Method for extracting puerarin from kudzu vine root peel by using ultrasonic-assisted ionic liquid solution

Abstract

The invention discloses a method for extracting puerarin from kudzu vine root peel by using an ultrasonic-assisted ionic liquid solution. The method comprises the following steps: by taking waste kudzu vine root peel as a raw material, carrying out drying and crushing pretreatment, carrying out oscillation extraction under an ultrasonic condition by taking an ionic liquid aqueous solution as an extraction solvent, and adsorbing and purifying an extracting solution through an adsorbent to realize separation of puerarin and the ionic liquid. According to the method, the ionic liquid is used as a green solvent, mass transfer is enhanced by combining the ultrasonic cavitation effect, the extraction rate of puerarin is remarkably increased, and efficient recovery of the ionic liquid is achieved. The process is simple and convenient to operate, can be carried out at room temperature, and has outstanding environmental protection advantages. According to the method, the extraction rate of puerarin can reach 91.4% under optimal conditions, the recovery rate of ionic liquid can reach 99.9% through adsorption and purification, and the relative content of puerarin in desorption liquid is 92.9%.

Description

Technical Field

[0001] This invention belongs to the field of plant active ingredient extraction and purification technology, specifically relating to a method for extracting puerarin from kudzu root bark, a production waste, based on ultrasound-assisted ionic liquid solution. Background Technology

[0002] Kudzu root (Pueraria Lobata (willd) Ohwi) is a traditional Chinese medicine, and its roots are rich in puerarin, an isoflavone compound. Puerarin possesses pharmacological activities such as improving cardiovascular function and regulating blood glucose metabolism. It has been included in the Chinese Pharmacopoeia and is widely used in clinical treatment and functional product development. With the continuous growth of global demand for natural products, developing efficient and environmentally friendly puerarin extraction technologies has become an important research direction. Although traditional solvent extraction methods can achieve effective extraction, they suffer from drawbacks such as low extraction rates, long extraction times, and the need for large amounts of volatile reagents. Furthermore, the environmental and safety issues caused by organic solvent residues urgently need to be addressed. On the other hand, during the production of kudzu starch, a large amount of puerarin is lost during the peeling process of kudzu root processing, resulting in resource waste. Therefore, how to efficiently and environmentally extract puerarin from kudzu root peel is a problem that urgently needs to be solved. Summary of the Invention

[0003] This invention aims to overcome the shortcomings of existing technologies and provide a method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution. This method utilizes ultrasound-assisted ionic liquid solution to efficiently extract puerarin from kudzu root bark, a waste product of kudzu starch processing. This not only achieves green and efficient extraction and separation of puerarin but also promotes the resource-based reuse of kudzu production waste.

[0004] The objective of this invention is achieved through the following technical solution: A method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution, the method comprising the following steps: (1) Pretreatment of kudzu root bark: Kudzu root bark is dried and pulverized to obtain kudzu root bark powder for later use; (2) Extraction: Weigh the kudzu root bark powder, place it in a container, add a certain amount of ionic liquid extraction solvent, put it in an ultrasonic cleaner, shake and extract, let it stand and cool to room temperature, centrifuge, and filter to obtain puerarin extract. (3) The ionic liquid extraction solvent is a mixture of water and an ionic liquid; the ionic liquid is any one of 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM]BF4), 1-ethyl-3-methylimidazolium acetate ([EMIM]OAc), N-ethylpyrrolidine tetrafluoroborate ([EPM]BF4), N-ethylpyridine tetrafluoroborate ([EPy]BF4), 1-cyanopropyl-3-methylimidazolium tetrafluoroborate ([CPMIM]BF4), 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl), 1-ethoxyethyl-3-methylimidazolium tetrafluoroborate ([EOEMIM]BF4), 1-ethyl-3-methylimidazolium nitrate ([EMIM]NO3) and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate ([HOMIM]BF4); (3) Product purification: The puerarin extract obtained in step (2) is adsorbed with an adsorbent and the ionic liquid extraction solvent is removed. Then, puerarin is eluted from the adsorbent with ethanol to obtain purified puerarin. 50 mg of adsorbent is added to every 25 ml of puerarin extract; the adsorbent is any one of AB-8, D101, DM130, NKA-II and H-BCMBP.

[0005] As a preferred technical solution, in step (1), the kudzu root bark is freeze-dried, pulverized and sieved to obtain kudzu root bark powder, which is then placed in a desiccator and packaged for later use.

[0006] As a further preferred embodiment of this technical solution, the liquid-to-solid ratio of the ionic liquid extraction solvent and kudzu root bark powder in step (2) is 10-35:1 (mL:g).

[0007] As a further preferred embodiment of this technical solution, the ultrasonic power of the ultrasonic cleaner in step (2) is 400-500W.

[0008] As a further preferred embodiment of this technical solution, the extraction temperature in step (2) is 25 ℃-55 ℃.

[0009] As a further preferred embodiment of this technical solution, the extraction time in step (2) is 30 s-30 min.

[0010] As a further preferred embodiment of this technical solution, the concentration of the ionic liquid extraction solvent in step (2) is 10-50 g / L.

[0011] As a further preferred embodiment of this technical solution, after step (2) is completed, the mixture is allowed to cool to room temperature, centrifuged for 10-30 minutes, and filtered through a 0.45 μm filter membrane to obtain puerarin extract.

[0012] After completing step (2) of extraction, the present invention takes a quantitative amount of puerarin extract, dilutes it to prepare a sample solution, performs ultraviolet detection at 250 nm and calculates the extraction rate.

[0013] The adsorbent of this invention can be recycled after regeneration.

[0014] Ionic liquids (ILs) have attracted widespread attention due to their unique physicochemical properties. As a green solvent system composed of anions and cations, they not only possess advantages such as low volatility, high thermal stability, and recyclability, but also enhance their solubility for bioactive substances through multiple interaction mechanisms including hydrogen bonding, electrostatics, and van der Waals forces. Combining ILs with ultrasound-assisted technology can produce a synergistic effect: the ultrasonic cavitation effect promotes the mass transfer process, while the high solubility of ILs can significantly improve the extraction rate of target components.

[0015] H-BCMBP is a polymer formed by the crosslinking of biphenyl dichlorobenzyl. It has a large number of microporous systems with a size of 1.3-1.8 nm, which is highly matched with the molecular size of puerarin (approximately 1.47 nm). This pore size-selective molecular sieve effect is the main mechanism for its adsorption and separation. In addition, the biphenyl framework of H-BCMBP forms a highly electron-delocalized π-conjugated system, giving the material a strongly hydrophobic interface and making it difficult to adsorb hydrophilic [EMIM]BF4.

[0016] The principle of this invention: Addressing the problems of long extraction time, low efficiency, and large organic solvent consumption in traditional puerarin extraction methods, this invention proposes an ultrasound-assisted ionic liquid solution extraction strategy. This method uses an environmentally friendly ionic liquid aqueous solution to treat kudzu root peel, a waste product from kudzu starch processing. The ultrasonic cavitation effect enhances the mass transfer process, while the high solubility of puerarin in the ionic liquid significantly improves extraction efficiency. The resulting extract is purified using a porous polymer. Its high specific surface area and strong hydrophobic properties allow for the selective separation of puerarin and the ionic liquid, achieving efficient recovery of the ionic liquid.

[0017] Compared with the prior art, the advantages of this invention are: 1. This invention uses a green solvent, an ionic liquid solution, to extract kudzu root bark, a production waste. The process is simple, can be carried out at room temperature, and effectively recovers the ionic liquid, making it more environmentally friendly than traditional methods. Furthermore, using kudzu root bark as a raw material further achieves resource recycling.

[0018] 2. This invention employs ultrasound-assisted ionic liquid solution extraction of puerarin from kudzu root bark. The synergistic effect of the ionic liquid and ultrasound technology significantly enhances the mass transfer process, enabling rapid extraction of puerarin. Experiments show that extraction can be essentially completed in approximately 10 minutes.

[0019] 3. This invention employs ultrasound-assisted ionic liquid solution extraction technology to achieve efficient extraction of puerarin from kudzu root bark. Using 20 g / L [EMIM]BF4 aqueous solution as solvent, with a liquid-to-solid ratio of 25:1 and ultrasonic extraction at 25 ℃ for 10 min, the puerarin extraction rate reaches 91.4%, demonstrating high extraction efficiency.

[0020] 4. The present invention uses porous polymer H-BCMBP to achieve efficient purification of the extract, effectively recovering ionic liquids (ILs recovery rate of 99.98%) from the extract, and the relative content of puerarin in the purified desorption solution is significantly increased compared with that in the extract. Attached Figure Description

[0021] Figure 1 This invention illustrates the effect of different extractants on the extraction rate of puerarin in Examples 1, 1, and 2 of the present invention.

[0022] Figure 2 This illustrates the effect of different cationic skeletons (ILs) on the extraction rate of puerarin in Example 2 of this invention.

[0023] Figure 3 This invention illustrates the effect of different cationic side chain functional groups (ILs) on the extraction rate of puerarin in Example 2.

[0024] Figure 4 This illustrates the effect of different anions (ILs) on the extraction rate of puerarin in Example 2 of this invention.

[0025] Figure 5 This invention illustrates the effect of extraction temperature on the extraction rate of puerarin in Example 3.

[0026] Figure 6 This describes the effect of extraction time on the extraction rate of puerarin in Example 4 of the present invention.

[0027] Figure 7 This illustrates the effect of the liquid-to-solid ratio on the extraction rate of puerarin in Example 5 of the present invention.

[0028] Figure 8 This describes the effect of IL concentration on puerarin extraction rate in Example 6 of the present invention.

[0029] Figure 9 This illustrates the effect of different adsorbents on the adsorption capacity of puerarin in Example 7 of the present invention.

[0030] Figure 10 This is the H-BCMBP pore size distribution in Example 7 of the present invention.

[0031] Figure 11 This is a comparison of the ILs content in the desorption solution in Example 7 of the present invention.

[0032] Figure 12This is a comparison of the relative content of puerarin in the desorption solution in Example 7 of the present invention. Detailed Implementation

[0033] The following examples further illustrate the present invention in detail. It should be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0034] Example 1: Study on the effect of different extractants on the extraction rate of puerarin Experimental method: (1) Kudzu root bark was freeze-dried, pulverized and passed through a 100-mesh sieve to obtain kudzu root bark powder, and then placed in a desiccator for packaging and use.

[0035] (2) Four 1g portions of kudzu root powder were accurately weighed using an analytical balance and placed in centrifuge tubes. 25 mL of extraction solvent was added to each tube. The extraction solvents were water, water + [EMIM]BF4 (ILs mass concentration 40 g / L), ethanol, and ethanol + [EMIM]BF4 (ILs mass concentration 40 g / L), respectively. All tubes were placed in an ultrasonic cleaner (480W) and shaken for extraction at 25 ℃ for 2 h and a liquid-to-solid ratio of 25:1 (mL / g). After extraction, the tubes were allowed to cool to room temperature, centrifuged for 10 min, and filtered through a 0.45 μm filter to obtain the puerarin extract. The puerarin content in the extract was then determined using a UV spectrophotometer, and the extraction rate was calculated.

[0036] (3) Purification: The puerarin extract obtained in step (2) was purified by using the adsorbent H-BCMBP. The amount of adsorbent used was 50 mg per 25 mL of puerarin extract, and the adsorption time was 6 h. Then, puerarin was eluted from the adsorbent with ethanol to obtain purified puerarin. After adsorption, the residual amount of ionic liquid and the relative content of puerarin in the desorption solution were determined by high performance liquid chromatography, and the ionic liquid recovery rate was calculated.

[0037] The extraction rates of puerarin by different extraction solvents were recorded in Table 1 by ultraviolet light detection.

[0038]

[0039] Note: Extraction rate = (mass of puerarin in g / mass of puerarin in puerarin root bark in g) × 100%.

[0040] From the above table 1 and Figure 1It is known that the extraction rate of puerarin can reach 91.4% when the extraction solvent is water + [EMIM]BF4, which is the best effect. Therefore, a mixture of water and ionic liquid is selected as the extraction solvent.

[0041] Example 2 Effect of different cationic backbone ILs on puerarin extraction rate Ultrasonic-assisted extraction of puerarin from kudzu root bark using ionic liquid solution includes the following steps: (1) Clean the waste kudzu root bark, then freeze-dry it, pulverize it through a 100-mesh sieve to obtain kudzu root bark powder, and put it into a desiccator for packaging and use.

[0042] (2) Accurately weigh multiple 1g portions of kudzu root powder using an analytical balance and place them in centrifuge tubes. Add ILs-water solution as extraction solvent to each tube, with an ILs mass concentration of 40 g / L.

[0043] The ILs used were in three groups: A. ILs with different cations: [EMIM]BF4, [EPM]BF4, [EPy]BF4.

[0044] ILs with different cationic side chain functional groups: [EMIM]BF4, [CPMIM]BF4, [HOMIM]BF4, [EOEMIM]BF4, [AOEMIM]BF4.

[0045] C. ILs with different anions: [EMIM]PF6, [EMIM]NTf2, [EMIM]OAc, [EMIM]Cl, [EMIM]NO3, [EMIM]BF4.

[0046] All samples were placed in an ultrasonic cleaner (480W) for extraction with shaking. The extraction temperature was 25 ℃, the extraction time was 2 h, and the liquid-to-solid ratio was 25:1 (mL / g). After extraction, the samples were allowed to cool to room temperature, centrifuged for 10 min, and filtered through a 0.45 μm filter membrane to obtain the puerarin extract. The puerarin content in the extract was then determined by ultraviolet spectrophotometry, and the extraction rate was calculated.

[0047] (3) Purification: The puerarin extract obtained in step (2) was purified by using the adsorbent H-BCMBP. The amount of adsorbent used was 50 mg per 25 mL of puerarin extract, and the adsorption time was 6 h. Then, puerarin was eluted from the adsorbent with ethanol to obtain the purified puerarin. After the adsorption was completed, the residual amount of ionic liquid and the relative content of puerarin in the desorption solution were determined by high performance liquid chromatography, and the ionic liquid recovery rate was calculated.

[0048] Table 2 shows the effects of different ionic liquid extraction solvents on the extraction rate of puerarin, as determined by UV detection. The influence of different ionic liquids (ILs) on the extraction rate of puerarin is as follows: Figure 2As shown, the effects of ILs with different cationic side chain functional groups on the extraction rate of puerarin are as follows: Figure 3 As shown, the effects of different anions of ILs on the extraction rate of puerarin are as follows: Figure 4 As shown.

[0049] Table 2. Puerarin extraction rate using different ionic liquid extraction solvents

[0050] From Table 2, Figure 2 The extraction rates of puerarin from aqueous solutions of the three different cationic backbones were as follows: [EMIM]BF4 > [EPM]BF4 > [EPy]BF4. The imidazole ring of [EMIM]BF4 has a high positive potential and small molecular size, which can enhance the π-π stacking interaction to form a stable force with puerarin, thus resulting in the highest extraction rate (91.4%). ILs containing pyrrole rings ([EPM]BF4) and pyridine rings ([EPy]BF4) have weaker interactions with puerarin, and therefore their extraction rates are lower than those of imidazole ILs.

[0051] The effect of aqueous solutions of ILs with different cationic side chain functional groups on the extraction rate of puerarin is as follows: Figure 3 As shown, the extraction rates of puerarin by aqueous solutions of five different ILs with different side-chain functional groups were in the following order: [EMIM]BF4 > [CPMIM]BF4 > [HOEMIM]BF4 > [EOEMIM]BF4 > [AOEMIM]BF4. The extraction rate of puerarin by aqueous solution of [EMIM]BF4 was 91.4%, which was higher than that of aqueous solutions of ILs containing cyano, hydroxyethyl, and other functional groups. As the side chain length increased, the extraction rate of puerarin gradually decreased. When the side chain was ethyl acetate ([AOEMIM]BF4), the extraction rate of puerarin was only 79.8%.

[0052] The effect of different anionic ILs aqueous solutions on the extraction rate of puerarin is as follows: Figure 4 As shown, the extraction rates of puerarin from aqueous solutions of six ILs, all with [EMIM]+ cations but different anions, followed by [EMIM]BF4 > [EMIM]NO3 > [EMIM]Cl > [EMIM]OAc > [EMIM]NTf2 > [EMIM]PF6. The smaller the anion size of the ILs, the stronger the hydrogen bond formation ability between the ILs and puerarin, resulting in a tighter binding and a higher puerarin extraction rate. [EMIM]BF4, due to its anion BF4... - With low steric hindrance and strong hydrogen bonding ability, it can effectively bind puerarin molecules, thereby significantly improving the extraction rate (91.4%).

[0053] Example 3: Study on the effect of extraction temperature on puerarin extraction rate A method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution includes the following steps: (1) Kudzu root bark was freeze-dried, pulverized and passed through a 100-mesh sieve to obtain kudzu root bark powder, and then placed in a desiccator for packaging and use.

[0054] (2) Using an analytical balance, accurately weigh multiple 1g portions of kudzu root powder and place them in centrifuge tubes. Add [EMIM]BF4 aqueous solution (ILs mass concentration 40 g / L) to each tube. In an ultrasonic cleaner (480W), perform extraction with shaking at a fixed time of 30 min, a liquid-to-solid ratio of 25:1 (mL / g), and extraction temperatures of 15, 25, 35, 45, and 55 ℃. After extraction, allow the mixture to cool to room temperature, centrifuge for 10 min, and filter through a 0.45 μm filter membrane to obtain the puerarin extract. Then, use a UV spectrophotometer to determine the puerarin content in the puerarin extract and calculate the extraction rate.

[0055] (3) Purification: The puerarin extract obtained in step (2) was purified by separation using the adsorbent H-BCMBP. The amount of adsorbent used was 50 mg per 25 mL of puerarin extract, and the adsorption time was 6 h. Then, puerarin was eluted from the adsorbent with ethanol to obtain the purified puerarin. After adsorption, the residual amount of ionic liquid and the relative content of puerarin in the desorption solution were determined by high performance liquid chromatography, and the ionic liquid recovery rate was calculated.

[0056] UV detection showed the effect of different extraction temperatures on the extraction rate of puerarin as follows: Figure 5 As shown, the extraction efficiency of puerarin first increases and then decreases with increasing extraction temperature. The highest extraction rate of puerarin, reaching 90.3%, is achieved at 25 ℃, therefore 25 ℃ is selected as the optimal extraction temperature.

[0057] Example 4: Study on the effect of extraction time on puerarin extraction rate A method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution includes the following steps: (1) Kudzu root bark was freeze-dried, pulverized and passed through a 100-mesh sieve to obtain kudzu root bark powder, and then placed in a desiccator for packaging and use.

[0058] (2) Using an analytical balance, accurately weigh 1g of kudzu root powder into multiple portions and place them into centrifuge tubes. Add 25mL of [EMIM]BF4 aqueous solution (ILs mass concentration 40 g / L) to each tube. In an ultrasonic cleaner (480W), maintain a fixed extraction temperature of 25℃, a liquid-to-solid ratio of 25:1 (mL / g), and select extraction times of 0.1, 0.5, 1, 3, 5, 7, 10, 20, and 30 min for shaking extraction. After extraction, allow the mixture to cool to room temperature, centrifuge for 10 min, and filter through a 0.45 μm filter membrane to obtain puerarin extract. Subsequently, determine the puerarin content in the puerarin extract using ultraviolet spectrophotometry and calculate the extraction rate.

[0059] (3) Purification: The puerarin extract obtained in step (2) was purified by separation using the adsorbent H-BCMBP. The amount of adsorbent used was 50 mg per 25 mL of puerarin extract, and the adsorption time was 6 h. Then, puerarin was eluted from the adsorbent with ethanol to obtain the purified puerarin. After adsorption, the residual amount of ionic liquid and the relative content of puerarin in the desorption solution were determined by high performance liquid chromatography, and the ionic liquid recovery rate was calculated.

[0060] UV detection showed the effect of different extraction times on the extraction rate of puerarin as follows: Figure 6 As shown, the extraction rate of puerarin gradually increased with increasing extraction time, reaching a plateau (90.5%) at 10 min. Afterward, the extraction efficiency of puerarin tended to stabilize within 10-30 min. Considering both economics and efficiency, the optimal extraction time was 10 min.

[0061] Example 5: Study on the effect of liquid-to-solid ratio on puerarin extraction rate A method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution includes the following steps: (1) Kudzu root bark was freeze-dried, pulverized and passed through a 100-mesh sieve to obtain kudzu root bark powder, and then placed in a desiccator for packaging and use.

[0062] (2) Using an analytical balance, accurately weigh 1g of kudzu root powder into multiple portions and place them into centrifuge tubes. Add 25mL of [EMIM]BF4 aqueous solution (ILs mass concentration 40 g / L) to each tube. In an ultrasonic cleaner (480W), maintain a fixed extraction temperature of 25℃ and an extraction time of 10 min. Select liquid-to-solid ratios of 10, 15, 2, 25, 30, and 35 mL / g for shaking extraction. After extraction, allow the mixture to cool to room temperature, centrifuge for 10 min, and filter through a 0.45 μm filter membrane to obtain puerarin extract. Subsequently, determine the puerarin content in the puerarin extract using ultraviolet spectrophotometry and calculate the extraction rate.

[0063] (3) Purification: The puerarin extract obtained in step (2) was purified by using the adsorbent H-BCMBP. The amount of adsorbent used was 50 mg per 25 mL of puerarin extract, and the adsorption time was 6 h. After adsorption, the residual amount of ionic liquid and the relative content of puerarin in the desorption solution were determined by high performance liquid chromatography, and the ionic liquid recovery rate was calculated.

[0064] UV detection showed the effect of different material-to-liquid ratios on the extraction rate of puerarin. Figure 7 As shown, when the liquid-to-solid ratio increases from 10:1 (mL / g) to 25:1 (mL / g), the mass transfer rate increases, and the puerarin extraction rate rises. At a liquid-to-solid ratio of 25:1 (mL / g), the puerarin extraction rate is 91.3%. When the liquid-to-solid ratio exceeds 25:1 (mL / g), some of the ultrasonic energy is absorbed by the excess solvent, reducing the mechanical disruption effect of ultrasound on cells, and consequently decreasing the puerarin extraction rate. Therefore, the optimal liquid-to-solid ratio is 25:1 (mL / g).

[0065] Example 6: Study on the effect of different IL concentrations on puerarin extraction rate A method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution includes the following steps: (1) Kudzu root bark was freeze-dried, pulverized and passed through a 100-mesh sieve to obtain kudzu root bark powder, and then placed in a desiccator for packaging and use.

[0066] (2) Using an analytical balance, accurately weigh 1g of kudzu root powder into multiple portions and place them into centrifuge tubes. Add 25mL of [EMIM]BF4 aqueous solution of different concentrations to each tube. In an ultrasonic cleaner (480W), maintain a fixed extraction temperature of 25℃, an extraction time of 10 min, and a liquid-to-solid ratio of 25:1 (mL / g). Select IL concentrations of 0, 5, 10, 20, 30, and 50 g / L for shaking extraction. After extraction, allow the mixture to cool to room temperature, centrifuge for 10 min, and filter through a 0.45 μm filter membrane to obtain puerarin extract. Then, use a UV spectrophotometer to determine the puerarin content in the puerarin extract and calculate the extraction rate.

[0067] (3) Purification: The puerarin extract obtained in step (2) was purified by using the adsorbent H-BCMBP. The adsorbent dosage was 50 mg per 25 mL of puerarin extract, and the adsorption time was 6 h. Then, puerarin was eluted from the adsorbent with ethanol to obtain the purified puerarin. After adsorption, the residual amount of ionic liquid and the relative content of puerarin in the desorption solution were determined by high performance liquid chromatography, and the ionic liquid recovery rate was calculated.

[0068] UV detection showed the effect of different material-to-liquid ratios on the extraction rate of puerarin. Figure 8As shown, when the IL concentration is between 0 and 20 g / L, the extraction rate of puerarin increases significantly with increasing IL concentration, reaching a peak of 91.4% at an IL concentration of 20 g / L. The extraction rate tends to stabilize after the concentration exceeds 20 g / L, therefore, an IL concentration of 20 g / L is the optimal concentration for puerarin extraction.

[0069] Example 7: Study on the effect of different adsorbents on the purification effect of puerarin A method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution includes the following steps: (1) Kudzu root bark was freeze-dried, pulverized and passed through a 100-mesh sieve to obtain kudzu root bark powder, and then placed in a desiccator for packaging and use.

[0070] (2) Accurately weigh 1 g of kudzu root powder using an analytical balance, place it in a centrifuge tube, add [EMIM]BF4 aqueous solution (ILs mass concentration 20 g / L), and perform extraction by shaking in an ultrasonic cleaner (480W) at a fixed extraction temperature of 25 ℃, extraction time of 10 min, and liquid-to-solid ratio of 25:1 (mL / g). After extraction, allow it to cool to room temperature, centrifuge for 30 min, and filter it through a 0.45 μm filter membrane to obtain puerarin extract. Subsequently, determine the puerarin content in the puerarin extract and calculate the extraction rate using ultraviolet spectrophotometry.

[0071] (3) Take 7 portions (25 ml each) of the extract obtained in step (2) and purify them using adsorbents. The adsorbents used are D3520, NKA-9, AB-8, D101, DM130, NKA-II, and H-BCMBP. The amount of adsorbent used is 50 mg for each, and the adsorption time is 6 h. After adsorption, the desorbed solution is obtained. The residual amount of ionic liquid and the relative content of puerarin in the desorbed solution are determined by high performance liquid chromatography, and the ionic liquid recovery rate is calculated. Puerarin is eluted from the adsorbent with a small amount of ethanol to obtain puerarin. The adsorbent can be recycled after regeneration.

[0072] UV detection showed the effect of different adsorbents on the adsorption capacity of puerarin as follows: Figure 9 As shown, in terms of static adsorption, H-BCMBP had the highest adsorption capacity (79.6 mg / g); NKA-II resin was second (52.6 mg / g); the adsorption capacities of DM130, D101 and AB-8 resins were between 39.6 and 41.7 mg / g, with no significant difference; while the adsorption effects of D3520 and NKA-9 resins were poor, both below 30.0 mg / g.

[0073] Detection and Analysis: The pore size distribution of the adsorbent H-BCMBP was analyzed using a specific surface area and pore size analyzer. The pore size distribution is as follows: Figure 10As shown, H-BCMBP is a rigid polymer formed by crosslinking biphenyl dichlorobenzyl. It has a large number of micropores of 1.3-1.8 nm, which is highly matched with the molecular dynamics size of puerarin (approximately 1.47 nm). This pore-selective molecular sieve effect is the main mechanism of its adsorption. At the same time, H-BCMBP has a high specific surface area (1575 m²·g⁻¹), which further enhances the adsorption capacity of puerarin. Therefore, H-BCMBP exhibits high adsorption capacity for puerarin.

[0074] The desorption solution was analyzed by HPLC (212 nm), such as... Figure 11 This indicates that H-BCMBP has significantly better recovery performance for the ionic liquid [EMIM]BF4 than the traditional NKA-II resin. The residual amount of [EMIM]BF4 in the H-BCMBP desorption solution is only 4.54 mg / L (ILs recovery rate 99.98%), which is much lower than the residual amount of 640 mg / L of NKA-II resin (ILs recovery rate 96.8%).

[0075] The relative content of puerarin in the desorption solution is as follows: Figure 12 As shown, the relative content of puerarin in the extract was 71.68%, and the relative content of puerarin after H-BCMBP adsorption and separation reached 92.91%, slightly higher than that after NKA-II resin adsorption treatment (90.34%). This indicates that H-BCMBP successfully achieved efficient enrichment of puerarin and deep removal of ILs.

Claims

1. A method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution, characterized in that, The method includes the following steps: (1) Pretreatment of kudzu root bark: Kudzu root bark is dried and pulverized to obtain kudzu root bark powder for later use; (2) Extraction: Weigh the kudzu root bark powder, place it in a container, add a certain amount of ionic liquid extraction solvent, put it in an ultrasonic cleaner, shake and extract, let it stand and cool to room temperature, centrifuge, and filter to obtain puerarin extract. The ionic liquid extraction solvent is a mixture of water and an ionic liquid; the ionic liquid is any one of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium acetate, N-ethylpyrrolidine tetrafluoroborate, N-ethylpyridine tetrafluoroborate, 1-cyanopropyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium chloride, 1-ethoxyethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium nitrate, and 1-hydroxyethyl-3-methylimidazolium tetrafluoroborate. (3) Product purification: The puerarin extract obtained in step (2) is adsorbed with an adsorbent and the ionic liquid extraction solvent is removed. Then, puerarin is eluted from the adsorbent with ethanol to obtain purified puerarin. Add 2-5 g of adsorbent per milliliter of puerarin extract; the adsorbent is any one of AB-8, D101, DM130, NKA-II and H-BCMBP.

2. The method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution according to claim 1, characterized in that: In step (1), the kudzu root bark is freeze-dried, pulverized and sieved to obtain kudzu root bark powder, which is then placed in a desiccator and packaged for later use.

3. The method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution according to claim 1, characterized in that: In step (2), the liquid-to-solid ratio of the ionic liquid extraction solvent and kudzu root bark powder is 10-35:

1.

4. The method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution according to claim 1, characterized in that: The ultrasonic power of the ultrasonic cleaner in step (2) is 400-500W.

5. The method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution according to claim 1: the extraction temperature in step (2) is 25 ℃-55 ℃.

6. The method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution according to claim 1, characterized in that: The extraction time in step (2) is 30 s-30 min.

7. The method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution according to claim 1, characterized in that: In step (2), the concentration of the ionic liquid extraction solvent is 10-50 g / L.

8. The method for extracting puerarin from kudzu root bark using ultrasound-assisted ionic liquid solution according to claim 1, characterized in that: After completing step (2), allow the mixture to cool to room temperature, centrifuge for 10-30 min, and filter using a 0.45 μm filter membrane to obtain puerarin extract.

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