Rscn HSO4

Figure 11. Degradation of glucosinolate: (1) glucosinolate, (2) isothiocyanate, (3) thiocyanate. Source: Ref. 83.

at the level of approximately 10 mg/100 g fresh weight (83). These glycoalkaloids are strong inhibitors of Cholinesterase causing neurological disorder symptoms. Lethal doses for humans range from 3 to 6 mg/kg body weight, and doses of greater than 2 mg/kg are normally considered toxic.

Another class of toxicants, glucosinolates, occurs predominantly in vegetables such as cabbage, cauliflower, radish, mustard greens, brussels sprouts, and broccoli. Glucosinolates are hydrolyzed by the enzyme thioglucoside glycohydrolase when the plant tissues are crushed. The unstable aglycone produced is converted to isothiocyanate in a process similar to the Lossen rearrangement or thiocyanate (84) (Fig. 11). The latter compound is a goitrogen.

A number of amino acids, peptides, and proteins constitute an interesting class of toxicants. There are more than 250 nonprotein amino acids found in plants, many of which are structurally similar to the protein amino acids. For example, ß-pyrazol-1-ylalane, pipecolic acid, homo-arginie, a,/?-diaminobutyric acid are analogs of histidine, proline, arginine, and lysine, respectively. Toxicity of these nonprotein amino acids is usually caused by the competition with structurally similar protein amino acids for proteins, resulting in functionally inactive products, or in interference with protein synthesis.

The notorious toxins produced by Clostridium botulinum are neurotoxins that block the release of acetylcholine

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