Cinnamaldehyde, biosynthesis

The earliest references to cinnamic acid, cinnamaldehyde, and cinnamyl alcohol are associated with thek isolation and identification as odor-producing constituents in a variety of botanical extracts. It is now generally accepted that the aromatic amino acid L-phenylalanine [63-91-2] a primary end product of the Shikimic Acid Pathway, is the precursor for the biosynthesis of these phenylpropanoids in higher plants (1,2). 

The reductive sequence from an appropriate cinnamic acid to the corresponding cinnamyl alcohol is not restricted to lignin and lignan biosynthesis, and is utilized for the production of various phenylpropene derivatives. Thus cinnamaldehyde (Figure 4.23) is the principal component in the... 

The activity of cinnamyl alcohol dehydrogenase (CAD EC 1.1.1.195) was already described in the 1970s and was mainly investigated with respect to lignin biosynthesis (see Petersen et al, 1999, for further information). It catalyses the reduction of cinnamaldehydes to cinnamyl alcohols with the help of NADPH the reaction is readily reversible (Fig. 4.7). From a functional point of view, CAD activity is involved in developmental lignification and in the formation of defence compounds. Several reviews have treated the involvement of this enzyme in lignin monomer formation (Boudet et al, 1998,... 

The first step of phenylpropanoid biosynthesis is conversion of phenylalanine into cinnamic acid by cleavage of ammonium group by the enzyme phenylalanine ammonia-lyase (PAL). Reduction of carboxylic acid from the cinnamic acid leads to cinnamaldehyde, which is then acylated with acetate from acetyl-CoA to form coniferyl alcohol [14]. Reductive cleavage of coniferyl alcohol by eugenol synthase yields eugenol [15]. 

Biosynthesis of cinnamaldehyde (VIII) and also phenylalanine (compare biosynthesis of other of eugenol (I) an safrole (VI) originates from plant phenols in 18.1.2.5.1). The following... 

A quantitative conversion of benzaldehyde to phenylacetyl carbinol was never achieved. A number of compounds were reported to be produced as byproducts during phenylacetyl carbinol biosynthesis by 5. cerevisiae. Voete et al. [47] observed the presence of acetyl benzoyl and rranr-cinnamaldehyde in the biotransformation mixtures. Smith and Hendlin [51] reported that benzoic acid is also produced during this biotransformation. Besides, production of the phenylacetyl carbinol isomer, 2-hydroxy-l,l-phenylpropane, was detected as a further byproduct of the reaction [77]. All of these b3q>roducts are produced in low amounts, which do not significantly influence efficiency of the production of the main biotransformation product, phenylacetyl carbinol. The only byproduct whose formation significantly influences the efficiency of phenylacetyl carbinol production is benzyl alcohol. 

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