American ginseng stem and leaf polysaccharide XYSJY2-2 as well as preparation method and application thereof

Abstract

The invention discloses American ginseng stem and leaf polysaccharide XYSJY2-2 as well as a preparation method and application of the American ginseng stem and leaf polysaccharide XYSJY2-2. The American ginseng stem and leaf polysaccharide XYSJY2-2 is prepared from 19.32% of galactose, 21.02% of galacturonic acid, 22.02% of rhamnose, 18.40% of arabinose, 9.3% of glucuronic acid, 3.45% of fucose, 2.45% of glucose, 2.28% of mannose and 1.76% of xylose. The pectin polysaccharide is a pectin polysaccharide with a rhamnogalacturonic acid core structure. The American ginseng stem and leaf polysaccharide XYSJY2-2 is obtained by taking American ginseng stem and leaf as a raw material, performing water extraction, concentration, dialysis, alcohol precipitation and protein removal to obtain crude American ginseng stem and leaf polysaccharide, and further performing column chromatography, concentration, dialysis and starch removal, the extraction method is simple and effective, and the American ginseng stem and leaf polysaccharide XYSJY2-2 has the effects of inhibiting myocardial cell hypertrophy and protecting the heart, and can be used for preparing the American ginseng stem and leaf polysaccharide XYSJY2-2. The compound is expected to be developed into carbohydrate drugs and functional products for resisting myocardial diseases.

Description

Technical Field

[0001] The invention belongs to the technical field of polysaccharide extraction, and specifically relates to a ginseng stem and leaf polysaccharide XYSJY2-2 and a preparation method and use thereof, namely a method for extracting the ginseng stem and leaf polysaccharide XYSJY2-2 from ginseng stems and leaves, the ginseng stem and leaf polysaccharide XYSJY2-2 extracted by the method, and use of the ginseng stem and leaf polysaccharide XYSJY2-2 in preparing an anti-myocardial disease drug. Background Art

[0002] Cardiovascular disease has become an important public health issue, posing a threat to human life and health worldwide. According to the National Health and Nutrition Examination Survey (NHANES) data from 2017 to March 2020, the overall incidence of cardiovascular disease in people aged 20 years and above has increased significantly by 48.6%. Ischemic heart disease causes 9 million deaths worldwide each year, accounting for 1.7% of all global disease-related deaths. In addition, it is worth noting that this prevalence increases with age. In fact, heart and vascular diseases cause more than 17.3 million deaths each year. Cardiac hypertrophy is considered an independent risk factor for cardiovascular morbidity and mortality. Cardiac hypertrophy is a compensatory process in which the heart increases cardiac output in response to a variety of pathological conditions such as hypertension, myocardial ischemia, hypoxia, and pulmonary hypertension. If untreated, persistent cardiac hypertrophy will lead to an increase in the volume of myocardial cells, accompanied by mechanical and metabolic changes, and may eventually develop into heart failure. Therefore, early intervention to effectively delay or reverse cardiac hypertrophy is of great clinical significance in preventing and controlling the progression of heart failure. The complex pathophysiology of cardiac hypertrophy has led to the current lack of effective treatments to deal with this pathological state.

[0003] Traditional Chinese medicine polysaccharides extracted by modern scientific methods are called traditional Chinese medicine polysaccharides. According to their biological sources, they can be divided into fungal, polyplant, animal and bacterial polysaccharides. Many studies have consistently shown that traditional Chinese medicine polysaccharides have a variety of pharmacological activities, including anti-inflammatory, antioxidant, anti-fibrotic, anti-cancer, inhibition of cardiac hypertrophy and immunomodulatory functions. Due to their sustainability, natural sources, pharmacological properties, inherent safety and low toxicity, traditional Chinese medicine polysaccharides have attracted extensive research attention. Some bioactive polysaccharides from traditional Chinese medicine have been applied in the fields of biochemistry and medicine. Among them, astragalus polysaccharides, ginseng polysaccharides, lentinan polysaccharides, fucoidan, hericium erinaceus polysaccharides and tuckahoe polysaccharides have been specially developed as health products.

[0004] The root of Panax quinquefolius is a perennial herb from the Araliaceae family, commonly known as American ginseng. American ginseng polysaccharides have the properties of immune enhancement, anti-inflammatory, anti-tumor, anti-radiation and intestinal flora regulation, showing good research and development prospects. American ginseng polysaccharides are not only found in its roots and rhizomes, but also in its fruits, stems and leaves. Studies have shown that these polysaccharides can relieve liver damage, regulate the immune system, and reduce intestinal mucosal damage. At present, studies have shown that American ginseng root polysaccharides have the ability to regulate mitochondrial function and protect myocardial cells, but their exact pharmacological mechanism has not yet been fully understood. Moreover, the research on American ginseng polysaccharides mainly focuses on its roots, and there are few reports on the activity of American ginseng stem and leaf polysaccharides. For example, patent document CN200610083851.2 discloses reports on the treatment of human and animal viral influenza and the improvement of animal immunity by crude polysaccharides from American ginseng stems and leaves. Summary of the invention

[0005] One of the purposes of the present invention is to provide a polysaccharide XYSJY2-2 from the stems and leaves of American ginseng. A pectin polysaccharide with a novel structure is extracted and purified from the stems and leaves of American ginseng. It is found that the polysaccharide has a significant inhibitory effect on cardiac hypertrophy and shows good anti-myocardial hypertrophy activity. Pharmacological experiments show that the polysaccharide can significantly inhibit Ang II-induced cardiomyocyte enlargement at the cellular level and significantly inhibit the expression of hypertrophy markers Nppa and Nppb. In vivo and in vitro experiments show that the polysaccharide can effectively prevent the progression of cardiac hypertrophy and remodeling, confirming that the polysaccharide XYSJY2-2 from the stems and leaves of American ginseng has a good anti-myocardial hypertrophy effect and is expected to become a potential polysaccharide drug and functional product for preventing and treating myocardial diseases.

[0006] One of the purposes of the present invention is to provide a method for preparing the American ginseng stem and leaf polysaccharide XYSJY2-2.

[0007] One of the purposes of the present invention is to provide the use of the American ginseng stem and leaf polysaccharide XYSJY2-2 in the preparation of a drug for preventing or treating myocardial disease.

[0008] To achieve the above object, the present invention adopts the following technical solution:

[0009] The invention provides a American ginseng stem and leaf polysaccharide XYSJY2-2, which consists of 19.32% of galactose, 21.02% of galacturonic acid, 22.02% of rhamnose, 18.40% of arabinose, 9.3% of glucuronic acid, 3.45% of fucose, 2.45% of glucose, 2.28% of mannose and 1.76% of xylose, has a weight average molecular weight of 10-500 kDa, and a relative molecular mass of 5110 Da.

[0010] Preferably, the American ginseng stem and leaf polysaccharide XYSJY2-2 has a β-D-type pyranose ring.

[0011] The present invention also provides a method for preparing the American ginseng stem and leaf polysaccharide XYSJY2-2, which specifically comprises the following steps:

[0012] (a) Polysaccharide extraction: The dried American ginseng stem and leaf powder is subjected to ethanol defatting, water extraction, and filtration. The resulting filtrate is concentrated, dialyzed, re-concentrated, alcohol precipitated, centrifuged, vacuum dried, and then freeze-dried after protein removal to obtain water-extracted American ginseng stem and leaf crude polysaccharides;

[0013] (b) Polysaccharide purification: The water-extracted crude polysaccharide from American ginseng stems and leaves was subjected to graded purification using a DEAE cellulose anion column, eluted with distilled water, 0.1 mol / L, 0.2 mol / L and 0.3 mol / L NaCl solutions in sequence, and detected with sulfuric acid-phenol. The fractions eluted with 0.2 mol / L NaCl solution were collected, concentrated, dialyzed and freeze-dried to obtain purified American ginseng stem and leaf polysaccharide XYSJY2;

[0014] (c) Secondary purification of polysaccharide: The purified American ginseng stem and leaf polysaccharide XYSJY2 was dissolved in deionized water and centrifuged. The supernatant was separated by Sephadex S-100 gel column. 0.2 mol / L NaCl solution was used for elution. The polysaccharide-containing components were collected and concentrated, dialyzed with deionized water, and freeze-dried to obtain a single homogeneous American ginseng stem and leaf polysaccharide XYSJY2-2.

[0015] Preferably, the specific process of polysaccharide extraction in step (a) comprises: first soaking the dried American ginseng stem and leaf powder in 95% ethanol for 1 week, then air-drying, adding 20 times the weight of deionized water, extracting at 100°C, filtering, extracting the residue again with deionized water, repeating the extraction 3 times, each time for 3 hours, concentrating the combined supernatant, treating with 15% trichloroacetic acid at 4°C for 3 hours to remove protein, centrifuging, concentrating, dialyzing, concentrating again, adding 95% ethanol 3 times the volume of the concentrate, centrifuging to obtain a precipitate, freeze-drying, and obtaining water-extracted American ginseng stem and leaf crude polysaccharides; wherein the dialysis bag has a molecular weight cutoff of 3500Da.

[0016] Preferably, the specific process of polysaccharide purification in step (b) comprises: taking the water-extracted American ginseng stem and leaf crude polysaccharide, adding 10 times the weight of water to dissolve, centrifuging, separating the supernatant through a DEAE cellulose anion column, eluting with distilled water, 0.1 mol / L, 0.2 mol / L, and 0.3 mol / L NaCl solution in sequence, detecting with sulfuric acid-phenol, collecting and merging the 0.2 mol / L NaCl solution eluate, concentrating, dialyzing, and freeze-drying to obtain the American ginseng stem and leaf polysaccharide XYSJY2.

[0017] Preferably, the specific process of the secondary purification of the polysaccharide in step (b) includes: dissolving the American ginseng stem and leaf polysaccharide XYSJY2 in deionized water with a mass volume ratio of 40:1 (w / v: mg / mL), centrifuging at 8000rpm for 15min, taking all the supernatant for loading, and separating through a Sephadex S-100 gel column; eluting with a 0.2mol / L NaCl solution, detecting the polysaccharide content by a phenol-sulfuric acid method, with the mobile phase volume as the horizontal axis and the absorbance as the vertical axis, drawing an elution curve, collecting the components containing the polysaccharide and concentrating them, dialyzing them with a 3500Da dialysis bag with deionized water for 3 days, and freeze-drying to obtain the American ginseng stem and leaf polysaccharide XYSJY2-2.

[0018] The present invention also provides a pharmaceutical composition, which comprises a therapeutically effective amount of the American ginseng stem and leaf polysaccharide XYSJY2-2 as an active ingredient.

[0019] Preferably, the pharmaceutical composition further comprises a pharmaceutically acceptable excipient selected from a carrier, an excipient, an adjuvant and / or a diluent.

[0020] The present invention also provides use of the American ginseng stem and leaf polysaccharide XYSJY2-2 or the pharmaceutical composition in preparing a drug for preventing or treating myocardial diseases.

[0021] Preferably, the drug uses the American ginseng stem and leaf polysaccharide XYSJY2-2 as the sole active ingredient, or is administered in combination with other pharmaceutically acceptable therapeutic agents.

[0022] The present invention also provides the use of the American ginseng stem and leaf polysaccharide XYSJY2-2 or the pharmaceutical composition in preparing a polysaccharide drug or functional product for treating myocardial hypertrophy.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention develops a simple and effective polysaccharide extraction and purification method, and obtains a ginseng stem and leaf polysaccharide XYSJY2-2 using ginseng stems and leaves as raw materials. Experimental verification shows that the ginseng stem and leaf polysaccharide XYSJY2-2 can significantly inhibit the enlargement of myocardial cells induced by Ang II at the cellular level, and significantly inhibit the expression of hypertrophy markers Nppa and Nppb; in vivo and in vitro experimental results also show that the polysaccharide XYSJY2-2 can effectively prevent cardiac hypertrophy and remodeling progression, has a good anti-myocardial hypertrophy effect, and is expected to become a potential polysaccharide drug and functional product for the treatment of myocardial diseases. At the same time, it is helpful to the high-value utilization of ginseng by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1This is a schematic diagram of the preparation process of American ginseng stem and leaf polysaccharide XYSJY2-2 in Example 1.

[0026] Figure 2 IR, monosaccharide and molecular weight spectra of American ginseng stem and leaf polysaccharide XYSJY2-2 in Example 1.

[0027] Figure 3 The results of the experiment in which American ginseng stem and leaf polysaccharide XYSJY2-2 protected cardiomyocytes from Ang II-induced hypertrophy in the example; NRCMs were stimulated with angiotensin II (1 μM), and then the cells were treated with or without XYSJY2-2 (25 and 100 μg / mL) for 48 h; A: Relative mRNA levels of Nppa and Nppb were detected by qPCR, n=6; B: Representative images of NRCM immunofluorescence staining, NRCM stained with F-actin (green) and nuclei stained with DAPI (blue), scale bar = 20 μm; C: Statistical results of NRCM cross-sectional area analyzed by Image J, n=6, all data are expressed as SD±mean, and statistical analysis was performed using one-way ANOVA test.

[0028] Figure 4 The experimental results of American ginseng stem and leaf polysaccharide XYSJY2-2 in the example alleviated TAC-induced mouse cardiac hypertrophy and remodeling; XYSJY2-2 (8 mg / kg / day) was given to mice 28 days after TAC surgery; A: 18srRNA was used to quantify Nppa and Nppb mRNA expression, n = 6; B: Representative cardiac vertical-hematoxylin-eosin (HE) stained sections showed the size of cardiomyocytes, scale bar = 20 μm, n = 6, Masson staining showed myocardial interstitial collagen and statistical results of myocardium; C: Bar graph results of analysis of myocardial cell cross-sectional area and left ventricular collagen area, n = 6, all data are expressed as SD ± mean, and statistical analysis was performed using one-way analysis of variance. DETAILED DESCRIPTION

[0029] The technical scheme of the present invention is further described below by way of examples. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] Reference Figure 1 The American ginseng stem and leaf polysaccharide XYSJY2-2 was prepared as follows:

[0032] a. Polysaccharide extraction:

[0033] Degrease the dried American ginseng stems and leaves with 95% ethanol for one week (ethanol is replaced every 3 days), and then dry naturally at room temperature. Extract 1000g of the dried American ginseng stems and leaves with 20 liters of boiling water (deionized water) 3 times, each time for 3 hours. Detect with sulfuric acid-phenol until there is no obvious reaction, filter, combine the extracts each time, heat and concentrate, dialyze with a dialysis bag with a molecular weight cutoff of 3500Da, and then concentrate to 2L, then add 3 times the volume of 6 liters of 95% ethanol under stirring, and let it stand overnight. Pour off the supernatant, centrifuge, wash the resulting precipitate with 3 times the volume of anhydrous ethanol, centrifuge, and vacuum dry the precipitate to obtain 30g of crude polysaccharide from American ginseng stems and leaves.

[0034] b. Polysaccharide purification:

[0035] Take 10 g of the above-mentioned crude polysaccharide from the stems and leaves of American ginseng, dissolve it in 100 mL of water, centrifuge to remove insoluble matter, and perform preliminary fractionation and purification of the supernatant through a Cl-type DEAE-cellulose anion column, eluted with distilled water, 0.1 mol / L, 0.2 mol / L and 0.3 mol / L NaCl solution in sequence, and detect with sulfuric acid-phenol. Collect and combine the 0.3 mol / L NaCl eluate, concentrate, dialyze, and freeze-dry to obtain 3.9 g of American ginseng stem and leaf polysaccharide XYSJY2.

[0036] Take 200 mg of American ginseng stem and leaf polysaccharide XYSJY2 treated with DEAE cellulose ion exchange column, dissolve in 5 mL of deionized water, centrifuge at 8000 rpm for 15 min, take all the supernatant for loading, use 0.2 mol / L NaCl solution for elution, use phenol-sulfuric acid method to detect polysaccharide content, use mobile phase volume as horizontal coordinate, vertical coordinate as absorbance, and draw elution curve. Collect the components containing polysaccharides and concentrate them, dialyze with 3500Da dialysis bag deionized water for 3 days, and finally freeze-dry to obtain 65.2 mg of single homogeneous polysaccharide component XYSJY2-2.

[0037] The structure of the prepared polysaccharide component XYSJY2-2 was identified and analyzed:

[0038] The molecular weight was determined by high performance gel permeation chromatography (HPGPC), which used Ultrahydrogel TM 2000 (25 cm × 0.75 cm, Waters, USA) and Ultrahydrogel TM 500 (25 cm × 0.75 cm, Waters, USA) columns in series, and used T-series standard dextran (Dextran) with different molecular weights to make a standard curve. The analysis by high performance gel permeation chromatography showed that the weight average molecular weight of polysaccharide XYSJY2-2 was 10 to 500 kDa, and the relative molecular weight was 5110 Da.

[0039] The monosaccharide composition was analyzed by PMP-pre-column derivatization high performance liquid chromatography, i.e., the polysaccharide was completely hydrolyzed, PMP-derivatized, extracted with chloroform, and the upper aqueous phase was sent to HPLC for analysis. The HPLC was determined using an Agilent 1260Seri high performance liquid chromatography system (Agilent, USA), a TSKgel GMPWXL column (7.5×300mm), a TSKgel guard column (6.0×40mm, 12μm, purchased from TOSOH, Japan), and a BDS HYPESILC18 column (250×4.60mm, 6μm, purchased from Thermo). The results of monosaccharide composition analysis showed that the American ginseng stem and leaf polysaccharide XYSJY2-2 contained 19.32% galactose, 21.02% galacturonic acid, 22.02% rhamnose, 18.40% arabinose, 9.3% glucuronic acid, 3.45% fucose, 2.45% glucose, 2.28% mannose and 1.76% xylose, among which Rha (22.02%) and Gal A (21.02%) had higher contents, with the ratio close to 1:1, and Gal (19.32%) and Ara (18.40%) had higher contents. The proportions of other monosaccharides were all lower than 10%, indicating that the American ginseng stem and leaf polysaccharide XYSJY2-2 was a pectin polysaccharide with a rhamnogalacturonic acid core structure.

[0040] The infrared analysis of the polysaccharide XYSJY2-2 from the stems and leaves of American ginseng was performed using a Perkin-Elmer 599B infrared spectrophotometer (Perkin-Elmer, USA). Figure 2 As shown, 3299cm -1 The prominent broadband at 2922 cm is attributed to the OH stretching vibration, while -1 The weak band at 1600 cm-1 is related to the CH stretching vibration of methylene and methyl groups. -1 The IR absorption peak at 1026 cm is attributed to the stretching vibration of C=O. -1 The strong peak at 916 cm-1 is attributed to the CO and CC stretching vibrations of the pyranose ring. -1 The absorption peak at indicates the presence of a β-D-pyranose ring.

[0041] Example 2: Activity of American ginseng stem and leaf polysaccharide XYSJY2-2 in inhibiting myocardial hypertrophy

[0042] Immunofluorescence staining: Cardiomyocytes were washed with PBS and fixed with 4% paraformaldehyde according to standard procedures. Cardiomyocytes were permeabilized with 0.1% Triton X-100 and blocked with 5% BSA in PBS for 1 hour at room temperature. Cardiomyocytes were incubated with FITC-phalloidin (Yeasen Biotech, catalog number 40735ES751:200) at 37°C for 1 hour, and the nuclei were stained with 4',6'-diamidino-2-phenylindole (DAPI, Beyotime, catalog number C1006). The cross-sectional area of ​​cardiomyocytes was measured using a confocal microscope (Zeiss LS800) using ImageJ software.

[0043] Real-time quantitative PCR: Total RNA was extracted from tissue or cardiomyocyte samples using Trizol reagent (Vazyme, catalog number R701-01). Total RNA was reverse transcribed into complementary DNA (cDNA) using III.1st Strand cDNA Synthesis SuperMix (Yeasen, catalog number 11141ES60) for qPCR. The primer sequences used are shown in Table 1.

[0044] Table 1

[0045] Gene Species Forward Reverse Nppa Rat 5'-CCCTCCGATAGATCTGCCCT-3' 5'-GGAAGCTGTTGCAGCCTAGT-3' Nppb Rat 5'-CTGCCCCAGATGATTCTGCT-3' 5'-TCCAGCAGCTTCTGCATCG-3' 18S Rat 5'-CGGCTACCACTCCAAGGAA-3' 5'-GCTGGAATTACCGCGGCT-3' Nppa Mouse 5'-TGTACAGTGCGGTGTCCAAC-3' 5'-CGAAGCAGCTGGATCTTCGT-3' Nppb Mouse 5'-TTGAAGGACCAAGGCCTCAC-3' 5'-CGTTACAGCCCAAACGACTG-3' 18S Mouse 5'-CGGCTACCACATCCAAGGAA-3' 5'-GCTGGAATTACCGCGGCT-3'

[0046] use Real-time polymerase chain reaction was performed using SYBR Green premix (Yeasen, catalog number 11202ES08). The expression of the targeted mRNA was normalized to 18s and measured by 2 -ΔΔCt Method calculation.

[0047] To investigate whether XYSJY2-2 has a cardioprotective effect on myocardial injury, NRCMs were isolated and angiotensin II (Ang II)-induced cardiomyocyte hypertrophy model was established. Immunofluorescence results showed that 25 μg / mL and 100 μg / mL XYSJY2-2 significantly inhibited Ang II-induced cardiomyocyte hypertrophy ( Figure 2 A). RT-qPCR results examining the expression of hypertrophic markers showed that XYSJY2-2 significantly inhibited the expression of Nppa and Nppb in response to Ang II stimulation ( Figure 2 B, C).

[0048] Example 3: American ginseng stem and leaf polysaccharide XYSJY2-2 inhibits cardiac hypertrophy in mice

[0049] Cardiac hypertrophy mouse model: Cardiac hypertrophy mouse model was established by pressure overload induced by transverse aortic constriction (TAC). Male mice were anesthetized by intraperitoneal injection of sodium pentobarbital (30 mg / kg), and the chest cavity of each mouse was opened to expose the aorta, and the aorta was narrowed using a 27G needle and 6-0 silk suture, which was then removed and the left chest was closed. Sham-operated mice underwent similar surgery without ligation, and the mice were taken after 28 days of feeding.

[0050] Histological analysis: The cells were fixed with 4% paraformaldehyde (Biosharp, catalog number BL539A), embedded in paraffin and cut into 4 μm thick cross sections. Myocardial fibrosis sections were stained with Masson's trichrome. The cross-sectional area of ​​myocytes was determined in the hematoxylin and eosin (HE) staining of the left ventricle. The cross-sectional area of ​​myocytes was measured using Image J software and scanned on a slice scanner (Hamamatsu, Nano Zoomer 2.0-RS).

[0051] To investigate the effect of XYSJY2-2 on cardiac hypertrophy in vivo, mice were given XYSJY2-2 (8 mg / kg) daily by oral gavage after transverse aortic constriction (TAC) surgery. The results showed that the mRNA expression levels of Nppa and Nppb were significantly increased in TAC mice and reversed by XYSJY2-2 treatment ( Figure 3 A); Hematoxylin-eosin (HE) staining showed that the cardiac cross-sectional area in the TAC group was increased compared with that in the sham group, and XYSJY2-2 significantly prevented this increase ( Figure 3 B and 3C); Masson staining to measure myocardial fibrosis in sections showed that XYSJY2-2 rescued TAC-induced collage deposition and cardiac fibrosis ( Figure 3 B and 3C).

[0052] In summary, the present invention extracts and purifies a novel American ginseng stem and leaf polysaccharide XYSJY2-2 from American ginseng stems and leaves, and it is found that the polysaccharide has a significant inhibitory effect on cardiac hypertrophy, shows good anti-myocardial hypertrophy activity, can effectively prevent the progression of cardiac hypertrophy and remodeling, and is helpful to develop potential polysaccharide drugs and functional products with few side effects and effective treatment of cardiovascular diseases.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the scope of the technical solution of the present invention.

Claims

1. A polysaccharide from American ginseng stems and leaves XYSJY2-2, characterized in that: The American ginseng stem and leaf polysaccharide XYSJY2-2 is composed of 19.32% galactose, 21.02% galacturonic acid, 22.02% rhamnose, 18.40% arabinose, 9.3% glucuronic acid, 3.45% fucose, 2.45% glucose, 2.28% mannose and 1.76% xylose, with a weight average molecular weight of 10 to 500 kDa and a relative molecular mass of 5110 Da.

2. The American ginseng stem and leaf polysaccharide XYSJY2-2 according to claim 1, characterized in that The American ginseng stem and leaf polysaccharide XYSJY2-2 has a β-D-type pyranose ring.

3. The method for preparing the American ginseng stem and leaf polysaccharide XYSJY2-2 according to claim 1 or 2, characterized in that: The following steps are involved: (a) Polysaccharide extraction: The dried American ginseng stem and leaf powder is subjected to ethanol defatting, water extraction, and filtration. The resulting filtrate is concentrated, dialyzed, re-concentrated, alcohol precipitated, centrifuged, vacuum dried, and then freeze-dried after protein removal to obtain water-extracted American ginseng stem and leaf crude polysaccharides; (b) Polysaccharide purification: The water-extracted crude polysaccharide from American ginseng stems and leaves was subjected to graded purification using a DEAE cellulose anion column, eluted with distilled water, 0.1 mol / L, 0.2 mol / L and 0.3 mol / L NaCl solutions in sequence, and detected with sulfuric acid-phenol. The fraction eluted with 0.2 mol / L NaCl solution was collected, concentrated, dialyzed and freeze-dried to obtain purified American ginseng stem and leaf polysaccharide XYSJY2; (c) Secondary purification of polysaccharide: The purified American ginseng stem and leaf polysaccharide XYSJY2 was dissolved in deionized water and centrifuged. The supernatant was separated by Sephadex S-100 gel column. 0.2 mol / L NaCl solution was used for elution. The polysaccharide-containing components were collected and concentrated, dialyzed with deionized water, and freeze-dried to obtain a single homogeneous American ginseng stem and leaf polysaccharide XYSJY2-2.

4. The method for preparing the American ginseng stem and leaf polysaccharide XYSJY2-2 according to claim 3, characterized in that: In step (a), the polysaccharide extraction process comprises: first soaking the dried American ginseng stem and leaf powder in 95% ethanol for 1 week, then air-drying, adding 20 times the weight of deionized water, extracting at 100°C, filtering, extracting the residue again with deionized water, repeating the extraction for 3 times, each time for 3 hours, concentrating the combined supernatant, treating with 15% trichloroacetic acid at 4°C for 3 hours to remove protein, centrifuging, concentrating, dialyzing, concentrating again, adding 95% ethanol 3 times the volume of the concentrate, centrifuging to obtain a precipitate, freeze-drying, and obtaining water-extracted American ginseng stem and leaf crude polysaccharides; wherein the dialysis bag has a molecular weight cutoff of 3500Da.

5. The method for preparing the American ginseng stem and leaf polysaccharide XYSJY2-2 according to claim 3, characterized in that: In step (b), the polysaccharide purification process includes: taking the water-extracted American ginseng stem and leaf crude polysaccharide, adding 10 times the weight of water to dissolve, centrifuging, separating the supernatant through a DEAE cellulose anion column, eluting with distilled water, 0.1mol / L, 0.2mol / L, and 0.3mol / L NaCl solution in sequence, detecting with sulfuric acid-phenol, collecting and merging the 0.2mol / L NaCl solution eluate, concentrating, dialyzing, and freeze-drying to obtain the American ginseng stem and leaf polysaccharide XYSJY2.

6. The method for preparing the American ginseng stem and leaf polysaccharide XYSJY2-2 according to claim 3, characterized in that: In step (c), the process of secondary purification of the polysaccharide includes: dissolving the American ginseng stem and leaf polysaccharide XYSJY2 in deionized water with a mass concentration of 40 mg / mL, centrifuging at 8000 rpm for 15 min, taking all the supernatant for loading, and separating through a Sephadex S-100 gel column; eluting with a 0.2 mol / L NaCl solution, detecting the polysaccharide content by a phenol-sulfuric acid method, with the mobile phase volume as the horizontal coordinate and the vertical coordinate as the absorbance, drawing an elution curve, collecting the components containing the polysaccharide for concentration, dialyzing with a 3500Da dialysis bag with deionized water for 3 days, and freeze-drying to obtain the American ginseng stem and leaf polysaccharide XYSJY2-2.

7. A pharmaceutical composition, characterized in that It contains a therapeutically effective amount of the American ginseng stem and leaf polysaccharide XYSJY2-2 as claimed in claim 1 or 2 as an active ingredient, and also includes pharmaceutically acceptable excipients selected from carriers, excipients, adjuvants and / or diluents.

8. Use of the American ginseng stem and leaf polysaccharide XYSJY2-2 according to claim 1 or 2, or the pharmaceutical composition according to claim 7, in the preparation of a drug for preventing or treating myocardial disease.

9. The use according to claim 8, characterized in that The drug uses the American ginseng stem and leaf polysaccharide XYSJY2-2 as the sole active ingredient, or is administered in combination with other pharmaceutically acceptable therapeutic agents.

10. Use of the American ginseng stem and leaf polysaccharide XYSJY2-2 according to claim 1 or 2, or the pharmaceutical composition according to claim 7, in the preparation of polysaccharide drugs or functional products for treating myocardial hypertrophy.

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