Partially methylated galactans containing different proportions of 3-O-methyl-galactose from Pleurotus citrinopileatus

Polysaccharide fractions extracted from Lactarius quieticolor mushroom exhibit immune stimulatory activities on macrophages

Several beneficial properties have already been observed for mushrooms extracts containing polysaccharides, one of the main components present in these fungi. In order to obtain these extracts and clarify their composition, different extraction and characterization methods can be applied, contributing to understanding its biological effects. In this research, we evaluated three different crude fractions obtained through cold water, hot water, and alkaline solution, from the mushroom Lactarius quieticolor. Each sample was totally characterized by NMR (1H, 13C, HSQC-DEPT, COSY), GC-MS (monosaccharide composition and methylation analysis) and HPSEC (homogeneity and relative Mw). The results showed a mixture of different polysaccharides, including D-galactans and D-glucans in each fraction. All the extracts presented immunostimulant activity in murine RAW 264.7 macrophages, stimulating NO secretion and inducing morphological alterations that were typical of activated cells. These effects were more intense for alkaline fraction (EA), which have higher amounts of mannose and 3,6-di-O-substituted-Glcp units. The results obtained show that crude fractions can potentially stimulate immune cells, which indicates that the consumption of this edible mushroom can bring great benefits to health, being considered an excellent food due to its good biological properties.

Lipopolysaccharides from a Shiraia fruiting body-associated bacterium elicit host fungal hypocrellin A biosynthesis through nitric oxide generation

Hypocrellin A (HA) is an excellent perylenequinone photosensitizer from Shiraia fruiting bodies. A dominant bacterium Pseudomonas fulva SB1 in the fruiting body was found to promote HA biosynthesis. The bacterial LPS were purified and the O-specific polysaccharide (OPS) consisted of rhamnose (Rha), galactose (Gal) and N-acetyl-galactosamine (GalNAc) with an average molecular weight of 282.8 kDa. Although the OPS composing of Rhap and Galp backbone showed elicitation capability on fungal HA accumulation, the highest HA production (303.76 mg/L) was achieved by LPS treatment at 20 μg/mL on day 3 of the mycelium culture. The generation of nitric oxide (NO) in Shiraia mycelia was triggered by LPS, which was partially blocked by inhibitors of nitric oxide synthase (NOS) and nitrate reductase (NR), leading to the depressed HA production. Transcriptome analysis revealed that NO mediated LPS-induced HA production via upregulating the expressions of critical genes associated with central carbon metabolism and downstream HA biosynthesis genes. This is the first report of LPS-induced NO to regulate fungal secondary metabolite production, which provides new insights on the role of bacterial LPS in bacterium-fungus interactions and an effective strategy to enhance hypocrellin production.

Neuroprotection of low-molecular-weight galactan obtained from Cantharellus cibarius Fr. against Alzheimer's disease

The large molecular weight of polysaccharides limits their absorption and utilization by organisms, affecting their biological activities. In this study, we purified α-1,6-galactan from Cantharellus cibarius Fr. (chanterelle) and reduced its molecular weight from approximately 20 kDa to 5 kDa (named CCP) to increase its solubility and absorption. In APP/PS1 mice, CCP improved both spatial and non-spatial memory loss in Alzheimer's disease (AD) mice, as confirmed by the Morris water maze, step-down, step-through, and novel object recognition tests, and dampened the deposition of amyloid-β plaques, as assessed by immunohistochemical analysis. Proteomic analysis suggested that the neuroprotective effects of CCP are related to anti-neuroinflammation. Immunofluorescence analysis and western blotting confirmed that CCP attenuated AD-like symptoms partly by inhibiting neuroinflammation, which was related to the blocking of complement component 3. Our study provides theoretical support and experimental evidence for the future application of chanterelle-extracted polysaccharides in AD treatment, promoting the modern development of traditional medicines originating from natural polysaccharides.

Structural Characterization and Anticoagulant Activity of a 3-O-Methylated Heteroglycan From Fruiting Bodies of Pleurotus placentodes

Pleurotus placentodes, a fungus, belongs to the Pleurotaceae family. The aim of the present study was to characterize the structure of a novel polysaccharide from fruiting bodies of P. placentodes (PPp-W) and evaluate its anticoagulant activity in vitro. The high-performance liquid chromatography and GC–MS analysis indicated that PPp-W with a molecular weight of 27.4 kDa was mainly composed of mannose (17.56%), glucose (6.37%), galactose (44.89%), and fucose (1.22%) with a certain amount of 3-O-methyled galactose. SEM, XRD, and AFM combined with Congo red test revealed that PPp-W was an irregular curly sheet with triple-helix conformation. The FT-IR, methylation, and nuclear magnetic resonance analysis indicated that PPp-W contained→6)-α-D-Galp-(1→, →6)-3-O-Me-α-D-Galp-(1→and →2, 6)-α-D-Galp-(1→ as main chain, partially substituted at O-2 and O-6 by non-reducing ends of β-D-Manp-(1→ and β-L-Fucp-(1→ with a small amount of α-1,3-linked-Glcp in backbone. PPp-W could significantly prolong APTT (12.9 ± 0.42 s, p < 0.001) and thrombin time (39.9 ± 0.28 s, p < 0.01) compared with the control group (11.45 ± 0.071 s and 38.05 ± 0.21 s), which showed that PPp-W had anticoagulant activity. These studies suggested that PPp-W was a 3-O-methylated heteroglycan and might be suitable for functional foods and natural drugs as an anticoagulant ingredient, which provided a basis for the application of polysaccharides from P. placentodes.

An α-D-galactan and a β-D-glucan from the mushroom Amanita muscaria: Structural characterization and antitumor activity against melanoma

Polysaccharides α-D-galactan (GAL-Am) and β-D-glucan (GLC-Am) were obtained from Amanita muscaria fruiting bodies. They were purified using different methodologies, such as Fehling precipitation (for both fractions), freeze-thawing process and ultrafiltration (for GLC-Am). Results showed that the GAL-Am has (1 → 6)-linked Galp main chain branched at O-2 by terminal Galp units and has not been previously reported. Besides, GLC-Am has (1 → 3)-linked Glcp in the main chain, substituted at O-6 by (1 → 6)-linked β-Glcp units. Both are water-soluble, with 9.0 × 10³ g/moL and 1.3 × 10⁵ g/moL, respectively. GAL-Am and GLC-Am presented a selective proliferation reduction against B16-F10 melanoma cell line, not affecting non tumoral BALB/3T3 fibroblast cell line. Furthermore, both fractions reduced clonogenic capacity of melanoma cell line over an extended period of time. These results were obtained without modulations in B16-F10 cell adhesion, reinforcing the biological activities towards cell proliferation impairment and eliciting these polysaccharides as promising compounds to further exploration of their antimelanoma properties.

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

Plant cell wall polysaccharide analysis encompasses the utilization of a variety of analytical tools, including gas and liquid chromatography, mass spectrometry (MS), and nuclear magnetic resonance (NMR) spectroscopy. These methods provide complementary data, which enable confident structural proposals of the many complex polysaccharide structures that exist in the complex matrices of plant cell walls. However, cell walls contain fractions of varying solubilities, and a few techniques are available that can analyze all fractions simultaneously. We have discovered that permethylation affords the complete dissolution of both soluble and insoluble polysaccharide fractions of plant cell walls in organic solvents such as chloroform or acetonitrile, which can then be analyzed by a number of analytical techniques including MS and NMR. In this work, NMR structure analysis of 10 permethylated polysaccharide standards was undertaken to generate chemical shift data providing insights into spectral changes that result from permethylation of polysaccharide residues. This information is of especial relevance to the structure analysis of insoluble polysaccharide materials that otherwise are not easily investigated by solution-state NMR methodologies. The preassigned NMR chemical shift data is shown to be vital for NMR structure analysis of minor polysaccharide components of plant cell walls that are particularly difficult to assign by NMR correlation data alone. With the assigned chemical shift data, we analyzed the permethylated samples of destarched, alcohol-insoluble residues of switchgrass and poplar by two-dimensional NMR spectral profiling. Thus, we identified, in addition to the major polysaccharide components, two minor polysaccharides, namely, <5% 3-linked arabinoxylan (switchgrass) and <2% glucomannan (poplar). In particular, the position of the arabinose residue in the arabinoxylan of the switchgrass sample was confidently assigned based on chemical shift values, which are highly sensitive to local chemical environments. Furthermore, the high resolution afforded by the ¹H NMR spectra of the permethylated switchgrass and poplar samples allowed facile relative quantitative analysis of their polysaccharide composition, utilizing only a few milligrams of the cell wall material. The concepts herein developed will thus facilitate NMR structure analysis of insoluble plant cell wall polysaccharides, more so of minor cell wall components that are especially challenging to analyze with current methods.

Polysaccharides of mushroom Pleurotus spp.: New extraction techniques, biological activities and development of new technologies

The biodiversity of mushrooms Pleurotus spp. is impressive due to its complexity and diversity related to the composition of chemical structures such as polysaccharides, glycoproteins and secondary metabolites such as alkaloids, flavonoids and betalains. Recent studies of polysaccharides and their structural elucidation have helped to direct research and development of technologies related to pharmacological action, production of bioactive foods and application of new, more sophisticated extraction tools. The diversity of bioactivities related to these biopolymers, their mechanisms and routes of action are constant focus of researches. The elucidation of bioactivities has helped to formulate new vaccines and targeted drugs. In this context, in terms of polysaccharides and the diversity of mushrooms Pleurotus spp., this review seeks to revisit the genus, making an updated approach on the recent discoveries of polysaccharides, new extraction techniques and bioactivities, emphasising on their mechanisms and routes in order to update the reader on the recent technologies related to these polymers.

Neutral Polysaccharide from the Leaves of Pseuderanthemum carruthersii: Presence of 3-O-Methyl Galactose and Anti-Inflammatory Activity in LPS-Stimulated RAW 264.7 Cells

Pseuderanthemum carruthersii (Seem.) Guillaumin is a native tree in Vietnam. The water extract of the leaves from this tree gives a highly viscous product that has been used to heal wounds and treat inflammations. Our previous studies showed that the leaves of P. carruthersii have a high content of polysaccharides. In this study, the structure and influence of the neutral polysaccharide from Pseuderanthemum carruthersii (PCA1) on lipopolysaccharide (LPS)-stimulated RAW264.7 cells were investigated. The PCA1 isolated from P. carruthersii is a galactan-type polysaccharide, containing galactose (77.0%), 3-O-methyl galactose (20.0%), and arabinose (3.0%). Linkage analysis of PCA1 showed that both the 3-O-methyl galactose and galactose were 1,4-linked. The presence of 3-O-methyl galactose units as part of the polysaccharide is important and can be used as a chemotaxonomic marker. The molecular weight of the PCA1 was 170 kDa. A PCA1 concentration of 30–40 μg/mL strongly inhibited TNFα, IL-1β, and IL-6 inflammatory cytokine production, and reactive oxygen species (ROS) release. PCA1 had inhibitory activities on pro-inflammatory cytokine and ROS release in LPS-stimulated mouse macrophages in vitro through MAPK signaling.