A method for extracting astragalus polysaccharide

Abstract

This application relates to the technical field of astragalus polysaccharides, and specifically relates to a method for extracting astragalus polysaccharides. A method for extracting astragalus polysaccharides includes the following steps: primary water extraction, secondary water extraction, vacuum concentration, primary alcohol precipitation, secondary alcohol precipitation, and purification. Among them, in the primary water extraction: soak astragalus with a weak alkaline solution, then heat to boiling and carry out extraction, and filter to separate the primary precipitate and the primary extract. By using a weak alkaline solution in the primary water extraction step, this application destroys cell walls, increases the solubility of polysaccharides, and promotes the release of polysaccharides, significantly improving the extraction rate of astragalus polysaccharides.

Description

Technical Field

[0001] This application relates to the technical field of astragalus polysaccharides, and particularly relates to a method for extracting astragalus polysaccharides. Background Art

[0002] As a natural product with a wide range of pharmacological effects, astragalus polysaccharides have been widely used in the fields of traditional Chinese medicine and health products. With the in-depth research on its immunomodulatory, antioxidant, anti-inflammatory and other effects, the market demand for astragalus polysaccharides is increasing continuously. At present, the extraction methods of astragalus polysaccharides mainly include traditional water extraction method, alcohol precipitation method, ultrasonic-assisted extraction method and microwave-assisted extraction method, etc.

[0003] However, in actual application, the water extraction method and alcohol precipitation method only rely on the concentration difference inside and outside the cells to promote the conversion of astragalus polysaccharides from inside the cells to the extractant, and the overall extraction efficiency is relatively low. Although the ultrasonic-assisted extraction method and microwave-assisted extraction method can cause cell rupture and promote more astragalus polysaccharides to be converted from inside the cells to the extractant. However, when producing on a large scale, the requirements for equipment standards and safety are higher, increasing the production cost. Summary of the Invention

[0004] In order to solve the problem of improving the extraction rate of astragalus polysaccharides under the premise of lower equipment standards and safety requirements, this application provides a method for extracting astragalus polysaccharides. By using a weak alkaline solution in the initial water extraction step, the cell wall is destroyed, the solubility of polysaccharides is increased, and the release of polysaccharides is promoted, significantly improving the extraction rate of astragalus polysaccharides.

[0005] In a first aspect, this application provides a method for extracting astragalus polysaccharides, adopting the following technical solution:

[0006] A method for extracting astragalus polysaccharides, comprising the following steps:

[0007] Initial water extraction: Soak astragalus with a weak alkaline solution, then heat to boiling and carry out extraction, and filter to separate the initial precipitate and the initial extract; the weak alkaline solution includes at least one of sodium carbonate solution and sodium bicarbonate solution, and the solute content in the weak alkaline solution is 3-6 wt%;

[0008] Re-water extraction: Soak the initial precipitate with water, then heat to boiling and carry out extraction, filter and collect the re-extract, and mix the initial extract and the re-extract to obtain a water extraction solution;

[0009] Vacuum concentration: Concentrate the water extraction solution under reduced pressure to obtain a concentrated solution;

[0010] Initial alcohol precipitation: Mix the concentrated solution with ethanol, let it stand for stratification, remove the supernatant to obtain an initial alcohol precipitate;

[0011] Redissolution and ethanol precipitation: Dissolve the primary ethanol-precipitated product in water to obtain a solution; mix the solution with ethanol, let it stand for layering, and remove the supernatant to obtain crude Astragalus polysaccharide;

[0012] Purification: Purify the crude Astragalus polysaccharide by chromatography to obtain Astragalus polysaccharide.

[0013] By adopting the above technical solution, the cell wall of Astragalus is composed of complex polysaccharides such as cellulose, hemicellulose and pectin, and these components form a certain barrier to the release of Astragalus polysaccharide. Soaking Astragalus in a weak alkaline solution (such as sodium carbonate solution) can change the pH value of the internal and external environments of the cell wall, resulting in partial destruction or relaxation of the cell wall structure. This dual physical and chemical effect helps to break the cell wall, making the Astragalus polysaccharide originally bound inside the cell easier to be released. The weak alkaline condition can not only break the cell wall, but also increase the solubility of Astragalus polysaccharide in water by affecting the charge interaction between polysaccharide molecules. The polysaccharide molecules may undergo conformational changes in the weak alkaline environment, reducing the intermolecular entanglement and aggregation, thus being more conducive to the dissolution of polysaccharides from the cells and their dispersion into the extract.

[0014] After using the weak alkaline solution in the primary water extraction stage, heating to boiling further promotes the dissolution and release of polysaccharides. Heating can not only accelerate the molecular movement speed, but also reduce the viscosity of the solution, which is beneficial to the transfer of polysaccharide molecules from the solid phase to the liquid phase. Subsequently, through filtration and separation, a primary extract containing a high concentration of Astragalus polysaccharide can be obtained. The re-water extraction step in the method is the secondary utilization of the primary precipitate, aiming to extract more Astragalus polysaccharide from the residue where polysaccharides were not fully released during the first extraction. This stepwise extraction strategy can significantly improve the overall recovery rate of polysaccharides and ensure the efficient utilization of resources.

[0015] This application significantly improves the extraction rate of Astragalus polysaccharide by using a weak alkaline solution in the primary water extraction step to break the cell wall, increase the solubility of polysaccharides and promote the release of polysaccharides.

[0016] Preferably, in the re-water extraction step, amylase is added when soaking the primary precipitate with water.

[0017] By adopting the above technical solution, after the primary water extraction, part of the Astragalus polysaccharide is extracted into the primary extract in a water-soluble form, but there is still a small amount of polysaccharide (such as water-insoluble glucan) remaining in the primary precipitate. Adding amylase can specifically act on these water-insoluble glucans, hydrolyze their glycosidic bonds, and decompose them into water-soluble polysaccharides. The originally difficult-to-extract water-insoluble polysaccharides are converted into a form more soluble in water, thus improving the overall extraction rate of polysaccharides.

[0018] Amylase can work efficiently under suitable temperature and pH conditions, but it will be inactivated at high temperatures. In the re-aqueous extraction step, when the water boils, the amylase will lose its activity due to the high temperature, thus stopping the further hydrolysis of polysaccharides. This means that amylase mainly decomposes water-insoluble dextran into water-soluble polysaccharides and it is difficult to further decompose these polysaccharides into monosaccharides (such as glucose), thus ensuring the structural integrity and high extraction rate of astragalus polysaccharides.

[0019] Adding amylase in the re-aqueous extraction step can significantly improve the extraction rate of astragalus polysaccharides, avoid excessive degradation of polysaccharides, optimize the extraction process, and improve the product quality.

[0020] Preferably, the mass ratio of the astragalus to the amylase is 1000:0.8 - 1.5.

[0021] By adopting the above technical solution, if the content of amylase is too low, its enzymatic hydrolysis effect may not be sufficient to completely decompose the water-insoluble dextran in the initial precipitate. This will result in some polysaccharides still existing in an insoluble form and unable to be effectively extracted into the filtrate, thus reducing the extraction rate of polysaccharides. If the content of amylase is too high, at this time the water-soluble dextran has basically been decomposed and it is difficult to further improve the extraction rate of polysaccharides. Considering the production cost, there is no need to further increase the addition amount of amylase.

[0022] Preferably, in the re-aqueous extraction step, the extraction time is 0.8 - 1.2 h.

[0023] By adopting the above technical solution, if the extraction time is too short, the polysaccharides in astragalus cells may not be fully released into the extraction solution. This will lead to a reduction in the polysaccharide extraction rate, thus affecting the yield and quality of the product. If the time is too long, the polysaccharide extraction rate is difficult to further increase. Considering the cost, there is no need to further increase the extraction time.

[0024] Preferably, in the re-aqueous extraction step, heat-resistant amylase is added 10 - 20 minutes before the end of extraction.

[0025] By adopting the above technical solution, heat-resistant amylase can maintain its activity in boiling water, which means it can continue to play a role in the later stage of the extraction process. By adding heat-resistant amylase 10 - 20 minutes before the end of extraction, it can ensure that the enzyme has enough time to act on the water-insoluble dextran and convert it into water-soluble polysaccharides. At the same time, since the extraction process is about to end, the risk of further degradation of polysaccharides into monosaccharides caused by too long enzymatic hydrolysis time is avoided.

[0026] In the later stage of the extraction process, a large amount of water-soluble polysaccharides has accumulated in the solution. At this time, adding heat-resistant amylase can further release the water-insoluble glucan that was originally difficult to extract and convert it into a water-soluble form, thereby increasing the overall extraction rate of polysaccharides.

[0027] Preferably, the mass ratio of the astragalus to the heat-resistant amylase is 1000:1 - 2.

[0028] By adopting the above technical solution, if the content of heat-resistant amylase is too high, its enzymatic hydrolysis effect may be too strong, not only decomposing water-insoluble glucan, but also possibly further decomposing the water-soluble polysaccharides that have been released into the filtrate. This will lead to the breakage of the polysaccharide molecular chain, reducing the molecular weight of the polysaccharide, and thus affecting its biological activity and application effect.

[0029] If the content of heat-resistant amylase is too low, its enzymatic hydrolysis effect may not be sufficient to completely decompose the water-insoluble glucan in the primary precipitate. This will result in part of the polysaccharides still existing in an insoluble form and unable to be effectively extracted into the filtrate, thereby reducing the extraction rate of polysaccharides.

[0030] Preferably, in the step of re-water extraction, amylase is added when soaking the primary precipitate with water.

[0031] By adopting the above technical solution, after the first water extraction, part of the astragalus polysaccharides are extracted in a water-soluble form, but there are still some polysaccharides (mainly water-insoluble glucan) remaining in the primary precipitate. At the beginning of the re-water extraction step, by adding ordinary amylase to the water for soaking the primary precipitate, these remaining water-insoluble glucans can be decomposed and converted into water-soluble polysaccharides, thereby increasing the release rate of polysaccharides. Before the end of the extraction, adding heat-resistant amylase can further decompose the newly generated water-insoluble glucan during the re-water extraction process to ensure the full extraction of polysaccharides.

[0032] Preferably, the mass ratio of the amylase to the heat-resistant amylase is 1:0.3 - 0.6.

[0033] By adopting the above technical solution, if the proportion of heat-resistant amylase is too low, its enzymatic hydrolysis effect may not be sufficient to completely decompose the water-insoluble glucan generated during the re-water extraction process. This will lead to a decrease in the polysaccharide extraction rate because part of the polysaccharides still exist in an insoluble form and cannot be effectively extracted.

[0034] If the proportion of heat-resistant amylase is too high, while decomposing water-insoluble glucan, heat-resistant amylase will also decompose water-soluble glucan, instead reducing the polysaccharide extraction rate.

[0035] Preferably, in the first alcohol precipitation step, after the concentrated solution is mixed with ethanol, hydrochloric acid is added to form a first mixed solution. The content of ethanol in the first mixed solution is 70-75 wt%, and the content of hydrochloric acid in the first mixed solution is 3-6 wt%.

[0036] By adopting the above technical solution, ethanol acts as a precipitant during the alcohol precipitation process, which can reduce the polarity of the solution and promote the precipitation of effective components such as polysaccharides from the solution. After the addition of hydrochloric acid, the solubility of polysaccharide molecules will be further reduced, promoting the easier precipitation of polysaccharide molecules from the solution.

[0037] Of course, in the first alcohol precipitation step, after the concentrated solution is mixed with ethanol and hydrochloric acid is added to form a first mixed solution, the contents of ethanol and hydrochloric acid have an important impact on the extraction rate and activity of astragalus polysaccharide.

[0038] If the ethanol content is too low, its precipitation ability will be weakened, resulting in insufficient precipitation of effective components such as polysaccharides, thus reducing the extraction rate of astragalus polysaccharide. Although high-concentration ethanol can enhance the precipitation effect, too high an ethanol content may damage the structure of polysaccharides, leading to a decrease in the activity of polysaccharides. The activity of polysaccharides is the basis of their biological functions, so maintaining the activity of polysaccharides is crucial for the extraction and purification process.

[0039] If the hydrochloric acid content is too low, the effect of hydrochloric acid on the solubility of polysaccharide molecules is relatively low, so the promotion effect on the extraction rate of astragalus polysaccharide is limited. However, high-concentration hydrochloric acid may damage the structure of polysaccharides, leading to a decrease in the activity of polysaccharides. The activity of polysaccharides is closely related to their structure and function, so maintaining the structural integrity of polysaccharides is crucial for maintaining their activity.

[0040] Preferably, in the second alcohol precipitation step, after the dissolved solution is mixed with ethanol, hydrochloric acid is added to form a second mixed solution. The content of ethanol in the second mixed solution is 70-75 wt%, and the content of hydrochloric acid in the second mixed solution is 3-6 wt%.

[0041] By adopting the above technical solution, as described above, ethanol and hydrochloric acid also need appropriate contents in the second mixed solution.

[0042] To sum up, the present application has the following beneficial effects:

[0043] 1. Since the present application uses a weak alkaline solution in the first water extraction step to break the cell wall, increase the solubility of polysaccharides and promote the release of polysaccharides, the extraction rate of astragalus polysaccharide is significantly improved;

[0044] 2. In the second water extraction step of the present application, whether amylase and / or heat-resistant amylase is added, it can decompose water-insoluble glucan into water-soluble polysaccharides, thereby increasing the extraction rate of astragalus polysaccharide;

[0045] 3. In the primary alcohol precipitation and / or secondary alcohol precipitation steps of the present application, 3 - 6 wt% hydrochloric acid and 70 - 75 wt% ethanol are added, which can not only improve the extraction rate of astragalus polysaccharide, but also ensure the activity of astragalus polysaccharide. Detailed implementation manners

[0046] The raw materials in the present application include the following parts:

[0047] Astragalus membranaceus: commercially available medicinal material;

[0048] Sodium carbonate: commercially available product with CAS number 497 - 19 - 8;

[0049] Sodium bicarbonate: commercially available product with CAS number 144 - 55 - 8;

[0050] Water: commercially available product with CAS number 7732 - 18 - 5;

[0051] Ethanol: commercially available product with CAS number 64 - 17 - 5;

[0052] Amylase: commercially available product from Shandong Pingju Biotechnology Co., Ltd.;

[0053] Heat - resistant amylase: commercially available product from Weifang Ruichen Biotechnology Co., Ltd.;

[0054] The present application will be further described in detail below with reference to examples and comparative examples.

[0055] Example 1

[0056] A method for extracting astragalus polysaccharide includes the following steps:

[0057] Primary water extraction: Soak 10 kg of astragalus membranaceus with 40 kg of sodium carbonate solution (sodium carbonate content is 5 wt%) for 20 min, then heat to boiling and carry out extraction for 2 h, and filter to separate the primary precipitate and the primary extract;

[0058] Secondary water extraction: Soak the primary precipitate with 40 kg of water for 15 min, then heat to boiling and carry out extraction for 1.2 h, filter to collect the secondary extract, and mix the primary extract and the secondary extract to obtain the water - extracted solution;

[0059] Vacuum concentration: Vacuum - concentrate the water - extracted solution with a vacuum degree above - 0.08 Mpa to obtain 11 kg of concentrated solution;

[0060] Primary alcohol precipitation: Mix the concentrated solution with absolute ethanol so that the ethanol content in the mixed solution is 70 wt%, let it stand for 24 h to be stable in layers, remove the supernatant to obtain the primary alcohol precipitate;

[0061] Redissolution and ethanol precipitation: Dissolve the crude ethanol precipitate with water at a weight ratio of 1:4 for 30 min to obtain a solution. Mix the solution with absolute ethanol to make the ethanol content in the mixture 75 wt%, let it stand for 24 h for stratification, remove the supernatant to obtain crude astragalus polysaccharide.

[0062] Purification: Purify the crude astragalus polysaccharide by chromatography to obtain astragalus polysaccharide.

[0063] Examples 2 - 4

[0064] Based on the preparation method of Example 1, for Examples 2 - 3, adjust the mass fraction of sodium carbonate as shown in Table 1.

[0065] Based on the preparation method of Example 1, for Example 4, replace the sodium carbonate solution with a sodium bicarbonate solution (sodium bicarbonate content is 5 wt%).

[0066] Comparative Examples 1 - 2

[0067] Based on the preparation method of Example 1, for Comparative Example 1, adjust the mass fraction of sodium carbonate as shown in Table 1.

[0068] Based on the preparation method of Example 1, for Comparative Example 2, replace the sodium carbonate solution with water, with other conditions unchanged.

[0069] Table 1 Mass fraction and performance test table of sodium carbonate in Examples 1 - 4 and Comparative Examples 1 - 2

[0070]

[0071] Performance detection test

[0072] Perform the following performance detections on the astragalus polysaccharides of Examples 1 - 4 and Comparative Examples 1 - 2, and the detection results are shown in Table 1.

[0073] Measure the weight of astragalus polysaccharide, and calculate the extraction rate = (weight of astragalus polysaccharide / weight of astragalus) * 100%.

[0074] Referring to Table 1, by comparing Examples 1 - 4 and Comparative Examples 1 - 2, it can be seen that soaking astragalus with sodium carbonate solution or sodium bicarbonate solution can improve the extraction rate of astragalus polysaccharide. This is mainly because the weak alkaline solution can break the cell wall of astragalus, increase the solubility of polysaccharide and promote the release of polysaccharide, thus improving the extraction rate of astragalus polysaccharide.

[0075] As the mass fraction of sodium carbonate increases continuously, the extraction rate of astragalus polysaccharide shows a trend of first increasing and then decreasing. This may be because excessive sodium carbonate will cause the decomposition of astragalus polysaccharide, thus reducing the extraction rate of astragalus polysaccharide. After comparison, Example 1 can be used as the preferred one.

[0076] Examples 5 - 9

[0077] Example 5 On the basis of the preparation method of Example 1, in the step of re-aqueous extraction, 15 g of amylase was added while soaking the primary precipitate with water.

[0078] Examples 6-9 On the basis of the preparation method of Example 5, the addition amount of amylase was adjusted, and the specific adjustment is shown in Table 2.

[0079] The astragalus polysaccharides of Examples 5-9 were subjected to the above performance tests, and the test results are shown in Table 2.

[0080] Table 2 Addition amount of amylase and performance test table of Examples 1 and 5-9

[0081]

[0082] Referring to Table 2, by comparing Example 1 and Examples 5-9, it can be seen that adding amylase when soaking the primary precipitate with water can further improve the extraction rate of astragalus polysaccharide. This is mainly because a small amount of polysaccharides (such as water-insoluble dextran) remain in the primary precipitate. Adding amylase can specifically act on these water-insoluble dextrans, and by hydrolyzing their glycosidic bonds, break them down into water-soluble polysaccharides. The originally difficult-to-extract water-insoluble polysaccharides are thus converted into a form more soluble in water, thereby increasing the overall extraction rate of polysaccharides.

[0083] As the addition amount of amylase increases continuously, the extraction rate of astragalus polysaccharide shows a trend of first increasing and then leveling off. Perhaps as the addition amount of amylase increases continuously, more water-insoluble dextrans are decomposed and converted into water-soluble polysaccharides, thus increasing the extraction rate of astragalus polysaccharide.

[0084] Examples 10-13

[0085] Examples 10-13 On the basis of the preparation method of Example 1, the extraction time during re-aqueous extraction was adjusted, and the specific adjustment is shown in Table 3.

[0086] The astragalus polysaccharides of Examples 10-13 were subjected to the above performance tests, and the test results are shown in Table 3.

[0087] Table 3 Extraction time during re-aqueous extraction and performance test table of Examples 1 and 10-13

[0088]

[0089] Referring to Table 3, by comparing Example 1 and Examples 10-13, it can be seen that as the extraction time increases continuously, the extraction rate of astragalus polysaccharide shows a trend of first increasing and then leveling off. Perhaps as the extraction time increases continuously, the polysaccharides in astragalus cells are gradually and fully released into the extraction solution, thus increasing the extraction rate of astragalus polysaccharide.

[0090] Examples 14 - 18

[0091] Based on the preparation method of Example 1, in the step of re - aqueous extraction of Example 14, 15 g of heat - resistant amylase was added 15 minutes before the end of extraction.

[0092] Based on the preparation method of Example 1, for Examples 15 - 18, the addition time of heat - resistant amylase was adjusted, and the specific adjustment is shown in Table 4.

[0093] The astragalus polysaccharides of Examples 14 - 18 were subjected to the above - mentioned performance tests, and the test results are shown in Table 4.

[0094] Table 4 Addition time and performance test table of heat - resistant amylase in Example 1 and Examples 14 - 18

[0095]

[0096] Referring to Table 4, by comparing Example 1 and Examples 14 - 18, it can be seen that as the addition time of heat - resistant amylase increases, the extraction rate of astragalus polysaccharide shows a trend of first increasing and then decreasing. This may be because as the addition time of heat - resistant amylase increases, a large amount of water - soluble polysaccharides have accumulated in the solution. At this time, adding heat - resistant amylase can further release the originally difficult - to - extract water - insoluble glucan and convert it into a water - soluble form, thereby increasing the overall extraction rate of polysaccharides. When exceeding a certain range, too long enzymolysis time may cause some polysaccharides to be further degraded into monosaccharides, resulting in a decrease in the extraction rate of astragalus polysaccharide.

[0097] Examples 19 - 22

[0098] Based on the preparation method of Example 14, for Examples 19 - 22, the addition amount of heat - resistant amylase was adjusted, and the specific adjustment is shown in Table 5.

[0099] The astragalus polysaccharides of Examples 19 - 22 were subjected to the above - mentioned performance tests, and the test results are shown in Table 5 respectively.

[0100] Table 5 Addition amount and performance test table of heat - resistant amylase in Example 1, Example 14 and Examples 19 - 22

[0101]

[0102] Referring to Table 5, by comparing Example 1, Example 14 and Examples 19 - 22, it can be seen that as the addition amount of heat-resistant amylase increases, the extraction rate of astragalus polysaccharide shows a trend of first increasing and then decreasing. This may be because as the addition amount of heat-resistant amylase increases, both the water-insoluble glucan left during the initial water extraction and the water-insoluble glucan extracted later are decomposed into water-soluble polysaccharides, thus increasing the extraction rate of astragalus polysaccharide. When exceeding a certain range, it may further decompose the water-soluble polysaccharides, thereby reducing the extraction rate of astragalus polysaccharide.

[0103] Examples 23 - 27

[0104] Based on the preparation method of Example 1, 10 g of amylase was added when soaking the initial precipitate in water in Example 23. In the step of re-water extraction, 5 g of heat-resistant amylase was added 15 min before the end of extraction.

[0105] Based on the preparation method of Example 23, in Examples 24 - 27, the total amount of amylase and heat-resistant amylase was 15 g, and the mass ratio of amylase to heat-resistant amylase was adjusted. The specific adjustment is shown in Table 6.

[0106] The astragalus polysaccharides of Examples 23 - 27 were subjected to the above performance tests, and the test results are shown in Table 6.

[0107] Table 6 Mass ratio of amylase and heat-resistant amylase and performance test table of Example 1 and Examples 23 - 27

[0108]

[0109] Referring to Table 6, by comparing Example 1 and Examples 23 - 27, it can be seen that at the beginning of the re-water extraction step, by adding ordinary amylase to the water for soaking the initial precipitate, the residual water-insoluble glucan can be decomposed and converted into water-soluble polysaccharides, thereby increasing the release rate of polysaccharides. Before the end of extraction, adding heat-resistant amylase can further decompose the newly generated water-insoluble glucan during the re-water extraction process to ensure the full extraction of polysaccharides.

[0110] As the mass ratio of amylase to heat-resistant amylase decreases, the extraction rate of astragalus polysaccharide shows a trend of first increasing and then decreasing. This may be because as the mass ratio of amylase to heat-resistant amylase decreases, the content of heat-resistant amylase continuously increases, which can continuously decompose the water-insoluble glucan generated during the re-water extraction process, thereby increasing the extraction rate of astragalus polysaccharide. When exceeding a certain range, while decomposing the water-insoluble glucan, the heat-resistant amylase will also decompose the water-soluble polysaccharides, instead reducing the polysaccharide extraction rate.

[0111] Examples 28 - 32

[0112] Example 28 On the basis of the preparation method of Example 1, after the concentrated solution is mixed with absolute ethanol, 15wt% dilute hydrochloric acid is added to form a first mixed solution. Finally, the content of ethanol in the first mixed solution is 70wt%, and the content of hydrochloric acid in the first mixed solution is 5wt%.

[0113] Examples 29 - 32 On the basis of the preparation method of Example 28, the contents of ethanol and hydrochloric acid in the first mixed solution are adjusted, and the specific adjustments are shown in Table 7.

[0114] Comparative Examples 3 - 7

[0115] Comparative Examples 3 - 7 On the basis of the preparation method of Example 28, the contents of ethanol and hydrochloric acid in the first mixed solution are adjusted, and the specific adjustments are shown in Table 7.

[0116] The astragalus polysaccharides of Examples 28 - 32 and Comparative Examples 3 - 7 were subjected to performance tests, and the test results are shown in Table 7.

[0117] Table 7 Data table of the contents of ethanol and hydrochloric acid in the first mixed solution and performance test data of Example 1, Examples 28 - 32 and Comparative Examples 3 - 7

[0118]

[0119] Performance test

[0120] Take healthy white mice, 8 mice in each group of examples or comparative examples, with 4 males and 4 females in each group. In the dosing group, each mouse was intraperitoneally injected with the test sample, and in the blank group, each mouse was intraperitoneally injected with normal saline. The injection was carried out once a day for 7 consecutive days. 24 hours after the last injection, the animals were sacrificed, their weights were measured, their spleens were taken and weighed, and the average spleen index was calculated. (Spleen index = spleen weight (mg) / body weight (g), average spleen index = sum of spleen indices within the group / number of animals within the group)

[0121] Referring to Table 7, by comparing Example 1, Examples 28 - 32 and Comparative Examples 3 - 7, it can be seen that compared with Comparative Examples 3 - 4, the precipitation ability of ethanol with a lower content will be weakened, resulting in insufficient precipitation of effective components such as polysaccharides, thereby reducing the extraction rate of astragalus polysaccharides. In addition, although hydrochloric acid with a higher content can improve the extraction rate of astragalus polysaccharides, its combined effect with ethanol with a lower content is poor.

[0122] Compared with Comparative Example 5, although ethanol with a higher content can improve the extraction rate of astragalus polysaccharides, it may damage the structure of the polysaccharides, resulting in a decrease in the activity of the polysaccharides. Compared with Comparative Examples 6 - 7, when ethanol with a higher content is combined with hydrochloric acid, although it can improve the extraction rate of astragalus polysaccharides, it will seriously damage the activity of astragalus polysaccharides.

[0123] Example 33

[0124] Example 33 On the basis of the preparation method of Example 1, after the dissolution solution is mixed with ethanol, 15 wt% dilute hydrochloric acid is added to form a second mixed solution. Finally, the ethanol content in the second mixed solution is 75 wt%, and the hydrochloric acid content in the second mixed solution is 5 wt%.

[0125] Perform performance testing on the astragalus polysaccharide of Example 33, and the test results are shown in Table 8.

[0126] Table 8 Data table of the content and performance testing of hydrochloric acid in the second mixed solution of Example 1, Example 32 and Example 33

[0127]

[0128] Referring to Table 8, by comparing Example 1, Example 32 and Example 33, it can be seen that after the dissolution solution is mixed with ethanol and hydrochloric acid is added, the reason is similar to the principle of the first mixed solution. In addition, since most of the impurities have been removed by the initial alcohol precipitation, the polysaccharide content in the solution is relatively high at this time. Therefore, changing the ionic strength at this time has a more significant effect on polysaccharide precipitation, and the extraction rate of astragalus polysaccharide can be further improved.

[0129] This specific embodiment is only an interpretation of the present application, and it does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for extracting astragalus polysaccharides, characterized in that: The following steps are involved: Initial water extraction: soaking the astragalus in a weak alkaline solution, then heating to boiling for extraction, filtering and separating the initial precipitate and the initial extract; the weak alkaline solution includes at least one of a sodium carbonate solution and a sodium bicarbonate solution, and the solute content in the weak alkaline solution is 3-6wt%; Re-water extraction: soak the initial precipitate with water and add amylase, then heat to boiling and extract, the extraction time is 0.8-1.2h, add heat-resistant amylase 10-20min before the end of extraction, filter and collect the re-extract, mix the initial extract and the re-extract to obtain a water extract; Concentrating under reduced pressure: concentrating the water extract under reduced pressure to obtain a concentrated solution; Primary alcohol precipitation: the concentrated solution is mixed with ethanol, and then hydrochloric acid is added to form a first mixed solution, the mixture is allowed to stand for stratification, and the supernatant is removed to obtain a primary alcohol precipitate; the content of the ethanol in the first mixed solution is 70-75wt%, and the content of the hydrochloric acid in the first mixed solution is 3-6wt%; Re-alcohol precipitation: dissolving the primary alcohol precipitation with water to obtain a solution; mixing the solution with ethanol, standing for stratification, removing the supernatant, and obtaining crude astragalus polysaccharide; Purification: Purify the crude astragalus polysaccharide to obtain astragalus polysaccharide.

2. The method for extracting astragalus polysaccharides according to claim 1, characterized in that: The mass ratio of the astragalus to the amylase is 1000:0.8-1.

5.

3. The method for extracting astragalus polysaccharides according to claim 1, characterized in that: The mass ratio of the astragalus to the heat-resistant amylase is 1000:1-2.

4. The method for extracting astragalus polysaccharides according to claim 1, characterized in that: The mass ratio of the amylase to the thermostable amylase is 1:0.3-0.

6.

5. The method for extracting astragalus polysaccharides according to claim 1, characterized in that: In the alcohol precipitation step, after the dissolving solution is mixed with ethanol, hydrochloric acid is added to form a second mixed solution, the content of ethanol in the second mixed solution is 70-75wt%, and the content of hydrochloric acid in the second mixed solution is 3-6wt%.

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