Characteristics and properties of a polysaccharide isolated from Wolfiporia cocos as potential dietary supplement for IBS

Abstract

Introduction: As low FODMAP (Fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet therapy is recommended for most of Irritable Bowel Syndrome (IBS) patients, the consequent insufficient of dietary fibers (DFs) intake exert an adverse impact on intestinal health. It is necessary to find suitable DFs for IBS patients.

Methods: This study extracted a water-insoluble polysaccharide from Wolfiporia cocos (WIP) by alkali-extraction and acid-precipitation method. Its molecular weight was detected by high performance gel permeation chromatography (HPGPC) analysis. The structure of WIP was analyzed by Fourier transform infrared (FT-IR) spectrum, Nuclear Magnetic Resonance (NMR) spectra and X-ray diffraction (XRD). The properties related to stability, digestion, viscosity, osmotic activity, adsorption and fermentation were investigated, aimed to explore the feasibility of WIP as a new DF supplement for patients with IBS. In addition, 16S rRNA sequencing analysis was conducted to explore its effects on IBS-related gut microbiota.

Results and discussion: The results showed that WIP had a single homogeneous composition and the molecular weight was 8.1 × 10³ Da. WIP was indicated as a kind of pyranose form with β anomeric configuration and the main chain of WIP was 1,3-β-glucan with amorphous structure. In addition to good thermal stability, WIP also has low bioavailability and can reach the colon mostly without being digested. Moreover, the low viscosity and osmotic activity, the high water- swelling and water/oil-holding capacity, fructose adsorption capacity and poor fermentation performance of WIP demonstrated that it is suitable for IBS patients. It is worth noting that WIP regulates IBS associated gut microbiota effectively, such as the abundance of Lachnospiraceae and Prevotella. These findings provide a theoretical basis for the development of WIP as a dietary supplement for IBS patients with low FODMAP diet therapy. GRAPHICAL ABSTRACT.

Keywords: Wolfiporia cocos; diet therapy; gut microbiota; in vitro digestion; in vitro fermentation; irritable bowel syndrome; polysaccharide.

GRAPHICAL ABSTRACT

Figure 1

HPGPC analysis of WIP. (A) Molecular weight of WIP, (B) peak of mobile phase.

Figure 2

Structural characterization of WIP. (A) FT-IR, (B) ultraviolet spectrogram, (C) 1H spectrum in DMSO-d6, (D) 13C spectrum in DMSO-d6, (E) XRD, (F) DSC and TGA of WIP.

Figure 3

Changes in reducing sugar contents of WIP. (A) Oral digestion, (B) gastric digestion, (C) intestinal digestion during In vitro digestion.

Figure 4

Viscosity and osmotic activity of WIP. (A) Viscosity, (B) particle size of WIP, CMP and INU.

Figure 5

Water and oil adsorption characteristics of WIP. (A) WSC, (B) WHC and OHC of WIP.

Figure 6

Density characteristics of WIP. (A) Bulk density, (B) Tapped density, (C) Hausner’s ratio and (D) compressibility index of WIP, CMP, and INU. ***p < 0.001 and ****p < 0.0001.

Figure 7

Effect of WIP, CMP and INU on (A) pH value, (B) reducing sugar content, and (C) ammonia content.*p < 0.05 and ***p < 0.001.

Figure 8

Morphological changes of WIP during in vitro fermentation. (A,B) SEM of WIP before fermentation, (C,D) SEM of WIP after fermentation.

Figure 9

Diversity and evenness analysis of gut microbial communities. (A) Simpson index, (B) Shannon index, and (C) ternary plot in WIP, CMP, and INU.

Figure 10

β-diversity analysis of gut microbial communities. (A) PCoA, (B) NMDS of WIP, CMP, and INU.

Figure 11

Contribution of species on gut microbial communities. (A) Simper analysis of WIP, (B) Heatmap analysis of WIP, CMP, and INU at the phylum level.

Figure 12

Effect of WIP on gut microbiota composition. (A) Phylum level, (B) Firmicutes/Bacteroidetes ratio, (C) family level, (D) Lachnospiraceae ratio, (E) genus level, and (F) Prevotella ratio. **p < 0.01, ***p < 0.001, and ****p < 0.0001.