Glucosinolates aromatic

Glucosinolates are divided into three classes based on the general chemical properties of the amino acid precursors. Aliphatic glucosinolates variously contain a straight carbon chain derived from methionine or a branched chain fix)m isoleucine, leucine or valine. Indole glucosinolates are formed from tryptophan, and the aromatic glucosinolates are derived from phenylalanine or tyrosine. ... 

The many naturally occurring glucosinolates fall into three groups, aliphatic, aromatic, and indole representative examples are given in Table 2. 

Mahadevan reviewed research up to 1973, with respect to the pathways of oxime metabolism in plants, and evaluated a series of aliphatic and aromatic oximes that are precursors for the biosynthesis of plant secondary metabolites (as opposed to basic metabolism products that are essential for cell survival), such as cyanogenic glycosides, glucosinolates and certain phytohormones . Some of these oximes are shown below. 

Arabidopsis cytochrome P450 (CYP83A1, CYP83B1) Conversion of aromatic and aUphatic oximes to glucosinolates 101... 

The precursor substrates and enzymes necessary for the first committed steps often appear to have been recruited from primary metabolic pathways, such as glycolysis, the Krebs cycle, the pentose phosphate pathway and the shikimate pathway [32], For example, the aromatic amino acid s L-phenylalanine and L-tyrosine, produced by the shikimate pathway, are precursors for a wide spectrum of natural products including phenylpropanoids, flavonoids, lignins, coumarins, cyanogenic glycosides, glucosinolates, and alkaloids [33],... 

In contrast to aliphatic glucosinolates, indolyl glucosinolates such as glucobrassidan and its myrosinase-catalyzed transformation products have been shown to inhibit chemical and other types of cardnogensis induced by polycyclic aromatic hydrocarbons and other iiutiators (17). Indolyl glucosinolates are found abundantly in crudferae vegetables and are present in relativdy large amounts in the canola varieties of rapeseed. 

Fig.1 The general structure of cyanogenic glucosides (a) and glucosinolates (b) structure. In (b), the R group is derived from amino acids and is highly variable. It may be aliphatic, aromatic or heterocyclic...

Aromatic and heterocyclic isothiocyanates are unstable and easily hydrolyse to the corresponding alcohols. For example, 4-hydroxybenzyl isothiocyanate (the degradation product of sinal-bin, which occurs in the seeds of white mustard, Leucosinapis album, Brassicaceae) decomposes in normal table mustard to 4-hydroxybenzyl alcohol and thiocyanate ions (Figure 8.68). Isothiocyanates derived from indolyl glucosinolates behave similarly. 

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