A method for nano-sizing emamectin

Abstract

The application discloses a method for nanometerizing emamectin benzoate. The method comprises the following steps: mixing an organic acid or an organic acid salt buffer solution with a solution of emamectin benzoate to obtain nanometerized emamectin benzoate; wherein the molar ratio of emamectin benzoate to the organic acid is 1:(10-30); and the molar ratio of emamectin benzoate to the acid radical ion in the organic acid salt buffer solution is 1:(10-30). By adding 10-30 times of the molar ratio of the organic acid or the organic acid salt buffer solution to the solution of emamectin benzoate, the emamectin benzoate can be nanometerized to form a micellar solution, the solubility and effective content of the emamectin benzoate in water are greatly improved, and no organic solvent needs to be added in the later period. The nanometerized emamectin benzoate prepared by the method has small particle size, which can reach 6-8 nm, and uniform particle size.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of plant pest control, and more particularly relates to a method for nanoizing emamectin benzoate. BACKGROUND

[0002] Emamectin benzoate (EB) is an organic compound with a molecular formula of C 56 H 81 NO 15 , a molecular weight of 1008.240, and a white or light yellow crystalline powder. It is a semi-synthetic derivative of the green, safe, and highly effective avermectin microbial source pesticide. In the mid-1990s, Merk & Co. obtained a stable and highly effective commercial pesticide by derivatizing the main active components B1a and B1b of avermectin with benzoic acid. Emamectin benzoate is also known as emamectin or invermectin. It is a semi-synthetic antibiotic pesticide that has a wide range of applications in livestock, medical treatment, and plant pest control.

[0003] Emamectin benzoate is slightly soluble in water and easily soluble in polar organic solvents such as DMSO, methanol, and ethanol, but insoluble in non-polar organic solvents such as hexane and dichloroethane. Emamectin benzoate is a more broad-spectrum insecticide than avermectin, which can effectively control pests in the orders Lepidoptera, Homoptera, and Coleoptera, with a killing activity 2-3 orders of magnitude higher than that of avermectin. It also has the advantages of ultra-high efficiency, low toxicity, no pollution, and little impact on the environment.

[0004] At room temperature, emamectin benzoate is easily adsorbed on soil and easily degraded under ultraviolet irradiation, and has low solubility in water. Emamectin benzoate pesticide is usually used in the form of emulsifiable concentrate in soil. Although emulsifiable concentrate formulations have good stability and good control effect, large-scale use can cause serious environmental pollution and drug damage to crops.

[0005] The conventional method for nanoizing emamectin benzoate requires the intervention of a nano-carrier for the synthesis and preparation of nano-emamectin benzoate. However, this conventional method makes the preparation of nano-emamectin benzoate more complex, and the obtained nano-particles usually have a particle size of more than 100 nm. In the preparation, characterization, and biological activity of emamectin benzoate nano-preparation, a nano-capsule of emamectin benzoate with an average particle size of 6.35 nm is prepared. By screening surfactants and modifying NPSO, the dispersion of emamectin benzoate is achieved. However, the overall preparation method is complex, the process is long, and it is not simple and fast to prepare nano-emamectin benzoate with a small particle size. Therefore, how to provide a simple, fast, and small particle size nano-emamectin benzoate method has become a technical problem to be solved. SUMMARY

[0006] In view of the above existing technical problems, a primary object of the present application is to provide a method for nanoizing emamectin benzoate, which can prepare emamectin benzoate with a particle size of 6-8 nm by a very simple and fast method.

[0007] A second object of the present application is to provide nanoized emamectin benzoate prepared by the method for nanoizing emamectin benzoate.

[0008] A third object of the present application is to provide the use of the above nanoized emamectin benzoate in the preparation of pesticide formulations or the control of plant pests.

[0009] A fourth object of the present application is to provide a pesticide formulation comprising the above nanoized emamectin benzoate.

[0010] In order to achieve the above objects, the present application is implemented by the following technical solutions:

[0011] A method for nanoizing emamectin benzoate, which comprises mixing an organic acid or an organic acid salt buffer solution with a solution of emamectin benzoate to prepare nanoized emamectin benzoate; wherein the molar ratio of emamectin benzoate to organic acid is 1:(10-30); and the molar ratio of emamectin benzoate to acid anion in the organic acid salt buffer solution is 1:(10-30).

[0012] The inventors have found that the addition of 10-30 times the molar ratio of organic acid or organic acid salt buffer solution to the emamectin benzoate solution can nanoize emamectin benzoate and form a micellar solution, greatly improving the solubility and effective content of emamectin benzoate in water, and without the need for adding any organic solvent later. The present application verifies the nanoization of emamectin benzoate by means of laser particle size analysis, Fourier transform infrared spectroscopy, cryogenic scanning electron microscopy, nuclear magnetic resonance technology, etc., and finds that the structure of nanoized emamectin benzoate has not changed. The present application provides a simple and fast method for nanoizing emamectin benzoate, which can prepare nanoized emamectin benzoate with a small particle size, which can reach 6-8 nm, and uniform particle size.

[0013] Specifically, the molar ratio of emamectin benzoate to organic acid in the present application can be 1:12, 1:14, 1:15, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28, or 1:30; the present application is not limited thereto.

[0014] Specifically, the molar ratio of emamectin benzoate to acid anion in the organic acid salt buffer solution in the present application can be 1:12, 1:14, 1:15, 1:16, 1:18, 1:20, 1:22, 1:24, 1:26, 1:28, or 1:30; the present application is not limited thereto.

[0015] In one of the embodiments, the molar ratio of emamectin benzoate to organic acid is 1:(15-30); the molar ratio of emamectin benzoate to the anion of the organic acid salt in the organic acid or organic acid salt buffer solution is 1:(15-30). At this preferred ratio, emamectin benzoate can be completely dissolved in the organic acid or organic acid salt buffer solution at a relatively fast speed, and complete nanocrystallization is achieved.

[0016] In one of the embodiments, the organic acid salt buffer solution is a buffer solution composed of an organic acid and its corresponding organic acid salt, and the molar ratio of the organic acid to its corresponding organic acid salt is (3-1):1. At this preferred ratio, emamectin benzoate can be completely dissolved in the organic acid or organic acid salt buffer solution.

[0017] In one of the embodiments, the organic acid or organic acid salt buffer solution is a carboxylic acid or carboxylic acid salt buffer solution containing 1-8 carbon atoms.

[0018] In one of the embodiments, the carboxylic acid is selected from one or more of formic acid, acetic acid, butyric acid, citric acid, malic acid, and isovaleric acid.

[0019] In one of the embodiments, the carboxylic acid salt buffer solution is selected from one or more of formate buffer solution, acetate buffer solution, butyrate buffer solution, and isovalerate buffer solution.

[0020] In one of the embodiments, the carboxylic acid salt buffer solution is specifically a sodium carboxylate buffer solution, and the sodium carboxylate buffer solution is selected from one or more of sodium formate buffer solution, sodium acetate buffer solution, sodium butyrate buffer solution, and sodium isovalerate buffer solution.

[0021] In one of the embodiments, the emamectin benzoate solution is an aqueous emamectin benzoate solution. In the aqueous emamectin benzoate solution, the concentration of emamectin benzoate is 5-15 mM.

[0022] Further, the present application also claims a nanocrystallized emamectin benzoate prepared by the method for nanocrystallizing emamectin benzoate.

[0023] In one of the embodiments, the particle size of the nanocrystallized emamectin benzoate is 6-8 nm.

[0024] Further, the present application also claims the use of the above-mentioned nanocrystallized emamectin benzoate in the preparation of a pesticide preparation or in the field of plant pest control.

[0025] Further, the present application also claims a pesticide preparation containing the above-mentioned nanocrystallized emamectin benzoate as an effective ingredient.

[0026] Compared with the prior art, the present application has the following beneficial effects: the present application provides a simple and rapid method for nanoizing emamectin benzoate, by adding 10-30 times molar ratio of organic acid or organic acid salt buffer solution to emamectin benzoate or its solution, the emamectin benzoate can be nanoized and micellar solution is formed, which greatly improves the solubility and effective content of emamectin benzoate in water, and no additional organic solvent is required in the later stage. The nanoized emamectin benzoate prepared by the method of the present application has not only small particle size, which can reach 6-8 nm, but also uniform particle size. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The solubility change results of the blank control and the nanoized emamectin benzoate solutions prepared in Example 1 and Comparative Example 2.

[0028] Figure 2 The red laser parallel beam change results of the blank control and the nanoized emamectin benzoate solutions prepared in Example 1 and Comparative Example 2.

[0029] Figure 3 The solubility change results of the solutions in Example 1, 3 and 4 and Comparative Example 1.

[0030] Figure 4 The solubility results of the nanoized emamectin benzoate solutions prepared in Example 5-10 when the molar ratio of sodium acetate and acetic acid is different.

[0031] Figure 5 The laser particle size analysis particle size results of the nanoized emamectin benzoate in Example 1.

[0032] Figure 6 The infrared spectrum experimental results of the nanoized emamectin benzoate in Example 1.

[0033] Figure 7 The freeze scanning electron microscope results of the nanoized emamectin benzoate in Example 1; wherein Figure 7 (a) is the freeze scanning electron microscope results of the nanoized emamectin benzoate without scale; Figure 7 (b) is the freeze scanning electron microscope results of the nanoized emamectin benzoate from another angle with scale.

[0034] Figure 8 The nuclear magnetic resonance analysis results of the nanoized emamectin benzoate in Example 1. DETAILED DESCRIPTION

[0035] The present application will be further described below in combination with the drawings and specific examples, but the examples do not limit the present application in any form. Unless otherwise specified, the reagents, methods and devices used in the present application are conventional reagents, methods and devices in the technical field.

[0036] Example 1 A method for nanoization of emamectin benzoate

[0037] (1) Take emamectin benzoate technical (95%) 0.9348 g, add 100 mL distilled water, mix well to prepare a 10 mM emamectin benzoate suspension;

[0038] (2) Take 5 mL of the 10 mM emamectin benzoate suspension into a centrifuge tube, add acetic acid 0.0605 g, the molar ratio of emamectin benzoate to acetic acid is 1:20, shake and mix well for about 5 minutes to obtain a solution containing nanoized emamectin benzoate.

[0039] Example 2 A method for nanoization of emamectin benzoate

[0040] The difference between this embodiment and Example 1 is that sodium acetate solution (acetic acid 0.0605 g, sodium hydroxide 0.04 g) is added.

[0041] Example 3 A method for nanoization of emamectin benzoate

[0042] The difference between this embodiment and Example 1 is that the molar ratio of emamectin benzoate to acetic acid is 1:15.

[0043] Example 4 A method for nanoization of emamectin benzoate

[0044] The difference between this embodiment and Example 1 is that the molar ratio of emamectin benzoate to acetic acid is 1:10.

[0045] Example 5 A method for nanoization of emamectin benzoate

[0046] (1) Take the 10 mM emamectin benzoate suspension prepared in Example 1;

[0047] (2) Take 5 mL of the 10 mM emamectin benzoate suspension into a centrifuge tube, add a buffer solution of sodium acetate and acetic acid, the molar ratio of emamectin benzoate to acetate ion is 1:20 (wherein sodium acetate 0.0779 g, acetic acid 0.0030 g, the molar ratio of sodium acetate to acetic acid is 19:1), shake and mix well for about 5 minutes to obtain a solution containing nanoized emamectin benzoate.

[0048] Example 6 A method for nanoization of emamectin benzoate

[0049] The difference between this embodiment and Example 5 is that the molar ratio of sodium acetate to acetic acid is 18:2.

[0050] Example 7 A method for nanoization of emamectin benzoate

[0051] The difference between this embodiment and Example 5 is that the molar ratio of sodium acetate to acetic acid is 17:3.

[0052] Example 8 A method for nanoization of emamectin benzoate

[0053] The difference between this example and Example 5 is that the molar ratio of sodium acetate to acetic acid is 15:5.

[0054] Example 9 A method for nano-sizing emamectin

[0055] The difference between this example and Example 5 is that the molar ratio of sodium acetate to acetic acid is 10:10.

[0056] Example 10 A method for nano-sizing emamectin

[0057] The difference between this example and Example 5 is that the molar ratio of sodium acetate to acetic acid is 9:11.

[0058] Example 11 A method for nano-sizing emamectin

[0059] The difference between this example and Example 1 is that the molar ratio of emamectin to acetic acid is 1:30.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that the molar ratio of emamectin to acetic acid is 1:5.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 1 is that 5 mL of a 10 mM emamectin suspension was taken into a centrifuge tube, and 20 times molar ratio of NaCl (0.058 g) was added, and mixed well by shaking for about 5 minutes.

[0064] Test Example 1 Emamectin solubility change test

[0065] Figure 1 The results of the solubility change of the blank control (the emamectin suspension in Example 1), and the nano-sized emamectin solutions prepared in Example 1, Comparative Example 2.

[0066] The results are shown in Table 1. Figure 1 As shown in Table 1, the emamectin is slightly soluble in water in the blank control, and a lot of precipitate can be seen; the emamectin + NaCl solution in Comparative Example 2 is not dissolved, and a lot of precipitate particles can be seen. After the addition of acetic acid to the emamectin in Example 1, the solubility is greatly improved, and the emamectin in the solution is completely dissolved.

[0067] The addition of sodium acetate solution in Example 2 has the same effect as Example 1, and the emamectin in the solution is completely dissolved. It can be seen that it is the effect of the acetate ion, not the simple acidity (PH), that promotes the dissolution of emamectin.

[0068] Figure 2 The results of the red laser parallel light beam change of the blank control, and the nano-sized emamectin solutions prepared in Example 1, Comparative Example 2.

[0069] As Figure 2 shown, when irradiated with a beam of parallel red laser light, a bright "pathway" appeared in Example 1, which is the phenomenon of Tyndall effect, indicating that the solution is a colloidal solution with dispersed particles of 1-100 nm in diameter; while no bright "pathway" appeared in the solutions of Comparative Example 2 and the blank control, indicating that the solutions have dispersed particles of more than 100 nm in diameter.

[0070] Figure 3 The solubility change results of the nano-emulsified emamectin benzoate solutions prepared in Examples 1, 3, 4, and the solution in Comparative Example 1 are shown in Table 1. Figure 3 As shown in Table 1, when the molar ratio of emamectin benzoate to acetic acid is 1:5, more precipitates can be seen, and the nano-emulsification effect of emamectin benzoate is poor; when the molar ratio of emamectin benzoate to acetic acid is 1:10, the precipitates can slowly disappear; when the molar ratio of emamectin benzoate to acetic acid is 1:15 and 1:20, the precipitates disappear.

[0071] Figure 4 The solubility results of the nano-emulsified emamectin benzoate solutions prepared in Examples 5-10 with different molar ratios of sodium acetate to acetic acid are shown in Table 2. Figure 4 As shown in Table 2, when the molar ratio of sodium acetate to acetic acid is 19:1, more precipitates appear; when the molar ratio of sodium acetate to acetic acid is 18:2, more precipitates still appear; when the molar ratio of sodium acetate to acetic acid is 17:3, the precipitates decrease but still exist; when the molar ratio of sodium acetate to acetic acid is 15:5, a small amount of precipitates exist; when the molar ratio of sodium acetate to acetic acid is 10:10, the precipitates slowly disappear; when the molar ratio of sodium acetate to acetic acid is 9:11, the precipitates disappear.

[0072] Test Example 2: Laser particle size analysis test

[0073] The nano-emulsified emamectin benzoate solutions prepared according to the ratios obtained in the above examples are prepared for standby use.

[0074] (1) Zeta potential: The samples to be tested are the solutions prepared in Examples 1, 2-11 and Comparative Example 2, and the blank control (the emamectin benzoate suspension in Example 1). The cuvette of the test sample is cleaned thoroughly, at least 3 times, and the cuvette is wiped clean with a lens paper. 1 mL of the sample is taken in the cuvette, the liquid on both sides is kept balanced, and the sample liquid is above the electrode of the cuvette. The cuvette is placed in the laser particle size analyzer, and the parameters are adjusted for Zeta potential test of the sample. The electrode should not be touched by hand during the operation to avoid contamination.

[0075] (2) Size particle size: The cuvette of the test sample is cleaned thoroughly, at least 3 times, and the cuvette is wiped clean with a lens paper. 1 mL of the sample is taken in the cuvette, and the particle size parameters are adjusted for Size particle size test of the sample.

[0076] Figure 5 is the result of laser particle size analysis of the nano-emulsified emamectin benzoate in Example 1. The result of the size particle is shown in Figure 5 The particle size of the nano-emulsified emamectin benzoate in Example 1 measured by the laser particle size analyzer is 6-8 nm, as shown in

[0077] The result of the Zeta potential is shown in Table 1. The Zeta potentials of the blank control, Comparative Example 2 and Example 1 are 53.867±0.2168 mV, 35.567±0.0425 mV and 23.160±0.4530 mV, respectively. The Zeta potentials of the emamectin benzoate after different treatments are positive and gradually decrease in absolute value. The value of the Zeta potential is related to the stability of the colloidal dispersion. The PDI of the emamectin benzoate itself is 0.7885, indicating that the solubility of the emamectin benzoate in water is very low and the stability in water is very poor. The PDI of the solution in Comparative Example 2 is 0.6445, indicating that the addition of NaCl can appropriately improve the dispersibility and stability of the emamectin benzoate in water. The PDI of the solution in Example 1 is 0.493, indicating that the emamectin benzoate after nano-emulsification has good dispersibility and stability in water.

[0078] Table 1

[0079] Name PDI Zeta / mV Blank control 0.7885±0.047 53.867±0.2168 Comparative Example 2 0.6445±0.850 35.567±0.0425 Example 1 0.493±0.0199 23.160±0.4530

[0080] Test Example 3 Infrared Spectroscopy Test of Emamectin Benzoate Acetate

[0081] The solution of the nano-emulsified emamectin benzoate in Example 1 and the blank control (10 mM emamectin benzoate suspension in Example 1) are freeze-dried. The tabletting die, medicine spoon, tweezers and the like to be used are cleaned with cotton soaked with anhydrous ethanol and dried. KBr and the ground and dried sample powder are uniformly laid on the base of the die, the upper pressure head is pressed and rotated by hand, and the sample powder is uniformly and evenly laid. The die is placed in the center of the tabletting machine workbench, the pressure indication value is about 20 MPa, and the pressure is maintained for 5 min. The die is removed, the upper pressure head and the die jacket are removed, the upper pressure head is placed on a flat plate, and the sample is collected in the sample chamber. Before sample collection, a blank KBr sheet is prepared for background collection.

[0082] Figure 6 is the result of the infrared spectroscopy test of the nano-emulsified emamectin benzoate in Example 1. The result is shown in Figure 6 The absorption of emamectin benzoate at 3492 cm -1 in the blank control is the vibration peak of hydrogen bonding, and the peak in the nano-emulsified emamectin benzoate in Example 1 is shifted to 3461 cm -1Meanwhile, the absorption peak of nano-sized abamectin at this point is stronger than that of abamectin, indicating that the hydrogen bonds have changed. Acetic acid has disrupted the hydrogen bonds of abamectin, which weakens the aggregation of abamectin molecules. Therefore, nano-sized abamectin has strong dispersibility.

[0083] Test Example 4: Cryo-Scanning Electron Microscopy Experiment

[0084] The solution of nano-sized abamectin from Example 1 was filtered and spotted, and then frozen in liquid nitrogen for about 40 seconds. It was then sublimated at -80°C for 5 minutes, and the images were observed after three sublimations.

[0085] Figure 7 These are the cryo-scanning electron microscopy results of nano-sized emamectin benzoate in Example 1; wherein Figure 7 (a) Cryo-scanning electron microscopy results of nano-sized abamectin without scale; Figure 7 (b) Another angle, showing the cryo-scanning electron microscopy results of nano-sized emamectin benzoate with a scale. Results are as follows: Figure 7 (a) and Figure 7 As shown in (b), the nano-sized abamectin appears spherical with an average nanoparticle size between 10-20 nm. Due to the approximately 40-second gold sputtering step during the cryo-electron microscopy operation, the particle size measured by the electron microscope will increase slightly. Therefore, it is basically consistent with the particle size of about 6 nm measured by laser particle size analysis. This indicates that adding an appropriate amount of organic acid can change both the solubility of abamectin and the size of the nanoparticles in the abamectin solution.

[0086] Test Example 5: Nuclear Magnetic Resonance Analysis Experiment

[0087] The solution containing nano-sized emamectin benzoate from Example 1 was lyophilized to obtain lyophilized emamectin benzoate nano-solution powder. 15 mg of emamectin benzoate technical material and lyophilized emamectin benzoate nano-solution powder were accurately weighed into NMR tubes, and 500 μL of deuterated DMSO was added to dissolve them respectively. The results were analyzed using an NMR spectrometer. 1 H-NMR spectrum.

[0088] Figure 8 The results are the nuclear magnetic resonance analysis results of the nano-sized emamectin benzoate from Example 1. The results are as follows... Figure 8 As shown, the peak shapes and positions of abamectin and nano-sized abamectin are almost identical, with the only difference being an additional hydrogen peak in acetic acid (chemical shift around 1.8 ppm) in the lyophilized abamectin sample with added acetic acid. This indicates that the molecular structure has not changed, demonstrating that adding appropriate amounts of organic acid compounds or organic acid salt buffers will not alter the structure of abamectin itself.

[0089] The foregoing examples are illustrative only and are not intended to limit the scope of the methods described herein. The appended claims are intended to claim as broad a scope as possible consistent with the recitations therein, and the examples presented herein are intended to be illustrative only and are not intended to limit the scope of the claims. Some of the examples presented herein are intended to demonstrate the scope of the claims by illustrating the scope of certain features. Thus, the applicant intends that the claims to cover all aspects of the methods described herein that fall within the scope of the claims. Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

Claims

1. A method for nanoization of emamectin, characterized by, The organic acid or organic acid salt buffer solution is mixed with the emamectin benzoate solution to obtain nano-sized emamectin benzoate; The emamectin benzoate solution is an aqueous emamectin benzoate solution; The molar ratio of emamectin benzoate to organic acid is 1:(10-30). The molar ratio of emamectin benzoate to acid radical ions in the organic acid salt buffer solution is 1:(15-30). The organic acid salt buffer solution is a buffer solution composed of an organic acid and its corresponding organic acid salt, and the molar ratio of the organic acid to its corresponding organic acid salt is (3-1):

1. The organic acid is selected from one or more of formic acid, acetic acid, butyric acid, and isovaleric acid. The organic acid salt buffer solution is selected from one or more of formate buffer solution, acetate buffer solution, butyrate buffer solution, and isovalerate buffer solution.

2. The method of claim 1, wherein, The molar ratio of emamectin benzoate to organic acid is 1:(15-30).

3. The method of claim 1, wherein, The concentration of emamectin benzoate in the aqueous emamectin benzoate solution is 5-15 mM.

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