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Title
Structural characterization of isolated lignins from Caragana korshinskii Kom
Authors
K. WANG H.Y. YANG X. YAO R.C. SUN and G.L. JONES
Received
November 21, 2011
Published
Volume 46, Issue 3-4 March-April
Keywords
Caragana korshinskii Kom., lignin, fractionation, structural characterization
Abstract
Lignin fractions, isolated from Caragana korshinskii Kom., were subjected to extensive structural characterization, including chemical component analysis, gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), ultraviolet (UV), thermo gravimetric/differential thermal analysis (TGA/DTA), and nuclear magnetic resonance (NMR). The structural differences caused by different solvent treatments (water, ethanol and NaOH alkaline solution in concentrations of 1%, 3%, 5%, 8% and 10%) were studied comparatively. The results indicated that 84.1% lignin was fractionated with the successive treatments. The weight-average molecular weights of all lignin fractions ranged from 926 to 2686 g/mol. Noticeable amounts of esterified hydroxycinnamic acids were identified in the lignin fractions obtained from water and ethanol treatments. The cleavage of ester and other types of lignin-carbohydrate interaction was obviously induced under basic conditions, and the purity of the isolated lignin was consequently improved. However, the thermal stability of the lignin fraction was slightly enhanced. Some substructures, such as ?-O-4, ?-?’, were also detected in C. korshinskii Kom. lignin by NMR technology.
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