Flavonoid compound, composition and application of flavonoid compound and composition in prevention and treatment of plant pests

Abstract

The invention discloses a flavonoid compound, a composition and application of the flavonoid compound to prevention and treatment of plant pests, the structure of the flavonoid compound is shown in a formula I, and the flavonoid compound can be used for preventing pests with piercing-sucking mouthparts and pests with rasping-sucking mouthparts, especially pests caused by Amyzus pisum and Odontothrips loti to medicago sativa 'Ladak +', and the flavonoid compound can be used for preventing pests caused by Amyzus pisum and Odontothrips loti to medicago sativa 'Ladak +'. The flavonoid compound disclosed by the invention is derived from a plant secondary metabolite, has the advantages of good environmental compatibility, easiness in degradation, relatively strong target specificity and the like, and accords with the development direction of green pesticides. Therefore, the invention not only provides important material basis and application basis for the development of efficient and safe botanical insecticides, but also has positive significance for promoting the production and ecological sustainable development of the grass industry.

Description

Technical Field

[0001] This invention belongs to the field of agricultural pest control technology, and relates to the use of flavonoids in biological pesticides for controlling plant pests, specifically to a flavonoid compound, a composition and its application in controlling plant pests. Background Technology

[0002] In agricultural production, common pests such as aphids and thrips cause serious damage to crop growth and development, often leading to reduced yields and lower quality. Currently, chemical pesticides are still the primary method for controlling these pests, but long-term, large-scale use can lead to a series of prominent problems, including environmental pollution, the development of pesticide resistance in pests, and excessive pesticide residues in agricultural products. Plant-derived active ingredients, due to their natural origin, good environmental compatibility, and low likelihood of inducing resistance, are gradually becoming a focus of green pesticide research and development. However, existing plant-derived substances still have certain limitations in terms of insecticidal activity, spectrum of action, and crop safety. There is a need to discover new plant-derived insecticidal ingredients that combine high efficiency with environmental safety. Given the vast variety of known plant-derived active ingredients, systematically screening compounds with significant insecticidal activity and no adverse effects on plant growth is of significant practical importance for developing environmentally friendly pesticides.

[0003] Flavonoid derivatives are environmentally friendly and safe for humans and animals, and can be used to develop natural, green plant-derived insecticides. They possess characteristics such as low toxicity, low residue, and high selectivity, laying the foundation for the development of novel environmentally compatible pesticides. However, the application of these flavonoid derivatives in controlling agricultural pests such as aphids and thrips has not yet been systematically studied or publicly reported. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a flavonoid compound, composition and its application in the control of plant pests, and to solve the technical problem that flavonoid compounds in the prior art are difficult to have both high insecticidal activity and crop safety.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: Application of flavonoids in the control of plant pests; the flavonoids are shown in Formula I: Formula I.

[0006] In the formula: R1, R2 and R3 are independently selected from hydrogen, hydroxyl, C1-C6 alkoxy, glycosidic group; R4 is selected from hydrogen, methyl and glycosidic group, and the glycosidic group is selected from glucosyl, rhamnosyl, rutinosyl or neohesperidosyl.

[0007] Preferably, the flavonoid compound is selected from one or more compounds shown in Formula I-1, Formula I-2 and Formula I-3: Formula I-1.

[0008] Formula I-2.

[0009] Formula I-3.

[0010] Preferably, the pests are piercing-sucking pests and rasping-sucking pests; more preferably, the piercing-sucking pest is the pea aphid ( Acyrthosiphon pisum The rasping-sucking pest is the horn-toothed thrips ( ). Odontothrips loti ).

[0011] The present invention also has the following technical features: This invention also protects a method for preparing flavonoids as shown in Formula I-1. This method involves extraction, column purification, acid hydrolysis, and recrystallization to extract and obtain flavonoids as shown in Formula I-1 from alfalfa. Specifically, it includes the following steps: Step 1.1: Take a dry sample of the above-ground parts of alfalfa, grind and crush it, sieve it, collect the powder passing through the sieve, and store it in the dark for later use.

[0012] Step 1.2: Add a mixture of ethanol and water to the alfalfa powder and perform reflux extraction; after extraction, filter, repeat the above reflux extraction operation on the filter residue multiple times, and combine all the extract filtrates.

[0013] Step 1.3: After the filtrate is extracted and concentrated under reduced pressure, a crude concentrate containing flavonoids is obtained. The crude concentrate is loaded onto an adsorption column and eluted with water. After the eluent shows no sugar reaction, it is eluted with a mixed solvent of ethanol and water. The eluent is collected and concentrated again under reduced pressure until there is no alcohol odor, thus obtaining a refined flavonoid concentrate.

[0014] Step 1.4: Add hydrochloric acid solution to the flavonoid concentrate to carry out the hydrolysis reaction.

[0015] Step 1.5: After hydrolysis, the reaction solution is naturally cooled to room temperature, and then extraction, washing, and drying are performed sequentially.

[0016] Step 1.6: Concentrate the dried organic phase under reduced pressure to obtain the crude product.

[0017] Step 1.7: Add a mixed solvent of ethanol and water to the crude product and stir until the crude product is completely dissolved to obtain a hot solution.

[0018] Step 1.8: Slowly add deionized water dropwise to the hot solution while stirring until the solution becomes slightly turbid; then let the solution stand and refrigerate to allow crystals to slowly precipitate.

[0019] Step 1.9: After crystallization is complete, filter and collect the precipitated crystals; then wash and dry them in sequence to finally obtain the flavonoid compound shown in Formula I-1.

[0020] Specifically, in step 1.2, the volume ratio of ethanol to water in the mixed solvent is 2 to 5:1; preferably 3:1.

[0021] Specifically, in step 1.2, the ratio of alfalfa powder to mixed solvent is 1g:10-20 mL; preferably 1g:15 mL.

[0022] Specifically, in step 1.2, the reflux extraction conditions are: reflux extraction at 60–80℃ for 1–2 h; preferably, reflux extraction at 70℃ for 1.5 h.

[0023] Specifically, in step 1.3, the conditions for vacuum concentration are: vacuum concentration at 50–55°C and a vacuum degree of 0.08–0.09 MPa.

[0024] Specifically, in step 1.3, the adsorption column is an AB-8 type macroporous adsorption resin column.

[0025] Specifically, in step 1.3, the conditions for elution with water are: using a deionized water gradient elution with a flow rate of 2-3 BV / h.

[0026] Specifically, in step 1.3, the volume ratio of ethanol to water in the mixed solvent is 2 to 5:1; preferably 4:1.

[0027] Specifically, in step 1.4, the concentration of the hydrochloric acid solution is 3 mol / L.

[0028] Specifically, in step 1.4, the hydrolysis reaction is carried out under the following conditions: stirring in a 90°C constant temperature water bath for 2 hours.

[0029] Specifically, in step 1.5, the extraction, washing, and drying process is as follows: an equal volume of ethyl acetate is added for extraction, the mixture is shaken thoroughly and allowed to stand for separation, and the upper organic phase is collected; the lower aqueous phase is extracted repeatedly, all organic phases are combined, the organic phase is washed with deionized water until the pH is neutral, anhydrous sodium sulfate is added and allowed to stand for drying, and the anhydrous sodium sulfate is removed by filtration.

[0030] Specifically, in step 1.6, the conditions for vacuum concentration are: vacuum concentration to near dryness at 50°C and a vacuum degree of 0.08 MPa.

[0031] Specifically, in step 1.7, the ratio of crude product to mixed solvent is 1g:15-25 mL; preferably 1g:20 mL.

[0032] Specifically, in step 1.7, the volume ratio of ethanol to water in the mixed solvent is 16 to 19:1; preferably 19:1.

[0033] Specifically, in step 1.7, the temperature during stirring is 60–65°C.

[0034] Specifically, in step 1.8, the conditions for static refrigeration are: standing at 0–4°C for 6–10 hours.

[0035] Specifically, in step 1.9, the washing conditions are as follows: wash the crystals 2 to 3 times with a mixture of ice-cold ethanol and water at a volume ratio of 7:3.

[0036] Specifically, in step 1.9, the drying conditions are: drying at 50°C for 4 hours.

[0037] The present invention also protects a composition containing flavonoids as shown in Formula I, which may be a wettable powder, a soluble liquid, or an emulsion.

[0038] Specifically and optionally, the composition is a wettable powder comprising: 10-25 wt% of a flavonoid compound as shown in Formula I, 5-8 wt% of a dispersant, 2-4 wt% of a wetting agent, 1-2 wt% of a stabilizer, and the balance being a solid carrier, with the total mass of the raw materials being 100 wt%.

[0039] Specifically, in the wettable powder, the flavonoid compound is selected from one or more of the compounds shown in Formula I-1, Formula I-2 and Formula I-3; the dispersant is selected from one or more of alkyl naphthalene sulfonate formaldehyde condensate and sodium lignin sulfonate; the wetting agent is selected from one or more of saponin and sodium dodecyl sulfate; the stabilizer is selected from one or more of epoxidized soybean oil and 2,6-di-tert-butyl-p-cresol; and the solid carrier is selected from one or more of diatomaceous earth, bentonite and kaolin.

[0040] Most preferably, the wettable powder is composed of 25 wt% of the compound shown in Formula I-1, 8 wt% of alkylnaphthalene sulfonate formaldehyde condensate, 2 wt% of saponin, 2 wt% of epoxidized soybean oil and 63 wt% of diatomaceous earth; or of 20 wt% of the compound shown in Formula I-2, 6 wt% of sodium lignosulfonate, 4 wt% of sodium dodecyl sulfate, 1.5 wt% of 2,6-di-tert-butyl-p-cresol and 68.5 wt% of bentonite; or of 10 wt% of the compound shown in Formula I-3, 5 wt% of sodium lignosulfonate, 3 wt% of sodium dodecyl sulfate, 1.0 wt% of 2,6-di-tert-butyl-p-cresol and 81 wt% of kaolin.

[0041] The present invention also protects a method for preparing the wettable powder described above, the method comprising: mixing flavonoids, dispersants, wetting agents, stabilizers and solid carriers evenly, and then pulverizing them to a particle size D90≤15μm to obtain the wettable powder.

[0042] Specifically and optionally, the composition is a soluble liquid comprising: 10–25 wt% of a flavonoid compound as shown in Formula I, 5–10 wt% of an emulsifier, 0.3–2 wt% of an antioxidant, and the balance being water, with the total mass of the raw materials being 100 wt%. The emulsifier is one or more mixtures of alkylphenol polyoxyethylene ether, benzylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and castor oil polyoxyethylene ether.

[0043] The present invention also protects a method for preparing the above-described soluble liquid, the method comprising: mixing flavonoids, emulsifiers, antioxidants and water, stirring until completely dissolved, and filtering to obtain the soluble liquid.

[0044] Specifically and optionally, the composition is an aqueous emulsion comprising: 10–25 wt% of a flavonoid compound as shown in Formula I, 5–10 wt% of an emulsifier, 0.3–2 wt% of an antioxidant, 10–25 wt% of an organic solvent, and the balance being water, with the total mass of the raw materials being 100 wt%. The emulsifier is one or more selected from alkylphenol polyoxyethylene ether, benzylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and castor oil polyoxyethylene ether; the organic solvent is one or more selected from ethanol, isopropanol, xylene, and DMSO.

[0045] The present invention also protects a method for preparing the above-described water-based emulsion, the method comprising: mixing a flavonoid compound, an emulsifier, an antioxidant, an organic solvent, and water.

[0046] Compared with the prior art, the present invention has the following technical effects: (I) High insecticidal activity: Indicators such as aphid survival rate and corrected control efficacy show that, at different treatment concentrations (75-1000 mg / L), the aphid survival rate continued to decrease with increasing concentration and treatment time, while the control efficacy increased. Specifically, the 1000 mg / L treatment group showed the lowest survival rate after 48 hours, significantly lower than the control group; and the high-concentration treatment groups (e.g., 1000 mg / L, 500 mg / L) exhibited significantly better corrected control efficacy and population reduction rates than the low-concentration groups. In summary, the flavonoids of this invention possess high insecticidal activity against aphids, and their activity significantly increases with prolonged treatment time and concentration, demonstrating outstanding application value in the field of aphid control.

[0047] (II) It can effectively reduce feeding damage to thrips and alleviate symptoms such as silver spots and deformities on leaves.

[0048] (III) Good crop safety: At effective control concentrations, the compound had no significant adverse effects on alfalfa's plant height, stem diameter, biomass, branch number, and other growth indicators, nor did it affect its quality indicators such as crude protein, soluble sugar, and fiber content, or its photosynthetic performance. Furthermore, the compound did not inhibit alfalfa seed germination or maize germination. Under different concentration treatments, the germination rate, germination potential, and germination index of the seeds showed no significant differences compared to the blank control group, indicating that it has good safety for crops at all growth stages from germination to maturity.

[0049] (IV) Excellent environmental compatibility: The compounds of this invention are derived from plant secondary metabolites and have the characteristics of low toxicity, low residue, easy degradation and strong target specificity. They are in line with the development direction of green pesticides, help reduce the use of chemical pesticides, alleviate the development of pesticide resistance and promote sustainable agricultural development.

[0050] (V) In summary, this invention provides a new material basis and technical approach for developing efficient, safe and environmentally friendly plant-derived insecticides. Attached Figure Description

[0051] Figure 1 The chromatogram is of the compound of formula I-1 extracted from alfalfa.

[0052] Figure 2 The effects of different concentrations of the exogenous compound shown in formula I-1 on the survival and reproduction rate of pea aphids were demonstrated.

[0053] Figure 3 The study demonstrated the control effects of different concentrations of the exogenous compound I-1 on alfalfa pea aphids.

[0054] Figure 4 The effects of different concentrations of the exogenous compound I-2 on the survival rate of pea aphids were demonstrated.

[0055] Figure 5 The study demonstrated the control effects of different concentrations of the exogenous compound I-2 on alfalfa pea aphids.

[0056] Figure 6 The effects of different concentrations of the exogenous compound I-3 on the survival rate of pea aphids were demonstrated.

[0057] Figure 7 The study demonstrated the control effects of different concentrations of the exogenous compound I-3 on alfalfa pea aphids.

[0058] Figure 8 The effects of different concentrations of the exogenous compound shown in formula I-2 on alfalfa seed germination were demonstrated.

[0059] Figure 9The effects of different concentrations of the exogenous compound shown in formula I-2 on maize seed germination are demonstrated.

[0060] Figure 10 The effects of different concentrations of the exogenous compound shown in formula I-2 on the growth and development of alfalfa were demonstrated.

[0061] Figure 11 The effects of different concentrations of the exogenous compound shown in formula I-2 on alfalfa photosynthesis are demonstrated.

[0062] Figure 12 The effects of different concentrations of the exogenous compound I-2 on thrips feeding were demonstrated.

[0063] The specific content of the present invention will be further explained in detail below with reference to the embodiments. Detailed Implementation

[0064] It should be noted that all reagents used in this invention, unless otherwise specified, are reagents known in the art.

[0065] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0066] Example 1: This embodiment provides a flavonoid compound with the following chemical structural formula: Formula I.

[0067] In the formula: R1, R2 and R3 are independently selected from hydrogen, hydroxyl, C1-C6 alkoxy, glycosidic group; R4 is selected from hydrogen, methyl and glycosidic group, and the glycosidic group is selected from glucosyl, rhamnosyl, rutinosyl or neohesperidosyl.

[0068] As a specific embodiment, the flavonoids are selected from compounds represented by the following formulas: Formula I-1 (CAS No.: 520-33-2), Formula I-2 (CAS No.: 520-27-4), and Formula I-3 (CAS No.: 7085-55-4): Formula I-1.

[0069] Formula I-2.

[0070] Formula I-3.

[0071] Example 2: This embodiment provides a method for preparing the flavonoid compound shown in Formula I-1 of Example 1. The method specifically includes the following steps: Step 1.1: Take a dry sample of the above-ground parts of alfalfa, grind it using a grinder, pass it through a 40-mesh sieve, collect the powder that passes through the sieve, and put it into a brown sealed bag to keep it away from light for later use.

[0072] Step 1.2: Add 75% ethanol solution to alfalfa powder at a material-to-liquid ratio of 1:15 (g / mL), place in a constant temperature water bath reflux device, and reflux extract at 70℃ for 1.5 h; after extraction, filter, repeat the above reflux operation twice on the filter residue, and combine the filtrates from the three extractions.

[0073] Step 1.3: Transfer the combined extract filtrate to a rotary evaporator and concentrate under reduced pressure at 50–55°C and 0.08–0.09 MPa to recover the ethanol solvent and obtain a crude concentrate of flavonoids. Load the crude concentrate onto a pretreated AB-8 macroporous adsorption resin column and elute with a gradient of deionized water (flow rate 2–3 BV / h). After the eluent shows no sugar reaction, elute the target components with 80% ethanol solution, collect the eluent, and concentrate it again under reduced pressure until there is no alcohol odor.

[0074] Step 1.4: Add 3 mol / L hydrochloric acid solution to the flavonoid concentrate and stir in a 90℃ constant temperature water bath for 2 h for hydrolysis.

[0075] Step 1.5: After hydrolysis, the reaction solution is naturally cooled to room temperature, and an equal volume of ethyl acetate is added for extraction. After thorough shaking, the mixture is allowed to stand and separate into layers. The upper organic phase is collected. The lower aqueous phase is extracted three times. All organic phases are combined and washed with deionized water until the pH is neutral. Anhydrous sodium sulfate is added and the mixture is allowed to stand and dry for 4 hours. The anhydrous sodium sulfate is then removed by filtration.

[0076] Step 1.6: Transfer the dried organic phase to a rotary evaporator and concentrate it to near dryness under reduced pressure at 50°C and a vacuum of 0.08 MPa.

[0077] Step 1.7: Add 95% ethanol solution again at a material-to-liquid ratio of 1:20 (g / mL), place in a constant temperature water bath at 60-65℃, and stir magnetically until the crude product is completely dissolved.

[0078] Step 1.8: Slowly add deionized water dropwise to the above hot solution while stirring until the solution becomes slightly turbid; then transfer the solution to a refrigerator at 4°C and let it stand for 8 hours to allow the compound shown in Formula I-1 to slowly precipitate.

[0079] Step 1.9: After crystallization, filter using a Buchner funnel and collect the precipitated compound I crystals; wash the crystals 2-3 times with a small amount of ice-cold ethanol-water mixture (volume ratio 7:3) to remove surface impurities; place the washed crystals in a 50℃ vacuum drying oven and dry for 4 h, then analyze by liquid chromatography (HPLC). Figure 1After identification, it was confirmed that pure flavonoid compounds with a purity of ≥95% as shown in Formula I-1 were obtained.

[0080] Example 3: This embodiment provides a method for preparing a wettable powder containing the flavonoid compound of Example 1, which specifically includes the following steps: Step 2.1, Preparation of wettable powder I-1: Take the compound shown in Formula I-1, alkyl naphthalene sulfonate formaldehyde condensate, saponin, epoxidized soybean oil and diatomaceous earth (mass percentages of 25 wt%, 8 wt%, 2 wt%, 2 wt%, with diatomaceous earth added to 100 wt%), mix them evenly, and then pulverize them with an air jet mill to a particle size D90≤15 μm to obtain wettable powder I-1.

[0081] Step 2.2, Preparation of wettable powder I-2: Take the compound shown in Formula I-2, sodium lignosulfonate, sodium dodecyl sulfate, 2,6-di-tert-butyl-p-cresol (BHT) and bentonite (mass percentages of 20 wt%, 6 wt%, 4 wt%, and 1.5 wt%, respectively, with bentonite added to make up to 100 wt%), mix them evenly, and then pulverize them with an air jet mill to a particle size D90≤15μm to obtain wettable powder I-2.

[0082] Step 2.3, Preparation of wettable powder I-3: Take the compound shown in Formula I-3, sodium lignosulfonate, sodium dodecyl sulfate, 2,6-di-tert-butyl-p-cresol (BHT) and kaolin (mass percentages of 10 wt%, 5 wt%, 3 wt%, and 1.0 wt%, respectively, with the kaolin added to make up to 100 wt%), mix them evenly, and then pulverize them with an air jet mill to a particle size D90≤15 μm to obtain wettable powder I-3.

[0083] Example 4: This embodiment demonstrates the application of the flavonoids from Example 1 as plant-derived insecticides for the control of piercing-sucking or rasping-sucking pests. Details are as follows: (1) Preparation of experimental materials: The plant-derived insecticides are flavonoids given in Formula I-1, Formula I-2 and Formula I-3. The wettable powder prepared in Example 3 is used for subsequent experiments.

[0084] The tested insect was the pea aphid, a pest with piercing-sucking mouthparts. Acyrthosiphon pisum ) and the rasping-sucking mouthpart pest, the horn-toothed thrips ( Odontothrips lotiPea aphids were provided by the College of Plant Protection, Northwest A&F University, and were continuously fed with fresh broad bean plants in a constant-temperature growth chamber under the following conditions: photoperiod 16 h:8 h (light:dark), day / night temperature 20±1℃, and relative humidity 70±5%. Horned thrips were collected from the Caoxinzhuang experimental field of Northwest A&F University, Yangling District, Xianyang City, Shaanxi Province. They were fed with fresh alfalfa in the laboratory and bred for multiple generations under conditions of 26±1℃, 70±5% relative humidity, and a photoperiod 12 h:12 h (light:dark) to establish a stable experimental population.

[0085] The test plant was alfalfa ( Medicago sativa The 'Ladak+' seed was provided by the Forage Stress Biology Laboratory of the College of Grassland Science and Technology, Northwest A&F University. The experiment was conducted in a constant temperature growth chamber with day and night temperatures set at 25±1℃ / 20±1℃, relative humidity at 70±5%, and a photoperiod of 16 h:8 h (light:dark). The plants were irrigated with 1 / 2 Hoagland's nutrient solution every 2 days.

[0086] (2) Evaluation of aphid-killing activity: Weigh 1 g each of wettable powder I-1, wettable powder I-2, and wettable powder I-3 (based on the total weight of the formulation), add 10 mL of water to fully dissolve and prepare a stock solution. Then, add water for serial dilution to obtain treatment groups of 75, 250, 500, and 1000 mg / L of the compounds shown in formulas I-1, I-2, and I-3, respectively. At the same time, a solvent control containing only equal amounts of dispersant, wetting agent, stabilizer, and solid carrier was set up. Each treatment was replicated 6 times. The solution of each concentration was sprayed evenly on the front and back of the plant leaves using a sprayer, until the leaves were evenly moistened without dripping. The amount of solution applied per pot was about 10 mL. After treatment, aphids were raised in a light incubator under the following conditions: photoperiod 16 h: 8 h (light: darkness), temperature (20±1)℃, and humidity (70±5)%. The number of surviving aphids and their reproductive output were investigated at 6, 12, 24, 30, 36, and 48 hours after treatment. Corrected control efficacy, population reduction rate, contact mortality rate, and median lethal concentration (LC50) were calculated. 50 ).

[0087] like Figure 2 and Figure 3 Table 1 shows that the experimental results indicate that the survival rate of aphids in each treatment group (75-1000 mg / L) continuously decreased with increasing treatment concentration and prolonged treatment time, with the 1000 mg / L treatment group showing the most significant control effect at 48 h. Multiple indicators, including corrected control efficacy, population reduction rate, and contact mortality rate, demonstrate that this compound exhibits excellent control effects on aphid populations at higher concentrations. Toxicity testing results show that the compound has a median lethal concentration (LC50) for aphids. 50The LC value decreased continuously with increasing processing time, reaching a maximum of 48 h. 50 The effective concentration was 140.80 mg / L, with a confidence interval of [24.37, 263.58] mg / L, indicating that it still possesses effective insecticidal activity at low concentrations. The chi-square test p-values ​​for the toxicity model at each time point were all greater than 0.05, indicating a good model fit and reliable results.

[0088] Table 1. Indoor bioactivity of different concentrations of exogenous compounds of formula I-1 against alfalfa pea aphids.

[0089] Note: All data in the table are mean ± standard error. Lowercase letters indicate that the differences in peer comparisons reached a significant level. P <0.05).

[0090] like Figure 4 and Figure 5 Table 2 shows that the compound represented by Formula I-2 exhibits significant biological activity against aphids, and its insecticidal effect is clearly concentration- and time-dependent. With increasing treatment concentration and prolonged treatment time, the survival rate of aphids in each treatment group (75–1000 mg / L) continuously decreased, and their reproductive rate was significantly inhibited. The corrected control efficacy and the aphid population reduction rate were both positively correlated with concentration, with the 1000 mg / L treatment group showing the best control effect at 48 h. Toxicity assays showed that the compound's median lethal concentration (LC50) against aphids... 50 The LC50 gradually decreased with increasing processing time, with the LC50 value decreasing after 48 hours. 50 The concentration was 72.07 mg / L, indicating that it still possesses good insecticidal activity at a low concentration. The contact mortality rate also increased significantly over time and with increasing concentration, further confirming that this compound has both rapid and sustained effects.

[0091] Table 2. Indoor bioactivity of different concentrations of exogenous compounds of formula I-2 against alfalfa pea aphids.

[0092] Note: All data in the table are mean ± standard error. Lowercase letters indicate that the differences in peer comparisons reached a significant level. P <0.05).

[0093] like Figure 6 and Figure 7 Table 3 shows that the experimental results indicate that the survival rate of aphids in each treatment group (75-1000 mg / L) continuously decreased with increasing treatment concentration and duration. The 1000 mg / L treatment group showed the lowest survival rate at 48 h, significantly lower than the control group. Toxicity assays showed that the compound's median lethal concentration (LC50) for aphids was... 50The LC gradually decreased with increasing processing time, reaching a maximum at 48 h. 50 The value was 73.00 mg / L, indicating that it still has significant insecticidal activity at a low concentration. Throughout the treatment process, the chi-square test results of the toxicity model at each time point showed that the model fit was acceptable (P>0.05), indicating that the data were reliable.

[0094] Table 3. Indoor bioactivity of different concentrations of exogenous compounds of formula I-3 against alfalfa pea aphids.

[0095] Note: All data in the table are mean ± standard error. Lowercase letters indicate that the differences in peer comparisons reached a significant level. P <0.05).

[0096] (4) Determination of the inhibitory effect of the compound shown in Formula I-2 on the bioactivity of thrips: Four treatment groups were set up with the compound shown in Formula I-2 at concentrations of 75, 250, 500, and 1000 mg / L, with a solvent control containing equal amounts of dispersant, wetting agent, stabilizer, and solid carrier. Each treatment was replicated six times. The solution was sprayed evenly until all leaves of the alfalfa plant were moistened, approximately 10 mL per pot. Twenty adult thrips were inoculated onto each plant, and the damage to the plants was observed and phenotypically recorded on the 7th day after treatment.

[0097] like Figure 12 As shown in the figure, the statistical results indicate that the anti-thrips effect is better with increasing concentration gradient.

[0098] Furthermore, this invention also provides safety evaluation experiments for the compounds shown in Formula I-2: (1) Seed germination evaluation: Four treatment groups with concentrations of compounds shown in Formula I-2 of 75, 250, 500 and 1000 mg / L were set up, with a solvent control containing equal amounts of dispersant, wetting agent, stabilizer and solid carrier. Each treatment was replicated 30 times. Healthy and plump alfalfa seeds and corn seeds were disinfected with sodium hypochlorite solution for 5 min, rinsed 3 times with clean water, and then soaked in the above-mentioned concentrations of solutions for 30 min respectively. After treatment, the seeds were placed under suitable conditions for germination test. The number of germinations was observed and recorded daily for 5 consecutive days. The germination rate was calculated and the germination process was recorded by photograph. The entire germination test was carried out in a constant temperature growth chamber with day and night temperatures set at (25±1)℃ / (20±1)℃, relative humidity at (70±5)%, and photoperiod of 16 h:8 h (light:dark).

[0099] like Figure 8 and Figure 9 As shown in Tables 4 and 5, the experimental results indicate that the control and different concentrations of the compound shown in Formula I-2 have no inhibitory effect on seed germination.

[0100] Table 4. Effects of different concentrations of exogenous compounds of formula I-2 on alfalfa seed germination.

[0101] Note: All data in the table are mean ± standard error. Lowercase letters indicate that the differences in peer comparisons reached a significant level. P <0.05).

[0102] Table 5. Effects of different concentrations of exogenous compound I-2 on maize seed germination.

[0103] Note: All data in the table are mean ± standard error. Lowercase letters indicate that the differences in peer comparisons reached a significant level. P <0.05).

[0104] (2) Evaluation of plant growth and development: Four treatment groups were set up with concentrations of the compound shown in Formula I-2: 75, 250, 500, and 1000 mg / L. A solvent control containing equal amounts of dispersant, wetting agent, stabilizer, and solid carrier was used. Each treatment was replicated 15 times. The entire plant was sprayed evenly with a handheld sprayer until the leaves were completely wetted, with about 10 mL per pot. Treatment began on day 14 of the alfalfa seedling stage, with spraying every 2 days for a total of 10 treatments. Plant height, stem diameter, and number of internodes were measured on days 14, 20, 26, 32, 38, and 44. The number of branches was counted on days 20, 26, 32, 38, and 44. Monitoring continued until the beginning of flowering, and plant quality indicators and photosynthetic parameters were uniformly measured at the end of the period. The experiment was conducted under the following conditions: temperature (25±1)℃ / (20±1)℃, humidity (70±5)%, and photoperiod of 16 h:8 h (light: darkness). Half of Hogland's nutrient solution was applied every 2 days.

[0105] like Figure 10 and Figure 11 As shown in Table 6, the experimental results indicate that the control and different concentrations of the compound represented by Formula I-2 had no significant effect on plant growth, development, quality, and photosynthesis.

[0106] Table 6. Effects of different concentrations of exogenous compounds (I-2) on alfalfa quality

[0107] Note: All data in the table are mean ± standard error. Lowercase letters indicate that the differences in peer comparisons reached a significant level. P <0.05).

Claims

1. The application of flavonoids in the control of plant pests, characterized in that, The flavonoids mentioned are shown in Formula I: Formula I; In the formula: R1, R2 and R3 are independently selected from hydrogen, hydroxyl, C1-C6 alkoxy, glycosidic group; R4 is selected from hydrogen, methyl and glycosidic group, and the glycosidic group is selected from glucosyl, rhamnosyl, rutinosyl or neohesperidosyl.

2. The application as described in claim 1, characterized in that, The flavonoids mentioned are selected from one or more of the compounds shown in Formula I-1, Formula I-2 and Formula I-3: Formula I-1; Formula I-2; Formula I-3.

3. The application as described in claim 1, characterized in that, The pests are piercing-sucking and rasping-sucking insects; the plant is alfalfa.

4. A method for preparing a flavonoid compound as shown in Formula I-1, characterized in that, Flavonoids, as shown in Formula I-1, were extracted from alfalfa by means of extraction, column purification, acid hydrolysis and recrystallization.

5. The method for preparing flavonoids according to claim 4, characterized in that, The method specifically includes the following steps: Step 1.1: Take a dry sample of the above-ground parts of alfalfa, grind and crush it, sieve it, collect the powder passing through the sieve, and store it in the dark for later use. Step 1.2: Add a mixed solvent of ethanol and water to alfalfa powder and perform reflux extraction; after extraction, filter, repeat the above reflux extraction operation on the filter residue multiple times, and combine all the extract filtrates; Step 1.3: After the filtrate is concentrated under reduced pressure, a crude concentrate containing flavonoids is obtained. The crude concentrate is loaded onto an adsorption column and eluted with water. After the eluent shows no sugar reaction, it is eluted with a mixed solvent of ethanol and water. The eluent is collected and concentrated under reduced pressure again until there is no alcohol odor, thus obtaining a refined flavonoid concentrate. Step 1.4: Add hydrochloric acid solution to the flavonoid concentrate to carry out the hydrolysis reaction; Step 1.5: After hydrolysis, the reaction solution is naturally cooled to room temperature, and extraction, washing, and drying are performed sequentially. Step 1.6: Concentrate the dried organic phase under reduced pressure to obtain the crude product; Step 1.7: Add a mixed solvent of ethanol and water to the crude product and stir until the crude product is completely dissolved to obtain a hot solution; Step 1.8: Slowly add deionized water dropwise to the hot solution while stirring until the solution becomes slightly turbid; then let the solution stand and refrigerate to allow crystals to slowly precipitate. Step 1.9: After crystallization is complete, filter and collect the precipitated crystals; then wash and dry them in sequence to finally obtain the flavonoid compound shown in Formula I-1.

6. A composition, characterized in that, It contains flavonoids as shown in Formula I; the formulations of the composition include wettable powders, soluble liquids and emulsions.

7. The composition according to claim 8, characterized in that, The wettable powder comprises: 10–25 wt% flavonoids, 5–8 wt% dispersant, 2–4 wt% wetting agent, 1–2 wt% stabilizer, and the balance being a solid carrier, with the total mass of the raw materials being 100 wt%. The flavonoids mentioned are selected from one or more of the compounds shown in Formula I-1, Formula I-2 and Formula I-3; The dispersant is selected from one or more of alkyl naphthalene sulfonate formaldehyde condensate and sodium lignosulfonate; The wetting agent is selected from one or more of saponins and sodium dodecyl sulfate; The stabilizer is selected from one or more of epoxidized soybean oil and 2,6-di-tert-butyl-p-cresol; The solid carrier is selected from one or more of diatomaceous earth, bentonite, and kaolin.

8. The composition according to claim 7, characterized in that, The particle size D90 of wettable powder is ≤15μm.

9. The composition according to claim 8, characterized in that, The soluble liquid comprises: 10-25 wt% of a flavonoid compound as shown in Formula I, 5-10 wt% of an emulsifier, 0.3-2 wt% of an antioxidant, and the balance being water, with the total mass of the raw materials being 100 wt%; wherein the emulsifier is one or a mixture of alkylphenol polyoxyethylene ether, benzylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and castor oil polyoxyethylene ether. The water-in-oil emulsion comprises: 10-25 wt% of a flavonoid compound as shown in Formula I, 5-10 wt% of an emulsifier, 0.3-2 wt% of an antioxidant, 10-25 wt% of an organic solvent, and the balance being water, with the total mass of the raw materials being 100 wt%; wherein the emulsifier is one or more of alkylphenol polyoxyethylene ether, benzylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and castor oil polyoxyethylene ether; and the organic solvent is one or more of ethanol, isopropanol, xylene, and DMSO.

10. The use of the composition according to any one of claims 6 to 9 in the control of plant pests.

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