Number Of Phenolic Hydroxyl Groups Research Articles

Investigation of the anti-inflammatory and antioxidant activities of luteolin, kaempferol, apigenin and quercetin

Luteolin, kaempferol, apigenin and quercetin are four common flavonol glycoside compounds found in many plants that possess multiple biological activities. The current study focused on their anti-inflammatory and antioxidant activities in vitro by assaying the NO content, phagocytosis, DPPH and ABTS radical scavenging activities and ferric reducing antioxidant power. This study indicated that all four compounds at concentrations of 50, 100 and 200 μM could reduce both the concentration of NO and phagocytosis; their antioxidant activities increased as the concentration increased from 0.5 to 32.0 μg/ml; the IC50 DPPH values were 2.099, 5.318, 1.84, 10.5 and 3.028 μg/ml for luteolin, kaempferol, quercetin, BHT and VC, respectively; the IC50 ABTS values were 0.59, 0.8506, 0.8243, 0.5083, 1.4497 and 2.1563 μg/ml for luteolin, kaempferol, apigenin, quercetin, BHT and VC, respectively; and the FRAP values ranged from 0.0101 to 0.0402 mmol Fe2+/μg/ml for the six compounds. Compared with the test results, quercetin is a perfect anti-inflammatory and antioxidant agent that has potential as an adjuvant treatment for inflammatory diseases and oxidative stress. In addition, this research preliminarily revealed that antioxidant activity is directly proportional to the number of phenolic hydroxyl groups, and after comparison of the anti-inflammatory and antioxidant activities, the compounds with enol groups were superior to those without enol groups, which will be further verified in future in vivo experiments.

Inhibitory activities of flavonoids from Eupatorium adenophorum against acetylcholinesterase

Fifteen flavonoids isolated from the Eupatorium adenophorum showed inhibitory activities against acetylcholinesterase (AChE) isolated from Caenorhabditis elegans and Spodoptera litura. Their IC50 values ranged from 12.54 to 89.06μg/mL and 12.08 to 86.01μg/mL, respectively against the AChE isolated from the nematode and insect species. AChE was inhibited in a dose-dependent manner by all tested flavonoids, The isolated compound quercetagetin-7-O-(6-O-caffeoyl-β-D-glucopyranoside) displayed the highest inhibitory effect against AChE from C. elegans and S. litura, with IC50 values of 12.54 μg/mL and 12.58 μg/mL, respectively. The structure-activity relationship of flavonoids on the inhibitory activities indicated that additional phenolic hydroxyl groups in the glucose were favorable for their inhibitory effects and the degree of increase in inhibitory activity also depended on the number of phenolic hydroxyl groups. The Lineweaver-Burk and Dixon plots indicated that quercetagetin-7-O-(6-O-caffeoyl-β-d-glucopyranoside) is a reversible inhibitor against AChE. Quercetagetin-7-O-(6-O-caffeoyl-β-d-glucopyranoside), 5,4′-Dihydroxytlavone and quercetin-3-O-β-d-glucopyranoside inhibited AChE in a mixed-type competitive manner and these compounds might be the dual binding site AChE inhibitors. Further, nine compounds showed poisonous effects against C. elegans and inhibitory effects on the growth and development of S. litura.

Highly active Pd-Fe/α-Al2O3 catalyst with the bayberry tannin as chelating promoter for CO oxidative coupling to diethyl oxalate

A novel Pd-Fe/α-Al2O3 catalyst was synthesized by incipient-wetness impregnation method with bayberry tannin as chelating promoter and commercial hollow column Raschig ring α-Al2O3 as support for the synthesis of diethyl oxalate from CO and ethyl nitrite. A variety of characterization techniques including N2 physical adsorption, optical microscopy, scanning electron microscopy and energy dispersive system (SEM-EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), were employed to explore the relationship between the physicochemical properties and activity of catalysts. It indicated that a large number of phenolic hydroxyl groups in bayberry tannin can efficiently anchor the active component Pd, reduce the particle size and make the active Pd as a multi-ring distribution on the commercial α-Al2O3 support, which were beneficial to improve the catalytic activity for the production of diethyl oxalate from CO and ethyl nitrite. 0.3 wt% Pd-Fe/α-Al2O3 showed excellent catalytic activity and selectivity in a continuous flow, fixed-bed reactor with the loading amount of 10 mL catalysts. Under the mild reaction conditions, the space-time yield of diethyl oxalate was 978gL−1 h−1 and CO conversion was 44% with the selectivity to diethyl oxalate of 95.5%.

Augmenting Therapeutic Potential of Polyphenols by Hydrogen-Bonding Complexation for the Treatment of Acute Lung Inflammation.

Dysregulated inflammation is considered as an essential pathological process in inflammation-associated diseases, which would be aggravated by high levels of reactive oxygen species (ROS) generation inducing oxidative stress. Currently, extensive attention has been paid to polyphenolic compounds owing to their broad spectrum biological activities, such as antioxidant and anti-inflammatory effects, while their therapeutic potential has been compromised by the poor stability, short plasma half-life, and low bioavailability. Given that polyphenols have a wide range of structural characteristics and various physicochemical properties, there remains a real challenge toward green, mass production of universal nanocarriers for effective entrapment of these active pharmaceutical ingredients. In this study, we adopted a flash nanocomplexation (FNC) platform to prepare nanocomplexes comprising polyphenols and d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) enabled by hydrogen bonding. We confirmed that the molecular structure of polyphenols has a great influence on their complexation with TPGS, and stable nanocomplexes were formed when the number of phenolic hydroxyl groups of polyphenols was above the value of 8. These hydrogen-bonded nanocomplexes produced by an FNC apparatus exhibited well-controlled quality with uniform size, good colloidal stability, and high batch-to-batch repeatability, thus improving the druggability as potent nanotherapeutics for antioxidant and anti-inflammatory applications. In vivo experiments indicated that the optimal nanocomplex (EGCG-NC) can be applied to ameliorate acute lung injury in a mice model after nasal administration. These results proved that polyphenols formulated with TPGS for nanocomplex formation through hydrogen-bonding complexation could augment their therapeutic potential for modulating hyperactive inflammation in the treatment of acute lung inflammation.

Mitigation of lipid oxidation in tuna oil using gelatin pouches derived from horse mackerel (Trachurus japonicus) scales and incorporating phenolic compounds

Mitigative effects of phenolic compounds on lipid oxidation of tuna oil in gelatin film pouches from horse mackerel (Trachurus japonicus) scales were investigated during storage at 40 °C for 30 days under dark conditions. Improvements in the antioxidant activity of gelatin films were observed following the addition of phenolic compounds. Increases in peroxide values (PV) and 2-thiobarbituric acid reactive substance (TBARS) levels of tuna oil were significantly mitigated using gelatin pouches with ferulic acid, which had the fewest phenolic hydroxyl groups among the phenolic compounds tested. The ferulic-gelatin film also exhibited the highest DPPH radical-scavenging activity among the tested samples. These results indicate that the oxidation of lipids in tuna oil can be mitigated using gelatin films containing phenolic compounds, but its antioxidant activity is not directly related to the number of phenolic hydroxyl groups. Protein crosslinking in gelatin film is likely to be induced by aldehydes such as malondialdehyde (MDA), which is a final product of lipid oxidation, and this was observed following storage of tuna oil. Thus, it is suggested that care should be taken when using TBARS levels to evaluate lipid oxidation of foods in fish gelatin film pouches, since aldehydes including MDA are consumed for protein crosslinking.

Small molecule-mediated self-assembly behaviors of Pluronic block copolymers in aqueous solution: impact of hydrogen bonding on the morphological transition of Pluronic micelles.

The influence of hydrogen bonding on the self-assembly behaviors of Pluronic P123 micelles is experimentally and theoretically investigated by introducing three small molecules, i.e. propyl benzoate (PB), propyl paraben (PP) and propyl gallate (PG) into the aqueous solution. It is discovered that the number of phenolic hydroxyl groups and concentration of the tested small molecules exhibit a profound impact on the micellar morphology. Although all the small molecules increase the size and polydispersity of Pluronic micelles in a concentration-dependent manner, the micellar morphologies induced by them vary considerably as demonstrated by DLS and cryo-TEM measurement. PB, without phenolic hydroxyl, cannot bring about the morphological change of P123 micelles, while PP induces a series of morphological transitions from spheres to long worm-like micelles and then to unilamellar vesicles by increasing the PP content. Upon increasing the number of phenolic hydroxyls in small molecules, i.e. PG, the fusion of the intermicellar core takes place, resulting in the formation of large micelles and micellar clusters. A qualitative study by NMR reveals that the different locations of small molecules within the micelles are attributed to the balance of hydrogen bonding and hydrophobic interaction between small molecules and copolymers. In addition, molecular dynamics simulations (MDS) are performed to further confirm the experimental results and provide quantitative information on intermolecular interaction strength. It is supposed that the mechanism of micellar morphological transition mediated by small molecules is ascribed to the hydrogen bonding interactions with varying strengths between the PEO blocks and their phenolic hydroxyls, which governs their locations in micelles, affecting the free energies from different regions of micelles, and consequently leads to the varying micellar morphologies. This study deepens our understanding of the role of hydrgen bonding in the self-assembly behaviors of Pluronic micelles and provides an alternative strategy for manipulating the nanostructure of Pluronic micelles.

Synthesis of Schiff bases modified inulin derivatives for potential antifungal and antioxidant applications

In this study, the structure of inulin was chemically modified by Schiff bases in order to improve its biological activity. A total of 6 kinds of inulin derivatives were synthesized according to aza-Wittig reaction. Their structures were confirmed by FTIR, 1H NMR, and 13C NMR spectroscopy. The antioxidant activity of the inulin derivatives was evaluated in vitro. Their antifungal activities against three kinds of plant pathogenic fungi, including Botrytis cinerea, Fusarium oxysporum f. sp. cucumerium Owen, and Phomopsis asparagi, were also studied. The results showed that the biological activities of the derivatives were significantly improved compared to pure inulin. 3HBSAIL could completely scavenge hydroxyl radical and DPPH radical at 1.6mgmL−1. 3,4DHBSAIL and 2,3,4THBSAIL exhibited strong antioxidant activity as far as the four tested antioxidant systems. Moreover, the scavenging rates of 3,4DHBSAIL and 2,3,4THBSAIL against DPPH radicals were both 100% even at the lowest test concentration (0.1mgmL−1). The synthetic inulin derivatives showed a broad antifungal spectrum against the tested fungi. At 1.6mgmL−1, the inhibitory rates of 3HBSAIL against Botrytis cinerea, Fusarium oxysporum f. sp. cucumerium Owen, and Phomopsis asparagi were 93%, 83%, and 82%, respectively. The biological activities of the inulin derivatives were closely related to the DS, the number of phenolic hydroxyl groups and their substitutive positions. The products described in this paper have great potential as biomaterials with good bioactivity and biocompatibility.

Three new phenolic glycosides from the roots of Lysidice rhodostegia

One new coumarin glycoside, lysidiforin A (1), and two new phloroglucinol glycosides, lysidiforin B–C (2 and 3), along with six known compounds (4–9) were isolated from the roots of Lysidice rhodostegia. The structures of compounds 1–3 were elucidated by the interpretation of extensive spectroscopic analyses (1D and 2D NMR, ESI-MS and HR-ESI-MS). All of the isolated compounds were evaluated regarding their antioxidant activities with a DPPH radical scavenging bioassay. Compounds 6–9 exhibited weak activities. The observed antioxidant activities of compounds 6–9 may be related to the number of phenolic hydroxyl groups.

Interaction Mechanism of Flavonoids and α-Glucosidase: Experimental and Molecular Modelling Studies.

Flavonoids are known to play a role in hypoglycemia by inhibiting α-glucosidase. However, their interaction mechanism with α-glucosidase still needs to be elaborated. In this study, the α-glucosidase inhibitory activities of 15 flavonoids were investigated. Their molecular volume had a negative effect on inhibitory activity, while the number of phenolic hydroxyl groups on the B ring was positively correlated with inhibitory activity. To explain the significant differences in activity, the interaction behaviors of myricetin and dihydromyricetin, which have similar structures, were compared by spectrofluorimetry, molecular docking, and the independent gradient model (IGM). In the fluorescence analysis, myricetin exhibited a higher binding capacity. Based on molecular docking and IGM analysis, their non-covalent interactions with α-glucosidase could be visualized and quantified. It was found that they had different binding modes with the enzymes and that myricetin possessed stronger hydrogen bonding and van der Waals force interactions, which explained the thermodynamic results.

Mechanism and Effects of Polyphenol Derivatives for Modifying Collagen

This study is aimed to investigate the relationship of the mechanism and the effect of polyphenol derivatives cross-linking collagen with polyphenol molecular structural complexity and reaction conditions of polyphenols with collagen and to present a reference for cross-linker selection. Three kinds of polyphenols were selected to cross-link collagen under nonoxidized and oxidized conditions in vitro. These polyphenols included tannic acid, which represents the most complex stereo structure and the highest number of phenolic hydroxyl groups; epigallocatechin gallate, which represents a moderately complex structure and contains fewer phenolic hydroxyl groups than tannic acid; and N-2-(3,4-dihydroxylphenyl) ethyl acrylamide, which represents only one hydroxyl phenol group. Particle size analysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, attenuated total reflection Fourier transform infrared spectroscopy, and cross-linking degree analysis were conducted. Mechanical properties, thermal stability, swelling properties, hydrophilicity, and antienzymolysis properties were also determined. Results showed that all polyphenol derivatives cross-linked collagen mainly by noncovalent bonding under acidic nonoxidized conditions and by covalent bonding under alkaline-oxidized conditions. In general, the modification effect of polyphenol on collagen was related to its molecular complexity and the number of its phenolic hydroxyls. Several phenolic hydroxyls in the polyphenol derivative caused a good modification effect on collagen, especially under acidic nonoxidized conditions. Under alkaline conditions, each polyphenol was oxidized, resulting in improved cross-linking strength by covalent bonding compared to that under acidic nonoxidized condition via noncovalent bonding. The selection of cross-linkers and cross-linking conditions should be based on the purpose of collagen modification consistent with the effect of cross-linking.

A Bioinspired Functionalization of Polypropylene Separator for Lithium-Sulfur Battery.

Lithium-sulfur batteries have received intensive attention, due to their high specific capacity, but the shuttle effect of soluble polysulfide results in a decrease in capacity. In response to this issue, we develop a novel tannic acid and Au nanoparticle functionalized separator. The tannic acid and gold nanoparticles were modified onto commercial polypropylene separator through a two-step solution process. Due to a large number of phenolic hydroxyl groups contained in the modified layer and the strong polarity of the gold nanoparticles, the soluble polysulfide generated during battery cycling is well stabilized on the cathode side, slowing down the capacity fade brought by the shuttle effect. In addition, the modification effectively improves the electrolyte affinity of the separator. As a result of these benefits, the novel separator exhibits improved battery performance compared to the pristine polypropylene separator.

Antiviral Activity of Phenolic Derivatives in Pyroligneous Acid from Hardwood, Softwood, and Bamboo

Pyroligneous acids (PA) from hardwood, softwood, and bamboo significantly disinfected encephalomyocarditis virus (EMCV). Twenty-five kinds of phenolic derivatives in the PAs were identified and quantified. The total amounts of phenolic compounds in bamboo PA is higher than those in the PAs from softwood and hardwood. Phenol, 2-methoxyphenol, 2-methoxy-4-methylphenol, and 2-methoxy-4-ethylphenol are the most abundant compounds in the PAs examined. The activities of all the phenolic compounds against the encephalomyocarditis virus were assessed. The number of phenolic hydroxyl groups significantly affects the antiviral activity, and catechol and its derivatives exhibit higher viral inhibition effects than other phenolic derivatives. In addition, substituents affect the antiviral activity of the compounds. Phenolic compounds with a methyl group show higher activities than with a methoxyl group (e.g., 2-methylphenol > 2-methoxyphenol). Moreover, the relative position of functional groups also plays a key role...

Characterization of binding interactions between selected phenylpropanoid glycosides and trypsin

Phenylpropanoid glycosides (PPGs) are important bioactive polyphenolic compounds that are widely distributed in plants. In this paper, the inhibitory effects of four selected PPGs against trypsin were investigated. The interactions between these PPGs and trypsin were further investigated by multiple spectroscopic methods and molecular docking studies. The results showed that the binding of each of these PPGs to trypsin induced changes in the natural conformation of trypsin, which inhibited the enzyme in the following order: acteoside>syringalide A 3′-α-l-rhamnopyranoside>lipedoside A-I>osmanthuside B. The binding constant (Ka) values followed the same trend. The hydrogen bond force played an important role in the interaction between each PPG and trypsin. Interestingly, the binding affinity and inhibitory effect increased as the number of phenolic hydroxyl groups increased. In addition, the effect of the phenolic hydroxyl group on the A ring had a greater effect than one on the B ring.

Anti-HSV-1, antioxidant and antifouling phenolic compounds from the deep-sea-derived fungus Aspergillus versicolor SCSIO 41502

Chemical investigation of the deep-sea-derived fungus Aspergillus versicolor SCSIO 41502 resulted in the isolation of three new anthraquinones, aspergilols G-I (1–3), one new diphenyl ether, 4-carbglyceryl-3,3′-dihydroxy-5,5′-dimethyldiphenyl ether (4), and one new benzaldehyde derivative, 2,4-dihydroxy-6-(4-methoxy-2-oxopentyl)-3-methylbenzaldehyde (5), along with 23 known phenolic compounds (6–28). The structures of new compounds were elucidated by extensive spectroscopic analysis. The absolute configuration of 3 was established by CD spectrum and the modified Mosher method. Compounds 2, 3 and 9 had evident antiviral activity towards HSV-1 with EC50 values of 4.68, 6.25, and 3.12μM, respectively. Compounds 15, 18, 20 and 22–24 showed more potent antioxidant activity than l-ascorbic acid with IC50 values of 18.92–52.27μM towards DPPH radicals. Comparison of the structures and antioxidant activities of 1–28 suggests that the number of phenolic hydroxyl group that can freely rotate can significantly affect the antioxidant activity of phenolic compounds. In addition, 4, 22–24 and 27 had significant antifouling activity against Bugula neritina larval settlement with EC50 values of 1.28, 2.61, 5.48, 1.59, and 3.40μg/ml, respectively.

Role of 3,5-Digalloyl and 3’,4’-Dihydroxyl Structure of (–)-Epicatechin- 3,5-Digallate in Inhibition of Hela S3 Cell Proliferation

Flavan-3-ol derivatives are common plant-derived bioactive compounds with strong various biological activities. In particular, (–)-epigallocatechin-3-O-gallate exhibits a variety of moderate biological activities without severe toxicity. Its health-promoting effects have been widely studied because it is a main ingredient in green tea and is commercially available at low cost. In general, the galloyl moieties of flavan-3-ol derivatives are thought to be essential to their strong biological activities. However, it is not clear which position is most effective for modification with the galloyl moiety to strengthen the biological activities because various galloylated analogs are difficult to obtain in pure form in a quantity large enough for assays. Therefore, we synthesized various galloylated flavan-3-ol derivatives in a stereoselective and regioselective manner. We reported in a previous paper that 3,5-digalloyl-(–)-epicatechin displayed much stronger inhibitory activity than 3,5-digalloyl-(+)-catechin did against HeLa S3 cell proliferation. In this study, we describe synthetic studies of 7-galloyl- and 3,7-digalloyl-modified (–)-epicatechin and (+)-catechin and compared their biological activities, HeLa S3 cell proliferation inhibitory activity and DPPH radical scavenging activity with those of 3,5- digalloyl- (–)-epicatechin. The results indicated that 3,7-digalloyl derivative did not inhibit HeLa S3 cell proliferation. Furthermore, 3,5-digalloyl- (–)-epigallocatechin was synthesized to evaluate the importance of the number of phenolic hydroxyl groups on the B-ring. Contrary to our expectations, 3,5-digalloyl-(–)-epigallocatechin exhibited a weaker inhibition of HeLa S3 cell proliferation than 3,5-digalloyl- (–)-epicatechin did. The DPPH radical scavenging activity of the synthesized compounds suggested that the galloyl-modified position and the number of phenolic hydroxyl groups on B-ring affected to the radical scavenging ability. In conclusion, we found that 3,5-digalloyl-(–)-epicatechin exhibited a superlative HeLa S3 cell proliferation inhibitory effect among the galloylated flavan-3-ol derivatives we synthesized and DPPH radical scavenging activity was affected by the galloyl-moiety-introduced position and the number of phenolic hydroxyl groups on the B-ring.

Substituent Effect of Phenolic Aldehyde Inhibition on Alcoholic Fermentation by Saccharomyces cerevisiae

Phenolic compounds significantly inhibit microbial fermentation of biomass hydrolysates. To understand the quantitative structure–inhibition relationship of phenolic aldehydes on alcoholic fermentation, the effect of 11 different substituted benzaldehydes on the final ethanol yield was examined. The results showed that the degree of phenolic benzaldehyde inhibition was strongly associated with the position of phenolic hydroxyl groups but not the number of phenolic hydroxyl groups. It was observed that ortho-substituted 2-hydroxybenzaldehyde resulted in 15–20-fold higher inhibition than the meta- or para-substituted analogues of 3- and 4-hydroxybenzaldehydes. From the correlation of the molecular descriptors to inhibition potency in yeast fermentation, we found a strong relationship between the octanol/water partition coefficient (log P) of aldehydes and the EC50 value. The most inhibitory 2-hydroxybenzaldehyde has the highest log P and possesses an ortho −OH group capable of forming an intramolecular hydr...

Behavior investigation of phenolic hydroxyl groups during the pyrolysis of cured phenolic resin via molecular dynamics simulation

In this paper, the initial stage of the pyrolysis process of phenolic resin has been simulated by ReaxFF (reactive force field) molecular dynamics simulation under various temperatures (3000 K, 3250 K, and 3500 K), to study the behavior of phenolic hydroxyl groups and to investigate the correlation between the production of small oxygen-containing molecules (including H2O, CO and CO2) and the quantity of hydroxyl radicals at different temperatures. We observed that the highly active phenolic hydroxyl groups would be easily turned into phenoxyl radicals and hydroxyl radicals in primary evolution. And also, both the phenoxyl radicals and hydroxyl radicals had remarkable impact on the following process of pyrolysis in secondary evolution: the formation of phenoxyl radicals reduced the stability of the benzene ring and damaged backbone of phenolic resin accompanying with the release of CO molecules, while the hydroxyl radicals increased the amount of CO molecules and converted them into CO2 molecules, to reduce the char yield of resin. We found that the amounts of small oxygen-containing molecules increased with the rise in the number of phenolic hydroxyl groups or the rise in the temperature. We also found that both the two evolution modes of phenolic hydroxyl groups (I. phenolic hydroxyl groups – phenoxyl radicals – small oxygen-containing molecules; II. phenolic hydroxyl groups – hydroxyl radicals – small oxygen-containing molecules) can reduce the thermal stability of the backbone of resin. The negative effect of phenolic hydroxyl groups on the thermal stability of cured PR is valuable to the understanding of the pyrolytic process and char forming mechanism, and also the enhancement of the thermal stability of resin.

Structure-Activity Relationship of Oligomeric Flavan-3-ols: Importance of the Upper-Unit B-ring Hydroxyl Groups in the Dimeric Structure for Strong Activities.

Proanthocyanidins, which are composed of oligomeric flavan-3-ol units, are contained in various foodstuffs (e.g., fruits, vegetables, and drinks) and are strongly biologically active compounds. We investigated which element of the proanthocyanidin structure is primarily responsible for this functionality. In this study, we elucidate the importance of the upper-unit of 4–8 condensed dimeric flavan-3-ols for antimicrobial activity against Saccharomyces cerevisiae (S. cerevisiae) and cervical epithelioid carcinoma cell line HeLa S3 proliferation inhibitory activity. To clarify the important constituent unit of proanthocyanidin, we synthesized four dimeric compounds, (−)-epigallocatechin-[4,8]-(+)-catechin, (−)-epigallocatechin-[4,8]-(−)-epigallocatechin, (−)-epigallocatechin-[4,8]-(−)-epigallocatechin-3-O-gallate, and (+)-catechin-[4,8]-(−)-epigallocatechin and performed structure–activity relationship (SAR) studies. In addition to antimicrobial activity against S. cerevisiae and proliferation inhibitory activity on HeLa S3 cells, the correlation of 2,2-diphenyl-l-picrylhydrazyl radical scavenging activity with the number of phenolic hydroxyl groups was low. On the basis of the results of our SAR studies, we concluded that B-ring hydroxyl groups of the upper-unit of the dimer are crucially important for strong and effective activity.

Softwood kraft lignin for value-added applications: Fractionation and structural characterization

This study focuses on a systematic, structural characterization of lignin samples fractionated from softwood industrial black liquor (BL). In addition to the isolation efficiency, the impact of fractionation and pulping severity on lignin structure was studied. BL samples from different chemical pulping stages were collected and the lignin was fractionated by sequential precipitation. While the alteration in structure and properties of the samples recovered from different delignification stages was only marginal, the spectroscopic characterization of the isolated lignin revealed significant alteration in its structure and functionalities as a function of the pH. Lignin samples precipitated at pH 10.5 exhibited the highest purity, as indicated by them having the lowest content of polysaccharides. In contrast, the samples precipitated at a pH of 2.5 revealed the highest carbohydrate content, rising from 9.7% at the beginning of cooking, to 36.8% at the end. At the same time, these lignin samples had the lowest Mw and the highest number of phenolic hydroxyl groups. Based on spectroscopic analysis, low Mw kraft lignin displayed an unusually high carboxyl content and a low methoxyl group content. All of the kraft lignin samples showed a reduction in the number of primary and secondary OH groups, which continuously decreased over the course of pulping. An opposite trend was observed with decreasing precipitation pH.

Exploitation of tannins to modulate rumen ecosystem and ruminants performance: A review

Tannins are polyphenolic polymers of relatively high molecular weight with the capacity to form complexes mainly with proteins due to the presence of a large number of phenolic hydroxyl groups. They are widely distributed in nutritionally important forage trees, shrubs and legumes, cereals and grains, which are considered as anti-nutritional compounds due to their adverse effects on intake and animal performance. However, tannins modulate rumen fermentation favorably such as reducing protein degradation in the rumen, prevention of bloat, inhibition of methanogenesis and increasing conjugated linoleic acid concentrations in ruminant-derived foods. The inclusion of tannins in diets has been shown to improve body weight and wool growth, milk yields and reproductive performance. This review discusses the effects of tannins on nutrient metabolism, rumen fermentation, and microbial populations bacteria, protozoa, fungi and archaea), metabolism of tannins, microbial tolerance mechanisms to tannins, inhibition of methanogenesis, and performance of animals. This review seeks to highlight the practical significance of tannins on ruminant nutrition in developing countries. It will also review approaches to counter the negative effects of tannins.