Method for extracting reserpine from rauvolfia verticillate under assistance of microwaves

Abstract

The invention relates to a method for extracting and separating natural substances, in particular to a method for extracting reserpine from rauvolfia verticillate under the assistance of microwaves, which comprises the following steps: S10, an extraction step: crushing rauvolfia verticillate root bark, mixing with an acidic ethanol solution, and carrying out microwave extraction; s20, coarse crystallization: centrifuging the extracting solution, concentrating, performing acid precipitation, adding methanol for reflux, and standing to obtain a crude product; and S30, recrystallization: pulping the crude product with ethanol, recrystallizing with an acetone-ethanol system, and drying to obtain a finished product. The method disclosed by the invention is environment-friendly and high in extraction efficiency, the time of the extraction process is greatly shortened, and the use amount of a toxic organic solvent is reduced; meanwhile, ethanol is used for replacing an organic solvent in the process, so that the process is simple and convenient, the operation is simple, the toxicity is low, the safety is high, organic solvent recovery is facilitated, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to a method for extracting and separating natural substances, and in particular to a method for extracting reserpine from Rauwolfia ovata by utilizing microwaves. Background Art

[0002] Reserpine is called Reserpine in English and its chemical formula is C 33 H 40 N2O9, CAS No.: 50-55-5, structural formula is as follows:

[0003]

[0004] Reserpine is an important indole alkaloid, mainly found in various plants of the genus Rauwolfia, with a maximum content of 1% in Rauwolfia emetica. Reserpine has the effects of lowering blood pressure and slowing heart rate, with a slow, mild and long-lasting effect. Due to its significant antihypertensive effect, reserpine is widely used as an antihypertensive drug or a health product formula for blood pressure reduction needs. At present, there is a lot of research on reserpine at home and abroad, and its production process is relatively mature.

[0005] The currently disclosed methods for extracting reserpine from Rauwolfia wood are:

[0006] In the patent publication CN101016297A, the process is to extract the powder of Rauwolfia with ethanol, concentrate the extract and pass it through a macroporous resin column, heat and concentrate the eluent to obtain solid alkaloids, dissolve it with acetone and add a chloroform-petroleum ether mixed solution to precipitate colloid, concentrate the supernatant and add ethyl acetate and methanol to obtain crude crystals, and then recrystallize with acetone and methanol to obtain the finished product of reserpine. The disadvantages of this process are that the process is complicated and has many steps, the extraction method takes a long time and the extraction efficiency is low, and the types of toxic organic solvents used in the purification and refining process are many and the amount used is large, which is not friendly to the environment and has the risk of endangering human health.

[0007] In the patent publication CN101475570A, the process is to extract the Rauwolfia powder by percolation with acid water, extract the extract with dichloroethane for multiple times after concentration, obtain crude reserpine crystals after concentration, dissolve the crude crystals with dichloroethane, filter and concentrate, and then use ethanol to crystallize to obtain the finished reserpine product. The disadvantage of this process is that the acid water percolation extraction method has the problem of poor leaching effect of effective components due to material blockage or enhanced material adsorption during the extraction process, thereby reducing the extraction efficiency.

[0008] In the patent publication CN104513236A, the process is to subject the powder of Rauwolfia to supercritical extraction, then dissolve it with an acid solution, pass the filtrate through a macroporous resin column, concentrate the eluate to dryness and then dissolve it with acetone, then add methanol for crystallization to obtain crude crystals, recrystallize the crude crystals with acetone-methanol, and dry them to obtain the finished product of reserpine. The disadvantage of this process is that the supercritical extraction technology needs to consume a lot of energy to maintain the supercritical state, the energy consumption is high, the technical requirements are high, and the investment is large.

[0009] In the patent publication CN104072494A, the process is to add an acidic ethanol solution and cellulase to the Rauwolfia powder, extract it in a dual-frequency ultrasonic extractor, inactivate the enzymatic solution, centrifuge it and elute it on a macroporous resin column, concentrate the eluate and add ethyl acetate-petroleum ether to precipitate alkaloids, and finally recrystallize it twice with ethyl acetate to obtain the finished product of reserpine. The disadvantages of this process are high equipment cost, the problem of easy inactivation of bioactive macromolecules and the influence of organic solvents on enzyme activity, and high requirements for operating conditions. Summary of the invention

[0010] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for extracting reserpine from Rauwolfia ovata using microwaves. The method is environmentally friendly and has high extraction efficiency, greatly reducing the time of the extraction process and the amount of toxic organic solvents used; at the same time, ethanol is used to replace the organic solvent in the above process, which not only has a simple process and simple operation, low toxicity and high safety, but also is conducive to the recovery of organic solvents and reduces production costs.

[0011] The purpose of the present invention is achieved by the following technical solutions:

[0012] The first aspect of the present invention provides a method for extracting reserpine from Rauwolfia ovata using microwaves, comprising the following steps:

[0013] S10, extraction step: crushing the root bark of Rauwolfia ovata and mixing it with an acidic ethanol solution, and performing microwave extraction;

[0014] S20, crude crystallization step: centrifuging and concentrating the extract, followed by acid precipitation, adding methanol to reflux, and standing to obtain a crude product;

[0015] S30, recrystallization step: the crude product is slurried with ethanol, then recrystallized through an acetone-ethanol system, and dried to obtain a finished product.

[0016] In the first aspect of the present invention, as an optional embodiment, a method for extracting reserpine from Rauwolfia ovata using microwaves comprises the following steps:

[0017] S10, extraction step: grind and sieve the root bark of Rauwolfia ovata, add ethanol solution, mix thoroughly, adjust the pH to acidic, perform microwave extraction in a microwave extractor, repeat the extraction 2-4 times, and combine the extracts;

[0018] S20, crude crystallization step: centrifuging the extract, filtering, and obtaining a first filtrate; concentrating the first filtrate until a fixed precipitate is present, adding glacial acetic acid, adjusting the pH to be acidic, ultrasonicating for 5-10 minutes, standing for 1.5-2.5 hours, filtering and discarding insoluble matter, and obtaining a second filtrate; adding methanol to the second filtrate, refluxing, filtering, and obtaining a third filtrate; concentrating the third filtrate to one third of its original volume, standing overnight, and obtaining a concentrated solution; filtering the concentrated solution to obtain a solid; washing the solid with ethyl acetate, and drying in a drying oven to obtain a crude product;

[0019] S30, recrystallization step: take the crude product, add ethanol solution to pulp for 25-35 minutes, filter and add acetone, adjust the pH to acidic, filter and discard insoluble matter, concentrate and then add acetone and ethanol respectively, stir and crystallize at low temperature, filter and wash with anhydrous ethanol, and dry to obtain the finished product.

[0020] In the first aspect of the present invention, as an optional embodiment, in S10, in the extraction step, an ethanol solution is added at a solid-liquid ratio of 1:10, wherein the mass percentage concentration of the ethanol solution is 70-90%.

[0021] In the first aspect of the present invention, as an optional embodiment, in S10, the extraction step, the pH is adjusted to a range of 1-3.

[0022] In the first aspect of the present invention, as an optional embodiment, in S10, the extraction step, the power of the microwave extractor is 500W, the extraction is repeated 3 times, the single extraction time is 5 minutes, and the extraction temperature is 50-80°C.

[0023] In the first aspect of the present invention, as an optional embodiment, in S20, the crude crystallization step, the reflux condition is reflux at 50-65° C. for 30 min.

[0024] In the first aspect of the present invention, as an optional embodiment, in S20, the crude crystallization step, 3-5 times the volume of methanol is added to the second filtrate for reflux, and the process is repeated twice.

[0025] In the first aspect of the present invention, as an optional embodiment, in S20, the crude crystallization step, the amount of glacial acetic acid added is equal to the volume of the filtrate, and the pH is adjusted to 2.2-3.0.

[0026] In the first aspect of the present invention, as an optional embodiment, in S30, the recrystallization step, the pH is adjusted to a range of 2-3.

[0027] In the first aspect of the present invention, as an optional embodiment, in S30, the recrystallization step, the condition of low-temperature crystallization is stirring crystallization at -10°C for 3 hours.

[0028] In the S10 extraction step, the extraction temperature is less than 50°C, the extraction is not sufficient, and the ethanol volatilizes at a temperature greater than 80°C, the solvent loss is serious, and the extraction rate is greatly reduced; in the S10 extraction step, the ethanol solution has a mass percentage concentration of 70-90%, and the optimal concentration is 85%. If the concentration is lower than 70%, the solvent cannot dissolve reserpine in the material well, and if the concentration is higher than 90%, the cell structure of the Rauwolfia tree may be destroyed, causing the polysaccharides, proteins and other components in the cell structure of the Rauwolfia tree to dissolve, increasing the difficulty of separation and purification; in the S20, crude crystallization step and S30, In the recrystallization step, acid is used to adjust the pH to 1-3 or 2-3, so that more reserpine in Rauwolfia can be dissolved in the solution, thereby better separating reserpine and other substances. Excessive acid or pH greater than 3 will reduce the solubility of reserpine and reduce the extraction rate of reserpine. In S20, the crude crystallization step, the temperature range of methanol reflux is 50-65°C. If the temperature is less than 50°C, the impurities soluble in acid and methanol in the extract cannot be well dissolved in methanol, and the separation is incomplete. If the temperature is greater than 65°C, methanol is easily volatile, which is not conducive to the separation and purification of reserpine.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention uses an acidic ethanol solution as an extraction solvent, and through microwave-assisted extraction, the extract is centrifuged, concentrated, and then precipitated with glacial acetic acid, methanol is added to reflux, and crude crystals are allowed to stand overnight to obtain crude crystals, and the crude crystals are pulped with ethanol and then recrystallized with acetone-ethanol, and finally dried to obtain a method for the finished product of reserpine. The present invention combines acidic ethanol solution extraction with microwave-assisted extraction, and can penetrate the cell wall of Rauwolfia and cause cell rupture, so that acid water can be infiltrated into the material in a short time, accelerate the solvation and dissolution release of the components to be extracted, significantly improve the extraction efficiency of reserpine, and significantly shorten the microwave extraction time. Using an acidic ethanol solution as an extraction solvent is more environmentally friendly and safe than using organic solvents such as benzene and chloroform in traditional processes, greatly reducing the use of toxic organic solvents, and reducing environmental pollution and harm to human health. The microwave-assisted extraction of the present invention has lower energy consumption than supercritical extraction, dual-frequency ultrasonic extraction, etc., can effectively save energy, reduce costs, and has a simple process and is easy to operate.

[0031] 2. The present invention optimizes the parameters of each step. In the step of S20, crude crystallization, the pH of the extract is first adjusted to acidic to remove insoluble substances, and the impurities soluble in acid and dissolved in organic solvents are further removed by combining methanol reflux, so as to achieve the purpose of preliminary separation and purification of reserpine. In the step of S30, recrystallization, alcohol water is used for pulping to remove salts and dissolved impurities that may exist in the crude crystals of reserpine, and reserpine is further purified. On this basis, impurities are repeatedly removed by adjusting pH, concentrating and other steps. Finally, the property of reserpine being insoluble in ethanol and slightly soluble in acetone is used to crystallize reserpine with an acetone-ethanol mixed solution to obtain high-purity reserpine. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the extraction method of the present invention.

[0033] Figure 2 The HPLC spectrum of the reserpine fine product of Example 1 of the present invention.

[0034] Figure 3 The HPLC spectrum of the reserpine fine product of Example 2 of the present invention.

[0035] Figure 4 The HPLC spectrum of the reserpine concentrate of Example 3 of the present invention.

[0036] Figure 5 The HPLC spectrum of the reserpine concentrate of Example 4 of the present invention.

[0037] Figure 6 The HPLC spectrum of the reserpine fine product of Example 5 of the present invention. DETAILED DESCRIPTION

[0038] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment. Unless otherwise specified, the materials and equipment used in this embodiment can be purchased from the market.

[0039] Please refer to Figure 1 The first aspect of the present invention provides a method for extracting reserpine from Rauwolfia ovata using microwave-assisted extraction, comprising the following steps:

[0040] S10, extraction step: crushing the root bark of Rauwolfia ovata and mixing it with an acidic ethanol solution, and performing microwave extraction;

[0041] S20, crude crystallization step: centrifuging and concentrating the extract, followed by acid precipitation, adding methanol to reflux, and standing to obtain a crude product;

[0042] S30, recrystallization step: the crude product is slurried with ethanol, then recrystallized through an acetone-ethanol system, and dried to obtain a finished product.

[0043] As a preferred embodiment, a method for extracting reserpine from Rauwolfia ovata using microwave-assisted extraction comprises the following steps:

[0044] S10, extraction step: grind and sieve the root bark of Rauwolfia ovata, add ethanol solution, mix thoroughly, adjust the pH to acidic, perform microwave extraction in a microwave extractor, repeat the extraction 2-4 times, and combine the extracts;

[0045] S20, crude crystallization step: centrifuging the extract, filtering, and obtaining a first filtrate; concentrating the first filtrate until a fixed precipitate is present, adding glacial acetic acid, adjusting the pH to be acidic, ultrasonicating for 5-10 minutes, standing for 1.5-2.5 hours, filtering and discarding insoluble matter, and obtaining a second filtrate; adding methanol to the second filtrate, refluxing, filtering, and obtaining a third filtrate; concentrating the third filtrate to one third of its original volume, standing overnight, and obtaining a concentrated solution; filtering the concentrated solution to obtain a solid; washing the solid with ethyl acetate, and drying in a drying oven to obtain a crude product;

[0046] S30, recrystallization step: take the crude product, add ethanol solution to pulp for 25-35 minutes, filter and add acetone, adjust the pH to acidic, filter and discard insoluble matter, concentrate and then add acetone and ethanol respectively, stir and crystallize at low temperature, filter and wash with anhydrous ethanol, and dry to obtain the finished product.

[0047] As a preferred embodiment, in S10, the extraction step, ethanol solution is added at a solid-liquid ratio of 1:10, wherein the mass percentage concentration of the ethanol solution is 70-90%.

[0048] As a preferred embodiment, in S10, the extraction step, the pH is adjusted to a range of 1-3.

[0049] As a preferred embodiment, in S10, the extraction step, the power of the microwave extractor is 500 W, the extraction is repeated 3 times, the single extraction time is 5 min, and the extraction temperature is 50-80°C.

[0050] As a preferred embodiment, in S20, the crude crystallization step, the reflux condition is reflux at 50-65° C. for 30 min.

[0051] As a preferred embodiment, in S20, the crude crystallization step, 3-5 times the volume of methanol is added to the second filtrate for reflux, and the process is repeated twice.

[0052] In the first aspect of the present invention, as an optional embodiment, in S20, the crude crystallization step, the amount of glacial acetic acid added is equal to the volume of the filtrate, and the pH is adjusted to 2.2-3.0.

[0053] As a preferred embodiment, in S30, the recrystallization step, the pH is adjusted to a range of 2-3.

[0054] As a preferred embodiment, in S30, the recrystallization step, the low-temperature crystallization condition is stirring crystallization at -10°C for 3 hours.

[0055] The following are some embodiments of the present application, and the present application is further described through the following embodiments.

[0056] Example 1

[0057] A method for extracting reserpine from Rauwolfia ovata using microwaves, comprising the following steps:

[0058] S10, extraction step:

[0059] 200 g of Rauwolfia root bark was crushed, all the powders were sieved through a 70-mesh sieve, 85% ethanol solution was added at a solid-liquid ratio of 1:10, the mixture was fully mixed, the pH was adjusted to 2.5 with hydrochloric acid, microwave extraction was performed in a microwave extractor for 15 minutes, the extraction was repeated 3 times, and the extracts were combined;

[0060] S20, crude crystallization step: centrifuge the extract, filter and concentrate the filtrate to half of the original volume, adjust the pH to 3.0 with glacial acetic acid, sonicate for 5-10 minutes, let stand for 2 hours, filter and discard the insoluble matter, add 3 times the volume of methanol to the filtrate, reflux at 58°C for 30 minutes, reflux, filter and concentrate the filtrate to one-third of the original volume, let stand overnight. Filter, wash the solid with 3 ml of ethyl acetate, and dry in a drying oven to obtain 2.07 g of crude product;

[0061] S30, recrystallization step: take 2.07g of the crude product, add 17ml of 85% ethanol to pulp for half an hour, filter and add 10.5ml of acetone, adjust the pH to 2.1, filter and discard the insoluble matter, concentrate and then add 16ml of acetone and 24ml of anhydrous ethanol respectively, stir and crystallize at -10℃ for 3h, filter and wash the solid with 3ml of water, then with 5ml of anhydrous ethanol, and dry to obtain 1.44g of reserpine solid.

[0062] According to the qualitative and quantitative methods of reserpine in Part II of the Pharmacopoeia of the People's Republic of China 2020 edition, such as Figure 2 As shown in the HPLC spectrum, the purity of the refined reserpine was 99.65%, which met the standards specified in the pharmacopoeia.

[0063] Example 2

[0064] A method for extracting reserpine from Rauwolfia ovata using microwaves, comprising the following steps:

[0065] S10, extraction step: 200g of Rauwolfia root bark was crushed, all the powders were sieved through a 70-mesh sieve, 70% ethanol solution was added at a solid-liquid ratio of 1:10, the mixture was fully mixed, the pH was adjusted to 2.1 with hydrochloric acid, microwave extraction was performed in a microwave extractor for 15 minutes, the extraction was repeated 3 times, and the extracts were combined;

[0066] S20, crude crystallization step: centrifuge the extract, filter and concentrate the filtrate to half of the original volume, adjust the pH to 2.7 with glacial acetic acid, sonicate for 5-10 minutes, let stand for 2 hours, filter and discard the insoluble matter, add 3 times the volume of methanol to the filtrate, reflux at 58°C for 30 minutes, reflux, filter and concentrate the filtrate to one-third of the original volume, let stand overnight. Filter, wash the solid with 5 ml ethyl acetate, and dry in a drying oven to obtain 1.89g of crude product;

[0067] S30, recrystallization step: take 1.89g of the crude product, add 15.5ml of 85% ethanol and beat for half an hour, filter and add 9.5ml of acetone, adjust the pH to 2.3, filter and discard the insoluble matter, concentrate and then add 14ml of acetone and 21ml of anhydrous ethanol respectively, stir and crystallize at -10℃ for 3h, filter and wash the solid with 3ml of water, then with 5ml of anhydrous ethanol, and dry to obtain 1.32g of reserpine solid.

[0068] According to the qualitative and quantitative methods of reserpine in Part II of the Pharmacopoeia of the People's Republic of China 2020 edition, such as Figure 3 As shown in the HPLC spectrum, the purity of the refined reserpine was 99.47%, which met the standards specified in the pharmacopoeia.

[0069] Example 3

[0070] A method for extracting reserpine from Rauwolfia ovata using microwaves, comprising the following steps:

[0071] S10, extraction step: 200g of Rauwolfia root bark was crushed, all the powders were sieved through a 70-mesh sieve, 85% ethanol solution was added at a solid-liquid ratio of 1:10, the mixture was fully mixed, the pH was adjusted to 2.8 with hydrochloric acid, microwave extraction was performed in a microwave extractor for 15 minutes, the extraction was repeated 3 times, and the extracts were combined;

[0072] S20, crude crystallization step: centrifuge the extract, filter and concentrate the filtrate to half of the original volume, adjust the pH to 2.2 with glacial acetic acid, sonicate for 5-10 minutes, let stand for 2 hours, filter and discard the insoluble matter, add 4 times the volume of methanol to the filtrate, reflux at a suitable temperature for 30 minutes, reflux, filter and concentrate the filtrate to one third of the original volume, let stand overnight. Filter, wash the solid with 5 ml of ethyl acetate, and dry in a drying oven to obtain 2.01 g of crude product;

[0073] S30, recrystallization step: take 2.01g of the crude product, add 16ml of 90% ethanol and beat for half an hour, filter and add 10ml of acetone, adjust the pH to 2.0, filter and discard the insoluble matter, concentrate and then add 15ml of acetone and 23ml of anhydrous ethanol respectively, stir and crystallize at -10℃ for 3h, filter and wash the solid with 4ml of water, then with 5ml of anhydrous ethanol, and dry to obtain 1.41g of reserpine solid.

[0074] According to the qualitative and quantitative methods of reserpine in Part II of the Pharmacopoeia of the People's Republic of China 2020 edition, such as Figure 4 As shown in the HPLC spectrum, the purity of the refined reserpine was 99.47%, which met the standards specified in the pharmacopoeia.

[0075] Example 4

[0076] A method for extracting reserpine from Rauwolfia ovata using microwaves, comprising the following steps:

[0077] S10, extraction step: 200g of Rauwolfia root bark was crushed, all the powders were sieved through a 70-mesh sieve, 65% ethanol solution was added at a solid-liquid ratio of 1:10, the mixture was fully mixed, the pH was adjusted to 2.8 with hydrochloric acid, microwave extraction was performed in a microwave extractor for 15 minutes, the extraction was repeated 3 times, and the extracts were combined;

[0078] S20, crude crystallization step: centrifuge the extract, filter and concentrate the filtrate to half of the original volume, adjust the pH to 1 with glacial acetic acid, sonicate for 5-10 minutes, let stand for 2 hours, filter and discard the insoluble matter, add 4 times the volume of methanol to the filtrate, reflux at a suitable temperature for 30 minutes, reflux, filter and concentrate the filtrate to one third of the original volume, let stand overnight. Filter, wash the solid with 3 ml of ethyl acetate, and dry in a drying oven to obtain 1.69 g of crude product;

[0079] S30, recrystallization step: take 1.69g of the crude product, add 13.5ml of 75% ethanol and beat for half an hour, filter and add 8.5ml of acetone, adjust the pH to 2.0, filter and discard the insoluble matter, concentrate and then add 13ml of acetone and 20ml of anhydrous ethanol respectively, stir and crystallize at -10℃ for 3h, filter and wash the solid with 3ml of water, then with 5ml of anhydrous ethanol, and dry to obtain 1.18g of reserpine solid.

[0080] According to the qualitative and quantitative methods of reserpine in Part II of the Pharmacopoeia of the People's Republic of China 2020 edition, such as Figure 5 As shown in the HPLC spectrum, the purity of the refined reserpine was measured to be 98.78%, which meets the standards specified in the pharmacopoeia.

[0081] Example 5

[0082] A method for extracting reserpine from Rauwolfia ovata using microwaves, comprising the following steps:

[0083] S10, extraction step: 200g of Rauwolfia root bark was crushed, all the powders were sieved through a 70-mesh sieve, 60% ethanol solution was added at a solid-liquid ratio of 1:10, the mixture was fully mixed, the pH was adjusted to 2.6 with hydrochloric acid, microwave extraction was performed in a microwave extractor for 15 minutes, the extraction was repeated 3 times, and the extracts were combined;

[0084] S20, crude crystallization step: centrifuge the extract, filter and concentrate the filtrate to half of its original volume, adjust the pH to 1.4 with glacial acetic acid, sonicate for 5-10 minutes, let stand for 2 hours, filter and discard insoluble matter, add 4 times the volume of methanol to the filtrate, reflux at a suitable temperature for 30 minutes, reflux, filter and concentrate the filtrate to one third of its original volume, let stand overnight. Filter, wash the solid with 3 ml of ethyl acetate, and dry in a drying oven to obtain 1.45 g of crude product;

[0085] S30, recrystallization step: take 1.45g of the crude product, add 12ml of 65% ethanol and beat for half an hour, filter and add 7.5ml of acetone, adjust the pH to 2.2, filter and discard the insoluble matter, concentrate and then add 11ml of acetone and 16.5ml of anhydrous ethanol respectively, stir and crystallize at -10℃ for 3h, filter and wash the solid with 4ml of water, then with 3ml of anhydrous ethanol, and dry to obtain 1.01g of reserpine solid.

[0086] According to the qualitative and quantitative methods of reserpine in Part II of the Pharmacopoeia of the People's Republic of China 2020 edition, such as Figure 6 As shown in the HPLC spectrum, the purity of reserpine was 97.23%, which did not meet the standards stipulated in the pharmacopoeia.

[0087] The above implementation modes are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for extracting reserpine from Rauwolfia ovata using microwave-assisted extraction, characterized in that: The following steps are involved: S10, extraction step: crushing the root bark of Rauwolfia ovata and mixing it with an acidic ethanol solution, and performing microwave extraction; S20, crude crystallization step: centrifuging and concentrating the extract, followed by acid precipitation, adding methanol to reflux, and standing to obtain a crude product; S30, recrystallization step: the crude product is slurried with ethanol, then recrystallized through an acetone-ethanol system, and dried to obtain a finished product.

2. The method according to claim 1, characterized in that The steps include: S10, extraction step: grind and sieve the root bark of Rauwolfia ovata, add ethanol solution, mix thoroughly, adjust the pH to acidic, perform microwave extraction in a microwave extractor, repeat the extraction 2-4 times, and combine the extracts; S20, crude crystallization step: centrifuging the extract, filtering, and obtaining a first filtrate; concentrating the first filtrate until a fixed precipitate is present, adding glacial acetic acid, adjusting the pH to be acidic, ultrasonicating for 5-10 minutes, standing for 1.5-2.5 hours, filtering and discarding insoluble matter, and obtaining a second filtrate; adding methanol to the second filtrate, refluxing, filtering, and obtaining a third filtrate; concentrating the third filtrate to one third of its original volume, standing overnight, and obtaining a concentrated solution; filtering the concentrated solution to obtain a solid; washing the solid with ethyl acetate, and drying in a drying oven to obtain a crude product; S30, recrystallization step: take the crude product, add ethanol solution to pulp for 25-35 minutes, filter and add acetone, adjust the pH to acidic, filter and discard insoluble matter, concentrate and then add acetone and ethanol respectively, stir and crystallize at low temperature, filter and wash with anhydrous ethanol, and dry to obtain the finished product.

3. The method according to claim 2, characterized in that S10, in the extraction step, adding ethanol solution at a solid-liquid ratio of 1:10, wherein the ethanol solution has a mass percentage concentration of 70-90%.

4. The method according to claim 2, characterized in that S10, in the extraction step, the pH is adjusted to a range of 1-3.

5. The method according to claim 2, characterized in that S10, in the extraction step, the power of the microwave extractor is 500 W, the extraction is repeated 3 times, the single extraction time is 5 min, and the extraction temperature is 50-80°C.

6. The method according to claim 2, characterized in that In the crude crystallization step S20, the reflux condition is reflux at 50-65° C. for 30 min.

7. The method according to claim 2, characterized in that S20, in the crude crystallization step, 3-5 times the volume of methanol is added to the second filtrate for reflux, and the process is repeated twice.

8. The method according to claim 2, characterized in that In S20, the crude crystallization step, the amount of glacial acetic acid added is equal to the volume of the filtrate, and the pH is adjusted to 2.2-3.

0.

9. The method according to claim 2, characterized in that S30, in the recrystallization step, the pH is adjusted to a range of 2-3.

10. The method according to claim 2, characterized in that In the recrystallization step S30, the low-temperature crystallization condition is to stir the crystallization at -10°C for 3h.

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