Structural characterization of an intestinal immune system-modulating arabino-3,6-galactan-like polysaccharide from the above-ground part of Astragalus membranaceus (Bunge)

New flavonoid glycosides from the stems and leaves of Astragalus membranaceus

Astragalus membranaceus, a well-known traditional medicine and food, has been extensively studied for its roots. However, comparatively little attention has been paid to its stems and leaves. In this study, we successfully isolated and identified three new flavonoid glycosides (1-3), and eight known analogues (4-11) from the stems and leaves of A. membranaceus. Notably, compound 10 exhibited significant anti-inflammatory activities in LPS-induced BV2 cells, with IC50 value of 1.11 ± 0.04 μM. These findings highlight flavonoids as the key bioactive components present in the stems and leaves of A. membranaceus.

Preparation, structural characterization, biological activity, and nutritional applications of oligosaccharides

Oligosaccharides are low-molecular-weight carbohydrates between monosaccharides and polysaccharides. They can be extracted directly from natural products by physicochemical methods or obtained by chemical synthesis or enzymatic reaction. Oligosaccharides have important physicochemical and physiological properties. Their research and production involve many disciplines such as medicine, chemical industry, and biology. Functional oligosaccharides, as an excellent functional food base, can be used as dietary fibrer and prebiotics to enrich the diet; improve the microecology of the gut; exert antitumour, anti-inflammatory, antioxidant, and lipid-lowering properties. Therefore, the industrial applications of oligosaccharides have increased rapidly in the past few years. It has great prospects in the field of food and medicinal chemistry. This review summarized the preparation, structural features and biological activities of oligosaccharides, with particular emphasis on the application of functional oligosaccharides in the food industry and human nutritional health. It aims to inform further research and development of oligosaccharides and food chemistry.

Structural elucidation and immunomodulatory activities in vitro of type I and II arabinogalactans from different origins of Astragalus membranaceus

Astragalus membranaceus polysaccharide (APS) possesses excellent immunomodulatory activity. However, there are several studies on the structural characterization of APS. Here, we aimed to elucidate the repeating units of polysaccharides (APS1, 106.5 kDa; APS2, 114.5 kDa) obtained from different Astragalus membranaceus origins and further investigated their immunomodulatory activities. Based on structural analysis, types of the two polysaccharides were identified as arabinogalactan-I (AG-I) and arabinogalactan-II (AG-II), and co-elution of arabinogalactans (AGs) and α-glucan was observed. The backbone of AG-I was 1,4-linked β-Galp occasionally substituted by α-Araf at O-2 and/or O-3. AG-II was a highly branched polysaccharide with long branches of α-Araf, which were attached to the O-3 of 1,6-linked β-Galp of the backbone. The presence of AGs in A. membranaceus was confirmed for the first time. The two polysaccharides could promote the expression of IL-6, IL-1β and TNF-α in RAW264.7 cells via MAPKs and NF-κB signaling pathways. The constants for APS1 and APS2 binding to Toll-like receptor 4 (TLR4) were 1.83 × 10-5 and 2.08 × 10-6, respectively. Notably, APS2 showed better immunomodulatory activity than APS1, possibly because APS2 contained more AGs. Hence, the results suggested that AGs were the vital components of APS in the immunomodulatory effect.

Structure-activity relationship of low molecular weight Astragalus membranaceus polysaccharides produced by Bacteroides

Astragalus membranaceus polysaccharides (APS) possess significant biological activities, such as anti-tumor, antiviral, and immunomodulatory activities. However, there is still a lack of research on the structure-activity relationship of APS. In this paper, two carbohydrate-active enzymes from Bacteroides in living organisms were used to prepare degradation products. The degradation products were divided into APS-A1, APS-G1, APS-G2, and APS-G3 according to molecular weight. Structural analysis showed that all degradation products had an α-1,4-linked glucose backbone, but APS-A1 and APS-G3 also had branched chains of α-1,6-linked galactose or arabinogalacto-oligosaccharide. In vitro, immunomodulatory activity evaluation results indicated that APS-A1 and APS-G3 had better immunomodulatory activity, while the immunomodulatory activities of APS-G1 and APS-G2 were comparatively weaker. Molecular interaction detection showed that APS-A1 and APS-G3 could bind to toll-like receptors-4 (TLR-4) with a binding constant of 4.6 × 10^-5 and 9.4 × 10^-6, respectively, while APS-G1 and APS-G2 failed to bind to TLR-4. Therefore, the branched chains of galactose or arabinogalacto-oligosaccharide played a crucial role in the immunomodulatory activity of APS.

Biosynthesis and Pharmacological Activities of Flavonoids, Triterpene Saponins and Polysaccharides Derived from Astragalus membranaceus

Astragalus membranaceus (A. membranaceus), a well-known traditional herbal medicine, has been widely used in ailments for more than 2000 years. The main bioactive compounds including flavonoids, triterpene saponins and polysaccharides obtained from A. membranaceus have shown a wide range of biological activities and pharmacological effects. These bioactive compounds have a significant role in protecting the liver, immunomodulation, anticancer, antidiabetic, antiviral, antiinflammatory, antioxidant and anti-cardiovascular activities. The flavonoids are initially synthesized through the phenylpropanoid pathway, followed by catalysis with corresponding enzymes, while the triterpenoid saponins, especially astragalosides, are synthesized through the universal upstream pathways of mevalonate (MVA) and methylerythritol phosphate (MEP), and the downstream pathway of triterpenoid skeleton formation and modification. Moreover, the Astragalus polysaccharide (APS) possesses multiple pharmacological activities. In this review, we comprehensively discussed the biosynthesis pathway of flavonoids and triterpenoid saponins, and the structural features of polysaccharides in A. membranaceus. We further systematically summarized the pharmacological effects of bioactive ingredients in A. membranaceus, which laid the foundation for the development of clinical candidate agents. Finally, we proposed potential strategies of heterologous biosynthesis to improve the industrialized production and sustainable supply of natural products with pharmacological activities from A. membranaceus, thereby providing an important guide for their future development trend.

Hypoglycemic activity in vitro and vivo of a water-soluble polysaccharide from Astragalus membranaceus

The polysaccharide AMP as one main bioactive component of Astragalus membranaceus (Fisch.) Bunge was separated and characterized. The results showed that AMP was a typical acidic heteropolysaccharide dominated by glucose, galacturonic acid and arabinose with typical shear-thinning and fluid-like behavior. Scanning electron microscopy images showed that AMP existed in the state of lamellar aggregates with a smooth compact surface. In addition, AMP exhibited strong antioxidant activity with an oxygen radical absorption capacity value of 278.68 ± 9.31 μM TE per g, and excellent α-glucosidase inhibitory activity and cholate binding ability. Furthermore, in vivo, AMP treatment significantly decreased blood glucose and serum insulin levels, improved glucose intolerance and insulin resistance, regulated the blood lipid profile, alleviated oxidative stress, and relieved liver damage in type 2 diabetes mellitus (T2DM) mice. Pearson correlation analysis suggested that the mitigation of oxidative stress contributed to the hypoglycemic effect of AMP, indicating that it is a beneficial functional food ingredient for T2DM.

Astragalus polysaccharide: a review of its immunomodulatory effect

The Astragalus polysaccharide is an important bioactive component derived from the dry root of Astragalus membranaceus. This review aims to provide a comprehensive overview of the research progress on the immunomodulatory effect of Astragalus polysaccharide and provide valuable reference information. We review the immunomodulatory effect of Astragalus polysaccharide on central and peripheral immune organs, including bone marrow, thymus, lymph nodes, spleen, and mucosal tissues. Furthermore, the immunomodulatory effect of Astragalus polysaccharide on a variety of immune cells is summarized. Studies have shown that Astragalus polysaccharide can promote the activities of macrophages, natural killer cells, dendritic cells, T lymphocytes, B lymphocytes and microglia and induce the expression of a variety of cytokines and chemokines. The immunomodulatory effect of Astragalus polysaccharide makes it promising for the treatment of many diseases, including cancer, infection, type 1 diabetes, asthma, and autoimmune disease. Among them, the anticancer effect is the most prominent. In short, Astragalus polysaccharide is a valuable immunomodulatory medicine, but further high-quality studies are warranted to corroborate its clinical efficacy.

Hypoglycemic effect of polysaccharide from Astragalus membranaceus on type 2 diabetic mice based on “gut microbiota-mucosal barrier”

Astragalus membranaceus polysaccharide (APP), the main active constituent possesses numerous bioactivities. In this research, the T2DM model mice was combined with streptozotocin to study the hypoglycemic effect and mechanism of...

Structural elucidation and anti-diabetic osteoporotic activity of an arabinogalactan from Phellodendron chinense Schneid

Phellodendron chinense Schneid. was widely used as a medicinal herb for the treatment of diabetic osteoporosis in China. In this study, an arabinogalactan, named as PPCP-1, was isolated from the bark of Phellodendron chinense Schneid., and purified by DEAE-cellulose DE52 and Sephacryl S-200 HR column chromatography. The structure of PPCP-1 was characterized as a repeating unit consisting of →3)-β-d-Galp-(1→, →3,6)-β-d-Galp-(1→, →5)-α-l-Araf-(1→, →4)-α-d-Glcp-(1→, →3)-α-d-Glcp-(1→, →4)-α-d-Manp-(1→ with branches of →5)-α-l-Araf-(1→, →3,5)-α-l-Araf-(1→ and terminal α-l-Araf. Pharmacologically, the oral administration of PPCP-1 preserved osteoporosis associated with hyperglycemia by inhibiting α-glucosidase activity, improving glucose tolerance, decreasing the accumulation of advanced glycation end products (AGEs), as well as down-regulating the expression of receptor for AGEs in tibias of streptozotocin-induced diabetic rats. Collectively, the present study suggested that the arabinogalactan PPCP-1 from Phellodendron chinense Schneid. might potentially be used as functional foods for bone health and/or developed for drug discovery for alleviating diabetic osteoporosis.

Plants arabinogalactans: From structures to physico-chemical and biological properties

Arabinogalactans (AGs) are plant heteropolysaccharides with complex structures occasionally attached to proteins (AGPs). AGs in cell matrix of different parts of plant are freely available or chemically bound to pectin rhamnogalactan. Type I with predominantly β-d-(1 → 4)-galactan and type II with β-d-(1 → 3) and/or (1 → 6)-galactan structural backbones construct the two main groups of AGs. In the current review, the chemical structure of AGs is firstly discussed focusing on non-traditional plant sources and not including well known industrial gums. After that, processes for their extraction and purification are considered and finally their techno-functional and biological properties are highlighted. The role of AG structure and function on health advantages such as anti-tumor, antioxidant, anti-ulcer- anti-diabetic and other activites and also the immunomodulatory effects on in-vivo model systems are overviewed.

Protective effect of the isolated oligosaccharide from Rosa canina in STZ-treated cells through modulation of the autophagy pathway

Isolation of active components of therapeutic plants and discovering molecular mechanisms play a pivotal role in therapy of diabetes. This study aimed to determine the antidiabetic mechanism of an oligosaccharide isolated from Rosa canina (RCO) by measuring the expression of some miRNAs and their targets involved in autophagy. RCO was extracted and characterized by using HPLC and spectroscopic methods. Rin-5F cells were treated with STZ and RCO alone and in combination. The viability of the cells and the expression of miR-21, miR-22, Akt, ATG5, Beclin1, LC3A, and LC3B were analyzed using MTT assay, and qRT-PCR, respectively. Oligosaccharide fraction could improve the viability of RCO-treated cells as compared to STZ-treated cells. Further, the expression of autophagy markers was increased in RCO-treated diabetic cells compared to STZ-treated cells. The results indicated that the antidiabetic effects of the oligosaccharide components of R. canina seem to be mediated by modulation of autophagy pathway. PRACTICAL APPLICATIONS: Given effectiveness of an oligosaccharide fraction isolated from Rosa canina in management of diabetes in STZ-induced diabetic rats, we have intention to scrutinize its molecular mechanism as modulation of autophagy pathway in STZ-treated Rin-5F cells. It is expected that the results paved the way to speculate novel antidiabetic strategies.

A Systematic Review of Phytochemistry, Pharmacology and Pharmacokinetics on Astragali Radix: Implications for Astragali Radix as a Personalized Medicine

Astragali radix (AR) is one of the most widely used traditional Chinese herbal medicines. Modern pharmacological studies and clinical practices indicate that AR possesses various biological functions, including potent immunomodulation, antioxidant, anti-inflammation and antitumor activities. To date, more than 200 chemical constituents have been isolated and identified from AR. Among them, isoflavonoids, saponins and polysaccharides are the three main types of beneficial compounds responsible for its pharmacological activities and therapeutic efficacy. After ingestion of AR, the metabolism and biotransformation of the bioactive compounds were extensive in vivo. The isoflavonoids and saponins and their metabolites are the major type of constituents absorbed in plasma. The bioavailability barrier (BB), which is mainly composed of efflux transporters and conjugating enzymes, is expected to have a significant impact on the bioavailability of AR. This review summarizes studies on the phytochemistry, pharmacology and pharmacokinetics on AR. Additionally, the use of AR as a personalized medicine based on the BB is also discussed, which may provide beneficial information to achieve a better and more accurate therapeutic response of AR in clinical practice.

Effect of gamma irradiation on structure, physicochemical and immunomodulatory properties of Astragalus polysaccharides

Astragalus polysaccharides (APS) were treated with different gamma irradiation doses (10, 25, 50, 100 and 150 kGy) to investigate the effects of gamma radiation processing on structure, physicochemical and immunomodulatory properties. The results revealed both the number-average and weight-average molecular weight of APS significantly decreased with increasing irradiation dose, whereas the solubility was increased after irradiation. A decrease in the apparent viscosity, as well as an increase in amount of small fragments of APS granules was also observed with increasing irradiation dose. FT-IR spectra indicated that gamma irradiation introduced no significant changes into the functional group status of APS. High irradiation dose (>50 kGy) caused a significant increase of yellowness and a slightly decrease of thermal stability of APS. Further, the immunomodulatory activity of irradiated APS was evaluated on Caco2 cells. APS irradiated at dose of 25 kGy exhibited the highest ability to induce nitric oxide production and up-regulate the mRNA expression of inflammatory cytokines, occludin, zonula occludens protein-1 (ZO-1) and toll-like receptor 4 (TLR4), as well as the protein expression of ZO-1 and TLR4. These findings indicate that gamma irradiation modification with a proper dose enhance immunomodulatory activity of APS by improving physicochemical properties without changing the functional groups.

Characteristics and intestinal immunomodulating activities of water-soluble pectic polysaccharides from Chenpi with different storage periods

BACKGROUND

The traditional view considers that Chenpi (dried citrus peel) stored over the long-term has better health efficacies compared to fresh Chenpi, although the detailed mechanism responsible for this remains obscure.

RESULTS

The three water-soluble pectic polysaccharides (CPP1, CPP5 and CPP10) were obtained from 1-, 5- and 10-year Chenpi, respectively, and their physicochemical characteristics and intestinal immunomodulating activities were investigated and compared. The results obtained showed that CPP5 and CPP10 demonstrated a lower dynamic viscosity and degree of methylesterification, as well as a higher molecular heterogeneity, compared to CPP1. Monosaccharide composition analysis indicated that CPP1 was composed of arabinose, galacturonic acid and galactose, and a small amount of rhamnose; however, CPP5 and CPP10 consisted of arabinose, galacturonic acid, galactose, glucose and xylose, and a small amount of rhamnose. With the extension of storage period of Chenpi, the content of soluble conjugate phenolic acids increased in the pectic polysaccharide. Furthermore, it was confirmed that the pectic polysaccharides extracted from the 5-year and 10-year Chenpi could significantly enhance the proliferation of bone marrow cells via activating the Peyer's patch cells in vitro.

CONCLUSION

The present study demonstrates the differences in the pectic polysaccharides from Chenpi with different storage periods and also confirms that the pectic polysaccharides extracted from Chenpi stored over the long-term had more significant intestinal activities compared to that obtained from the fresh Chenpi. This phenomenon might partly explain why the Chenpi stored over the long-term has better healthcare effects. © 2018 Society of Chemical Industry.

Extraction of a Novel Cold-Water-Soluble Polysaccharide from Astragalus membranaceus and Its Antitumor and Immunological Activities

The polysaccharides of Astragalus membranaceus have received extensive study and attention, but there have been few reports on the extraction of these polysaccharides using cold water (4 °C). In this study, we fractionated a novel cold-water-soluble polysaccharide (cAMPs-1A) from Astragalus membranaceus with a 92.00% carbohydrate content using a DEAE-cellulose 52 anion exchange column and a Sephadex G-100 column. Our UV, Fourier-transform infrared spectroscopy (FTIR), high-performance gel permeation chromatography, and ion chromatography analysis results indicated the monosaccharide composition of cAMPs-1A with 1.23 × 10⁴ Da molecular weight to be fucose, arabinose, galactose, glucose, and xylose, with molar ratios of 0.01:0.06:0.20:1.00:0.06, respectively. The UV spectroscopy detected no protein and nucleic acid in cAMPs-1A. We used FTIR analysis to characterize the α-d-pyranoid configuration in cAMPs-1A. In addition, we performed animal experiments in vivo to evaluate the antitumor and immunomodulatory effects of cAMPs-1A. The results suggested that cAMPs-1A oral administration could significantly inhibit tumor growth with the inhibitory rate of 20.53%, 36.50% and 44.49%, respectively, at the dosage of 75,150, and 300 mg/kg. Moreover, cAMPs-1A treatment could also effectively protect the immune organs, promote macrophage pinocytosis, and improve the percentages of lymphocyte subsets in the peripheral blood of tumor-bearing mice. These findings demonstrate that the polysaccharide cAMPs-1A has an underlying application as natural antitumor agents.

New findings on green sweet pepper (Capsicum annum) pectins: Rhamnogalacturonan and type I and II arabinogalactans

Polysaccharides were extracted from sweet pepper (Capsicum annum) with hot water and named ANW (9% yield). Starch was precipitated by freeze-thaw treatment, while pectic polysaccharides (8% yield) remained soluble and consisted of GalA (67.0%), Rha (1.6%), Ara (6.4%), Xyl (0.3%), Gal (6.7%) and Glc (4.4%). A highly methoxylated homogalacturonan (HG, degree of methylesterification of 85% and degree of acetylation of 5%), and type I and type II arabinogalactans (AG-I and AG-II) were observed in NMR analyses. These were fractionated with Fehling's solution to give HG (5.5% yield) and AG fractions (0.6% yield). AG-I and AG-II were further separated by ultrafiltration. AG-II (0.2% yield) consisted of Ara (17.1%), Gal (36.0%), Rha (5.6%) and GalA (12.0%), had a molecular weight of 5.3×10⁴g/mol and methylation and ¹H/¹³C HSQC-DEPT-NMR analyses showed that it was anchored in type I rhamnogalacturonan. This is the first study that reports the presence of AG-I and AG-II in sweet pepper fruits.

Cycloartane-type triterpenoids from Astragalus hoantchy French

A new cycloartane-type triterpenoid, 3β-acetoxy-9β,19-cyclolanost-24E-ene-1α,16β-diol-27-O-β-d-glucopyranoside (1), together with three known ones (2-4) were isolated from the aerial parts of Astragalus hoantchy. The structure of compound 1 was elucidated by detailed spectroscopic analyses including 1D and 2D NMR, HRESIMS, and IR experiments. All of the four compounds were isolated from A. hoantchy for the first time. The antifungal activities of compounds 1-4 against a phytopathogenic fungus (Alternaria solani) were evaluated with the result that compound 3 exhibited a moderate activity with an IC₅₀ value of 284 μg/mL.