Trichothecenes classification

Epoxytrichothec-9-en-8-ones (Table 2) are often referred to as Type B trichothecenes [Group III on the chemical classification (2), based on ring A chemistry] the remaining simple trichothecenes, without a keto group at C-8, are Type A (Groups I and II of the chemical classification). 

All trichothecenes include the tricyclic 12,13-epoxytrichothec-9-ene core, 370. Based on this structure and its substitution pattern, the mycotoxins have been classified into four types, A (371), B (372), C (373), and D (374), by Ueno et al. Type A (371) can have a hydroxy group, an ester, or no functional group at C-8. Type B (372) possesses a carbonyl group at C-8, type C (373) has an epoxide function at C-7/C-8, and type D (374) mycotoxins are macrocyclic trichothecenes. Included among these four types there are some exceptions, which cannot be grouped accurately using this classification. Other classification systems for trichothecenes were proposed by Jarvis et al. (312) and Tamm et al. (313), but these will not be further discussed in this volume (Fig. 8.3). 

Fig. 8.3 Classification of trichothecenes into four types, A, B, C, and D, by Ueno et al.

Although this classification system has been largely used, there are other structural features that are not accounted for with this system. For example, all Fusarium trichothecenes, including lype A and Type B, have a hydroxyl or an acetyl group at C-3. Trichothecenes produced by Trichoderma, Trichothecium, Myrothecium, or Stachybotrys, including lypes A, B, C, and D, lack an oxygen function at the C-3 position. 

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