CN117903332A - A kind of distiller's grains water-soluble arabinoxylan and its preparation method, pharmaceutical composition and application - Google Patents

Abstract

The present invention belongs to the field of medical technology, and discloses a distiller's grains water-soluble arabinoxylan and a preparation method, a pharmaceutical composition and an application thereof. The present invention uses distiller's grains as raw materials and extracts water-soluble arabinoxylan therefrom. The distiller's grains water-soluble arabinoxylan prepared by the present invention can significantly improve the symptoms of ulcerative colitis, and has the activity of inhibiting the secretion of inflammatory factors and improving the barrier function of the intestinal mucosa. At the same time, it provides a safe and effective drug for the treatment of ulcerative colitis. It can also be widely used in the preparation of drugs that inhibit the secretion of inflammatory factors by macrophages, drugs that enhance the barrier function of the intestinal tract, drugs that increase the level of intestinal short-chain fatty acids, and drugs that repair the imbalance of intestinal flora in ulcerative colitis. In addition, the distiller's grains in the present invention are by-products of liquor fermentation, and the raw material yield is high and the cost is low. The present invention can achieve the purpose of making full use of and increasing its added value.

Description

A kind of water-soluble arabinoxylan from distiller's grains and its preparation method, pharmaceutical composition and application

Technical Field

The invention belongs to the technical field of medicines, and in particular relates to a vinasse water-soluble arabinoxylan and a preparation method, a pharmaceutical composition and application thereof.

Background technique

Ulcerative colitis is a chronic, nonspecific inflammatory bowel disease that primarily affects the mucosa and submucosa of the colon. Although the etiology of ulcerative colitis is not fully understood, the main symptoms include diarrhea, bloody stools, abdominal pain, and persistent intestinal inflammation, which not only affect the patient's quality of life, but may also lead to severe systemic symptoms such as malnutrition, anemia, and weight loss as the disease progresses. In addition, patients with ulcerative colitis have a significantly increased risk of developing colon cancer compared to normal people.

Currently, the treatment of ulcerative colitis mainly includes the use of aminosalicylic acid drugs (5-ASA), corticosteroids, immunomodulatory drugs, biological agents and small molecule drugs. These drugs can relieve symptoms to a certain extent, but the recurrence rate is high after long-term use or discontinuation of the drug, and there is a risk of adverse reactions. Therefore, the development of new anti-colitis drugs and adjuvant therapies is an urgent problem that the current medical community needs to solve.

The production process of Chinese liquor produces a large amount of byproducts - distiller's grains, which contain a variety of biologically active ingredients, such as polysaccharides, oligosaccharides, proteins, fats, etc. After proper treatment, they are currently commonly used as organic fertilizers, animal feeds, yeast culture and biofuels. In recent years, researchers have begun to pay attention to polysaccharides in distiller's grains, especially water-soluble polysaccharides, and have conducted in-depth research on their structure and function.

However, there are relatively few studies on the extraction of water-soluble polysaccharides from liquor lees. The research on their structure and function is not in-depth enough, and there is a lack of research on their anti-ulcerative colitis mechanism, which is crucial for the high-value utilization of liquor lees, the treatment of ulcerative colitis, and the development of drugs to alleviate the disease and reduce the risk of complications.

Summary of the invention

The purpose of the present invention is to solve the deficiencies of the prior art and provide a vinasse water-soluble arabinoxylan and a preparation method, a pharmaceutical composition and application thereof, which specifically adopts the following technical scheme:

According to a first aspect of the present invention, there is provided a vinasse water-soluble arabinoxylan, the sugar chain structure of which is shown in Formula I:

Formula I;

In formula I, R is selected from any one of terminal xylose, terminal arabinose, and a short glucose or galactose chain consisting of rhamnose, galactose, glucose, arabinose, and xylose; and n is an integer of 20.

The distillers grains water-soluble arabinoxylan (DGPS-2B) prepared by the present invention is a novel arabinoxylan with a molecular weight of 37.3 kDa, wherein the ratio of arabinose to xylose is 0.66, and there are substituents at the C-3 position of the xylose residue and the C-2 or C-3 position of the arabinose residue. In addition, when the number of repeating units n is equal to 20, there may be a glucose and galactose chain.

According to a second aspect of the present invention, a method for preparing the above-mentioned vinasse water-soluble arabinoxylan is also provided, comprising the following steps:

(1) extracting the lees in boiling water three times, filtering and soaking in 5% sodium hydroxide solution to obtain an alkaline extract;

(2) dialyzing the alkaline extract obtained in step (1) with water for three days, centrifuging the dialyzate, adding anhydrous ethanol to precipitate overnight, centrifuging, and freeze-drying to obtain crude polysaccharide;

(3) re-dissolving the crude polysaccharide obtained in step (2) in water, removing the protein by Sevag method, and freeze-drying to obtain the crude polysaccharide from which the protein has been removed;

(4) The crude polysaccharide obtained in step (3) from which the protein has been removed is dissolved in water and eluted with a DEAE Sepharose FF column with water and a sodium chloride solution at a flow rate of 1.0 mL/min in sequence; the portion eluted with a 0.1 mol/L sodium chloride solution is further separated by a Sephacryl S-300 chromatography column and dialyzed to obtain lees water-soluble arabinoxylan.

The DGPS-2B arabinoxylan disclosed by the present invention has fewer preparation processes, low cost, no environmental pollution, is suitable for large-scale production, can realize high-value utilization of lees which are byproducts of liquor brewing, and the prepared arabinoxylan has outstanding effects on preventing and treating ulcerative colitis.

Preferably, the soaking conditions in step (1) are: temperature of 4°C and time of 12 h. Controlling the soaking conditions can prevent polysaccharide degradation and protect the biological activity of the polysaccharide.

Preferably, in step (2), the volume ratio of the dialysate to anhydrous ethanol is 1:4. Using excess anhydrous ethanol can increase the recovery rate of crude polysaccharides and precipitate soluble polysaccharides as much as possible.

Preferably, the concentration of the sodium chloride solution in step (4) is 0.1 mol/L, 0.2 mol/L and 0.3 mol/L. By utilizing a graded elution method, the polysaccharide can be fully eluted to improve the purity of the polysaccharide.

According to the third aspect of the present invention, a pharmaceutical composition is also provided, comprising the above-mentioned vinasse water-soluble arabinoxylan.

According to the fourth aspect of the present invention, there is also provided the use of the above-mentioned distiller's grains water-soluble arabinoxylan in the preparation of drugs for the treatment of ulcerative colitis, drugs for inhibiting the secretion of inflammatory factors by macrophages, drugs for improving intestinal barrier function, drugs for increasing the level of intestinal short-chain fatty acids, and drugs for repairing the imbalance of intestinal flora in ulcerative colitis.

The DGPS-2B prepared by the present invention can significantly change the composition of the intestinal microbial community of colitis model mice, increase the number of bacteria that produce short-chain fatty acids, and reduce the number of bacteria that degrade mucin. This change in the microbial flora increases the level of short-chain fatty acids in the intestines of colitis mice, inhibits the NF-κB signaling pathway, and then reduces the production of pro-inflammatory cytokines. These combined effects ultimately increase the level of synthesis and secretion of mucin 2 by intestinal epithelial cells, and are a new, safe and effective drug for the treatment of ulcerative colitis.

Preferably, the inflammatory factors are TNF-α, IL-1β and IL-6.

Preferably, the short chain fatty acids are butyrate, acetate and propionate.

Preferably, the intestinal flora is short-chain fatty acid producing flora and mucin degrading flora.

The beneficial effects of the present invention are as follows: the lees water-soluble arabinoxylan prepared by the present invention can significantly improve the symptoms of ulcerative colitis, and has the activity of inhibiting the secretion of inflammatory factors and improving the barrier function of the intestinal mucosa, and at the same time provides a new safe and effective drug for the treatment of ulcerative colitis, and can be widely used in the preparation of ulcerative colitis treatment drugs, drugs for inhibiting macrophage secretion of inflammatory factors, drugs for improving intestinal barrier function, drugs for increasing the level of intestinal short-chain fatty acids, and drugs for repairing the imbalance of intestinal flora in ulcerative colitis. In addition, the experimental materials involved in the present invention are derived from the by-products of liquor fermentation, with high raw material yield and low cost, and can achieve the purpose of making full use of the by-product of liquor brewing lees and improving its added value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a monosaccharide composition analysis diagram of DGPS-2B;

Figure 2 shows the NMR analysis of DGPS-2B; (A) anomeric carbon region of HSQC spectrum; (B) presaturated ¹ H NMR spectrum of DGPS-2B; (C) ¹ H NMR spectrum of DGPS-2B; (D) COSY spectrum; (E) non-anomeric carbon region of HSQC spectrum; (F) HMBC spectrum; (G) NOESY spectrum;

Figure 3 shows the activity of DGPS-2B in improving DSS-induced ulcerative colitis in mice; (A) the effect of DGPS-2B treatment on the weight change of mice after DSS induction; (B) the effect of DGPS-2B treatment on the colon length of mice after DSS induction; (C) the effect of DGPS-2B treatment on the spleen weight of mice after DSS induction; (D) the effect of DGPS-2B on the disease activity index score after DSS-induced ulcerative colitis; (E) the effect of DGPS-2B treatment on the DSS-induced proximal colon, middle colon and distal colon histopathological changes;

Figure 4 shows the molecular mechanism of DGPS-2B improving the inflammatory response and intestinal barrier damage caused by ulcerative colitis; (A) Western blotting was used to detect and quantify the expression levels of total IκBα and p65, phosphorylated IκBα and p65 in the colon of different treatment groups; (B) The levels of inflammatory cytokines IL-1β, IL-6 and TNF-α in serum; (C) AB&PAS staining was used to analyze the abundance of goblet cells and mucin levels in the colon of different experimental groups;

Figure 5 shows the effects of DGPS-2B on fecal short-chain fatty acid levels and intestinal flora; (A) the effect of DGPS-2B on fecal short-chain fatty acid butyrate, acetate, and propionate levels; (B) the regulatory effect of DGPS-2B on intestinal microbial flora at the phylum level after DSS-induced ulcerative colitis; (C) the regulatory effect of DGPS-2B on intestinal microbial flora at the genus level after DSS-induced ulcerative colitis.

Detailed ways

The following will be combined with the embodiments and drawings to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other without conflict.

Example 1

A distiller's grains water-soluble arabinoxylan comprises the following steps:

(1) The liquor lees were extracted in boiling water three times, each time for 4 hours, and the extract was filtered and discarded. The filtered residue was soaked in 5% sodium hydroxide solution at 4°C for 12 hours to obtain an alkaline extract.

(2) After filtering and concentrating the alkaline extract obtained in step 1, dialyze with tap water for three days, centrifuge the dialyzate at 8000 rpm for 10 minutes, and precipitate with four times the volume of anhydrous ethanol overnight. The precipitate obtained by centrifugation is freeze-dried to obtain crude polysaccharide.

(3) The crude polysaccharide is redissolved in deionized water and the protein is removed by the Sevag method. The resulting solution is freeze-dried again to obtain the crude polysaccharide from which the protein is removed.

(4) The crude polysaccharide after protein removal was dissolved in deionized water and eluted sequentially with deionized water, 0.1, 0.2 and 0.3 mol/L sodium chloride solutions at a flow rate of 1.0 mL/min using a DEAE Sepharose FF column (Φ5.0 cm × 50 cm). The eluted fractions were collected and the polysaccharide content was detected using the phenol-sulfuric acid method. The fraction eluted with 0.1 mol/L sodium chloride was further separated by a Sephacryl S-300 chromatography column (Φ2.6 cm × 100 cm). The chromatography column was equilibrated and eluted with 0.2 mol/L sodium chloride solution. The main fraction was collected and dialyzed to obtain a water-soluble polysaccharide named DGPS-2B.

Example 2

This example experimentally analyzes the monosaccharide composition and methylation of DGPS-2B.

As shown in Figure 1, the upper figure represents the mixed standard, and the lower figure represents the DGPS-2B sample. The sugar composition analysis results show that DGPS-2B is composed of xylose, arabinose, glucose, galactose and rhamnose, with a molar ratio of 55.5:36.6:3.7:3.0:1.2 (Figure 1). Monosaccharide analysis shows that DGPS-2B is mainly composed of arabinose and xylose, with a molar ratio of 0.66.

After DGPS-2B was completely methylated through multiple methylation reactions, it was hydrolyzed, reduced, and acetylated to generate partially methylated sugar alcohol acetates, which were then detected using GC-MS. According to the total ion chromatogram and each mass spectrometry fragment analysis, a total of 13 glycosidic bonds were detected in DGPS-2B (Table 1). Among them, xylose residues had the highest content, accounting for about 56.9% of DGPS-2B, and existed in the form of Xyl p -(1→, →4)-Xyl p -(1→ and →3,4)-Xyl p -(1→). Arabinose residues accounted for 32.7% of DGPS-2B, and existed in the form of Ara f -(1→, →2,5)-Ara f -(1→ and →2,3,5)-Ara f -(1→). Galactose residues (4.2%) in DGPS-2B had four different forms, including →6)-Gal p -(1→, →3)-Gal p -(1→, →2,6)-Gal p -(1→ and →3,6)-Gal p -(1→, and glucose residues (4.7%) were only connected in the form of →6)-Glc p -(1→ and →3,6)-Glc p -(1→. In addition, rhamnose residues were only connected through 1,4-glycosidic bonds.

Example 3

This example conducts an experimental analysis on the nuclear magnetic resonance of DGPS-2B.

To further analyze the sugar chain structure of DGPS-2B, we acquired the one-dimensional and two-dimensional NMR spectra of DGPS-2B. From the NMR spectrum, we can see that the three strong cross-linked anomeric signals at 4.39/101.6, 4.55/101.4 and 4.49/102.5 ppm in the HSQC spectrum (Figure 2A) are attributed to the xylose residue A (→4)-β-D-Xyl p -(1→), residue B (β-D-Xyl p -(1→) and residue C (→3,4)-D-Xyl p -(1→), respectively. The anomeric signals at 5.32/107.5, 5.21/108.2 and 5.14/108.7 ppm in the HSQC spectrum (Figure 2A) are attributed to the arabinose residue D (α-L-Ara f -(1→), residue E (→2,3,5)-α-L-Ara f -(1→) and residue F (→2,5)-α-L-Ara f -(1→), respectively.

The anomeric signal of residue G (→4)-α-L-Rha p -(1→) appears at 5.06/99.2 ppm. The glucose residues (→6)-β-D-Glc p -(1→) and (→3,6)-β-D-Glc p -(1→) are indicated as residues H and I, respectively. The four galactose residues are residue J (→3)-α-D-Gal p -(1→), residue K (→6)-α-D-Gal p -(1→), residue L (→3,6)-α-D-Gal p -(1→), and residue M (→2,6)-α-D-Gal p - (1→). -(1→). In the HSQC spectrum (Figure 2A), the chemical shifts of the anomeric protons and carbons of these six residues are 4.53/102.5, 4.60/102.5, 4.92/99.5, 5.01/101.7, 5.09/101.7, and 5.04/101.7 ppm, respectively. In addition, in the presaturated ¹ H NMR spectrum of DGPS-2B (Figure 2B), no signals of residues H and I were observed, while these two signals were observed in the ¹ H spectrum without presaturation (Figure 2C) and the anomeric carbon region of the HSQC spectrum (Figure 2A). This difference may be due to their lower concentrations.

In the HSQC spectrum (Figure 2A), the anomeric signal at 4.39/101.6 ppm was assigned to residue A (→4)-β-D-Xyl p -(1→). The COSY spectrum (Figure 2D) further showed related signals derived from the H-1 signal, including H-1/H-2 (4.39/3.37), H-2/H-3 (3.37/3.50), H-3/H-4 (3.50/3.83) and H-4/H-5 (3.83/3.65). Using the chemical shifts of H-2 to H-5, the corresponding chemical shifts of C-2 to C-5 of residue A were determined to be 3.37/75.9, 3.50/76.2, 3.83/77.2 and 3.30 (4.08)/62.8 ppm, respectively (Figure 2E). Similarly, the proton and carbon signals of residue B (β-D-Xyl p -(1→) and residue C (→3,4)-β-D-Xyl p -(1→) were also determined.

The anomeric signals at 5.32/107.5, 5.21/108.2, and 5.14/108.7 ppm in the HSQC spectrum (Figure 2A) were assigned to residue D (α-L-Ara f -(1→), residue E (→2,3,5)-α-L-Ara f -(1→), and residue F (→2,5)-α-L-Ara f, respectively. -(1→). Figure 2D (COSY spectrum) shows the cross peaks of H-1/H-5 (5.32/3.73), H-5/H-4 (3.73/4.01), H-4/H-3 (4.01/3.86), and H-3/H-2 (3.86/4.19) of residue D, and the chemical shifts of H-2 to H-5 were determined. Based on the signals at 4.26/84.6, 3.86/76.7, 4.01/84.0, 3.73 (3.60)/61.1 ppm in the HSQC spectrum, the corresponding chemical shifts of C-2 to C-5 of residue D were determined. For residue E, the cross peaks of H-2 to H-4 (4.26, 4.08, and 4.24 ppm). Based on the proton information, the signals from C2 to C4 were identified. The cross peaks at 3.86 (3.37)/69.0 ppm in the nonanomeric region of the HSQC spectrum were assigned to H-5 and C-5. Similarly, the nonanomeric protons and nonanomeric carbons of residue F were also identified.

Based on the cross-peak data in both HMBC (Fig. 2F) and NOESY (Fig. 2G) spectra, the correlation signals between H-1 of residue D and H-3 of residue E indicate the presence of a disaccharide unit L-Ara f -(1→2,3,5)-L-Ara f -(1→→4)-D-Xyl p -(1→2,3,5)-L-Ara f ... -(1→. Similarly, the connections between residues E and C, A and C, and D and A were also determined. Therefore, we infer that DGPS-2B is composed of an arabinoxylan backbone, and the substitution mainly occurs at the C-3 position of the xylose residue, and may also occur at the C-2 or/and C-3 position of the arabinose residue. Based on the theory of relatively ordered structures of polysaccharides, we further infer that galacto-oligosaccharides and gluco-oligosaccharides (indicated as R) exist in the side chains of DGPS-2B, and other side chains such as short galactans and glucans may also exist.

Example 4

This example experimentally analyzes the anti-ulcerative colitis activity of DGPS-2B.

Experimental methods: Healthy 8-week-old female mice were randomly divided into 4 groups: control group (Control), DSS-induced group (DSS), DSS-induced low concentration (10 mg/kg/day) DGPS-2B treatment group (DSS+DGPS-2B10), and DSS-induced high concentration (100 mg/kg/day) DGPS-2B treatment group (DSS+DGPS-2B100). The control group mice were given an equal volume of normal saline, and 2.5% DSS was added to the drinking water of the DSS-induced group and the DGPS-2B treatment group to induce ulcerative colitis. The DGPS-2B treatment group was given different doses of DGPS-2B by gavage once a day for two consecutive weeks. During the administration period, the diet, behavior and feces of the mice were observed. After two weeks of administration, the mice were killed, and blood, feces and colon tissue samples were collected to test the therapeutic effect of DGPS-2B on experimental colitis.

The results showed that DGPS-2B treatment could significantly improve the symptoms of ulcerative colitis. Starting from the fourth day after DSS induction, both low and high concentrations of DGPS-2B improved DSS-induced weight loss (Figure 3A), shortened colon length (Figure 3B), and spleen enlargement (Figure 3C), and significantly reduced the DAI score (Figure 3D). Colon pathological analysis found that both low and high doses of DGPS-2B effectively reduced DSS-induced mucosal damage and inflammatory response in the proximal, middle, and distal colons, and significantly reduced the loss of colonic epithelial structure and infiltration of inflammatory cells (Figure 3E).

Example 5

This example is the mechanism of action of DGPS-2B in improving DSS-induced ulcerative colitis inflammatory response and intestinal barrier loss.

Further detection revealed that compared with the DSS group, DGPS-2B could inhibit DSS-induced phosphorylation of IκBα and p65 proteins (Figure 4A), and reduce the levels of inflammatory factors TNF-α, IL-1β, and IL-6 in serum (Figure 4B), indicating that DGPS-2B may reduce the production of proinflammatory cytokines and alleviate inflammatory responses by inhibiting the NF-κB signaling pathway. In addition, compared with control mice, a decrease in mucus-secreting goblet cells and down-regulation of mucin 2 expression were observed in the colon of DSS-treated mice (Figure 4C). DGPS-2B treatment significantly increased the number of goblet cells and restored the expression of mucin 2, indicating that DGPS-2B can promote the repair of DSS-induced mucus barrier damage.

Example 6

This example shows the effect of DGPS-2B on short-chain fatty acids and microbial flora structure in the intestine.

The metabolism of microorganisms in the intestine produces short-chain fatty acids, mainly butyrate, propionate and acetate, which have been shown to improve colitis symptoms and promote intestinal health. In this patent, DGPS-2B treatment can restore the decrease in butyrate, acetate and propionate levels in the intestine of mice caused by DSS, thereby helping to improve the symptoms of ulcerative colitis (Figure 5A).

After DSS-induced ulcerative colitis, we investigated the effect of DGPS-2B on the composition of the intestinal microbiota in colitis. At the phylum level, the intestinal microbiota of mice in all treatment groups was mainly composed of Firmicutes, Bacteroidetes, Campylobacter, Proteobacteria, Verrucomicrobia, Desulfobacteria, and Actinobacteria. DSS treatment reduced the abundance of Firmicutes, Campylobacter, and Desulfobacteria, but increased the abundance of Bacteroidetes and Verrucomicrobia. DGPS-2B treatment increased the abundance of Firmicutes, Campylobacter, Proteobacteria, and Desulfobacteria, and reduced the abundance of Bacteroidetes, Verrucomicrobia, and Actinobacteria, indicating that it can repair the imbalance of the intestinal microbiota structure induced by DSS (Figure 5B). At the genus level, the top 15 genera identified in feces accounted for more than 80% of the total microbial flora, among which Muribaculaceae , Bacteroides, and Akkermansia were significantly increased, while DSS treatment downregulated the levels of Lachnospiraceae_NK4A136_group , Lactobacillus, Turicibacter , Helicobacter, Odoribacter , unclassified f_Lachnospiraceae , and unclassified f_Desulfovibrionaceae in the intestine of mice. Compared with DSS-treated mice, DGPS-2B treatment increased the abundance of Lachnospiraceae_NK4A136_group , Turicibacter , Helicobacter , Odoribacter , and unclassified f_Lachnospiraceae in the fecal intestinal microbiota of DSS mice, but decreased the relative abundance of unclassified f_Muribaculaceae , Bacteroides, and Akkermansia (Figure 5C). Therefore, DGPS-2B treatment can promote the restoration of the composition of the intestinal microbial flora of mice induced by DSS. In addition, a comparative analysis with existing literature found that DGPS-2B can be beneficial to the restoration of intestinal mucus barrier function in ulcerative colitis by reducing the expansion of mucin-degrading bacterial genera, including Bacteroides, Akkermansia, Murribakula, and Alternaria. In addition, DGPS-2B treatment increased the abundance of potential short-chain fatty acid-producing bacterial genera in the colon in a dose-dependent manner, such as Lachnospiraceae_NK4A136_group , Odoribacter , Blautia , Lachnoclostridium , Butyricicoccus , and Turicibacter , thereby helping to increase the content of butyrate, propionate, and acetate in the colon.

In summary, DGPS-2B can significantly change the composition of the intestinal microbial community in colitis model mice, increase the number of bacteria that produce short-chain fatty acids, and reduce the number of bacteria that degrade mucin. This change in the microbial flora increased the level of short-chain fatty acids in the intestine of colitis mice, inhibited the NF-κB signaling pathway, and then reduced the production of proinflammatory cytokines. These combined effects ultimately increased the level of intestinal epithelial cell synthesis and secretion of mucin 2, thereby achieving the purpose of treating ulcerative colitis.

Although the description of the present invention has been quite detailed and specifically described with respect to several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as providing a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively covering the intended scope of the present invention. In addition, the above description of the present invention is based on the embodiments foreseeable by the inventors, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that have not yet been foreseen may still represent equivalent changes to the present invention.

Claims (10)

1. A water-soluble arabinoxylan from distiller's grains, characterized in that its sugar chain structure is as shown in Formula I: Formula I; In formula I, R is selected from any one of terminal xylose, terminal arabinose, and a short glucose or galactose chain consisting of rhamnose, galactose, glucose, arabinose, and xylose; and n is an integer of 20. 2. A method for preparing water-soluble arabinoxylan from distiller's grains, characterized in that it comprises the following steps: (1) extracting the lees in boiling water three times, filtering and soaking in 5% sodium hydroxide solution to obtain an alkaline extract; (2) dialyzing the alkaline extract obtained in step (1) with water for three days, centrifuging the dialyzate, adding anhydrous ethanol to precipitate overnight, centrifuging, and freeze-drying to obtain crude polysaccharide; (3) re-dissolving the crude polysaccharide obtained in step (2) in water, removing the protein by Sevag method, and freeze-drying to obtain the crude polysaccharide from which the protein has been removed; (4) The crude polysaccharide obtained in step (3) from which the protein has been removed is dissolved in water and eluted with a DEAE Sepharose FF column with water and a sodium chloride solution at a flow rate of 1.0 mL/min in sequence; the portion eluted with a 0.1 mol/L sodium chloride solution is further separated by a Sephacryl S-300 chromatography column and dialyzed to obtain lees water-soluble arabinoxylan. 3. The preparation method according to claim 2, characterized in that the soaking conditions in step (1) are: temperature of 4°C and time of 12 h. 4. The preparation method according to claim 2, characterized in that the volume ratio of the dialysate to the anhydrous ethanol in step (2) is 1:4. 5. The preparation method according to claim 2, characterized in that the concentration of the sodium chloride solution in step (4) is 0.1 mol/L, 0.2 mol/L and 0.3 mol/L. 6. A pharmaceutical composition, characterized in that it comprises the vinasse water-soluble arabinoxylan according to any one of claims 1 to 5. 7. Use of the water-soluble arabinoxylan from distiller's grains according to any one of claims 1 to 6 in the preparation of drugs for treating ulcerative colitis, drugs for inhibiting macrophage secretion of inflammatory factors, drugs for improving intestinal barrier function, drugs for increasing intestinal short-chain fatty acid levels, and drugs for repairing intestinal flora imbalance in ulcerative colitis. 8. The use according to claim 7, characterized in that the inflammatory factors are TNF-α, IL-1β and IL-6. 9. The use according to claim 7, characterized in that the short-chain fatty acids are butyrate, acetate and propionate. 10. The use according to claim 7, characterized in that the intestinal flora is a short-chain fatty acid producing flora and a mucin degrading flora.