General classification The core structure of all major<unk> s with major examples from each classification type. Identifying functional groups for the classification type are highlighted in red.<unk> s are a group of over 150 chemically related mycotoxins. Each<unk>  displays a core structure consisting of a single six-membered ring containing a single oxygen atom, flanked by two carbon rings. This core ring structure contains an epoxide, or tricyclic ether, at the 12,13 carbon positions, as well as a double bond at the 9, 10 carbon positions. These two functional groups are primarily responsible for<unk>  ability to inhibit protein synthesis and incur general cytotoxic effects. Notably, this core structure is amphipathic, containing both polar and non polar parts. All<unk> s are related through this common structure, but each<unk>  also has a unique substitution pattern of oxygen containing functional groups at possible sites on carbons 3,4,7,8, and 15. These functional groups govern the properties of an individual<unk>  and also serve as the basis for the most commonly used classification system for this family of toxins. This classification system breaks up the<unk>  family into four groups: Type A, B, C, and D. Type A<unk> s have hydroxyl, ester, or no functional group substitutions around the core ring structure. Common examples of these are Neosolaniol with a hydroxyl substitution at carbon 8, and T-2 toxin with an ester substitution at carbon 8. Type B<unk> s are classified by the presence of carbonyl functional groups substituted around the core ring structure. Common examples of these include nivalenol and trichotecin, which both have a ketone functional group at carbon 8. Type C<unk> s have an extra carbon 7, carbon 8 epoxide group. The common example of these is crotocin. which also has an ester functional group at carbon 4. Type D<unk> s have an additional ring between carbon 4 and carbon 15. These rings can have diverse additional functional groups. Common examples of these are roridin A and satratoxin H. Although the distinct functional groups of these classification types give each<unk>  unique chemical properties, their classification type does not explicitly indicate their relative toxicity. While Type D<unk> s are thought to be the most toxic, Types A and B have relatively mixed toxicity. Alternative classifications The classification system described above is the most commonly used to group molecules of the<unk>  family. However, a variety of alternative classification systems also exist for these complex molecules.<unk> s can also be generally described as simple or macrocyclic. Simple<unk> s include Types A, B, and C, whereas macrocyclic<unk> s include Type D and are characterized by the presence of a carbon 4 - carbon 15 bridge. Additionally, J. F. Grove proposed a classification of<unk> s into three groups that was also based upon the functional substitution patterns of the ring skeleton. Group 1<unk> s only have functional groups substituted on the third, fully saturated carbon ring. Group 2<unk> s contain additional functional groups on the core ring containing the 9, 10 carbon double bond. Finally, Group 3<unk> s contain a ketone functional group at carbon 8; this is the same criteria for Type B<unk> s. Advances in the field of evolutionary genetics have also led to the proposal of<unk>  classification systems based on the pathway of their biosynthesis. Genes responsible for the biosynthesis of a mycotoxin are typically located in clusters; in Fusariumi these are known as TRI genes. TRI genes are each responsible for producing an enzyme that carries out a specific step in the biosynthesis of<unk> s. Mutations in these genes can lead to the production of variant<unk> s and therefore these molecules could be grouped on the basis of shared biosynthesis steps. For example, a shared step in the biosynthesis of<unk> s is controlled by the gene TRI4. This enzyme product controls the addition of either three or four oxygens to trichodiene to form either isotrichodiol or isotrichotriol respectively. A variety of<unk> s can then be synthesized from either of these intermediates and they could therefore be classified as either t-type if synthesized from isotrichotriol or d-type if synthesized from isotrichodiol.
Trichothecene
Scyllatoxin
Laudanum
Toxicon
Simmondsin
Coal tar
Mersa
Chloracne