Exploring the partial degradation of polysaccharides: Structure, mechanism, bioactivities, and perspectives.

Polysaccharides are promising biomolecules with lowtoxicity and diverse bioactivities in food processing and clinical drug development. However, an essential prerequisite for their applications is the fine structure characterization. Due to the complexity of polysaccharide structure, partial degradation is a powerful tool for fine structure analysis, which can effectively provide valid information on the structure of backbone and branching glycosidic fragments of complex polysaccharides. This review aims to conclude current methods of partial degradation employed for polysaccharide structural characterization, discuss the molecular mechanisms, and describe the molecular structure and solution properties of degraded polysaccharides. In addition, the effects of polysaccharide degradation on the conformational relationships between the molecular structure and bioactivities, such as antioxidant, antitumor, and immunomodulatory activities, are also discussed. Finally, we summarize the prospects and current challenges for the partial degradation of polysaccharides. This review will be of great value for the scientific elucidation of polysaccharide fine structures and potential applications.

Recent developments in Hericium erinaceus polysaccharides: extraction, purification, structural characteristics and biological activities.

Hericium erinaceus (H. erinaceus), an edible mushroom with medicinal value, has a long history of usage in China and other oriental countries. Polysaccharide is supposed to be one of the major bioactive compounds in H. erinaceus, which possesses immunomodulating, anti-cancer, antioxidant, gastroprotection and intestinal health promotion, neuroprotective, hepatoprotective, antihpyerglycemic and hypolipidemic activities. In this review, the current advancements on extraction, purification, structural characteristics and biological activities of polysaccharide from different sources (fruiting body, mycelium and culture broth) of H. erinaceus were summarized. Among these aspects, summaries of the structural characteristics focused on the purified polysaccharides. Meanwhile, comparisons on the structural characteristics among the purified polysaccharides obtained from above three sources were made. Moreover, their biological activities were introduced on the basis of in vivo and in vitro experiments, and some possible action mechanisms were listed. Furthermore, the structure-activity relationship of the polysaccharide was discussed. New perspectives for the future work of Hericium erinaceus polysaccharide were also proposed. HIGHLIGHTS Extraction, purification, structural characteristics and biological activities of Hericium erinaceus polysaccharide (HEP) were summarized. Structural characteristics of the purified polysaccharides from different sources (fruiting body, mycelium and culture broth) of Hericium erinaceus were summarized and compared. Structure-activity relationship of HEP was discussed, and new perspectives for the future work of this polysaccharide were proposed.

Pterostilbene suppresses human endometrial cancer cells in vitro by down-regulating miR-663b.

Resveratrol has long been known as an antioxidant and a chemopreventive agent. Similar to resveratrol, pterostilbene (PT) is also a phenolic compound extracted from the Vitis species. However, there are few studies on the antitumor effect of PT. Thus, we investigated the effects of PT on the endometrial cancer (EC) cells in vitro and the related molecular mechanisms. Treatment of EC cell lines HTB-111 and Ishikawa with PT (25-100 µmol/L) dose-dependently suppressed the cell viability and induced apoptosis. Using miR microarrays, we examined the miR expression profile in Ishikawa cells with or without PT, and revealed that miR-663b was the most decreased in PT-treated Ishikawa cells. Furthermore, we predicted and verified that the pro-apoptosis factor BCL2L14 is the direct target of miR-663b. Over-expression of miR-663b and knock-down of BCL2L14 counteracted the suppressing effects of PT on HTB-111 and Ishikawa cells. In addition, we evaluated the miR-663b levels in EC tissues of 51 patients using an in situ hybridization technique. With the median of the score of miR-663b as a cut-off value, these EC patients were divided into two groups, and the patients with high miR-663b expression had significantly poor prognosis.

Gamma-Aminobutyric Acid Increases the Production of Short-Chain Fatty Acids and Decreases pH Values in Mouse Colon.

Gamma-Aminobutyric acid (GABA) could regulate physiological functions in the gastrointestinal tract. The present study aimed to investigate the effect of GABA on colon health in mice. The female Kunming mice were given GABA at doses of 5, 10, 20 and 40 mg/kg/d for 14 days. Afterwards, the short-chain fatty acids (SCFAs) concentrations, pH values, colon index, colon length and weight of colonic and cecal contents were determined to evaluate the effects of GABA on colon health. The results showed that intake of GABA could increase the concentrations of acetate, propionate, butyrate and total SCFAs in colonic and cecal contents, as well as the weight of colonic and cecal contents. The colon index and length of the 40 mg/kg/d GABA-treated group were significantly higher than those of the control group (p < 0.05). In addition, decrease of pH values in colonic and cecal contents was also observed. These results suggest that GABA may improve colon health.

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.

Recent advances in the biosynthesis of fungal glucan structural diversity.

Glucans are the most abundant class of macromolecule polymers in fungi, which are commonly found in Ascomycota and Basidiomycota. Fungal glucans are not only essential for cell integrity and function but also crucial for the immense industrial interest in high value applications. They present a variety of structural characteristics at the nanoscale due to the high regulation of genes and the involvement of stochastic processes in synthesis. However, although recent findings have demonstrated the genes of glucans synthesis are relatively conserved across diverse fungi, the formation and organization of diverse glucan structures is still unclear in fungi. Here, we summarize the structural features of fungal glucans and the recent developments in the mechanisms of glucans biosynthesis. Furthermore, we propose the engineering strategies of targeted glucan synthesis and point out the remaining challenges in the synthetic process. Understanding the synthesis process of diverse glucans is necessary for tailoring high value glucan towards specific applications. This engineering strategy contributes to enable the sustainable and efficient production of glucan diversity.

Ascorbic acid-mediated reduction of arabinoxylan viscosity through free radical reactions.

Arabinoxylan (AX) is a potential natural food additive that can enhance the textural properties of food. However, the addition of ascorbic acid (AA) can easily lead to a decrease in the viscosity of AX, which poses a challenge in the development of AX-rich foods. Therefore, the purpose of this study is to elucidate the mechanisms behind the reduction in AX viscosity in the presence of AA. The results indicated that AA could reduce the apparent viscosity and molecular weight of AX without significantly affecting the monosaccharide composition, suggesting a potential mechanism related to the cleavage of AX glycosidic bonds. Interestingly, free radicals were present in the reaction system, and the generation of free radicals under different conditions was consistent with the reduction in apparent viscosity of AX. Furthermore, the reduction in AX apparent viscosity by AA was influenced by various factors including AA concentration, reaction time, temperature, pH, and metal ions. These findings suggested that the mechanism of AX degradation may be due to AA-induced free radical generation, leading to non-selective attacks on glycosidic bonds. Therefore, this study revealed that the potential mechanism behind the reduction in AX viscosity induced by AA involved the generation of ascorbic acid radicals.

UCA1 Inhibits NKG2D-mediated Cytotoxicity of NK Cells to Breast Cancer.

BACKGROUND: Natural killer cells play important roles in tumor immune surveillance, and cancer cells must resist this surveillance in order to progress and metastasise. INTRODUCTION: The study aimed to explore the mechanism of how breast cancer cells become resistant to the cytotoxicity of NK cells. METHODS: We established NK-resistant breast cancer cells by exposing MDA-MB-231 cells and MCF-7 cells to NK92 cells. Profiles of lncRNA were compared between the NK-resistant and parental cell lines. Primary NK cells were isolated by MACS, and the NK attacking effect was tested by non-radioactive cytotoxicity. The change in lncRNAs was analyzed by Gene-chip. The interaction between lncRNA and miRNA was displayed by Luciferase assay. The regulation of the gene was verified by QRT-PCR and WB. The clinical indicators were detected by ISH, IH, and ELISA, respectively. RESULTS: UCA1 was found to be significantly up-regulated in both NK-resistant cell lines, and we confirmed such up-regulation on its own to be sufficient to render parental cell lines resistant to NK92 cells. We found that UCA1 up-regulated ULBP2 via the transcription factor CREB1, while it up-regulated ADAM17 by "sponging" the miR-26b-5p. ADAM17 facilitated the shedding of soluble ULBP2 from the surface of breast cancer cells, rendering them resistant to killing by NK cells. UCA1, ADAM17, and ULBP2 were found to be expressed at higher levels in bone metastases of breast cancer than in primary tumors. CONCLUSION: Our data strongly suggest that UCA1 up-regulates ULBP2 expression and shedding, rendering breast cancer cells resistant to killing by NK cells.

Dynamics of α-glucan from Agrocybe cylindracea water extract at different developmental stages and its structure characteristics.

Polysaccharides are the important bioactive macromolecules in Agrocybe cylindracea, but their changes are as yet elusive during developmental process. This study investigated the dynamic changes of polysaccharides from A. cylindracea fruiting body water extract at four developmental stages and its structure characteristics. Results revealed that the polysaccharides from A. cylindracea water extract significantly increased at the pileus expansion stage and the increased fraction could be α-glucan. The further purification and identification indicated that this α-glucan was a glycogen. It had typical morphology of ß particles with a molecular weight of 1375 kDa. Its backbone comprised α-D-(1 â†’ 4)-Glcp and α-D-(1 â†’ 4,6)-Glcp residues at a ratio of 5:1, terminated by α-D-Glcp residue. Rheological behavior suggested that it was a Newtonian fluid at the concentration of 1 %. In addition, despite both the glycogen and natural starch were composed of D-glucose, they exhibited the entirely distinct Maltese cross characteristic and unique crystalline structure. This study is the first to demonstrate the presence of abundant glycogen in the pileus expansion stage of A. cylindracea, which provides new insights on the change patterns of fungal polysaccharides.

Changes of the Physicochemical Properties and Structural Characteristics of Alkali-Extracted Polysaccharides from Agrocybe cylindracea Across the Growth Process.

Polysaccharides derived from Agrocybe cylindracea have been demonstrated to exhibit various bioactivities. However, studies on their structural characteristics during the growth process are limited. This study aimed to compare the physicochemical properties and structural characteristics of alkali-extracted polysaccharides from A. cylindracea fruiting bodies (JACP) across four growth stages. Results showed that the extraction yields and protein levels of JACP declined along with the growth of A. cylindracea, while the contents of neutral sugar and glucose increased significantly. However, JACP exhibited structural characteristics similar to those across the four stages. Four polysaccharide subfractions were isolated from each growth stage, including JACP-Et30, JACP-Et50, JACP-Et60, and JACP-Et70. JACP-Et30 from the four stages and JACP-Et50 from the initial three stages were identified as heteroglucans with ß-1,3-d-Glcp and ß-1,6-d-Glcp residues as main chains, respectively. However, other subfractions were considered as ß-1,6-d-glucans containing minor glucuronic acid. These subfractions were predominantly replaced by Glcp residues at the O-3 and O-6 positions. Overall, while JACP exhibited variable physicochemical properties, its structural characteristics remained stable during the growth process, offering new insights into its potential applications in the food and medicinal industries.

Insights into dynamic evolution of glucuronofucogalactoglucan from water extract of Agrocybe cylindracea during maturation.

This study explored the physicochemical properties and structural characteristics of Agrocybe cylindracea polysaccharides at four developmental stages, as well as their dynamic evolution during maturation. Results showed that the polysaccharides from A. cylindracea water extract exhibited similar structural characteristics across all four maturity stages, despite a significant reduction in yields. Four water-soluble heteroglycans, including one high molecular weight (ACPM-Et50-I) and three low molecular weight (ACPM-Et50-II, ACPM-Et60, ACPM-Et80), were isolated from A. cylindracea at each maturity stage. ACPM-Et50-I was identified as branched heterogalactans, while ACPM-Et60 and ACPM-Et80 were branched heteroglucans. However, ACPM-Et50-II was characterized as a branched glucuronofucogalactoglucan at the tide-turning stage but a glucuronofucoglucogalactan at the pileus expansion stage due to the increase of its α-(1 â†’ 6)-D-Galp. In general, although the structural skeletons of most A. cylindracea heteroglycans were similar during maturation as shown by their highly consistent glycosyl linkages, there were still differences in the distribution of some heteroglucans. This work has for the first time reported a glucuronofucogalactoglucan in A. cylindracea and its dynamic evolution during maturation, which may facilitate the potential application of A. cylindracea in food and biomedicine industries.

Development of soy protein isolate gels added with Tremella polysaccharides and psyllium husk powder as 3D printing inks for people with dysphagia.

The aim of this study was to investigate the feasibility of soy protein isolate (SPI) gels added with Tremella polysaccharides (TPs) and psyllium husk powder (PHP) as 3D printing inks for developing dysphagia-friendly food and elucidate the potential mechanism of TPs and PHP in enhancing the printing and swallowing performance of SPI gels. The results indicated that the SPI gels with a TP : PHP ratio of 3 : 7 could be effectively used as printing inks to manufacture dysphagia-friendly food. The addition of TPs increased the free water content, resulting in a decrease in the viscosity of the SPI gels, which, in turn, reduced the line width of the 3D-printed product and structural strength of the gel system. The addition of PHP increased disulfide bond interactions and excluded volume interactions, which determined the mechanical strength of SPI gels and increased the line width of the printed product. The synergistic effects between TPs and PHP improved the printing precision and structural stability. This study presents meaningful insights for the utilization of 3D printing in the creation of dysphagia-friendly food using protein-polysaccharide complexes.

Comprehensive analysis in the nutritional composition, phenolic species and in vitro antioxidant activities of different pea cultivars.

In this study, ten pea (Pisum sativum L.) varieties were compared in their nutrient composition, phenolic compounds, antioxidant properties and their diversity were deciphered by multivariate analysis of correlation analysis and principal component analysis (PCA). The ten pea cultivars are rich in nutrients with different contents in lipid (0.57 to 3.52%), dietary fiber (11.34 to 16.13%), soluble sugar (17.53 to 23.99%), protein (19.75 to 26.48%) and starch (32.56 to 48.57%). Through the UPLC-QTOF-MS and HPLC-QQQ-MS/MS analysis, the ethanol extracts of ten peas mainly included 12 kinds of phenolic substances and showed good antioxidant activities on the 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC). The phenolic content and protocatechuic acid showed a positive correlation with antioxidant capacity. All results provide theoretical basis for the development and rational application of different varieties of peas and their related products.

Evaluation of the "Relative Ordered Structure of Hericium erinaceus Polysaccharide" from Different Origins: Based on Similarity and Dissimilarity.

Polysaccharides are organic compounds widely distributed in nature, but structural order and disorder remain a formidable problem. In this study, based on the theoretical framework of the "relative ordered structure of polysaccharide" proposed in our previous work, the structural order of Hericium erinaceus polysaccharides from different regions was evaluated by FT-IR, methylation analysis, and 1H NMR spectroscopy combined with chemometric methods. The results of principal component analysis and heatmap cluster analysis revealed that 18-subfractions exhibit four different structural types with representative glycoside linkage types: fucogalactoglucan, glucofucogalactan, fucoglucan, and glucan. The main chain of heteroglucans often consists of ß-(1 → 6)-Glcp, ß-(1 → 4)-Glcp, and ß-(1 → 3)-Glcp residues, which are predominantly substituted at the O-3 and O-6 positions. The main chain structure of heterogalactans is α-(1 → 6)-Galp residues, which may be replaced by Fucp and Galp residues at O-2. Overall, our findings demonstrate the validity of the "relative ordered structure of polysaccharide" in Hericium erectus polysaccharides and simplify the complexity of polysaccharide structures.

Comparison of structures and emulsifying properties between water-extracted pectins from Fructus aurantii.

The structural characteristics of two water-extracted pectic polysaccharides from Fructus aurantii were investigated, and the impacts of their structures on the emulsifying stability were evaluated. FWP-60 (extracted by cold water and followed 60 % ethanol precipitation) and FHWP-50 (extracted by hot water and followed 50 % ethanol precipitation) were both high methyl-esterified pectins, which were composed of homogalacturonan (HG) and highly branched rhamnogalacturonan I (RG-I) regions. The weight-average molecular weight, methyl-esterification degree (DM) and HG/RG-I ratio of FWP-60 were 1200 kDa, 66.39 % and 4.45, respectively, which were 781 kDa, 79.10 % and 1.95 for FHWP-50. The methylation and NMR analysis of FWP-60 and FHWP-50 demonstrated that the main backbone consisted of different molar ratios of →4)-α-GalpA-(1 â†’ and →4)-α-GalpA-6-O-methyl-(1 →, and the side chains contained arabinan and galactan. Moreover, the emulsifying properties of FWP-60 and FHWP-50 were discussed. Compared with FHWP-50, FWP-60 had better emulsion stability. Overall, pectin had a linear HG domain and a small number of RG-I domain with short side chains to facilitate the stabilization of emulsions in Fructus aurantii. A comprehensive knowledge of the structure characteristic and emulsifying property would enable us to provide more information and theoretical guidance for the structure and emulsion preparation of Fructus aurantii pectic polysaccharides.

A branched galactoglucan with flexible chains from the basidioma of Macrolepiota albuminosa (Berk.) Pegler.

A homogeneous galactoglucan was purified from the alkali-extracted polysaccharides from the basidioma of Macrolepiota albuminosa by gradient ethanol precipitation, whose proposed structure was given for the first time. Results showed it had a molecular weight of 210 kDa, and mainly consisted of glucose and galactose. There were abundant filaments, randomly distributed sheet-like and flaky appearance in its surface by SEM observation. Its backbone comprised ß-(1 â†’ 6)-Glcp, α-(1 â†’ 6)-Galp and ß-(1 â†’ 3,6)-Glcp residues at 4:1:1, terminated by ß-(1 â†’ 3)-Glcp and T-Glcp residues. Rheological measurements suggested its steady flow behavior was highly dependent on concentrations. Newtonian behavior was evident at low concentrations, whereas pseudoplastic behavior was observed at high concentrations. Besides, the X-ray diffraction patterns proved the presence of amorphous structure. The conformational parameters were detected by HPSEC-MALLS-RI, revealing a random coil conformation in NaNO3 aqueous solution. This work provides a theoretical basis for the application of polysaccharides from M. albuminosa in food- and drug-based therapies.

Gastroprotective activity of polysaccharide from the fruiting body of Hericium erinaceus against acetic acid-induced gastric ulcer in rats and structure of one bioactive fraction.

This study aimed at investigating gastroprotective activity of Hericium erinaceus polysaccharide (HEP) and characterizing one of its bioactive fractions. Acetic acid-induced gastric ulcer (GU) rat model was used to evaluate the gastroprotective activity of HEP, while H2O2-induced injury GES-1 cell model was conducted to screen the bioactive fractions from HEP. Moreover, one of the bioactive fractions was characterized using methylation and 1D/2D NMR analysis. Results indicated HEP treatment could ameliorate acetic acid-induced GU in rats. HEP supplement decreased levels of interleukin-6, tumor necrosis factor-α and malondialdehyde and myeloperoxidase activity, and increased releases of nitric oxide, prostaglandin E2, epidermal growth factor, vascular endothelial growth factor and basic fibroblast growth factor and superoxide dismutase activity in gastric tissues of ulcerated rats. Five purified polysaccharides from HEP were screened to be bioactive fractions with cytoprotection on H2O2-induced injury in GES-1 cells. Among them, RP-S was characterized to be a (1 â†’ 6)-ß-D-glucan, whose backbone was composed of →6)-ß-D-Glcp-(1 â†’ residue and branched with T-ß-D-Glcp-(1 â†’ residue at O-3 position. In conclusion, HEP possessed gastroprotection against acetic acid-induced GU in rats and one of its bioactive fractions was a ß-D-glucan. This study supports the utilization of HEP in anti-GU and provides evidences for the structure of gastroprotective HEP.

Structural characteristic of pectin-glucuronoxylan complex from Dolichos lablab L. hull.

Polysaccharides are important constituents in Dolichos lablab hull. Herein, pectin-glucuronoxylan complex from D. lablab hull designated as DLHP-3 (D. lablab hull polysaccharide,) was prepared by ion exchange and gel permeation chromatography, and further characterized by acid degradation and enzymatic hydrolysis, methylation combined with GC-MS, NMR and MALDI-TOF-MS analysis. Both of pectin and glucuronoxylan regions were found in DLHP-3. The glucuronoxylan region consisted of a →4)-ß-Xylp-(1→ backbone with branches of α-GlcpA-(1→ substituted at O-2 site, and the ratio of xylose to glucuronic acid was about 5:1. Acetyl groups were mainly attached to O-3 site of →2,4)-ß-Xylp-(1→ residues. The main chain of pectin region could be represented by →4)-α-GalpA-(1→4)-α-GalpA-(1→ and →2)-α-Rhap-(1→4)-α-GalpA-(1→ with partial methyl-esterification. The side chains were deduced to embrace arabinan and arabinogalactan linked to rhamnogalacturonan-I region. Pectin was probably covalently bound to glucuronoxylan. Our findings uncovered the molecular structure of pectin-glucuronoxylan complex from D. lablab hull.

Revealing the architecture and solution properties of polysaccharide fractions from Macrolepiota albuminosa (Berk.) Pegler.

Macrolepiota albuminosa (Berk.) Pegler is abundant in active polysaccharides, but little is known about their structures and solution properties. In this study, water-extracted polysaccharides from M. albuminosa (MAWP) were purified into three fractions with structural heterogeneity, which was attributed to the diversity in molecular weight, monosaccharide composition and linkage patterns, further affecting their solution properties. Methylation and NMR analysis revealed MAWP-60p and MAWP-70 were a 3-O-methylated glucomannogalactan and a previously unreported glucomannogalactan, whereas MAWP-80 was elucidated as a branched galactoglucan. Besides, three fractions exhibited random coil conformation in aqueous solution, while MAWP-60p had the highest viscosity due to its highest molecular weight, mean square radius of gyration (Rg) and O-methyl group attached to the backbone. The molecular weight, monosaccharide composition and glycosidic linkages might be the major contributors to the flexibility, molecular size and stereochemistry of mushroom polysaccharide chains.

Structural characteristics of three pectins isolated from white kidney bean.

Three water-soluble pectic polysaccharides (WKBP-P2, P3 and P4) were isolated from white kidney bean by ion exchange combined with size-exclusion methods. The structural features were characterized by GC-MS, NMR spectroscopy and HPSEC-MALLS-RI. It was found that three pectic polysaccharides were the major water-extracted polysaccharides in white kidney bean. All the WKBP-P2, P3 and P4 were probably composed of various structural regions including homogalacturonan (HG), xylogalacturonan (XGA), rhamnogalacturonan I (RG-I) regions in backbone, and arabinan region mainly as side chain. However, these pectic polysaccharides were significantly different in molar ratios of these structural regions and molecular size. WKBP-P2 was HG-predominant pectin (partially methyl-esterified) with weight-average molecular weight (Mw) of 1.2 × 104 g/mol, and contained minor RG-I, arabinan and probable XGA regions. WKBP-P3 (Mw of 4.0 × 104 g/mol) primarily embraced XGA, HG, arabinan regions and minor RG-I region. WKBP-4 with highest Mw (4.5 × 105 g/mol) had the most arabinan region (51.3%), which was probably the side chain linked to the backbone composed of RG-I, HG and slight XGA regions. These findings provided a structural basis for study on polysaccharides from white kidney bean, which was benefit for development of functional food.