Methylation and 2D NMR analysis of arabinoxylan from the seeds of Plantago asiatica L

Structural characteristics of sulfated xylogalactomannan isolated from Caulerpa okamurae and its anticoagulant activity

Due to wonderful taste, rich nutrition and biological functions, many marine green algae in the genus Caulerpa have been recently developed as candidates for green caviar. A novel water-soluble sulfated xylogalactomannan CO-0-1 was obtained from the green algae Caulerpa okamurae. CO-0-1 was mainly composed of mannose (Man), galactose (Gal), and xylose (Xyl) at the ratio of 4.4:4.0:1.4 with the molecular weight at 470 kDa and the sulfate content at 12.78 %. The sulfated xylogalactomannan had Man at the backbone with →4)-β-D-Manp-(1→ and →2)-β-D-Manp-(1→ as the main chain and branches at O-3 position. The side chains contained →3)-β-D-Galp-(1→ and minor →2)-β-D-Xylp(1→. The sulfate groups only distributed at the side chains and at O-6 position of →3)-β-D-Galp-(1→ and O-4 position of (1→2)-β-D-Xylp. The anticoagulant activity indicated that CO-0-1 displayed intrinsic anticoagulant and specific anti-thrombin activities. The investigation expanded the utilization and development scene and scope of the green algae Caulerpa okamurae.

Structural and rheological characterization of water-soluble and alkaline-soluble fibers from hulless barley

BACKGROUND

Highland hulless barley has garnered attention as a promising economic product and a potential healthy food ingredient. The present study aimed to comprehensively investigate the molecular structure of extractable fibers obtained from a specific highland hulless barley. Water-soluble fiber (WSF) and alkaline-soluble fiber (ASF) were extracted using enzymatic digestion and an alkaline method, respectively. The purified fibers underwent a thorough investigation for their structural characterization.

RESULTS

The monosaccharide composition revealed that WSF primarily consisted of glucose (91.7%), whereas ASF was composed of arabinose (54.5%) and xylose (45.5%), indicating the presence of an arabinoxylan molecule with an A/X ratio of 1.2. The refined structural information was further confirmed through methylation, 1 H NMR and Fourier-transform infrared spectroscopy analyses. WSF fiber exclusively exhibited α-anomeric patterns, suggesting it was an α-glucan. It has a low molecular weight of 5 kDa, as determined by gel permeation chromatography. Conversely, ASF was identified as a heavily branched arabinoxylan with 41.55% of '→2,3,4)-Xylp-(1→' linkages. ASF and WSF exhibited notable differences in their morphology, water absorption capabilities and rheological properties.

CONCLUSION

Based on these findings, molecular models of WSF and ASF were proposed. The deep characterization of these fiber structures provides valuable insights into their physicochemical and functional properties, thereby unlocking their potential applications in the food industry. © 2023 Society of Chemical Industry.

Structure and properties of acidic polysaccharides isolated from Massa Medicata Fermentata: Neuroprotective and antioxidant activity

Massa Medicata Fermentata (MMF) is a fermented food with therapeutic effects. Previous studies suggested that after stir-frying, the uronic acid content in MMF crude polysaccharides increases, and the pH value decreases, which is caused by the change in acidic polysaccharides. However, the detailed physicochemical properties and structure-activity correlation of the acidic polysaccharides in MMF have not been fully explored. In this study, two acidic polysaccharides (SMMFAP and CMMFAP) were isolated from the MMF and its stir-fried product, respectively. Their structural characteristics and bioactivities were comparatively studied, and the structure-activity correlation was examined. Our findings revealed that the SMMFAP had a higher average Mw and higher Gal and Man content than the CMMFAP. Both the SMMFAP and CMMFAP were mainly composed of Xyl, Man, and Gal residues, whereas the CMMFAP had fewer linkage types. Additionally, the CMMFAP exhibited stronger neuroprotective activity than the SMMFAP owing to its higher content of 1,6-linked-Galp, while the SMMFAP exhibited better antioxidant activity, which might be related to its higher average Mw. Our findings suggest that acidic polysaccharides may be the active substances that cause differences in effectiveness between the sheng and chao MMF. Furthermore, the research qualified the SMMFAP and CMMFAP with different potential applications.

Water-extractable polysaccharide fraction PNE-P1 from Pinus koraiensis pine nut: Structural features and immunostimulatory activity

The polysaccharide fraction PNE-P1 was isolated from hot water extract (PNE) of the defatted meal of pine nuts (Pinus koraiensis) using DEAE-cellulose column chromatography. This fraction had three components of molecular masses 1251, 616, and 303 g/mol consisting mainly of arabinose, xylose, and galacturonic acid at a molar ratio of 2:1.6:1. Structural analysis with FTIR/Raman, methylation and GC-MS, and NMR revealed that PNE-P1 is a cell wall polysaccharide complex including arabinan, heteroxylan, homogalacturonan (HM) and rhamnogalacturonan I (RG-I) parts. Being nontoxic to RAW 264.7 macrophages in the concentration range of 10-200 μg/mL, PNE-P1 promoted proliferation of these cells, significantly induced the secretion of proinflammatory cytokines (TNF-α and IL-6) and chemokines (RANTES and MIP-1α) and enhanced the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) and nitric oxide (NO). PNE-P1 also markedly induced macrophage-mediated phagocytosis of apoptotic Jurkat T cells. These results demonstrate that pine nuts Pinus koraiensis contain a complex of water-soluble plant cell wall polysaccharides, which can stimulate innate immunity by potentiating macrophage function.

Structural characterization of corn fiber hemicelluloses extracted by organic solvent and screening of degradation enzymes

An integrated treatment coupling peracetic acid delignification, dimethyl sulfoxide extraction, and ethanol precipitation were performed to isolate hemicellulose from de-starched corn fiber. Based on chemical composition, molecular weight distribution, methylation, and nuclear magnetic resonance spectroscopy, it is proposed that hemicelluloses in corn fiber were composed of two polysaccharides, glucuronoarabinoxylan (about 80 %) and xyloglucan (about 20 %). Xylose (about 46 %) and arabinose (about 32 %) were the main components in glucuronoarabinoxylan. More than half of the xylose units in the glucuronoarabinoxylan backbone chain were substituted at O-2 and/or O-3 by various monomers or oligomeric side chains. Based on structure analysis, five hemicellulases were selected and added to Penicillium oxalicum MCAX enzymes for enzymatic hydrolysis of corn fiber. The results showed that the addition of hemicellulases increased the sugar yield of corn fiber. These results demonstrate the effectiveness of enzyme consortium constructed by elucidating the chemical structure of hemicellulose in corn fiber for the degradation of corn fiber and also provide a general solution for the rational construction of targeted and efficient enzyme systems for the degradation of lignocellulosic biomass.

Phytochemicals, Biological Activities, Molecular Mechanisms, and Future Prospects of Plantago asiatica L

Plantago asiatica L. has been used as a vegetable and nutritious food in Asia for thousands of years. According to recent phytochemical and pharmacological research, the active compositions of the plant contribute to various health benefits, such as antioxidant, anti-inflammatory, antibacterial, antiviral, and anticancer. This article reviews the 87 components of the plant and their structures, as well as their biological activities and molecular research progress, in detail. This review provides valuable reference material for further study, production, and application of P. asiatica, as well as its components in functional foods and therapeutic agents.

Outstanding questions on xylan biosynthesis

Xylan is the second most abundant polysaccharide in plant biomass. It is a crucial component of cell wall structure as well as a significant factor contributing to biomass recalcitrance. Xylan consists of a linear chain of β-1,4-linked xylosyl residues that are often substituted with glycosyl side chains, such as glucuronosyl/methylglucuronosyl and arabinofuranosyl residues, and acetylated at O-2 and/or O-3. Xylan from gymnosperms and dicots contains a unique reducing end tetrasaccharide sequence that is not detected in xylan from grasses, bryophytes and seedless vascular plants. Grass xylan is heavily decorated at O-3 with arabinofuranosyl residues that are frequently esterified with hydroxycinnamates. Genetic and biochemical studies have uncovered a number of genes involved in xylan backbone elongation and acetylation, xylan glycosyl substitutions and their modifications, and the synthesis of the unique xylan reducing end tetrasaccharide sequence, but some outstanding issues on the biosynthesis of xylan still remain unanswered. Here, we provide a brief overview of xylan structure and focus on discussion of the current understanding and open questions on xylan biosynthesis. Further elucidation of the biochemical mechanisms underlying xylan biosynthesis will not only shed new insights into cell wall biology but also provide molecular tools for genetic modification of biomass composition tailored for diverse end uses.

Structural characterization of novel arabinoxylan and galactoarabinan from citron with potential antitumor and immunostimulatory activities

This study aimed to extract polysaccharides from citron and analyze their structures and potential bioactivities. Two novel polysaccharides CM-1 and CM-2 were purified from citron by DEAE-Sepharose Fast Flow and Sephadex G-100 column chromatography. Monosaccharide composition, linkage and NMR data were used to infer their sugar chains composition. The anti-breast cancer cells and immunoregulatory activities of CM-1 and CM-2 were investigated. Results indicated that CM-1 (Mw = 21,520 Da), composed of arabinose, xylose, mannose and glucose in a molar ratio of 10.78:11.53:1.00:1.70, was arabinoxylan (AX) with (1 → 4)-linked β-d-Xylp skeleton monosubstituted with α-l-Araf units at O-3 position. While CM-2 (Mw = 22,303 Da), composed of arabinose, mannose, glucose and galactose in a molar ratio of 25.46:1.45:1.00:6.57, was galactoarabinan (GA) with (1 → 5)-linked α-l-Araf backbone substituted by β-d-Galp units at O-2 and/or O-3 positions. Both polysaccharides exhibited potential inhibiting cancer and immunostimulatory activities in vitro, especially CM-1. These results provide a basis for further research on citron polysaccharides.

TEMPO/NaClO2/NaOCl oxidation of arabinoxylans

TEMPO-oxidation of neutral polysaccharides has been used to obtain polyuronides displaying improved functional properties. Although arabinoxylans (AX) from different sources may yield polyuronides with diverse properties due to their variable arabinose (Araf) substitution patterns, information of the TEMPO-oxidation of AX on its structure remains scarce. We oxidized AX using various TEMPO:NaClO₂:NaOCl ratios. A TEMPO:NaClO₂:NaOCl ratio of 1.0:2.6:0.4 per mol of Ara gave an oxidized-AX with high molecular weight, minimal effect on xylose appearance, and comprising charged side chains. Although NMR analyses unveiled arabinuronic acid (AraAf) as the only oxidation product in the oxidized-AX, accurate AraA quantification is still challenging. Linkage analysis showed that > 75 % of the β-(1→4)-xylan backbone remained single-substituted at position O-3 of Xyl similarly to native AX. TEMPO-oxidation of AX can be considered a promising approach to obtain arabinuronoxylans with a substitution pattern resembling its parental AX.

A review of NMR analysis in polysaccharide structure and conformation: Progress, challenge and perspective

Nuclear magnetic resonance (NMR) has been widely used as an analytical chemistry technique to investigate the molecular structure and conformation of polysaccharides. Combined with 1D spectra, chemical shifts and coupling constants in both homo- and heteronuclear 2D NMR spectra are able to infer the linkage and sequence of sugar residues. Besides, NMR has also been applied in conformation, quantitative analysis, cell wall in situ, degradation, polysaccharide mixture interaction analysis, as well as carbohydrates impurities profiling. This review summarizes the principle and development of NMR in polysaccharides analysis, and provides NMR spectra data collections of some common polysaccharides. It will help to promote the application of NMR in complex polysaccharides of biochemical interest, and provide valuable information on commercial polysaccharide products.

Structural characteristics and rheological properties of alkali-extracted arabinoxylan from dehulled barley kernel

Arabinoxylan (BIF-60) was isolated from barley water-insoluble fiber (BIF) by ethanol precipitation at 60 % (v/v). BIF-60 was composed of xylose (48.5 %) and arabinose (30.3 %). Its average molecular weight was 1360 kDa. Methylation and 1D/2D NMR analysis showed that BIF-60 possessed β-(l→4)-xylan as backbone, comprised of un-substituted (1,4-linked β-Xylp, 56.9 %), mono-substituted (1,2,4-linked and 1,3,4-linked β-Xylp, 22.1 %) and di-substituted (1,2,3,4-lin4ked β-Xylp, 18.4 %) xylose units, as well as other residues (T-Araf-(1→, T-Xylp-(1→, →5)-Araf-(1→, →2)-Araf-(1→, →3)-Araf-(1→ and →4)-Glcp-(1→). BIF-60 exhibited shear-thinning behaviour, low gel stability and weak gelling ability at high concentrations. This work provides a theoretical and experimental basis for molecular structure and properties of the alkali-extracted arabinoxylan from barley kernel, which could guide further functional research and application of barley-derived arabinoxylan.

Structural features, selenization modification, antioxidant and anti-tumor effects of polysaccharides from alfalfa roots

Hot water extraction and chromatographic purification methods were used to extract and purify two polysaccharides (RAPS-1 and RAPS-2) from the roots of alfalfa. Subsequently, RAPS-2 was modified using the HNO₃/Na₂SeO₃ method to obtain Se-RAPS-2. The structural features, antioxidant and in vitro anti-tumor activities of the three polysaccharides were evaluated. The structural analysis revealed that RAPS-1 (Mw = 10.0 kDa) was composed of rhamnose, xylose, arabinose, galacturonic acid, mannose and glucose, whereas RAPS-2 (Mw = 15.8 kDa) consisted of rhamnose, xylose, galacturonic acid, mannose, glucose and galactose. RAPS-1 contained 1 → 2, 1 → 4, 1 → 3, and 1 → 6 or 1 → glycosidic bonds; however, while RAPS-2 lacked 1 → 4 glycosidic linkages. The molecular weight of Se-RAPS-2 was 11.0 kDa less than that of RAPS-2. The results of activities demonstrated that Se-RAPS-2 displayed superior antioxidant activity and inhibitory effect in HepG2 cells than RAPS-1 and RAPS-2.

Chemical characterization and immunostimulatory activity of phenolic acid bound arabinoxylans derived from foxtail and barnyard millets

The chemical characterization and evaluation of immunostimulating effect of phenolic acid bound arabinoxylan (PA-AXs) isolated from barnyard (PA-AX-B) and foxtail (PA-AX-F) millets were performed. The sugar composition analysis and bound phenolic acids' (caffeic acid, p-coumaric acid, and ferulic acid) content of PA-AXs were examined by gas chromatography and mass spectroscopy (GC-MS) and high performance liquid chromatography (HPLC), respectively. The immunostimulatory activity of PA-AXs was evaluated by studying the effect of PA-AXs on the release of nitric oxide (NO), ROS, and cytokine (TNF-α, IL-1β, and IL-6) in RAW 264.7 murine macrophage cells. The GC-MS results revealed the xylose: arabinose ratio of PA-AX-F and PA-AX-B as 1.96:1.0 and 1.64:1.0, respectively. In HPLC analysis, PA-AX-B showed higher phenolic acid content than PA-AX-F. In RAW 264.7 cells, immunostimulatory activity was established by its increased release of NO, ROS, and cytokine (TNF-α, IL-1β, and IL-6) in a dose-dependent manner. Both PA-AX-B and PA-AX-F exhibited significant immunostimulation in in vitro studies. PRACTICAL APPLICATIONS: Millets are known for the higher content of phenolic acid bound arabinoxylans (PA-AX). The composition of PA-AX varies with different types of millets. In general, rice bran and wheat arabinoxylans are well reported to have significant immunostimulatory and antitumor properties. The bound ferulic acid with arabinoxylan isolated from finger millet bran also possesses immunostimulatory property. As the millets grains, foxtail and barnyard are also rich in PA-AXs, the present study was focused to evaluate the immunostimulatory property of PA-AX derived from two different millets. The study results indicated the immune stimulatory action of millet PA-AX's and thus the purified PA-AX can be explored further to identify the mechanism of action with respect to its immune stimulation property.

Structural characterisation and immunomodulatory activity of a neutral polysaccharide from Sambucus adnata Wall

A neutral polysaccharide, SPW-2, was purified from the leaves of Sambucus adnata Wall. using water extraction and alcohol precipitation, Sevage deproteination, ion exchange chromatography and gel filtration chromatography. This molecule had an average molecular weight of 7040 Da and was composed of arabinose, xylose, mannose, glucose and galactose at a molar ratio of 1.5:0.5:1.2:5.0:1.8. The repetitive structural units of SPW-2 were deduced using methylation analysis and nuclear magnetic resonance (one- and two-dimensional) spectroscopy. In vitro immunological activity test showed that SPW-2 could induce the secretion of nitric oxide, interleukin-1β (IL-1β), IL-6 and tumour necrosis factor-alpha (TNF-α), and increase the mRNA expression level of inducible nitric oxide synthase (iNOS), IL-1β, IL-6 and TNF-α in macrophages. The data supported the notion that SPW-2 exerts an immunomodulatory effect by activating macrophages and enhancing the host immune system function, which enabled it to be used as a novel immunomodulator for application in the treatment of immunological diseases.

Structural features and rheological behavior of a water-soluble polysaccharide extracted from the seeds of Plantago ciliata Desf

A water-soluble polysaccharide (PSPC) was extracted from the seeds of Plantago ciliata Desf., a spontaneous Algerian Saharan plant by a hot aqueous extraction then purified by successive ethanolic precipitations. The final extraction yield for PSPC was close to 18.6% (w/v). PSPC was then investigated regarding its global composition, structural features and rheological properties. PSPC is a neutral arabinoxylan, composed of a β-(1,3)/β-(1,4)-d-xylan backbone with side chains of Xylp, and Araf residues attached in O-2 and O-3 positions. The macromolecular characteristics of PSPC in water was determined by SEC/MALLS, with a high molecular weight (Mw) of 700 kDa, a low polydispersity index (PDI) of 1.47 and an intrinsic viscosity [η] close to 157 mL/g. PSPC showed a pseudoplastic behavior in semi-dilute media and the critical overlay concentration (C*) was estimated around 0.32-0.37% (w/v). This current research has supplied original structural information on a new arabinoxylan which could be particularly useful as a novel source of soluble fiber belonging to psyllium.

Modified soybean meal polysaccharide with high adhesion capacity to Salmonella

Carbohydrates are known to act as analog receptors for bacteria and therefore are promising alternatives for the control and prevention of bacterial infections. The present study evaluated the chemical structure of modified soybean meal polysaccharides and their capacity to adhere enterobacteria (Salmonella Typhimurium) and to interfere with the bacteria adhesion to the known analogue receptors, using in vitro assays. For this, soybean meal suspensions were subjected to a thermochemical extraction process and structural analyses showed that the fraction with higher adhesion and adhesion-inhibition potential, SAP, was constituted by two types of polysaccharides: a partially depolymerized pectin, of high molar mass, composed of xylogalacturonan and rhamnogalacturonan regions (SAP1, 545.5 kDa), and a (1 → 4)-linked-β-D-galactan of low molar mass (SAP2, 8.7 kDa). The results showed a high affinity of Salmonella for galactans, while high molar mass pectins showed no adhesion capacity. The chemical compositions of the fractions suggested that galactose could be responsible for the recognition process in the adhesion process. Other factors, such as structure and degree of polymerization of the polymers, may also be influencing the adhesion process. Modified soybean meal polysaccharides appear to be a promising alternative agent to antibiotics for the control and prevention of foodborne diseases.

Chemical structure and rheological studies of arabinoglucuronoxylans from the Cercidium praecox exudate brea gum

The structure of the arabinoglucuronoxylans from brea gum was elucidated through an chemical and NMR spectroscopical analysis. They are composed of xylose, arabinose, glucuronic acid and 4-O-methylglucuronic acid in a molar ratio 1:0.44:0.16:0.22. The structure consists of a central chain of (1→4)-β-d-xylopyranose of which ca.70% are susbstituted in C2 with single stubs of others sugars (β-d-Xylp, α-d-GlcpA and 4-O-Me-α-d-GlcpA), with disaccharides (α-l-Arap-(1→2)-4-O-Me-α-d-GlcpA-(1→, α-l-Arap-(1→2)-α-d-GlcpA-(1→, β-l-Araf-(1→3)-α-l-Araf-(1→ and α-l-Araf-(1→3)-α-l-Araf-(1→5), and possibly with trisaccharides of xylose. The determination of the location of the acetyl groups and their quantification in these arabinoglucuronoxylans has been achieved for the first time. Brea gum presents a higher thickening effect than gum arabic in 5% aqueous solution, demonstrating its potential usefulness for food and pharmaceutical applications.

Molecular properties and structural characterization of an alkaline extractable arabinoxylan from hull-less barley bran

An alkaline extractable arabinoxylan (HBAX-25) was fractionated from crude arabinoxylan (HBAX) obtained optimally in hull-less barley (Hordeum vulgare L. var. nudum Hook. f.) bran. Molecular properties and structural characterization of HBAX-25 were investigated thoroughly based on chemical composition of 8.31% (w/w) moisture and 87.57% (w/w) sugar with specifically few proteins (1.08%, w/w) and high arabinoxylans (82.46%, w/w). Data from monosaccharide composition indicated that HBAX-25 mainly consisted of arabinose (30.13 mol%) and xylose (51.55 mol%) with A/X ratio of 0.58, representative for arabinoxylans, which coincided with FT-IR results and was corroborated by methylation and NMR analyses, i.e., a relatively low-branched arabinoxylan composed of un-substituted (1,4-linked β-D-Xylp, 71.19%), mono-substituted (1,3,4-linked β-D-Xylp, 14.78%) and di-substituted (1,2,3,4-linked β-D-Xylp, 10.76%) xylose units as backbone via β-(1→4) linkages, with six possible branches or individuals included. Hence, a structural basis of HBAX-25 was established, which could have potential in food and other value-added applications capable of interpreting their physicochemical, functional and technological characteristics.

Structural analysis and antioxidant activity of an arabinoxylan from Malvastrum coromandelianum L. (Garcke)

The structure of MAP was studied by degradative, derivatization and spectroscopic methods, and it was found to be an arabinoxylan comprising a backbone of →4)-β-d-linked Xylp(1→ with branching at O-2 by →3)-α-l-Araf(1→ and →3)-β-d-Xylp(1→ chains.

Polysaccharide isolated from seeds of Plantago asiatica L. induces maturation of dendritic cells through MAPK and NF-κB pathway

Plantago species are used as traditional medicine in Asian and Europe. Polysaccharide isolated from the seeds of Plantago asiatica L. could stimulate maturation transformation of bone-marrow derived dendritic cells (DCs). We found that blocking p38, ERK1/2 and JNK MAPK signal transduction could significantly decreased the PLP-2 induced expression of MHC II, CD86 surface molecules on DCs. Blocking p38 and JNK signal also significantly inhibited the cytokine secretion of TNF-α and IL-12p70 as well, while blocking ERK1/2 signal only decreased the secretion of TNF-α. Meanwhile, DCs in the three MAPK signal-blocking groups showed dramatically attenuated effects on stimulating proliferation of T lymphocytes. Similarly, blocking signal transduction of NF-κB pathway also significantly impaired the phenotypic and functional maturation development of DCs induced by PLP-2. These data suggest that MAPK and NF-κB pathway mediates the PLP-induced maturation on DCs. Especially, among the three MAPK pathways, activation of JNK signal transduction is the most important for DCs development after PLP-2 incubation. And PLP-2 may activate the MAPK and NF-κB pathway by triggering toll-like receptor 4 on DCs.

A new heteropolysaccharide from the seed husks of Plantago asiatica L. with its thermal and antioxidant properties

A new heteropolysaccharide (PMH) with a molecular weight of 1.4 × 10³ kDa was isolated from the seed husks of Plantago asiatica L. The monosaccharide composition of PMH was determined as glucose, xylose, arabinose, rhamnose, galactose and galacturonic acid with a molar ratio of 1.0 : 1.8 : 2.4 : 3.8 : 4.9 : 8.5. The backbone of PMH consisted of 1,4-β-d-GalpA with the side chains mainly composed of 1,3-α-d-Galp and 1,2-α-d-Galp which were attached to the O-3 of GlapA. The thermal analysis using the Flynn-Wall-Ozawa (FWO) method revealed that PMH had an apparent activation energy (E_a) of 173.1 kJ mol^-1. PMH experienced a major decomposition during the heating process at a temperature of 91.1 °C with a dry weight loss of 31.1%. Moreover, PMH exhibited stronger antioxidant ability than commercial psyllium, partially due to its higher content of uronic acid. The results suggested that PMH could be used in functional foods due to its structural, thermal and antioxidant characteristics.

Polysaccharide from Plantago as a green corrosion inhibitor for carbon steel in 1M HCl solution

Polysaccharide from Plantago ovata was investigated for its inhibition characteristics for carbon steel corrosion in 1M HCl. The mucilage of the Plantago is comprised of a highly branched polysaccharide, arabinosyl (galaturonic acid) rhamnosylxylan (AX), which is mainly responsible for the corrosion inhibition of the carbon steel. The techniques that were used to assess the inhibition and adsorption properties of the AX in the acid solution are gravimetric method, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-vis spectroscopy and FTIR. Thermodynamic and activation parameters revealed that the spontaneous adsorption of AX on carbon steel was mixed type and predominantly chemical in nature. Quantum chemical analysis supports the proposed mechanism of inhibition. AX from Plantago could serve as a green corrosion inhibitor for the carbon steel in hydrochloric medium with good inhibition efficiency but low risk of environmental pollution.

Structural Features of Alkaline Extracted Polysaccharide from the Seeds of Plantago asiatica L. and Its Rheological Properties

Polysaccharide from the seeds of Plantago asiatica L. has many bioactivities, but few papers report on the structural and rheological characteristics of the alkaline extract. The alkaline extracted polysaccharide was prepared from seeds of P. asiatica L. and named herein as alkaline extracted polysaccharide from seeds of P. asiatica L. (PLAP). Its structural and rheological properties were characterized by monosaccharide composition, methylation, GC-MS and rheometry. PLAP, as an acidic arabinoxylan, was mainly composed of 1,2,4-linked Xylp and 1,3,4-linked Xylp residues. PLAP solution showed pseudoplastic behavior, and weak gelling properties at high concentration. Sodium and especially calcium ions played a significant role in increasing the apparent viscosity and gel strength.

Allelopathic Potential of Invasive Plantago virginica on Four Lawn Species

Plantago virginica L. has invaded many lawn ecosystems in the Eastern part of China. The invasion has incurred an economic cost to remove them. In order to prevent the invasion, it is critical to understand the invasive mechanisms of this species. However, few studies have been conducted on the allelopathic mechanisms of its invasion. In this study, we examined allelopathic effects of P. virginica on germination of seeds and growth of seedlings of four widely used lawn species. We found extensive allelopathic potential of P. virginica on other lawn species, which varied with species and developmental stage. While most effects of the extracts of P. virginica were inhibitory, some variables in some species were promoted by the addition of the extracts. The extracts of P. virginica significantly inhibited seed germination of Agrostis matsumurae. While the overall differences in seed germination rate of Poa annua were significant among treatments, difference between control and any of the treatments was not significant. The height of seedlings of A. matsumurae and Cynodon dactylon was significantly lower under the treatments of adding extracts of P. virginica. In contrast, growth of seedlings of Festuca elata and P. annua did not show significant differences among treatments. The root length of A. matsumurae, C. dactylon and P. annua was suppressed by the extracts of P. virginica whereas root length of F. elata was not affected. Aboveground biomass of A. matsumurae and F. elata was significantly higher than control, except for F. elata at the concentration of 50mg/mL, whereas aboveground biomass of C. dactylon and P. annua was reduced at higher concentrations of the extracts. Except for A. matsumurae, root biomass of the other three lawn species declined under the treatments with the extracts of P. virginica. Our results revealed that P. virginica had allelopathic potential on four lawn species and supported the theory of "novel weapons hypothesis". Invasion by P. virginica in lawn can be moderated by selecting those species that are not affected or promotionally affected by it.

Effect of calcium on solution and conformational characteristics of polysaccharide from seeds of Plantago asiatica L

Polysaccharide from seeds of Plantago asiatica L. is rich in calcium, which is important for keeping viscous and weak gelling properties of the polysaccharide. However, few studies reported effect of calcium on solution and conformational characteristics of the polysaccharide. In this study, polysaccharide was prepared from seeds of P. asiatica L. and named as PLCP. PLCP was treated with EDTA to remove calcium ion to get PLCP-E. PLCP and PLCP-E were characterized by Ubbelohde capillary viscometer, light scattering and HPSEC with refractive index, light scattering and viscometric detectors. The results showed that PLCP had much higher intrinsic viscosity, hydrodynamic radius (Rh), radius of gyration (Rg) and molecular weight than that of PLCP-E when measured in the same solvent. PLCP and PLCP-E were in random coil conformation in aqueous solutions according to light scattering and HPSEC measurements. HPSEC data showed PLCP-E had lower intrinsic viscosity than that of PLCP with the same molecular weight. Persistence length of Lp was 2.5nm for PLCP and 2.3nm for PLCP-E, respectively. In conclusion, PLCP exhibited higher intrinsic viscosity and molecular weight, and stiffer conformation than that of PLCP-E, which could explain the reason of higher viscosity of PLCP.

Carboxymethylation enhances the maturation-inducing activity in dendritic cells of polysaccharide from the seeds of Plantago asiatica L

Carboxymethylation is a well-known modification process for polysaccharides. To evaluate the biological availability of carboxymethyl, polysaccharide from the seeds of Plantago asiatica L. (PLCP) was carboxymethylated (CM-PLCP) and the immunomodulatory activities of five CM-PLCPs of gradient degree of substitution (DS) from 0.40 to 0.62 were determined on dendritic cells (DCs) in vitro. Compared with DCs treated with PLCP, DCs treated with CM-PLCP of DS0.50, DS0.55, DS0.62, as well as CD86 and CD80, expressed higher levels of MHCII, CD86 and CD80 surface molecules. In addition, the secretion of IL-12p70 and the mRNA of CCR7 and CXCR4 chemokines were increased, while the endocytosis activities were inhibited. Correspondingly, stronger mixed lymphocyte reactions were induced by the DCs treated with the CM-PLCPs. The results showed that carboxymethylation modification of relevant high DS can enhance the DC maturation-inducing function of PLCP, indicating the potential application of carboxymethylated polysaccharide as an immunotherapeutic adjuvant.

Discovery of diversity in xylan biosynthetic genes by transcriptional profiling of a heteroxylan containing mucilaginous tissue

The exact biochemical steps of xylan backbone synthesis remain elusive. In Arabidopsis, three non-redundant genes from two glycosyltransferase (GT) families, IRX9 and IRX14 from GT43 and IRX10 from GT47, are candidates for forming the xylan backbone. In other plants, evidence exists that different tissues express these three genes at widely different levels, which suggests that diversity in the makeup of the xylan synthase complex exists. Recently we have profiled the transcripts present in the developing mucilaginous tissue of psyllium (Plantago ovata Forsk). This tissue was found to have high expression levels of an IRX10 homolog, but very low levels of the two GT43 family members. This contrasts with recent wheat endosperm tissue profiling that found a relatively high abundance of the GT43 family members. We have performed an in-depth analysis of all GTs genes expressed in four developmental stages of the psyllium mucilagenous layer and in a single stage of the psyllium stem using RNA-Seq. This analysis revealed several IRX10 homologs, an expansion in GT61 (homologs of At3g18170/At3g18180), and several GTs from other GT families that are highly abundant and specifically expressed in the mucilaginous tissue. Our current hypothesis is that the four IRX10 genes present in the mucilagenous tissues have evolved to function without the GT43 genes. These four genes represent some of the most divergent IRX10 genes identified to date. Conversely, those present in the psyllium stem are very similar to those in other eudicots. This suggests these genes are under selective pressure, likely due to the synthesis of the various xylan structures present in mucilage that has a different biochemical role than that present in secondary walls. The numerous GT61 family members also show a wide sequence diversity and may be responsible for the larger number of side chain structures present in the psyllium mucilage.