Structural characterization and immunoregulatory activity of polysaccharides from Dendrobium officinale leaves

Abstract

In this study, two kinds of polysaccharides from leaves of Dendrobium officinale, namely DLP‐1 and DLP‐2, were obtained by hot water extraction, ethanol sedimentation, and chromatographic separation using DEAE‐52 cellulose and Sephadex G‐100 columns. They were composed of different monosaccharides and the content of monosaccharides varied significantly while DLP‐1 (Mw 1.38 × 106 Da) was mainly composed of mannose (71.69%) and glucose (22.89%), and DLP‐2 (Mw 1.93 × 106 Da) was constituted by rhamnose (35.05%), arabinose (24.12%), and galactose (25.65%). A triple‐helical conformation was exhibited by both of them. The scanning electron microscope image of DLP‐1 showed an irregular and large lamellar shape, as well as a smooth surface and a porous interior, illustrating they had an amorphous structure. In contrast, DLP‐2 revealed a rough, loose, and uneven surface consisting of large sponge‐like particles. Nuclear magnetic resonance analysis showed that (1→4)‐β‐D‐Manp, (1→4)‐β‐D‐Glcp, and (1→4)‐2‐O‐acetyl‐β‐D‐Manp were the main linkage types of DLP‐1, whereas DLP‐2 was constituted by a large amount of (1→4)‐β‐D‐Manp, (1→4)‐β‐D‐Glcp, and other residues. Besides, DLP‐1 and DLP‐2 stimulated the proliferation and phagocytic capacities of RAW 264.7 cells and improved the production of nitric oxide, interleukin‐6, TNF‐α, and IL‐1β. These results proved that both DLP‐1 and DLP‐2 possessed excellent immunoregulatory bioactivities and could be functional food or adjuvant drug. Practical applications The leaf of Dendrobium officinale is a by‐product with huge biomass. The lack of systematic research on its chemical composition and pharmacologic effect, leading to a great waste of resources. In order to maximize the value of D. officinale, this study aimed to investigate the structural characteristics and immunologic effects of two polysaccharide fractions (DLP‐1 and DLP‐2) from D. officinale leaves, showing that DLP‐1 and DLP‐2 in D. officinale leaves could be used as anti‐inflammatory agents to avoid wasting.

Physicochemical property changes of Dendrobium officinale leaf polysaccharide LDOP‐A and it promotes GLP‐1 secretion in NCI‐H716 cells by simulated saliva‐gastrointestinal digestion

“…Polysaccharide was the main component in Dendrobium Officinale leaf, the contents were measured as 8.99-16.55%, respectively (Zhou et al, 2014), while the total flavonoid contents in D. officinale leaves collected only ranged from 7.66 to 9.50 mg/g dried weight (Zhong et al, 2022). Therefore, understanding the digestive characteristics of polysaccharides is conducive to the in-depth study of their functions.…”

Research progress on extraction, purification, structure and biological activity of Dendrobium officinale polysaccharides

“…At present, the advanced structure characterization of polysaccharide mainly includes Congo red experiment, SEM, AFM, circular dichroism, and X-ray diffraction (XRD) ( 36 , 44 ). Zhong et al ( 51 ) isolated two polysaccharides (DLP-1 and DLP-2) from D. officinale leaves, both of which could form complexes with Congo red in the Congo red experiment, indicating that DLP-1 and DLP-2 had triple helices structure. Besides, the surface structure of DLP-1 was irregular large flakes with smooth surface and porous interior.…”

“…Moreover, the immunomodulatory activity of DLP-2 was higher than that of DLP-1 at the same concentration. Thus, DLP-1 and DLP-2 could be used as functional food additives ( 51 ). Similarly, DCP also has immunostimulatory activity in vitro , the mechanism of which was similar to that of DLP-1 and DLP-2 ( 53 ).…”

Glucomannan in Dendrobium catenatum: Bioactivities, Biosynthesis and Perspective

“…D. catenatum polysaccharide DOPW3-B can improve the intestinal mucosal immune activity by increasing at Peyer’s patches the levels of interferon-γ (IFN-γ) and interleukin-4 (IL-4), two key effector cytokines for the differentiation of T helper types 1 and 2 with a positive effect on mesenteric lymph nodes [ 31 , 53 ]. Glucomannan can increase the expression of several cytokines that are important for immune homeostasis (e.g., TNF-α, IL-β and IL-10) [ 54 ]. Meanwhile, glucomannan plays a pivotal role in regulating the activation and proliferation of macrophages [ 55 ], and promoting phagocytosis [ 29 ].…”