A method of preparing a bacteriostatic herbal composition

Abstract

The present application relates to the field of bacteriostatic agents, and particularly relates to a preparation method of a bacteriostatic herbal composition. The preparation method of the bacteriostatic herbal composition comprises the following steps: mixing chicory extract, galangal extract, motherwort extract, thyme extract, emulsifier and ethanol to obtain core materials; mixing beta-cyclodextrin, tea polyphenol, tannic acid and water, and then adding into the core materials to perform homogenization to obtain an emulsion; adding sodium oxidized alginic acid into water to perform dispersion, and then adding into the emulsion to perform dispersion, adjusting pH to obtain a mixed system; adding mercapto chitosan into 0.1M acetic acid buffer solution at 4 DEG C, and then adding into the mixed system to perform crosslinking to obtain an intermediate; mixing the intermediate, octenyl succinic anhydride, emulsifier and ethanol, performing solidification, and then continuing spray drying to obtain the bacteriostatic herbal composition. The bacteriostatic herbal composition provided by the present application has high activity, high stability and low toxicity.

Description

Technical Field

[0001] This invention relates to the field of antibacterial agents, and more specifically, to a method for preparing an antibacterial herbal composition. Background Technology

[0002] Currently, microbial contamination and pathogen invasion are widespread problems in agricultural plant protection, public environmental disinfection, and skin care, significantly impacting plant health, biosafety, and human quality of life. Traditional antimicrobial control methods mainly rely on chemically synthesized fungicides or antibiotics. While these methods offer some short-term effectiveness, they suffer from numerous drawbacks, including increased resistance, environmental residues, ecotoxicity, and effects on non-target organisms. Therefore, developing novel, green, safe, broad-spectrum antimicrobial materials with good environmental adaptability has become an important direction for current research and application.

[0003] In recent years, antibacterial systems developed based on natural products have gradually attracted attention. Natural active substances are widely available, possess multi-site and multi-target antibacterial mechanisms, can effectively reduce the emergence of drug-resistant strains, and are environmentally friendly and biodegradable, showing great application potential. However, natural antibacterial components often suffer from high volatility, poor stability, and low bioavailability, limiting their widespread application and sustained efficacy in practical situations.

[0004] To address the aforementioned issues, there is a need to provide an antibacterial combination structure and its preparation method that is process-controllable, has stable activity, a broad antibacterial spectrum, and is suitable for agricultural and environmental applications. Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for preparing an antibacterial herbal composition composed of various Chinese herbal extracts. This method can efficiently extract and retain the active ingredients of plants, and improve their stability and sustained-release performance through cyclodextrin inclusion technology and biopolymer cross-linking and solidification technology, thereby obtaining a natural antibacterial composition with high activity, high stability and low toxicity.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] This invention provides a method for preparing an antibacterial herbal composition, comprising the following steps:

[0008] S1. Chicory extract, galangal extract, motherwort extract, thyme extract, first emulsifier and ethanol are mixed to obtain the core material;

[0009] S2. Mix β-cyclodextrin, tea polyphenols, tannic acid and water to obtain a mixed solution; add the mixed solution to the core material and homogenize to obtain an emulsion;

[0010] S3. Add sodium alginate oxide to water and disperse it. After dispersion, add it to the emulsion for further dispersion and adjust the pH to obtain a mixed system. Add thiolated chitosan to a 0.1M acetate buffer solution at 4°C and then add it to the mixed system for cross-linking to obtain an intermediate.

[0011] S4. Mix the intermediate, octenyl succinic anhydride, second emulsifier and ethanol, cure, and then continue spray drying to obtain the antibacterial herbal composition.

[0012] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, step S1, the method for preparing the chicory extract includes the following steps:

[0013] Chicory stems were dried, crushed, and sieved to obtain pretreated chicory stems. The pretreated chicory stems were then soaked in an ethanol-water solution and subjected to sonication. After sonication, the resulting product was filtered, evaporated, and dried sequentially to obtain chicory extract.

[0014] The ratio of chicory stem to ethanol aqueous solution is 1g: 10-20mL;

[0015] The volume ratio of ethanol to water in the ethanol-water solution is 7:3;

[0016] The ultrasound conditions are: frequency 40kHz, power 300W, temperature <50℃, and time 30min.

[0017] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, step S1, the method for preparing the galangal extract includes the following steps:

[0018] The rhizomes of Alpinia galanga were dried, crushed, and sieved to obtain pretreated Alpinia galanga rhizomes. The pretreated Alpinia galanga rhizomes were mixed with an ethanol aqueous solution and refluxed. The resulting product was concentrated and then mixed with petroleum ether for extraction. Finally, the product was obtained by rotary evaporation and vacuum drying to obtain Alpinia galanga extract.

[0019] The ratio of the amount of Alpinia galanga rhizome to the ethanol aqueous solution is 1g: 10-20mL;

[0020] The volume ratio of ethanol to water in the ethanol-water solution is 7:3;

[0021] The reflux temperature is 80°C, and the reflux time is 2 hours.

[0022] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, step S1, the method for preparing the motherwort extract includes the following steps:

[0023] The whole herb of Leonurus japonicus was dried, crushed, and sieved to obtain pretreated whole herb. The pretreated whole herb of Leonurus japonicus was mixed with an ethanol aqueous solution and refluxed. The resulting product was concentrated and allowed to stand. Finally, it was dried to obtain Leonurus japonicus extract.

[0024] The ratio of the whole motherwort herb to the ethanol aqueous solution is 1g: 10-20mL;

[0025] The volume ratio of ethanol to water in the ethanol-water solution is 6.5:3.5;

[0026] The reflux temperature is 80°C, and the reflux time is 2 hours.

[0027] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, step S1, the method for preparing the thyme extract includes the following steps:

[0028] The whole thyme herb was dried, crushed and sieved to obtain pretreated whole thyme herb; the pretreated whole thyme herb was mixed with water and refluxed, sodium chloride was added to the product until saturated, ethyl acetate was added and the mixture was extracted and separated by reverse extraction, and then dried to obtain thyme extract.

[0029] The ratio of the whole thyme herb to water is 1g: 5-10mL;

[0030] The reflux temperature is 100°C, and the reflux time is 2 hours.

[0031] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, in step S1, the mass ratio of chicory extract, galangal extract, motherwort extract, and thyme extract is (1.2-1.8):(0.8-1.2):(0.6-1.0):(1.5-2.5);

[0032] In step S1, the mass ratio of the chicory extract, the first emulsifier, and ethanol is (1.2–1.8) g : (0.12–0.18) g : (10–20) mL;

[0033] In step S1, the first emulsifier includes Tween-80.

[0034] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, the mixing process includes:

[0035] First, mix and disperse the first emulsifier with 70% of the volume of ethanol in the formula. Then, add the chicory extract, galangal extract, and motherwort extract for dispersion. Finally, add the thyme extract and disperse it in the dark at 25°C. Finally, add the remaining ethanol for dispersion.

[0036] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, in step S2, the mass ratio of β-cyclodextrin, tea polyphenols, tannic acid and water is (4.5-5.5):(0.8-1.2):(0.15-0.25):(45-55);

[0037] In step S2, the mass ratio of the β-cyclodextrin to the core material is (4.5-5.5):(4-5);

[0038] In step S2, the homogenization conditions are: pressure of 18-22 MPa, time of 8-12 min, and temperature of 20-30 °C.

[0039] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, step S2, the mixing step, includes:

[0040] β-cyclodextrin and water were mixed and dispersed at 55°C, cooled to 30°C, and tea polyphenols and tannic acid were added. The mixture was then dispersed in the dark under nitrogen protection.

[0041] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, in step S3, the mass ratio of oxidized sodium alginate, thiolated chitosan, and water is 1:(1.1-1.3):(95-105);

[0042] The mass ratio of sodium alginate oxide in step S3 to the core material in step S2 is 1:(2-10);

[0043] In step S3, the oxidation degree of the oxidized sodium alginate is 50% to 60%.

[0044] In step S3, the degree of thiolation of the thiolated chitosan is 30% to 40%.

[0045] In step S3, the target value of pH is 5.5;

[0046] In step S3, the crosslinking temperature is 23-27°C, and the crosslinking time is 80-100 min.

[0047] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, step S3 specifically includes:

[0048] Sodium oxidized alginate was added to water at 4°C for dispersion, and then added to an emulsion for further dispersion. The pH was adjusted to obtain a mixed system. Thiolized chitosan was added to a 0.1M acetate buffer solution at 4°C, and then added to the mixed system for cross-linking.

[0049] The ratio of the amount of thiolated chitosan to the acetate buffer solution is (1.1-1.3) g: (45-60) mL.

[0050] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, in step S4, the mass ratio of the intermediate, octenyl succinic anhydride, second emulsifier and ethanol is 10g:(0.45-0.55)g:(0.08-0.12)g:(14-16)mL;

[0051] In step S4, the second emulsifier includes Tween-80.

[0052] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, in step S4, the curing temperature is 58-62°C and the curing time is 25-35 min;

[0053] In step S4, the spray drying conditions are as follows: inlet air temperature is 130-140℃, outlet air temperature is 65-75℃, and pressure is 0.28-0.32MPa.

[0054] Preferably, in the above-mentioned method for preparing an antibacterial herbal composition, step S4, the mixing process includes:

[0055] Octenyl succinic anhydride and 70% by volume of ethanol were mixed and dispersed to obtain a mixed solution; the intermediate and the remaining 30 wt% of ethanol were mixed and dispersed, then a second emulsifier was added, and the mixed solution was added and dispersed in an ice bath at 0-5°C.

[0056] The beneficial technical effects of the present invention through the above technical solution are as follows:

[0057] (1) Chicory extract is rich in chicoric acid and flavonoids, galangal extract contains volatile oils and curcumin, motherwort contains alkaloids and sterols, and thyme is rich in thymol and linalool. These components have a synergistic effect in antibacterial mechanisms, interfering with bacterial cell membrane structure, protein synthesis, and metabolic pathways, thereby showing significant inhibitory effects on Gram-positive bacteria (such as Staphylococcus aureus) and fungi (such as the pathogen of melon wilt). Among them, the combination of thyme extract and chicory extract has a synergistic enhancing effect on plant pathogens, significantly expanding the antibacterial spectrum and improving the antibacterial intensity.

[0058] (2) This invention utilizes the synergistic effect of β-cyclodextrin with tea polyphenols and tannic acid, possessing excellent encapsulation ability and antioxidant properties. This effectively stabilizes and slowly releases volatile and heat-sensitive components from plant extracts, preventing their degradation during storage and application. Then, through covalent cross-linking between the aldehyde groups in oxidized sodium alginate and the thiol groups in thiolated chitosan, a stable gel microparticle is formed within the initially encapsulated emulsion, enhancing the composition's retention capacity and bioavailability in the plant rhizosphere environment, thus strengthening its sustained efficacy in agricultural disease prevention. Furthermore, octenyl succinic anhydride further cross-links with the exposed hydroxyl or amino groups on the intermediate surface, forming a hydrophobic protective shell on the carrier particle surface. This delays release while retaining the active substances, improving its UV resistance and degradation resistance in natural soil or plant surface environments. This dual encapsulation system is significantly superior to traditional physical mixing formulations.

[0059] (3) The antibacterial herbal composition has a concentrated particle size distribution (180-200 nm), and the powder particles after spray drying are uniform, stable in color, and without obvious agglomeration. After 90 days of storage, the particle size and antibacterial activity change little, indicating that the composition has good physical stability and functional durability, and is suitable for long-term transportation and storage.

[0060] (4) The raw materials used are non-toxic and harmless, environmentally friendly, and can replace chemical pesticides for agricultural disease control, seed treatment or horticultural plant protection. Moreover, due to its multi-pathway synergistic antibacterial mechanism, it is not easy to induce pathogens to develop drug resistance. Detailed Implementation

[0061] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0062] Preparation Example 1

[0063] Fresh chicory stems were dried in hot air at 45℃ for 24 hours, then pulverized and passed through a 60-mesh sieve. The pulverized stems were added to a mixed solution of ethanol / water at a ratio of 1g:15mL, and the mixture was ultrasonically treated (frequency 40kHz, power 300W, temperature controlled below 45℃) for 30 minutes. The resulting mixture was filtered, concentrated by vacuum evaporation, and dried under vacuum to obtain the chicory extract.

[0064] Preparation Example 2

[0065] The dried galangal rhizomes were pulverized and passed through a 60-mesh sieve. They were then added to a 7:3 ethanol / water mixture at a ratio of 1 g:15 mL and extracted under reflux at 80°C for 2 h. The resulting extract was concentrated under reduced pressure and extracted three times with an equal volume of petroleum ether. The combined organic phases were then rotary evaporated and dried under vacuum to obtain the galangal extract.

[0066] Preparation Example 3

[0067] After pulverizing and sieving the dried whole motherwort herb, add it to an ethanol / water solution of 6.5:3.5 at a ratio of 1g:15mL and reflux for 2 hours. Concentrate the resulting extract, allow it to stand, precipitate out, and dry to obtain the motherwort extract.

[0068] Preparation Example 4

[0069] The dried whole thyme herb was mixed with water at a ratio of 1g:8mL and extracted by reflux at 100℃ for 2h. After filtration, sodium chloride was added until saturation, and then the mixture was extracted three times by reverse extraction with ethyl acetate. The organic layer was separated and dried under low temperature vacuum to obtain the thyme extract.

[0070] Example 1

[0071] A method for preparing an antibacterial herbal composition includes the following steps:

[0072] 10.5 mL of anhydrous ethanol and 0.15 g of Tween-80 were added to a 25°C light-protected reactor and dispersed. Then, 1.5 g of chicory extract, 1.0 g of galangal extract, and 0.8 g of motherwort extract were added and dispersed in sequence. Then, 2.0 g of thyme extract was added and dispersed at 25°C in the dark. Finally, 4.5 mL of anhydrous ethanol was added and dispersed to obtain the core material.

[0073] Add 5g of β-cyclodextrin to 50mL of deionized water at 55℃, stir and disperse, cool to 30℃, then add 1g of tea polyphenols and 0.2g of tannic acid, disperse under nitrogen protection in the dark to obtain a mixed solution; then add 4.5g of core material dropwise to the mixed solution at 1mL / min for dispersion, and homogenize at 20MPa and 25℃ to obtain an emulsion;

[0074] 1g of oxidized sodium alginate (oxidation degree of 50%) was added to 100mL of deionized water and dispersed. After dispersion, it was added to the emulsion (containing 4.5g of core material) and dispersed again. The pH was adjusted to 5.5 to obtain a mixed system. 1.2g of thiolated chitosan (thiolation degree of 30%) was dispersed in 50mL of 4℃ acetate buffer (0.1M, pH 5.5) and magnetically stirred for 30min. The resulting product was added dropwise to the mixed system at 0.5mL / min and crosslinked at 25℃ for 80min to obtain an intermediate.

[0075] 0.5 g of octenyl succinic anhydride was dispersed in 10.5 mL of anhydrous ethanol and cooled to 4 °C to obtain a mixed solution. 10 g of the intermediate was mixed and dispersed with 4.5 mL of ethanol at 4 °C, and then 0.1 Tween-80 was added. The mixture was stirred in an ice bath at 0 °C and added dropwise at 0.5 mL / min. Crosslinking was then carried out at 60 °C for 30 min. Finally, spray drying was performed with an inlet air temperature of 135 °C, an outlet air temperature of 70 °C, and a pressure of 0.30 MPa to obtain an antibacterial herbal composition.

[0076] Example 2

[0077] A method for preparing an antibacterial herbal composition includes the following steps:

[0078] 7.0 mL of anhydrous ethanol and 0.12 g of Tween-80 were added to a 25°C, light-protected reactor and dispersed. Then, 1.2 g of chicory extract, 0.8 g of galangal extract, and 0.6 g of motherwort extract were added and dispersed in sequence. 1.5 g of thyme extract was added and the mixture was dispersed at 25°C in the dark. Finally, 3.0 mL of anhydrous ethanol was added and dispersed to obtain the core material.

[0079] 4.5 g of β-cyclodextrin was added to 45 mL of deionized water at 55 °C and stirred to disperse. After cooling to 30 °C, 0.8 g of tea polyphenols and 0.15 g of tannic acid were added and dispersed under nitrogen protection in the dark. 4.0 g of core material was added dropwise at 1 mL / min for dispersion. After dispersion, the mixture was homogenized at 18 MPa and 20 °C for 12 min to obtain an emulsion. 1 g of oxidized sodium alginate (oxidation degree 50%) was added to 95 mL of deionized water and dispersed. After dispersion, it was added to the emulsion (containing 4.0 g of core material) and the pH was adjusted to 5.5. 1.1 g of thiolated chitosan (thiolation degree 30%) was dispersed in 45 mL of acetate buffer (0.1 M, pH 5.5) at 4 °C and added dropwise to the mixture at 0.3 mL / min. The mixture was crosslinked at 23 °C for 100 min to obtain an intermediate.

[0080] 0.45 g of octenyl succinic anhydride was dispersed in 7.0 mL of anhydrous ethanol and cooled to 4 °C. 10 g of the intermediate was mixed with 3.0 mL of ethanol at 4 °C, and 0.08 g of Tween-80 was added. The mixture was added dropwise at 0.5 mL / min in an ice bath at 0 °C. The mixture was crosslinked at 58 °C for 35 min and then spray-dried (inlet air 130 °C, outlet air 65 °C, pressure 0.28 MPa) to obtain the antibacterial herbal composition.

[0081] Example 3

[0082] A method for preparing an antibacterial herbal composition includes the following steps:

[0083] 14.0 mL of anhydrous ethanol and 0.18 g of Tween-80 were added to a 25°C, light-protected reactor and dispersed. Then, 1.8 g of chicory extract, 1.2 g of galangal extract, and 1.0 g of motherwort extract were added and dispersed in sequence. 2.5 g of thyme extract was added and the mixture was dispersed at 25°C in the dark. Finally, 6.0 mL of anhydrous ethanol was added and dispersed to obtain the core material.

[0084] Add 5.5g of β-cyclodextrin to 55mL of deionized water at 55℃, stir and disperse, cool to 30℃, then add 1.2g of tea polyphenols and 0.25g of tannic acid, and disperse under nitrogen protection in the dark; add 5.0g of core material dropwise at 1mL / min for dispersion, and homogenize at 22MPa and 30℃ for 8min to obtain an emulsion;

[0085] 1 g of oxidized sodium alginate (oxidation degree 60%) was dispersed in 105 mL of deionized water, and then added to the emulsion (containing 5.0 g of core material) and the pH was adjusted to 5.5. 1.3 g of thiolated chitosan (thiolation degree 40%) was dispersed in 60 mL of 4℃ acetate buffer (0.1 M, pH 5.5) and added dropwise to the mixture at 0.8 mL / min. The mixture was crosslinked at 27℃ for 80 min to obtain the intermediate.

[0086] 0.55 g of octenyl succinic anhydride was dispersed in 10.5 mL of anhydrous ethanol and cooled to 4 °C. 10 g of the intermediate was mixed with 4.5 mL of ethanol at 4 °C, and 0.12 g of Tween-80 was added. The mixture was added dropwise at 0.5 mL / min in an ice bath at 0 °C. The mixture was crosslinked at 62 °C for 25 min and then spray-dried (inlet air 140 °C, outlet air 75 °C, pressure 0.32 MPa) to obtain the antibacterial herbal composition.

[0087] Comparative Example 1

[0088] A method for preparing an antibacterial herbal composition includes the following steps:

[0089] 10.5 mL of anhydrous ethanol and 0.15 g of Tween-80 were added to a 25°C light-protected reactor and dispersed. Then, 1.5 g of chicory extract, 1.0 g of galangal extract, and 0.8 g of motherwort extract were added and dispersed in sequence. Then, 2.0 g of thyme extract was added and dispersed at 25°C in the dark. Finally, 4.5 mL of anhydrous ethanol was added and dispersed to obtain the core material.

[0090] 1g of oxidized sodium alginate (oxidation degree of 50%) was added to 100mL of deionized water and dispersed. After dispersion, it was added to 4.5g of core material and dispersed again. The pH was adjusted to 5.5 to obtain a mixed system. 1.2g of thiolated chitosan (thiolation degree of 30%) was dispersed in 50mL of 4℃ acetate buffer (0.1M, pH 5.5) and magnetically stirred for 30min. The resulting product was added dropwise to the mixed system at 0.5mL / min and crosslinked at 25℃ for 80min to obtain an intermediate.

[0091] 0.5 g of octenyl succinic anhydride was dispersed in 10.5 mL of anhydrous ethanol and cooled to 4 °C to obtain a mixed solution. 10 g of the intermediate was mixed and dispersed with 4.5 mL of ethanol at 4 °C, and then 0.1 Tween-80 was added. The mixture was stirred in an ice bath at 0 °C and added dropwise at 0.5 mL / min. Crosslinking was then carried out at 60 °C for 30 min. Finally, spray drying was performed with an inlet air temperature of 135 °C, an outlet air temperature of 70 °C, and a pressure of 0.30 MPa to obtain an antibacterial herbal composition.

[0092] Comparative Example 2

[0093] A method for preparing an antibacterial herbal composition includes the following steps:

[0094] 10.5 mL of anhydrous ethanol and 0.15 g of Tween-80 were added to a 25°C light-protected reactor and dispersed. Then, 1.5 g of chicory extract, 1.0 g of galangal extract, and 0.8 g of motherwort extract were added and dispersed in sequence. Then, 2.0 g of thyme extract was added and dispersed at 25°C in the dark. Finally, 4.5 mL of anhydrous ethanol was added and dispersed to obtain the core material.

[0095] Add 5g of β-cyclodextrin to 50mL of deionized water at 55℃, stir and disperse, cool to 30℃, then add 1g of tea polyphenols and 0.2g of tannic acid, disperse under nitrogen protection in the dark to obtain a mixed solution; then add 4.5g of core material dropwise to the mixed solution at 1mL / min for dispersion, and homogenize at 20MPa and 25℃ to obtain an emulsion;

[0096] 1g of oxidized sodium alginate (oxidation degree of 50%) was added to 100mL of deionized water and dispersed. After dispersion, it was added to the emulsion (containing 4.5g of core material) and dispersed again. The pH was adjusted to 5.5 to obtain a mixed system. 1.2g of thiolated chitosan (thiolation degree of 30%) was dispersed in 50mL of 4℃ acetate buffer (0.1M, pH 5.5) and magnetically stirred for 30min. The resulting product was added dropwise to the mixed system at 0.5mL / min and crosslinked at 25℃ for 80min. Finally, it was spray-dried at an inlet air temperature of 135℃, an outlet air temperature of 70℃, and a pressure of 0.30MPa to obtain an antibacterial herbal composition.

[0097] Comparative Example 3

[0098] The method for preparing a herbal antibacterial composition differs from that in Example 1 in that:

[0099] Chicory extract is not available.

[0100] Everything else is the same as in Example 1.

[0101] Comparative Example 4

[0102] The method for preparing a herbal antibacterial composition differs from that in Example 1 in that:

[0103] Thyme extract is not available.

[0104] Everything else is the same as in Example 1.

[0105] Performance testing

[0106] 1. The herbal antibacterial compositions of the examples and comparative examples were stored at 25°C and 60% humidity for 3 months, and the changes in color, particle size, and antibacterial activity were observed. The particle size was measured using Zetasizer, and the changes in the inhibition zone were measured using S. aureus as a model strain. The results are shown in Table 1.

[0107] Table 1

[0108]

[0109] As shown in Table 1, the particle size increase in the Example group was only 7-8 nm after 90 days, while that in the comparative example was 65-89 nm. The appearance of the Example group was basically stable (no precipitation / browning), while the comparative example 4 (lacking thyme) showed severe browning, indicating that thyme extract is crucial for stability. The inhibition zone of the Example group shrank by ≤1.2 mm, while that of the comparative example shrank by ≥4.2 mm, demonstrating that the antibacterial herbal composition provided by this invention can maintain its antibacterial effect for a long time.

[0110] 2. Antibacterial rate

[0111] On PDA plates, half were cultured with the pathogenic fungus of melon wilt (0.5 cm diameter mycelial cake), and the other half were placed with 0.01 g of the herbal antibacterial composition powder prepared in the examples and comparative examples, respectively. The plates were incubated at 28℃ for 3 days, and the inhibition rate was measured. Inhibition rate = (colon diameter of control group ~ colony diameter of treatment group) / colony diameter of control group × 100%.

[0112] 0.01 g of the herbal antibacterial composition powder prepared in the examples and comparative examples was placed in seedling trays inoculated with melon wilt disease, buried 1 cm around the roots, and the inhibition rate was measured after 7 days; the total number of inoculated plants in this experiment was 90. Inhibition rate = (total number of inoculated plants - number of diseased plants) / total number of inoculated plants × 100%.

[0113] In greenhouses where melons were infected with Fusarium wilt, 0.01g of the herbal antibacterial composition powder prepared in the examples and comparative examples was placed around the infected plants at a depth of 2-3cm. The inhibition rate was measured after 10 days. The total number of infected plants in this experiment was 30. Inhibition rate = (total number of infected plants - surviving plants) / total number of infected plants × 100%. The test results are shown in Table 2.

[0114] Table 2

[0115]

[0116] As shown in Table 2, the antibacterial herbal composition in the examples exhibited an antibacterial rate >83% in all scenarios, while the antibacterial rate in the comparative examples was less than 75%. This indicates that the antibacterial herbal composition provided by the present invention is highly effective and stable in inhibiting bacteria, and is suitable for field application.

[0117] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing an antibacterial herbal composition, characterized in that, Includes the following steps: S1. Chicory extract, galangal extract, motherwort extract, thyme extract, first emulsifier and ethanol are mixed to obtain the core material; S2. Mix β-cyclodextrin, tea polyphenols, tannic acid and water to obtain a mixed solution; add the mixed solution to the core material and homogenize to obtain an emulsion; S3. Add sodium alginate oxide to water and disperse it. After dispersion, add it to the emulsion for further dispersion and adjust the pH to obtain a mixed system. Add thiolated chitosan to a 4°C, 0.1M acetate buffer solution and then add it to the mixed system for cross-linking to obtain an intermediate. S4. Mix the intermediate, octenyl succinic anhydride, second emulsifier and ethanol, cure, and then continue spray drying to obtain the antibacterial herbal composition; In step S1, the mass ratio of chicory extract, galangal extract, motherwort extract, and thyme extract is (1.2-1.8):(0.8-1.2):(0.6-1.0):(1.5-2.5). In step S1, the mass ratio of the chicory extract, the first emulsifier, and water is (1.2–1.8):(0.12–0.18):(4–6); In step S2, the mass ratio of β-cyclodextrin, tea polyphenols, tannic acid and water is (4.5-5.5):(0.8-1.2):(0.15-0.25):(45-55); In step S2, the mass ratio of the β-cyclodextrin to the core material is (4.5-5.5):(4-5); In step S3, the mass ratio of oxidized sodium alginate, thiolated chitosan, and water is 1:(1.1-1.3):(95-105); In step S3, the mass ratio of the oxidized sodium alginate to the core material in step S2 is 1:(2-10); In step S4, the mass ratio of the intermediate, octenyl succinic anhydride, second emulsifier and ethanol is 10:(0.45-0.55):(0.08-0.12):(14-16).

2. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S1, the method for preparing the chicory extract includes the following steps: Chicory stems were dried, crushed, and sieved to obtain pretreated chicory stems. The pretreated chicory stems were then soaked in an ethanol-water solution and subjected to sonication. After sonication, the resulting product was filtered, evaporated, and dried sequentially to obtain chicory extract. The ratio of chicory stem to ethanol aqueous solution is 1g: 10-20mL; The volume ratio of ethanol to water in the ethanol-water solution is 7:3; The ultrasound conditions are: frequency 40kHz, power 300W, temperature <50°C, and time 30min.

3. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S1, the preparation method of the galangal extract includes the following steps: The rhizomes of Alpinia galanga were dried, crushed, and sieved to obtain pretreated Alpinia galanga rhizomes. The pretreated Alpinia galanga rhizomes were mixed with an ethanol aqueous solution and refluxed. The resulting product was concentrated and then mixed with petroleum ether for extraction. Finally, the product was obtained by rotary evaporation and vacuum drying to obtain Alpinia galanga extract. The ratio of the amount of Alpinia galanga rhizome to the ethanol aqueous solution is 1g: 10-20mL; The volume ratio of ethanol to water in the ethanol-water solution is 7:3; The reflux temperature is 80°C, and the reflux time is 2 hours.

4. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S1, the preparation method of the motherwort extract includes the following steps: The whole herb of Leonurus japonicus was dried, crushed, and sieved to obtain pretreated whole herb of Leonurus japonicus. The pretreated whole herb of Leonurus japonicus was mixed with an ethanol aqueous solution and refluxed. The resulting product was concentrated and allowed to stand. Finally, it was dried to obtain Leonurus japonicus extract. The ratio of the whole motherwort herb to the ethanol aqueous solution is 1g: 10-20mL; The volume ratio of ethanol to water in the ethanol-water solution is 6.5:3.5; The reflux temperature is 80°C, and the reflux time is 2 hours.

5. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S1, the preparation method of the thyme extract includes the following steps: The whole thyme herb was dried, crushed and sieved to obtain pretreated whole thyme herb; the pretreated whole thyme herb was mixed with water and refluxed, sodium chloride was added to the product until saturated, ethyl acetate was added and the mixture was extracted and separated by reverse extraction, and then dried to obtain thyme extract. The ratio of the whole thyme herb to water is 1g: 5-10mL; The reflux temperature is 100°C, and the reflux time is 2 hours.

6. The method for preparing the antibacterial herbal polymer according to claim 1, characterized in that, In step S1, the first emulsifier includes Tween-80.

7. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S2, the homogenization conditions are: pressure of 18-22 MPa, time of 8-12 min, and temperature of 20-30°C.

8. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S3, the target value of pH is 5.5; In step S3, the crosslinking temperature is 23–27°C, and the crosslinking time is 80–100 min.

9. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S4, the second emulsifier includes Tween-80.

10. The method for preparing the antibacterial herbal composition according to claim 1, characterized in that, In step S4, the curing temperature is 58–62°C and the curing time is 25–35 min; in step S4, the spray drying conditions are: inlet air temperature is 130–140°C, outlet air temperature is 65–75°C, and pressure is 0.28–0.32 MPa.

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