Preparation method of a laponite-based nanocomposite antibacterial material

Abstract

The application discloses a preparation method of a hectorite-based nanometer composite antibacterial material, which comprises the following steps: firstly, uniformly mixing hectorite, zinc nitrate and copper nitrate by stirring; secondly, further uniformly mixing the mixture by spraying a certain amount of water; thirdly, sequentially performing sealing aging, three-roller rolling and calcination; fourthly, dispersing the material in a plant extract solution for modification treatment; and finally, obtaining the nanometer composite antibacterial material through pressure filtration, drying and grinding. The nanometer composite antibacterial material has high charge separation efficiency and strong antibacterial activity to gram-negative bacteria and gram-positive bacteria, and more importantly, has strong antibacterial capacity to drug-resistant bacteria; as a broad-spectrum antibacterial agent, the nanometer composite antibacterial material can be applied to the fields of rubber, plastic, paint and daily-use chemical industry.

Description

Technical Field

[0001] This invention relates to the field of functional materials preparation technology, specifically to a method for preparing an antibacterial material, particularly a lithium saponite-based nanocomposite antibacterial material and its preparation method, which uses synthetic lithium saponite as a substrate, loads zinc-copper bimetallic oxides and is surface-modified. Background Technology

[0002] Bacterial infections and the resulting biosafety issues continue to be a concern in the medical, consumer goods, and public environments. The overuse of traditional antibiotics has led to increasing bacterial resistance, making the development of novel non-antibiotic antibacterial agents an important research direction. Among these, inorganic antibacterial agents (such as ZnO, CuO, and Ag nanoparticles) have been widely studied and applied in various materials due to their high heat resistance, good stability, and low tendency to induce resistance, thus imparting durable antibacterial properties to the substrate.

[0003] However, current inorganic antibacterial agents still face several problems in practical applications: First, single inorganic nanoparticles (such as ZnO or CuO) have a relatively narrow antibacterial spectrum, and their inhibitory effect on certain bacterial species (especially drug-resistant bacteria) is limited. Moreover, their antibacterial activity is greatly affected by particle size, dispersion state and photogenerated charge separation efficiency.

[0004] Second, nanoparticles have a large specific surface area and high surface energy, making them prone to aggregation during preparation and storage, which leads to a decrease in effective specific surface area and a reduction in active sites, thereby weakening their antibacterial properties.

[0005] Third, when inorganic nanoparticles are directly blended with polymer substrates (such as rubber, plastics, and coatings), problems such as poor interfacial compatibility and uneven dispersion occur, which affect the mechanical properties and durability of the antibacterial effect of the product.

[0006] Fourth, some highly efficient inorganic antibacterial agents (such as nano-silver) are expensive and pose potential risks of biotoxicity and environmental release, which limits their large-scale application in certain fields.

[0007] To overcome the aforementioned problems, researchers have begun to focus on developing composite antibacterial materials. For example, using nanocarriers to load antibacterial components has become an effective strategy. Lithium saponite, a synthetically produced layered silicate clay mineral, possesses excellent ion exchange capacity, high specific surface area, and colloidal stability, making it an ideal nanocarrier. Existing technologies have already attempted to prepare antibacterial materials by loading single metal ions or nanoparticles onto lithium saponite.

[0008] For example, prior art document 1 (CN202411408890.X) discloses a lithium saponite composite antibacterial and antioxidant hydrogel, which uses lithium saponite as a physical crosslinking agent to composite with zwitterionic monomers and loads EGCG-Cu nanocomplexes, ultimately applied to wound dressings. This technology mainly focuses on the biomedical field, solving the problems of mechanical properties, adhesion, and biocompatibility of hydrogels. Its process route (polymerization, impregnation) and target product (hydrogel) are fundamentally different from the powder materials and industrial substrates involved in this invention.

[0009] For example, prior art document 2 (CN108102152B) discloses a lithium saponite-immobilized nano-silver / chitosan antibacterial composite membrane, which uses lithium saponite to immobilize nano-silver and then forms a film with chitosan for use in food packaging. This technology focuses on preventing nano-silver leakage and reducing toxicity. Its core antibacterial component is nano-silver, and the final product is a membrane material. Its preparation method (microwave reduction, dialysis film formation) and application field (food contact materials) are different from those of this invention.

[0010] While existing technologies have demonstrated the potential of lithium saponite as a carrier, developing an inorganic antibacterial powder that can be widely applied to hydrophobic or polar polymer industrial substrates such as rubber, coatings, and plastics, possessing efficient, broad-spectrum, and long-lasting antibacterial properties, while also being cost-effective and processable, remains a pressing technical challenge in this field. In particular, how to simultaneously load and stabilize multiple active components with synergistic antibacterial effects on lithium saponite through innovative material design and process combinations, and further improve its compatibility and dispersibility with industrial substrates, has not yet been effectively reported.

[0011] This invention addresses the shortcomings of the prior art by proposing a new solution. Summary of the Invention

[0012] To address the problems of narrow antibacterial spectrum, easy aggregation, poor compatibility with industrial substrates, high cost, or potential toxicity associated with single inorganic antibacterial agents in existing technologies, this invention provides a method for preparing lithium saponite-based nanocomposite antibacterial materials. This invention aims to prepare an inorganic antibacterial functional powder that possesses highly efficient broad-spectrum antibacterial activity, excellent dispersion stability, good substrate compatibility, and controllable cost through a unique combination of material design and processes.

[0013] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a lithium saponite-based nanocomposite antibacterial material includes the following steps: Mixing: A certain proportion of lithium saponite, zinc nitrate and copper nitrate are stirred and mixed evenly in a mixing hopper to obtain a mixed powder; Aging: A certain amount of water is sprayed into the mixture under continuous stirring. After stirring for 2 hours, the mixture is discharged and then sealed for aging for 24 hours to obtain the aging precursor. Three-roller process: The aged precursor is subjected to three-roller pressing to obtain sheet material; Calcination: After drying the flaky material, place it in a muffle furnace and keep it at a certain temperature for 2-6 hours; Modification: After the furnace temperature drops to room temperature, the material is dispersed in an aqueous solution of plant extract, stirred continuously for 4 hours, then filtered and dehydrated, dried at 60-90℃ for 6-12 hours, and then ground through a 200-mesh sieve to obtain a lithium saponite-based nanocomposite antibacterial material powder.

[0014] Furthermore, the mass ratio of the specified lithium saponite, zinc nitrate, and copper nitrate is 7:2:1.

[0015] Furthermore, the lithium saponite is a homogenized and peeled lithium saponite nanosheet, and zinc nitrate and copper nitrate refer to zinc nitrate hexahydrate and copper nitrate hexahydrate.

[0016] Furthermore, the aforementioned "certain amount of water" refers to water comprising 10% to 20% of the total mass fraction of the mixture of lithium saponite, zinc nitrate, and copper nitrate.

[0017] Furthermore, the three-roll processing refers to a process that can be repeated 3 to 6 times.

[0018] Furthermore, the aforementioned "certain temperature" refers to a muffle furnace temperature of 350–400°C.

[0019] Furthermore, the amount of the aqueous solution of the plant extract is 70-90% of the mass fraction of the mixture of lithium saponite, zinc nitrate and copper nitrate.

[0020] Furthermore, the plant extract in the aqueous solution is selected from one or more of the following: Sapindus mukorossi, Angelica sinensis, Codonopsis pilosula, Lonicera japonica, Astragalus membranaceus, and Glycyrrhiza uralensis.

[0021] Furthermore, the plant extract refers to the mixture of plant material and solvent at a solid-liquid ratio of 1:10, stirred continuously at room temperature for 10 hours, and then separated.

[0022] Compared with existing technologies, the lithium saponite-based nanocomposite antibacterial material prepared by this invention possesses high efficiency and broad spectrum, strong anti-drug-resistant bacterial activity, excellent dispersion stability, and good compatibility with various industrial polymer substrates. Specifically: First, by simultaneously loading ZnO and CuO nanoparticles with synergistic antibacterial effects onto lithium saponite nanosheets in situ, and supplementing with surface modification, efficient separation of photogenerated charges and strong inhibition and killing of Gram-negative bacteria, Gram-positive bacteria, and even drug-resistant bacteria are achieved, resulting in a broad antibacterial spectrum and high activity. Second, the "three-roll homogenization-calcination" process effectively prevents the aggregation of nanoparticles, improving the dispersibility of active components and charge separation efficiency. Third, coating with a specific surface modifier enhances the antibacterial activity of the material. In addition, the entire preparation process uses water as the main medium, with mild conditions, a simple process, and controllable raw material costs, possessing the potential for green and large-scale production. Attached Figure Description

[0023] Figure 1 This is a digital photograph of the three-roll sheet obtained after three-roll processing in Embodiment 4 of the present invention.

[0024] Figure 2 This is a transmission electron microscope (TEM) image of the nanosheets obtained after the lithium saponite raw material used in the embodiments of the present invention has undergone exfoliation treatment.

[0025] Figure 3 This is a TEM image of the pure ZnO nanoparticles obtained in Comparative Example 1 of this invention.

[0026] Figure 4 This is a TEM image of the pure CuO nanoparticles obtained in Comparative Example 2 of this invention.

[0027] Figure 5 This is a TEM image of the lithium saponite / zinc-copper oxide composite material obtained in Example 4 of the present invention.

[0028] Figure 6 The photocurrent density test results are those of the lithium saponite / zinc-copper oxide composite material obtained in the embodiments of the present invention.

[0029] Figure 7 This is a TEM image of the lithium saponite-based nanocomposite antibacterial material obtained in Example 4 of the present invention.

[0030] Figure 8 This is a photograph showing the test results of the antibacterial performance of ZnO nanoparticles obtained in Comparative Example 1 against Escherichia coli.

[0031] Figure 9 This is a photograph showing the test results of the antibacterial properties of CuO nanoparticles obtained in Comparative Example 2 against Escherichia coli and Staphylococcus aureus.

[0032] Figure 10These are photographs showing the test results of the antibacterial performance of the lithium saponite / zinc-copper oxide composite materials obtained in Examples 1-4 of this invention against Escherichia coli.

[0033] Figure 11 These are photographs showing the test results of the antibacterial performance of the lithium saponite / zinc-copper oxide composite materials obtained in Examples 1-4 of this invention against Staphylococcus aureus.

[0034] Figure 12 These are photographs showing the test results of the antibacterial performance of the lithium saponite-based nanocomposite antibacterial materials obtained in Examples 1-4 of this invention against Escherichia coli.

[0035] Figure 13 These are photographs showing the test results of the antibacterial performance of the lithium saponite-based nanocomposite antibacterial materials obtained in Examples 1-4 of this invention against Staphylococcus aureus.

[0036] Figure 14 The lithium saponite-based nanocomposite antibacterial material obtained in Example 4 of this invention exhibits resistance to ultra-broad spectrum... β - Photographs showing the antibacterial performance test results of lactamase-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0038] The key to the method provided by this invention lies in achieving uniform loading and stable composite of zinc and copper oxides on lithium saponite nanosheets through a specific "mixing-aging-three-roll calcination-modification" process route, and further combining it with surface modification of plant extract aqueous solution to obtain lithium saponite-based nanocomposite antibacterial material powder with excellent performance.

[0039] To facilitate comparison and explanation of the effectiveness of the present invention, a comparative sample was first prepared.

[0040] Comparative Example 1: Preparation of pure ZnO nanoparticles Zinc nitrate hexahydrate was sprayed with 16% water (by mass), sealed, aged, and formed into thin sheets using a three-roll mill. After drying at 80°C, it was calcined in a muffle furnace at 400°C for 2 hours. After the furnace temperature dropped to room temperature, the material was removed, ground into powder, and passed through a 200-mesh sieve for later use.

[0041] Comparative Example 2: Preparation of Pure CuO Nanoparticles Copper nitrate hexahydrate was sprayed with 16% water by mass, sealed, aged, and formed into thin sheets using a three-roller process. After drying at 80°C, it was calcined in a muffle furnace at 400°C for 2 hours. After the furnace temperature dropped to room temperature, the material was removed, ground into powder, and passed through a 200-mesh sieve for later use.

[0042] The present invention will be further illustrated below through specific embodiments.

[0043] Example 1 Lithium saponite, zinc nitrate, and copper nitrate in a 7:2:1 ratio were stirred and mixed evenly in a mixing hopper to obtain a mixed powder. Water at a mass fraction of 20% was sprayed into the mixture under continuous stirring for 2 hours, and then discharged. The mixture was then sealed and aged for 24 hours to obtain an aging precursor. The aging precursor was fed into a three-roll mill for six roll pressing processes to obtain sheet material. The sheet material was dried and then placed in a muffle furnace at 400℃ for 2 hours. After the furnace temperature dropped to room temperature, the material was dispersed in an aqueous solution of Angelica sinensis extract at a mass fraction of 70% (lithium saponite, zinc nitrate, and copper nitrate). After continuous stirring for 4 hours, the mixture was pressure filtered and dehydrated. After drying at 90℃ for 6 hours, it was ground through a 200-mesh sieve to obtain a lithium saponite-based nanocomposite antibacterial material powder.

[0044] Example 2 Lithium saponite, zinc nitrate, and copper nitrate in a 7:2:1 ratio were stirred and mixed evenly in a mixing hopper to obtain a mixed powder. Water (10% by mass) was sprayed into the mixture under continuous stirring for 2 hours, and then discharged. The mixture was then sealed and aged for 24 hours to obtain an aging precursor. The aging precursor was fed into a three-roll mill for four roll pressing processes to obtain sheet material. The sheet material was dried and then placed in a muffle furnace at 350°C for 3 hours. After the furnace temperature dropped to room temperature, the material was dispersed into an aqueous solution of honeysuckle extract (80% by mass of lithium saponite, zinc nitrate, and copper nitrate), stirred continuously for 4 hours, and then dehydrated by pressure filtration. After drying at 70°C for 10 hours, the material was ground through a 200-mesh sieve to obtain a lithium saponite-based nanocomposite antibacterial material powder.

[0045] Example 3 Lithium saponite, zinc nitrate, and copper nitrate in a 7:2:1 ratio were stirred and mixed evenly in a mixing hopper to obtain a mixed powder. Water with a mass fraction of 14% was sprayed into the mixture under continuous stirring for 2 hours, and then discharged. The mixture was then sealed and aged for 24 hours to obtain an aging precursor. The aging precursor was fed into a three-roll mill for three rolling processes to obtain sheet material. The sheet material was dried and then placed in a muffle furnace at 380℃ for 6 hours. After the furnace temperature dropped to room temperature, the material was dispersed into an aqueous solution of Sapindus mukorossi extract with a mass fraction of 85% (lithium saponite, zinc nitrate, and copper nitrate). After continuous stirring for 4 hours, the mixture was dehydrated by pressure filtration, dried at 60℃ for 12 hours, and then ground through a 200-mesh sieve to obtain a lithium saponite-based nanocomposite antibacterial material powder.

[0046] Example 4 Lithium saponite, zinc nitrate, and copper nitrate in a 7:2:1 ratio were stirred and mixed evenly in a mixing hopper to obtain a mixed powder. Water with a mass fraction of 16% was sprayed into the mixture under continuous stirring for 2 hours, and then discharged. The mixture was then sealed and aged for 24 hours to obtain an aging precursor. The aging precursor was fed into a three-roll mill for five roll pressing processes to obtain sheet material. The sheet material was dried and then placed in a muffle furnace at 400℃ for 4 hours. After the furnace temperature dropped to room temperature, the material was dispersed into a licorice extract aqueous solution containing 90% lithium saponite, zinc nitrate, and copper nitrate by mass. After continuous stirring for 4 hours, the mixture was pressure filtered and dehydrated. After drying at 80℃ for 8 hours, it was ground through a 200-mesh sieve to obtain a lithium saponite-based nanocomposite antibacterial material powder.

[0047] The products of the above embodiments and comparative examples were characterized structurally and their performance was evaluated. 1. Structural Morphology Analysis Figure 1 The image shows the state of the material after three-roll processing in Example 4. As can be seen from the photograph, under the condition of a controlled system moisture content of 16%, the three-roll pressing yielded thin, uniform, and distinctly curled sheet-like material. This indicates that the components (nitrate and lithium saponite nanosheets) achieved good mixing, wetting, and stretching under suitable humidity through mechanical force, laying the foundation for uniform reaction and loading during the subsequent calcination process.

[0048] Figure 2 These are transmission electron microscopy (TEM) images of the lithium saponite raw materials used in all embodiments of the present invention after three-roll processing. The images clearly show that the original lithium saponite flakes have been effectively exfoliated, forming a large number of dispersed nanosheets, including both single-layer nanosheets and a small number of multilayer stacked structures. This highly dispersed nanosheet carrier has a large specific surface area and abundant surface active sites, which is a prerequisite for efficiently loading active components.

[0049] Figure 3 and Figure 4 TEM images of single-component nanoparticles prepared in Comparative Examples 1 and 2, respectively. Figure 3 The results show that the pure ZnO nanoparticles have an uneven size distribution, with a particle size of about 10 nm, and there is obvious aggregation between the particles. Figure 4 The results show that pure CuO nanoparticles are smaller (approximately 2 nm), but exhibit equally severe aggregation. This confirms the common problem of easy aggregation of inorganic nanoparticles mentioned in the background section, which leads to a reduction in active surface area and affects their composite properties with the substrate.

[0050] Figure 5 This is a TEM image of the lithium saponite / zinc-copper oxide obtained in Example 3. Figure 3 ,4 As can be seen from the comparison, after adopting the "three-roll homogenization-calcination shaping" process of this invention, small (nanoscale) ZnO and CuO nanoparticles (bright white spots in the figure) were successfully and relatively uniformly loaded onto the surface and edges of lithium saponite nanosheets (grayish-black sheet-like substrate). This structure effectively utilizes the spatial confinement effect of the carrier, inhibits the excessive growth and aggregation of nanoparticles, and forms a stable nanocomposite structure.

[0051] Figure 6 The photocurrent density test results of the lithium saponite / zinc-copper oxide composite material obtained in the examples are shown. The comparison shows that the photocurrent density of the nano-ZnO obtained in Comparison 1 is lower, indicating its low photogenerated charge efficiency. The introduction of binary zinc-copper oxide and the lithium saponite support significantly improves the photogenerated charge separation efficiency of the composite material, further demonstrating the advantages of constructing nanocomposite antibacterial materials based on lithium saponite support using zinc-copper oxide, effectively improving the interfacial charge separation efficiency and thus enhancing the antibacterial activity of the composite material. The comparison also shows that the lithium saponite / zinc-copper oxide obtained in Example 4 has the highest charge separation efficiency.

[0052] Figure 7 This is a TEM image of the lithium saponite-based nanocomposite antibacterial material finally obtained in Example 4. (Comparison) Figure 5 It can be observed that a thin film-like substance is coated around the lithium saponite / zinc-copper oxide composite material (indicated by the arrow in the figure). This confirms that the surface modifier (natural plant extract) was successfully coated on the surface of the lithium saponite composite substrate loaded with zinc-copper oxide, forming a ternary structure of "lithium saponite carrier-metal oxide-organic modification layer".

[0053] Antibacterial performance evaluation Antimicrobial testing was performed using colony counting. The tested bacteria included Gram-negative bacteria (e.g., Escherichia coli) and Gram-positive bacteria (e.g., Staphylococcus aureus). The antimicrobial resistance was assessed using a broad-spectrum antimicrobial method. β - Lactamase-lactamase-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus.

[0054] Figure 8 and Figure 9 The antibacterial results of Comparative Example 1 (pure ZnO) and Comparative Example 2 (pure CuO) are presented respectively. Figure 8 This indicates that pure ZnO nanoparticles exhibit a certain inhibitory effect on Escherichia coli. However, Figure 9 The results showed that, at the same test concentration, pure CuO nanoparticles had a weak inhibitory effect on both test bacteria, and did not produce a significant killing effect. This illustrates the limitations of the performance of a single antibacterial component.

[0055] Figure 10 and Figure 11The antibacterial properties of four different ratios of lithium saponite / zinc-copper oxide composite materials (without surface modification) prepared in Examples 1-4 of this invention are demonstrated. Figure 10 It is evident that all four lithium saponite / zinc-copper oxide composite materials exhibited a certain inhibitory effect on Escherichia coli, but the reduction in colonies was limited. This indicates that the antibacterial performance was improved by relying solely on the synergistic loading of zinc and copper oxides, but the improvement was not significant. Figure 11 The study showed a similar trend in the lithium saponite / zinc-copper oxide composite material against Staphylococcus aureus, indicating that the composite material exhibited certain antibacterial activity.

[0056] Figure 13 and Figure 14 This demonstrates the antibacterial properties of the lithium saponite-based nanocomposite antibacterial material obtained after surface modification, with significantly different results. Figure 13 The results showed that the antibacterial ability of the four lithium saponite-based nanocomposite antibacterial materials against Escherichia coli was significantly enhanced, and compared with... Figure 11 In comparison, the number of colonies was significantly reduced, especially in the sample of Example 4, where colony growth was almost completely inhibited. Figure 14 The results were even more striking; all lithium saponite-based nanocomposite antibacterial materials exhibited extremely significant bactericidal effects against Staphylococcus aureus. Most importantly, the sample in Example 4, even at a relatively low contact concentration (0.5 mg / mL), was still able to completely kill Staphylococcus aureus in the culture medium, demonstrating extremely strong antibacterial efficacy.

[0057] Figure 14 The lithium saponite-based nanocomposite antibacterial material obtained in Example 4 of this invention exhibits resistance to ultra-broad spectrum... β The antibacterial properties of the composite material against *Escherichia coli* and methicillin-resistant *Staphylococcus aureus* were shown in the figure. As can be seen from the figure, the number of colonies at the tested concentration was significantly reduced compared with the blank control group, indicating that the composite material exhibited excellent antibacterial activity against the two drug-resistant bacteria.

[0058] The above verification of effects and analysis of the accompanying drawings, combined with specific embodiments, fully demonstrate the technical chain of this invention from material design and preparation to performance optimization, confirming that the method and the obtained materials of this invention possess outstanding innovation and practicality.

Claims

1. A method for preparing a lithium saponite-based nanocomposite antibacterial material, characterized in that, Includes the following steps: S1. Mixing: A certain proportion of lithium saponite, zinc nitrate and copper nitrate are stirred and mixed evenly in a mixing hopper to obtain a mixed powder; S2. Aging: A certain amount of water is sprayed into the mixture under continuous stirring. After stirring for 2 hours, the mixture is discharged and then sealed for 24 hours to obtain the aging precursor. S3, Three-roller: The aged precursor is subjected to three-roller pressing to obtain thin sheet material; S4. Calcination: After drying the sheet material, place it in a muffle furnace at a certain temperature and keep it for 2-6 hours. S5. Modification: After the furnace temperature drops to room temperature, the material is dispersed in an aqueous solution of plant extract, stirred continuously for 4 hours, then filtered and dehydrated, dried at 60-90℃ for 6-12 hours, and then ground through a 200-mesh sieve to obtain a lithium saponite-based nanocomposite antibacterial material powder.

2. The preparation method according to claim 1, characterized in that, In step S1, the certain ratio refers to the mass ratio of lithium saponite, zinc nitrate, and copper nitrate being 7:2:

1.

3. The preparation method according to claim 1 or 2, characterized in that, In step S1, the lithium saponite is lithium saponite nanosheets after homogenization and peeling, and zinc nitrate and copper nitrate refer to zinc nitrate hexahydrate and copper nitrate hexahydrate.

4. The preparation method according to claim 1 or 2, characterized in that, In step S2, the certain amount of water refers to water accounting for 10% to 20% of the mass fraction of the mixture of lithium saponite, zinc nitrate, and copper nitrate.

5. The preparation method according to claim 1 or 2, characterized in that, In step S3, the three-roll processing refers to repeating the process 3 to 6 times.

6. The preparation method according to claim 1 or 2, characterized in that, In step S4, the certain temperature refers to the muffle furnace temperature of 350-400℃.

7. The preparation method according to claim 1 or 2, characterized in that, In step S5, the amount of the plant extract aqueous solution used is 70-90% of the mass fraction of the mixture of lithium saponite, zinc nitrate and copper nitrate.

8. The preparation method according to claim 7, characterized in that, In step S5, the plant extract in the aqueous solution of the plant extract is selected from one or more of the following: Sapindus mukorossi, Angelica sinensis, Codonopsis pilosula, Lonicera japonica, Astragalus membranaceus, and Glycyrrhiza uralensis.

9. The preparation method according to claim 8, characterized in that, In step S5, the plant extract refers to the mixture of plant material and solvent at a solid-liquid ratio of 1:10, stirred continuously at room temperature for 10 hours, and then separated.

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