Method for enhancing purification and separation of artemisinin by polyion liquid coating

Abstract

The invention relates to a method for purifying and separating artemisinin reinforced by a polyion liquid coating, which comprises the following steps: adding an extracting agent into an extract containing artemisinin and wax oil, extracting, carrying out solid-liquid separation to obtain an extracting solution, adding the polyion liquid coating into the extracting solution, and separating and purifying to obtain artemisinin, the polyion liquid coating is prepared by the following steps: dissolving polyion liquid powder in an organic solvent, standing, defoaming, drying, soaking in an alkaline solution, washing with water, and drying. Wax oil in the extraction liquid is adsorbed by the polyion liquid coating, and co-crystallization of the wax oil and artemisinin is inhibited, so that high-purity artemisinin is obtained. The preparation method of the polyion liquid coating is simple, low in raw material cost, green and environment-friendly. The crystallization frequency required in the artemisinin product obtaining process can be reduced, and the method is an efficient purification and separation method.

Description

Technical Field

[0001] The invention belongs to the technical field of natural product purification, and specifically relates to a method for purifying artemisinin, and in particular to a method for enhancing the purification and separation of artemisinin by using a polyionic liquid coating. Background Art

[0002] Artemisinin is the most effective antimalarial drug recommended by the World Health Organization. It is mainly extracted and separated from Artemisia annua L. Artemisinin can also be used to treat dementia, schizophrenia, autoimmune diseases, etc. The world's demand for artemisinin will continue to grow.

[0003] At present, the separation and purification processes of artemisinin mainly include crystallization and column chromatography. The crystallization method is a method of purification and separation by controlling the temperature and changing the precipitation order by utilizing the different solubility of artemisinin and other impurities in Artemisia annua in different solvents. Although the crystallization separation technology is simple to operate, impurities with similar solubility and crystallization characteristics as artemisinin will co-crystallize with artemisinin and cannot be eliminated by the crystallization process. In the column chromatography method, when the extract passes through the filler, polar impurities are adsorbed, and the weakly polar artemisinin has a relatively short residence time in the filler, thereby improving the purity of artemisinin. Although column chromatography separation technology can purify artemisinin, it consumes a large amount of organic solvents, is easy to cause environmental pollution, and has low efficiency, low product yield, and high cost. In addition, column fillers will cause solid waste pollution, and regeneration needs to be carried out at a high temperature of 800°C, which has high energy consumption and high cost. Therefore, it is urgent to find a new route for separation and purification of artemisinin that is green, efficient, easy to operate, safe and stable.

[0004] CN107245081A discloses a method for purifying artemisinin based on the principle of ultrasonic vibration, which specifically includes the following steps: 1) Preparation: Take 50g of dried Artemisia annua branches and leaves and 1L of aqueous solution; 2) Mixing: Stir and mix the prepared Artemisia annua branches and leaves and the aqueous solution thoroughly; 3) Extraction: The mixed solution obtained in step 2) is subjected to ultrasonic vibration to extract the Artemisia annua solution; 4) Elution: The Artemisia annua solution obtained in step 3) is subjected to centrifugal precipitation, macroporous resin adsorption and ethyl acetate elution, and reduced pressure concentration to obtain a crude artemisinin product; 5) Purification: The crude artemisinin product obtained in step 4) is purified by alkyl halide; and then the pure product is obtained by recrystallization. The preparation process of artemisinin in this method is simple, the purification efficiency is high, and the preparation cost is low. However, the alkyl halide used in this method is highly toxic and the existing macroporous resin has high regeneration energy consumption, which is not in line with the current trend of vigorously promoting the "dual carbon" policy.

[0005] Therefore, simplifying the purification process of artemisinin, efficiently separating artemisinin from other components in Artemisia annua, and obtaining artemisinin products with high purity and good crystal quality are issues that need to be urgently addressed in the current industrial production of artemisinin. Summary of the Invention

[0006] In view of the problems existing in the prior art, the object of the present invention is to overcome the defects of the prior art and provide a method for enhancing the purification and separation of artemisinin by using a polyionic liquid coating. This method uses a coating prepared from a polyionic liquid to adsorb wax oil, inhibits the co-crystallization of wax oil and artemisinin during the crystallization process, quickly separates artemisinin from wax oil, and enhances the purification and separation process of artemisinin, thereby obtaining a high-purity artemisinin product.

[0007] The present invention also provides a polyionic liquid used in the above method, its preparation method, and its application in the purification and separation of artemisinin.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A polyionic liquid, whose chemical name is poly(3-(2-(acyloxy)ethyl)-1-vinylimidazole) bromide, and the acyloxy group refers to an acyloxy group of C6-C18. For example, it can be n-octanoyloxy, n-decanoyloxy, dodecanoyloxy, octadecanoyloxy, etc., and preferably octadecanoyloxy (i.e., stearoyloxy). The specific structural formula of the polyionic liquid is as follows: Among them, R is any saturated straight-chain alkyl group of C6-C18.

[0009] The present invention provides a preparation method of the above polyionic liquid, which includes the following steps: 1) Mix any saturated fatty acid of C6-C18, 2-bromoethanol, and the catalyst p-toluenesulfonic acid, and react at 30-70 °C for 5-10 h. After the reaction is completed, fatty acid-2-bromoethyl ester is obtained through post-treatment; 2) Mix fatty acid-2-bromoethyl ester and 1-vinylimidazole and react at 40-80 °C for 24-48 h. After the reaction is completed, an ionic liquid monomer is obtained through post-treatment; 3) Dissolve the ionic liquid monomer and azobisisobutyronitrile in DMF, and carry out a polymerization reaction at 50-75 °C for 12-24 h under an inert gas (such as nitrogen, argon, etc.) atmosphere. After the reaction is completed, solid-liquid separation is carried out, and after washing and drying, the polyionic liquid is obtained.

[0010] In the above preparation method of the polyionic liquid, specifically, in step 1), the molar ratio of the saturated fatty acid to 2-bromoethanol is preferably 1:1-4; the molar ratio of the saturated fatty acid to the catalyst p-toluenesulfonic acid is 1:0.08-0.2; In step 2), the molar ratio of fatty acid-2-bromoethyl ester to 1-vinylimidazole is preferably 1-2:1; In step 3), the mass ratio of the ionic liquid monomer to azobisisobutyronitrile is preferably 0.8-1:0.02-0.05.

[0011] The present invention provides an application of the above polyionic liquid in the purification and separation of artemisinin.

[0012] The present invention provides a method for enhancing the purification and separation of artemisinin by a polyionic liquid coating. An extractant is added to an extract containing artemisinin and wax oil, and extraction is carried out (stirring extraction can be carried out at 45 - 55 °C for 0.5 - 1 h), followed by solid-liquid separation to obtain an extractant solution. A polyionic liquid coating is added to the extractant solution, and separation and purification are carried out to obtain artemisinin. The polyionic liquid coating is prepared through the following steps: dissolving the powder of the polyionic liquid in an organic solvent, standing for defoaming, transferring it into a carrier, drying, then soaking it in an alkaline solution, and finally rinsing with water and drying to obtain the polyionic liquid coating.

[0013] In the present invention, the extract containing artemisinin and wax oil is generally obtained through the following steps: mixing Artemisia annua with petroleum ether (preferably at a material-liquid ratio of 1 g: 5 - 15 mL) and stirring for 2 - 5 h, then filtering to obtain a clear solution, and rotary evaporating to remove the solvent to obtain the extract containing artemisinin and wax oil.

[0014] As a preferred technical solution of the present invention, the extractant can be an aqueous methanol solution.

[0015] Preferably, the volume concentration of methanol in the aqueous methanol solution is 50 - 70%, for example, it can be 50%, 55%, 60%, 65%, 68% or 70%, etc.

[0016] Preferably, the solid-liquid ratio of the extract containing artemisinin and wax oil to the extractant aqueous methanol solution can be 1 g: (7 - 10) mL, for example, it can be 1 g: 7 mL, 1 g: 7.5 mL, 1 g: 8 mL, 1 g: 8.5 mL, 1 g: 9 mL, 1 g: 9.5 mL or 1 g: 10 mL, etc.

[0017] As a preferred technical solution of the present invention, the mass ratio of the extract containing artemisinin and wax oil to the polyionic liquid coating can be 1: (0.03 - 0.5), for example, it can be 1: 0.03, 1: 0.05, 1: 0.1, 1: 0.2, 1: 0.25, 1: 0.3, 1: 0.4 or 1: 0.5, etc.

[0018] As a preferred technical solution of the present invention, the steps of separation and purification include stirring and crystallization.

[0019] Preferably, the stirring time is 0.5 - 5 h, such as 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc. The stirring temperature is 30 - 60 °C, such as 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C or 60 °C, etc.

[0020] Preferably, the crystallization time is 1 - 10 h, such as 1 h, 1.5 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h or 10 h, etc. The crystallization temperature is 5 - 25 °C, such as 5 °C, 8 °C, 10 °C, 13 °C, 15 °C, 18 °C, 20 °C, 23 °C or 25 °C, etc.

[0021] As a preferred technical solution of the present invention, the preparation method of the polyionic liquid coating comprises the following steps: adding the powder of the polyionic liquid into an organic solvent dichloromethane, stirring and dissolving (it can be stirred and dissolved at 30 - 40 °C for 0.5 - 2 h), then standing for defoaming, pouring it into a plastic petri dish, drying, then soaking it in an alkaline solution, and finally rinsing with water and drying to obtain.

[0022] Furthermore, the organic solvent can be dichloromethane, and the solid-liquid ratio of the polyionic liquid powder to the organic solvent dichloromethane is 1 g:(10 - 20) mL. Such as 1 g:10 mL, 1 g:11 mL, 1 g:12 mL, 1 g:13 mL, 1 g:14 mL, 1 g:15 mL, 1 g:16 mL, 1 g:17 mL, 1 g:18 mL, 1 g:19 mL or 1 g:20 mL, etc.

[0023] Preferably, after standing for defoaming and pouring it into a plastic petri dish, the material of the plastic petri dish is polystyrene.

[0024] Preferably, the alkaline solution is an ammonia water solution, and the mass fraction of the ammonia water solution is 0.1 - 0.5 wt%, such as 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt% or 0.5 wt%, etc. Preferably, the soaking time is 0.5 - 2 h, such as 0.5 h, 1 h, 1.5 h or 2 h, etc.

[0025] As an optimization, the method for enhancing the purification and separation of artemisinin by the above-mentioned polyionic liquid coating may specifically be as follows: Add an aqueous methanol solution with a volume concentration of 50-70% to the extract containing artemisinin and wax oil, stir and extract at 45-55 °C for 0.5-1 h, then filter and separate to obtain an extract. Add a polyionic liquid coating to the extract, stir at 30-60 °C for 0.5-5 h, crystallize at 5-25 °C for 1-10 h, filter and dry to obtain artemisinin; the solid-liquid ratio of the extract to the aqueous methanol solution is 1 g: (7-10) mL, and the mass ratio of the extract to the polyionic liquid coating is 1: (0.03-0.5).

[0026] The numerical ranges described in the present invention include not only the above-listed point values, but also any point values between the above numerical ranges not listed. Due to space limitations and for the sake of brevity, the specific point values included in the described ranges are not exhaustively listed in the present invention. Compared with the prior art, the present invention has at least the following advantages and beneficial effects: (1) The present invention designs and synthesizes a polyionic liquid compound. Through research, it is found that using this polyionic liquid to make a coating as an adsorbent to adsorb wax oil can effectively inhibit the co-precipitation of wax oil and artemisinin during the crystallization process, strengthen the purification and separation process of artemisinin, and thus improve the purity of artemisinin; (2) The polyionic liquid coating used in the present invention is simple to prepare, has a large specific surface area, and is convenient to separate from artemisinin after adsorbing wax oil; (3) The present invention can reduce the number of crystallization times during the process of obtaining artemisinin products and is an efficient purification and separation method. Description of the Drawings

[0027] Figure 1 It is the HPLC detection result diagram of the product in Example 1; Figure 2 It is the HPLC detection result diagram of the product in Comparative Example 1; Figure 3 It is the synthesis route diagram of the poly(3-(2-(octadecanoyloxy)ethyl)-1-vinylimidazole) bromide; in the figure, n refers to the degree of polymerization; Figure 4 It is the NMR spectrum diagram of the poly(3-(2-(octadecanoyloxy)ethyl)-1-vinylimidazole) bromide (PIL) and its monomer (IL). Detailed Embodiments

[0028] The following further details the technical solutions of the present invention in combination with embodiments, but the protection scope of the present invention is not limited thereto.

[0029] In the following embodiments, the raw materials used are all ordinary commercially available products that can be directly purchased, or can be prepared by conventional techniques in the art.

[0030] In the following examples, an Arc HPLC (Waters, America) was used to determine the purity of artemisinin by the external standard method. The stationary phase was a C 18 column (4.6 mm × 250 mm, 5.0 μm), the mobile phase was acetonitrile and water, the volume ratio of acetonitrile to water was 55:45, and the flow rate was 1.0 mL / min; the column temperature was 25 °C, and the detection wavelength was 210 nm.

[0031] In the present invention, the specific structural formula of the polyionic liquid is as follows: Among them, R is any saturated straight-chain alkyl group with 6 to 18 carbon atoms.

[0032] Taking poly(3-(2-(octadecanoyloxy)ethyl)-1-vinylimidazole) bromide (i.e., R is a saturated straight-chain alkyl group with 18 carbon atoms) as an example of the polyionic liquid, the specific synthesis steps are as follows (the synthesis route can be seen in Figure 3 ) 1) Stearic acid (12 mmol, 3.4138 g) and 2-bromoethanol (24 mmol, 2.9990 g) were added to a round-bottom flask and stirred well to dissolve. Then, p-toluenesulfonic acid (1.2 mmol, 0.2066 g) was added as a catalyst, and the reaction was carried out at 60 °C for 8 h. After the reaction, it was cooled to room temperature. First, it was dissolved in 50 mL of dichloromethane, and then extracted and separated 3 times with 25 mL of deionized water. After that, dichloromethane was removed by rotary evaporation to obtain a white solid, which was dried in vacuo at 30 °C for 12 h to obtain stearic acid-2-bromoethyl ester; 2) Stearic acid-2-bromoethyl ester (10.2 mmol, 3.9927 g) and 1-vinylimidazole (6 mmol, 0.5647 g) were added to a round-bottom flask, and the reaction was carried out at 80 °C for 48 h. After the reaction, the unreacted ester was washed away with ethyl acetate, filtered, and dried in vacuo at 30 °C for 12 h to obtain the ionic liquid monomer; 3) 1 g of the ionic liquid monomer was added to 10 mL of N,N-dimethylformamide (DMF) and stirred well to dissolve. Then, 5 mL of DMF containing 0.02 g of azobisisobutyronitrile (AIBN) was added, and polymerization was carried out at 70 °C for 24 h under a nitrogen atmosphere. A white solid precipitated out, was filtered, rinsed with a small amount of DMF, and dried in vacuo at 30 °C for 12 h to obtain the polyionic liquid.

[0033] When synthesizing other polyionic liquids, stearic acid in step 1) can be replaced with the corresponding saturated fatty acid, such as n-octanoic acid, n-nonanoic acid, n-decanoic acid, n-dodecanoic acid, n-hexadecanoic acid, etc.

[0034] The results of the 1H NMR spectrum of the ionic liquid monomer obtained in the above synthesis process are as follows: 1 H NMR (600 MHz, CDCl3) δ 7.98 (t, J = 1.7 Hz, 1H), 7.78 (t, J = 1.5 Hz, 1H), 7.36 (dd, J = 15.6, 8.8 Hz, 1H), 6.00 (dd, J = 15.6, 2.4 Hz, 1H), 5.44 (dd, J = 8.7, 2.4 Hz, 1H), 4.53 - 4.50 (m, 2H), 4.44 - 4.40 (m, 2H), 2.30 (t, J = 7.4 Hz, 2H), 1.49 - 1.41 (m, 2H), 1.27 - 1.18 (m, 28H), 0.85 (t, J = 7.0 Hz, 3H).

[0035] Figure 4 The 1H NMR spectra of the above poly(3-(2-(octadecanoyloxy)ethyl)-1-vinylimidazolium) bromide (PIL) and its ionic liquid monomer (IL) are given. It can be seen from the comparison in the figure that the hydrogen of the olefin double bond in the polyionic liquid disappears in the NMR spectrum, indicating the successful synthesis of the polyionic liquid.

[0036] Example 1 In the following examples, the polyionic liquid coating was prepared by the following method: 0.2 g of poly(3-(2-(octadecanoyloxy)ethyl)-1-vinylimidazolium) bromide was added to 2 mL of dichloromethane, stirred at 40 °C for 1 h to dissolve, allowed to stand for 0.5 h to remove bubbles, poured into a polystyrene plastic petri dish, dried at 30 °C for 0.5 h, then soaked in 0.2 wt% ammonia water for 2 h, rinsed with water, and dried at 30 °C for 5 h.

[0037] A method for enhancing the purification and separation of artemisinin by a polyionic liquid coating is as follows: 1 g of the extract containing artemisinin and wax oil was dissolved in 7 mL of 70% aqueous methanol solution, stirred and extracted at 55 °C for 0.5 h, filtered to obtain an extract containing artemisinin and wax oil; 0.3 g of C 18 polyionic liquid coating was added to the extract, stirred at 60 °C for 2 h, then placed in a low-temperature constant temperature bath, crystallized at 10 °C for 5 h, filtered, and dried at 50 °C. The HPLC spectrum of the obtained product is as Figure 1 shown. It can be seen from the figure that the peak time of artemisinin is 9.669 min and the purity is 98.46%.

[0038] The extract containing artemisinin and wax oil is obtained through the following steps: Mix 100 g of Artemisia annua with 800 mL of petroleum ether and stir for 3 h, then filter to obtain a clear solution, and rotary evaporate to remove the solvent to obtain the extract containing artemisinin and wax oil.

[0039] Examples 2 - 8 Comparative Example 1 Dissolve 1 g of the extract containing artemisinin and wax oil in 7 mL of a 70% aqueous methanol solution, stir and extract at 55 °C for 0.5 h, filter to obtain the extract containing artemisinin and wax oil, then place it in a low-temperature constant-temperature bath, crystallize at 10 °C for 5 h, filter, and dry at 50 °C. The HPLC chromatogram of the obtained product is as Figure 2 shown. It can be seen from the figure that the obtained product has more impurities. The peak emergence time of artemisinin is 9.364 min, and the purity is 74.55%.

[0040] Combined with the analysis of Example 1 and Comparative Example 1, it can be known that after adding C 18 polyionic liquid coating, it can significantly adsorb the wax oil in the extract, reduce the co-precipitation of wax oil and artemisinin, and thus improve the purity of the artemisinin product. After purification by the method of the present invention, the purity of the obtained artemisinin product is above 93.19%, and the highest reaches 98.46%.

[0041] In summary, the method of the present invention adsorbs the wax oil in the extract by adding a polyionic liquid coating, inhibits its co-crystallization with artemisinin, and thus obtains high-purity artemisinin. The preparation method of the polyionic liquid coating is simple, the raw material cost is low, and it is green and environmentally friendly. The present invention can also reduce the number of crystallization times required in the process of obtaining artemisinin products, and is an efficient purification and separation method.

[0042] The applicant declares that the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A polyionic liquid, characterized in that The structural formula is as follows: Wherein, R is any saturated straight-chain alkane group of C6 to C18.

2. The method for preparing the polyionic liquid according to claim 1, characterized in that: The steps include: 1) Saturated fatty acid, 2-bromoethanol and p-toluenesulfonic acid catalyst are mixed and reacted at 30-70°C for 5-10 hours. After the reaction is completed, fatty acid-2-bromoethyl ester is obtained through post-treatment; 2) Then, fatty acid-2-bromoethyl ester and 1-vinylimidazole are mixed and reacted at 40-80° C. for 24-48 hours. After the reaction is completed, the ionic liquid monomer is obtained by post-treatment; 3) Dissolve the ionic liquid monomer and azobisisobutyronitrile in DMF, react at 50-75°C for 12-24 hours under an inert gas atmosphere, separate the solid and liquid after the reaction, wash and dry to obtain a polyionic liquid.

3. The method for preparing a polyionic liquid according to claim 1, characterized in that: In step 1), the molar ratio of saturated fatty acid to 2-bromoethanol is 1:1-4; the molar ratio of saturated fatty acid to catalyst p-toluenesulfonic acid is 1:0.08-0.2; In step 2), the molar ratio of fatty acid-2-bromoethyl ester to 1-vinylimidazole is 1-2:1; In step 3), the mass ratio of the ionic liquid monomer to azobisisobutyronitrile is 0.8-1:0.02-0.

05.

4. Use of the polyionic liquid according to claim 1 in the purification and separation of artemisinin.

5. A method for enhancing the purification and separation of artemisinin by polyionic liquid coating, characterized in that: Adding an extracting agent to an extract containing artemisinin and wax oil, extracting, and separating the solid and liquid to obtain an extract, adding a polyionic liquid coating to the extract, separating and purifying, and obtaining artemisinin; The polyionic liquid coating is prepared by the following steps: dissolving the polyionic liquid powder of claim 1 in an organic solvent, standing to remove bubbles, transferring to a carrier, drying, then soaking in an alkaline solution, and finally washing with water and drying.

6. The method for enhancing the purification and separation of artemisinin by polyionic liquid coating as claimed in claim 5, characterized in that: The extractant is a methanol aqueous solution, and the volume concentration of methanol in the methanol aqueous solution is 50-70%; the solid-liquid ratio of the extract containing artemisinin and wax oil to the extractant is 1g: (7-10)mL; the mass ratio of the extract containing artemisinin and wax oil to the polyionic liquid coating is 1: (0.03-0.5).

7. The method for enhancing the purification and separation of artemisinin by polyionic liquid coating as claimed in claim 5, characterized in that: The separation and purification includes stirring and crystallization; the stirring time is 0.5 to 5 hours, and the stirring temperature is 30 to 60° C.; the crystallization time is 1 to 10 hours, and the crystallization temperature is 5 to 25° C.

8. The method for enhancing the purification and separation of artemisinin by polyionic liquid coating as claimed in claim 5, characterized in that: The organic solvent is dichloromethane, and the solid-liquid ratio of the polyionic liquid powder to the organic solvent is 1 g: (10-20) mL.

9. The method for enhancing the purification and separation of artemisinin by polyionic liquid coating as claimed in claim 5, characterized in that: The carrier is a plastic culture dish, and the material of the plastic culture dish is polystyrene.

10. The method for enhancing the purification and separation of artemisinin by polyionic liquid coating as claimed in claim 5, characterized in that: The alkaline solution is an ammonia solution, the mass fraction of the ammonia solution is 0.1-0.5wt%, and the soaking time is 0.5-2h.

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