Alkali-extractable Polysaccharides Research Articles

Characterization and in vitro digestion of alkali-extracted polysaccharides from Grifola frondosa and its impacts on human gut microbiota

Grifola frondosa is a highly valued, edible and biologically active fungus in which the polysaccharide component plays a major role. To investigate the fundamental structure, in vitro digestion and fermentation characteristics of Grifola frondosa polysaccharides (GFP), GFP from the waste residue of Grifola frondosa after water extraction was re-extracted by alkaline solution. The carbohydrate and β-glucan contents of GFP were 91.61% and 60.57%, respectively, and were mainly composed of glucose. GFP can form triple supercoils and combine with Congo red, and the surface of GFP was smooth and dense, and the particles were in the shape of long column, sheet and ellipse. Analysis of carbohydrate, reducing sugars, and further chromatogram data also showed that GFP was not degraded by the simulated digestion process of the mouth, stomach and small intestine. Fecal fermentation of GFP significantly increased the abundance of Bacteroidota, and decreased Proteobacterias in both normal weight and obese subjects in vitro. The short-chain fatty acid (SCFA)-producing bacteria, Faecalibacterium, Erysipelotrichaceae_UCG_003, Lactococcus were increased, and Dorea and Escherichia-Shigella were reduced after GFP treatment. Thus, the molecular of GFP was utilized and degraded by the gut microbiota and metabolized into SCFAs. This decreased pH, H2S, and NH3, as well as increased CO2 in the fermentation broth. In conclusion, GFP can modulate the composition of the gut microbiota and is a potentially functional product.

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 β-1,3-d-Glcp and β-1,6-d-Glcp residues as main chains, respectively. However, other subfractions were considered as β-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.

An alkali-extracted polysaccharide from Pleurotus eous and exploration of its antioxidant and immunomodulatory activities

An alkali-extracted polysaccharide from Pleurotus eous and exploration of its antioxidant and immunomodulatory activities

Biochemical characterisation of cellulose and cell-wall-matrix polysaccharides in variously oxidised sugar-beet pulp preparations differing in viscosity

Sugar-beet pulp (SBP) is an abundant, cellulose-rich, non-food by-product of agriculture. Oxidised SBP (oP) has valuable viscosity attributes, and different oxidation protocols yield higher- or lower-viscosity oP. We investigated how SBP polysaccharides change during oxidation, since these changes must define oP quality. Oxidation solubilised much pectin and hemicellulose; however, most cellulose stayed insoluble. Fresh SBP contains negligible ‘hemicellulose a’ (=alkali-extractable polysaccharides that precipitate upon acidification), but oxidation created abundant glucose-rich ‘hemicellulose a’ from SBP cellulose. We propose that the cellulose acquired COOH groups, conferring alkali-extractability and admitting more water, thereby augmenting viscosity. The pectin and hemicellulose molecules that were retained during oxidation had been partially depolymerised, and their median Mr correlated negatively with oP viscosity. We developed a novel procedure to explore cellulose's permeability by measuring the ingress of tritium from [3H]water into microfibrils and its retention during desiccation. In high-crystallinity Avicel, 75 % of the cellulose's OH groups were inaccessible to [3H]water, whereas filter-paper cellulose acquired the theoretical maximum 3H, indicating an open structure. Retention of 3H by oP preparations correlated positively with viscosity, indicating that increased cellulose accessibility generates a viscous oP. In conclusion, depolymerisation and solubilisation of matrix polysaccharides, accompanied by increasing water-accessibility of cellulose, enhanced SBP's viscosity.

Structural characterization of alkali-extracted jujube polysaccharides and their effects on the fecal microbiota in vitro

The structural characteristics of alkali-extracted jujube polysaccharides and their effects of in vitro fermentation on fecal microorganisms were evaluated in this study. Scanning electron microscopy revealed that AJP1 and AJP2 polysaccharides had different morphological characteristics, and their molecular weights were 75465 Da and 268007 Da, respectively. The uronic acid contents of the two polysaccharides were 79.68% and 77.64%. Infrared spectroscopy showed that two alkaline-extracted polysaccharide groups had characteristic absorption peaks of acidic polysaccharides such as C=O and C-H. After 48 h of in vitro fermentation, the total sugar consumption rates of the AJP1 and AJP2 treatments reached 65.40% and 56.24%, respectively. During the fermentation process, the pH values of the polysaccharide-treated groups were significantly lower compared to the control group. In addition, polysaccharides could promote the abundance, diversity, and composition of gut microbiota. These results showed that alkali-extracted jujube polysaccharides could regulate the intestinal microflora composition in feces, and inhibit the growth of pathogenic bacteria Peptoniphilus and Desulfovibrio while promoting the growth of beneficial bacteria such as Megamonas and Allisonella. This study provides a reference for further developing jujube polysaccharide functional food products and the study of the structure-activity relationship between alkali-extracted polysaccharides and intestinal flora.

CM3-SII polysaccharide obtained from Cordyceps militaris ameliorates hyperlipidemia in heterozygous LDLR-deficient hamsters by modulating gut microbiota and NPC1L1 and PPARα levels

Accumulating evidence has demonstrated that polysaccharides derived from edible fungi have lipid-lowering effects in mice. However, the lipid metabolism mechanisms in mice and humans are different. We have previously elucidated the structural characteristics of the alkali-extracted polysaccharide CM3-SII obtained from Cordyceps militaris. This study aimed to investigate whether CM3-SII could ameliorate hyperlipidemia in a heterozygous low-density lipoprotein receptor (LDLR)-deficient hamster model of hyperlipidemia. Our data demonstrated that CM3-SII significantly decreased total plasma cholesterol, non-high-density lipoprotein cholesterol, and triglyceride levels in heterozygous LDLR-deficient hamsters. Unlike ezetimibe, CM3-SII could enhance the concentration of plasma apolipoprotein A1 and the expression of liver X receptor α/ATP-binding cassette transporter G8 mRNA pathway and suppress the expression of Niemann-Pick C1-like 1, which help to reduce cholesterol levels further. Moreover, the results of molecular docking analysis demonstrated that CM3-SII could directly bind to Niemann-Pick C1-like 1 with high affinity. The triglyceride-lowering mechanisms of CM3-SII were related to its downregulation of sterol regulatory element-binding protein 1c and upregulation of peroxisome proliferator-activated receptor α. Importantly, CM3-SII increased the abundance of Actinobacteria and Faecalibaculum and the ratio of Bacteroidetes/Firmicutes. Thus, CM3-SII attenuated hyperlipidemia by modulating the expression of multiple molecules involved in lipid metabolism and the gut microbiota.

An Alkali-extracted polysaccharide from Poria cocos activates RAW264.7 macrophages via NF-κB signaling pathway

An alkali-extracted polysaccharide (PCAPS1) was isolated and purified from the Poria cocos. Our results proved that PCAPS1 was a neutral polysaccharide with a molecular weight of 11.5 kDa. The monosaccharide composition, methylation and NMR analysis results displayed that the polysaccharide was mostly comprised of β-1,3-glucan with 1,4 and 1,6 branches. The Immune activity and mechanism of PCAPS1 were evaluated in RAW264.7 cells. The enzyme-linked immunosorbent assay (ELISA) analysis revealed that PCAPS1 increased the tumor necrosis factor-α (TNF-α) secretion. RNA-sequencing data analysis suggested that PCAPS1 activated macrophages by the classic NF-κB pathway. Real-time quantitative polymerase chain reaction (RT-qPCR) analysis confirmed that PCAPS1 enhanced mRNA expression levels of TNF-α and nuclear factor κB (NF-κB) in RAW264.7 cells. Simultaneously, the fluorescence nuclear transport experiment showed that PCAPS1 activated RAW264.7 cells by inducing the NF-κB p65 translocation. Our results indicated that PCAPS1-induced TNF-α expression was mediated via the NF-κB signaling pathway.

Life cycle assessment and techno-economic analysis of joint extraction of Eucommia powder, gum, water-soluble polysaccharide and alkali-extractable polysaccharide from Eucommia leaves

The economic feasibility and environmental burdens of a process extracting Eucommia powder, Eucommia gum, water-soluble polysaccharide, and alkali-extractable polysaccharide from Eucommia leaves are evaluated by modeling a 900 kg of Eucommia leaves per day facility. Total capital investment (TCI) and total product cost were separately estimated to be $2.64 million and $7.12 million while an internal facility rate of return (IRR) of 30.0% was calculated. The GWP100a emission for Eucommia powder is 111 kg of CO2eq per kg of Eucommia powder, the CED for Eucommia powder is 2200 MJ per kg of Eucommia powder, and the EI99 for Eucommia powder is 9.15 points per kg of Eucommia powder when using mass-based allocation. The life-cycle impact assessment (LCIA) results using economic value-based allocation is around 4 times higher than the corresponding LCIA results using mass-based allocation. Therefore, the joint extraction process could be economically attractive but could not be environmentally-friendly.

Optimization of Activated Carbon Decolorization Process of Water- and Alkali-Extracted Polysaccharides from Cordyceps taii

Optimization of Activated Carbon Decolorization Process of Water- and Alkali-Extracted Polysaccharides from Cordyceps taii

Physicochemical characterization, rheological and antioxidant properties of three alkali-extracted polysaccharides from mung bean skin

The properties of polysaccharides are closely related to their extraction and preparation methods. However, studies on the effect of alkali concentration on the properties of polysaccharides during alkali extraction are scarce. In this study, three alkali-extracted polysaccharides from mung bean skin (MBP) by different alkali concentrations (0.5%, 1.0%, 2.0%, w/v, MBP0.5, MBP1.0 and MBP2.0) were successfully obtained. The effects of alkali concentration on the extraction rate, microstructure, rheological properties, antioxidant activity and cell proliferation activity of MBP were investigated. The results showed that the alkali extraction method can break the ester and hydrogen bonds between polysaccharides, thus three alkali-extracted polysaccharides had higher extraction yields than polysaccharide extracted by hot water (MBPW), and MBP1.0 extraction rate of 3.64%. Moreover, comparing with MBPW, three alkali-extracted polysaccharides had lower molecular weights, particle sizes and better thermal stability. In addition, MBP0.5 had better antioxidant activity due to its higher galacturonic acid content and lower molecular weight, MBP1.0 and MBP2.0 had a tight structure, flat surface, resulting in a strong gel network structure. Cell experiments showed that MBPs had different degrees of proliferative effects on RAW264.7 and L-02. This study will provide some research ideas for the extraction of plant polysaccharides by alkaline methods.

Comparison of water- and alkali-extracted polysaccharides from Fuzhuan brick tea and their immunomodulatory effects in vitro and in vivo.

In the present study, the purpose is to compare the effect of water extraction and alkali-assisted extraction on the structural characteristics and immunomodulatory activity of polysaccharides from Fuzhuan brick tea (FBTPs). The results indicated that water-extracted FBTPs (W-FBTPs) and alkali-extracted FBTPs (A-FBTPs) had similar molecular weights but different monosaccharide compositions, of which A-FBTPs had a higher yield and uronic acid groups corresponding to galacturonic acid (GalA). Moreover, A-FBTPs had stronger ability to promote phagocytic capacity, acid phosphatase activity and nitric oxide (NO) secretion in macrophages in vitro. In the in vivo study, A-FBTPs exhibited a promising effect to adjust the immune imbalance by enhancing the body features, antioxidant activities, immune response and intestinal mucosal barrier in cytoxan (CTX)-induced immunosuppressive mice. Besides, A-FBTP supplementation effectively improved CTX-induced gut microbiota dysbiosis, including promoting the abundance of beneficial bacteria (e.g., Lactobacillus) and short chain fatty acid (SCFA)-producing bacteria (e.g., Lachnospiraceae, Prevotellaceae and Ruminococcaceae), along with reducing the growth of potentially pathogenic microbes (e.g., Desulfovibrionaceae and Helicobacter). These findings suggested that alkaline extraction might be a promising way to obtain high-quality acidic polysaccharides from Fuzhuan brick tea (FBT), and A-FBTPs could be developed as novel potential prebiotics and immunomodulators for further application in food formulations.

Chemical elucidation of an arabinogalactan from rhizome of Polygonatum sibiricum with antioxidant activities

Polygonatum sibiricum is traditionally used as Chinese medicine for immunity enhancement. Exploration of polysaccharides from Polygonatum species would provide a wider insight into the studies on their chemical structures and function activities. In this study, the alkali-extracted polysaccharide from P. sibiricum (PSP) was isolated and examined. The polysaccharide was firstly isolated by ion-exchange chromatography equipped with DE52 column, followed by isolated through Superdex-200 column. The obtained PSPJWA fraction was a homogenous one with average molecular weight of 141 kDa. The monosaccharide composition was galactose, arabinose and rhamnose in a ratio of 14:4:1. The glycosidic linkages of PSPJWA fraction were indicated to be Araf-(1→, →5)-Araf-(1→, →3,5)-Araf-(1→, Galp-(1→, →4)-Galp-(1→, →4,6)-Galp-(1→ and →2,4)-Rhap-(1→ residue by methylation analysis. NMR and enzymatic studies showed that PSPJWA was a novel arabinogalactan-type structure. PSPJW polysaccharides with different molecular weight and similar chemical structure had different antioxidant activities. Together, P. sibiricum polysaccharide has the potential to be a natural antioxidant.

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 β-(1 → 6)-Glcp, α-(1 → 6)-Galp and β-(1 → 3,6)-Glcp residues at 4:1:1, terminated by β-(1 → 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.

Structural characterization of an alkali-extracted polysaccharide from Dioscorea opposita Thunb. with initial studies on its anti-inflammatory activity

An alkali-extracted polysaccharide (HY-B) was isolated and purified from Dioscorea opposita Thunb. (Huai Yam). Its chemical structure was analyzed with FT-IR, GC-MS and 1 D, 2 D-NMR spectrometry. It was proved that HY-B is mainly composed of α-1,4-linked glucose, which is similar to starch, but the starch-iodine color test proved that it was not starch. The chain conformation of HY-B was analyzed by SEC-MALLS-RI and TEM, indicated that HY-B exists in a random coil conformation. Its molecular weight is 18.7 kDa, and the molecular size is about 100 nm. MTT assays indicated that HY-B was nontoxic to RAW 264.7 cells in vitro. The results of anti-inflammatory studies showed that HY-B could inhibit the production of NO and TNF-α in RAW 264.7 macrophage stimulated by lipopolysaccharides (LPSs). This work provided the important information about the anti-inflammatory active component of Huai Yam and its potential applications in the food and health industries.

Purification, structural characterization, and PCSK9 secretion inhibitory effect of the novel alkali-extracted polysaccharide from Cordyceps militaris

One novel alkali-extracted polysaccharide, CM3-SII, was obtained from the fruiting body of C. militaris via column chromatography. Its structural characteristics were investigated via chemical and spectroscopic methods. The backbone of CM3-SII was composed of →4)-β-D-Manp(1→, →6)-β-D-Manp(1→, and →6)-α-D-Manp(1→ glycosyls, and branching at the O-4 positions of →6)-β-D-Manp(1→ glycosyls with β-D-Galp, (1→2) linked-β-D-Galf, and →2,6)-α-D-Manp(1→ residues. Furthermore, O-6 and O-2 positions of the →2,6)-α-D-Manp(1→ residues were substituted with methyl and β-D-Galp, respectively. This polysaccharide significantly enhanced the intracellular protein expression of low-density lipoprotein receptor and proprotein convertase subtilisin/kexin type 9 (PCSK9) via regulating sterol regulatory element-binding protein 2 in hepatoma Huh7 cells. Of note, CM3-SII significantly decreased PCSK9 secretion at the concentration of 200 μg/mL. Collectively, CM3-SII is different from the previously reported alkali-extracted polysaccharides isolated from the fruiting body of C. militaris, and it may have potential application in hypolipidemia or as a pharmaceutical additive.

Comprehensive evaluation of alkali-extracted polysaccharides from Agrocybe cylindracea: Comparison on structural characterization

Agrocybe cylindracea is a common source of active polysaccharides, but their fine structures are not clearly elucidated. In the present study, four fractions were purified from the alkaline extract of A. cylindracea (JACP), and their chemical components and structures were compared by HPAEC-PAD, methylation combined with GC–MS, and 1D/2D NMR analysis. Results showed the purified fractions’ physicochemical properties, including monosaccharide compositions, molecular weights, viscosities and surface morphology considerably varied. JACP-30 was identified as a fucoglucogalactan with a α-(1 → 6)-galactopyranosyl as main chain. JACP-50p and JACP-80r were characterized as β-(1 → 6)-glucans with side chains composed of terminal and 3-substituted β-glucopyranosyl residues attached at O-3 for every three residues. Similarly, the backbone of JACP-80 was β-(1 → 6)-linked glucopyranosyl and β-(1 → 3,6)-linked glucopyranosyl residues at a ratio of 4:1. This work provides more information to the understanding of polysaccharides from A. cylindracea, further guiding its biological researches and developing the application in food and biomedicine industries.

Structural characterization and antioxidant activity of alkali-extracted polysaccharides from quinoa

A polysaccharide component (SQAP-2) was isolated from quinoa by alkaline extraction and purified with DEAE-Sepharose Fast Flow and Sephacryl S-300 column chromatography. The chemical structure of the polysaccharide was characterized, and the impact on antioxidant activity was evaluated. Polysaccharide SQAP-2 (2.02 × 103 Da) is a type of glucose whose glycosidic bond Glc-(1→, →4)-Glcp-(1→, →4, 6)-Glcp-(1→ linkages were identified through gas chromatography-mass spectrometry. Nuclear magnetic resonance confirmed the monosaccharide composition and glycosidic linkage content, and a suggestion of the structural formula was provided. Their radical scavenging capacity was evaluated, and scavenging activity against DPPH, ABTS, hydroxyl, superoxide radicals, and ferric reducing ability exhibited excellent radical scavenging activities of approximately 21.71 ± 1.25%, 49.46 ± 1.59%, 70.10 ± 3.39%, 70.49 ± 2.09%, 51.25 ± 1.16%, respectively, at 3 mg/mL. The isolated quinoa polysaccharides could represent an antioxidant agent once the structural features and antioxidant activities are definitively characterized.

Extraction Methods Affect the Structure of Goji (Lycium barbarum) Polysaccharides

Polysaccharides are considered to be the most important active substances in Goji. However, the structure of polysaccharides varies according to the extraction methods applied, and the solution used to prepare Goji polysaccharides (LBPs) were limited. Thus, it is important to clarify the connection between extraction methods and structure of Goji polysaccharide. In view of the complex composition of cell wall polysaccharides and the various forms of interaction, different extraction methods will release different parts of the cell wall. The present study compared the effects of different extraction methods, which have been used to prepare different types of plant cell wall polysaccharides based on various sources, on the structure of cell-wall polysaccharides from Goji, by the single separate use of hot water, hydrochloric acid (0.4%) and sodium hydroxide (0.6%), at both high and low temperatures. Meanwhile, in order to explore the limitations of single extraction, sequential extraction methods were applied. Structural analysis including monosaccharide analysis, GPC-MALLS, AFM and 1H-NMR suggested the persistence of more extensively branched rhamnogalacturonan I (RG-I) domains in the procedures involving low-temperature-alkali, while procedures prepared by high-temperature-acid contains more homogalacturonan (HG) regions and results in the removal of a substantial part of the side chain, specifically the arabinan. A kind of acidic heteropolysaccharide was obtained by hot water extraction. SEC-MALLS and AFM confirmed large-size polymers with branched morphologies in alkali-extracted polysaccharides. Our results provide new insight into the extraction of Goji polysaccharides, which differ from the hot water extraction used by traditional Chinese medicine.

Physicochemical, structural and rheological properties of alkali-extracted polysaccharide from fruiting body of Hericium erinaceus

An alkali-extracted polysaccharide (HEAEP-0.5) was prepared from the water insoluble residue of Hericium erinaceus fruiting body. Effects of concentration, temperature, pH and salts on its rheological property were systematically evaluated. Its physicochemical property, structural characteristic and intrinsic viscosity were also determined. Results revealed that HEAEP-0.5 was a β-D-glucan polymer, which contained a →3)-Glcp-(1→ backbone branched with Glc units at O-6 position. HEAEP-0.5 was a high molecular weight (5400 kDa and 290 kDa) polysaccharide showing high viscosity with an intrinsic viscosity value as 1.43 L/g, and revealing a triple helix conformation. It exhibited strong shear-thinning behavior and could form weak gels as concentration increased. Increase in concentration and addition of NaCl or CaCl2 elevated the apparent viscosity and gel strength of HEAEP-0.5 solution, while reverse was the case as temperature increased. The gel formed by this polysaccharide at the concentration of 2.0 g/dL was a thermally irreversible gel and was not highly sensitive to temperature changes (5–45 °C). Its apparent viscosity and gel strength were higher under neutral addition (pH 7.0) than those under alkaline (pH 8.0 & pH 9.0) and acidic additions (pH 5.0 & pH 6.0). This study indicates HEAEP-0.5 is a novel hydrocolloid in food and other industries.

An alkali-extracted polysaccharide from Zizyphus jujuba cv. Muzao: Structural characterizations and antioxidant activities

An acidic polysaccharide (SAZMP3) was isolated from jujube fruit residues by alkaline extraction and purified with DEAE-Sepharose Fast Flow and Sephacryl S-300 column chromatography. The structural characterizations of SAZMP3 were determined by high-performance gelpermeation chromatography, gas chromatography, Fourier transform infrared spectroscopy, methylation analysis, NMR spectroscopy, scanning electron microscopy, and atomic force microscopy. The results determined SAZMP3 was an acidic polysaccharide mainly contained rhamnose, galactose, and galacturonic acid with a molecular weight of 9.37 kDa and its backbone might mainly be composed of 1,4-α-D-GalAp with side chains of 1,3-β-D-Galp, 1,3,5-linked Araf, 1,2,4-α-L-Rhap and terminals of 1-linked Araf, 1-linked Rhap, 1-linked Galp by methylation and NMR analysis. Besides, SAZMP3 has shown potential antioxidant activity in scavenging free radicals suggesting that it is an antioxidant agent, which might contribute to the functional food qualities of jujube fruit.