Suberized plant cell walls have three distinguishing features: (1) tissue specificity, (2) a poly(aliphatic) domain and (3) a unique, “lignin-like” poly(phenolic) domain.
With respect to the latter, comparisons have often been made to lignin, but the unique phenolic composition of suberized cells yields a unique polymer better designated as a poly(phenolic) domain that ferulic acid part Compounds Phenolic.
Ferulic acid (3-methoxy-4-hydroxycinnamic acid) is the main phenolic acid in cell walls of seeds and leaves of monocotyledons, in particular graminacae, both free and ester-linked at the O5 position to α-L-arabinosyl residues of AX and conjugated to polysaccharides, glycoproteins, polyamines and fatty acids, thus acting as cross-linker (Yamamoto et al., 1989; Negrel et al., 1996).
The determination of the total amount of ferulic acid should consider both the free and the conjugated ones, however experimental conditions play a crucial role, therefore quantification and comparisons should be cautious and thoroughly explained in the methods.
More about ferulic acid and suberin:
Its presence has been reported among the products of suberin depolymerisation in amounts varying between 1.3-1.5% (Graça and Pereira, 1997; Lopes et al., 2000) and 5–8% of the soluble monomers (Bento et al., 1998, 2001a,b; Conde et al., 1999).
In the products obtained with a mild suberin methanolysis, dimeric structures between ferulic acid and the ω-hydroxyacids were found including the feruloyl esters of the 22-hydroxydocosanoic acid and of the 18C monounsaturated ω-hydroxyacid in higher amounts (Graça and Pereira, 1998).
Further dimers between ferulic acids and alkanols, ω-hydroxyacids and glycerol were found in the suberin of potato periderm and Pseudotsuga bark (Graça and Pereira, 1999, 2000b).