Comparison of Lignin-Like Polymers Produced Peroxidatively by Cinnamic Acid Derivatives in Leaf Sections of Phleum

Abstract

A series of cinnamic acid derivatives and related compounds postulated as lignin precursors were incubated with sections of the lamina of Phleum pratense (timothy grass) in the presence of H2O2 at pH 4.5. Cinnamic acid and tyrosine were inactive, while p-hydroxy-cinnamic, ferulic, and sinapic acids, and coniferyl alcohol produced lignin-like polymers, presumably by peroxidative polymerization. The actual products, however, differed in their reaction to histochemical tests for lignin, in their solubility in water and in 0.5 N NaOH, in the free phenolic groups detected by the qulnonechlorimide test, and in their ionization difference spectra. When compared with the lignin extracted from mature timothy shoots or hay, ferulic acid produced the most natural product. Although these results support the general scheme implicating these compounds as immediate precursors of the 3 different moieties found in grass lignins, the variations in the polymers formed may reflect basic differences in the solubility and polymerization of lignins from woody plants and from herbaceous grasses.