Bread alkaloids

It is difficult to conceive that even poisons can be harnessed as medically-useful drugs, yet this is the case with the ergot alkaloids. These mycotoxins (i.e., toxins produced by molds) were responsible for fatal poisoning of humans and animals (ergotism) throughout the ages after consumption of bread made from grain contaminated with species of... 

A number of plants should be avoided because the seriousness of potential adverse reactions outweighs any potential benehts. All members of the Boraginaceae and several members of the Fabaceae and Asteraceae have been found to contain pyrro-lizidine alkaloids (PAs). Mass intoxications affecting up to 6000 people have been caused by bread cereals contaminated by the seeds of various species of Heliotropium and Crotalaria (Dubrovinskii, 1946 Khanin, 1948 Tandon et al., 1976a,b, 1977, 1978a,b Krishnamachari et al., 1977). 

Importance Pro is able to participate in a-helices to a much lower extent than other amino acids. It is thus a helix breaker of particular importance for the structure of proteins. Rotation about the amino peptide bond of proline is especially hindered the correct folding of Pro-containing proteins thus appears to be catalyzed by peptidylprolyl cis-fra/u-isomerases (rotamases, EC 5.2.1.8 see FK-506). On account of its presence in gluten, Pro is involved in the Maillard reaction resulting in the typical bread flavor. The inner salt (betaine) of I, l-dimethyl-P. is a widely distributed pyrrolidine alkaloid in plants, e.g., in woundwort (Stachys spp., stachydrin). 

Scott, P.M. and Lawrence, G.A. (1982) Losses of ergot alkaloids duringmaking of bread and pancakes./. Agric. Food Chem., 30, 445-450. 

The Strecker degradation of ornithine proceeds analogously, but the intermediate 4-aminobutanal forms by cychsation the final product, 1-pyrroHne (Figure 2.59). This reaction is important for the development of the characteristic aroma of bread crust (see Section 8.2.12.4.1), the aroma of other cereal products, certain fragrant rice varieties (such as Basmati rice) and in the biosynthesis of pyrrolidine alkaloids in plants (see Section 10.3.2.1.1). It was proposed that pyrrolidine and l-pyrrohne also result upon Strecker-type reaction of proline by a-dicarbonyl compounds. 

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