Structural characterization and evaluation of the antioxidant activity of DES-Lignin isolated from Cunninghamia lanceolata

As a simple and effective biorefinery method, deep eutectic solvent (DESs) treatment was proposed to isolate lignin from lignocellulose. In this study, choline chloride/lactic acid (ChCl/Lac) was applied to extract high-purity and antioxidative lignin. Under the optimized conditions (120 degrees C for 12 h), the lignin profiling indicated that the recovered lignin had a high purity (94.18%), low molecular weight (Mw 1967 g/mol), and excellent thermal stability as compared with milled wood lignin. The lignin samples were characterized by using Fourier transform infrared spectrometry and nuclear magnetic resonance (NMR) spectra. In addition, the NMR spectra indicated the functional groups of the lignin extracted via DESs were less damaged and the backbone structure was not significantly modified. To further determine the potential application of DES-Lignin, the antioxidant activity was evaluated by radical scavenging ability. The IC50 values of a treatment time of about 12 h was 0.174. As expected, DES-Lignin showed obvious advantage in oxidation resistance. In short, the proposed process was considered as a promising biorefinery strategy for lignin first production.