Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties
Lignin is an abundant and environmentally friendly biopolymer that contains a large number of phenolic hydroxyl functional group. In this paper, alkaline lignin was modified using different acidic DES (choline chloride/<i>p</i>-toluenesulfonic acid and choline chloride/lactic acid) at 13...
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MDPI AG
2023-03-01
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| author | Penghui Li Yuan Lu Guifang Long Sixian Li Kongyan Li Bo Jiang Wenjuan Wu |
| author_facet | Penghui Li Yuan Lu Guifang Long Sixian Li Kongyan Li Bo Jiang Wenjuan Wu |
| author_sort | Penghui Li |
| collection | DOAJ |
| description | Lignin is an abundant and environmentally friendly biopolymer that contains a large number of phenolic hydroxyl functional group. In this paper, alkaline lignin was modified using different acidic DES (choline chloride/<i>p</i>-toluenesulfonic acid and choline chloride/lactic acid) at 130 ℃ (TC-lignin and LC-lignin) and the conformational relationship between the modified products and the antioxidant activity was investigated. Lignin was characterized by <sup>31</sup>P NMR, gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FT-IR), and its antioxidant activity was evaluated. The results showed that the alkaline lignin products modified by acidic DES formed relatively homogenous dispersions and were characterized by a relatively low molecular weight and a high content of phenolic hydroxyl groups (e.g., TC-lignin, aliphatic-OH: 3.52 mmol/g, G-OH: 4.18 mmol/g, M<sub>w</sub>: 3726, M<sub>n</sub>: 2053, PDI: 1.81). The antioxidant activity (free radical scavenging rate, 90.35%) of TC-lignin was somewhat higher than that of LC-lignin (free radical scavenging rate, 89.12%) and both were higher than that of the commercially available antioxidant BHT (free radical scavenging rate, 88.79%). More specifically, we discussed the possible mechanisms of antioxidant reactions of lignin model substances in DPPH solutions. In addition, LC-lignin has an excellent UV-blocking capacity due to the specific phenolic hydroxyl and phenyl propane structure. A simple method is proposed for the modification of industrial lignin to make it suitable for use as an antioxidant and UV-resistant product. |
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| series | Forests |
| spelling | doaj.art-a26f6667b34f45acb7dfcb009954f6232023-11-17T11:10:09ZengMDPI AGForests1999-49072023-03-0114355010.3390/f14030550Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant PropertiesPenghui Li0Yuan Lu1Guifang Long2Sixian Li3Kongyan Li4Bo Jiang5Wenjuan Wu6Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Light Industry and Food Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Light Industry and Food Engineering, Nanjing Forestry University, Nanjing 210037, ChinaCollege of Light Industry and Food Engineering, Nanjing Forestry University, Nanjing 210037, ChinaJiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, ChinaJiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing Forestry University, Nanjing 210037, ChinaLignin is an abundant and environmentally friendly biopolymer that contains a large number of phenolic hydroxyl functional group. In this paper, alkaline lignin was modified using different acidic DES (choline chloride/<i>p</i>-toluenesulfonic acid and choline chloride/lactic acid) at 130 ℃ (TC-lignin and LC-lignin) and the conformational relationship between the modified products and the antioxidant activity was investigated. Lignin was characterized by <sup>31</sup>P NMR, gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FT-IR), and its antioxidant activity was evaluated. The results showed that the alkaline lignin products modified by acidic DES formed relatively homogenous dispersions and were characterized by a relatively low molecular weight and a high content of phenolic hydroxyl groups (e.g., TC-lignin, aliphatic-OH: 3.52 mmol/g, G-OH: 4.18 mmol/g, M<sub>w</sub>: 3726, M<sub>n</sub>: 2053, PDI: 1.81). The antioxidant activity (free radical scavenging rate, 90.35%) of TC-lignin was somewhat higher than that of LC-lignin (free radical scavenging rate, 89.12%) and both were higher than that of the commercially available antioxidant BHT (free radical scavenging rate, 88.79%). More specifically, we discussed the possible mechanisms of antioxidant reactions of lignin model substances in DPPH solutions. In addition, LC-lignin has an excellent UV-blocking capacity due to the specific phenolic hydroxyl and phenyl propane structure. A simple method is proposed for the modification of industrial lignin to make it suitable for use as an antioxidant and UV-resistant product.https://www.mdpi.com/1999-4907/14/3/550DESligninantioxidantUV protection |
| spellingShingle | Penghui Li Yuan Lu Guifang Long Sixian Li Kongyan Li Bo Jiang Wenjuan Wu Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties Forests DES lignin antioxidant UV protection |
| title | Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties |
| title_full | Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties |
| title_fullStr | Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties |
| title_full_unstemmed | Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties |
| title_short | Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties |
| title_sort | structural characterization of acid des modified alkaline lignin and evaluation of antioxidant properties |
| topic | DES lignin antioxidant UV protection |
| url | https://www.mdpi.com/1999-4907/14/3/550 |
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