A preparation process and application of a 24-epibrassinolide soluble concentrate

Abstract

This invention provides a preparation process and application of a 24-epibrassinolide soluble concentrate. The raw materials for the soluble concentrate include: 5-10 parts of a loading agent, 0.001-1 parts of 24-epibrassinolide, 0.05-1 parts of plant essential oil, 1-2 parts of an antioxidant, 1-3 parts of a surfactant, 2-5 parts of an antifreeze agent, and 50-100 parts of water. This invention uses 24-epibrassinolide as the active ingredient to promote cucumber growth. Simultaneously, the introduction of essential oil and the loading agent HMS-PEGDMA into the soluble concentrate, used synergistically with 24-epibrassinolide, not only better promotes cucumber rooting and growth but also improves the control effect of the soluble concentrate against cucumber powdery mildew. Furthermore, the prepared soluble concentrate exhibits good UV stability.

Description

Technical Field

[0001] This invention relates to the field of pesticide technology, and in particular to a preparation process and application of a 24-epibrassinolide soluble concentrate. Background Technology

[0002] Cucumber (Cucumas sativus L.), also known as gourd cucumber, is an annual vegetable. Cucumbers have excellent nutritional value, offering benefits such as relieving heat and swelling, quenching thirst, and aiding weight loss. Their crisp texture and rich nutritional content make them a popular and indispensable part of people's daily diet. With the improvement of living standards and increased health awareness, the demand for cucumbers is constantly increasing. Cucumber cultivation has a long history in my country and has now become an important vegetable crop. With the continuous development of agricultural technology, cucumber cultivation techniques have been continuously improved, resulting in significant increases in both yield and quality.

[0003] Although cucumber cultivation techniques have greatly improved, some challenges still exist in actual production. Cucumbers are susceptible to various diseases during their growth, such as powdery mildew and downy mildew. These diseases not only affect cucumber yield and quality but also increase farmers' production costs. Therefore, effectively controlling cucumber diseases is a significant challenge. Furthermore, with constantly changing market demands, the requirements for cucumber varieties are continuously increasing. Developing higher-quality, higher-yielding, and disease-resistant cucumber varieties to meet people's needs for healthy eating is an important task at present.

[0004] 24-Epibrassinolide, also known as brassinolide or brassinolide, is a plant growth regulator widely found in plants. It promotes plant growth and development, increasing crop yield and quality, and is therefore frequently used in agricultural production. 24-Epibrassinolide increases chlorophyll content in leaves, improves photosynthetic efficiency, promotes cell division and elongation, enhances crop resistance, and makes crops grow more vigorously. Simultaneously, it improves crop quality, increases the content of sugars, vitamins, and other nutrients in fruits, promotes fruit growth and development, and makes fruits fuller and more uniform.

[0005] CN115152767A discloses a pesticide formulation containing 24-epibrassinolide and gibberellic acid, its preparation method, and its application. This invention uses a composition of tert-butylhydroquinone, ascorbic acid, and phytic acid as a stabilizer and optimizes the stabilizer's component ratio to significantly prevent the hydrolysis of 24-epibrassinolide and gibberellic acid, reducing the amount of organic solvent used. This invention not only significantly reduces production costs but is also more environmentally friendly. Furthermore, this invention applies the provided pesticide formulation of 24-epibrassinolide and gibberellic acid to reduce the rate of cucumber deformities in the field, effectively reducing the production of deformed cucumbers and increasing their commercial value.

[0006] CN111449070A discloses a compound plant growth regulator, its preparation method, and its application. The raw materials for preparing the compound plant growth regulator include 0.001-1 parts of brassinolide, 0.001-1 parts of dihydroporphyrin iron, and 0.01-10 parts of triacontanol. This invention combines the growth regulator brassinolide with dihydroporphyrin iron and triacontanol respectively, allowing each drug to exert a synergistic effect, effectively promoting the growth and development of vegetable crops (cucumber, pepper, or tomato) and the absorption and transport of nutrients, accelerating crop maturity, and significantly improving color, sugar content, and appearance gloss. This invention not only improves crop yield and quality but also has the advantages of good environmental compatibility, rapid efficacy, easy degradation, and no residual pollution, meeting the requirements of green and environmentally friendly pesticide development. Summary of the Invention

[0007] This invention provides a preparation process and application of 24-epibrassinolide soluble concentrate. By rationally proportioning the raw material components, this invention fully leverages the synergistic effect of each raw material, resulting in a 24-epibrassinolide soluble concentrate that effectively promotes cucumber growth and controls cucumber powdery mildew. Furthermore, the prepared soluble concentrate exhibits excellent UV stability.

[0008] One objective of this invention is to provide a preparation process for a soluble 24-epibrassinolide, comprising the following preparation steps: 24-Epibrassinolide, antioxidant, surfactant, water and antifreeze are mixed and stirred at a stirring speed of 150-300 r / min for 1.5-2 h until a transparent homogeneous solution is formed, which yields 24-epibrassinolide soluble agent. Alternatively, 24-epibrassinolide, plant essential oil, antioxidant, surfactant, water and antifreeze are mixed and stirred at a stirring speed of 150-300 r / min for 1.5-2 h until a transparent homogeneous solution is formed, thus obtaining a soluble form of 24-epibrassinolide.

[0009] Preferably, the weight ratio of each raw material component is as follows: 24-Epibrassinolide 0.001-1 part, antioxidant 1-2 parts, surfactant 1-3 parts, antifreeze 2-5 parts, water 50-100 parts; Alternatively, 0.001-1 part of 24-epibrassinolide, 0.05-1 part of plant essential oil, 1-2 parts of antioxidant, 1-3 parts of surfactant, 2-5 parts of antifreeze, and 50-100 parts of water.

[0010] More preferably, the antifreeze is at least one selected from glycerol, propylene glycol, ethylene glycol, and glycerin.

[0011] More preferably, the surfactant is at least one selected from calcium dodecylbenzenesulfonate, sodium carboxymethyl cellulose, sulfonyl chloride, calcium lignin sulfonate, nonylphenol polyoxyethylene aldehyde, and styrylphenol polyoxyethylene ether.

[0012] More preferably, the antioxidant is tocopherol.

[0013] More preferably, the plant essential oil is one of oregano essential oil, lemon essential oil, and thyme essential oil.

[0014] Preferably, the preparation steps of the 24-epibrassinolide soluble concentrate can further include: 24-Epibrassinolide, plant essential oil, antioxidant, surfactant, water, loading agent and antifreeze are mixed and stirred at a stirring speed of 150-300 r / min for 1.5-2 h until a transparent homogeneous solution is formed, thus obtaining 24-epibrassinolide soluble agent.

[0015] Preferably, the weight ratio of each raw material component is as follows: The mixture contains 5-10 parts of loading agent, 0.001-1 part of 24-epibrassinolide, 0.05-1 part of plant essential oil, 1-2 parts of antioxidant, 1-3 parts of surfactant, 2-5 parts of antifreeze, and 50-100 parts of water. More preferably, the loaded agent is an HMS-PEGDMA composite material.

[0016] More preferably, the preparation steps of the loaded drug are as follows: S1. Dissolve polyvinylpyrrolidone in water, add styrene under a nitrogen atmosphere, and stir to obtain an emulsion; heat the emulsion in an oil bath to 60-80℃, add an aqueous solution of 2,2'-azobis(2-methylpropanediamine) dihydrochloride, and stir to obtain a mixture; stir the mixture at 60-80℃ under a nitrogen atmosphere for 22-24 hours to obtain polystyrene latex. S2. Mix water, hexadecyltrimethylammonium bromide, ethanol, and ammonium hydroxide solution, add the polystyrene latex obtained in step S1 above, and mix evenly to obtain mixture A; ultrasonically treat mixture A at an ultrasonic power of 450-600W and an ultrasonic frequency of 25-30kHz for 2-3 hours, then stir for 30-40 minutes, and then add tetraethyl orthosilicate dropwise to obtain mixture B; place mixture B at room temperature for 45-50 hours, centrifuge, wash the solid product, and calcine the product at 600-650℃ for 8-10 hours to obtain hollow mesoporous silica nanoparticles, abbreviated as HMS; S3. Mix the HMS obtained in step S2 above, toluene and 3-aminopropyltriethoxysilane, and stir at 100-120℃ for 24-25h under nitrogen atmosphere. After the reaction is completed, cool to room temperature, centrifuge, wash the solid product, vacuum dry, and dry at 50-60℃ for 6-8h to obtain HMS-NH2. S4. Add the HMS-NH2 obtained in step S3 above to dichloromethane and ultrasonically disperse it for 1-2 hours at an ultrasonic power of 450-600W and an ultrasonic frequency of 25-30kHz to obtain a suspension. Add trimethylamine to the suspension, cool to 0-5℃, and then add a dichloromethane solution of 2-bromoisobutyryl bromide dropwise. Mix and stir to obtain a mixture. Stir the mixture in an ice bath for 2-3 hours, then transfer it to room temperature and continue stirring for 24-25 hours. Centrifuge to collect the precipitate, vacuum dry it, and dry it at 50-60℃ for 6-8 hours to obtain HMS-NH-Br. S5. Mix HMS-NH-Br, ethylene glycol dimethacrylate and cyclohexanone obtained in step S4 above, add a mixture of copper bromide, N,N,N',N",N"-pentamethyldiethylenetriamine and cyclohexanone under a nitrogen atmosphere, stir at 90-100℃ for 6-8h, centrifuge, wash the solid product, vacuum dry, and dry at room temperature for 6-8h to obtain the loaded reagent HMS-PEGDMA.

[0017] More preferably, the preparation steps of the loaded drug are as follows, where all parts are parts by weight: S1. Dissolve 0.2-0.3 parts of polyvinylpyrrolidone in 150-160 parts of water, add 15-18 parts of styrene under a nitrogen atmosphere, stir and mix to obtain an emulsion; heat the emulsion in an oil bath to 60-80℃, add 2-4 parts of an aqueous solution of 2,2'-azobis(2-methylpropanediamine) dihydrochloride, mix and stir to obtain a mixture; stir the mixture at 60-80℃ under a nitrogen atmosphere for 22-24 hours to obtain polystyrene latex; S2. Mix 4.5-5 parts water, 0.4-0.5 parts hexadecyltrimethylammonium bromide, 5.5-6 parts anhydrous ethanol and 1-2 parts ammonium hydroxide solution, add 25-30 parts of the polystyrene latex obtained in step S1 above, mix evenly to obtain mixture A; treat mixture A with ultrasonic power of 450-600W and ultrasonic frequency of 25-30kHz for 2-3 hours, stir for 30-40 minutes, then add 1.5-2 parts tetraethyl orthosilicate dropwise to obtain mixture B; place mixture B at room temperature for 45-50 hours, centrifuge, wash the solid product, and calcine the product at 600-650℃ for 8-10 hours to obtain HMS; S3. Mix 1-2 parts of HMS obtained in step S2 above, 200-250 parts of toluene and 5-8 parts of 3-aminopropyltriethoxysilane, stir at 100-120℃ for 24-25h under nitrogen atmosphere, cool to room temperature after the reaction is completed, centrifuge, wash the solid product, vacuum dry, and dry at 50-60℃ for 6-8h to obtain HMS-NH2. S4. Add 0.1-0.2 parts of HMS-NH2 obtained in step S3 above to 20-30 parts of dichloromethane, and ultrasonically disperse for 1-2 hours at an ultrasonic power of 450-600W and an ultrasonic frequency of 25-30kHz to obtain a suspension; add 0.3-0.4 parts of trimethylamine to the suspension, cool to 0-5℃, and then add 10-15 parts of a dichloromethane solution of 2-bromoisobutyryl bromide dropwise. After the addition is complete, mix and stir to obtain a mixture; stir the mixture in an ice bath for 2-3 hours, then transfer it to room temperature and continue stirring for 24-25 hours; collect the precipitate by centrifugation, vacuum dry it, and dry it at 50-60℃ for 6-8 hours to obtain HMS-NH-Br; S5. Mix 0.1-0.2 parts of HMS-NH-Br obtained in step S4 above, 1.5-2 parts of ethylene glycol dimethacrylate and 2-4 parts of cyclohexanone. Under a nitrogen atmosphere, add 0.1-0.2 parts of copper bromide, 0.2-0.3 parts of N,N,N',N",N"-pentamethyldiethylenetriamine and 1-2 parts of cyclohexanone. Then stir at 90-100℃ for 6-8h, centrifuge, wash the solid product, vacuum dry, and dry at room temperature for 6-8h to obtain the loaded reagent HMS-PEGDMA.

[0018] The second objective of this invention is to provide the application of the above-mentioned 24-epibrassinolide soluble concentrate in promoting cucumber growth and preventing cucumber powdery mildew.

[0019] The beneficial effects of this invention are: 1. Compared with existing technologies, this invention uses 24-epibrassinolide as the active ingredient to promote cucumber growth. Simultaneously, it introduces essential oils into the soluble concentrate, which, when used synergistically with 24-epibrassinolide, not only better promotes cucumber rooting and growth but also enhances the control effect of the soluble concentrate against cucumber powdery mildew. 24-epibrassinolide, as a plant growth regulator, can promote the growth and development of cucumber plants, improving their immunity and resistance to pathogens. Carvacrol and thymol in oregano essential oil inhibit the growth and reproduction of cucumber powdery mildew pathogens by disrupting the cell structure and physiological functions of fungi. Therefore, the synergistic use of 24-epibrassinolide and oregano essential oil can enhance the antibacterial effect of the prepared soluble concentrate, more effectively inhibiting the growth and reproduction of pathogens, improving the control effect of the soluble concentrate against cucumber powdery mildew, and simultaneously promoting cucumber rooting and growth.

[0020] 2. This invention modifies mesoporous silica nanoparticles with a porous structure and large specific surface area using 3-aminopropyltriethoxysilane and 2-bromoisobutyryl bromide, and then grafts ethylene glycol dimethacrylate onto the mesoporous silica nanoparticles to obtain a loaded agent HMS–PEGDMA with better molecular slow-release effect. Simultaneously, 24-epibrassinolide and oregano essential oil are loaded onto HMS–PEGDMA, allowing both to be maximally loaded onto HMS–PEGDMA and their active ingredients to be stably released, significantly protecting the active ingredients from degradation and prolonging the duration of action. This improves the control effect of the prepared soluble agent against cucumber powdery mildew. In addition, the acrylate groups in the ethylene glycol dimethacrylate of HMS–PEGDMA have unsaturated double bonds, which can undergo addition reactions with the hydroxyl groups on the surface of cucumber leaves to form chemical bonds and generate stable ester compounds. This improves the adhesion to the leaves and avoids the instability of droplets impacting the leaf surface after spraying due to improper spraying methods, which would increase the possibility of droplets slipping and further affect the effective deposition of the pesticide. This enhances the control effect of the prepared soluble agent on cucumber powdery mildew.

[0021] 3. Compared to existing technologies, the soluble agent provided by this invention exhibits excellent UV stability. Under ultraviolet light, when the loaded agent HMS-PEGDMA combines with 24-epibrassinolide and oregano essential oil, HMS-PEGDMA, composed of mesoporous silica nanoparticles and ethylene glycol dimethacrylate, provides a stable matrix, allowing the components in 24-epibrassinolide and oregano essential oil to be more uniformly dispersed within it, reducing volatilization and degradation, thereby improving the stability of the active ingredients. Simultaneously, due to the large specific surface area and pore volume of the mesoporous silica nanoparticles, they can adsorb and fix the photosensitive components in oregano essential oil, thus protecting them from direct UV irradiation and oxidative damage. Furthermore, under ultraviolet light, the π-electron cloud on the double bond of the ethylene glycol dimethacrylate contained in the loaded agent is excited by the energy provided by the ultraviolet light, forming excited-state molecules, thereby initiating polymerization reactions. These reactions may lead to intermolecular cross-linking and polymerization, generating high molecular weight polymers. The generated polymer encapsulates the essential oil molecules, forming a protective layer that prevents the direct action of ultraviolet light on the essential oil molecules and protects the unsaturated bonds in the essential oil from ultraviolet radiation. This avoids the decomposition or cross-linking of the essential oil molecules, maintains the stability and quality of the essential oil, and gives the soluble concentrate prepared by this invention good ultraviolet stability. Detailed Implementation

[0022] The present invention will be further explained below with reference to specific embodiments.

[0023] The parameters of some raw materials in the examples are as follows: Polyvinylpyrrolidone, white powder, purity: 99%, manufactured by Hubei Xinkang Pharmaceutical Chemical Co., Ltd., product number: XK4393.

[0024] The oregano essential oil of this invention is obtained by pressing the leaves or flowers of the oregano plant to extract the essential oil from the plant material, and then collecting it.

[0025] Example 1 A process for preparing a soluble 24-epibrassinolide solution includes the following steps: 0.01g of 24-epibrassinolide, 1g of tocopherol, 2g of sodium carboxymethyl cellulose, 93.99g of water and 3g of propylene glycol were mixed and stirred at 150r / min for 2h until a transparent homogeneous solution was formed, thus obtaining the soluble form of 24-epibrassinolide.

[0026] Example 2 A process for preparing a soluble 24-epibrassinolide solution includes the following steps: Mix 0.01g of 24-epibrassinolide, 0.05g of oregano oil, 1g of tocopherol, 2g of sodium carboxymethyl cellulose, 93.94g of water and 3g of propylene glycol at a stirring speed of 150r / min for 2h until a transparent homogeneous solution is formed, thus obtaining a soluble 24-epibrassinolide solution.

[0027] Example 3 A preparation process for a 24-epibrassinolide soluble concentrate differs from Example 2 in that oregano essential oil is replaced with lemon essential oil.

[0028] Example 4 A preparation process for a 24-epibrassinolide soluble concentrate differs from Example 2 in that oregano essential oil is replaced with thyme essential oil.

[0029] Example 5 A process for preparing a soluble 24-epibrassinolide solution includes the following steps: 0.01g of 24-epibrassinolide, 0.05g of oregano oil, 1g of tocopherol, 2g of sodium carboxymethyl cellulose, 88.94g of water, 5g of loading agent and 3g of propylene glycol were mixed and stirred at 150r / min for 2h until a transparent homogeneous solution was formed, thus obtaining the soluble 24-epibrassinolide.

[0030] The loaded agent is an HMS-PEGDMA composite material, and its preparation steps are as follows: S1. Add 0.244g of polyvinylpyrrolidone to 158g of water, add 16g of styrene under a nitrogen atmosphere, stir and mix to obtain an emulsion; heat the emulsion in an oil bath to 70℃, add 2g of an aqueous solution of 2,2'-azobis(2-methylpropanediamine) dihydrochloride (0.12 g / mL), mix and stir, stir at 70℃ under a nitrogen atmosphere for 24h to obtain polystyrene latex; S2. Mix 4.8g water, 0.4g hexadecyltrimethylammonium bromide, 5.5g anhydrous ethanol and 1g ammonium hydroxide solution (0.013mol / mL), add 25g of polystyrene latex obtained in step S1 above, mix evenly to obtain mixture A; treat mixture A with ultrasonic power of 500W and ultrasonic frequency of 30kHz for 2h, stir for 30min, then add 1.5g tetraethyl orthosilicate dropwise at a dropping rate of 1 drop / s to obtain mixture B; place mixture B at room temperature for 48h, centrifuge, wash the solid product, heat the product to 600℃ at a heating rate of 3℃ / min, and calcine for 8h to obtain hollow mesoporous silica nanoparticles, abbreviated as HMS; S3. Mix 1g of HMS obtained in step S2 above, 200g of toluene and 5g of 3-aminopropyltriethoxysilane, stir at 110°C for 24h under nitrogen atmosphere, after the reaction is completed and cooled to room temperature, centrifuge, wash the solid product with ethanol, vacuum dry, and dry at 50°C for 6h to obtain HMS-NH2. S4. Add 0.1g of HMS-NH2 obtained in step S3 above to 20g of dichloromethane, and sonicate for 1h at an ultrasonic power of 500W and an ultrasonic frequency of 25kHz to obtain a suspension. Add 0.3g of trimethylamine to the suspension, cool to 0℃, and add 10g of a dichloromethane solution of 2-bromoisobutyryl bromide (58.7 mg / mL) at a dropping rate of 2 drops / s. After the addition is complete, stir in an ice bath for 2h, then transfer to room temperature and continue stirring for 24h. Collect the precipitate by centrifugation, vacuum dry, and dry at 50℃ for 6h to obtain HMS-NH-Br. S5. Mix 0.1g of HMS-NH-Br obtained in step S4 above, 1.69g of ethylene glycol dimethacrylate and 2g of cyclohexanone, and add a mixture of 0.1148g of copper bromide, 0.2773g of N,N,N',N",N"-pentamethyldiethylenetriamine and 1g of cyclohexanone under a nitrogen atmosphere. Then stir at 90°C for 6h, centrifuge, wash the solid product with tetrahydrofuran, vacuum dry, and dry at room temperature for 6h to obtain the loaded reagent HMS–PEGDMA.

[0031] Test Example 1 Field efficacy experiment Vigorous and uniformly growing cucumber seedlings were selected and divided into groups 1-5 (Examples 1-5) and a control group. Seedlings from each group were transplanted into seedbeds of the same size and with uniform soil fertility (8m long, 1m wide, 45cm deep, with a soil depth of approximately 40cm). Two rows were planted in each seedbed, with a row spacing of 30cm and a plant spacing of 50cm. Each treatment contained 12 seedlings, with 3 replicates. The pesticide was sprayed every 10 days at the seedling stage, early flowering stage, and young fruit stage, for a total of 3 applications. Groups 1-5 were treated with a 3000-fold dilution of the soluble concentrate prepared in Examples 1-5, while the control group was treated with plain water.

[0032] Determination of the effects of 24-epibrassinolide soluble concentrate on cucumber rooting and growth: Root growth index measurement: Ten days after the last application of pesticide, cucumber roots were photographed. Photos were taken from three different locations around the cucumber roots, with a flat, transparent thin plastic tube (approximately 10cm in diameter and 40cm long) buried in each location. The photographing instrument was placed inside the plastic tube, starting from the soil surface and gradually deepening to capture images of the roots. The instrument was automatically set to extend 1cm at a time. The obtained root photos were organized according to location and depth, and the total root length was quantitatively analyzed using root analysis software.

[0033] Aboveground morphological indicators were measured: 10 days after the last application of the pesticide, the plant height and stem diameter of the cucumber were measured. Plant height was the natural height from the base of the plant to the main stem growth point; stem diameter was the horizontal stem diameter at 3 cm above the surface of the potting soil.

[0034] The test results are averaged. See Table 1 for specific test data.

[0035] Table 1. Effects on rooting and growth of cucumber crop

[0036] As shown in Table 1, compared with the control group, Examples 1-5 significantly promoted the rooting and growth of cucumber, indicating that 24-epibrassinolide can promote cell division and elongation, thereby increasing the plant's growth rate and promoting cucumber growth. Among these, Examples 2-5 showed a better promoting effect on cucumber growth than Example 1, indicating that the synergistic use of 24-epibrassinolide and essential oils has a better promoting effect on cucumber rooting and growth.

[0037] Test Example 2 Control effect of cucumber powdery mildew Preparation of conidium suspension: Cucumber powdery mildew occurs naturally on local farms. The fungicide group of the plant protection department propagated the fungicides on potted cucumbers and preserved them. Spore powder was brushed off from diseased leaves and transferred to disease-free cucumber seedlings. After re-spore production, fresh spores were washed off with distilled water, filtered through double-layered gauze, and prepared to a spore concentration of 1×10⁻⁶. 5 A suspension of spores per mL, the spore suspension should be prepared and used immediately.

[0038] For the seedling pot experiment, treatments were set up in Examples 1-5 according to the treatment results, and a blank control group without pesticide application was also set up. Each treatment was repeated 3 times. Cucumber potted seedlings with two true leaves were selected, the growing point was cut off, and the pesticide was manually sprayed evenly on both sides of the leaves using a throat sprayer until the leaf surface was evenly moistened. After the pesticide was allowed to air dry naturally, it was ready for use. 24 hours later, the seedlings were inoculated with cucumber powdery mildew spore suspension and promptly moved into a greenhouse / plant growth room, maintaining a temperature of 20-25℃, a relative humidity of 70%-80%, and alternating light / dark for 12 hours.

[0039] Fourteen days after application of the pesticide, the disease incidence of each treatment was investigated by grade. All leaves of all plants in each treatment were investigated, and the grading was based on the following standards (by leaf).

[0040] Level 0: No disease; Grade 1: The area of ​​lesions accounts for less than 5% of the total leaf area; Grade 3: The lesion area accounts for 6% to 10% of the total leaf area; Level 5: The lesion area accounts for 11% to 25% of the total leaf area; Level 7: The lesion area accounts for 26% to 50% of the total leaf area; Level 9: The lesion area accounts for more than 50% of the total leaf area.

[0041] The method for calculating the disease index is as follows: Disease index = Σ(number of diseased leaves at each level × corresponding level) × 100 / total number of leaves surveyed × 9 The method for calculating the prevention and control effect is as follows: Prevention and control efficacy (%) = (CK - PT) × 100 / CK In the formula: CK: disease index after drug administration in the blank control area, PT: disease index after drug administration in the drug-treated area.

[0042] The test results are shown in Table 2.

[0043] Table 2. Control efficacy of cucumber powdery mildew in each group

[0044] Table 2 shows that, compared with the blank control group, Examples 1-5 all had a certain control effect on cucumber powdery mildew. Examples 2 and 5 showed significantly better control effects than the other groups. This is because carvacrol and thymol in oregano essential oil inhibit the growth and reproduction of cucumber powdery mildew pathogens by disrupting the cell structure and physiological functions of the fungus. 24-Epibrassinolide, as a plant growth regulator, can promote the growth and development of cucumber plants, improve their immunity and resistance to pathogens. Therefore, the synergistic use of 24-epibrassinolide and oregano essential oil can enhance the antibacterial effect of the prepared soluble concentrate, more effectively inhibiting the growth and reproduction of pathogens and improving the control effect of the soluble concentrate on cucumber powdery mildew.

[0045] Compared with Examples 2-5, Example 5 showed significantly better control effect than Examples 2-4. This is because after the loaded agent HMS-PEGDMA was combined with 24-epibrassinolide and oregano essential oil, the mesoporous silica nanoparticles, with their porous structure and large specific surface area, and functional group modification with 3-aminopropyltriethoxysilane and 2-bromoisobutyryl bromide, achieved better sustained release of the blocked molecules. Therefore, 24-epibrassinolide and oregano essential oil could not only be loaded onto HMS-PEGDMA to the maximum extent, but their active ingredients could also be released stably, significantly protecting their active ingredients from degradation and prolonging the duration of action. This improved the control effect of the prepared soluble agent on cucumber powdery mildew. In addition, the acrylate groups in the ethylene glycol dimethacrylate of HMS–PEGDMA have unsaturated double bonds, which can undergo addition reactions with the hydroxyl groups on the surface of cucumber leaves to form chemical bonds and generate stable ester compounds. This improves the adhesion to the leaves and avoids the instability of droplets impacting the leaf surface after spraying due to improper spraying methods, which would increase the possibility of droplets slipping and further affect the effective deposition of the pesticide. This enhances the control effect of the prepared soluble agent on cucumber powdery mildew.

[0046] Test Example 3 UV stability test Five mL each of the soluble concentrates prepared in Examples 2 and 5 and oregano essential oil were used as the Example 2 group, Example 5 group, and control group, respectively. Since oregano essential oil is hydrolyzed stably in pH 7 phosphate buffer, the three groups of samples were exposed to a 36W germicidal lamp (254 nm) at a distance of 20 cm for 24 h in pH 7 phosphate buffer to test the stability of each group against ultraviolet radiation. The changes in essential oil content in each group were analyzed by high-performance liquid chromatography (HPLC) with 270 nm ultraviolet detection (Agilent HP1260, USA). The chromatographic conditions were as follows: a reversed-phase Welch Ultimate XB-C18 column (250 × 4.6 mm inner diameter, 5 μm) was used, and the mobile phase was methanol and water (80:20, v / v). Analysis was performed using an injection volume of 20 μL and a flow rate of 1.0 mL / min. All solvents were filtered through a 0.45 μm membrane filter before use.

[0047] The test results are shown in Table 3.

[0048] Table 3 Degradation rate of essential oils in each group

[0049] As shown in Table 2, compared with the control group, the degradation rate of essential oils in Examples 2 and 5 was reduced, with Example 5 showing a significant decrease. This is because the unsaturated bonds in essential oils are prone to addition reactions under ultraviolet light, forming cross-linked structures. Simultaneously, homolytic or heterolytic cleavage may occur, leading to molecular breakage into smaller fragments, ultimately causing the decomposition of the essential oil molecules and affecting their stability and efficacy. When the loaded agent HMS-PEGDMA is combined with 24-epibrassinolide and oregano essential oil, the HMS-PEGDMA, composed of mesoporous silica nanoparticles and ethylene glycol dimethacrylate, provides a stable matrix, allowing the components of 24-epibrassinolide and oregano essential oil to be more uniformly dispersed within it, reducing volatilization and degradation, thereby improving the stability of the active ingredients. Simultaneously, the mesoporous silica nanoparticles have a large specific surface area and pore volume, which can adsorb and fix the photosensitive components in oregano essential oil, thus protecting them from direct ultraviolet radiation and oxidative damage. Furthermore, under ultraviolet light, the π electron clouds on the double bonds of ethylene glycol dimethacrylate contained in the loaded agent are excited by the energy provided by the ultraviolet light, forming excited-state molecules, thereby initiating a polymerization reaction. These reactions may lead to intermolecular cross-linking and polymerization, generating high molecular weight polymers. The generated polymers encapsulate the essential oil molecules, forming a protective layer that prevents the direct action of ultraviolet light on the essential oil molecules, protects the unsaturated bonds in the essential oil from ultraviolet radiation, thereby preventing the decomposition or cross-linking of the essential oil molecules and maintaining the stability and quality of the essential oil. In summary, the soluble concentrate prepared by this invention has excellent ultraviolet stability.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for the preparation of a 24-epibrassinolide soluble solution, characterized in that, The preparation steps include the following: By weight, 0.001-1 parts of 24-epibrassinolide, 0.05-1 parts of plant essential oil, 1-2 parts of antioxidant, 1-3 parts of surfactant, 50-100 parts of water, 5-10 parts of loading agent and 2-5 parts of antifreeze are mixed and stirred at a stirring speed of 150-300 r / min for 1.5-2 h until a transparent homogeneous solution is formed, thus obtaining 24-epibrassinolide soluble agent; The loaded agent is an HMS-PEGDMA composite material; The preparation steps of the loaded drug are as follows: S1. Polyvinylpyrrolidone is added to water, and styrene is added under a nitrogen atmosphere. The mixture is stirred to obtain an emulsion. The emulsion is heated to 60-80°C in an oil bath, and an aqueous solution of 2,2'-azobis(2-methylpropanediamine) dihydrochloride is added. The mixture is stirred to obtain a mixture. The mixture is stirred at 60-80°C under a nitrogen atmosphere for 22-24 hours to obtain polystyrene latex. S2. Mix water, hexadecyltrimethylammonium bromide, ethanol, and ammonium hydroxide solution, add the polystyrene latex obtained in step S1 above, and mix evenly to obtain mixture A; ultrasonically treat mixture A at an ultrasonic power of 450-600W and an ultrasonic frequency of 25-30kHz for 2-3 hours, then stir for 30-40 minutes, and then add tetraethyl orthosilicate dropwise to obtain mixture B; place mixture B at room temperature for 45-50 hours, centrifuge, wash the solid product, and calcine the product at 600-650℃ for 8-10 hours to obtain hollow mesoporous silica nanoparticles, abbreviated as HMS; S3. Mix the HMS obtained in step S2 above, toluene and 3-aminopropyltriethoxysilane, and stir at 100-120℃ for 24-25h under nitrogen atmosphere. After the reaction is completed, cool to room temperature, centrifuge, wash the solid product, vacuum dry, and dry at 50-60℃ for 6-8h to obtain HMS-NH2. S4. Add the HMS-NH2 obtained in step S3 above to dichloromethane and ultrasonically disperse it for 1-2 hours at an ultrasonic power of 450-600W and an ultrasonic frequency of 25-30kHz to obtain a suspension. Add trimethylamine to the suspension, cool to 0-5℃, and then add a dichloromethane solution of 2-bromoisobutyryl bromide dropwise. After the addition is complete, mix and stir to obtain a mixture. Stir the mixture in an ice bath for 2-3 hours, then transfer it to room temperature and continue stirring for 24-25 hours. Collect the precipitate by centrifugation, vacuum dry it, and dry it at 50-60℃ for 6-8 hours to obtain HMS-NH-Br. S5. Mix HMS-NH-Br, ethylene glycol dimethacrylate and cyclohexanone obtained in step S4 above; add a mixture of copper bromide, N,N,N',N",N"-pentamethyldiethylenetriamine and cyclohexanone under a nitrogen atmosphere, and then stir at 90-100℃ for 6-8h; centrifuge, wash the solid product, vacuum dry, and dry at room temperature for 6-8h to obtain the loaded reagent HMS-PEGDMA.

2. A process for the preparation of a 24-epibrassinolide soluble solution as claimed in claim 1, wherein: The antifreeze is at least one of glycerol, propylene glycol, ethylene glycol, and glycerin.

3. The preparation process of a 24-epibrassinolide soluble concentrate as described in claim 1, characterized in that: The surfactant is at least one of calcium dodecylbenzenesulfonate, sodium carboxymethyl cellulose, sulfonyl chloride, calcium lignin sulfonate, nonylphenol polyoxyethylene aldehyde, and styrylphenol polyoxyethylene ether.

4. The preparation process of a 24-epibrassinolide soluble concentrate as described in claim 1, characterized in that: The antioxidant is tocopherol.

5. The preparation process of a 24-epibrassinolide soluble concentrate as described in claim 1 or 2, characterized in that: The plant essential oil is at least one of oregano essential oil, lemon essential oil, and thyme essential oil.

6. The preparation process of a 24-epibrassinolide soluble concentrate as described in claim 1 or 2, characterized in that: The plant essential oil mentioned is oregano essential oil.

7. A soluble concentrate of 24-epibrassinolide, characterized in that: Prepared by the method described in any one of claims 1-6.

8. The application of the 24-epibrassinolide soluble concentrate as described in claim 7 in promoting cucumber growth and controlling cucumber powdery mildew.

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