Trichothecenes toxicity

However, the most interesting of the Baccharis species is most certainly B. coridifolia. This plant is well-known in Brazil as being one of that country s most toxic plants (49) and is a serious hazard to livestock who graze in pastures populated by B. coridifolia (49). Four separate collections were made of B. coridifolia (48). Three of these collections were "From several miles outside Curitaba and a fourth collection in a pasture near Santa Maria, the site of an earlier collection of 13. coridifolia (47), and several hundred miles away from Curitaba. ThTs latter collection and two of the three former collections contained appreciable quantities of roridins A and E. A third collection from near Curitaba appeared to contain no macrocyclic trichothecenes. From a 20 g sample of one of the collections of B. coridifolia... 

Soil microorganisms produce many compounds that are potentially toxic to higher plants. Examples include members of the following antibiotics (1-6), fatty and phenolic acids (7-12), amino compounds (13-15), and trichothecenes (16, 17). "Soil sickness" and "replant problems" have been reported where certain crops or their residues interfere with establishment of a subsequent crop (18, 19). Toxins resulting from microbial activity sometimes are involved, but it is often unclear whether these are synthesized de novo in microbial metabolism or are breakdown products of the litter itself (20). 

Of four basic trichothecene groups (A, B, C and D), types A and B represent the most important mycotoxins. Type A includes the T-2 toxin that can suppress the immune system and can cause damage to bone marrow. The T-2 toxin is about 14 times more toxic than the most widespread Fusarium-based type B mycotoxin, deoxynivalenol (DON), previously called vomitoxin. DON is a... 

Ex vivo studies have revealed that trichothecenes can both inhibit and stimulate leukocyte function.12 For example, trichothecenes are toxic to alveolar macrophages,13 but drive differentiation of human myeloid leukemic cells.14 Dose-dependent decreases or increases in B- and T-cell mitogen responses are observable in lymphocytes from animals exposed to T-2 toxin, DON, or various macrocyclic trichothecenes these toxins similarly impair or enhance mitogen-induced lymphocyte proliferation in vitro.12 Rank order of inhibitor potency in rodent and human lymphocyte proliferation assays is Type D > Type A group > Type B group and is dependent on degree of acylation as well as of uptake and metabolism. 

Zhou, H. R. et al. Amplified proinflammatory cytokine expression and toxicity in mice coexposed to lipopolysaccharide and the trichothecene vomitoxin (deoxynivalenol). J. Toxicol. Environ. Health 57, 115, 1999. 

Some microorganisms are also able to transform trichothecenes into less toxic compounds. For example, rumenal bacteria, bacteria from the large intestine of chickens, and bacterial populations from soil samples, were capable of transforming deoxynivalenol into 3-acetyldeoxynivalenol or 3-keto-4-deoxynivalenol (Binder et ah, 2000 Swanson et ah, 1987 He et ah, 1993 Shima et ah, 1997). Therefore, it seems likely that the development of wheat crops with the capability of eliminating this mycotoxin or bio-treatments could possibly be developed as a feasible strategy. 

Some natural products, or their degradation products, represent a hazard for mammals not because of general toxicity but for subtle, adverse properties, such as carcinogenicity and tumor promotion. They are best known fi om marine dinoflagellates (okadaic acid and structural analogues), filamentous fungi (trichothecenes and ochratoxins), and plants (pyrrolizidine alkaloids). 

Contamination occurs primarily in wheat, barley, rye, and maize. Type A trichothecenes include mainly T-2 toxin, HT-2, and diacetoxyscirpenol (DAS) mycotoxins of the group B include mainly 4-deoxynivalenol (DON), commonly known as vomitoxin, and nivalenol (NIV). Toxic effects include nausea, vomiting, visual disorder, vertigo, throat irritation, and feed refusal in farm animals. The most toxic is T-2, followed by DAS and NIV, with DON being the least toxic in acute toxicity studies but the most widespread in grains worldwide and therefore the most studied. Issues related to chemical and physical data, occurrence, toxicity, absorption, distribution, and metabolism of trichothecenes are reviewed in WHO (89) and IARC (34). Physicochemical data for some selected Fusarium toxins is given by Sydenham et al. (90). The molecular structures of the main trichothecenes are shown in Fig. 9. 

Many trichothecene derivatives have been tested as potential anticancer agents but have proved too toxic for clinical use. 

Trichothecenes are composed of 40 or more structurally related compounds produced by a variety of molds, including Cephalosporium, Fusarium, Myrothecium, and Trichoderma, which grow predominantly on grains. Much of the available information on human toxicity of trichothecenes was obtained from an outbreak of poisoning in Siberia in 1944, mentioned above. 

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