CN102010316A - Method for extracting high-purity frangula emodin from polygonum cuspidatum - Google Patents

Abstract

The invention provides a high-purity extraction method for emodin, the active ingredient in Polygonum cuspidatum. After the medicinal material is pulverized, it is soaked in 45-95% ethanol, and the dosage is 4-9 times the volume of the medicinal material, heated to reflux, the medicinal residue is removed, and the filtrate is concentrated to obtain Emodin Concentrate. Dilute the concentrated solution with water, adjust the pH to acidic, heat for hydrolysis, and stop the hydrolysis reaction when there are no more obvious flocs. The hydrolyzate was obtained by filtration, the product was mixed with water, centrifuged to remove the supernatant, washed with water, and crude emodin was obtained. The crude product was purified by chromatographic column, the eluent was concentrated, and ethanol recrystallized to obtain yellow needle crystals of emodin. The purity of the emodin extracted by the method is higher than 99.0%.

Description

A method for extracting high-purity emodin from Polygonum cuspidatum

technical field

The invention belongs to the field of extraction and purification of active ingredients of natural medicinal materials, and in particular relates to a method for obtaining high-purity emodin by extracting and purifying traditional Chinese medicine Polygonum cuspidatum.

technical background

In our country, there are many kinds of Chinese herbal medicines containing a certain amount of emodin in different degrees in the tuber roots. Among them, the content of emodin is relatively high in domestic Tibetan rhubarb (0.8%) and palmate rhubarb (1%). Recently, Polygonum cuspidatum has been used very frequently in the treatment of viral diseases such as hepatitis in traditional Chinese medicine. Research has found that Polygonum cuspidatum is rich in emodin, and its content is higher than 1.5%. Emodin, as the main effective monomer isolated from Rhubarb, Polygonum, Rhamna and Senna, has antibacterial, antiviral, antiprotozoal, anti-inflammatory, anti-oxidant and scavenging oxygen free radicals, protecting liver and kidney, Treatment of pancreatitis, myocardial protection, neuroprotection and other pharmacological effects. Recent studies have shown that emodin can inhibit tumor cell proliferation, induce apoptosis, prevent tumor cell proliferation, and can effectively inhibit tumor cell uptake of glucose, causing changes in cell membrane-related functions, and ultimately leading to cell apoptosis. Based on the fact that emodin has a wide range of pharmacological effects, it is meaningful to study a method for extracting high-purity emodin from Chinese herbal medicine. According to the extremely rich resources of Chinese herbal medicines in my country, especially Polygonum cuspidatum is not only cheap but also has a high content of emodin, the present invention will provide a method for extracting high-purity emodin from plant Polygonum cuspidatum, which will be used for laboratory research on emodin derivatives. The preparation provides the basis.

Contents of the invention

The object of the present invention is to provide a method for extracting emodin with a purity higher than 99.0% from Polygonum cuspidatum.

Technical scheme of the present invention comprises the steps:

(1) Take Polygonum cuspidatum as the medicinal material and crush it, add ethanol aqueous solution to soak, heat to reflux, remove medicinal residues, and concentrate the filtrate to obtain emodin concentrate. (2) Dilute the concentrated solution with water, adjust the pH to acidity, heat for hydrolysis, and stop the hydrolysis reaction when there are no more obvious flocs. Filtrate to obtain the hydrolyzate, (3) add water to the hydrolyzate, stir evenly, centrifuge to remove the supernatant, and wash with water to obtain crude emodin. (4) The crude emodin was purified by column chromatography, the eluent was concentrated, and recrystallized from ethanol to obtain yellow needle crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

The medicinal material of Polygonum cuspidatum in the step (1) is the decoction pieces of Polygonum cuspidatum sold in pharmacies or the stems of Polygonum cuspidatum from the place of origin. The decoction pieces of Polygonum cuspidatum can be directly soaked in ethanol aqueous solution, and the stems of Polygonum cuspidatum need to be dried, crushed and soaked in aqueous ethanol solution.

In the extraction solvent of the step (1), the aqueous ethanol solution is 45%-95% ethanol, the amount of the aqueous ethanol solution is 4-9 times that of Polygonum cuspidatum medicinal material, soaking time at normal temperature is 4-12 hours, heating and refluxing in a water bath for 2-4 hours, and the extraction times 2-4 times.

The filtrate extracted in the step (1) is concentrated to 1/5-1/10 of the stock solution.

In the step (2), the concentrated solution is diluted with 5-10 times of water, and inorganic acid is added to adjust the pH to 2-3, and the hydrolysis time is 0.5-1.3 hours.

The inorganic acid is hydrochloric acid or sulfuric acid, preferably sulfuric acid.

The amount of water added in the step (3) is 1-2 times that of the hydrolyzed product, and the maximum speed of the centrifuge is 3000 rpm.

The silica gel used in the chromatographic column in the step (4) is 100-200 mesh coarse-pore silica gel, and the ratio of silica gel consumption to crude emodin is 30:1. A mixed reagent of cyclohexane and acetone is used for elution, and a mixed reagent of cyclohexane and acetone is also used as a thin layer developer.

Among the mixed reagents of cyclohexane and acetone, the best separation effect is achieved when the ratio of cyclohexane:acetone is 5:1.

The solvent used in the recrystallization of step (4) is 95% ethanol, the ratio of ethanol dosage to emodin is 20:1, heated to reflux until completely dissolved, and allowed to stand at a temperature of 1-5°C for 8-10 hours.

The instrument used for nuclear magnetic resonance analysis in the step (5) is a BRUKER AV-500 type nuclear magnetic resonance instrument, and about 0.7 mg of the crystallization product is dissolved in 0.5 milliliters of deuterated dimethyl sulfoxide, and the solution is put into a standard sample tube with a diameter of 5 mm In the middle, the temperature is controlled under the condition of 303K, and the hydrogen spectrum, carbon spectrum, DEPT spectrum, COZY spectrum, HSQC spectrum and HMBC spectrum are measured. The test and analysis results are listed in Table 1 and Table 2. NMR proves that this product is emodin .

Purity inspection uses WDL-95 high performance liquid chromatograph in described step (5), test condition: detector UV430nm, stationary phase 5uC18, mobile phase: methanol/water (85/15), chromatographic column: KromasilC18, column length: 25cm, inner diameter: 46mm. As can be seen from the high performance liquid chromatogram of emodin, the absorption peak of emodin appears at the retention time of 9.33 minutes, and the integrated area of the spectrum peak is 99.52%. This shows that the purity of the emodin extracted by this method is higher than 99%.

Table 1. The results of the hydrogen spectrum determination of emodin

The carbon spectrum determination result of table 2 emodin

The present invention will be further described below by way of example.

Detailed ways

Example 1

The method of extracting high-purity emodin from Polygonum cuspidatum, taking 500g of decoction pieces of Polygonum cuspidatum, adding 4000ml of 95% ethanol solution to soak for 4 hours, heating and refluxing for 4 hours, filtering to remove medicinal residues, concentrating the filtrate to 50ml, recovering most of the ethanol, refluxing twice and combining Concentrate. (2) Dilute the concentrated solution with 1500ml of water, then add 30ml of 50% sulfuric acid, adjust the pH to 2, heat the prepared solution for hydrolysis reaction for 1 hour, and continue heating until there are no more obvious flocs after the red flocs appear appear, stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water for 3 times to obtain crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and then use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone is 5:1) to elute. . When the eluate containing emodin flows out from the chromatographic column, start to collect until the eluate does not contain emodin and stop collecting. After the collected eluate is distilled and dried, add 100ml of 95% ethanol and heat to reflux Until it is completely dissolved, let stand at 3°C for 8-10 hours, and filter to obtain yellow needle-like crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Example 2

The method of extracting high-purity emodin from Polygonum cuspidatum, take 500g of decoction pieces of Polygonum cuspidatum, add 4000ml of 50% ethanol solution to soak for 4 hours, heat and reflux in a water bath for 2 hours, filter to remove the medicine residue, concentrate the filtrate to 100ml, recover most of the ethanol, and reflux 4 times Combine the concentrates. (2) Dilute the concentrate with 1200ml of water, then add 30ml of 50% sulfuric acid. Adjust the pH to 2, and heat the prepared solution in a water bath for 1 hour for hydrolysis reaction. After red flocs appear, continue heating until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water for 3 times to obtain crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and then ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and then use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone is 5:1) to elute. . When the eluate containing emodin flows out from the chromatographic column, the collection starts, and the collection stops when emodin is not contained in the eluate, and the collected eluate is distilled and dried. Add 100ml of 95% ethanol, heat to reflux until completely dissolved, let stand at 3°C for 8-10 hours, and filter to obtain yellow needle crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Example 3

The method of extracting high-purity emodin from Polygonum cuspidatum, take 500g of decoction pieces of Polygonum cuspidatum, add 4000ml of 95% ethanol solution to soak for 12 hours, heat and reflux for 2 hours, filter to remove the medicine residue, concentrate the filtrate to 50ml, recover most of the ethanol, and reflux twice to combine Concentrate. (2) Dilute the concentrate with 1500ml of water, then add 30ml of 50% sulfuric acid. Adjust the pH to 2, heat the prepared solution for hydrolysis reaction for 1 hour, after red flocs appear, continue heating until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water for 3 times to obtain crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and then use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone is 5:1) to elute. . When the eluate containing emodin flows out from the chromatographic column, start to collect until the eluate does not contain emodin and stop collecting. After the collected eluate is distilled and dried, add 100ml of 95% ethanol and heat to reflux Until it is completely dissolved, let stand at 3°C for 8-10 hours, and filter to obtain yellow needle-like crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Example 4

The method of extracting high-purity emodin from Polygonum cuspidatum, take 500g of decoction pieces of Polygonum cuspidatum, add 4000ml of 50% ethanol solution to soak for 12 hours, heat and reflux in a water bath for 1 hour, filter to remove medicinal residues, concentrate the filtrate to 50ml, recover most of the ethanol, and reflux 4 times Combine the concentrates. (2) Dilute the concentrate with 1200ml of water, then add 30ml of 50% sulfuric acid. Adjust the pH to 2, heat the prepared solution for hydrolysis reaction for 1 hour, after red flocs appear, continue heating until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water three times to obtain the crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and then use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone is 5:1) to elute. . When the eluate containing emodin flows out from the chromatographic column, the collection starts, and the collection stops when emodin is not contained in the eluate, and the collected eluate is distilled and dried. Add 100ml of 95% ethanol, heat to reflux until completely dissolved, let stand at 3°C for 8-10 hours, and filter to obtain yellow needle-like crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Example 5

The method for extracting high-purity emodin from Polygonum cuspidatum, after drying and crushing 500g of Polygonum cuspidatum stems, adding 4000ml of 95% ethanol solution to soak for 4 hours, heating and refluxing in a water bath for 4 hours, filtering to remove medicinal residues, concentrating the filtrate to 50ml, and recovering most of it Ethanol, reflux twice to combine the concentrate. (2) Dilute the concentrate with 1500ml of water, then add 30ml of 50% sulfuric acid. Adjust the pH to 2, and heat the prepared solution in a water bath for 1 hour for hydrolysis reaction. After red flocs appear, continue heating until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water three times to obtain the crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and then use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone is 5:1) to elute. . When the eluate containing emodin flows out from the chromatographic column, the collection starts, and the collection stops when emodin is not contained in the eluate, and the collected eluate is distilled and dried. Add 100ml of 95% ethanol, heat to reflux until completely dissolved, let stand at 3°C for 8-10 hours, filter to obtain yellow needle-like crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Example 6

The method for extracting high-purity emodin from Polygonum cuspidatum, after drying and pulverizing 500g of Polygonum cuspidatum stems, adding 4000ml of 50% ethanol solution to soak for 4 hours, heating and refluxing in a water bath for 2 hours, filtering to remove medicinal residues, concentrating the filtrate to 100ml, recovering large part of ethanol, refluxed 4 times to combine the concentrate. (2) Dilute the concentrate with 1200ml of water, then add 30ml of 50% sulfuric acid. Adjust the pH to 2, and heat the prepared solution in a water bath for 1 hour of hydrolysis reaction. After red flocs appear, continue heating until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water three times to obtain the crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and then use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone is 5:1) to elute. . When the eluate containing emodin flows out from the chromatographic column, the collection starts, and the collection stops when emodin is not contained in the eluate, and the collected eluate is distilled and dried. Add 100ml of 95% ethanol, heat to reflux until completely dissolved, let stand at 3°C for 8-10 hours, and filter to obtain yellow needle-like crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Example 7

The method for extracting high-purity emodin from Polygonum cuspidatum, after drying and crushing 500g of Polygonum cuspidatum stems, adding 4000ml of 95% ethanol solution to soak for 12 hours, heating and refluxing in a water bath for 2 hours, filtering to remove medicinal residues, concentrating the filtrate to 50ml, and recovering most Ethanol, reflux twice to combine the concentrate. (2) Dilute the concentrate with 1500ml of water, then add 30ml of 50% sulfuric acid. Adjust the pH to 2, and heat the prepared solution in a water bath for 1 hour for hydrolysis reaction. After red flocs appear, continue heating until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water three times to obtain crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and then use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone is 5:1) to elute. . When the eluate containing emodin flows out from the chromatographic column, start to collect until the eluate does not contain emodin and stop collecting. After the collected eluate is distilled and dried, add 100ml of 95% ethanol and heat to reflux Until it is completely dissolved, let stand at 3°C for 8-10 hours, and filter to obtain yellow needle-like crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Example 8

The method for extracting high-purity emodin from Polygonum cuspidatum, after drying and crushing 500g of Polygonum cuspidatum stems, adding 4000ml of 50% ethanol solution to soak for 12 hours, heating and refluxing in a water bath for 1 hour, filtering to remove medicinal residues, concentrating the filtrate to 50ml, and recovering most Ethanol, refluxed 4 times to combine the concentrate. (2) Dilute the concentrate with 1200ml of water, then add 30ml of 50% sulfuric acid. Adjust the pH to 2, and heat the prepared solution for hydrolysis for 1 hour. After red flocs appear, continue heating until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) Add 50ml of water to the hydrolyzate, stir well, centrifuge to remove the supernatant, and wash with water three times to obtain crude emodin. (4) The crude emodin and silica gel were mixed in a ratio of 1:1, and ground after adding a small amount of acetone to mix the crude emodin and silica gel evenly. Weighed 120 g of silica gel and dissolved it in acetone, and poured it into column chromatography. In the process of pouring silica gel, tap the column with a rubber rod continuously to minimize the air bubbles in the column chromatography. Then put the mixture of crude emodin and silica gel into the chromatographic column, and use the mixed reagent of cyclohexane and acetone (cyclohexane: acetone: 5:1) to elute. During the elution process, use a thin-layer plate to spot and track. When the eluate containing emodin flows out from the chromatographic column, the collection starts, and the collection stops when emodin is not contained in the eluate, and the collected eluate is distilled and dried. Add 100ml of 95% ethanol, heat to reflux until completely dissolved, let stand at 3°C for 8-10 hours, and filter to obtain yellow needle crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%.

Without further elaboration, it is believed that one skilled in the art can, using the preceding disclosure, utilize the present invention to its fullest extent. Accordingly, the foregoing specific embodiments are to be understood as illustrative only, and are not intended to limit the scope of the invention in any way.

Claims (10)

1. A method for extracting high-purity emodin from Polygonum cuspidatum, is characterized in that it is realized through the following steps: (1) Take Polygonum cuspidatum, add ethanol aqueous solution to soak, heat to reflux, filter to remove medicinal residues, concentrate the filtrate, recover most of the ethanol, and obtain emodin concentrate. (2) Dilute the concentrated solution with water, and then add a small amount of inorganic acid. Adjust the pH to acidic, heat the prepared solution to carry out the hydrolysis reaction, after the red flocs appear, continue to heat until no more obvious flocs appear, and stop the hydrolysis reaction. The filtrate was removed by filtration to obtain the hydrolyzate. (3) The hydrolyzate was mixed with water, centrifuged to remove the supernatant, and washed three times with water to obtain crude emodin. (4) The crude emodin is passed through a silica gel chromatography column, eluted with an eluent, the collected eluent is distilled under reduced pressure, and recrystallized from ethanol to obtain yellow needle-like crystals. (5) NMR analysis proves that this product is emodin. The nuclear magnetic resonance spectrum shows that there are no obvious miscellaneous peaks except the solvent peak, and the high performance liquid chromatography test result shows that the purity of the emodin extracted by the method is higher than 99.0%. 2. according to the method for extracting high-purity emodin from Polygonum cuspidatum described in patent claim 1, it is characterized in that the knotweed knotweed medicinal material in the step (1) is the knotweed knotweed decoction piece sold in the pharmacy or the stem piece of the knotweed knotweed from the place of origin, and the knotweed knotweed decoction piece can directly add ethanol soaked in water solution, and the stems of Polygonum cuspidatum need to be dried, crushed and then soaked in ethanol water solution. 3. according to the method for extracting high-purity emodin from Polygonum cuspidatum described in patent requirements 1 and 2, ethanol aqueous solution is 45%-95% ethanol in the extraction solvent of described step (1), and the amount of ethanol aqueous solution is 4% of Polygonum cuspidatum medical material -9 times, soaking time at room temperature for 4-12 hours, heating and reflux in water bath for 2-4 hours, extraction times 2-4 times. 4. The method for extracting high-purity emodin from Polygonum cuspidatum according to patent claim 1, characterized in that the filtrate extracted in step (1) is concentrated to 1/5-1/10 of the stock solution. 5. according to the method for extracting high-purity emodin from Polygonum cuspidatum described in patent claim 1, it is characterized in that in step (2), the concentrated solution is diluted with water 5-10 times, adding inorganic acid, adjusting pH to 2-3, The hydrolysis time is 0.5-1.3 hours. 6. According to the patent requirement 5, the inorganic acid is hydrochloric acid or sulfuric acid, and sulfuric acid is preferred. 7. According to the method for extracting high-purity emodin from Polygonum cuspidatum described in patent claim 1, it is characterized in that the addition of water in step (3) is 1-2 times of the hydrolyzate, and the centrifuge speed is up to 3000 rpm . 8. according to the method for extracting high-purity emodin from Polygonum cuspidatum described in patent claim 1, it is characterized in that the silica gel used in the chromatographic column in step (4) is 100-200 mesh coarse-pore silica gel, the ratio of silica gel consumption and emodin crude product It is 30:1. A mixed reagent of cyclohexane and acetone is used for elution, and a mixed reagent of cyclohexane and acetone is also used as a thin layer developer. 9. According to the mixed reagent of cyclohexane and acetone described in patent claim 8, the best separation effect is achieved when cyclohexane: acetone is 5:1. 10. according to the method for extracting high-purity emodin from Polygonum cuspidatum described in patent claim 1, it is characterized in that used solvent is 95% ethanol in the step (4) recrystallization, and its consumption and emodin ratio are 20: 1, at temperature Stand at 1-5°C for 8-10 hours to crystallize.