Clarification of the structural features of Rhamnogalacturonan-I type polysaccharide purified from radish leaves.

Determining the structure of REPI, an immunostimulatory polysaccharide fraction from radish leaves, is an important health objective. Herein, we show that REP-I contains nine different monosaccharides, including GalA (22.2%), Gal (32.6%), Ara (27.5%), and Rha (10.2%) as main sugars. REP-I was also reacted with ß-glucosyl Yariv reagent (29.8%), suggesting the presence of the arabino-ß-3,6-galactan. Furthermore, methylated-product analysis revealed that REP-I contains 13 different glycosyl linkages, including 4-linked GalpA (21.0%), 2,4-linked Rhap (7.0%), 4-linked Galp (5.8%), 5-linked Araf (10.1%), and 3,6-linked Galp (7.9%), which are characteristic of RG-I. Microstructural information was obtained by sequential degradation using four linkage-specific glycosylases and ß-elimination, with fragments analyzed on the basis of sugar composition, methylation, and MS/MS spectra. The results show that the immunostimulatory activity of REP-I is possibly due to the structure of RG-I, which is composed of a main chain with repeating [→2)-Rhap-(1 â†’ 4)-GalpA-(1→] linkage units and three side-chains: a branched α(1 â†’ 5)arabinan, a ß(1 â†’ 4)galactan, and arabino-ß-3,6-galactan, which are branched at the C(O)4 position of each Rha residue in the REP-I main chain.

Dynamics of cell wall polysaccharides during the elongation growth of rye primary roots.

MAIN CONCLUSION: In cells of growing rye roots, xyloglucans and homogalacturonans demonstrate developmental stage specificity, while different xylans have tissue specificity. Mannans, arabinans and galactans are also detected within the protoplast. Mannans form films on sections of fresh material. The primary cell walls of plants represent supramolecular exocellular structures that are mainly composed of polysaccharides. Cell wall properties and architecture differ between species and across tissues within a species. We revised the distribution of cell wall polysaccharides and their dynamics during elongation growth and histogenesis in rye roots using nonfixed material and the spectrum of antibodies. Rye is a member of the Poaceae family and thus has so-called type II primary cell walls, which are supposed to be low in pectins and xyloglucans and instead have arabinoxylans and mixed-linkage glucans. However, rye cell walls at the earliest stages of cell development were enriched with the epitopes of xyloglucans and homogalacturonans. Mixed-linkage glucan, which is often considered an elongation growth-specific polysaccharide in plants with type II cell walls, did not display such dynamics in rye roots. The cessation of elongation growth and even the emergence of root hairs were not accompanied by the disappearance of mixed-linkage glucans from cell walls. The diversity of xylan motifs recognized by different antibodies was minimal in the meristem zone of rye roots, but this diversity increased and showed tissue specificity during root growth. Antibodies specific for xyloglucans, galactans, arabinans and mannans bound the cell content. When rye root cells were cut, the epitopes of xyloglucans, galactans and arabinans remained within the cell content, while mannans developed net-like or film-like structures on the surface of sections.

Isolation and structure characterization of a low methyl-esterified pectin from the tuber of Dioscorea opposita Thunb.

A low methyl-esterified pectin (33.2% methyl-esterification degree) was isolated from the tuber of Dioscorea opposita Thunb., which was an edible and medicinal material in China. This pectin (Mw of 1.3 × 104 g/mol) contained the ~59.1% homogalacturonan (HG) and ~38.1% highly branched rhamnogalacturonan I (RG-I) region with possible side chains embracing arabinogalactan II, arabinan or arabinogalactan I. The fragments including HG backbone consisting of â†’ 4)-α-GalpA-(1 â†’ and â†’ 4)-α-GalpA-6-O-methyl-(1 â†’ with molar ratio of ~2:1, and repeating unit of arabinogalactan II side chain composed of α-Araf-(1 â†’ and â†’ 3,6)-ß-Galp-(1→, were speculated through methylation analysis and NMR spectra. However, the linkage pattern for RG-I backbone and side chains were indiscernible due to limited resolution of NMR spectra. Besides, the pectin adopted a flexible chain conformation in 0.1 M NaNO3 solution. These results provided a structural basis for study on polysaccharide from D. opposite, which was benefit for development of functional food of yam.

Pectic galactan affects cell wall architecture during secondary cell wall deposition.

MAIN CONCLUSION: ß-(1,4)-galactan determines the interactions between different matrix polysaccharides and cellulose during the cessation of cell elongation. Despite recent advances regarding the role of pectic ß-(1,4)-galactan neutral side chains in primary cell wall remodelling during growth and cell elongation, little is known about the specific function of this polymer in other developmental processes. We have used transgenic Arabidopsis plants overproducing chickpea ßI-Gal ß-galactosidase under the 35S CaMV promoter (35S::ßI-Gal) with reduced galactan levels in the basal non-elongating floral stem internodes to gain insight into the role of ß-(1,4)-galactan in cell wall architecture during the cessation of elongation and the beginning of secondary growth. The loss of galactan mediated by ßI-Gal in 35S::ßI-Gal plants is accompanied by a reduction in the levels of KOH-extracted xyloglucan and an increase in the levels of xyloglucan released by a cellulose-specific endoglucanase. These variations in cellulose-xyloglucan interactions cause an altered xylan and mannan deposition in the cell wall that in turn results in a deficient lignin deposition. Considering these results, we can state that ß-(1,4)-galactan plays a key structural role in the correct organization of the different domains of the cell wall during the cessation of growth and the early events of secondary cell wall development. These findings reinforce the notion that there is a mutual dependence between the different polysaccharides and lignin polymers to form an organized and functional cell wall.

Dietary fibre profiles of Turkish Tombul hazelnut (Corylus avellana L.) and hazelnut skin.

Dietary fibre (DF) profiles of natural hazelnut, roasted hazelnut and hazelnut skin were analyzed. Insoluble (IDF) and soluble (SDF) DFs were examined for monosaccharide and glycosyl-linkage compositions using gas chromatography-mass spectrometry (GC-MS). Total DF contents of natural hazelnut, roasted hazelnut, and hazelnut skin were 17.8, 15.4, and 69.8%, respectively; majority of which (>96%) were water-insoluble. IDFs of natural and roasted hazelnuts were composed of cellulose (~49%), pectic polysaccharides (~30%), and xyloglucans (~15%), whereas that of hazelnut skin made up lignin (~55%) and fibre polysaccharides (cellulose, pectic polysaccharides, and xyloglucans, ~45%). Unlike the ones from other sources, pectic polysaccharides in IDFs had lower proportion of smooth region and higher proportion of hairy region that is heavily branched with arabinan and galactan side chains. Xyloglucans were also densely branched with monomeric and/or dimeric side chains. SDFs of the samples were composed of heavily branched heteromannans (~60%), slightly branched pectic polysaccharides (~25%), and xyloglucans possessing monomeric side chains (~5%). These results suggest that hazelnut is rich in DFs that have potential to improve large bowel function and hazelnut skin, a byproduct of hazelnut roasting process, could be utilized for the production of functional carbohydrates having prebiotic capacities.

Soluble cell wall carbohydrates and their relationship with sensory attributes in Cabernet Sauvignon wine.

The chemical and sensory profiles of wines prepared from Cabernet Sauvignon grapes at different ripening stages vary greatly. Here, the soluble cell wall carbohydrate (SCWC) and phenolic profiles of wines were analyzed in parallel with the sensory evaluation of their mouthfeel and taste characteristics. Both SCWCs and phenolic compounds correlated with wine mouthfeel. When analyses were extended to specific classes of cell wall carbohydrates, it was shown that rhamnogalacturonan I/II, arabinan, arabinogalactan types I and II and xyloglucan from grapes were the key determinants of overall mouthfeel descriptors, particularly viscosity, astringency and roughness, whereas heteromannan from grapes was associated with mouth coating and chalkiness. A perceived sour taste was notably associated with higher homogalacturonan contents. This finding provides insights into the contributions of non-phenolic compounds to wine mouthfeel. The data provide opportunities for the development of simple monosaccharide marker assays to monitor major mouthfeel characteristics in red wines.

Comparative analysis of protein composition and digestibility of Ceratonia siliqua L. and Prosopis spp. seed germ flour.

By virtue of exclusive nutrient composition and nutritional properties, seed germ flours from both European carob (Ceratonia siliqua L.) and South American algarrobo (Prosopis alba and Prosopis nigra) or vinal (Prosopis ruscifolia) have potential as a high nutritional value and health-promoting ingredient for food formulations. In order to define their compositional and functional properties, we investigated the germ protein content of carob compared to the P. alba, P. nigra and P. ruscifolia counterparts, applying proteomics and complementary methods. The mono- and two-dimensional electrophoretic profiles of Prosopis spp. were very similar among one another, while C. siliqua exhibited significant differences. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy highlighted a dominant ß-sheet structural conformation for C. siliqua, suggesting that carob germ flour might more suited than Prosopis germ flour for baking and food technological applications. In contrast, Prosopis spp. contained a more adequate nutritional value than C. siliqua, in terms of essential amino acid complement. Both carob and algarrobo germ flour samples were highly digestible, as demonstrated by in vitro simulated gastrointestinal digestion, releasing high amounts of free amino acids and only minor proportions of low molecular weight peptides.

Structural characterisation of polysaccharides from roasted hazelnut skins.

Two polysaccharide fractions sequentially extracted with water 1W and alkali 1A, were isolated from the hazelnut skins. The monosaccharide composition together with the FTIR and NMR analyses, indicated that both fractions are formed from a mixture of polysaccharides. The fraction 1W consists of methyl-esterified pectic polysaccharide with rhamnogalacturonan I blocks, branching with arabinose side chains, and with 1,5-, 1,3,5-arabinan and galactan polysaccharides. The fraction 1A is a mixture of deesterified rhamnogalacturonan I and 1,5-, 1,3,5-arabinan and 4-O-Me-glucuronoxylan polysaccharides. The presence of unsaturated galacturonic acid and the heterogeneity of the molecular weights, which Mw ranged between 3.6 and 39 kg mol-1, indicated the pectin degradation during roasting.

Yellow lupin (Lupinus luteus L.) polysaccharides: Antioxidant, immunomodulatory and prebiotic activities and their structural characterisation.

Yellow lupin polysaccharides (YLP-1, YLP-2 and YLP-3) were isolated from the whole seeds of Lupinus luteus L. Their antioxidant activities were evaluated by ABTS+ and hydroxyl radical scavenging, and Fe2+ chelating assays. Immunostimulatory activities were measured by their ability to activate macrophages to produce TNF-α and NO. Four strains of probiotic bacteria were used to measure their prebiotic activities. YLP-2 with largest galactose content displayed the best activity amongst the three isolated polysaccharides. NMR and FT-IR spectroscopic methods have revealed that YLPs contain galactans and galactomannans which are linked with ß-(1,4) glycosidic bond in the main chain. The side chain Galp unit of galactomannan is connected to the main chain Manp by α-(1,6) linkage. The results presented in this paper strongly suggest that YLPs display significant antioxidant, immunostimulatory and prebiotic activities and hence hold great potential as nutraceutical and functional agents.

Common Hydraulic Fracturing Fluid Additives Alter the Structure and Function of Anaerobic Microbial Communities.

The development of unconventional oil and gas (UOG) resources results in the production of large volumes of wastewater containing a complex mixture of hydraulic fracturing chemical additives and components from the formation. The release of these wastewaters into the environment poses potential risks that are poorly understood. Microbial communities in stream sediments form the base of the food chain and may serve as sentinels for changes in stream health. Iron-reducing organisms have been shown to play a role in the biodegradation of a wide range of organic compounds, and so to evaluate their response to UOG wastewater, we enriched anaerobic microbial communities from sediments collected upstream (background) and downstream (impacted) of an UOG wastewater injection disposal facility in the presence of hydraulic fracturing fluid (HFF) additives: guar gum, ethylene glycol, and two biocides, 2,2-dibromo-3-nitrilopropionamide (DBNPA) and bronopol (C3H6BrNO4). Iron reduction was significantly inhibited early in the incubations with the addition of biocides, whereas amendment with guar gum and ethylene glycol stimulated iron reduction relative to levels in the unamended controls. Changes in the microbial community structure were observed across all treatments, indicating the potential for even small amounts of UOG wastewater components to influence natural microbial processes. The microbial community structure differed between enrichments with background and impacted sediments, suggesting that impacted sediments may have been preconditioned by exposure to wastewater. These experiments demonstrated the potential for biocides to significantly decrease iron reduction rates immediately following a spill and demonstrated how microbial communities previously exposed to UOG wastewater may be more resilient to additional spills.IMPORTANCE Organic components of UOG wastewater can alter microbial communities and biogeochemical processes, which could alter the rates of essential natural attenuation processes. These findings provide new insights into microbial responses following a release of UOG wastewaters and are critical for identifying strategies for the remediation and natural attenuation of impacted environments.

Development of protein, dietary fiber, and micronutrient enriched extruded corn snacks.

The study was aimed to develop protein, dietary fiber, and micronutrient enriched corn snacks through extrusion processing. Corn snacks supplemented with chickpea, defatted soy flour (20-40/100 g) and guar gum (7/100 g) were prepared through extrusion processing. Micronutrients (iron, zinc, iodine, and vitamins A, C, and folic acid) at recommended daily values were added in all formulations. Extruded corn snacks were analyzed for physical, textural, and sensory attributes. Results showed that piece density (0.34-0.44 g/cm3 ), moisture (3.40-5.25%), water activity (0.203-0.361), hardness (64.4-133.2 N), and cohesiveness (0.25-0.44) was increased Whereas, expansion ratio (3.72-2.64), springiness (0.82-0.69), chewiness (1.63-0.42), and resilience (1.37-0.14) was decreased as supplementation with soy and chickpea flour increased from 20 to 40/100 g. Overall corn snack supplemented with 15/100 g of soy and 15/100 g of chickpea flour got the highest acceptance from the sensory panelists. PRACTICAL APPLICATIONS: The article focuses on physical, textural, and sensory attributes of extruded corn snacks enriched with protein, dietary fiber, and micronutrients Awareness about the importance of healthy snacks has grown among the consumers during the last decade. Extruded snacks developed using nutrient rich ingredients with good textural and sensory properties has always remained a challenge for the snack industry. Texture of the extruded snacks varies a lot with high levels of protein and dietary fiber. This study is helpful for the development of healthy snacks especially in developing countries lacking storage infrastructure or tropical environment. Nutrient rich extruded snacks can also be used to alleviate malnutrition by incorporating in school lunch programs.

Characterization of a water soluble, hyperbranched arabinogalactan from yacon (Smallanthus sonchifolius) roots.

Yacon (Smallanthus sonchifolius Poepp. & Endl.) roots are largely grown in Andean countries and have attracted recent interest due to their antioxidant and prebiotic effects. Yacon is typically consumed as a fruit due to its sweet taste and juiciness. The macromolecular properties of an aqueous extract of yacon are investigated using asymmetric flow field-flow fractionation (AF4) coupled to UV, multiangle light scattering (MALS) and differential refractive index (dRI) detection. The method allows for determination of molar mass and size over the size distribution. Three major populations were found of which one strongly dominates in concentration. Through collection of fractions from AF4, carbohydrate composition and glycosidic linkage analysis for the dominating population was performed. The results show that the dominating population consists of a highly branched arabinogalactan (type 2) with a molar mass of approximately 1-2·105g/mol, a hydrodynamic radius of approximately 6-10nm and a relatively high apparent density (approx. 70-150kg/m3).

Detection of Inulin, a Prebiotic Polysaccharide, in Maple Syrup.

Maple syrup is a widely consumed plant-derived natural sweetener produced by concentrating xylem sap collected from certain maple (Acer) species. During thermal evaporation of water, natural phytochemical components are concentrated in maple syrup. The polymeric components from maple syrup were isolated by ethanol precipitation, dialysis, and anion exchange chromatography and structurally characterized by glycosyl composition analysis, glycosyl linkage analysis, and nuclear magnetic resonance spectroscopy. Among the maple syrup polysaccharides, one neutral polysaccharide was characterized as inulin with a broad molecular weight distribution, representing the first isolation of this prebiotic carbohydrate from a xylem sap. In addition, two acidic polysaccharides with structural similarity were identified as arabinogalactans derived from rhamnogalacturonan type I pectic polysaccharides.

Structural characteristics of oxalate-soluble polysaccharides of Sosnowsky's hogweed (Heracleum sosnowskyi Manden).

Arabinogalactan proteins (AGP) and pectic polysaccharides were isolated from above-ground parts of Heracleum sosnowskyi. The structural study has shown that a linear region of the pectic macromolecules consists of 1,4-α-d-galactopyranosyluronan blocks partially methyl esterified and acetylated. The branched region consists of 3-O- and partially 2-O-acetylated rhamnogalacturonan I. Side chains of the RG-I backbone include the regions of arabinogalactan I and branched 1,5-α-l-arabinan. The carbohydrate part of AGP consists of arabinogalactan II with a 1,3-ß-d-Galp main chain. The side chains of the branched area of AG-II are composed of 1,6-ß-d-Galp, 1,5-, 1,3,5-α-l-Araf, 4-O-Me-ß-d-GlcA and 1,4-ß-d-GlcpA, and non-reducing ends residues of ß-d-Galp, α-l-Araf, α-l-Rhap and α-l-Fucp. The branch points of the main and side chains are formed by 3,6-di-O-substituted ß-d-Galp. It was found that at least a portion of pectin is probably covalently linked to AGP, wherein AGP is linked to RG-I, but not with galacturonan.

Rapid screening of guar gum using portable Raman spectral identification methods.

Guar gum is a well-known inactive ingredient (excipient) used in a variety of oral pharmaceutical dosage forms as a thickener and stabilizer of suspensions and as a binder of powders. It is also widely used as a food ingredient in which case alternatives with similar properties, including chemically similar gums, are readily available. Recent supply shortages and price fluctuations have caused guar gum to come under increasing scrutiny for possible adulteration by substitution of cheaper alternatives. One way that the U.S. FDA is attempting to screen pharmaceutical ingredients at risk for adulteration or substitution is through field-deployable spectroscopic screening. Here we report a comprehensive approach to evaluate two field-deployable Raman methods--spectral correlation and principal component analysis--to differentiate guar gum from other gums. We report a comparison of the sensitivity of the spectroscopic screening methods with current compendial identification tests. The ability of the spectroscopic methods to perform unambiguous identification of guar gum compared to other gums makes them an enhanced surveillance alternative to the current compendial identification tests, which are largely subjective in nature. Our findings indicate that Raman spectral identification methods perform better than compendial identification methods and are able to distinguish guar gum from other gums with 100% accuracy for samples tested by spectral correlation and principal component analysis.

Microwave-assisted alkaline extraction of galactan-rich rhamnogalacturonan I from potato cell wall by-product.

Galactan-rich rhamnogalacturonan I (RG I), exhibiting promising health benefits, is the most abundant polysaccharide in potato pulp by-product. In the present study, the microwave-assisted alkaline extraction of galactan-rich RG I was investigated. Solid/liquid ratio was identified as the most significant parameter affecting linearly yield and galactose/rhamnose contents. Microwave power and solid/liquid ratio exhibited a significant adverse interactive effect on the yield. Galactose content of extracted polysaccharides can be modulated by compromising between KOH concentration and extraction time, which exhibited adverse interaction. Optimum conditions were identified using the established predicted models and consisted of treatment of potato cell wall at solid/liquid ratio of 2.9% (w/v) with 1.5M KOH under microwave power of 36.0 W for 2.0 min. Yield of intact galactan-rich RG I of 21.6% and productivity of 192.0 g/Lh were achieved. The functional properties of RG I-rich polysaccharides were comparable or superior to potato galactan and oranges homogalacturonan.

The Deconstruction of Pectic Rhamnogalacturonan I Unmasks the Occurrence of a Novel Arabinogalactan Oligosaccharide Epitope.

Rhamnogalacturonan I (RGI) is a pectic polysaccharide composed of a backbone of alternating rhamnose and galacturonic acid residues with side chains containing galactose and/or arabinose residues. The structure of these side chains and the degree of substitution of rhamnose residues are extremely variable and depend on species, organs, cell types and developmental stages. Deciphering RGI function requires extending the current set of monoclonal antibodies (mAbs) directed to this polymer. Here, we describe the generation of a new mAb that recognizes a heterogeneous subdomain of RGI. The mAb, INRA-AGI-1, was produced by immunization of mice with RGI oligosaccharides isolated from potato tubers. These oligomers consisted of highly branched RGI backbones substituted with short side chains. INRA-AGI-1 bound specifically to RGI isolated from galactan-rich cell walls and displayed no binding to other pectic domains. In order to identify its RGI-related epitope, potato RGI oligosaccharides were fractionated by anion-exchange chromatography. Antibody recognition was assessed for each chromatographic fraction. INRA-AGI-1 recognizes a linear chain of (1→4)-linked galactose and (1→5)-linked arabinose residues. By combining the use of INRA-AGI-1 with LM5, LM6 and INRA-RU1 mAbs and enzymatic pre-treatments, evidence is presented of spatial differences in RGI motif distribution within individual cell walls of potato tubers and carrot roots. These observations raise questions about the biosynthesis and assembly of pectin structural domains and their integration and remodeling in cell walls.

Lipid Peroxidation-Antioxidant Defense System during Toxic Liver Damage and Its Correction with a Nanocomposite [corrected] Substance Containing Selenium and Arabinogalactan.

Experiments on rat model of toxic liver damage (CCl4, subcutaneously) have demonstrated that selenium nanopreparation on arabinogalactan matrix and partially arabinogalactan alone prevented the development of oxidative stress assessed by the balance of LPO and antioxidant defense processes.

Characterization and prebiotic activity of aqueous extract and indigestible polysaccharide from Anoectochilus formosanus.

Anoectochilus formosanus (Orchidaceae) is a folk medicine in Asia. This study investigated the in vivo and in vitro prebiotic effects of an aqueous extract of A. formosanus (SAEAF) and of an indigestible polysaccharide (AFP) isolated from SAEAF. Chemical analyses showed AFP was mainly composed of arabinogalactan type II (AG-II), with an average molecular weight of 29 kDa. Following 4 weeks of oral administration to rats, SAEAF exhibited prebiotic effects including a decrease in cecum pH and increases of calcium absorption and fecal bifidobacteria. Furthermore, through a bioactivity-guided separation strategy, AFP was proven to be a bifidogenic component in vitro fecal strains fermentation and in vivo administration to mice. In RT-PCR analysis of Bifidobacterium , AFP increased the expression of ABC transporter related to nutrient uptake. Thus, AFP, a polysaccharide from A. formosanus, was demonstrated to be a prebiotic that has a positive health effect on gut microbiota.

Analysis of the neutral polysaccharide fraction of MCP and its inhibitory activity on galectin-3.

The pH-modified citrus pectin (MCP) has been demonstrated to inhibit galectin-3 in cancer progression. The components and structures of MCP related to this inhibition remained unknown. In this paper, we fractionated MCP on DEAE-cellulose column into a homogenous neutral fraction MCP-N (about 20 kDa) and a pectin mixture fraction MCP-A (wide molecular distribution on Sepharose CL-6B chromatography). Both MCP-N and MCP-A inhibited hemagglutination mediated by galectin-3 with minimum inhibition concentration (MIC) 625 and 0.5 µg/ml, respectively. MCP-N was identified to be a type I arabinogalactan (AG-I) with a main chain of ß-1→4-galactan. MCP-N was digested by α-L-arabinofuranosidase to give its main chain structure fraction (M-galactan, around 18 kDa), which was more active than the original molecule, MIC 50 µg/ml. The acidic degradation of M-galactan increased the inhibitory activity, MIC about 5 times lower than M-galactan. These results above showed that the functional motif of the ß-1→4-galactan fragment might lie in the terminal residues rather than in the internal region of the chain. Therefore, MCP-N and its degraded products might be developed to new potential galectin-3 inhibitors. This is the first report concerning the fractionation of MCP and its components on galectin-3 inhibition. The information provided in this paper is valuable for screening more active galectin-3 inhibitors from natural polysaccharides.