Method for removing heavy metals in radix puerariae extract

Abstract

The invention provides a method for removing heavy metals in a radix puerariae extract. The method comprises the following steps: step 1, crushing radix puerariae; step 2, mixing radix puerariae powder with an ethanol solution to obtain a first treated substance; step 3, filtering the first treated substance to obtain a first treated solution; step 4, adding glutathione S-transferase and metallothionein into the first treatment solution, and stirring to obtain a second treatment substance; step 5, adding activated carbon into the second treated substance, and stirring to obtain a third treated substance; step 6, filtering the third treated substance to obtain a second treated solution; and step 7, concentrating and drying the second treatment liquid to obtain radix puerariae extract powder. Effective components are extracted through an ethanol solution, GST and MT react with heavy metal to specifically bind heavy metal ions, then the heavy metal is further removed by combining activated carbon adsorption, and finally the heavy metal in the radix puerariae extract is removed through the steps of filtering, drying and the like, so that the problems of loss of active components and introduction of new impurities caused by a chemical precipitation method are avoided, and the operation is simpler and more convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of removing heavy metals from plant extracts, and in particular, to a method for removing heavy metals from Pueraria lobata extracts. Background Art

[0002] As an important plant with both medicinal and edible uses, Pueraria lobata is widely used in the fields of food, health products, and pharmaceuticals due to its rich flavonoid compounds, such as puerarin, daidzein, etc. Pueraria lobata extracts have received extensive attention due to their significant health care functions (such as reducing blood lipids, anti-inflammatory, antioxidant, etc.). However, with the intensification of industrial pollution, natural plants such as Pueraria lobata are prone to absorbing heavy metals in the soil and environment during growth, such as lead Pb 2+ , cadmium Cd 2+ , arsenic As 3+ , etc., resulting in excessive heavy metal content in the extracts, affecting their safety and market competitiveness.

[0003] Currently, for the removal of heavy metals from natural product extracts, common methods include chemical precipitation, ion exchange, and membrane separation. However, these methods have certain limitations. For example, the chemical precipitation method requires the use of a large amount of chemical reagents, which may lead to the loss of active ingredients in the extracts or the introduction of new impurities; although the ion exchange method and the membrane separation method can effectively remove heavy metals, they are complex in operation and high in cost, and it is difficult to promote and apply them in large-scale production. In addition, these methods usually carry out heavy metal removal after the extraction of the extracts is completed, resulting in a long process flow and increased production costs.

[0004] Therefore, there is an urgent need for a Pueraria lobata extraction process to solve the above problems. Summary of the Invention

[0005] The main object of the present invention is to provide a method for removing heavy metals from Pueraria lobata extracts, so as to at least solve the problems that the chemical precipitation method in the prior art may cause the loss of active ingredients in the extracts or the introduction of new impurities, and the ion exchange method and the membrane separation method are complex in operation.

[0006] To achieve the above object, the present invention provides a method for removing heavy metals from Pueraria lobata extracts, including:

[0007] Step 1: Crush Pueraria lobata to a target particle size to obtain Pueraria lobata powder;

[0008] Step 2: Mix the Pueraria lobata powder with an ethanol solution and stir for a first duration at a first temperature to obtain a first treated product;

[0009] Step 3: Filter the first treated product for the first time to obtain a first treated liquid with solid residues filtered out;

[0010] Step 4: After adjusting the pH of the first treatment solution to 7.0 - 7.5, add glutathione S-transferase and metallothionein to the first treatment solution, control the temperature at 36 - 38 °C, and stir for a second duration to obtain a second treatment product;

[0011] Step 5: Add activated carbon to the second treatment product and stir for a third duration at a second temperature to obtain a third treatment product;

[0012] Step 6: Filter the third treatment product for the second time to obtain a second treatment solution;

[0013] Step 7: After concentrating and drying the second treatment solution, obtain kudzu root extract powder.

[0014] Optionally, in step 1, the target particle size is 40 - 80 mesh.

[0015] Optionally, in step 2:

[0016] The concentration of the ethanol solution is 65% - 75%, the first temperature is 60 - 70 °C, and the first duration is 120 - 150 min.

[0017] Optionally, in step 2: The mass ratio of the kudzu root powder to the ethanol solution is 1:12 - 15.

[0018] Optionally, in step 4, the amount of glutathione S-transferase added to each 1 L of the first treatment solution is 15 - 25 U, and the amount of metallothionein added to each 1 L of the first treatment solution is 0.3 - 0.7 mg.

[0019] Optionally, in step 4, the second duration is 100 - 130 min.

[0020] Optionally, in step 4, control the temperature at 37 °C and the second duration at 120 min.

[0021] Optionally, in step 5, the second temperature is room temperature and the third duration is 50 - 80 min.

[0022] Optionally, the first filtration uses medium-speed qualitative filter paper.

[0023] Optionally, the second filtration uses a microfiltration membrane with a pore size of 0.22 μm.

[0024] A method for removing heavy metals from Pueraria lobata extract according to the technical solution of the present invention includes: Step 1, crushing Pueraria lobata to a target particle size to obtain Pueraria lobata powder; Step 2, mixing the Pueraria lobata powder with an ethanol solution and stirring for a first duration at a first temperature to obtain a first treated product; Step 3, performing a first filtration on the first treated product to obtain a first treated liquid with solid residues filtered out; Step 4, adjusting the pH of the first treated liquid to 7.0 - 7.5, then adding glutathione S-transferase and metallothionein to the first treated liquid, controlling the temperature at 36 - 38 °C, and stirring for a second duration to obtain a second treated product; Step 5, adding activated carbon to the second treated product and stirring for a third duration at a second temperature to obtain a third treated product; Step 6, performing a second filtration on the third treated product to obtain a second treated liquid; Step 7, concentrating and drying the second treated liquid to obtain Pueraria lobata extract powder. Thus, by first crushing Pueraria lobata into powder to increase the contact area with the extraction solvent, then using an ethanol solution to extract the active ingredients, while ensuring a high extraction efficiency, GST and MT are utilized to specifically bind heavy metal ions through reaction with heavy metals, and further removing heavy metals by combining with activated carbon adsorption. Finally, heavy metals in the Pueraria lobata extract are removed through steps such as filtration and drying, avoiding the problems of loss of active ingredients and introduction of new impurities caused by the chemical precipitation method, with simple operation and effectively improving the efficiency of removing heavy metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0026] Figure 1 is a flowchart of a method for removing heavy metals from Pueraria lobata extract according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0028] As Figure 1 shown, a method for removing heavy metals from Pueraria lobata extract includes:

[0029] Step 1, crushing Pueraria lobata to a target particle size to obtain Pueraria lobata powder;

[0030] Step 2, mixing the Pueraria lobata powder with an ethanol solution and stirring for a first duration at a first temperature to obtain a first treated product;

[0031] Step 3, performing a first filtration on the first treated product to obtain a first treated liquid with solid residues filtered out;

[0032] Step 4: After adjusting the pH of the first treatment solution to 7.0 - 7.5, add glutathione S-transferase and metallothionein to the first treatment solution, control the temperature at 36 - 38°C, and stir for a first period of time to obtain a second treatment product;

[0033] Step 5: Add activated carbon to the second treatment product and stir for a second period of time at a second temperature to obtain a third treatment product;

[0034] Step 6: Filter the third treatment product for the second time to obtain a second treatment solution;

[0035] Step 7: After concentrating and drying the second treatment solution, obtain kudzu root extract powder.

[0036] Specifically, in Step 1, the kudzu root raw material is pulverized to obtain kudzu root powder, making its particle size reach a suitable size to increase the specific surface area of the kudzu root. Through pulverization, the cell walls of the kudzu root are broken, and more internal components are exposed, having a larger contact area with the subsequent extraction solvent. In this way, during the extraction process, the extraction solvent can more smoothly enter the interior of the kudzu root cells, dissolve and leach out the active ingredients therein, greatly improving the extraction efficiency.

[0037] In Step 2, the pulverized kudzu root powder is fully mixed with an ethanol solution, and then continuously stirred for a certain time under specific temperature conditions to obtain a first treatment product. Ethanol is used as the extraction solvent. Most of the active ingredients such as flavonoid compounds in the kudzu root have a certain polarity, and ethanol is also a polar solvent. According to the principle of "like dissolves like", polar ethanol can better dissolve polar active ingredients. The stirring operation can make the kudzu root powder evenly disperse in the ethanol solution, avoiding the situation of too high or too low local concentration, ensuring the uniformity and stability of the extraction process, and enabling the active ingredients to be more fully transferred into the ethanol solution.

[0038] In Step 3, the first treatment product is filtered to remove the solid residues therein, thereby obtaining a first treatment solution. After the kudzu root powder is soaked in the ethanol solution, the solid parts such as undissolved fibers and cell wall fragments still remain solid, while the active ingredients have been dissolved in the ethanol solution to form a liquid mixture. Through filtration, a pure first treatment solution is obtained.

[0039] In Step 4, after adjusting the pH value of the first treatment solution to the appropriate range, glutathione S-transferase (GST) and metallothionein (MT) are added thereto, and a stirring reaction is carried out under specific temperature conditions. First of all, the pH value has a significant impact on the activity of biological enzymes. Different biological enzymes have the best catalytic activity within different pH ranges. These two enzymes, GST and MT, can maintain relatively high activity in an environment with a pH value of 7.0 - 7.5. Within this pH range, the spatial structure of the enzyme molecules is relatively stable, and the charge state and spatial conformation of the amino acid residues at the active center are conducive to binding with heavy metal ions. When the pH value deviates from this range, the structure of the enzyme molecules may change, resulting in a decrease or even inactivation of the activity. Secondly, glutathione S-transferase forms a stable complex with heavy metal ions (such as Pb 2+ , Cd 2+ , As 3+ ) through its sulfhydryl group (-SH). This is because the structure of the active center of GST matches the chemical properties of these heavy metal ions, and it can firmly bind the heavy metal ions to the enzyme molecules through specific interactions. Metallothionein is a protein rich in cysteine, and its sulfhydryl group (-SH) can also bind to various heavy metal ions (such as Pb 2+ , Cd 2+ , As 3+ ) to form metal-sulfur bonds. Stirring at a temperature of 36 - 38°C, on the one hand, this temperature is close to the optimal reaction temperature of these two enzymes. Within this temperature range, the catalytic activity of the enzymes is the highest, and they can bind to heavy metal ions more effectively; on the other hand, the stirring operation can make the enzymes evenly distributed in the solution, increase the contact opportunity between the enzymes and heavy metal ions, and promote the progress of the reaction, finally obtaining a second treatment product containing enzyme-heavy metal complexes.

[0040] In Step 5, activated carbon is added to the second treatment product, and continuous stirring is carried out at room temperature for a certain period of time to obtain a third treatment product. Activated carbon has strong adsorption properties and has physical and chemical adsorption functions. Physical adsorption is due to the rich pore structure on the surface of activated carbon. These pores provide a large specific surface area, enabling activated carbon to adsorb molecules or ions in the solution through van der Waals forces. The pore sizes on the surface of activated carbon are different, and it can adsorb substances of different sizes. For relatively large molecules such as enzyme-heavy metal complexes, activated carbon can capture and fix them through its pores. Chemical adsorption is that the functional groups (such as carboxyl groups, hydroxyl groups, etc.) on the surface of activated carbon react chemically with substances in the solution or form chemical bonds to achieve the adsorption of specific substances. In this process, activated carbon fixes and separates enzyme-heavy metal complexes through the synergistic effect of physical and chemical adsorption, and can also remove impurities such as pigments and odors in the extract, further improving the quality of the extract.

[0041] In Step 6, a second filtration operation is performed on the third processed material to effectively separate activated carbon and the enzyme-heavy metal complex from the extract, obtaining a second processed liquid. The principle of this step is similar to that of the first filtration, both separating based on the differences in physical state and particle size of substances. After the treatment of adding activated carbon in the previous step, the activated carbon and the enzyme-heavy metal complex exist in the solution in solid form, while the active ingredients in the extract remain dissolved in the liquid. Through the second filtration, impurities are further removed to obtain a purer second processed liquid, preparing for the subsequent concentration and drying operations.

[0042] In Step 7, the second processed liquid is subjected to concentration and drying treatment. The ethanol solvent is removed by vacuum concentration, and then it is transformed into powder form by methods such as freeze-drying or spray-drying. Vacuum concentration heats the solution under an environment below normal pressure, reducing the boiling point of the ethanol solvent, enabling it to evaporate into a gaseous state at a lower temperature and thus separating from the solution. This can avoid damaging the active ingredients in the Pueraria lobata extract during long-term heating at high temperatures and ensure the quality and activity of the extract. Freeze-drying first freezes the concentrated solution into a solid state, and then under low-temperature and low-pressure conditions, the solid water is directly sublimated into a gaseous state to remove the water, obtaining dry powder, which can maximize the retention of the active ingredients and biological activity in the extract, and at the same time the obtained powder has good stability and solubility. Spray-drying sprays the concentrated liquid into fine droplets through an atomizer, and the droplets quickly evaporate water during contact with hot air to form dry powder. Through concentration and drying, finally, Pueraria lobata extract powder is obtained, which is convenient for storage, transportation, and use.

[0043] In this application, by first crushing Pueraria lobata into powder to increase the contact area with the extraction solvent, then using an ethanol solution to extract the active ingredients, while ensuring a relatively high extraction efficiency, GST and MT are utilized to specifically bind heavy metal ions through reaction with heavy metals, and further heavy metals are removed by combining with activated carbon adsorption. Finally, heavy metals in the Pueraria lobata extract are removed through steps such as filtration and drying, avoiding the problems of loss of active ingredients and introduction of new impurities caused by the chemical precipitation method, with simple operation and effectively improving the efficiency of heavy metal removal.

[0044] In a possible implementation manner, in Step 1, the target particle size is 40 - 80 mesh.

[0045] Specifically, in step 1, if the target particle size is greater than 80 mesh, that is, the particles are too large, the contact area between kudzu root and the extraction solvent is limited, and the dissolution of active ingredients such as flavonoids is insufficient, which will reduce the extraction efficiency and result in insufficient content of active ingredients in the final extract. Moreover, the large-particle-size kudzu root powder is not conducive to the full contact between the enzyme and the substrate, and the enzymatic reaction is difficult to proceed efficiently, and the heavy metal removal effect will be reduced. If the particle size is less than 40 mesh, that is, the particles are too fine, although the contact area with the solvent is large in theory, in actual operation, the fine particles are prone to agglomeration, which may instead reduce the exposure opportunity of active ingredients and affect the extraction effect. During filtration, the too-fine particles may pass through the filter medium such as filter paper and mix into the extract, increasing the difficulty of subsequent separation and purification.

[0046] In a possible implementation manner, in step 2:

[0047] The concentration of the ethanol solution is 65% - 75%, the first temperature is 60 - 70 °C, and the first duration is 120 - 150 min.

[0048] Specifically, during the kudzu root extraction process, the ethanol solution concentration is set at 65% - 75%. On the one hand, this concentration range can enable ethanol molecules to form appropriate interactions with target components such as flavonoids in kudzu root. The polarity and solubility of ethanol molecules in this interval can effectively dissolve the target components from kudzu root cells, ensuring a high extraction rate. On the other hand, this concentration range can avoid damaging certain heat-sensitive and active components in kudzu root due to too high ethanol concentration, maintaining the biological activity and pharmacological efficacy of the extract; at the same time, it can also prevent incomplete extraction due to too low ethanol concentration, ensuring the quality of the extract. If the concentration is lower than 65%, the solubility is insufficient, and the active ingredients are difficult to be fully dissolved; if it is higher than 75%, it may damage the component structure and increase the subsequent processing cost.

[0049] The first temperature is controlled at 60 - 70 °C. If the temperature is lower than 60 °C, the activity of ethanol molecules is insufficient, the extraction speed is slow, and incomplete extraction may occur; if it is higher than 70 °C, it may damage heat-sensitive components such as flavonoids and biogenic amines, reducing the medicinal value and health care function of the extract.

[0050] The first duration is 120 - 150 minutes. Within this time range, the ethanol solution has sufficient time to fully penetrate into the interior of the kudzu root powder, making sufficient contact and undergoing dissolution reactions with the active ingredients therein. A duration of 120 - 150 minutes can enable the interaction between ethanol molecules and the target components to reach equilibrium, ensuring that important components such as flavonoid compounds are effectively extracted into the ethanol solution and improving the extraction rate. If the duration is less than 120 minutes, the contact between the ethanol solution and the kudzu root powder is insufficient, and some active ingredients may not be completely dissolved, affecting the extraction effect. If the duration exceeds 150 minutes, although the extraction effect may not be significantly improved, it will increase energy consumption and production cycle, raise production costs, and may also introduce unnecessary impurities.

[0051] In a possible implementation manner, in step 2: the mass ratio of the kudzu root powder to the ethanol solution is 1:12 - 15.

[0052] Specifically, in step 2, the mass ratio of the kudzu root powder to the ethanol solution is set to 1:12 - 15. Within this range, the ethanol solution can fully moisten the kudzu root powder, enabling efficient dissolution of active ingredients such as flavonoid compounds. If the mass ratio is lower than 1:12, that is, the ethanol solution is relatively less, it may cause the kudzu root powder to not be completely submerged and fully wetted, and some active ingredients are difficult to fully contact with ethanol molecules, thereby reducing the extraction efficiency. On the contrary, when the mass ratio is higher than 1:15, although the excessive ethanol solution can ensure complete immersion of the kudzu root powder, it may dilute the extract, increase the difficulty and cost of subsequent treatment steps such as concentration, and may also cause excessive dissolution of some impurities due to too much solvent, affecting the purity of the extract.

[0053] In a possible implementation manner, in step 4, the amount of glutathione S-transferase added to each 1 L of the first treatment solution is 15 - 25 U, and the amount of metallothionein added to each 1 L of the first treatment solution is 0.3 - 0.7 mg.

[0054] Specifically, when the amount of GST in every 1 L of the second treatment liquid is within the range of 15 - 25 U, it can not only ensure that there are enough enzyme active sites to bind heavy metal ions, but also avoid waste of resources or unnecessary influence on the extract due to excessive enzyme amount; when the amount of metallothionein is within the range of 0.3 - 0.7 mg, it can also ensure its effective binding with heavy metal ions and maintain an appropriate binding efficiency. If the amount of GST is less than 15 U, the active sites of the enzyme are relatively insufficient, and it may not be able to fully bind heavy metal ions, resulting in poor heavy metal removal effect; if it is higher than 25 U, not only the cost is increased, but also too much enzyme protein may be introduced, bringing difficulties to subsequent operations such as separation and purification. Similarly, if the amount of metallothionein is less than 0.3 mg, its ability to bind heavy metals is limited; if it is higher than 0.7 mg, it may also cause waste of resources and increase the complexity of subsequent treatment, thereby affecting the efficiency and effect of the entire extraction process.

[0055] In a possible implementation manner, in step 4, the first duration is 100 - 130 min.

[0056] Specifically, if the duration is less than 100 min, the reaction may not be complete, and some heavy metal ions may be processed in subsequent steps before they have time to fully bind with the enzyme, resulting in a decrease in the heavy metal removal rate and affecting the purity and quality of the extract. When the duration exceeds 130 min, although the heavy metal binding reaction can basically reach a high degree, the excessive time may introduce other unnecessary side reactions, such as the degradation of the enzyme protein itself or non-target reactions with other substances. At the same time, it also increases the time cost of the entire process and reduces the production efficiency. Therefore, the range of the first duration of 100 - 130 min can ensure the effective removal of heavy metals while taking into account the production efficiency and product quality.

[0057] In a possible implementation manner, in step 4, the temperature is controlled at 37 °C and the second duration is 120 min.

[0058] Specifically, from the perspective of enzymatic reaction, 37 °C is close to the physiological temperature in the organism, which can make both glutathione S-transferase and metallothionein participating in the reaction maintain the best active conformation, thereby ensuring that they can efficiently perform their respective functions and promote the reaction with heavy metal ions. The second duration is set to 120 min. Within this duration, enzymes and metallothionein etc. have sufficient time to form stable complexes and metal-sulfur bonds with heavy metal ions (such as Pb 2+ 、Cd 2+ 、As 3+ ), ensuring the effective removal of heavy metals.

[0059] In a possible implementation manner, in step 5, the second temperature is room temperature and the third duration is 50 - 80 min.

[0060] Specifically, the room temperature is generally 25°C. The room temperature condition is mild and easy to control, without the need for complex temperature control equipment, which reduces the operation cost. At the same time, it can ensure the stability and compatibility of bioactive substances such as enzymes participating in the reaction, avoiding enzyme inactivation and protein denaturation caused by too high temperature, or too slow reaction rate due to too low temperature, and ensuring the smooth progress of the reaction in a suitable environment. The third time period is set to 50 - 80 min, which not only ensures the full progress of the reaction and achieves the expected reaction effect, but also does not introduce unnecessary side reactions or increase the time cost due to too long time, thus achieving a good balance between ensuring the reaction quality and efficiency. The third time period is preferably 60 min.

[0061] In a possible implementation manner, the first filtration uses medium-speed qualitative filter paper.

[0062] Specifically, medium-speed qualitative filter paper is usually made of raw materials such as plant fibers, and has good adsorption and certain mechanical strength. Its filtration performance is between that of fast and slow qualitative filter papers, with a moderate pore size, which can effectively intercept and separate solid particles, colloids, and some larger suspended matters in the mixture while ensuring a certain filtration speed. In this application, after the kudzu root powder is mixed with the ethanol solvent, there may be some insoluble dietary fibers, undissolved starch granules, and other impurities in the kudzu root powder in the mixture system. If these substances are not removed by filtration, they may have an adverse impact on subsequent experimental steps or technological processes. Using medium-speed qualitative filter paper for filtration, from the perspective of filtration efficiency, the pore size of medium-speed qualitative filter paper can adapt to the characteristics of this mixture system, allowing the ethanol solvent and small molecule substances dissolved in it to pass through smoothly, and effectively intercepting insoluble solid particles and impurities. Compared with fast filter paper, it can filter out impurities more thoroughly and prevent impurities from entering subsequent steps with the filtrate; compared with slow filter paper, it can complete the filtration process within a reasonable time and will not extend the entire process cycle due to too slow filtration speed, improving work efficiency. From the perspective of chemical stability, medium-speed qualitative filter paper has good chemical inertness and will not react chemically with kudzu root powder, ethanol, and other possible components in the ethanol solvent environment, ensuring that the chemical properties of the mixture during filtration will not change due to the filter paper, ensuring the stability of the composition and properties of the filtrate, providing a reliable sample basis for various subsequent analyses and treatments based on the filtrate, ensuring the accuracy and reliability of experimental results, and enabling the entire scheme to proceed smoothly and achieve the expected effect.

[0063] In a possible implementation manner, the second filtration uses a microporous membrane with a pore size of 0.22 μm.

[0064] Specifically, the microfiltration membrane is a porous thin film filtration material with uniform pore size, and its pore size is usually between 0.1 micrometer and 10 micrometers. The specific pore size can be selected according to different application requirements. It is generally made of polymer materials such as polyethersulfone, polytetrafluoroethylene, nylon, etc., and has good chemical stability, thermal stability and mechanical strength. The microfiltration membrane can allow liquids or gases to pass through through physical sieving, while intercepting substances larger than the pore size such as solid particles, colloids, microorganisms, etc. In this application, after activated carbon adsorption treatment, there may be various impurities in the system, including heavy metal ions not completely adsorbed by activated carbon, tiny precipitates or enzyme-heavy metal complexes formed with heavy metal ions, and residual activated carbon particles, etc. The 0.22μm pore size microfiltration membrane can play an important role. First of all, this pore size can effectively intercept activated carbon particles. Activated carbon may form some fine aggregates or undissolved particles during the adsorption process, and the 0.22μm pore size can prevent these particles from entering the subsequent process and avoid causing pollution or interference to subsequent experimental or production links. At the same time, for tiny impurities such as enzyme-heavy metal complexes, this pore size can also effectively intercept them. The size of enzyme-heavy metal complexes is usually in the micrometer level, and the 0.22μm pore size can prevent them from flowing into the subsequent steps with the filtrate, thus ensuring the purity of the filtrate in the subsequent process; Secondly, the polymer material selected for the microfiltration membrane has good chemical inertness. When contacting with the mixed system containing heavy metal ions, it will not react chemically with heavy metal ions and other components, ensuring that during the filtration process, the existence state and distribution of heavy metals in the system will not be changed by the filter membrane, and the composition of the filtrate remains stable. Moreover, the 0.22μm pore size can maintain a relatively good filtration rate while ensuring the filtration effect. In actual heavy metal removal operations, it is usually necessary to process a relatively large amount of samples or solutions. If the pore size is too small, although impurities can be intercepted more thoroughly, it will cause the filtration process to be too slow, increasing the processing time and cost. The 0.22μm pore size can complete the filtration process within a reasonable time on the premise of effectively filtering impurities, improving the overall work efficiency.

[0065] Example 1

[0066] Step 1: Crush kudzu root to 40 mesh to obtain kudzu root powder.

[0067] Step 2: Weigh 100g of kudzu root powder, mix it with 750g of ethanol solution with a concentration of 65%, and stir at 60°C for 120 min to obtain the first treatment product.

[0068] Step 3: Use medium-speed qualitative filter paper to filter the first treatment product for the first time to obtain the first treatment solution with solid residues filtered out.

[0069] Step 4: Adjust the pH of the first treatment solution to 7.0. Add 15 U of glutathione S-transferase and 0.3 mg of metallothionein to 1 L of the first treatment solution, and stir at 36 °C for 100 min to obtain a second treatment product.

[0070] Step 5: Add activated carbon to the second treatment product, and stir at room temperature (25 °C) for 50 min to obtain a third treatment product.

[0071] Step 6: Filter the third treatment product through a microporous membrane with a pore size of 0.22 μm for the second time to obtain a second treatment solution.

[0072] Step 7: Remove the ethanol solvent from the second treatment solution by vacuum concentration, and then convert it into a powder by freeze-drying to obtain kudzu root extract powder.

[0073] Example 2

[0074] Step 1: Crush kudzu root into 60 mesh to obtain kudzu root powder.

[0075] Step 2: Weigh 100 g of kudzu root powder, mix it with 1250 g of ethanol solution with a concentration of 70%, and stir at 65 °C for 135 min to obtain a first treatment product.

[0076] Step 3: Filter the first treatment product through medium-speed qualitative filter paper for the first time to obtain a first treatment solution with solid residues filtered out.

[0077] Step 4: Adjust the pH of the first treatment solution to 7.2. Add 20 U of glutathione S-transferase and 0.5 mg of metallothionein to 1 L of the first treatment solution, and stir at 37 °C for 115 min to obtain a second treatment product.

[0078] Step 5: Add activated carbon to the second treatment product, and stir at room temperature (25 °C) for 65 min to obtain a third treatment product.

[0079] Step 6: Filter the third treatment product through a microporous membrane with a pore size of 0.22 μm for the second time to obtain a second treatment solution.

[0080] Step 7: Remove the ethanol solvent from the second treatment solution by vacuum concentration, and then freeze-dry it into a powder to obtain kudzu root extract powder.

[0081] Example 3

[0082] Step 1: Crush kudzu root into 80 mesh to obtain kudzu root powder.

[0083] Step 2: Weigh 100 g of kudzu root powder, mix it with 1500 g of ethanol solution with a concentration of 75%, and stir at 70 °C for 150 min to obtain a first treatment product.

[0084] Step 3: Filter the first processed material with medium-speed qualitative filter paper for the first time to obtain the first processed liquid with solid residues filtered out.

[0085] Step 4: Adjust the pH of the first processed liquid to 7.5, add 25 U of glutathione S-transferase and 0.7 mg of metallothionein to 1 L of the first processed liquid, and stir at 38 °C for 130 min to obtain the second processed material.

[0086] Step 5: Add activated carbon to the second processed material and stir at room temperature (25 °C) for 80 min to obtain the third processed material.

[0087] Step 6: Filter the third processed material with a microporous filter membrane with a pore size of 0.22 μm for the second time to obtain the second processed liquid.

[0088] Step 7: Remove the ethanol solvent from the second processed liquid by vacuum concentration, and then freeze-dry it into a powder to obtain the kudzu root extract powder.

[0089] Example 4

[0090] Step 1: Crush the kudzu root into 60 meshes to obtain kudzu root powder.

[0091] Step 2: Weigh 100 g of kudzu root powder, mix it with 1250 g of ethanol solution with a concentration of 70%, and stir at 65 °C for 135 min to obtain the first processed material.

[0092] Step 3: Filter the first processed material with medium-speed qualitative filter paper for the first time to obtain the first processed liquid with solid residues filtered out.

[0093] Step 4: Adjust the pH of the first processed liquid to 7.2, directly add activated carbon to 1 L of the first processed liquid, and stir at room temperature (25 °C) for 65 min to obtain the third processed material.

[0094] Step 5: Filter the third processed material with a microporous filter membrane with a pore size of 0.22 μm for the second time to obtain the second processed liquid.

[0095] Step 6: Remove the ethanol solvent from the second processed liquid by vacuum concentration, and then freeze-dry it to obtain the kudzu root extract powder.

[0096] Among them, Example 4 is a comparative example.

[0097] Experimental data

[0098] Experimental method: Use inductively coupled plasma mass spectrometry (ICP-MS) to measure the Pb, Cd, and As contents in the kudzu root extract powder in Examples 1-4 respectively.

[0099] Table 1 Heavy metal content data in kudzu root extract powder in Examples 1 to 4

[0100] Example Pb content (mg / kg) Cd content (mg / kg) As content (mg / kg) 1 0.12 0.08 0.05 2 0.08 0.05 0.03 3 0.06 0.04 0.02 4 0.25 0.15 0.12

[0101] It can be seen from the experimental data that the contents of Pb, Cd, and As in the kudzu root extract powder in Examples 1 to 3 all meet the limited values specified in the relevant national standards, while the heavy metals in Example 4 are relatively high. This indicates that the treatment method of first reacting GST and MT with heavy metals and then performing activated carbon adsorption in this solution can effectively reduce the heavy metal content in kudzu root powder to meet the safety standards. GST and MT have the ability to specifically bind heavy metal ions, which can fix heavy metal ions on enzyme or protein molecules, reducing the residue of heavy metals in the system. Activated carbon can further adsorb these complexes and other residual heavy metal ions, thereby achieving effective removal of heavy metals. In contrast, only activated carbon is used for adsorption in Example 4. Due to the lack of specificity of activated carbon adsorption, the removal effect on heavy metal ions is relatively poor, and the heavy metal content cannot be reduced to the standard range.

[0102] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for removing heavy metals from Pueraria lobata extract, characterized in that, Including: Step 1: Crush kudzu root to a target particle size to obtain kudzu root powder; Step 2: Mix the kudzu root powder with an ethanol solution and stir for a first duration at a first temperature to obtain a first treated product; Step 3: Filter the first treated product for the first time to obtain a first treated liquid with solid residues filtered out; Step 4: After adjusting the pH of the first treated liquid to 7.0 - 7.5, add glutathione S-transferase and metallothionein to the first treated liquid, control the temperature at 36 - 38 °C, and stir for a second duration to obtain a second treated product; Step 5: Add activated carbon to the second treated product and stir for a third duration at a second temperature to obtain a third treated product; Step 6: Filter the third treated product for the second time to obtain a second treated liquid; Step 7: Concentrate and dry the second treated liquid to obtain kudzu root extract powder.

2. The method for removing heavy metals from Pueraria lobata extract according to claim 1, characterized in that, In step 1, the target particle size is 40 - 80 mesh.

3. The method for removing heavy metals from Pueraria lobata extract according to claim 1, wherein In step 2: The concentration of the ethanol solution is 65% - 75%, the first temperature is 60 - 70 °C, and the first duration is 120 - 150 min.

4. The method for removing heavy metals from Pueraria lobata extract according to claim 3, wherein In step 2: The mass ratio of the kudzu root powder to the ethanol solution is 1:12 - 15.

5. The method for removing heavy metals from Pueraria lobata extract according to claim 1, characterized in that, In step 4, the amount of glutathione S-transferase added to each 1 L of the first treated liquid is 15 - 25 U, and the amount of metallothionein added to each 1 L of the first treated liquid is 0.3 - 0.7 mg.

6. The method for removing heavy metals from Pueraria lobata extract according to claim 1, wherein, In step 4, the second duration is 100 - 130 min.

7. The method for removing heavy metals from Pueraria lobata extract according to claim 6, characterized in that, In step 4, control the temperature at 37 °C and the second duration at 120 min.

8. The method for removing heavy metals from pueraria lobata extract according to claim 1, wherein In step 5, the second temperature is room temperature, and the third duration is 50 - 80 min.

9. The method for removing heavy metals from pueraria lobata extract according to claim 1, wherein The first filtration uses medium-speed qualitative filter paper.

10. The method for removing heavy metals from Pueraria lobata extract according to claim 1, characterized in that, The second filtration uses a microporous membrane with a pore size of 0.22 μm.

Images