Physicochemical, morpho-structural, and biological characterization of polysaccharides from three Polygonatum spp.

Polygonatum species, including P. cyrtonema, P. kingianum, and P. sibiricum, are edible plants with medicinal purposes, which have long been consumed as food due to their high nutritional value. In this study, polysaccharides from P. cyrtonema (PCP), P. kingianum (PKP) and P. sibiricum (PSP) were obtained, and their physicochemical properties and in vitro biological activities were investigated. Our results demonstrated that PCP, PKP, and PSP consist of major fructose and minor glucose, galacturonic acid, and galactose in different molar ratios with the molecular weights of 8.5 × 103 Da, 8.7 × 103 Da, and 1.0 × 104 Da, respectively. The three polysaccharides had triple-helical structures with ß-d-Fruf, α-d-Glcp, α-d-Galp sugar residues, and an O-acetyl group, and displayed peak-shaped structures in different sizes. They also exhibited thermal, shear-thinning behavior and viscoelastic properties, and PCP presented the highest viscoelasticity. Moreover, they exerted strong free radical-scavenging abilities, and significant reducing capacity. PCP was the strongest, followed by PSP and then PKP. They significantly promoted the polarization of the M1 macrophage, with the effect of PCP ranking first. All three had similar effects on GLP-1 secretion. It is, therefore, necessary to identify the various roles of these three Polygonatum polysaccharides as functional agents based on their bioactivities and physicochemical properties.

Polygonatum cyrtonema Hua Polysaccharide Promotes GLP-1 Secretion from Enteroendocrine L-Cells through Sweet Taste Receptor-Mediated cAMP Signaling.

Glucagon-like peptide-1 (GLP-1) secreted from enteroendocrine L-cells is a pleiotropic hormone with beneficial potential related to islet function, diet control, glucose homeostasis, inflammation relief, and cardiovascular protection. The present study aimed at investigating the effect of Polygonatum cyrtonema polysaccharide (PCP) after structural identification on GLP-1 secretion and the possible mechanism involved in the PCP-stimulated secretion of GLP-1. It was found that GLP-1 secretion was effectively promoted (p < 0.01) by PCP both in rats with oral administration for 5 weeks (13.9 ± 0.3-35.8 ± 0.3 pmol/L) and ileal administration within 2 h (13.6 ± 0.4-34.1 ± 1.1 pmol/L) and in enteroendocrine NCI-H716 cells with direct stimulation within 24 h (2.05 ± 0.3-20.7 ± 0.2 pmol/L). The sweet taste receptor T1R2/T1R3 was identified to be essential for NCI-H716 cells to directly recognize PCP. The intervention experiments showed that PCP-stimulated GLP-1 secretion was significantly depressed (p < 0.01) not only by antibodies, siRNA, and the inhibitor of T1R2/T1R3 but also by an adenylate cyclase inhibitor. These results suggest that PCP stimulates GLP-1 secretion from enteroendocrine cells possibly through activation of the T1R2/T1R3-mediated cAMP signaling pathway.

Structural features of an acidic polysaccharide with the potential of promoting osteoblast differentiation from Lycium ruthenicum Murr.

The enhanced osteoblast differentiation is beneficial to the prevention of osteoporosis. In this study, a homogeneous polysaccharide (LRP-S2A) with the potential of promoting osteoblast differentiation was obtained from the fruits of Lycium ruthenicum, a traditional herb for treatment of postmenopausal metabolic disorders. Structural identification indicated that LRP-S2A, with a relative molecular weight of 2.65 × 106 Da and an uronic acid content of 41.8%, contained Rha, Ara, Gal, Glc and GlcA in a molar ratio of 1.00 : 2.07 : 0.57 : 2.59 : 4.33 and was composed of a backbone consisting of 6-O-Me-α-(1→4)-D-GlcpA, 2-O-acetyl-α-(1→4)-D-Glcp, α-(1→2,4)-L-Rhap, ß-(1→3)-D-Galp andα-(1→3,5)-L-Araf, and some branches consisting of 6-O-Me-α-(1→4)-D-GlcpA and terminal α-L-Araf. These results suggested that LRP-S2A with the potential of promoting osteoblast differentiation was a new acidic polysaccharide.

Dendrobium huoshanense polysaccharide regulates intestinal lamina propria immune response by stimulation of intestinal epithelial cells via toll-like receptor 4.

A homogenous polysaccharide (GXG) from Dendrobium huoshanense with stable digestive behavior and effective immunoregulatory function was employed to explore its underlying molecular basis regulating intestinal mucosal immune response from the view of interaction between GXG and intestinal epithelial cells (IECs). Using in vitro established co-culture system consisting of IECs and lamina propria cells (LPCs), we found the immune response of LPCs could be effectively regulated by GXG-stimulated IECs, and three cytokines including IL-6, MCP-1 and CINC-1 produced from GXG-stimulated IECs were the main factors involved in modulating immune response of LPCs. Toll-like receptor 4 (TLR4) was identified as an essential receptor for IECs to directly bind GXG. Receptor intervention experiments demonstrated that TLR4 mediated GXG-induced activation of IECs, which further induces immunomodulating effects on LPCs. These results suggest that GXG could modulate the immune response in LPCs by the direct interaction with IECs via TLR4.

Dendrobium huoshanense polysaccharide regionally regulates intestinal mucosal barrier function and intestinal microbiota in mice.

The present study investigated the effects of a homogeneous Dendrobium huoshanense polysaccharide (GXG) on mucosal barrier function and microbiota composition in different intestinal regions of mice. Results exhibited, besides changing the intestinal physiological status, orally administrated GXG could improve the intestinal physical barrier function by modulating mucosal structures and up-regulating the expression of tight junction proteins, reinforce the intestinal biochemical barrier function by elevating the expression and secretion of mucin-2, ß-defensins and sIgA, and regulate the intestinal immunological barrier function by stimulating the production of cytokines and the functional development of immune cells. Simultaneously, GXG could differentially impact the composition and metabolism of microbiota along intestinal tract. In addition, the immune response in spleen and peripheral blood were effectively regulated by GXG. These results indicated that GXG might be used as functional agent to improve host health.

Digestive behavior of Dendrobium huoshanense polysaccharides in the gastrointestinal tracts of mice.

With fluorescent end-labeling method, a homogenous Dendrobium huoshanense polysaccharide (GXG) that was orally administrated to mice was found to be degraded into a stable fragment (dGXG) in the stomach, where dGXG was propelled into the small intestine and absorbed into the systemic circulation. The residual GXG in the stomach could pass through the gastrointestinal tract and was excreted into faeces with a very slow fermentation in the large intestine. The simulated digestion of GXG indicated that the acidic pH condition in the gastric fluid was responsible for GXG degradation, which was supported by the oral digestion of dGXG. Chemical analysis not only showed a change in the molar ratio of monosaccharide compositions and glycosidic linkage types, but also found the loss of the sugar residue (1→4)-linked Galp after the acid treatment of GXG, suggesting that the cleavage of glycosidic linkage, especially (1→4)-linked Galp linkage, resulted in GXG degradation in the gastrointestinal tract.

Intestinal immunomodulating activity and structural characterization of a new polysaccharide from stems of Dendrobium officinale.

A homogeneous polysaccharide fraction (DOP-W3-b) with a high intestinal immunomodulating activity was obtained from the stems of Dendrobium officinale through a bioactivity-guided sequential isolation procedure based on the screening of Peyer's patch-mediated immunomodulating activity. Oral administration experiments of mice showed that DOP-W3-b could effectively regulate intestinal mucosal immune activity by changing intestinal mucosal structures, promoting the secretions of cytokines from Peyer's patches (PPs) and mesenteric lymph nodes (MLNs), and increasing the production of secretory immunoglobulin A (sIgA) in the lamina propria. Structure analysis indicated that DOP-W3-b was composed of mannose and glucose in a molar ratio of 4.5 with a relatively low molecular weight of 1.543 × 10(4) Da, and its repeat unit contained a backbone consisting of ß-(1→4)-d-Manp, ß-(1→4)-d-Glcp and ß-(1→3,6)-d-Manp residues, a branch consisting of ß-(1→4)-d-Manp, ß-(1→4)-d-Glcp and terminal ß-d-Glcp, and O-acetyl groups attached to O-2 of ß-(1→4)-d-Manp. These results suggested that DOP-W3-b was a new polysaccharide with an essential potential for modulating body's immune functions.

Polysaccharide of Dendrobium huoshanense activates macrophages via toll-like receptor 4-mediated signaling pathways.

The present work aimed at investigating the pattern recognition receptor (PRR) and immunostimulatory mechanism of a purified Dendrobium huoshanense polysaccharide (DHP). We found that DHP could bind to the surface of macrophages and stimulate macrophages to secrete NO, TNF-α and IL-1ß. To unravel the mechanism for the binding of DHP to macrophages, flow cytometry, confocal laser-scanning microscopy, affinity electrophoresis, SDS-PAGE and western blotting were employed to verify the type of PRR responsible for the recognition of DHP by RAW264.7 macrophages and peritoneal macrophages of C3H/HeN and C3H/HeJ macrophages. Results showed that toll-like receptor 4 (TLR4) was an essential receptor for macrophages to directly bind DHP. Further, the phosphorylation of ERK, JNK, Akt and p38 were observed to be time-dependently promoted by DHP, as well as the nuclear translocation of NF-κB p65. These results suggest that DHP activates macrophages via its direct binding to TLR4 to trigger TLR4 signaling pathways.