Structure and Bioactivities of a Novel Polysaccharide Extracted From Dendrobium huoshanense by Subcritical Water

Abstract

In this study, the polysaccharide was extracted by subcritical water from Dendrobium huoshanense. A novel polysaccharide (DHPs-1) was obtained through several purification steps and its structure and bioactivity were investigated. Structural analysis indicated that the weight-average molecular weight of DHPs-1 was 5.0 × 10⁴ Da and it was mainly composed of glucose (65.04%), mannose (14.23%), galactose (8.17%), galacturonic acid (6.41%), rhamnose (2.34%), and xylose (1.25%). 1,4-Glcp, and 1,4,6-Galp were existed in the backbone of DHPs-1. The residues of 1,3,4-Galp, 1,4-Manp, 1,4-Galp, and 1,3,4,6-Galp could be in the backbone or the side chains with the non-reducing terminal of α-Manp. Bioactivity tests indicated that DHPs-1 had immunomodulatory activity in that it significantly enhanced transcript levels of cytokines [Tumor necrosis factor-α (TNF-α), Interleukin-6 (IL-6), Interleukin-1β (IL-1β), and Interleukin-10 (IL-10)]. DPPH and hydroxyl radical scavenging tests showed that it had good antioxidant activity. These results reveal that DHPs-1 could be developed as a safe immunomodulatory agent and antioxidant for pharmacological or functional food applications.

Keywords: Dendrobium huoshanense; bioactivities; polysaccharide; structure; subcritical water.

Figure 1

Elution curve of DHPs-1 on DEAE-52 (A); FT-IR spectrum of DHPs-1 (B).

Figure 2

The spectra of DHPs-1: (A) ¹H; (B) ¹³C; (C) HSQC; (D) COSY; (E) HMBC; (F) ROESY.

Figure 3

SEM images of DHPs-1 (A₁, A₂: different magnification of the same region; B1, B2: different magnification of the same region; A₁, B₁, 800×; A₂ B₂, 1,000×).

Figure 4

TG, DTG, and DSC curves of DHPs-1.

Figure 5

Antioxidant activity of DPHs-1. (A) DPPH radical scavenging assay; (B) Hydroxyl radical scavenging activity.

Figure 6

Effect of DHPs-1 on the viability of RAW264.7 cells.

Figure 7

Effects of DHPs-1 on the expression of cytokine genes in RAW264.7 cells (A–D): Expression of TNF-α (A), IL-1β (B), IL-6 (C), and IL-10 (D) mRNA in RAW264.7 cells treated with DHPs-1 or LPS groups for 12 h. Significant differences from control group are denoted by *p < 005, **p < 0.01, ***p < 0.001.