Radical Scavenging Index Research Articles

Facile extraction of lignin-carbohydrate complexes from bamboo with formic acid aqueous solution under moderate conditions

The extraction of lignin-carbohydrate complexes (LCC) while preserving the majority of the interconnecting bonds poses a formidable challenge in characterizing the structure and exploring further applications. In this study, a straightforward approach was proposed to extract LCC from bamboo by precisely adjusting formic acid aqueous solution concentrations (70 % to 100 %) and reaction temperatures (40 to 100 °C) under normal pressure. Notably, employing a 90 % formic acid aqueous solution at 100 °C for 2 h led to an impressive LCC yield of 24.47 %. Moreover, all the LCC samples demonstrated exceptional homogeneity with a polydispersity index ≤ 1.97. Nuclear magnetic resonance analysis revealed the presence of phenyl glycosidic, benzyl ether, benzyl ester, and acetal bonds within the extracted LCC, with phenyl glycosidic bonds serving as the predominant linkages. The LCC samples displayed notable antioxidant capacity, as evidenced by their high DPPH free radical scavenging index of 1.28.

The structure and properties of lignin isolated from various lignocellulosic biomass by different treatment processes

The structure and properties of lignin can vary depending on the type of lignocellulosic biomass it comes from and the separation techniques used, and also affects its suitability for different applications. In this work, the structure and properties of lignin isolated from moso bamboo, wheat straw, and poplar wood by different treatment processes were compared. Results show that deep eutectic solvent (DES) extracted lignin exhibits well-preserved structures (including β-O-4, β–β, and β-5 linkages), a low molecular weight (Mn = 2300–3200 g/mol), and relatively homogeneous lignin fragments (1.93 < PDI < 2.33) compared to dealkaline lignin (DL) and milled wood lignin (MWL). Besides, lignin samples extracted by DES have a regular nanostructure, higher carbon residue content (>40 %), and excellent antioxidant properties (the free radical scavenging index >20). Among the three types of biomass, the structural destruction of lignin in straw is the most obvious, which is due to the degradation of β-O-4 and β-β linkages during DES treatment. These findings can contribute to a better understanding of the structural changes that occur in various treatment processes from different lignocellulosic biomass, and help maximize the targeted development of their applications based on the characteristics of lignin.

Quantification of phenolic constituents and bioactive properties of callus and leaf tissue of Citrus jambhiri lush

The chemical constituents of callus and leaf tissues of Citrus jambhiri Lush were extracted in methanol, ethanol and chloroform and the extracts were estimated for their total phenolic and flavonoid contents (TPC and TFC).Evaluation of antioxidant and antibacterial potential of callus and leaf extracts revealed that methanol extracts exhibited higher DPPH radical scavenging activity (radical scavenging index 4.55 of leaf extract and 9.09 of standard BHA).Further, these extracts were most effective against pathogenic bacteria (with inhibition zone diameters 8.0 and 8.9 mm against Escherichia coli and Salmonella typhi, respectively). Leaf extracts were found to contain slightly higher amounts of TPC and TFC and hence, higher antioxidant and antibacterial activities as compared to callus extracts.

Sequential extraction of organosolv lignin from Chinese quince fruit: Structural features and antioxidant activities of the obtained fractions

Lignin from the Chinese quince (Chaenomeles sinensis) fruit offers a promising source of natural antioxidant for industrial applications. However, the utilization of Chinese quince fruit lignin is restricted by its inhomogeneous nature. Accordingly, Chinese quince fruit lignin was sequentially fractionated with organic solvents of increasing dissolving capacity to prepare homogeneous lignin fractions. The GPC (gel permeation chromatography) results showed that the molecular weights of lignin fractions increased from dichloromethane fraction to dioxane/water fraction. The five lignin fractions were also compared with respect to yield, carbohydrate content, thermal stability, inter-unit linkages, S/G ratios, and phenolic OH content. Among the five fractions, the ethyl acetate fraction showed a lower proportion of β-O-4′ linkages (48.4%), the highest thermal stability, the highest phenolic OH content (2.8 mmol/g), and the highest DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging index and reducing power. The high antioxidant performance of the ethyl acetate fraction implies that it can be used as a natural antioxidant. This study shows that sequential solvent fractionation of lignin can produce homogeneous fractions with enhanced antioxidant performance. In addition, it demonstrates that Chinese quince fruits are a potentially valuable natural resource.

Structural features and antioxidant behavior of lignins successively extracted from ginkgo shells (Ginkgo biloba L)

Ginkgo shells as by-products from Ginkgo biloba L. industries with a remarkable annual output up to now are not fully analyzed and exploited. For the application of ginkgo shells beyond their current roles, structure and antioxidant activity of milled wood lignins successively extracted from two ginkgo shell species were investigated. Results showed lignin in ginkgo shells is abundant in guaiacyl units with the presence of ferulates and p-coumarates and demonstrates a high yield of vanillin (1.47–1.65 mmol/g-lignin) by nitrobenzene oxidation, much higher than general softwoods and hardwoods (0.6–0.9 mmol/g-lignin), which makes ginkgo shells good feedstocks for the production of food and beverage flavoring agent. By increasing the extent of ball-milling (4–8 h), the polydispersity of lignin molecular weight exhibits negligible change, but condensation and aldol interconversion occur to its Cβ/C5 structure and end-groups, respectively. Lignin in ginkgo shells also features outstanding antioxidant activity with the optimal radical scavenging index of 6.9, much higher than commercial butyl hydroxyanisole (3.85) and butylated hydroxytoluene (0.29), and the phenolic hydroxyl is demonstrated to dominate this contribution by the analysis of statistical product and service solutions. These results reveal lignin in ginkgo shells shows many unique structural and biological properties for materials.

Introduction and discussion about three types of fine grain products and their harvesters

Background:Melanogenesis begins with the oxidation of L-tyrosine to L-Dopa by tyrosinase. Inhibition of tyrosinase could be effective in treatment of complications such as skin lesions, eczema and melasma. Inhibition of tyrosinase could be effective in treatment of those complications. The aim of this study was to determine inhibitory activity on tyrosinase and antioxidant activity of Astragalus siliquosus Bioss. and Verbascum phoeniceum L. Methods:Methanol extracts of organs of the plants were prepared by maceration. Inhibitory effects of the extracts were evaluated in 96 wells at 492 nm wavelength. The antioxidant activity of the extracts was evaluated using DPPH free radical scavenging index and iron reduction test. Results;For A.siliquosus, maximum inhibitory activity was of its flower extract (97% inhibition and IC50=1.58 mg/ml) and of its stem extract (100 % and IC50=2.1 mg/ml). For V.phoeniceum, the highest inhibitory activity was of its leaf extract (87% inhibition and IC50=3.2 mg/ml). Flower extract of A.siliquosus showed mixed Uncompetitive-Non-competitive pattern of inhibitory activity, while the extract of the V.phoeniceum leaf showed mixed Competitive-Non-competitive inhibitory pattern. All aerial parts of the A.siliquosus had 100% antioxidant activity with EC50s of 0.089, 1.78, 1.25 mg/ml for its flower, leaf and stem respectively. Leaves of the V.phoeniceum had a 100% antioxidant activity, with EC50 of 0.013 mg/ml. Conclusions:Methanol extracts of flower and leaf organs of A.siliquosus, and leaf organ of V.phoeniceum, had a reasonable inhibitory effect on tyrosinase activity. Feature studies could be focused on those organs to separate potential agents with pharmaceutical and cosmetic applications.

Optimized microwave extraction, characterization and antioxidant capacity of biological polysaccharides from Eucommia ulmoides Oliver leaf

Microwave-induced technique was combined with response surface methodology for optimizing the isolation of polysaccharides from Eucommia ulmoides Oliver leaf. The maximum polysaccharides yield of 12.31% was achieved by microwave extraction at 74 °C for 15 min with a solid to liquid ratio of 1:29 g/mL, which agreed with the predicted value and was 2.9-fold higher than that of the conventional heat-reflux extraction method. The dominant bioactive constituent in extracts was chlorogenic acid (1.3–1.9%), followed by geniposidic acid (1.0–1.7%). The polysaccharides from the optimized extraction had a high molecular weight and polydispersity (Mw 38,830 g/mol, Mw/Mn 2.19), as compared to the fraction prepared in the absence of microwave (Mw 12,055 g/mol, Mw/Mn 1.26). Glucose was the dominant sugar component (38.2–39.1%) of heterogeneous polysaccharides which belonged to a structure of β-type acidic heteropolysaccharides with a glucan group and highly branched degree. The polysaccharides showed a higher DPPH radical scavenging index (0.87–1.22) than BHT (0.41) but lower than BHA (3.56), which can act as a favorable antioxidant in functional food.

Acetic acid lignins from Chinese quince fruit (Chaenomeles sinensis): effect of pretreatment on their structural features and antioxidant activities.

In this study, three pretreatment processes were evaluated for their effects on the structural features and antioxidant activities of lignins extracted by the acetosolv process from the fruit of Chinese quince. The three pretreatments included dephenolization, sugar removal, and multiple processes (a combination of both dephenolization and sugar removal). The results showed that after sugar removal pretreatment, the carbohydrate content, the molecular weight and S/G value of the lignin fractions decreased. However, after dephenolization pretreatment, the carbohydrate content and the molecular weight of the lignin fractions increased. After sugar removal and dephenolization, there were increases in the temperatures corresponding to the maximal rate of decomposition (DTGmax) in all lignin fractions. The radical scavenging index of lignin after sugar removal pretreatment was higher compared to other pretreatments and no treatment. The results of these tests showed that sugar removal, as a pretreatment, enhanced lignin extraction, yielding pure and highly functional lignins. Additionally, dephenolization or multiple process were beneficial to the acquisition of macromolecular lignins. All the results provided references for the biorefinery of biomass rich in polyphenol and sugar compounds.

Antioxidant and Antibacterial Activities of Sugarcane Bagasse Lignin and Chemically Modified Lignins

Unmodified lignin from sugarcane bagasse was chemically modified by acetylation, epoxidation and hydroxymethylation reactions. Modifications in lignin structure were characterized by FT-IR, 1H and 13C NMR spectra. The optimum reaction times for both epoxidation and hydroxymethylation of lignin were found to be 3 h by epoxy content and functional analysis, respectively. Acetylated and epoxy lignins were found to have lower DPPH radical scavenging activity [radical scavenging index (RSI) 0.15 and 0.16] than unmodified lignin (RSI 2.63), whereas hydroxymethyl derivative exhibited comparable activity (RSI 2.70) to unmodified lignin. Lignin and hydroxymethyl lignin were found to be more effective antioxidant than standard 3,5-di-tert-butyl-4-hydroxytoluene all lignins were found to be less effective than standard 3-tert-butyl-4-hydroxyanisole. Epoxy lignin was found to be most effective antibacterial among modified lignins with minimum inhibitory concentrations of 90 and 200 µg/disc against Bacillus aryabhattai and Klebsiella sp., respectively. It was concluded that natural lignin isolated from sugarcane bagasse and chemically modified lignins may be used as potential antioxidants and antibacterials.

Identifying the impact of ultrasound-assisted extraction on polysaccharides and natural antioxidants from Eucommia ulmoides Oliver

Ultrasound-assisted technique has been developed as complementary method to extract natural antioxidants and polysaccharides from Eucommia ulmoides Oliver. Additionally, polysaccharides were characterized by sugar analysis, FTIR, and GPC. The contents of eight main bioactive molecules were identified and quantified by HPLC. The results showed that ultrasound improved the yield and selectivity of the antioxidants and that the chemical properties of the polysaccharides were modified slightly. The contents of phenolics, flavonoids, and bioactive compounds were increased after ultrasonic treatment, but the increment varied between the different tissue parts. Meanwhile, aucubin and chlorogenic acid were the uppermost bioactive constituents of barks and leaves, respectively. The polysaccharides prepared with ultrasound exhibited slightly higher molecular weights (32,125–91,800g/mol) as compared to the fractions prepared without ultrasound (17,995–21,410g/mol). The extracts from leaves showed significant inhibitory activity, with radical scavenging index ranging from 3.22 to 4.17, which was higher than that of extracts from cortex (1.01–1.32), suggesting that the leaves exhibited much higher antioxidant activity than raw cortex. The in vitro antioxidant activity of concentrates correlated with their phenolic content.

Structural features and antioxidant activities of degraded lignins from steam exploded bamboo stem

A two-step process based on steam explosion pretreatment and alkali/alkaline ethanol post-treatments of bamboo stems was developed to produce bioethanol efficiently. In this study, alkali/alkaline ethanol post-treatments were applied to isolate lignins from steam exploded (1.8 and 2.0MPa for 5min, and 2.0MPa for 8min) bamboo stems, which resulted in the dissolution of 28.9, 53.3 and 60.1% of acid-insoluble lignins, respectively. The structural features of the isolated lignins were comparatively and comprehensively investigated by FT-IR and NMR techniques. The lignins showed low molecular weights (Mw, 860–1190g/mol), narrow polydispersities (Mw/Mn, 1.46–1.92), and high content of phenolic hydroxyl groups (0.53–1.79mmol/g). Antioxidant activities investigation showed that the radical scavenging index (RSI) of the extracted lignins (2.02–5.56) was higher than BHT (0.19) but lower than that of BHA (11.11). The relatively high antioxidant activity of the lignins suggested that they may be a potential antioxidant in food and other industries.

Sequential solvent fractionation of heterogeneous bamboo organosolv lignin for value-added application

Value-added utilization of lignin is affected by its heterogeneous nature. In this case, bamboo organosolv lignin was successively fractionated with organic solvents of increasing dissolving capacity (i.e., ether, ethyl acetate, methanol, acetone, and dioxane/water) to obtain homogeneous preparations. The starting lignin and the fractions obtained were compared in terms of molecular weight distribution and functional groups by a set of chemistry and spectroscopy technologies. It was found that the yield of the five fractions obtained was 2.80%, 39.85%, 18.64%, 23.38%, and 13.30%, respectively. The lignin fraction extracted with ethyl acetate contained homogeneous materials of low molecular weight whereas the lignin fraction extracted with acetone was composed of a mixture of medium and high molecular weight materials. As evidenced by sugar analysis, there was strong association between hemicelluloses and lignin in the preparations with different molecular weights. Spectroscopy analysis indicates that with increasing the dissolving capacity of solvent, the contents of methoxyl, phenolic, and aliphatic hydroxyl groups in the extracted lignin fractions were decreased. The lignin fraction extracted with ethyl acetate, having a high radical scavenging index (RSI), will be a good feedstock as stabilizer. The results above suggest that the sequential solvent fractionation provides a promising way to prepare lignin with homogeneous structure and good functional properties for potential application.

Unmasking the structural features and property of lignin from bamboo

In this study, a simple method based on DMSO/NMI (dimethylsulfoxide/N-methylimidazole) dissolved system for the isolation of dissolved lignin (DL) from bamboo was presented. The lignin extracted was studied as compared to milled wood lignin (MWL) and alkali lignin (AL). Quantitative 13C and 2D-HSQC NMR analysis indicated that all lignin preparations are HGS-type and partially acylated (below 12%) at the γ-carbon of the side chain by p-coumarate. In addition, some LCC linkages and acetylated β-d-xylopyranoside were distinguished from HSQC spectra in the specific lignin preparations. The abundances (Ar/100Ar) of β-O-4, β-β, and β-5, S/G ratios, acylation degree, phenolic hydroxyl, aliphatic hydroxyl and methoxy groups (mmol/g) were also observed in the lignin preparations. Furthermore, the amount of β-O-4 coupling and molecular weight of the lignin decreased in the order of DL<MWL<AL. The in vitro antioxidant activity results showed that the radical scavenging index (RSI) is correlated to the phenolic hydroxyl groups (Ar-OH) involved in the lignin preparations.

Microwave-enhanced extraction of lignin from birch in formic acid: Structural characterization and antioxidant activity study

A rapid and mild extraction protocol for the preparation of lignin was achieved by microwave-assisted heating in formic acid at 101°C under atmospheric pressure. In this case, birch lignin was extracted with microwave heating process (ML) in formic acid and characterized by elemental analysis, FTIR, GPC, 1H NMR and 13C–1H HSQC. In addition, the antioxidant activity of the samples was investigated. For comparative study, milled wood lignin (MWL) and lignin extracted with oil bath heating process (OL) were prepared. The results showed that the lignin yield under microwave heating was much higher than that under oil bath heating. A maximal delignification degree (89.77%) was achieved when microwave heating time was 30min. When double time (60min) was used under oil bath heating, the delignification degree was 66.11%. The structural characterization showed that the lignin structure of ML did not change dramatically, which is a mixture of GS-type with β-O-4′ ether bond as the major inter-unit linkage. As for antioxidant activity against DPPH, the radical scavenging index (RSI) of ML was 1.20, which was higher than that of MWL (0.53), suggesting that ML exhibited much higher antioxidant activity than MWL.

Microwave-assisted organic acid extraction of lignin from bamboo: Structure and antioxidant activity investigation

Microwave-assisted extraction in organic acid aqueous solution (formic acid/acetic acid/water, 3/5/2, v/v/v) was applied to isolate lignin from bamboo. Additionally, the structural features of the extracted lignins were thoroughly investigated in terms of C₉ formula, molecular weight distribution, FT-IR, (1)H NMR and HSQC spectroscopy. It was found that with an increase in the severity of microwave-assisted extraction, there was an increase of phenolic hydroxyl content in the lignin. In addition, an increase of the severity resulted in a decrease of the bound carbohydrate content as well as molecular weight of the lignin. Antioxidant activity investigation indicated that the radical scavenging index of the extracted lignins (0.35-1.15) was higher than that of BHT (0.29) but lower than that of BHA (3.85). The results suggested that microwave-assisted organic acid extraction provides a promising way to prepare lignin from bamboo with good antioxidant activity for potential application in the food industry.