ABSTRACT
Lignin is a structural component of the cell walls of vascular plants (Sarkanen & Ludwig 1971), and the second most abundant naturally produced polymer in the biosphere (after cellulose). Lignin links through covalent bonds to noncellulosic wall polysaccharides, especially “hemicelluloses” (Isherwood 1965, Kirk & Farrell 1987, Stafford 1988). Various acids, including p-coumaric, ferulic, and diferulic acid, are linking to lignins through ester or ether bonds. Such bifunctional compounds, capable of forming both of ester and ether linkages, act as bridging units between lignin and “hemicelluloses” (Tanner & Morrison 1983, Scalbert et al. 1985, Bolwell 1988, Hartley et al. 1988). Lignins also link through covalent bonds to some proteins of cell walls (Whitmore 1982) too. Therefore, lignin essentially contains carbohydrate moiety in its structure. However, the role of the polysaccharide moiety in chemistry of lignin is unclear.
