In-depth interpretation of the structural changes of lignin and formation of diketones during acidic deep eutectic solvent pretreatment

Deep eutectic solvents (DESs) as novel and green solvents can extract high-purity lignin from lignocellulose in a high yield; however, further utilization of the extracted lignin in the DES is a severe challenge in biorefinery processes. Nevertheless, the potential of lignin valorization can be precisely reflected by unveiling the chemical transformations of lignin during DES pretreatment. In this study, we aimed to understand the possible transformation pathway via thorough characterization of the regenerated lignin and lignin oil and transformation of lignin into value-added products. During this process, alkali lignin (AL) isolated from poplar was pretreated with choline chloride-lactic acid (ChCl-LA) and choline chloride-oxalic acid (ChCl-OA) at 80-120 °C for 6 hours to produce the regenerated lignin and lignin oil. The yield of the regenerated lignin ranged from 44 to 75% after DES pretreatment. During ChCl-LA pretreatment, γ-acetylated groups in the regenerated lignin were observed at low temperatures and then deacylation occurred at high temperatures, which was beneficial for oxidizing lignin and producing phenolic diketones. Additionally, the depolymerization of lignin fractions was the dominant reaction during DES pretreatment, accompanied by partial condensation reactions. More importantly, this is the first report of obtaining S- and G-derived diketones from lignin oil after DES pretreatment. The degradation mechanism of lignin in the DES system has been proposed. This work opens a way to produce value-added chemicals from lignin in DESs, which needs to be researched in the future.We acknowledge the financial support for this research from the National Natural Science Foundation of China (31971613 and 31670587), the Fundamental Research Funds for the Central Universities (2015ZCQ-CL-02), and the Beijing Forestry University Outstanding Young Talent Cultivation Project (2019JQ03005 and 2019JQ03006)

Anti-diarrhea and anti-oxidant properties of Magnolol

Purpose: To provide an experimental basis for the anti-diarrheal and anti-oxidant properties of the bark extract of Magnolia officinalis Rehd. et Wils., a Chinese traditional herb called magnolol. Methods: The effects of magnolol on castor oil-induced diarrhea, small intestinal transit (SIT) in mice were investigated. Additionally, the antioxidant activity of magnolol was assessed in mice by the following parameters: glutathione (GSH), total antioxidant capacity (T-AOC), antioxidant enzyme activities and their gene expression level. Results: Compared with diarrhea model control group, magnolol (25, 50, or 100 mg/kg body weight) showed significant (p < 0.05) inhibitory activity against castor oil-induced diarrhea in mice. Administration of magnolol (25, 50, and 100 mg/kg) also lowered neostigmine-induced SIT acceleration to 60.34 ± 5.17, 59.61 ± 7.66, and 54.12 ± 7.27 %, respectively, as against 70.1 ± 6.89 % for neostigmine control group. In vivo antioxidant assay results showed that mice treated with magnolol exhibited significantly (p < 0.001) higher activities of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) activities in blood, compared to control. Similarly, magnolol proups showed significantly higher CAT and SOD and T-AOC activities (p < 0.01) than control in liver tissues. The 100 mg/kg magnolol group had significantly higher liver GSH content than normal control group (1.01 vs. 0.79 mg/mg protein). At 25 and 50 mg/kg doses, magnolol significantly enhanced gene expression levels of CAT (p < 0.01) in liver. Conclusion: Findings from this study indicate that magnolol possesses anti-diarrheal activity and is probably one of the main anti-diarrhea ingredients of Cortex Magnoliae Officinalis. Magnolol modulation of the activity and gene expression of antioxidant enzymes may therefore exert beneficial effects in antioxidant defense