Antioxidant Activity Of Lignin Research Articles

Lignin from Residual Sawdust of Eucalyptus spp.—Isolation, Characterization, and Evaluation of the Antioxidant Properties

Lignin is an abundant biopolymer, as well as cellulose and hemicellulose. Thus, this work aimed at isolating and characterizing the lignin from Eucalyptus spp. Sawdust—a lignocellulosic waste generated in large amounts in sawmills—to evaluate its antioxidant capacity. A biorefinery perspective was utilized: the biomass was fractionated using a sequential acid-alkaline treatment to recover the hemicellulosic carbohydrates, preserving the cellulose-rich solid fraction and isolating the lignin. The physicochemical characterization of isolated lignin was carried out using thermogravimetric (TGA), Fourier-transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) analyses, while the antioxidant property was evaluated employing electron transfer and using DPPH and ABTS assays. After sequential acid-alkaline treatment, 68.15% of the hemicellulosic carbohydrates were recovered using mild acid treatment. The specific yield of lignin was 69.38%, and the remaining solid fraction contained 60.42% of cellulose. The antioxidant activity of lignin was evaluated using a DPPH radical test, and it showed an inhibition of 81.58% and IC50 of 60 μg/mL. For the ABTS test, the inhibition was 99.86%, and the IC50 was 7.39 µg/mL. Therefore, the lignin isolated from residual eucalyptus sawdust using sequential acid-alkaline treatment presented interesting antioxidant properties, which should be further investigated and evaluated for different applications.

Effect of CO2 Concentration on Improving Yield and Antioxidant Activity of Lignin from Corn Cobs

Effect of CO2 Concentration on Improving Yield and Antioxidant Activity of Lignin from Corn Cobs

Effect of Two-Step Formosolv Fractionation on the Structural Properties and Antioxidant Activity of Lignin.

The formosolv fractionation process has been demonstrated to be an effective approach toward lignin recovery as an antioxidant from lignocellulosic biomass. In this study, four lignin fractions, FL-88%, FSL-70%, FIL-70% and FL-EtAc, were isolated from Phragmites australis biomass through two-step formosolv fractionation (88% formic acid delignification followed by 70% aqueous formic acid fractionation). To better understand the structural properties of the lignin obtained from this fractionation process, four isolated lignins were successfully characterized by gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy, thermogravimetric analysis (TGA) and gas chromatograph-mass spectroscopy (GC/MS). It was found that lignin depolymerization via β-O-4 cleavage occurred via a formylation, elimination and hydrolysis mechanism, accompanied by a competitive condensation reaction. Noteworthily, two-step formosolv fractionation can produce specific lignin fractions with different ABTS and DPPH radical scavenging activities. The FL-EtAc fraction with low molecular weight (Mw = 2748 Da) and good homogeneity (PDI = 1.5) showed excellent antioxidant activity, compared with the other three isolated lignin fractions, even equal to that of commercial antioxidant BHT at the same concentration of 2.0 mg·mL−1. These findings are of great help for specific lignin from biomass as a natural antioxidant in the future.

Structural analysis of light-colored separated lignin (lignocresol) and its antioxidant properties

The use of lignin is limited by its heterogeneity and complexity. This study was processed using different methods to obtain spruce milled wood lignin (SMWL), spruce kraft lignin (SKL), and spruce lignocresol (SLC) for comparative analysis of the structure and antioxidant activity. SMWL has a complete softwood lignin side-chains structure and lignin carbohydrate complexes. SKL contains fewer ether bonds, while more conjugate structures and condensed structures contribute to the color. However, the α-position of the lignin side chain eliminates most of the hydroxyl and ether bonds (β-O-4/α-OH, phenylcoumaran, and dibenzodioxocine structure) and effectively grafts p-cresol in the phase separation reaction. It not only inhibits the self-condensation of lignin, but also forms the 1,1-diarylpropane unit while protecting β-O-4 linkages from not breaking. Importantly, SLC has few conjugate structures that result in the lightest color among all lignin isolated. Besides, SLC has a high yield and contains trace carbohydrates, indicating that the phase separation method can achieve great amounts of purity separated lignin. The antioxidant activity of lignin was evaluated, results show that 85% of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals were scavenged at the end of 60 min. Owing to its unique color, structural properties, and continuous antioxidant activity, SLC has the potential to manufacture antioxidant cosmetics.

Enhancement of the antioxidant abilities of lignin and lignin-carbohydrate complex from wheat straw by moderate depolymerization via LiCl/DMSO solvent catalysis

A facile and environmentally-friendly strategy for increasing antioxidant activity is a crucial issue for value-added lignin and lignin-carbohydrate complex (LCC) as alternative antioxidants. However, the antioxidant activities of lignin and LCC by the traditional solid-liquid extraction (SLE) methods were restricted by the relatively lower solubility induced from high molecular weight (Mw), and the less functional groups including, phenolic hydroxyl and carboxyl. To improve the antioxidantion of lignin and LCC, lithium chloride/dimethyl sulfoxide (LiCl/DMSO) solvent fractionation (LDSF) was conducted to increase the functional groups and reduce Mw, in which LiCl/DMSO acted triple roles as solvent, acid, and metal chloride catalyst for the depolymerization reaction synchronously. The β-O-4′ linkages were cleaved to release the phenolic hydroxyl, resulting in decreasing Mw; the hydroxyl of the side-chain of lignin was oxidized into carboxyl. Thus, the lignin (LD-RL) and LCC (LD-LCC) samples from LDSF had a higher syringyl (S)/guaiacyl (G) ratio, phenolic hydroxyl, and carboxyl contents, but less Mw than control groups from SLE. Consequently, they presented more excellent scavenging rates toward DPPH and ABTS radicals, up to 90%. This work provided panoramic perspectives and basics of the green and convenient approach to isolate and modify lignin and LCC for great antioxidantion with LDSF.

Study on the Antioxidant Activity of Lignin and Its Application Performance in SBS Elastomer

The technical enzymatic hydrolysis lignin (EHL) and alkali lignin (AKL) were pretreated via alkaline depolymerization and organic solvent extraction process, respectively. The molecular weight of l...

Structure-antioxidant activity relationship of active oxygen catalytic lignin and lignin-carbohydrate complex

Lignin, as a natural antioxidant, has a great potential to replace the chemosynthetic ones due to this material benefits of being biodegradable, eco-friendly, abundant and low-cost. However, the commonly-used lignins, such as acid, kraft and alkali lignins, have the poor antioxidant ability, and their antioxidative mechanism and kinetics remain poorly understood. Moreover, the understanding of the effect of polysaccharides in lignin-carbohydrate complex (LCC) on lignin antioxidant activity is also extremely insufficient. Herein, we isolated lignin and LCC from rice straw and its alkali-oxygen spent liquor to investigate their structure-antioxidant activity relationship and antioxidative mechanism. Experimental results illustrated that the alkali-oxygen treatment can significantly enhance the antioxidant activity of lignin. Demethoxylation, ring-opening and the cleavage of aryl ether bonds occur to lignin structure leading to the decrease of molecular weight, while the more stable condensed β-1′, 5–5′ and β-5′ linkages maintain the thermostability of this antioxidant. The synergistic effect of adjacent methoxyl with phenolic hydroxyl is the key factor that endows lignin with the outstanding antioxidant activity. In contrast, oligosaccharides formed by alkali-oxygen treatment have a negative influence on the antioxidant activity of lignin. This work demonstrates that alkali-oxygen lignin is a promising antioxidant to replace chemosynthetic ones for polymeric materials.

Characterization and evaluation of antioxidation of lignin from bamboo powder using a formic acid-catalyzed ethanol organosolv process

The antioxidant activity of lignin for producing biochemicals has attracted attention. In this paper, a separation method for lignin is proposed, with high-yield and high-antioxidant activity by using a formic acid-catalyzed subcritical ethanol process. The formic acid-catalyzed ethanol lignin (EOL/FA) and ethanol organosolv lignin (EOL) were first prepared using a high-pressure autoclave at different formic acid dosages. Then, the antioxidant activity and the structural and thermal properties of EOL/FA, EOL, alkali lignin, and sodium lignosulfonate were analyzed using antioxidant analysis, Fourier transform infrared (FTIR) spectroscopy analysis, and thermogravimetric analysis (TGA). The phenolic hydroxyl content of the four lignins was also determined by the Folin–Ciocalteau colorimetric method. Results showed EOL/FA had a higher radical scavenging ability and higher total phenolic hydroxyl content than industrial lignin. It indicated that the formic acid-catalyzed subcritical ethanol process was effective for enhancing the antioxidant activity of lignin.

Structural Characterization and Antioxidant Activity of Lignin Extracted from Ficus Carica L.

Structural Characterization and Antioxidant Activity of Lignin Extracted from Ficus Carica L.

Structural elucidation and antioxidant activity of lignin isolated from rice straw and alkali‑oxygen black liquor

Alkali‑oxygen cooking of lignocellulose offers lignin many structural properties and bioactivities for biorefinery. In this work, milled wood lignin (MWL) and alkali‑oxygen lignin (AOL) were isolated from rice straw and alkali‑oxygen black liquor, respectively. The lignin structure was characterized by spectroscopy and wet chemistry. Antioxidant activity of lignins was assessed by DPPH·and ABTS scavenging ability assay. Results showed the oxidization and condensation of lignin occurred during alkali‑oxygen cooking. The p-hydroxyphenyl was more easily removed from rice straw than guaiacyl and syringyl units. The ester or ether linkages derived from hydroxycynnamic acids, and the main interunit linkages, i.e. β–O–4′ bonds, were mostly cleaved. Lignin-xylan complex had high reactivity under alkali‑oxygen condition. Tricin, incorporated into lignin, was detected in MWL but was absent in AOL. Nitrobenzene oxidation showed MWL can well represent the protolignin of rice straw, and the products yield decreased dramatically after alkali‑oxygen cooking. AOL had higher radical scavenging ability than MWL indicating alkali‑oxygen cooking was an effective pathway for the enhancement of antioxidant activity of lignin.

Fractionation of technical lignin with ionic liquids as a method for improving purity and antioxidant activity

Alder soda lignin, a by-product of the chemical processing of black alder wood, was fractionated using ionic liquids (ILs) based on the 1-buthyl-3-methylimidazolium [Bmim] cation and the following anions: chloride ([Bmim]Cl), dimethylphosphate ([Bmim]Me2PO4), acetate ([Bmim]OAc) and tosylate ([Bmim]OTs). The aim was to obtain lignin fractions of improved purity for further application as antioxidants. The purity and properties of the IL lignin fractions were compared with those of other lignin fractions obtained using sequential extraction with organic solvents. The original lignin and the lignin fractions were characterized by analytical pyrolysis (Py-GC/MS/FID), size-permeation chromatography (GPC), electron paramagnetic resonance (EPR) spectroscopy and wet chemistry methods. The lignin treatment with [Bmim]DMP, [Bmim]OAc and [Bmim]OTs produced fractions with a lignin content of 98–99%. These fractions along with the n-propanol and methanol fractions obtained using sequential organic solvent extraction were enriched with certain structural features that had a positive impact on lignin antioxidant activity, according to the results from DPPH and ORAC assays.

Structural characterization and antioxidant activity of lignin from sugarcane bagasse

The aim of the present study was to extract lignin from sugarcane bagasse followed by its structural characterization, oxidation, and evaluation of antioxidant activities. Lignin was extracted in a process involving different concentrations (1, 5, and 10 %) of NaOH solutions. The chemical composition of untreated and treated bagasse samples was analyzed which clearly showed that the delignification was found to be maximum with 10 % NaOH. The scanning electron microscopy (SEM) images of untreated and treated samples of bagasse were taken to study the physical changes occurred in the bagasse during different treatments. Lignin extracted was purified with acidified water and oxidized with 10 % H2O2. Both lignin and oxidized lignin were structurally characterized using Fourier-transformed infrared (FTIR), 1H, and 13C NMR spectra. The antioxidant potential of lignin and its oxidized derivative was evaluated by radical scavenging activity using DPPH method. Lignin was found to have higher antioxidant activity than oxidized lignin. This was attributed to a higher number of phenolic groups in lignin than in oxidized lignin. Both lignin and its oxidized derivative were observed to have higher antioxidant activity than 3,5-di-tert-butyl-4-hydroxytoluene (BHT) and lower than 3-tert-butyl-4-hydroxyanisole (BHA). It was concluded that sugarcane bagasse lignin and its oxidized derivative could be used as potential antioxidant of food oils and fats.

Role of paramagnetic polyconjugated clusters in lignin antioxidant activity (in vitro)

Using physico-chemical methods (EPR, SEC, Py-GC/MS and UV/VIS spectroscopy) and wet chemical analysis, the characteristics of 6 hardwood lignins in terms of functionality, molecular weight and composition of lignin substructures were determined and considered together with the results of DPPH•, ABTS•+ and O2•− antioxidant assays with the aim to understand the relationships governing antioxidant properties of lignin. The strong positive linear correlation between lignin antioxidant capacity in the three assays used and the extent of conjugation of paramagnetic polyconjugated clusters in lignin macromolecules was found. The biological activity of the most active alkaline lignins was assessed by in vitro experiment with human blood.

Antimicrobial and antioxidant activities of lignin from residue of corn stover to ethanol production

To improve the economic viability of the biofuel production from biomass resource, a value-added lignin byproduct from this process is increasingly important. Antioxidant and antimicrobial activities of lignin extracted from residue of corn stover to ethanol production were investigated. The lignin extracts exhibited strong antioxidant activities in hydrophilic oxygen radical absorbance capacity (ORAC) assay and Folin–Ciocalteu test. The extracts also exhibited antimicrobial activities against Gram-positive bacteria ( Listeria monocytogenes and Staphylococcus aureus) and yeast ( Candida lipolytica), but not Gram-negative bacteria ( Escherichia coli O157:H7 and Salmonella Enteritidis) or bacteriophage MS2. Different extraction conditions (temperature and residue/solvent ratio) affected the antioxidant and antimicrobial activities of lignin extracts. Generally, the bioactivities of lignin extracts were consistent with FTIR analysis results. Lignin byproducts showed the potential for their antioxidant and antimicrobial application.

ANTIOXIDANT CAPACITY OF LIGNIN FROM GREEN TEA WASTE

ABSTRACT The antioxidant capacity of lignin from used green tea leaves was evaluated by measuring its effects on the autoxidation of linoleic acid. Autoxidation of linoleic acid was reduced by 50% in the presence of tea leaf lignin. This effect was weaker than that of α-tocopherol and t-butylhydroxyanisole. However, lignin enhanced the antioxidant effects of α-tocopherol, epigallocatechin gallate or acetone extracts of used tea leaves, with the antioxidant activity of lignin + acetone extracts of used tea leaves being nearly equivalent to that of α-tocopherol and t-butylhydroxyanisole. PRACTICAL APPLICATIONS The agricultural industry generates large amounts of botanical food by-products, including used tea leaves, most of which are discarded. To determine whether lignin extracted from used green tea leaves has a practical application, we measured its effect on the autoxidation of linoleic acid, a model for the oxidation of fats. We found that lignin contained in used green tea leaves has an antioxidant effect, suggesting that used tea leaves in industrial waste may have potential applications as antioxidants for food oils and fats.