Radical transfer system in the enzymatic dehydrogenative polymerization (DHP formation) of coniferyl alcohol (CA) and three dilignols

Abstract No clear picture has yet been elaborated concerning the mechanism of lignin growth, and thus this topic is the focus of the present paper. Namely, the enzymatic dehydrogenative polymerization (DHP formation) of coniferyl alcohol (CA, as a monolignol) and three dilignols and their reaction kinetics were investigated. The dilignols [guaiacylglycerol-β-coniferyl ether ( I βO4 ), dehydrodiconiferyl alcohol ( II β5 ), and pinoresinol ( III ββ )] and CA as a monolignol [(3-OCD 3 )-coniferyl alcohol ( CA OCD3 )] were synthesized and subjected to enzymatic DHP formation. The dilignol derived from CA OCD3 could be identified by its higher molecular weight in comparison with the starting dilignols ( I βO4 , II β5 , and III ββ ). Based on the observed consumption rate of the CA and its dilignols, it was proposed that a radical transfer system exists between the dilignols, which is generated from the CA and the starting substrates.