Evaluating the Utility of Permethylated Polysaccharide Solution NMR Data for Characterization of Insoluble Plant Cell Wall Polysaccharides

Permethylation as a strategy for high-molecular-weight polysaccharide structure analysis by nuclear magnetic resonance-Case study of Xylella fastidiosa extracellular polysaccharide

Current practices for structural analysis of extremely large-molecular-weight polysaccharides via solution-state nuclear magnetic resonance (NMR) spectroscopy incorporate partial depolymerization protocols that enable polysaccharide solubilization in suitable solvents. Non-specific depolymerization techniques utilized for glycosidic bond cleavage, such as chemical degradation or ultrasonication, potentially generate structural fragments that can complicate complete and accurate characterization of polysaccharide structures. Utilization of appropriate enzymes for polysaccharide degradation, on the other hand, requires prior structural knowledge and optimal enzyme activity conditions that are not available to an analyst working with novel or unknown compounds. Herein, we describe an application of a permethylation strategy that allows the complete dissolution of intact polysaccharides for NMR structural characterization. This approach is utilized for NMR analysis of Xylella fastidiosa extracellular polysaccharide (EPS), which is essential for the virulence of the plant pathogen that affects multiple commercial crops and is responsible for multibillion dollar losses each year.

Methylation-GC-MS/FID-Based Glycosidic Linkage Analysis of Unfractionated Polysaccharides in Red Seaweeds

Glycosidic linkage analysis was conducted on the unfractionated polysaccharides in alcohol-insoluble residues (AIRs) prepared from six red seaweeds (Gracilariopsis sp., Prionitis sp., Mastocarpus papillatus, Callophyllis sp., Mazzaella splendens, and Palmaria palmata) using GC-MS/FID analysis of partially methylated alditol acetates (PMAAs). The cell walls of P. palmata primarily contained mixed-linkage xylans and small amounts of sulfated galactans and cellulose. In contrast, the unfractionated polysaccharides of the other five species were rich in galactans displaying diverse 3,6-anhydro-galactose and galactose linkages with varied sulfation patterns. Different levels of cellulose were also observed. This glycosidic linkage method offers advantages for cellulose analysis over traditional monosaccharide analysis that is known for underrepresenting glucose in crystalline cellulose. Relative linkage compositions calculated from GC-MS and GC-FID measurements showed that anhydro sugar linkages generated more responses in the latter detection method. This improved linkage workflow presents a useful tool for studying polysaccharide structural variations across red seaweed species. Furthermore, for the first time, relative linkage compositions from GC-MS and GC-FID measurements, along with normalized FID and total ion current (TIC) chromatograms without peak assignments, were analyzed using principal component analysis (PCA) as a proof-of-concept demonstration of the technique's potential to differentiate various red seaweed species.

Extraction, structural characterization and immunoactivity of glucomannan type polysaccahrides from Lilium brownii var. viridulum Baker

Homogeneous polysaccharide (LBP) was extracted and purified from the bulblets of Lilium brownii var. viridulum Baker with a molecular weight of 312 kDa. The monosaccharides are composed of mannose and glucose, and the corresponding molar ratios are 0.582 and 0.418, respectively. FT-IR, LC-MS, NMR, GC-MS and HPAEC were used to analyze the functional groups, glycosidic linkages and chemical structure of LBP, which was a 1-4-linked glucomannan and contained a dodecasaccharide repeating units of →4)-β-D-Manp-(1 → 4)-β-D-Manp-(1 → 4)-β-D-Manp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Manp-(1 → 4)-β-D-Manp-(1 → 4)-β-D-Glcp-(1 → 4)-α-D-Glcp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Manp-(1 → 4)-β-D-Manp-(1 → . In vitro experimental results showed that LBP had noble biocompatibility, and a low dose of 5 μg/mL LBP significantly up-regulated the mRNA expression of TNF-α, iNOS, IL-6, IL-1β and Toll-like receptors family (TLRs) in RAW 264.7 cells. In conclusion, LBP played an important role in immunomodulation, and further studies on the specific immunomodulatory mechanisms of LBP on RAW 264.7 cells are still needed.

Polysaccharide assemblies in fungal and plant cell walls explored by solid-state NMR

Structural analysis of macromolecular complexes within their natural cellular environment presents a significant challenge. Recent applications of solid-state NMR (ssNMR) techniques on living fungal cells and intact plant tissues have greatly enhanced our understanding of the structure of extracellular matrices. Here, we selectively highlight the most recent progress in this field. Specifically, we discuss how ssNMR can provide detailed insights into the chemical composition and conformational structure of pectin, and the consequential impact on polysaccharide interactions and cell wall organization. We elaborate on the use of ssNMR data to uncover the arrangement of the lignin-polysaccharide interface and the macrofibrillar structure in native plant stems or during degradation processes. We also comprehend the dynamic structure of fungal cell walls under various morphotypes and stress conditions. Finally, we assess how the combination of NMR with other techniques can enhance our capacity to address unresolved structural questions concerning these complex macromolecular assemblies.

Permethylation as a Strategy for High Molecular Weight Polysaccharide Structure Analysis by NMR - Case Study of Xylella fastidiosa EPS

Current practices for structure analysis of extremely large molecular weight polysaccharides via solution-state NMR spectroscopy incorporate partial depolymerization protocols that enable polysaccharide solubilization in suitable solvents. Non-specific depolymerization techniques utilized for glycosidic bond cleavage, such as chemical degradation or ultrasonication, potentially generate structure fragments that can complicate the complete characterization of polysaccharide structures. Utilization of appropriate enzymes for polysaccharide degradation, on the other hand, requires prior structure information and optimal enzyme activity conditions that are not available to the analyst working with novel or unknown compounds. Herein, we describe the application of a permethylation strategy that allows the complete dissolution of the intact polysaccharides for NMR structure characterization. This approach is utilized for NMR analysis of Xylella fastidiosa EPS, which is essential for the virulence the plant pathogen that affects multiple commercial crops and is responsible for multibillion dollar losses each year.

A novel approach for quantitative determination of cellulose content in tobacco via 2D HSQC NMR spectroscopy

Cellulose is an important component of tobacco (Nicotiana tabacum L.) cell walls, which can be precursors for many harmful compounds in smoke. Traditional cellulose content analysis methods involve sequential extraction and separation steps, which are time-consuming and environmentally unfriendly. In this study, a novel method was first introduced to analyze cellulose content in tobacco via two-dimensional heteronuclear single quantum coherence (2D HSQC) NMR spectroscopy. The method was based on derivatization approach to allow the dissolution of insoluble polysaccharide fractions of tobacco cell walls in DMSO‑d₆/pyridine-d₅ (4:1 v/v) for NMR analysis. The NMR results suggested that besides the main NMR signals of cellulose, partial signals of hemicellulose including mannopyranose, arabinofuranose, and galactopyranose units could also be identified. In addition, the utilization of relaxation reagents has proved to be an effective way to improve the sensitivity of 2D NMR spectroscopy, which was beneficial for quantification of biological samples with limited quantities. To overcome the limitations of quantification using 2D NMR, the calibration curve of cellulose with 1,3,5-trimethoxybenzene as internal reference was constructed and thus the accurate measurement of cellulose in tobacco was achieved. Compared with the chemical method, the interesting method was simple, reliable, and environmentally friendly, which provided a new insight for quantitative determination and structure analysis of plant macromolecules in complex samples.

Carboxyl-Based CPMP Tag for Ultrasensitive Analysis of Disaccharides by Negative Tandem Mass Spectrometry

Here, we develop a sensitive method for glucose-containing disaccharide analysis by 1-(4-carboxyphenyl)-3-methyl-5-pyrazolone (CPMP) derivatization using mass spectrometry. The intense anion of [M - H]^- (m/z 759) was observed for CPMP-labeled disaccharides in a negative mode. After derivatization, its sensitivity was significantly increased with the limits of detection (LODs) and limits of quantification (LOQ) ranging from 3.90 to 8.67 ng L^-1 and 12.99 to 28.92 ng L^-1, respectively. During CID-MS/MS analysis, the fragment patterns of CPMP derivatized disaccharides in the negative mode were simpler and clearer than their counterparts in a positive mode, which further could be applied to distinct and relatively quantitative isomeric disaccharides with ultrahigh sensitivity and good reproducibility. The great linear relationships could be achieved under wider concentration ratios from 0.01 to 20 compared to the previous report. Eventually, the developed methodology was applicable to identify isomeric disaccharides in beers. No sucrose was discovered. All beers contain 1,4- and 1,6-linked disaccharides. Some of them also have a mixture of 1,2- and 1,3-linked disaccharides. Through the integration of statistical analysis, beers with different production processes were finally discriminated, and the relative quantification of isomaltose and maltose was realized. In general, this method is sensitive, fast, and reliable for the discrimination and relative quantification of isomeric disaccharides in complex matrices. This study provides a new idea for the structural analysis of oligosaccharides in food, plants, and animals and an important theoretical basis for the exploration of new functions of oligosaccharides.

Structural studies of a mannoglucan from Cremastra appendiculata (Orchidaceae) by chemical and enzymatic methods

Pseudobulb of Cremastra appendiculata (Orchidaceae) is a traditionally used medicine in China for treatment of certain cancers. The polysaccharides from this medicinal plant are poorly understood. Therefore, we focused on the isolation and fine structure characterization of C. appendiculata polysaccharides. After isolation by DE-52 and Superdex 200 gel chromatography, the purified polysaccharide (named as CAP) with Mw 557.5 kDa was obtained with a narrow and symmetric peak presented in the HPGPC. The monosaccharide composition results showed in HPAEC that CAP was a heteropolysaccharide composed of glucose and mannose at a molar ratio roughly 0.34:0.66. The methylation results indicated that CAP was a 1,4-β-mannose and 1,4-β-glucose linear linkage. The further NMR studies suggested a 0.208 acetylation substitution of CAP and a hexasaccharide repeating unit composed of 1,4-β-mannose and1, 4-β-glucose in the CAP structure. The chemical structure of CAP was confirmed further by the specific glucanase and mannanase hydrolysis results.

Combined whole cell wall analysis and streamlined in silico carbohydrate-active enzyme discovery to improve biocatalytic conversion of agricultural crop residues

The production of biofuels as an efficient source of renewable energy has received considerable attention due to increasing energy demands and regulatory incentives to reduce greenhouse gas emissions. Second-generation biofuel feedstocks, including agricultural crop residues generated on-farm during annual harvests, are abundant, inexpensive, and sustainable. Unlike first-generation feedstocks, which are enriched in easily fermentable carbohydrates, crop residue cell walls are highly resistant to saccharification, fermentation, and valorization. Crop residues contain recalcitrant polysaccharides, including cellulose, hemicelluloses, pectins, and lignin and lignin-carbohydrate complexes. In addition, their cell walls can vary in linkage structure and monosaccharide composition between plant sources. Characterization of total cell wall structure, including high-resolution analyses of saccharide composition, linkage, and complex structures using chromatography-based methods, nuclear magnetic resonance, -omics, and antibody glycome profiling, provides critical insight into the fine chemistry of feedstock cell walls. Furthermore, improving both the catalytic potential of microbial communities that populate biodigester reactors and the efficiency of pre-treatments used in bioethanol production may improve bioconversion rates and yields. Toward this end, knowledge and characterization of carbohydrate-active enzymes (CAZymes) involved in dynamic biomass deconstruction is pivotal. Here we overview the use of common "-omics"-based methods for the study of lignocellulose-metabolizing communities and microorganisms, as well as methods for annotation and discovery of CAZymes, and accurate prediction of CAZyme function. Emerging approaches for analysis of large datasets, including metagenome-assembled genomes, are also discussed. Using complementary glycomic and meta-omic methods to characterize agricultural residues and the microbial communities that digest them provides promising streams of research to maximize value and energy extraction from crop waste streams.

PL-S2, a homogeneous polysaccharide from Radix Puerariae lobatae, attenuates hyperlipidemia via farnesoid X receptor (FXR) pathway-modulated bile acid metabolism

Polysaccharides are important active constituents of Radix Puerariae lobatae (RPL). In this study, a novel homogeneous polysaccharide from RPL was successfully obtained by HP-20 macroporous resin and purified by Sepharose G-100 column chromatography. Nuclear magnetic resonance (NMR) analysis showed that the main glycosidic bonds were composed of α-1,3-linked and α-1,4-linked glucose. The molecular weight of PL-S2 was 18.73 kDa. The hypolipidemic effect of PL-S2 on hyperlipidemic rats was evaluated in histopathology and metabolomics analyses. PL-S2 significantly reduced plasma lipid levels and inhibited bile acid metabolism. We also demonstrated that treatment with PL-S2 activated FXR, CYP7A1, BESP, and MRP2 in rat liver. Our findings first indicate that PL-S2 decreases plasma lipid levels in hyperlipidemic rats by activating the FXR signaling pathway and promoting bile acid excretion. Therefore, PL-S2 derived from RPL is implicated as a functional food factor with lipid-regulating activity, and highlighted as a potential food supplement for the treatment of hyperlipidemia.