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Lignin biosynthesis is initiated by an enzyme-catalyzed phenol dehydrogenation of mixtures of p-hydroxy-iranscinnamyl alcohol monomers, namely coniferyl (2a), sinapyl (2b), and p-coumaryl (2c) alcohols. A copolymerization follows during which resonance-stabilized phenoxy radicals produced from monomers and from the growing polymer couple in a variety of ways to build up the lignin macromolecule (Sarkanen, 1971; Harkin, 1967, 1973; Adler, 1977).

Lignin-like dehydrogenation polymers (DHPs) can be made in vitro, using mushroom lacease or horseradish peroxidase preparations (Freudenberg, 1956, 1968; Higuchi, 1971; Brunow and Wallin, 1981). Although synthetic de-hydrogenative polymerization is a simplification of the lignification processes, it constitutes a unique tool to elucidate the lignin structural patternsand to study the possible chemical pathways followed during lignin bio-genesis (Ralph et al …