THE CHEMICAL DIVERSITY OF MYCOTOXINS

Mycotoxins are a group of more than 400 types of molecules that present more or less toxicity, produced by more than 100 species of fungi. Among them, the most common and with more effects on human and animal health are those belonging to the groups of aflatoxins, zearalenone, fumonisins and trichothecenes. Its molecular structure is very diverse, and its main effects can be largely explained by knowing its chemical structure. In this article, we are going to focus on the structure of mycotoxins on their toxicity mechanisms.

Aflatoxins are a group of mycotoxins whose structure is coumarins linked to a bifuran unit (B series of aflatoxins) or lactone (G series of mycotoxins). This structure causes them to bind DNA, RNA and proteins. For example, aflatoxin B1 binds to DNA with a covalent bond, which causes mutations, and this is the reason that makes it a very potent carcinogen.

Aflatoxin B1 (Chemspider)                                                                           Aflatoxin B1-Guanin adduct (Carvajal, 2013)

Zearalenone is an acid lactone, and its structure is similar to the one of estrogens, the most important female sex hormone. In fact, its estrogenic effect is due to the fact that it binds to the α y β receptors, competing with estrogens themselves (Alshanaq, 2017). Therefore, the main symptoms it produces are related to reproductive function.

Zearalenone (Chemspider)                                                                               Estradiol (Chemspider)

Fumonisins are a particular in terms of their chemical structure. Its structure is very similar to the one of sphingosines. In fact, it has been shown that it inhibits the metabolism of sphingolipids, and consequently, alters the methanolic pathways mediated by them, as well as the physiological functions dependent on them. 

           Fumonisin (Chemspider)                                                                   Esfingosin (Chemspider)                    

Trichotecenes, are the most diverse group of mycotoxins. Among them, the best known is Deoxynivalenol (usually called DON), which is a terpenoid. Its structure makes it a very non polar molecule, making it more difficult to adsorb than the rest of the mycotoxins. It contains an active epoxide group that binds the 60s subunit of ribosomes, affecting their function, and therefore, is a very powerful protein synthesis inhibitor (Janik, 2020). 

Deoxynivalenol (Chemspider)