Ferulate–coniferyl alcohol cross-coupled products formed by radical coupling reactions |
| |
Authors: | Aiping Zhang Fachuang Lu Runcang Sun John Ralph |
| |
Institution: | (1) Department of Biochemistry (Enzyme Institute), and the Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, 1710 University Avenue, Madison, WI 53726, USA;(2) State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, 510641 Guangzhou, China |
| |
Abstract: | Radical coupling reactions between ethyl ferulate (Et-FA), a simple model for feruloyl polysaccharides in planta, and coniferyl
alcohol (CA), a monolignol, were studied in order to better understand the polymer cross-coupling interactions among polysaccharides
and monolignols or lignin, mediated by ferulate (FA), in plant cell walls. Cross-coupled FA/CA dimers produced in an aqueous
buffer (pH 5.0) containing peroxidase/hydrogen peroxide were isolated and characterized by NMR. The total coupling products
were characterized by 2D 13C–1H correlation (HSQC) NMR spectroscopy and GC–MS. Results from this study showed that ferulate readily cross-couples with coniferyl
alcohol through free radical coupling mechanisms producing a series of cross-coupled FA/CA dimers with β-O-4-, β-5-/8-5-,
and 8-β-linkages; the syntheses and isolation of β-5- and 8-5-cross-coupled dimers are reported here. The transformation from
8-β-coupled FA/CA hydroxyl esters into lactones through intramolecular transesterification is demonstrated for the first time
and mechanisms behind these transformations are discussed. The finding of both β-5- and 8-5-cross-coupled dimers in this study
suggests that analogs of both may be present in plant cell walls. Finally it is suggested that ferulates in plants indeed
react with monolignols through free radical mechanisms producing a more diverse array of cross-coupled dimers than previously
reported. |
| |
Keywords: | Coniferyl alcohol Cross-coupled dimer Cell walls Ethyl ferulate Grass lignin Radical coupling |
本文献已被 SpringerLink 等数据库收录! |
|