Monolignols p-coumaryl

Lignin is a phenolic compound, created by the enzymatic polymerization of three phenolic alcohols, known as monolignols (p-coumaryl, coniferyl, and sinapyl alcohols). The structures of three phenolic alcohols are as follows ... 

Figure 9.43 Structure of monolignol where R[ = R2 = H p-coumaryl R[ = H, R2 = OCH3 confiferyl alcohol Rj = R2 = OCH3 sinapyl alcohol. (From de Leeuw and Largeau, 1993.)...

The main monolignols are coniferyl, sinapyl, and p-coumaryl alcohols. Cinnamic aldehydes and acids that are biogenetic precursors to the monolignol can also take part in the biosynthesis. This chapter is concerned with the topological aspects of the structnral organisation of lignin. 

Lignin precursors p-coumaryl (p-CA), coniferyl (CA) and sinapyl (SA) alcohols, are synthesized through the shikimate and cinamic acid pathways, starting from phenylalanine which under the action of phenylalanine ammonia-lyase (PAL) is deaminated followed by hydroxylations of the aromatic ring, methyla-tions and reductions of therminal acidic group to an alcohol leading to the formation of the monolignols (Fig. 8.2), [37, 48]. 

FIGURE 7.2 Monolignols (a) p-coumaryl alcohol, (b) coniferyl alcohol, and (c) sinapyl alcohol. 

Lignin is the second most abundant renewable biopolymer in the world, exceeded in quantity only by cellulose, comprising 30% of all non-fossil organic carbon [1] and constituting from a quarter to a third of the dry mass of wood. Its precursors are three monolignol monomers, methoxylated to various degrees by enzymatic reaction via a free radical route p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol [2],... 

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