Organosolv Ethanol Lignin from Hybrid Poplar as a Radical Scavenger:  Relationship between Lignin Structure, Extraction Conditions, and Antioxidant Activity

Abstract

Twenty-one organosolv ethanol lignin samples were prepared from hybrid poplar (Populus nigra xP. maximowiczii) under varied conditions with an experimental matrix designed using response surface methodology (RSM). The lignin preparations were evaluated as potential antioxidants. Results indicated that the lignins with more phenolic hydroxyl groups, less aliphatic hydroxyl groups, low molecular weight, and narrow polydispersity showed high antioxidant activity. Processing conditions affected the functional groups and molecular weight of the extracted organosolv ethanol lignins, and consequently influenced the antioxidant activity of the lignins. In general, the lignins prepared at elevated temperature, longer reaction time, increased catalyst, and diluted ethanol showed high antioxidant activity. Regression models were developed to enable the quantitative prediction of lignin characteristics and antioxidant activity based on the processing conditions.

Midwest vision for sustainable fuel production

“…The phenolic oligomers, derived from depolymerization of lignin, exist as a viscous, low volatility material that is highly reactive due to the vinyl and carbonyl functional groups associated with the phenol moieties [54]. This reactivity causes the phenolic oligomers to polymerize when heated.…”

Potential of Lignins as Antioxidant Additive in Active Biodegradable Packaging Materials

“…Furthermore, properties potentially interesting in high value applications, such as antimicrobial activity [12] or cytotoxic effects [13] have been shown. The antioxidant properties of lignins stem from their radical scavenging capacity [13][14][15][16][17], following the general mechanism of monomeric phenols. The hindered phenolic hydroxyl groups being part of the lignin structure act as proton donors and are able to stabilize the radical in the quinone resonance structure [16].…”

“…The antioxidant properties of lignins stem from their radical scavenging capacity [13][14][15][16][17], following the general mechanism of monomeric phenols. The hindered phenolic hydroxyl groups being part of the lignin structure act as proton donors and are able to stabilize the radical in the quinone resonance structure [16]. Radical scavenging activity is described for a large number of lignin sources, ranging form black liquors [18] to the description of different botanic sources such as miscanthus [19], oak chips [20], bamboo [21] and many others.…”

“…Radical scavenging activity is described for a large number of lignin sources, ranging form black liquors [18] to the description of different botanic sources such as miscanthus [19], oak chips [20], bamboo [21] and many others. In general, radical scavenging activity of lignin is negatively influenced by increasing heterogeneity, dispersity, molecular weight average and carbohydrate admixtures [13,15,16]. Lignins extracted in sodium hydroxide aqueous medium (alkali lignins) have been shown to have higher activity than other types of lignins, such as lignosulfonates, Kraft, or steam explosion lignin, with a radical scavenging activity similar to that of epicatechin, used as a reference antioxidant [14,17].…”

Biological Treatment of Poplar Wood with White-rot Fungus Trametes hirsuta C7784: Structural Elucidation of the Whole Lignin in Treated Wood

“…To improve the solubility of the lignin fractions in the THF eluent, all isolated lignin samples were acetylated prior to GPC analysis. MWL acetylation was performed as reported by Pan et al (2006), while REL acetylation was performed using the method of Lu and Ralph (2013). Two-dimensional heteronuclear single-quantum coherence (2D HSQC) NMR spectra of the MWLs and acetylated RELs (REL-Ac) were recorded using a Bruker AVIII 400 MHz spectrometer (Karlsruhe, Germany) operated at 25 °C using DMSO-d6 solvent, as reported by Yuan et al (2010).…”