Calyx tongue extract with insect antifeedant activity as well as preparation method and application of Calyx tongue extract

Abstract

The invention discloses a flat calyx moss extract with insect antifeedant activity as well as a preparation method and application thereof, and belongs to the field of pest repellent. According to the invention, research on insect antifeedant activity is carried out on Radula Complanata (L.) Dumor, extraction is carried out by adopting a heating reflux method, then extraction is carried out by adopting solvents with different polarities to obtain a petroleum ether phase, an ethyl acetate phase, an n-butanol phase and a water phase, and the antifeedant activity is screened by using plutella xylostella and prodenia litura, so that the method for screening the antifeedant activity of Radula Complanata (L.) Dumor is provided for screening the antifeedant activity of Radula Complanata (L.) Dumor. Researches show that the extract of each phase of calyx tongue has insect antifeedant activity, especially the petroleum ether phase and the ethyl acetate phase have the highest antifeedant activity on plutella xylostella, and a new thought is provided for biological control.

Description

Technical Field

[0001] This invention belongs to the field of insect repellents, specifically relating to an extract of *Lysimachia clethroides* with insect antifeeding activity, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance some understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art.

[0003] Diamondback moth larvae are a global pest of cruciferous vegetables, particularly damaging crops such as cabbage, kale, cauliflower, and rapeseed. They reproduce rapidly, develop strong pesticide resistance, and are difficult to control, severely impacting vegetable yield and quality. The beet armyworm, belonging to the Noctuidae family of Lepidoptera, is another major global agricultural pest. Its larvae primarily feed on plant leaves. Young larvae congregate on the underside of leaves, leaving behind a transparent upper epidermis; after the third instar, they disperse and enter a voracious feeding stage, biting notches, holes, and even completely consuming leaves, leaving only the main vein. In severe cases, they can also bore into fruits, tender stems, and flower buds, causing enormous yield and economic losses.

[0004] With the long-term and extensive use of chemical pesticides, problems such as pest resistance, pesticide residues, and environmental pollution have become increasingly prominent. Developing new, highly efficient, low-toxicity, and environmentally friendly green pesticides has become an urgent need in the field of sustainable agricultural development. Against this backdrop, searching for lead compounds with insecticidal or antifeedant activities from plant-derived natural products is one of the important directions in the research and development of biopesticides.

[0005] Currently, as environmentally sensitive organisms, bryophytes not only play a significant indicative role in heavy metal pollution and atmospheric changes, but their unique secondary metabolites also demonstrate unique advantages in agricultural pest control. The secondary metabolites contained in bryophytes include terpenes, aromatic compounds, polyacetyl groups, and alkaloids, exhibiting a wide range of biological activities. However, compared to higher plants, research on the biological activities of bryophytes, especially their specific chemical components, remains relatively weak, and their potential for industrial application has not yet been fully explored.

[0006] Plants of the Apocynaceae family are an important group of bryophytes. Although existing research indicates that they contain a variety of secondary metabolites, there are few reports on their specific active ingredients, especially in their application in agricultural pest control. Currently, the screening of insect-repellent active ingredients mostly focuses on extracts from higher plants or microorganisms, and systematic research and development of Apocynaceae plants in this field is still lacking.

[0007] Therefore, there is an urgent need in this field for a new technical solution that can efficiently and selectively screen and extract active ingredients from bryophyte resources, identify their active parts, and provide a scientific basis and material foundation for developing novel, green insect repellents or biopesticides based on bryophyte sources, so as to make up for the shortcomings of existing technologies. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a method for treating *Platycodon grandiflorus* (a type of lichen). Radula complanata (L.) Dumort. (20240728001) Research was conducted on insect antifeedant activity. A crude extract was obtained by heating and refluxing 85% ethanol with water. Then, it was extracted with different polar solvents to obtain petroleum ether phase, ethyl acetate phase, n-butanol phase and aqueous phase mixture. Diamondback moth and Spodoptera litura were used as model insects to evaluate the antifeedant activity of different parts. The results showed that all phases of the extract of *Platycodon grandiflorus* had insect antifeedant activity, especially the petroleum ether phase and ethyl acetate phase had the highest antifeedant activity against diamondback moth, providing a new approach for biological control.

[0009] The technical solution adopted in this invention is as follows: In a first aspect of the present invention, a method for preparing an extract of *Platycodon grandiflorus* with insect antifeeding activity is provided, the method comprising the following steps: The *Platycodon grandiflorus* was extracted several times by reflux with an ethanol solution, and the extracts were combined. The extracts were then rotary evaporated to obtain an extract paste. The extract paste was dissolved and extracted separately using petroleum ether, ethyl acetate, n-butanol, and / or water as extraction solvents. After extraction, extracts of different polar fractions of *Platycodon grandiflorus* were obtained. After concentration, an extract paste was obtained, which is the extract of different polar fractions of *Platycodon grandiflorus* with insect antifeedant activity.

[0010] In one or more embodiments of the present invention, the volume fraction of the ethanol solution is 80-85%, preferably 85%.

[0011] In one or more embodiments of the present invention, the liquid-liquid extraction method is as follows: the dissolved extract solution is first extracted with petroleum ether to obtain an aqueous phase I and a petroleum ether phase; then, ethyl acetate is added to aqueous phase I for extraction to obtain an aqueous phase II and an ethyl acetate phase; finally, n-butanol is added to aqueous phase II for extraction to obtain an aqueous phase III and a n-butanol phase. The obtained petroleum ether phase, ethyl acetate phase, n-butanol phase, and aqueous phase III are evaporated separately to obtain petroleum ether extract, ethyl acetate extract, n-butanol extract, and aqueous extract, respectively, which are the extracts of *Lactuca tataricus* with insect antifeedant activity. Among them, the petroleum ether extract and the ethyl acetate extract have particularly significant antifeedant activity.

[0012] Preferably, the volume ratio of the extract solution to petroleum ether is (1~3):3.

[0013] In one or more embodiments of the present invention, the extraction solvent is petroleum ether or ethyl acetate.

[0014] In a second aspect of the invention, an extract of *Lysimachia clethroides* prepared by the above method is provided.

[0015] In a third aspect of the invention, the use of the *Platycodon grandiflorus* extract in the preparation of insect repellents is provided.

[0016] In one or more embodiments of the present invention, the pest repellent has insect antifeeding activity.

[0017] In one or more embodiments of the present invention, the pests repelled by the pest repellent are diamondback moth larvae and / or beet armyworm larvae.

[0018] In a fourth aspect of the present invention, an insect repellent is provided, which is prepared by dissolving the extract of the *Platycodon grandiflorus* in methanol to a concentration of 1-1000 μg / mL.

[0019] In one or more embodiments of the present invention, the concentration is 100~500 μg / mL.

[0020] Compared with the related technologies known to the inventors, one of the technical solutions of the present invention has the following beneficial effects: From the perspective of ecological and agricultural sustainable development, this invention has dual significance: on the one hand, as a widely distributed bryophyte, *Phyllostachys pubescens* has abundant and environmentally friendly secondary metabolites, providing green and low-toxicity natural materials for the development of novel plant-derived pesticides, which helps alleviate the residual pollution and resistance problems caused by traditional chemical pesticides; on the other hand, the research results expand the application scope of bryophytes in the field of biological control, confirm the unique value of bryophyte resources in integrated pest management, and open up new paths for the resource development of bryophytes.

[0021] This invention focuses on the plant *Platycodon grandiflorus*, systematically screening and evaluating its insect-repellent active ingredients. Through extraction, separation, polar extraction, and bioactivity assays, it was confirmed that different polar extracts of *Platycodon grandiflorus* exhibit significant anti-feeding activity against both diamondback moth and beet armyworm. Experimental results show that petroleum ether, ethyl acetate, n-butanol, and aqueous extracts at different concentrations can inhibit insect feeding, with particularly pronounced anti-feeding effects against diamondback moth. High-concentration treatments achieved an anti-feeding rate exceeding 60% within 72 hours, demonstrating good potential for biological control. Compared to beet armyworm, *Platycodon grandiflorus* extracts show more stable and efficient effects against diamondback moth, which is related to differences in the pest's feeding habits or metabolic mechanisms, providing important clues for the subsequent development of targeted anti-feeding agents. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 Bar chart of feeding area of ​​diamondback moth in petroleum ether phase. Different letters indicate significant differences between means, P≤0.05 (test), and the values ​​are the mean (n=3).

[0024] Figure 2 Different concentrations of petroleum ether were used to treat diamondback moth feeding phenomena.

[0025] Figure 3 Bar chart of the feeding area of ​​diamondback moth in ethyl acetate phase. Different letters indicate significant differences between means, P≤0.05 (test), and the values ​​are the mean (n=3).

[0026] Figure 4 Different concentrations of ethyl acetate were used to treat diamondback moth feeding behavior.

[0027] Figure 5 Bar chart of the feeding area of ​​diamondback moth in the n-butanol phase. Different letters indicate significant differences between means, P≤0.05 (test), and the values ​​are the mean (n=3).

[0028] Figure 6 Different concentrations of n-butanol were used to treat the diamondback moth feeding behavior.

[0029] Figure 7 Bar chart of feeding area of ​​diamondback moth in the water phase. Different letters indicate significant differences between means. P≤0.05 (test). The values ​​are the mean (n=3).

[0030] Figure 8 Different concentrations of aqueous phase were used to treat the diamondback moth feeding behavior.

[0031] Figure 9 Bar chart of feeding area of ​​Spodoptera litura in petroleum ether phase. Different letters indicate significant differences between means, P≤0.05 (test), and the values ​​are the mean (n=3).

[0032] Figure 10 Different concentrations of petroleum ether were used to treat the feeding behavior of Spodoptera litura.

[0033] Figure 11 Bar chart of feeding area of ​​Spodoptera litura in ethyl acetate phase. Different letters indicate significant differences between means, P≤0.05 (test), and the values ​​are the mean (n=3).

[0034] Figure 12 Ethyl acetate phases were used to treat the feeding behavior of Spodoptera litura.

[0035] Figure 13 Bar chart of feeding area of ​​Spodoptera litura in n-butanol phase. Different letters indicate significant differences between means, P≤0.05 (test), and the values ​​are the mean (n=3).

[0036] Figure 14 Different concentrations of n-butanol were used to treat the feeding behavior of Spodoptera litura.

[0037] Figure 15 Bar chart of feeding area of ​​water-phase beet armyworm. Different letters indicate significant differences between means, P≤0.05 (test), and the values ​​are the mean (n=3).

[0038] Figure 16 The feeding phenomenon of Spodoptera litura under different concentrations of aqueous phase. Detailed Implementation

[0039] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0041] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0042] Example 1: 1. Experimental Materials *Radula complanata* (L.) Dumort. was collected from littered slopes along a road in the Guanshan Nature Reserve, Jiangxi Province, at E114°33′12, N28°33′20, H326m. Morphologically identified as belonging to the family Radulaceae, *Radula complanata* (L.) Dumort. is currently housed in Room 1308, Science and Technology Building, Linyi University, with the catalog number 20240728001. It is associated with the 3rd instar larvae of the diamondback moth and the beet armyworm.

[0043] 2. Experimental Methods 2.1 Extraction of Radula complanata (L.) Dumort. (family Radulaceae) To obtain the plant *Lysimachia clethroides* (of the family Lysimachia), Radula complanata (L.) Dumort. To extract the active ingredient, fresh *Pteris vittata* plant samples were pulverized. 1064 g of the pulverized *Pteris vittata* was accurately weighed and placed in a 5 L round-bottom flask. Sufficient 85% (v / v) ethanol solution was added until the *Pteris vittata* was completely submerged. The mixture was soaked at room temperature for 12 hours, then a reflux condenser was connected, and the mixture was extracted three times by reflux in an 85°C water bath, each time for 2.5 hours. After extraction, the mixture was cooled and filtered. All filtrates were combined and concentrated under reduced pressure using a rotary evaporator at a 45°C water bath until a thick, alcohol-free extract was obtained. The resulting extract was completely dissolved in 1000 mL of purified water to obtain an aqueous solution of *Pteris vittata*, which was used as the sample for subsequent fractional extraction.

[0044] 2.2 Polar Solution Extraction Experiment Petroleum ether extraction: 70 mL of an aqueous solution containing extract of *Platycodon grandiflorus* (family Platycodonaceae) and 210 mL of petroleum ether were added to a 500 mL separatory funnel. The mixture was shaken and mixed 5 times. After standing and separating the layers, the aqueous phase and the petroleum ether phase were separated. The extraction was repeated 15 times, and the petroleum ether phase and the combined aqueous phase were combined.

[0045] Ethyl acetate extraction: Take the separated aqueous phase, add 210 mL of ethyl acetate, and extract 8 times in the same way. Combine the ethyl acetate phase and the combined aqueous phase.

[0046] n-Butanol extraction: The remaining aqueous phase was extracted three times with 210 mL of n-butanol, and the n-butanol phase and the final aqueous phase were collected.

[0047] Concentration process: The petroleum ether phase, ethyl acetate phase, n-butanol phase and final aqueous phase obtained after extraction were evaporated into extracts by rotary evaporation.

[0048] The remaining aqueous solution containing the extract of *Platycodon grandiflorus* (family Platycodonaceae) was subjected to fractional extraction using this method. The following data were obtained: Table 1 Extract Weight

[0049] The four-phase extract obtained after extraction and rotary evaporation was dissolved in methanol and then transferred to vials. The extract was dried to obtain a sample powder of the four phases of *Epipremnum aureum*, then sealed and stored for later use.

[0050] 2.3 Insect refusal to eat experiment Comparative studies revealed that diamondback moth larvae and beet armyworms had the highest feeding rates on rapeseed leaves. A 1.5cm diameter punch was used to punch holes in the rapeseed leaves, resulting in 672 holes. Eight leaves were placed in round petri dishes, marked, and awaited further processing.

[0051] The research on insect antifeedant activity generally adopts the leaf disc method. The specific method commonly used is to put the leaf discs treated with the agent and the blank control into petri dishes respectively. After a period of time, the feeding area of the insects is determined by measuring the area of the leaf discs, so as to measure the non-selective antifeedant rate.

[0052] Dissolve 2 ml of methanol in the four-phase medicine of Radula complanata, and divide it into three different concentrations: high, medium and low. The specific concentration data are as follows: Table 2 Concentrations of medicines added to the leaves for insect antifeedance

[0053] Add the medicine to the round petri dish containing the leaves, soak the round leaves in different medicines for 30 s (8 leaves in each group, and set three parallel experiments), and dry them. After the methanol on the leaves dries, put them into a plastic petri dish lined with absorbent filter paper. Put 8 leaves in each petri dish, and put 5 third-instar Plutella xylostella or Spodoptera litura larvae in each petri dish. Drill holes in the cover of the petri dish to ensure that the hole diameter is not large enough for the larvae to pass through, but also ensure that the larvae are not in a completely airtight space. Put the petri dish containing the larvae into an environment with moist air and conduct dark treatment. Measure the leaf area at 24 h, 48 h and 72 h later.

[0054] 3 Results: The following are the data results of the petroleum ether phase, ethyl acetate phase, n-butanol phase and water phase, including the column chart of the average feeding area of insects and the data of insect antifeedant rate. Among them, in the significance difference test, P(F<=f)>0.05 indicates that the difference is not significant; 0.01<P(F<=f)<0.05 indicates that the difference is significant; P(F<=f)<0.01 indicates that the difference is extremely significant. There are also F values and F crit values. If F>F crit, it means the difference is significant. If F<F crit, it means there is no obvious difference, which are represented by a, b, c, d.

[0055] Antifeedant rate = (feeding area of the blank group - feeding area of the treatment group) / feeding area of the blank group * 100% ， Here, the overall feeding area of eight leaves is used to substitute into the formula for calculation.

[0056] 3.1 Experimental results of the insect antifeedant experiment on Plutella xylostella 3.1.1 Results of the petroleum ether phase Table 3 Antifeedant rate of the petroleum ether phase

[0057] Conclusion: From Figure 1 and Figure 2It was found that, compared with the control group, the average feeding area of ​​insects in different petroleum ether concentration groups decreased at 24h, 48h, and 72h, indicating that the petroleum ether extract has an inhibitory effect on insect feeding. Furthermore, as the petroleum ether concentration increased, the average feeding area of ​​insects gradually decreased. The feeding area of ​​the high-concentration petroleum ether group was significantly lower than that of the low- and medium-concentration groups at all time points, indicating that the higher the concentration, the more significant the inhibitory effect on feeding.

[0058] As shown in Table 3, under the same treatment time, the concentration of the petroleum ether extract was positively correlated with the feeding rejection rate, and higher concentrations of the extract were more effective in inhibiting insect feeding. The feeding rejection rate at high concentrations reached 60.28% after 72 hours and as high as 83.13% after 24 hours, demonstrating a rapid and sustained inhibitory effect.

[0059] 3.1.2 Results of Ethyl Acetate Phase Table 4. Ethyl acetate phase rejection rate

[0060] Conclusion: From Figure 3 and Figure 4 As can be seen, compared with the control group, the average feeding area of ​​insects was reduced at 24h, 48h, and 72h in different ethyl acetate concentration groups, indicating that the ethyl acetate extract has an inhibitory effect on insect feeding. Furthermore, the average feeding area of ​​insects gradually decreased with increasing ethyl acetate concentration.

[0061] As shown in Table 4, the non-feeding rate of medium and high concentrations (200-500 ug / ml) exceeded 50% in 24-48 hours, but decreased slightly after 72 hours. This indicates that the concentration of the ethyl acetate extract is positively correlated with the non-feeding rate, and the high concentration extract has a better effect on inhibiting insect feeding.

[0062] 3.1.3 Results of n-Butanol Phase Table 5. Refusal rate in the n-butanol phase

[0063] Conclusion: From Figure 5 and Figure 6 As can be seen, compared with the control group, the average feeding area of ​​insects decreased at 24h, 48h, and 72h in different n-butanol concentration groups, indicating that the n-butanol extract has an inhibitory effect on insect feeding. Furthermore, the average feeding area of ​​insects gradually decreased with increasing n-butanol concentration. Within each concentration group, the average feeding area of ​​insects generally increased from 24h to 72h, but the increase was relatively slower in the high-concentration group, meaning that the inhibitory effect of high-concentration n-butanol extract on insect feeding was more persistent over a longer period.

[0064] As shown in Table 5, under the same treatment time, the higher the concentration, the higher the feeding rejection rate. This demonstrates a positive correlation between the concentration of the n-butanol extract and the feeding rejection rate; higher concentrations of the n-butanol extract have a stronger ability to inhibit insect feeding.

[0065] 3.1.4 Aqueous Phase Results Table 6. Aquatic phase feeding rejection rate

[0066] Conclusion: From Figure 7 and Figure 8 It was found that, compared with the control group, the average feeding area of ​​insects decreased at 24h, 48h, and 72h in different aqueous phase concentration groups, indicating that the aqueous phase extract could inhibit insect feeding. As the aqueous phase concentration increased, the average feeding area of ​​insects gradually decreased. The feeding area of ​​the high-concentration aqueous phase group was significantly lower than that of the low- and medium-concentration groups at all time points, indicating that the higher the concentration, the stronger the inhibitory effect on insect feeding.

[0067] As can be seen from the data in Table 6, under the same treatment time, the higher the concentration, the higher the feeding rejection rate, which shows that the concentration of aqueous extract is positively correlated with the feeding rejection rate. The high concentration of aqueous extract has a more prominent effect on inhibiting insect feeding.

[0068] 3.2 Experimental Results of the Feed Rejection Experiment on the Spodoptera litura 3.2.1 Results of petroleum ether phase Table 7. Refusal rate of petroleum ether phase

[0069] Conclusion: From Figure 9 , Figure 10 As shown in Table 7, compared with the control group, the average feeding area of ​​insects in different concentrations of petroleum ether decreased at 24h, 48h, and 72h, indicating that the petroleum ether extract can inhibit insect feeding. Only the high concentration (500ug / ml) showed a significant effect at 24h, with a rejection rate as high as 87.20%, but its long-term effect was weak.

[0070] 3.2.2 Results of Ethyl Acetate Phase Table 8. Food rejection rate in ethyl acetate phase

[0071] Conclusion: From Figure 11 , Figure 12 As shown in Table 8, compared with the control group, the average feeding area of ​​insects decreased at 24h, 48h, and 72h in different ethyl acetate concentration groups, indicating that the ethyl acetate extract has an inhibitory effect on insect feeding. Within each concentration group, the refusal rate decreased significantly as the time increased from 24h to 72h, indicating that the inhibitory effect of the ethyl acetate extract weakened over time.

[0072] 3.2.3 Results of n-Butanol Phase Table 9. Refusal rate in the n-butanol phase

[0073] Conclusion: Through Figure 13 , Figure 14 According to the data in Table 9, compared with the control group, the average feeding area of ​​insects decreased at 24h, 48h, and 72h in different n-butanol concentration groups, indicating that the n-butanol extract can inhibit insect feeding. Furthermore, the inhibitory effect became more pronounced with increasing n-butanol concentration. At the same treatment time, higher concentrations resulted in higher feeding rejection rates, and the concentration of the n-butanol extract was positively correlated with the feeding rejection rate; higher concentrations of the n-butanol extract demonstrated a stronger ability to inhibit insect feeding.

[0074] 3.2.4 Aqueous Phase Results Table 10 Aquatic phase feeding rejection rate

[0075] Conclusion: From Figure 15 , Figure 16 As shown in Table 10, compared with the control group, the average feeding area of ​​insects in different concentration groups of aqueous solution decreased at 24h, 48h, and 72h, indicating that the aqueous extract can inhibit insect feeding. Furthermore, the higher the concentration, the more significant the inhibitory effect; the feeding area in the high-concentration aqueous solution group was significantly lower than that in the low- and medium-concentration groups at all time points. Under the same treatment time, the higher the concentration, the higher the rejection rate, indicating that the high-concentration extract has a stronger ability to inhibit insect feeding. However, the effect decays rapidly with prolonged treatment time.

[0076] Conclusion Analysis: This study focuses on the plant *Lactuca latae* (of the family Lactucaaceae). Radula complanata (L.) Dumort. Using *Plutella xylostella* as the research subject, this study systematically evaluated the effects of petroleum ether, ethyl acetate, n-butanol, and aqueous extracts on the feeding behavior of *Plutella xylostella* through reflux extraction, multipolar solvent extraction, and leaf-dish insect antifeeding experiments. Plutella xylostella ) and beet armyworm ( Spodoptera litura The main conclusions regarding the antifeeding activity of [the substance] are as follows: Extracts of different polarities from *Platycodon grandiflorus* showed significant antifeedant effects on two lepidopteran pests, with a more pronounced inhibitory effect on the diamondback moth. Overall, the diamondback moth showed higher sensitivity to the extracts, which may be related to differences in the pest's feeding habits or metabolic mechanisms.

[0077] The rejection rate of each phase extract increased significantly with increasing concentration. Although the rejection rate of all treatment groups decreased over time, the high concentration group maintained a high inhibitory effect in the early stage (24–48 h), demonstrating the characteristics of rapid onset and short-term sustained effect.

[0078] This invention confirms the potential of *Platycodon grandiflorus* extract in insect control, providing a new candidate material for the development of plant-derived food repellents. Compared to traditional chemical pesticides, it has advantages such as being environmentally friendly and having low toxicity, meeting the needs of green agricultural development.

[0079] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an extract of *Platycodon grandiflorus* with insect antifeedant activity, characterized in that, The method includes the following steps: The *Platycodon grandiflorus* was extracted several times by reflux with an ethanol solution, and the extracts were combined. The extracts were then rotary evaporated to obtain an extract paste. The extract paste was dissolved and extracted separately using petroleum ether, ethyl acetate, n-butanol, and / or water as extraction solvents. After extraction, extracts of different polar fractions of *Platycodon grandiflorus* were obtained. After concentration, an extract paste was obtained, which is the extract of different polar fractions of *Platycodon grandiflorus* with insect antifeedant activity.

2. The method for preparing the extract of *Platycodon grandiflorus* with insect antifeedant activity as described in claim 1, characterized in that, The separation and extraction method is as follows: the dissolved extract solution is first extracted with petroleum ether to obtain aqueous phase one and petroleum ether phase; then ethyl acetate is added to aqueous phase one for extraction to obtain aqueous phase two and ethyl acetate phase; finally, n-butanol is added to aqueous phase two for extraction to obtain aqueous phase three and n-butanol phase. The obtained petroleum ether phase, ethyl acetate phase, n-butanol phase and aqueous phase three are evaporated separately to obtain petroleum ether phase extract, ethyl acetate phase extract, n-butanol phase extract and aqueous phase extract, which are the extracts of *Platycodon grandiflorus* with insect antifeeding activity.

3. The method for preparing the extract of *Platycodon grandiflorus* with insect antifeedant activity as described in claim 2, characterized in that, The volume ratio of the extract solution to petroleum ether is (1~3):

3.

4. The method for preparing the extract of *Platycodon grandiflorus* with insect antifeedant activity as described in claim 1, characterized in that, The extraction solvent is petroleum ether or ethyl acetate.

5. An extract of *Lysimachia foenum-graecum* prepared by any one of claims 1 to 4.

6. The use of the extract of *Platycodon grandiflorus* according to claim 5 in the preparation of an insect repellent.

7. The application as described in claim 6, characterized in that, The pest repellent has insect antifeeding activity.

8. The application as described in claim 6, characterized in that, The pest repellent is repelled by diamondback moth larvae and / or beet armyworm larvae.

9. An insect repellent, characterized in that it is... The insect repellent was prepared by dissolving the extract of *Lysimachia foenum-graecum* as described in claim 5 in methanol to a concentration of 1-1000 μg / mL.

10. The pest repellent as described in claim 9, characterized in that, The concentration is 100~500μg / mL.

Images