Model coniferyl alcohol lignin (the so-called dehydrogenative polymerisate, DHP) was produced in water under homogeneous conditions guaranteed by the presence of a micellised cationic surfactant. A complete study of the activity of the enzymatic system peroxidase/H2O2 under our reaction conditions was reported and all the reaction products up to the pentamer were characterised by 1H NMR spectroscopy and ESI mass spectrometry. Our system, and the molecules that have been generated in it, represent a closer mimicry of the natural microenvironment since an enzyme, under micellar conditions, reproduces the cell system better than in buffer alone. On the basis of the oligomers structures a new biosynthetic perspective was proposed that focused attention on a coniferyl alcohol dimeric quinone methide as the key intermediate of the reaction. A formal, strictly alternate sequence of a radical and an ionic step underlines the reaction, thus generating ordered oligolignols structures. Alternatively to other model lignins, our olignols present a lower degree of radical coupling between oligomeric units. This offers a closer biosynthetic situation to the observation of a low rate of radical generation in the cell wall.

Lignin chemistry: biosynthetic study and structural characterization of coniferyl alcohol oligomers formed in vitro in a micellar environment

DE ANGELIS, Francesco;REALE S;SPRETI, Nicoletta
2010

Abstract

Model coniferyl alcohol lignin (the so-called dehydrogenative polymerisate, DHP) was produced in water under homogeneous conditions guaranteed by the presence of a micellised cationic surfactant. A complete study of the activity of the enzymatic system peroxidase/H2O2 under our reaction conditions was reported and all the reaction products up to the pentamer were characterised by 1H NMR spectroscopy and ESI mass spectrometry. Our system, and the molecules that have been generated in it, represent a closer mimicry of the natural microenvironment since an enzyme, under micellar conditions, reproduces the cell system better than in buffer alone. On the basis of the oligomers structures a new biosynthetic perspective was proposed that focused attention on a coniferyl alcohol dimeric quinone methide as the key intermediate of the reaction. A formal, strictly alternate sequence of a radical and an ionic step underlines the reaction, thus generating ordered oligolignols structures. Alternatively to other model lignins, our olignols present a lower degree of radical coupling between oligomeric units. This offers a closer biosynthetic situation to the observation of a low rate of radical generation in the cell wall.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11697/13284
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