Extraction method of astragalus polysaccharide

Abstract

The invention relates to the technical field of astragalus polysaccharide, in particular to an extraction method of astragalus polysaccharide. An extraction method of astragalus polysaccharide comprises the following steps: primary water extraction, secondary water extraction, vacuum concentration, primary alcohol precipitation, secondary alcohol precipitation and purification, specifically, the primary water extraction comprises the following steps: soaking astragalus with a weakly alkaline solution, heating until boiling, extracting, and filtering to separate primary precipitate and primary extract; the weakly alkaline solution is used in the primary water extraction step, so that cell walls are damaged, the solubility of the polysaccharide is improved, the release of the polysaccharide is promoted, and the extraction rate of the astragalus polysaccharide is remarkably improved.

Description

Technical Field

[0001] The present application relates to the technical field of astragalus polysaccharides, and in particular to a method for extracting astragalus polysaccharides. Background Art

[0002] As a natural product with a wide range of pharmacological effects, astragalus polysaccharide has been widely used in the field 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 polysaccharide continues to increase. At present, the extraction methods of astragalus polysaccharide mainly include traditional water extraction, alcohol precipitation, ultrasound-assisted extraction and microwave-assisted extraction.

[0003] However, in actual use, water extraction and alcohol precipitation methods only rely on the concentration difference between the inside and outside of cells to promote the conversion of astragalus polysaccharides from cells to the extractant, and the overall extraction efficiency is low. Although ultrasonic-assisted extraction and microwave-assisted extraction can cause cell rupture and promote the conversion of more astragalus polysaccharides from cells to the extractant, large-scale production requires higher equipment standards and safety, which increases production costs. Summary of the invention

[0004] In order to improve the extraction rate of astragalus polysaccharides under the premise of lower equipment standards and safety requirements, the present application provides a method for extracting astragalus polysaccharides, which significantly improves the extraction rate of astragalus polysaccharides by using a weak alkaline solution in the initial water extraction step to destroy the cell wall, increase the solubility of polysaccharides and promote the release of polysaccharides.

[0005] In the first aspect, the present application provides a method for extracting astragalus polysaccharides, using the following technical solution: A method for extracting astragalus polysaccharide comprises the following steps: 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: soaking the initial precipitate in water, then heating it to boiling for extraction, filtering and collecting the re-extracted solution, mixing the initial extract and the re-extracted solution to obtain a water-extracted extract; Concentrating under reduced pressure: concentrating the water extract under reduced pressure to obtain a concentrated solution; Primary alcohol precipitation: mixing the concentrated solution with ethanol, standing for stratification, removing the supernatant, and obtaining a primary alcohol precipitate; 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: The crude astragalus polysaccharide is purified by chromatography to obtain astragalus polysaccharide.

[0006] By adopting the above technical scheme, the cell wall of Astragalus is composed of complex polysaccharides such as cellulose, hemicellulose and pectin, which form a certain barrier to the release of Astragalus polysaccharides. Soaking Astragalus in a weak alkaline solution (such as sodium carbonate solution) can cause partial destruction or relaxation of the cell wall structure by changing the pH value of the environment inside and outside the cell wall. This dual physical and chemical effect helps to break the cell wall, making it easier to release the Astragalus polysaccharides that were originally bound in the cell. Weakly alkaline conditions can not only destroy the cell wall, but also increase the solubility of Astragalus polysaccharides in water by affecting the charge interaction between polysaccharide molecules. Polysaccharide molecules may undergo conformational changes in a weakly alkaline environment, reducing the mutual entanglement and aggregation between molecules, which is more conducive to the dissolution of polysaccharides from the cell and dispersion into the extract.

[0007] After using a weak alkaline solution in the initial water extraction stage, the dissolution and release of polysaccharides are further promoted by heating to boiling. Heating not only accelerates the molecular movement speed, but also reduces the viscosity of the solution, which is beneficial to the transfer of polysaccharide molecules from the solid phase to the liquid phase. Subsequently, by filtration and separation, a primary extract containing a high concentration of astragalus polysaccharides can be obtained. The re-water extraction step in the method is a secondary utilization of the initial precipitate, aiming to extract more astragalus polysaccharides from the residues that failed to completely release the polysaccharides in the first extraction. This step-by-step extraction strategy can significantly improve the overall recovery rate of polysaccharides and ensure efficient use of resources.

[0008] The present application uses a weak alkaline solution in the initial water extraction step to destroy the cell wall, increase the solubility of the polysaccharide and promote the release of the polysaccharide, thereby significantly improving the extraction rate of astragalus polysaccharide.

[0009] Preferably, in the step of re-extraction, amylase is added when the primary precipitate is soaked in water.

[0010] By adopting the above technical scheme, after the initial water extraction, part of the astragalus polysaccharides are extracted into the primary extract in a water-soluble form, but a small amount of polysaccharides (such as water-insoluble glucans) remain in the primary precipitate. The addition of amylase can specifically act on these water-insoluble glucans and decompose them into water-soluble polysaccharides by hydrolyzing their glycosidic bonds. The water-insoluble polysaccharides that were originally difficult to extract are converted into a form that is more soluble in water, thereby improving the overall extraction rate of polysaccharides.

[0011] Amylase can work efficiently under suitable temperature and pH conditions, but it will be inactivated at high temperatures. In the re-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 glucans 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.

[0012] Adding amylase in the re-extraction step can significantly improve the extraction rate of astragalus polysaccharides, while avoiding excessive degradation of polysaccharides, optimizing the extraction process, and improving product quality.

[0013] Preferably, the mass ratio of the astragalus to the amylase is 1000:0.8-1.5.

[0014] By adopting the above technical solution, if the content of amylase is too low, its enzymatic action may not be sufficient to completely decompose the water-insoluble glucan in the initial precipitate. This will cause some polysaccharides to still exist in an insoluble form and cannot be effectively extracted into the filtrate, thereby reducing the extraction rate of polysaccharides. If the content of amylase is too high, the water-soluble glucan has been basically decomposed at this time, and it is difficult to further improve the extraction rate of polysaccharides. For production cost considerations, there is no need to further increase the amount of amylase added.

[0015] Preferably, in the step of re-extraction with water, the extraction time is 0.8-1.2 hours.

[0016] By adopting the above technical solution, if the extraction time is too short, the polysaccharides in the Astragalus cells may not be fully released into the extract. This will lead to a decrease in the polysaccharide extraction rate, thereby affecting the yield and quality of the product. If the time is too long, the polysaccharide extraction rate is difficult to further increase. For cost considerations, there is no need to further increase the extraction time.

[0017] Preferably, in the step of re-extraction with water, a thermostable amylase is added 10-20 minutes before the end of the extraction.

[0018] By adopting the above technical solution, the thermostable amylase can remain active in boiling water, which means that it can continue to work in the later stages of the extraction process. By adding the thermostable amylase 10-20 minutes before the end of the extraction, it can be ensured that the enzyme has enough time to act on the water-insoluble glucan 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 due to excessive enzymatic hydrolysis time is avoided.

[0019] In the later stages of the extraction process, a large amount of water-soluble polysaccharides have accumulated in the solution. At this time, the addition of thermostable amylase can further release the water-insoluble glucans that were originally difficult to extract and convert them into water-soluble forms, thereby improving the overall extraction rate of polysaccharides.

[0020] Preferably, the mass ratio of the astragalus to the thermostable amylase is 1000:1-2.

[0021] By adopting the above technical solution, if the content of thermostable amylase is too high, its enzymatic hydrolysis may be too strong, not only decomposing water-insoluble glucan, but also further decomposing water-soluble polysaccharides that have been released into the filtrate. This will lead to the breakage of polysaccharide molecular chains and reduce the molecular weight of polysaccharides, thereby affecting their biological activity and application effects.

[0022] If the content of thermostable amylase is too low, its enzymatic action may not be sufficient to completely decompose the water-insoluble glucan in the primary precipitate. This will cause some polysaccharides to remain in an insoluble form and cannot be effectively extracted into the filtrate, thereby reducing the extraction rate of polysaccharides.

[0023] Preferably, in the step of re-extraction, amylase is added when the primary precipitate is soaked in water.

[0024] By adopting the above technical scheme, after the initial water extraction, part of the astragalus polysaccharide is extracted in a water-soluble form, but part of the polysaccharide (mainly water-insoluble glucan) remains in the initial precipitate. At the beginning of the re-water extraction step, by adding ordinary amylase to the water in which the initial precipitate is soaked, these residual water-insoluble glucans can be decomposed and converted into water-soluble polysaccharides, thereby increasing the release rate of the polysaccharide. Before the end of the extraction, the addition of heat-resistant amylase can further decompose the newly generated water-insoluble glucan during the re-water extraction process to ensure the full extraction of the polysaccharide.

[0025] Preferably, the mass ratio of the amylase to the thermostable amylase is 1:0.3-0.6.

[0026] By adopting the above technical solution, if the proportion of thermostable amylase is too low, its enzymatic action may not be sufficient to completely decompose the water-insoluble glucan produced during the water extraction process. This will lead to a decrease in the polysaccharide extraction rate because some polysaccharides still exist in an insoluble form and cannot be effectively extracted.

[0027] If the proportion of heat-resistant amylase is too high, the heat-resistant amylase will decompose water-soluble glucan while decomposing water-insoluble glucan, which will reduce the polysaccharide extraction rate.

[0028] Preferably, in the step of primary alcohol precipitation, after the concentrated solution is mixed with ethanol, hydrochloric acid is added to form a first mixed solution, 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%.

[0029] By adopting the above technical solution, ethanol is used as a precipitant in the alcohol precipitation process to reduce the polarity of the solution and promote the precipitation of effective ingredients such as polysaccharides from the solution. After the addition of hydrochloric acid, the solubility of the polysaccharide molecules will be further reduced, which will promote the polysaccharide molecules to precipitate more easily from the solution.

[0030] Of course, in the initial alcohol precipitation step, the concentrate is mixed with ethanol and then hydrochloric acid is added to form a first mixed solution, in which the content of ethanol and hydrochloric acid has an important influence on the extraction rate and activity of astragalus polysaccharides.

[0031] If the ethanol content is too low, its precipitation ability will be weakened, resulting in the inability to fully precipitate effective ingredients such as polysaccharides, thereby reducing the extraction rate of astragalus polysaccharides. Although high concentrations of ethanol can enhance the precipitation effect, too high ethanol content may damage the structure of polysaccharides, resulting in reduced 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.

[0032] If the hydrochloric acid content is too low, the effect of hydrochloric acid on the solubility of polysaccharide molecules is low, thus the effect of promoting the extraction rate of astragalus polysaccharides is limited. However, high concentrations of hydrochloric acid may damage the structure of polysaccharides, resulting in reduced activity of polysaccharides. The activity of polysaccharides is closely related to their structure and function, so maintaining the structural integrity of polysaccharides is crucial to maintaining their activity.

[0033] Preferably, in the step of re-alcohol precipitation, after the dissolving solution is mixed with ethanol, hydrochloric acid is added to form a second mixed solution, the content of the ethanol in the second mixed solution is 70-75wt%, and the content of the hydrochloric acid in the second mixed solution is 3-6wt%.

[0034] By adopting the above technical solution, as mentioned above, the ethanol and hydrochloric acid also need to have appropriate contents in the second mixed liquid.

[0035] In summary, this application has the following beneficial effects: 1. The present application uses a weak alkaline solution in the initial water extraction step to destroy the cell wall, increase the solubility of polysaccharides and promote the release of polysaccharides, thereby significantly improving the extraction rate of astragalus polysaccharides; 2. In the step of water extraction, whether amylase and / or thermostable amylase is added, water-insoluble glucan can be decomposed into water-soluble polysaccharides, thereby improving the extraction rate of astragalus polysaccharides; 3. In the present application, 3-6wt% hydrochloric acid and 70-75wt% ethanol are added in the primary alcohol precipitation and / or secondary alcohol precipitation step, which can not only improve the extraction rate of astragalus polysaccharides, but also ensure the activity of astragalus polysaccharides. DETAILED DESCRIPTION

[0036] The raw materials in this application include the following parts: Astragalus: Commercially available medicinal material; Sodium carbonate: a commercially available product with CAS number 497-19-8; Sodium bicarbonate: a commercially available product with CAS number 144-55-8; Water: a commercial product with CAS number 7732-18-5 was used; Ethanol: a commercially available product with CAS number 64-17-5 was used; Amylase: a commercially available product from Shandong Pingju Biotechnology Co., Ltd. Thermostable amylase: a commercially available product from Weifang Ruichen Biotechnology Co., Ltd. The present application is further described in detail below with reference to examples and comparative examples.

[0037] Example 1 A method for extracting astragalus polysaccharide comprises the following steps: Initial water extraction: soak 10 kg of Astragalus in 40 kg sodium carbonate solution (sodium carbonate content is 5 wt%) for 20 min, then heat to boiling and extract for 2 h, filter and separate the initial precipitate and the initial extract; Re-water extraction: soak the initial precipitate in 40 kg of water for 15 minutes, then heat to boiling and extract for 1.2 hours, collect the re-extracted solution by filtration, mix the initial extract and the re-extracted solution to obtain a water-extracted solution; Concentration under reduced pressure: Concentrate the water extract under reduced pressure, with a vacuum degree of -0.08Mpa or above, to obtain 11kg of concentrated solution; Primary alcohol precipitation: the concentrate was mixed with anhydrous ethanol, the ethanol content in the mixed solution was 70wt%, and the mixture was allowed to stand for 24h to stabilize the layers, and the supernatant was removed to obtain the primary alcohol precipitate; Re-alcohol precipitation: stirring and dissolving the primary alcohol precipitation with water 4 times the weight of the primary alcohol precipitation for 30 minutes to obtain a solution; mixing the solution with anhydrous ethanol, wherein the ethanol content in the mixture is 75wt%, standing for 24 hours to separate the layers, removing the supernatant, and obtaining crude astragalus polysaccharide; Purification: The crude astragalus polysaccharide is purified by chromatography to obtain astragalus polysaccharide.

[0038] Embodiment 2-4 Example 2-3 Based on the preparation method of Example 1, the mass fraction of sodium carbonate is adjusted, and the specific adjustment is shown in Table 1.

[0039] Example 4 Based on the preparation method of Example 1, the sodium carbonate solution is replaced with a sodium bicarbonate solution (sodium bicarbonate content is 5wt%).

[0040] Comparative Example 1-2 Comparative Example 1 Based on the preparation method of Example 1, the mass fraction of sodium carbonate was adjusted, and the specific adjustment is shown in Table 1.

[0041] Comparative Example 2 is based on the preparation method of Example 1, except that the sodium carbonate solution is replaced with water, and other conditions remain unchanged.

[0042] Table 1 Mass fraction and performance test table of sodium carbonate of Examples 1-4 and Comparative Examples 1-2

[0043] Performance testing The astragalus polysaccharides of Examples 1-4 and Comparative Examples 1-2 were subjected to the following performance tests. The test results are shown in Table 1.

[0044] The weight of astragalus polysaccharide was measured and the extraction rate was calculated as (weight of astragalus polysaccharide / weight of astragalus)*100%.

[0045] Referring to Table 1, it can be seen from the comparison between Examples 1-4 and Comparative Examples 1-2 that soaking Astragalus in sodium carbonate solution or sodium bicarbonate solution can improve the extraction rate of Astragalus polysaccharides, mainly because the weak alkaline solution can destroy the Astragalus cell wall, increase the solubility of polysaccharides and promote the release of polysaccharides, thereby improving the extraction rate of Astragalus polysaccharides.

[0046] As the mass fraction of sodium carbonate increases, the extraction rate of astragalus polysaccharide increases first and then decreases, which may be because too much sodium carbonate will cause the decomposition of astragalus polysaccharide, thereby reducing the extraction rate of astragalus polysaccharide. After comparison, Example 1 can be used as a preferred embodiment.

[0047] Embodiment 5-9 Example 5 Based on the preparation method of Example 1, in the step of re-extraction, 15g of amylase is added while soaking the primary precipitate in water.

[0048] In Examples 6-9, based on the preparation method of Example 5, the amount of amylase added was adjusted, and the specific adjustments are shown in Table 2.

[0049] The astragalus polysaccharides of Examples 5-9 were subjected to the above performance tests, and the test results are shown in Table 2.

[0050] Table 2 Addition amount and performance test table of amylase in Example 1 and Examples 5-9

[0051] Referring to Table 2, it can be seen from the comparison between Example 1 and Examples 5-9 that the addition of amylase during the soaking of the primary precipitate in water can further improve the extraction rate of astragalus polysaccharides. This is mainly because a small amount of polysaccharides (such as water-insoluble glucans) remain in the primary precipitate, and the addition of amylase can specifically act on these water-insoluble glucans, hydrolyzing their glycosidic bonds and decomposing them into water-soluble polysaccharides. The water-insoluble polysaccharides that were originally difficult to extract are converted into a form that is more soluble in water, thereby improving the overall extraction rate of the polysaccharides.

[0052] As the amount of amylase added continued to increase, the extraction rate of astragalus polysaccharides showed a trend of increasing and then tending to a stable state. It may be that as the amount of amylase added continued to increase, more water-insoluble glucans were decomposed and converted into water-soluble polysaccharides, thereby improving the extraction rate of astragalus polysaccharides.

[0053] Examples 10-13 In Examples 10-13, based on the preparation method of Example 1, the extraction time during the water extraction was adjusted, and the specific adjustments are shown in Table 3.

[0054] The astragalus polysaccharides of Examples 10-13 were subjected to the above performance tests, and the test results are shown in Table 3.

[0055] Table 3 Extraction time and performance test table of Example 1 and Example 10-13 during re-water extraction

[0056] Referring to Table 3, by comparing Example 1 with Examples 10-13, it can be seen that as the extraction time increases, the extraction rate of astragalus polysaccharides first increases and then tends to be stable. This may be because as the extraction time increases, the polysaccharides in the astragalus cells are gradually and fully released into the extract, thereby improving the extraction rate of astragalus polysaccharides.

[0057] Examples 14-18 Example 14 is based on the preparation method of Example 1. In the step of water extraction, 15 g of heat-resistant amylase is added 15 minutes before the end of extraction.

[0058] In Examples 15-18, based on the preparation method of Example 1, the addition time of the thermostable amylase was adjusted, and the specific adjustments are shown in Table 4.

[0059] The astragalus polysaccharides of Examples 14-18 were subjected to the above performance tests, and the test results are shown in Table 4.

[0060] Table 4 Addition time and performance test table of thermostable amylase in Example 1 and Examples 14-18

[0061] Referring to Table 4, it can be seen from the comparative example 1 and examples 14-18 that, with the increase of the addition time of the thermostable amylase, the extraction rate of astragalus polysaccharide shows a trend of first rising and then falling, which may be due to the increase of the addition time of the thermostable amylase, a large amount of water-soluble polysaccharides have been accumulated in the solution. At this time, adding thermostable amylase can further release the water-insoluble glucan that was originally difficult to extract, and convert it into a water-soluble form, thereby improving the overall extraction rate of polysaccharides. When it exceeds a certain range, the excessive enzymolysis time may cause some polysaccharides to be further degraded into monosaccharides, which in turn causes the extraction rate of astragalus polysaccharides to decrease.

[0062] Examples 19-22 In Examples 19-22, based on the preparation method of Example 14, the amount of heat-resistant amylase added was adjusted, and the specific adjustments are shown in Table 5.

[0063] The astragalus polysaccharides of Examples 19-22 were subjected to the above performance tests, and the test results are shown in Table 5 respectively.

[0064] Table 5 Addition amount and performance test table of thermostable amylase in Example 1, Example 14 and Examples 19-22

[0065] Referring to Table 5, it can be seen from the comparison of Example 1, Example 14 and Examples 19-22 that as the amount of thermostable amylase added increases, the extraction rate of astragalus polysaccharide shows a trend of first increasing and then decreasing. This may be because as the amount of thermostable amylase added increases, the water-insoluble glucan left in the initial water extraction and the water-insoluble glucan extracted later are decomposed into water-soluble polysaccharides, thereby improving the extraction rate of astragalus polysaccharide. When exceeding a certain range, the water-soluble polysaccharide may be further decomposed, thereby reducing the extraction rate of astragalus polysaccharide.

[0066] Examples 23-27 Example 23 Based on the preparation method of Example 1, 10 g of amylase was added when the primary precipitate was soaked in water. In the step of re-extraction, 5 g of thermostable amylase was added 15 minutes before the end of the extraction.

[0067] Examples 24-27 are based on the preparation method of Example 23, except that the total amount of amylase and thermostable amylase is 15 g, and the mass ratio of amylase and thermostable amylase is adjusted, and the specific adjustment is shown in Table 6.

[0068] The astragalus polysaccharides of Examples 23-27 were subjected to the above performance tests, and the test results are shown in Table 6.

[0069] Table 6 Mass ratio and performance test table of amylase and thermostable amylase in Example 1 and Examples 23-27

[0070] Referring to Table 6, by comparing Example 1 with Examples 23-27, it can be seen that at the beginning of the re-water extraction step, by adding ordinary amylase to the water in which the primary precipitate is soaked, the residual water-insoluble glucan can be decomposed and converted into water-soluble polysaccharides, thereby increasing the release rate of the polysaccharides. Before the end of the extraction, the addition of thermostable amylase can further decompose the newly generated water-insoluble glucan during the re-water extraction process to ensure sufficient extraction of the polysaccharides.

[0071] As the mass ratio of amylase to thermostable amylase continued to decrease, the extraction rate of astragalus polysaccharides showed a trend of first increasing and then decreasing. This may be because as the mass ratio of amylase to thermostable amylase continued to decrease, the content of thermostable amylase continued to increase, which could continuously decompose the water-insoluble glucan produced during the water extraction process and improve the extraction rate of astragalus polysaccharides. When it exceeds a certain range, thermostable amylase will decompose water-soluble polysaccharides while decomposing water-insoluble glucans, which will reduce the polysaccharide extraction rate.

[0072] Examples 28-32 Example 28 Based on the preparation method of Example 1, after the concentrate is mixed with anhydrous ethanol, 15wt% dilute hydrochloric acid is added to form a first mixed solution, and finally the ethanol content in the first mixed solution is 70wt%, and the hydrochloric acid content in the first mixed solution is 5wt%.

[0073] In Examples 29-32, based on the preparation method of Example 28, the contents of ethanol and hydrochloric acid in the first mixed solution were adjusted, and the specific adjustments are shown in Table 7.

[0074] Comparative Examples 3-7 In Comparative Example 3-7, based on the preparation method of Example 28, the contents of ethanol and hydrochloric acid in the first mixed solution were adjusted, and the specific adjustments are shown in Table 7.

[0075] The astragalus polysaccharides of Examples 28-32 and Comparative Examples 3-7 were tested for performance, and the test results are shown in Table 7.

[0076] Table 7 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

[0077] Performance Testing Take healthy mice, 8 mice in each group of the embodiment or comparative example, half of which are male and half are female. Each mouse in the administration group is intraperitoneally injected with the test sample, and each mouse in the blank group is intraperitoneally injected with normal saline. The injections are continued for 7 days, once a day. 24 hours after the last injection, the animals are killed, weighed, and the spleen is weighed to calculate the average spleen index. (Spleen index = spleen weight (mg) / body weight (g), average spleen index = sum of spleen indexes in the group / number of animals in the group) Referring to Table 7, it can be seen from the comparison between Example 1, Examples 28-32 and Comparative Examples 3-7 that, relative to Comparative Examples 3-4, the precipitation ability of the ethanol with a lower content is weakened, resulting in the inability to fully precipitate the effective components such as polysaccharides, thereby reducing the extraction rate of astragalus polysaccharides. In addition, although a higher content of hydrochloric acid can increase the extraction rate of astragalus polysaccharides, the coordination effect with a lower content of ethanol is poor.

[0078] Compared with Comparative Example 5, a higher content of ethanol can improve the extraction rate of astragalus polysaccharides, but it may damage the structure of the polysaccharides, resulting in reduced activity of the polysaccharides. Compared with Comparative Examples 6-7, a higher content of ethanol combined with hydrochloric acid can improve the extraction rate of astragalus polysaccharides, but it will seriously damage the activity of astragalus polysaccharides.

[0079] Embodiment 33 Example 33 Based on the preparation method of Example 1, after the dissolved liquid is mixed with ethanol, 15wt% dilute hydrochloric acid is added to form a second mixed liquid, and finally the content of ethanol in the second mixed liquid is 75wt%, and the content of hydrochloric acid in the second mixed liquid is 5wt%.

[0080] The performance of the astragalus polysaccharide of Example 33 was tested, and the test results are shown in Table 8.

[0081] Table 8 Content and performance test data of hydrochloric acid in the second mixed solution of Example 1, Example 32 and Example 33

[0082] Referring to Table 8, it can be seen from Comparative Example 1, Example 32 and Example 33 that after the dissolved solution is mixed with ethanol, hydrochloric acid is added for a reason similar to the first mixed solution principle. 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, the effect of changing the ionic strength on the polysaccharide precipitation is more significant at this time, and the extraction rate of astragalus polysaccharide can be further improved.

[0083] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be 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: soaking the initial precipitate in water, then heating it to boiling for extraction, filtering and collecting the re-extracted solution, mixing the initial extract and the re-extracted solution to obtain a water-extracted extract; Concentrating under reduced pressure: concentrating the water extract under reduced pressure to obtain a concentrated solution; Primary alcohol precipitation: mixing the concentrated solution with ethanol, standing for stratification, removing the supernatant, and obtaining a primary alcohol precipitate; 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: In the step of re-extraction, amylase is added when the primary precipitate is soaked in water.

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

5.

4. The method for extracting astragalus polysaccharides according to claim 1, characterized in that: In the step of re-extraction with water, the extraction time is 0.8-1.2 hours.

5. The method for extracting astragalus polysaccharides according to claim 4, characterized in that: In the step of re-extraction with water, a thermostable amylase is added 10-20 minutes before the end of the extraction.

6. The method for extracting astragalus polysaccharides according to claim 5, characterized in that: The mass ratio of the astragalus to the heat-resistant amylase is 1000:1-2.

7. The method for extracting astragalus polysaccharides according to claim 5, characterized in that: In the step of re-extraction, amylase is added when the primary precipitate is soaked in water.

8. The method for extracting astragalus polysaccharides according to claim 6, characterized in that: The mass ratio of the amylase to the thermostable amylase is 1:0.3-0.

6.

9. The method for extracting astragalus polysaccharides according to claim 1, characterized in that: In the step of primary alcohol precipitation, after the concentrated solution is mixed with ethanol, hydrochloric acid is added to form a first mixed solution, 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%.

10. 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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