatives, generating conjugates with homoglutathione and hydroxymethylglutathione. The activity of GSTs is induced by stress, such as by heavy metals, which is how herbicide safeners (chemicals to protect crops from herbicides) induce GST activity in crops to protect them from the herbicide applications (often applied to the seed as a coating). It can therefore be assumed that the level of mycotoxins masked by GSH conjugation in plants varies to a large degree, and that herbicide safener treatments stimulate the conversion of mycotoxins to masked forms.

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