Purification method of silymarin and preparation method of high-purity silibinin

Abstract

The invention provides a purification method of silymarin and a preparation method of high-purity silybin, and relates to the technical field of silybin. According to the method, one of the ethanol water solution, the isopropanol water solution and the ethanol-ethyl acetate solution is used as the purification solvent for purifying the silymarin, so that a silybin crude product with relatively high purity can be obtained. And dissolving the silybin crude product with hot isopropanol, concentrating, adding hot water, and precipitating to separate out the silybin, thereby obtaining the high-purity silybin with the purity not lower than 99%. The method is simple and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of silybin technology, and relates to a method for purifying silybin and a method for preparing high-purity silybin. Background Technology

[0002] Silymarin belongs to the flavonoid lignan class of compounds and is composed of two diastereomers, silymarin A and silymarin B. It has a variety of biological activities, most notably liver protection and free radical scavenging.

[0003] Purification of silymarin is an important method for obtaining silybin. Silymarin contains approximately 30% silybin, but also contains various isomers such as silymarinine, silybinin, and isosilybin, all with similar physicochemical properties. Therefore, the purification process for silybin from silymarin places high demands on the process. Chinese Patent CN101260105A discloses a method for extracting silybin from silymarin, comprising the following steps: 1) using 70-80% ethanol as the extraction solvent, refluxing, concentrating, and re-extracting silymarin to obtain crude silybin; 2) using 95% ethanol as the extraction solvent, refluxing, concentrating, and re-extracting the crude silybin from step 1) to obtain crude silybin; 3) decolorizing and purifying the crude silybin from step 2) with anhydrous ethanol. However, this method is relatively complex, requiring multiple concentration and extraction cycles, and the purity of the obtained crude silybin is not disclosed.

[0004] Therefore, the existing process for extracting silybin from silymarin needs to be improved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for purifying silymarin.

[0006] On the other hand, the present invention also proposes a method for preparing high-purity silymarin.

[0007] The technical solution of the present invention is as follows:

[0008] A method for purifying silymarin involves adding silymarin to a purification solvent, stirring for 20-80 minutes, filtering, and drying the filter cake at a temperature not exceeding 100°C to obtain crude silymarin. The purification solvent is selected from one of the following: aqueous ethanol solution, aqueous isopropanol solution, and ethanol-ethyl acetate solution; When the purification solvent is selected from an aqueous ethanol solution, the weight-to-volume ratio of silymarin to the aqueous ethanol solution is 1:2-4 g / ml, and the volume content of ethanol in the aqueous ethanol solution is 50-70%. When the purification solvent is selected from an isopropanol aqueous solution, the weight-to-volume ratio of silymarin to the isopropanol aqueous solution is 1:8-13 g / ml, and the volume content of isopropanol in the isopropanol aqueous solution is 80±5%. When the purification solvent is selected from an ethanol-ethyl acetate solution, the weight-to-volume ratio of silymarin to the ethanol-ethyl acetate solution is 1:2-5 g / ml, and the volume content of ethanol in the ethanol-ethyl acetate solution is 15±5%.

[0009] Preferably, the weight-to-volume ratio of silymarin to the ethanol aqueous solution is 1:2-2.5 g / ml; The volume content of ethanol in the aqueous ethanol solution is 60%.

[0010] Preferably, the weight-to-volume ratio of silymarin to the isopropanol aqueous solution is 1:10 g / ml; The isopropanol aqueous solution contains 80% isopropanol by volume.

[0011] Preferably, the weight-to-volume ratio of silymarin to the ethanol-ethyl acetate solution is 1:3 g / ml; The volume content of ethanol in the ethanol-ethyl acetate solution is 15%.

[0012] Preferably, the purity of the crude silymarin is not less than 80%.

[0013] More preferably, when the purification solvent is selected from the isopropanol aqueous solution or the ethanol-ethyl acetate solution, the purity of the crude silymarin is not less than 95%.

[0014] A method for preparing high-purity silybin: crude silybin is added to isopropanol, stirred and heated to 85-90℃ and dissolved, the volume of the solution is concentrated to 1 / 3-1 / 2, hot water at 90±2℃ is added, a solid is precipitated, the temperature is cooled to room temperature to continue crystallization, the solid is separated, dried, and high-purity silybin is obtained. The purity of the high-purity silymarin is not less than 99%; The crude silymarin is obtained by the purification method described in any of the above embodiments; Alternatively, the crude silymarin may be a commercially available crude silymarin with a purity of not less than 90%.

[0015] Preferably, the weight-to-volume ratio of crude silymarin to isopropanol is 1:15-25 g / ml.

[0016] Preferably, the volume ratio of isopropanol to hot water is 1.5-3:1.

[0017] Preferably, the purity of the high-purity silymarin is not less than 99.9%.

[0018] The beneficial effects of this invention are: (1) The present invention can use three mixed solvents to purify silymarin, which combines the characteristics of different solvents. The process is simple, the purification efficiency is high and the effect is good, and crude silymarin with high silymarin content can be obtained.

[0019] (2) For the purification of crude silymarin, this invention uses a combination of isopropanol and water as the purification solvent. Isopropanol is low in toxicity and highly efficient, and has a moderate solubility for silymarin. The solubility of silymarin is further reduced by adding hot water, and then purified to obtain high-purity silymarin with a purity of not less than 99%, or even not less than 99.9%, or reaching 99.99%. The preparation method of high-purity silymarin in this invention is simple, the reagents are inexpensive and readily available, it is environmentally friendly, and suitable for industrial production. Attached Figure Description

[0020] Figure 1 The image shows the HPLC chromatogram of high-purity silymarin obtained in Example 11. Detailed Implementation

[0021] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0022] On the one hand, the present invention proposes a method for purifying silymarin, which involves adding silymarin to a purification solvent, stirring for 20-80 minutes, filtering, and drying the filter cake at a temperature not exceeding 100°C to obtain crude silymarin. The purification solvent is selected from one of the following: aqueous ethanol solution, aqueous isopropanol solution, and ethanol-ethyl acetate solution; When the purification solvent is selected as an aqueous ethanol solution, the weight-to-volume ratio of silymarin to the aqueous ethanol solution is 1:2-4 g / ml, and the volume content of ethanol in the aqueous ethanol solution is 50-70%. When the purification solvent is selected as isopropanol aqueous solution, the weight-to-volume ratio of silymarin to isopropanol aqueous solution is 1:8-13 g / ml, and the volume content of isopropanol in the isopropanol aqueous solution is 80±5%. When the purification solvent is selected as ethanol-ethyl acetate solution, the weight-to-volume ratio of silymarin to ethanol-ethyl acetate solution is 1:2-5 g / ml, and the volume content of ethanol in ethanol-ethyl acetate solution is 15±5%.

[0023] This invention uses the three purification solvents mentioned above to purify silymarin. It only requires stirring and filtration at room temperature (5-30℃), making the method simple, suitable for industrial operation, and yielding a high-purity crude silymarin. Different solvents have different solubilities for silymarin; for example, methanol has higher solubility than ethanol, ethanol is higher than isopropanol, isopropanol is higher than n-butanol, and n-butanol is higher than water. The three purification solvents of this invention combine the different solubilities of different solvent components in each solvent for the various components of silymarin. For example, ethanol has good solubility for silymarin in aqueous ethanol solution, while water has poor solubility. By adjusting the volume content of ethanol in the aqueous ethanol solution, the different solubilities of the purification solvent for the various components of silymarin are adjusted, thus allowing for the acquisition of a high-purity crude silymarin through simple stirring and filtration.

[0024] In this invention, the unit of weight-volume ratio is g / ml. For example, a weight-volume ratio of 1:2-3 g / ml means the ratio of 1g in weight to 2-3ml in volume. Similarly, it can be converted to the ratio of 1kg in weight to 2-3L in volume.

[0025] For example, the weight-to-volume ratio of silymarin to an ethanol aqueous solution can be 1:2 g / ml, 1:2.5 g / ml, 1:3 g / ml, 1:3.5 g / ml, 1:4 g / ml, etc., and the volume content of ethanol in the ethanol aqueous solution can be 50%, 60%, 70%, etc.; for example, the weight-to-volume ratio of silymarin to an isopropanol aqueous solution can be 1:8 g / ml, 1:9 g / ml, 1:10 g / ml, 1:11 g / ml, 1:12 g / ml, 1:13 g / ml, etc., and the volume content of isopropanol in the isopropanol aqueous solution can be 75%, 80%, 85%, etc.; for example, the weight-to-volume ratio of silymarin to an ethanol-ethyl acetate solution can be 1:2 g / ml, 1:3 g / ml, 1:4 g / ml, 1:5 g / ml, etc., and the volume content of ethanol in the ethanol-ethyl acetate solution can be 10%, 15%, 20%, etc.

[0026] For the drying of the filter cake, after the filter cake is dried to initial dryness, it can be crushed into small pieces and then dried further, and then crushed again until the content of the purified solvent does not exceed 0.5 wt%.

[0027] In some embodiments, the weight-to-volume ratio of silymarin to the aqueous ethanol solution is 1:2-2.5 g / ml; The volume content of ethanol in the aqueous ethanol solution is 60%.

[0028] In some embodiments, the weight-to-volume ratio of silymarin to isopropanol aqueous solution is 1:10 g / ml; The volume content of isopropanol in the aqueous solution is 80%.

[0029] In some embodiments, the weight-to-volume ratio of silymarin to the ethanol-ethyl acetate solution is 1:3 g / ml; The volume content of ethanol in the ethanol-ethyl acetate solution is 15%.

[0030] In some embodiments, the purity of crude silybin is not less than 80%. For example, the purity of the obtained crude silybin can be 80%, 82%, 85%, 87%, 90%, 92%, 95%, etc. Further, the purity of crude silybin is not less than 90%.

[0031] In some embodiments, when the purification solvent is selected from an aqueous isopropanol solution or an ethanol-ethyl acetate solution, the purity of the crude silymarin is not less than 95%. An unexpected discovery of this invention is that using an aqueous isopropanol solution or an ethanol-ethyl acetate solution as the purification solvent yields a higher purity of the crude silymarin, reaching 95% or higher, such as 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, etc.

[0032] On the other hand, the present invention also proposes a method for preparing high-purity silybin, wherein crude silybin is added to isopropanol, stirred and heated to 85-90°C and dissolved, the volume of the solution is concentrated to 1 / 3-1 / 2, hot water at 90±2°C is added, solid is precipitated, the temperature is cooled to room temperature to continue crystallization, the solid is separated, dried, and high-purity silybin is obtained. The purity of high-purity silymarin is not less than 99%; The crude silymarin was obtained by the purification method described in any of the above embodiments; Alternatively, crude silymarin may be commercially available crude silymarin with a purity of not less than 90%.

[0033] As analyzed above, the solubility of silybin in alcohol solvents, from highest to lowest, is methanol, ethanol, isopropanol, and n-butanol. This invention discovers that dissolving crude silybin in isopropanol at high temperatures (even reaching near boiling point), followed by decolorization and concentration (the volume of the concentrate is 1 / 3 to 1 / 2 of the filtrate volume), and then adding hot water, reduces the solubility of silybin, causing it to precipitate. Other impurities remain largely in the isopropanol aqueous solution, thus obtaining high-purity silybin with a purity of 99% or higher, even 99.9%. The above method for preparing high-purity silybin can also be used to prepare silybin with a purity of 99.99% or higher.

[0034] In this invention, crude silybin can be obtained by purifying silybin as described above. Silybin is purified to obtain crude silybin, and the crude silybin is further purified to obtain high-purity silybin. Crude silybin, as a raw material for preparing high-purity silybin, can also be obtained directly from the market, such as commercially available crude silybin with a purity of approximately 90-95%.

[0035] In some embodiments, the weight-to-volume ratio of crude silybin to isopropanol is 1:15-25 g / ml. For example, the weight-to-volume ratio of crude silybin to isopropanol can be 1:15 g / ml, 1:16 g / ml, 1:17 g / ml, 1:18 g / ml, 1:19 g / ml, 1:20 g / ml, 1:21 g / ml, 1:22 g / ml, 1:23 g / ml, 1:24 g / ml, 1:25 g / ml, etc. Further, the weight-to-volume ratio of crude silybin to isopropanol can be 1:18-25 g / ml, for example, 18 ml of isopropanol is added to 1 g of crude silybin, or 25 ml of isopropanol is added to 1 g of crude silybin.

[0036] In some embodiments, the volume ratio of isopropanol to hot water is 1.5-3:1. For example, the volume ratio of isopropanol to hot water can be 1.5:1, 2:1, 2.5:1, 3:1, etc.

[0037] When the solution formed by dissolving crude silymarin in isopropanol is dark in color (mainly because the purity of crude silymarin is not high enough), activated carbon can be added for decolorization. The decolorization should be carried out at a constant temperature, and the filtrate after decolorization should be concentrated.

[0038] In some embodiments, the purity of high-purity silymarin is not less than 99.9%.

[0039] The high-purity silymarin of the present invention can be used to prepare silymarin meglumine salt.

[0040] The technical solution of the present invention will be further described and illustrated below with reference to various embodiments. Unless otherwise specified, the parts mentioned in the following embodiments are parts by weight.

[0041] Examples 1-5: Preparation of crude silymarin from silymarin purification. Example 1 2.5 kg of silymarin (obtained commercially, silybin content 32%) was weighed and added in four batches to 5 L of 60% ethanol aqueous solution (weight-to-volume ratio of silymarin to ethanol aqueous solution 1:2 g / ml). The mixture was stirred at 7.5℃ for 45 min, filtered, and the filter cake was dried at 90℃ until the ethanol content did not exceed 0.5 wt%, yielding a light yellow crude silybin product with a yield of 26.3%. The silybin content in the crude silymarin product was determined by high performance liquid chromatography (HPLC) according to the Chinese Pharmacopoeia, and the silybin content was found to be 91.85%.

[0042] High performance liquid chromatography (HPLC) detection conditions: UV detector, wavelength 288 nm, flow rate 1.0 ml / min, column temperature 30 ℃, injection volume 10 μl, mobile phase methanol-water-glacial acetic acid (42:58:5), chromatographic column Inertsil ODS-3 (4.6 mm × 250 mm, 5 μm); Solution preparation Blank solution: i.e., solvent methanol.

[0043] Test solution: Accurately weigh 25 mg of sample, place it in a 25 ml volumetric flask, add methanol and sonicate for 20 min, dilute to the mark with methanol, and shake well to obtain the test solution.

[0044] Control solution: Transfer 2.5 ml of the test solution to a 100 ml volumetric flask, dilute to the mark with methanol, and shake well.

[0045] Accurately pipette 10 μl each of the reference solution and the test solution into the liquid chromatograph. Record the chromatogram of the test solution up to twice the retention time of the main component peak, and then determine the concentration. Calculate the silymarin content by summing the areas of the two silymarin peaks.

[0046] Example 2 5 kg of silymarin was weighed and added in 5 batches to 12.5 L of 60% ethanol aqueous solution (volume ratio 1:2.5 g / ml). The mixture was stirred at 11 °C for 30 min, filtered, and the filter cake was dried at 100 °C until the ethanol content did not exceed 0.5 wt%, yielding a light yellow crude silymarin product with a yield of 24.5%. Testing showed that the silymarin content in the crude silymarin product was 93.03%.

[0047] Example 3 5 kg of silymarin was weighed and added in 5 batches to 17.5 L of 60% ethanol aqueous solution (volume ratio 1:3.5 g / ml). The mixture was stirred at 20°C for 60 min, filtered, and the filter cake was dried at 100°C until the ethanol content did not exceed 0.5 wt%, yielding a light yellow crude silymarin product with a yield of 25.2%. Testing showed that the silymarin content in the crude silymarin product was 92.01%.

[0048] Example 4 2 kg of silymarin was weighed and added in four batches to 20 L of isopropanol aqueous solution with a volume content of 80% (1:10 g / ml). The mixture was stirred at 15 °C for 50 min, filtered, and the filter cake was dried at 100 °C until the isopropanol content did not exceed 0.5 wt%, yielding a light yellow crude silymarin product with a yield of 20.1%. Testing showed that the silymarin content in the crude silymarin product was 97.82%.

[0049] Example 5 2 kg of silymarin was weighed and added in four batches to 6 L of an ethanol-ethyl acetate solution with a volume content of 15% (15% ethanol). The weight-to-volume ratio of silymarin to the ethanol-ethyl acetate solution was 1:3 g / ml. The mixture was stirred at 18°C ​​for 40 min, filtered, and the filter cake was dried at 100°C until the content of both ethanol and ethyl acetate did not exceed 0.5 wt%, yielding a pale yellow crude silymarin product with a yield of 19.8%. Testing showed that the silymarin content in the obtained crude silymarin product was 97.55%.

[0050] Therefore, as can be seen from Examples 1-5, the present invention uses three purification solvents, and through dissolution, filtration and drying, the process is simple and can obtain crude silymarin with high purity.

[0051] Examples 6-12: Preparation of high-purity silymarin from crude silymarin Example 6 3 kg of crude silymarin obtained in Example 1 was added to 54 L of isopropanol (weight-to-volume ratio 1:18 g / ml), stirred, and heated to 85-90 °C to dissolve, yielding a clear reddish-brown solution. At a constant temperature, 0.9 kg of activated carbon was added to the solution for decolorization for 30 min. The activated carbon was removed by filtration, and another 0.9 kg of activated carbon was added for further decolorization for 30 min. The activated carbon was then removed by filtration, and the resulting filtrate was concentrated to 27 L (volume concentration 1 / 2). Then, 27 L of 90 °C hot water was slowly added, resulting in the precipitation of a large amount of solid in the filtrate. After the hot water was added, the filtrate was cooled to 10 °C, and crystallization continued for 3 h. The solid was obtained by suction filtration and vacuum drying at 80-85 °C for 3 h to obtain pale yellow to off-white high-purity silymarin, with a yield of 60%. The high-performance liquid chromatography method described in Example 1 was used to detect silybin. The content of silybin in the high-purity silybin was found to be 99.2%, the content of isosilybin A was 0.4%, and the content of isosilybin B was 0.17%.

[0052] Example 7 Following the method of Example 6, the crude silybin obtained in Example 1 was replaced with the crude silybin obtained in Example 2. The remaining steps remained unchanged. The obtained high-purity silybin contained 99.7% silybin, 0.25% isosilybin A, and 0.11% isosilybin B.

[0053] Example 8 3 kg of crude silybin obtained in Example 3 was added to 54 L of isopropanol (weight-to-volume ratio 1:18 g / ml), stirred, and heated to 85-90 °C to dissolve, yielding a clear reddish-brown solution. At a constant temperature, 0.9 kg of activated carbon was added to the solution for decolorization for 30 min. The activated carbon was removed by filtration, and the resulting filtrate was concentrated to 18 L (volume concentration of 1 / 3). Then, 18 L of 90 °C hot water was slowly added, resulting in the precipitation of a large amount of solid in the filtrate. After the hot water was completely added, the filtrate was cooled to 10 °C, and crystallization continued for 3 h. The solid was obtained by suction filtration and vacuum drying at 80-85 °C for 3 h, yielding a pale yellow to off-white high-purity silybin with a yield of 63.3%. The content of silybin in the high-purity silybin was measured to be 99.4%, the content of isosilybin A was 0.36%, and the content of isosilybin B was 0.13%.

[0054] Example 9 Following the method of Example 8, the crude silybin obtained in Example 3 was replaced with commercially available crude silybin (silybin content 92.3%). The remaining steps remained unchanged. The obtained high-purity silybin contained 99.5% silybin, 0.29% isosilybin A, and 0.14% isosilybin B.

[0055] Comparative Example 1 Take 3 kg of commercially available crude silybin from Example 9, add 54 L of anhydrous ethanol, heat to a gentle boil and dissolve, add 0.9 kg of activated carbon for decolorization for 30 min, filter to remove activated carbon, concentrate the obtained filtrate to 18 L (volume concentration 1 / 3), then slowly add 18 L of 75°C hot water. The amount of solid precipitated in the filtrate is small. Cool the filtrate to 10°C and continue crystallization for 3 h. Filter to obtain the solid, dry under vacuum at 80-85°C for 3 h to obtain light yellow to off-white high-purity silybin, with a yield of 30.7%. The content of silybin in the high-purity silybin was measured to be 94.3%, and the combined content of isosilybin A and isosilybin B was 4.9%.

[0056] Example 10 1 kg of crude silybin obtained in Example 4 was added to 25 L of isopropanol (weight-to-volume ratio 1:18 g / ml), stirred, and heated to 85-90 °C to dissolve, yielding a clear yellow solution. The solution was concentrated to 9 L, and then 13.5 L of 90 °C hot water was slowly added, resulting in the precipitation of a large amount of solid in the filtrate. After the hot water was completely added, the filtrate was cooled to 10 °C, and crystallization continued for 3 hours. The solid was obtained by suction filtration and vacuum drying at 80-85 °C for 3 hours, yielding a pale yellow to off-white high-purity silybin with a yield of 86%. The silybin content in the high-purity silybin was measured to be 99.94%, and the maximum content of a single impurity was 0.055%.

[0057] Example 11 Following the method of Example 10, the crude silybin obtained in Example 4 was replaced with the crude silybin obtained in Example 5. The remaining steps remained unchanged. The obtained high-purity silybin contained 99.9% silybin and the maximum single impurity content was 0.099%. The HPLC chromatogram is attached. Figure 1 As shown.

[0058] Example 12 Following the method of Example 10, the crude silybin obtained in Example 4 was replaced with the high-purity silybin obtained in Example 6. The remaining steps remained unchanged. The obtained high-purity silybin contained 99.995% silybin and had a maximum single impurity content of 0.003%.

[0059] Therefore, as can be seen from Examples 6-12, the present invention uses isopropanol as a solvent to dissolve crude silymarin at high temperature, and after concentration, precipitation with heated water and crystallization (or decolorization with activated carbon before concentration), the process is simple and can obtain high-purity silymarin.

[0060] As described above, the basic principles, main features, and advantages of the present invention have been shown and described. Those skilled in the art should understand that the present invention is not limited to the above embodiments, which are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent changes and modifications made in accordance with the scope of the patent and the description should still fall within the scope of the present invention. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for purifying silymarin, characterized in that, Silymarin was added to the purification solvent, stirred for 20-80 minutes, filtered, and the filter cake was dried at no more than 100°C to obtain crude silymarin. The purification solvent is selected from one of the following: aqueous ethanol solution, aqueous isopropanol solution, and ethanol-ethyl acetate solution; When the purification solvent is selected from an aqueous ethanol solution, the weight-to-volume ratio of silymarin to the aqueous ethanol solution is 1:2-4 g / ml, and the volume content of ethanol in the aqueous ethanol solution is 50-70%. When the purification solvent is selected from an isopropanol aqueous solution, the weight-to-volume ratio of silymarin to the isopropanol aqueous solution is 1:8-13 g / ml, and the volume content of isopropanol in the isopropanol aqueous solution is 80±5%. When the purification solvent is selected from an ethanol-ethyl acetate solution, the weight-to-volume ratio of silymarin to the ethanol-ethyl acetate solution is 1:2-5 g / ml, and the volume content of ethanol in the ethanol-ethyl acetate solution is 15±5%.

2. The method for purifying silymarin according to claim 1, characterized in that, The weight-to-volume ratio of silymarin to the ethanol aqueous solution is 1:2-2.5 g / ml; The volume content of ethanol in the aqueous ethanol solution is 60%.

3. The method for purifying silymarin according to claim 1, characterized in that, The weight-to-volume ratio of silymarin to the isopropanol aqueous solution is 1:10 g / ml; The isopropanol aqueous solution contains 80% isopropanol by volume.

4. The method for purifying silymarin according to claim 1, characterized in that, The weight-to-volume ratio of silymarin to the ethanol-ethyl acetate solution is 1:3 g / ml; The volume content of ethanol in the ethanol-ethyl acetate solution is 15%.

5. The method for purifying silymarin according to claim 1, characterized in that, The purity of the crude silymarin is not less than 80%.

6. The method for purifying silymarin according to claim 5, characterized in that, When the purification solvent is selected from the isopropanol aqueous solution or the ethanol-ethyl acetate solution, the purity of the crude silymarin is not less than 95%.

7. A method for preparing high-purity silymarin, characterized in that, Crude silymarin was added to isopropanol, stirred and heated to 85-90℃ to dissolve, the volume of the solution was concentrated to 1 / 3-1 / 2, hot water at 90±2℃ was added, the solid precipitated, the temperature was cooled to room temperature to continue crystallization, the solid was separated, dried, and high-purity silymarin was obtained. The purity of the high-purity silymarin is not less than 99%; The crude silymarin is obtained by the purification method described in any one of claims 1-6; Alternatively, the crude silymarin may be a commercially available crude silymarin with a purity of not less than 90%.

8. The method for preparing high-purity silymarin according to claim 7, characterized in that, The weight-to-volume ratio of crude silymarin to isopropanol is 1:15-25 g / ml.

9. The method for preparing high-purity silymarin according to claim 7, characterized in that, The volume ratio of isopropanol to hot water is 1.5-3:

1.

10. The method for preparing high-purity silymarin according to claim 7, characterized in that, The purity of the high-purity silymarin is not less than 99.9%.

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