Enhancing the Antioxidant Activity of Technical Lignins by Combining Solvent Fractionation and Ionic-Liquid Treatment
2019
Majira, Amel | Godon, Blandine | Foulon, Laurence | Putten, van der, Jacinta C. | Cézard, Laurent | Thierry, Marina | Pion, Florian | Bado-Nilles, Anne | Pandard, Pascal | Jayabalan, Thangavelu | Aguié-Béghin, Véronique | Ducrot, Paul Henri | Lapierre, Catherine | Marlair, Guy | Gosselink, Richard J.A. | Baumberger, Stephanie | Cottyn, Betty
A grass soda technical lignin (PB1000) underwent a process combining solvent fractionation and treatment with an ionic liquid (IL), and a comprehensive investigation of the structural modifications was performed by using high-performance size-exclusion chromatography, <sup>31</sup>P NMR spectroscopy, thioacidolysis, and GC–MS. Three fractions with distinct reactivity were recovered from successive ethyl acetate (EA), butanone, and methanol extractions. In parallel, a fraction deprived of EA extractives was obtained. The samples were treated with methyl imidazolium bromide ([HMIM]Br) by using either conventional heating or microwave irradiation. The treatment allowed us to solubilize 28 % of the EA-insoluble fraction and yielded additional free phenols in all the fractions, as a consequence of depolymerization and demethylation. The gain of the combined process in terms of antioxidant properties was demonstrated through 2,2-diphenyl-1-picrylhydrazyl (DPPH<sup>.</sup>) radical-scavenging tests. Integrating further IL safety-related data and environmental considerations, this study paves the way for the sustainable production of phenolic oligomers competing with commercial antioxidants.
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