Trichothecene

Trichothecenes are a very large family of chemically related mycotoxins produced by various species of Fusarium, Myrothecium, Trichoderma, Trichothecium, Cephalosporium, Verticimonosporium, and Stachybotrys. Trichothecenes belong to sesquiterpene compounds.The most important structural features causing the biological activities of trichothecenes are: the 12,13-epoxy ring, the presence of hydroxyl or acetyl groups at appropriate positions on the trichothecene nucleus and the structure and position of the side-chain. They are produced on many different grains like wheat, oats or maize by various Fusarium species such as F. graminearum, F. sporotrichioides, F. poae and F. equiseti. Trichothecenes are a very large family of chemically related mycotoxins produced by various species of Fusarium, Myrothecium, Trichoderma, Trichothecium, Cephalosporium, Verticimonosporium, and Stachybotrys. Trichothecenes belong to sesquiterpene compounds.The most important structural features causing the biological activities of trichothecenes are: the 12,13-epoxy ring, the presence of hydroxyl or acetyl groups at appropriate positions on the trichothecene nucleus and the structure and position of the side-chain. They are produced on many different grains like wheat, oats or maize by various Fusarium species such as F. graminearum, F. sporotrichioides, F. poae and F. equiseti. Some molds that produce trichothecene mycotoxins, such as Stachybotrys chartarum, can grow in damp indoor environments. It has been found that macrocyclic trichothecenes produced by Stachybotrys chartarum can become airborne and thus contribute to health problems among building occupants.The poisonous mushroom in Japan and China, Podostroma cornu-damae contains six trichothecenes; satratoxin H, roridin E, verrucarin and others. Trichothecenes are a group of over 150 chemically related mycotoxins. Each trichothecene displays a core structure consisting of a single oxygen containing six membered ring, 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 trichothecene ability to inhibit protein synthesis and incur general cytotoxic effects. Notably, this core structure is amphipathic, containing both polar and non polar parts. All trichothecenes are related through this common structure, but each trichothecene 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 tricothecene and also serve as the basis for the most commonly used classification system for this family of toxins. This classification system breaks up the trichothecene family into four groups: Type A, B, C, and D. Type A tricothecenes 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 tricothecenes 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 trichothecenes 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 trichothecenes 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 trichothecene unique chemical properties, their classification type does not explicitly indicate their relative toxicity. While Type D trichothecenes are thought to be the most toxic, Types A and B have relatively mixed toxicity. The classification system described above is the most commonly used to group molecules of the trichothecene family. However, a variety of alternative classification systems also exist for these complex molecules. Trichothecenes can also be generally described as simple or macrocyclic. Simple trichothecenes include Types A, B, and C, whereas macrocyclic tricothecenes include Type D and are characterized by the presence of a carbon 4 - carbon 15 bridge. Additionally, J. F. Grove proposed a classification of tricothecenes into three groups that was also based upon the functional substitution patterns of the ring skeleton. Group 1 tricothecenes only have functional groups substituted on the third, fully saturated carbon ring. Group 2 tricothecenes contain additional functional groups on the core ring containing the 9, 10 carbon double bond. Finally, Group 3 trichothecenes contain a ketone functional group at carbon 8; this is the same criteria for Type B trichothecenes.