Structural Characterization of Lignin and Lignin-Carbohydrate Complex (LCC) from Ginkgo Shells ( L.) by Comprehensive NMR Spectroscopy.
Journal:
Polymers
Published Date:
Jul 4, 2018
Abstract
Lignin and lignin-carbohydrate complexes are important polymers for lignocellulosic biorefinery and functional materials, but those in ginkgo shells are not effectively analyzed and exploited. Based on this background, milled wood lignins (MWL and MWL) and lignin-carbohydrate complexes (LCC and LCC) were isolated from the shells of L. cv. Damaling (ML) and L. cv. Dafozhi (FZ) correspondingly, and were structurally characterized by comprehensive NMR spectroscopy. The results showed that ginkgo shells exhibited higher lignin (42%) and xylan (20%) content than general softwood species. Isolated MWLs were rich in guaiacyl units with the presence of ferulates and -coumarates, and the molecular formula was C₉HO(OCH₃) and C₉HO(OCH₃) for MWL and MWL, respectively. Phenolic hydroxyl of MWL (1.38 mmol/g) and MWL (1.23 mmol/g) in ginkgo shells was much less than that in general softwoods, suggesting a higher etherification and condensation degree of ginkgo shells lignin, and -5', -O-4', and 4-O-5' bonds were the main condensed structures. -acetylated -d-xylopyranoside and -d-mannopyranoside were the main polysaccharides associated with lignin, and the acetyl groups frequently acylate the C₂ and C₃ positions. LCC had more phenyl glycoside (0.035/Ar) and less -ester (0.026/Ar) linkages than LCC.
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