Antioxidant Active Polysaccharides Extracted with Oxalate from Wild Blackthorn Fruits (Prunus spinosa L.).

Although several therapeutic effects have been attributed to wild blackthorn fruits, their use is still negligible. Purification of the antioxidant-active fraction, obtained from wild blackthorn fruits by hot ammonium oxalate extraction (Ao), yielded seven fractions after successive elution with water, sodium chloride and sodium hydroxide solutions. The purified fractions differ in carbohydrates, proteins, and phenolics. About 60% of the applied Ao material was recovered from the column, with the highest yields eluted with 0.25 M NaCl solution, accounting for up to 70 wt% of all eluted material. Analyses have shown that two dominant fractions (3Fa and 3Fb) contain 72.8-81.1 wt% of galacturonic acids, indicating the prevalence of homogalacturonans (HG) with a low acetyl content and a high degree of esterification. The low content of rhamnose, arabinose and galactose residues in both fractions indicates the presence of RG-I associated with arabinogalactan. In terms of yield, the alkali-eluted fraction was also significant, as a dark brown-coloured material with a yield of ~15 wt% with the highest content of phenolic compounds of all fractions. However, it differs from other fractions in its powdery nature, which indicates a high content of salts that could not be removed by dialysis.

Pectic polysaccharides derived from Hainan Rauwolfia ameliorate NLR family pyrin domain-containing 3-mediated colonic epithelial cell pyroptosis in ulcerative colitis.

Pectic polysaccharides (PPs) could exert functions on ulcerative colitis (UC), which is classified as a nonspecific inflammatory disorder. This study investigated the molecular mechanism of PPs derived from Rauwolfia in UC. First, the dextran sodium sulfate (DSS)-induced mouse colitis models and lipopolysaccharide (LPS)-treated colonic epithelial cell (YAMC) models were established and treated with PP. Subsequently, the effects of PPs on mucosal damages in DSS mice were detected, and the levels of inflammatory cytokines, pyroptosis-related factors, oxidative stress-related markers, and the tight junction-related proteins in the tissues or cells were examined, and the results suggested that PPs ameliorated colonic mucosal damages and cell pyroptosis in DSS mice, and limited colonic epithelial cell pyroptosis in in vitro UC models. Subsequently, the binding relations of retinol-binding protein 4 (RBP4) to miR-124-3p and NLR pyrin domain-containing 3 (NLRP3) were analyzed. miR-124-3p targeted RBP4 and reduced the binding of RBP4 to NLRP3, thus inhibiting NLRP3-mediated pyroptosis. Finally, functional rescue experiments revealed that miR-124-3p suppression or RBP4 overexpression promoted colonic epithelial cell pyroptosis. Collectively, Rauwolfia-derived PPs limited miR-124-3p and targeted RBP4 and reduced the binding potency of RBP4 to NLRP3 to inhibit NLRP3-mediated pyroptosis, resulting in the alleviation of colonic epithelial cell pyroptosis and mucosal damages in UC.

The digestive behavior of pectin in human gastrointestinal tract: a review on fermentation characteristics and degradation mechanism.

Pectin is widely spread in nature and it develops an extremely complex structure in terms of monosaccharide composition, glycosidic linkage types, and non-glycosidic substituents. As a non-digestible polysaccharide, pectin exhibits resistance to human digestive enzymes, however, it is easily utilized by gut microbiota in the large intestine. Currently, pectin has been exploited as a novel functional component with numerous physiological benefits, and it shows a promising prospect in promoting human health. In this review, we introduce the regulatory effects of pectin on intestinal inflammation and metabolic syndromes. Subsequently, the digestive behavior of pectin in the upper gastrointestinal tract is summarized, and then it will be focused on pectin's fermentation characteristics in the large intestine. The fermentation selectivity of pectin by gut bacteria and the effects of pectin structure on intestinal microecology were discussed to highlight the interaction between pectin and bacterial community. Meanwhile, we also offer information on how gut bacteria orchestrate enzymes to degrade pectin. All of these findings provide insights into pectin digestion and advance the application of pectin in human health.

Polysaccharides and Bioactive Phenolics from Aconitum septentrionale Roots.

Aconitum septentrionale is known to contain toxic diterpene alkaloids, while other bioactive compounds in the plant remain unclear. The aim of this study was to explore the phenolic compounds and polysaccharides from the water extract of A. septentrionale roots. Fifteen phenolic compounds were isolated and identified by NMR and MS, including fourteen known and one new dianthramide glucoside (2-[[2-(ß-D-glucopyranosyloxy)-5-hydroxybenzoyl]amino]-4,5-dihydroxybenzoic acid methyl ester, 14). One neutral (complex of glucans with minor amounts of mannans) and two acidic polysaccharide fractions (complexes of pectic polysaccharides and glucans) were also obtained. Hydroxytyrosol (1), hydroxytyrosol-1-O-ß-glucoside (2) and bracteanolide A (7) inhibited the release of nitric oxide by dendritic cells. Magnoflorine (8) and 2-[[2-(ß-D-glucopyranosyloxy)-5-hydroxybenzoyl]amino]-5-hydroxybenzoic acid methyl ester (12) inhibited 15-lipoxygenase, and bracteanolide A (7) was a moderate inhibitor of xanthine oxidase. This study is the first to describe the diversity of phenolics and polysaccharides from A. septentrionale and their anti-inflammatory and anti-oxidant activities.

Novel Pectic Polysaccharides Isolated from Immature Honey Pomelo Fruit with High Immunomodulatory Activity.

A novel pectic polysaccharide (HPP-1) with high immunomodulatory activity was extracted and isolated from the immature honey pomelo fruit (Citrus grandis). Characterization of its chemical structure indicated that HPP-1 had a molecular weight of 59,024 D. In addition, HPP-1 was primarily composed of rhamnose, arabinose, fucose, mannose, and galactose at a molar ratio of 1.00:11.12:2.26:0.56:6.40. Fourier-transform infrared spectroscopy, periodic acid oxidation, and Smith degradation results showed that HPP-1 had α- and ß-glycosidic linkages and 1 → 2, 1 → 4, 1 → 6, and 1 → 3 glycosidic bonds. 13C NMR and 1H NMR analyses revealed that the main glycogroups included 1,4-D-GalA, 1,6-ß-D-Gal, 1,6-ß-D-Man, 1,3-α-L-Ara, and 1,2-α-L-Rha. Immunomodulatory bioactivity analysis using a macrophage RAW264.7 model in vitro revealed that NO, TNF-α, and IL-6 secretions were all considerably increased by HPP-1. Moreover, RT-PCR results showed that HPP-1-induced iNOS, TNF-α, and IL-6 expression was significantly increased in macrophages. HPP-1-mediated activation in macrophages was due to the stimulation of the NF-κB and MAPK signaling pathways based on western blot analyses. HPP-1 extracted from immature honey pomelo fruit has potential applications as an immunomodulatory supplement.

New pectic polysaccharides from Codonopsis pilosula and Codonopsis tangshen: structural characterization and cellular antioxidant activities.

BACKGROUND: Codonopsis pilosula and Codonopsis tangshen are plants widely used in traditional Chinese medicine. Two pectic polysaccharides from the roots of C. pilosula and C. tangshen named as CPP-1 and CTP-1 were obtained by boiling water extraction and column chromatography. RESULTS: The core structures of both CPP-1 and CTP-1 comprise the long homogalacturonan region (HG) as the backbone and the rhamnogalacturonan I (RG-I) region as the side chains. CPP-1 has methyl esterified galacturonic acid units and a slightly lower molecular weight than CTP-1. Biological testing suggested that CPP-1 and CTP-1 can protect IPEC-J2 cells against the H2 O2 -induced oxidative stress by up-regulating nuclear factor-erythroid 2-related factor 2 and related genes in IPEC-J2 cells. The different antioxidative activities of polysaccharides from different source of C. pilosula may be result of differences in their structures. CONCLUSION: All of the results indicated that pectic polysaccharides CPP-1 and CTP-1 from different species of C. pilosula roots could be used as a potential natural antioxidant source. These findings will be valuable for further studies and new applications of pectin-containing health products. © 2021 Society of Chemical Industry.

Developmental changes in collenchyma cell-wall polysaccharides in celery (Apium graveolens L.) petioles.

BACKGROUND: Collenchyma cells occur widely in eudicotyledons and provide mechanical support for growing organs. At maturity, the cells are elongated and have thick, non-lignified walls, which in celery contain cellulose and pectic polysaccharides, together with xyloglucans and heteroxylans and heteromannans. A previous study suggested that at least some of the collenchyma cell wall in celery is laid down after expansion has stopped and is thus secondary. In the present study, we re-examined this. We used chemical analysis and immunomicroscopy to determine changes in the polysaccharide compositions of these walls during development. Additionally, solid-state NMR spectroscopy was used to examine changes in polysaccharide mobilities during development. RESULTS: We showed the collenchyma walls are deposited only during cell expansion, i.e. they are primary walls. During cell-wall development, analytical and immunomicroscopy studies showed that within the pectic polysaccharides there were no overall changes in the proportions of homogalacturonans, but there was a decrease in their methyl esterification. There was also a decrease in the proportions of the (1 → 5)-α-L-arabinan and (1 → 4)-ß-D-galactan side chains of rhamnogalacturonan I. The proportions of cellulose increased, and to a lesser extent those of xyloglucans and heteroxylans. Immunomicroscopy showed the homogalacturonans occurred throughout the walls and were most abundant in the middle lamellae and middle lamella junctions. Although the (1 → 4)-ß-D-galactans occurred only in the rest of the walls, some of the (1 → 5)-α-L-arabinans also occurred in the middle lamellae and middle lamella junctions. During development, the location of the xyloglucans changed, being confined to the middle lamellae and middle lamella junctions early on, but later occurred throughout the walls. The location of the heteroxylans also changed, occurring mostly in the outer walls in young cells, but were more widely distributed in mature cells. Solid-state NMR spectroscopy showed that particularly cellulose, but also homogalacturonans, decreased in mobility during development. CONCLUSIONS: Our studies showed that celery collenchyma cell walls are primary and that during their development the polysaccharides undergo dynamic changes. Changes in the mobilities of cellulose and homogalacturonans were consistent with the cell walls becoming stiffer as expansion ceases.

Pectic polysaccharides extracted from Rauvolfia verticillata (Lour.) Baill. var. hainanensis Tsiang ameliorate ulcerative colitis via regulating the MAPKs and NF-κB pathways in dendritic cells.

This study was to investigate the effects and mechanisms of pectic polysaccharides (PP) extracted from Rauvolfia verticillata (Lour.) Baill. var. hainanensis Tsiang on dextran sulphate sodium (DSS)-induced ulcerative colitis (UC). Eighty female BALB/c mice were randomly divided into four groups: Control, DSS, DSS + salicylazosulfapyridine (SASP), and DSS+ PP. The disease activity index (DAI), overall physical activity, and blood stool were monitored daily to evaluate severity of UC. Histological scores of the colon were observed. The expression of nuclear factor κB (NF-κB) and mitogen-activated protein kinase (MAPKs) pathways in colon tissues and bone marrow-derived dendritic cells (DCs) was assessed by western blot, immunohistochemistry, electrophoretic mobility shift assay (EMSA) and real time polymerase chain reaction (RT-PCR). Cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The overall physical activity, DAI and histological scores decreased in DSS+SASP and DSS+PP groups, compared with the DSS-alone group. Also, tumour necrosis factor α (TNF-α) and interleukin 6 (IL-6) reduced significantly while the expression of IκBα was up-regulated, extracellular signal-regulated kinase (ERK), Jun N-terminal kinase (JNK) and p38 were activated, in DSS+SASP and DSS+PP groups. PP inhibited activation of MAPKs and NF-κB pathways in the bone-marrow-derived DCs. In conclusion, PP significantly ameliorated murine DSS-induced UC model, via regulation of MAPKs and NF-κB pathways in DCs.

Malting process has minimal influence on the structure of arabinan-rich rhamnogalacturonan pectic polysaccharides from chickpea (Cicer arietinum L.) hull.

The objective of the study was to determine the changes brought about by malting/germination on the pectic polysaccharides (PP's), the major components of soluble fibres present in chickpea (Cicer arietinum L.) hull. Chickpea hull PP's were extracted sequentially using ammonium oxalate (AO) and ethylenediaminetetraacetic acid (EDTA), and a comparative study was conducted in native (unprocessed, N-PP) and after subjecting to 48 h malting process (M-PP). Malting process did not show a significant change in the respective yields of AO and EDTA extracted pectic polysaccharides. The degree of esterification of N-PP-EDTA through Fourier transform infrared spectroscopy was found to be five times (~ 21%) more than N-PP-AO (~ 4%). AO isolated PP's have more complexed xylogalacturonan with relatively more galactan side chains compared to EDTA isolated PPs. Proton (1H) nuclear magnetic resonance result further suggested the occurrence of arabinan rich rhamnogalacturonan in chickpea hull and malting process showed no significant changes in structure.

Boron bridging of rhamnogalacturonan-II is promoted in vitro by cationic chaperones, including polyhistidine and wall glycoproteins.

Dimerization of rhamnogalacturonan-II (RG-II) via boron cross-links contributes to the assembly and biophysical properties of the cell wall. Pure RG-II is efficiently dimerized by boric acid (B(OH)3 ) in vitro only if nonbiological agents for example Pb(2+) are added. By contrast, newly synthesized RG-II domains dimerize very rapidly in vivo. We investigated biological agents that might enable this. We tested for three such agents: novel enzymes, borate-transferring ligands and cationic 'chaperones' that facilitate the close approach of two polyanionic RG-II molecules. Dimerization was monitored electrophoretically. Parsley shoot cell-wall enzymes did not affect RG-II dimerization in vitro. Borate-binding ligands (apiose, dehydroascorbic acid, alditols) and small organic cations (including polyamines) also lacked consistent effects. Polylysine bound permanently to RG-II, precluding electrophoretic analysis. However, another polycation, polyhistidine, strongly promoted RG-II dimerization by B(OH)3 without irreversible polyhistidine-RG-II complexation. Likewise, partially purified spinach extensins (histidine/lysine-rich cationic glycoproteins), strongly promoted RG-II dimerization by B(OH)3 in vitro. Thus certain polycations, including polyhistidine and wall glycoproteins, can chaperone RG-II, manoeuvring this polyanionic polysaccharide domain such that boron-bridging is favoured. These chaperones dissociate from RG-II after facilitating its dimerization, indicating that they act catalytically rather than stoichiometrically. We propose a natural role for extensin-RG-II interaction in steering cell-wall assembly.

Pectic polysaccharides are attacked by hydroxyl radicals in ripening fruit: evidence from a fluorescent fingerprinting method.

BACKGROUND AND AIMS: Many fruits soften during ripening, which is important commercially and in rendering the fruit attractive to seed-dispersing animals. Cell-wall polysaccharide hydrolases may contribute to softening, but sometimes appear to be absent. An alternative hypothesis is that hydroxyl radicals ((•)OH) non-enzymically cleave wall polysaccharides. We evaluated this hypothesis by using a new fluorescent labelling procedure to 'fingerprint' (•)OH-attacked polysaccharides. METHODS: We tagged fruit polysaccharides with 2-(isopropylamino)-acridone (pAMAC) groups to detect (a) any mid-chain glycosulose residues formed in vivo during (•)OH action and (b) the conventional reducing termini. The pAMAC-labelled pectins were digested with Driselase, and the products resolved by high-voltage electrophoresis and high-pressure liquid chromatography. KEY RESULTS: Strawberry, pear, mango, banana, apple, avocado, Arbutus unedo, plum and nectarine pectins all yielded several pAMAC-labelled products. GalA-pAMAC (monomeric galacturonate, labelled with pAMAC at carbon-1) was produced in all species, usually increasing during fruit softening. The six true fruits also gave pAMAC·UA-GalA disaccharides (where pAMAC·UA is an unspecified uronate, labelled at a position other than carbon-1), with yields increasing during softening. Among false fruits, apple and strawberry gave little pAMAC·UA-GalA; pear produced it transiently. CONCLUSIONS: GalA-pAMAC arises from pectic reducing termini, formed by any of three proposed chain-cleaving agents ((•)OH, endopolygalacturonase and pectate lyase), any of which could cause its ripening-related increase. In contrast, pAMAC·UA-GalA conjugates are diagnostic of mid-chain oxidation of pectins by (•)OH. The evidence shows that (•)OH radicals do indeed attack fruit cell wall polysaccharides non-enzymically during softening in vivo. This applies much more prominently to drupes and berries (true fruits) than to false fruits (swollen receptacles). (•)OH radical attack on polysaccharides is thus predominantly a feature of ovary-wall tissue.

Physiologically induced changes in bound phenolics and antioxidants, DNA/cytoprotective potentials in pectic poly/oligosaccharides of tomato (Solanum lycopersicum).

BACKGROUND: Antioxidant, cyto/DNA protective potentials are known to offer significant protection against free radical induced injury to cells or tissues and cellular damages that are envisaged in various diseases including chronic diseases like cancer, diabetes, etc, while galectin-3 inhibitory potentials are known to block or delay the process of metastasis in cancer. Antioxidant, cyto/DNA protection and galectin-3 inhibitory potentials were examined in pectic polysaccharides (PPs) and pectic oligosaccharides (POs) from four types of two varieties of tomatoes such as Sour (Mallika local variety) raw (SrRT-SrRTPP, SrRTPO), Sour ripe (SrRIT-SrRITPP, SrRITPO), Sweet (Rashmi local variety) raw (SwRT-SwRTPP, SwRTPO) and Sweet ripe (SwRIT-SwRITPP and SwRITPO). RESULTS: Results indicate that unripe PPs and POs show approximately four- to five-fold better galectin-3 inhibitory property than ripe ones. An approximately nine- to 10-fold increase in galectin-3 inhibitory activity in sour variety was observed. The IC50 as determined by free radical scavenging (FRS), red blood cell (RBC) and DNA protection assays revealed reduction in FRS and RBC protective potencies in pectic oligosaccharides (POs) than pectic polysaccharides (PPs), supporting the fact that phenolics contribute towards these activities. Loss of activity could be attributed to the hydrolysis of certain phenolics during the ripening process as well as during conversion of PPs to POs. CONCLUSION: This study, for the first time, showed changes in bioactivity profiling in unripened and ripened conditions in tomato. Precise alterations in biomolecular components, such as bound cinnamyl/ferulyl and vanillic acid derivatives, along with alterations in sugar composition that reflect changes in antioxidants, cyto/DNA protective and antimetastatic potentials, have been delineated. © 2016 Society of Chemical Industry.

Sugar composition of the pectic polysaccharides of charophytes, the closest algal relatives of land-plants: presence of 3-O-methyl-D-galactose residues.

BACKGROUND AND AIMS: During evolution, plants have acquired and/or lost diverse sugar residues as cell-wall constituents. Of particular interest are primordial cell-wall features that existed, and in some cases abruptly changed, during the momentous step whereby land-plants arose from charophytic algal ancestors. METHODS: Polysaccharides were extracted from four charophyte orders [Chlorokybales (Chlorokybus atmophyticus), Klebsormidiales (Klebsormidium fluitans, K. subtile), Charales (Chara vulgaris, Nitella flexilis), Coleochaetales (Coleochaete scutata)] and an early-diverging land-plant (Anthoceros agrestis). 'Pectins' and 'hemicelluloses', operationally defined as extractable in oxalate (100 °C) and 6 m NaOH (37 °C), respectively, were acid- or Driselase-hydrolysed, and the monosaccharides analysed chromatographically. One unusual monosaccharide, 'U', was characterized by (1)H/(13)C-nuclear magnetic resonance spectroscopy and also enzymically. KEY RESULTS: 'U' was identified as 3-O-methyl-D-galactose (3-MeGal). All pectins, except in Klebsormidium, contained acid- and Driselase-releasable galacturonate, suggesting homogalacturonan. All pectins, without exception, released rhamnose and galactose on acid hydrolysis; however, only in 'higher' charophytes (Charales, Coleochaetales) and Anthoceros were these sugars also efficiently released by Driselase, suggesting rhamnogalacturonan-I. Pectins of 'higher' charophytes, especially Chara, contained little arabinose, instead possessing 3-MeGal. Anthoceros hemicelluloses were rich in glucose, xylose, galactose and arabinose (suggesting xyloglucan and arabinoxylan), none of which was consistently present in charophyte hemicelluloses. CONCLUSIONS: Homogalacturonan is an ancient streptophyte feature, albeit secondarily lost in Klebsormidium. When conquering the land, the first embryophytes already possessed rhamnogalacturonan-I. In contrast, charophyte and land-plant hemicelluloses differ substantially, indicating major changes during terrestrialization. The presence of 3-MeGal in charophytes and lycophytes but not in the 'intervening' bryophytes confirms that cell-wall chemistry changed drastically between major phylogenetic grades.

Differences between easy- and difficult-to-mill chickpea (Cicer arietinum L.) genotypes. Part III: free sugar and non-starch polysaccharide composition.

BACKGROUND: Parts I and II of this series of papers identified several associations between the ease of milling and the chemical compositions of different chickpea seed fractions. Non-starch polysaccharides were implicated; hence, this study examines the free sugars and sugar residues. RESULTS: Difficult milling is associated with: (1) lower glucose and xylose residues (less cellulose and xyloglucans) and more arabinose, rhamnose and uronic acid in the seed coat, suggesting a more flexible seed coat that resists cracking and decortication; (2) a higher content of soluble and insoluble non-starch polysaccharide fractions in the cotyledon periphery, supporting a pectic polysaccharide mechanism comprising arabinogalacturonan, homogalacturonan, rhamnogalalcturonan, and glucuronan backbone structures; (3) higher glucose and mannose residues in the cotyledon periphery, supporting a lectin-mediated mechanism of adhesion; and (4) higher arabinose and glucose residues in the cotyledon periphery, supporting a mechanism involving arabinogalactan-proteins. CONCLUSION: This series has shown that the chemical composition of chickpea does vary in ways that are consistent with physical explanations of how seed structure and properties relate to milling behaviour. Seed coat strength and flexibility, pectic polysaccharide binding, lectins and arabinogalactan-proteins have been implicated. Increased understanding in these mechanisms will allow breeding programmes to optimise milling performance in new cultivars.

Utilization of electron beam irradiation pretreatment for the extraction of pectic polysaccharides from Diaphragma juglandis fructus: Structural, physicochemical, and functional properties.

The effects of electron beam irradiation (EBI) pretreatment on the alkaline extraction of pectic polysaccharides from Diaphragma juglandis fructus (DJF) are highly dependent on the irradiation dosage. Comprehensive characterizations encompassing physicochemical, structural, and functional properties were conducted on crude pectic polysaccharide extract from DJF subjected to various EBI doses. EBI pretreatment significantly increased the yields of crude pectic polysaccharides extract (increasing by 41.89 %), also facilitating the extraction of uronic acid, RG-I structure, and protein content, despite causing a decrease in total sugar content. EBI pretreatment induced the degradation of pectin, resulting in decreased molecular weight, particle size, crystallinity, viscosity, thermal stability, and water holding capacity, while enhancing solubility and oil holding capacity. Variations in physicochemical and structural properties induced by different EBI doses influenced the functional activities of DJF pectic polysaccharides. Low-dose EBI (at 5 kGy) pretreatment markedly improved the emulsifying activity/stability (increasing by 20.82/74.10 %) and ABTS/DPPH radical scavenging activity (increasing by 27.91/12.40 %), whereas high-dose EBI pretreatment (50 kGy) greatly enhanced foaming capacity/stability (increasing by 259.99/175.56 %). These findings provide a novel regulatory strategy for the functional activity of pectic polysaccharides.

Structure of KOH-soluble polysaccharides from сoniferous greens of Norway spruce (Picea abies): The pectin-xylan-AGPs complex. Part 2.

Polymers containing arabinoglucuronoxylan, fucogalactoxyglucan, pectin and arabinogalactan proteins were obtained from PAK isolated from Norway spruce with 7 % KOH. The pectin core of PAK-I2-F-1 and PAK-I2-F-2 was dominated by RG-I, as treatment with 1,4-α-D-polygalacturonase resulted in almost complete removal of homogalacturonan. Interestingly, the above has not affected the co-fractionation of arabinoglucuronoxylan (AGX), arabinogalactan proteins and rhamnogalacturonan I (RG-I). Since pectin was mainly represented by RG-I, we concluded that xylan is specifically associated with RG-I. Correlations in the HMBC spectrum demonstrate intermolecular interactions between the α-L-Rhap (RG-I) and the Xyl (xylan), indicating a covalently bound AGX:RG-I complex via the Xyl-(1→4)-Rha bond: …→2)-[(2,4-ß-D-Xylp)-(1→4)]-[(α-D-GalpA-(1→2)]-α-L-Rhap-(1→4)-α-D-GalpA-(1→…. In PAK-H1-1-F-1 and PAK-H1-1-F-2, parts of RG-I and xylan were removed by enzymolysis. Part of the xylan was probably attached to the above-mentioned RG-I blocks. The removal of part of RG-I, xylan and the disappearance of the signal in the HMBC spectrum indicating the bond between RG-I and xylan confirms that part of the arabinoglucuronoxylan is covalently bound to RG-I. The observed glycosidic linkage contradicts the dominant PCW model in which pectin and hemicellulose polysaccharide networks are considered as independent components. It can be concluded that alkali-soluble xylan from Norway spruce was detected both in the free state and covalently bound to pectin.

Pectins Rich in RG-I Extracted from Watermelon Peel: Physicochemical, Structural, Emulsifying, and Antioxidant Properties.

RG-I pectin has excellent health benefits, but its raw materials are relatively scarce, and its complex structure often breaks down its side-chain structure during the extraction process. In this study, the physicochemical and antioxidant properties of a branched-chain-rich pectin gained from watermelon peel were demonstrated, and the structure-function relationships of RG-I-enriched pectin and emulsification properties were investigated. Fourier transform infrared spectroscopy, high-performance anion exchange chromatography, high-performance gel permeation chromatography, nuclear magnetic resonance spectroscopy, and methylation analyses reveal it as acetylated, low-methoxylated pectin, rich in RG-I side chains (MW: 1991 kDa, RG-I = 66.17%, methylation degree: 41.45%, (Ara + Gal)/Rha: 20.59%). RPWP outperforms commercial citrus pectin in emulsification and stability, significantly preventing lipid oxidation in emulsions. It also exhibits free radical scavenging abilities, contributing to its effectiveness in preventing lipid oxidation. Emulsions made with RPWP show higher viscosity and form a weak gel network (G' > G″), enhancing stability by preventing phase separation. These findings position watermelon peel as a good source of RG-I pectin and deepen our understanding of RPWP behavior in emulsion systems, which may be useful in the food and pharmaceutical fields.

Structural characteristics of cell wall pectic polysaccharides from wampee and their decreased binding with pectinase by wampee polyphenol.

To investigate the structural characteristics of cell wall pectic polysaccharides from wampee, water soluble pectin (WSP), chelator-soluble pectin (CSP) and sodium carbonate-soluble pectin (SSP) were purified. And the inhibitory effects of wampee polyphenol (WPP) on pectinase when these cell wall pectic polysaccharides were used as substrates were also explored. Purified WSP (namely PWSP) had the lowest molecular weight (8.47 × 105 Da) and the highest GalA content (33.43%). While purified CSP (called PCSP) and SSP contained more abundant rhamnogalacturonan I side chains. All of them were low-methoxy pectin (DE < 50%). Enzyme activity and kinetics analysis showed that the inhibition of pectinase by wampee polyphenol was reversible and mixed type. When SSP was used as the substrate, WPP had the strongest inhibition (IC50 = 1.96 ± 0.06 mg/mL) on pectinase. Fluorescence quenching results indicated that WPP inhibited enzyme activity by interacting with substrates and enzymes. Therefore, WPP has the application potential in controlling softening of fruits and vegetables.

Effect of hydrochloric acid and citric acid with ultrasound processing on characteristics of superfine-ground pectic polysaccharides from okra (Abelmoschus esculentus L.) peel.

The structural properties and biological activities of okra pectic polysaccharides (OPs) were impacted by various extraction methods. Based on commonly grinding (40, 100 meshes) and superfine grinding okra powders, two extraction solvents (hydrochloric acid, HA; citric acid, CA) were used firstly. Next, the extraction yield, physical and chemical properties, molecular structure and functional properties of OPs were analyzed by non-ultrasonic treatment and ultrasound-assisted superfine grinding method. The outcomes demonstrated that the extraction yield of OPs rose as the particle size of the powder decreased. HA-OPs had higher molecular weight (Mw), apparent viscosity and emulsification ability than CA-OPs. CA-OPs had higher esterification degree (DE), solubility and total sugar content, and higher amounts of rhamnogalacturonan-I (RG-I) segments. Compared with OPs without ultrasound-assisted extraction, ultrasound-assisted superfine grinding extraction exhibited higher sugar content, antioxidant capacity, emulsification ability, lower Mw, DE and apparent viscosity. Finally, the correlation between structure and function of OPs was further quantified. The antioxidant capacity was positively correlated with RG-I content, and negatively correlated with DE and Mw. The emulsification ability was mainly positively correlated with the GlcA of OPs. This study provides a theoretical basis for the development of OPs foods with clear structure-function relationship, which would be instructive for the application of OPs in food and cosmetics.

Effects of extraction methods on the physicochemical properties and functionalities of pectic polysaccharides from burdock (Arctium lappa L.).

In this work, the effects of four different extraction methods, acid (HCl), alkali (NaOH), enzymes (cellulase/pectinase), and buffer (pH 7.0) on the physicochemical properties and functionalities of burdock pectin were systematically investigated and compared. Buffer extraction gave a low yield (2.8 %) and is therefore limited in its application. The acid treatment hydrolyzed the neutral sidechains and gave a homogalacturonan content of 72.6 %. By contrast, alkali and enzymes preserved the sidechains while degrading the polygalacturonan backbone, creating a rhamnogalacturonan-I dominant structure. The branched structure, low molecular weight, and high degree of methylation (42.3 %) contributed to the interfacial adsorption, emulsifying capacity, and cellular antioxidant activity of the enzyme-extracted product. For the acid-extracted product, the strong intramolecular electrostatic repulsion restricted the formation of a contact interface to prevent coalescence of the emulsion. In addition, they did not have sufficient reducing ends to scavenge free radicals. Although a high branching size (5.0) was adopted, the low degree of methylation (19.5 %) affected the emulsifying capacity of the alkali-extracted products. These results provide useful information for pectic polysaccharides production with tailored properties.