Lignins aromatic monomers from

AROMATIC MONOMERS FROM LIGNIN AND MODEL POLYMERS... 

In the purest sense, lignin is a complex racemic consisting from aromatic heteropolymers produced by free radical coupling reactions initiated by enzymatic dehydrogenation of the three primary precursors, the hydroxycinnamyl alcohol monomers differing in their degree of methoxylation trans-4-coumaryl alcohol [3-(4-hydroxyphenyl)-2-propenol)], trans-coniferyl alcohol [3-(4-hydroxy-3-methoxyphenyl)-2-propenol)] and trans-sinapyl alcohols [3-(4-hydroxy-3,5-dime-thoxyphenyl)-2-propenol)] (Fig. 8.4). 

The suberin polymeric structure cannot be defined in terms of a monomer repeating unit, since the spatial arrangement of these moieties cannot be accurately defined, even when their relative abundance is known. Additionally, the latter aspect depends on the depolymerization methods used to isolate the aliphatic fraction and, moreover, as far as the aromatic domain is concerned, its identification/quantification is also quite complex because of its macromolecular nature and structural similarity with lignin [1, 42-45]. Notwithstanding these difficulties, several models have been proposed to illustrate the suberin macromolecular structure in suberized cell walls [46, 47]. In 2002, Bernards proposed a model for suberin from potato periderm, which summarized the state of the art on the structural data related to this macromolecular component [1]. 

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