Cold alkali can extract phenolic acids that are ether linked to cell wall components in dicotyledonous plants (buckwheat, soybean and flax)

Experiments were carried out to estimate the amounts and nature of bonding of ferulic acid to cell walls of various dicotyledonous plant materials including soybean heterotrophic and mixotrophic cell suspension cultures, soybean leaves, buckwheat callus, flax phloem and xylem. Isolated cell walls were oxidized, with CuSO4-NaOH, with phenol aldehyde products and ferulic acid produced estimated by GC. Ferulic acid content was also analyzed in the cell wall fraction extracted by 1 M alkali at room temperature, which cleaves ester linkages, and in the fraction extracted by hot concentrated alkali, which cleaves ether linkages. Overall, the bulk of the cell wall ferulic acid (60-80%) was found to be ether linked to cell-wall components. Room temperature alkali treatment may release from the cell wall a portion of the ferulic acid that is esterified to cell wall components via saponification. This treatment, however, also extracts a portion of the etherified ferulic acid that is bound to some cell wall components like proteins or glycoproteins that are acid precipitable. Our results demonstrate that hydroxycinnamic acids can form a significant part (0.01-0.19% of cell wall dry weight) of primary cell wall phenolics of dicots and the nature of linkages between ferulic acid and polymers of the primary cell wall varies in different plant materials. (C) 1998 Elsevier Science Ltd. All rights reserved.