Antifungal isoquinoline derivative

Abstract

The invention belongs to the technical field of pesticides and plant disease control, and provides an antifungal isoquinoline derivative which can inhibit various fungal diseases on rice, tobacco and white lotus. The derivative can also be compounded with difenoconazole or pyraclostrobin to prevent and treat fungal diseases of rice and tobacco, and has a good development prospect.

Description

Technical Field

[0001] This invention belongs to the field of pesticide and plant disease control technology, and relates to the application of an isoquinoline derivative in the control of plant pathogens. Background Technology

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

[0003] Rice is one of the world's major food crops, serving as the staple food for nearly 3 billion people globally. Therefore, stabilizing rice quality and yield plays a crucial role in ensuring food security. Tobacco has a wide range of uses, serving as both an industrial raw material and a medicinal ingredient. Both rice and tobacco are threatened by various pathogens during their growth period, such as rice blast, rice sheath blight, tobacco target spot, and tobacco red spot. These fungal diseases severely impact crop quality and yield. Therefore, controlling different diseases during the growth and development of crops like rice and tobacco has become a key focus of modern agricultural research.

[0004] Currently, chemical control remains the primary method of disease control, playing a crucial role in curbing disease spread and contributing to steady crop yield increases. However, it is undeniable that pesticide use has been steadily increasing in recent years, both in quantity and intensity. Simultaneously, improper use is frequent, leading not only to the development of pesticide resistance in pathogens but also to further impacting the environment and human health due to excessive use, posing serious challenges to the agricultural ecological environment and the quality and safety of agricultural products. Therefore, developing novel, highly efficient, and environmentally friendly lead compounds is of paramount importance for the control of plant fungal diseases.

[0005] Isoquinolines and their derivatives are an important class of nitrogen-containing heterocyclic compounds, widely found in the structures of naturally derived alkaloids. Examples include papaverine, extracted from poppy plants, which has antispasmodic effects; berberine, an antibacterial component isolated from plants such as Coptis chinensis; and corydaline, a sedative and analgesic component derived from Corydalis yanhusuo. Therefore, isoquinolines and their derivatives, due to their wide distribution in nature, complex and diverse structures, and broad physiological activities, have great development and utilization value in chemistry and biopharmaceuticals. They not only possess broad medicinal activities but also have some reported applications in agriculture. For example, sanguinarine extracted and isolated from the plant *Chloranthus chinensis* and chelidonine isolated from the plant *Cephalotaxus fortunei* have activity against *Dactylogyrus*. However, current research on the control of plant fungal diseases using these compounds is relatively limited, and there is still considerable room for expansion. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides the application of isoquinoline derivatives in the prevention and control of plant pathogens, which can inhibit the occurrence and development of various fungal diseases on rice, tobacco and white lotus.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] Application of an isoquinoline derivative in the control of plant pathogens, wherein the structural formula of the isoquinoline derivative is: It is abbreviated as Ntic3.

[0009] The plant pathogen was selected from *Cucurbita cylindrica* (a type of fungus). Cucumber beetle Alternaria alternata ( ) Alternaria alternata Rhizoctonia solani ( ) Rhizoctonia solani Rice blast fungus ( Magnaporthe rice ) and Fusarium oxysporum ( Fusarium oxysporum ).

[0010] The preferred Fusarium oxysporum species is the lotus-specific Fusarium oxysporum.

[0011] A pesticide composition comprising the above-mentioned isoquinoline derivative as its active ingredient.

[0012] The above-mentioned pesticide composition also includes other pesticide active ingredients and / or inert excipients.

[0013] The active ingredient of the pesticide is preferably a fungicide. More preferably, the active ingredient is difenoconazole or pyraclostrobin.

[0014] In the above pesticide composition, the mass ratio of isoquinoline derivative to difenoconazole is 1:9-9:1. The mass ratio of isoquinoline derivative to pyraclostrobin is 1:9-9:1.

[0015] Preferably, in the above pesticide composition, the mass ratio of isoquinoline derivative to difenoconazole is 1:9 or 7:3. The mass ratio of isoquinoline derivative to pyraclostrobin is 1:9.

[0016] The target pest of the above pesticide composition is *Trichophyton mentagrophytes* (Cucurbita spp.). Cucumber beetle Alternaria alternata ( ) Alternaria alternata Rhizoctonia solani ( ) Rhizoctonia solani Rice blast fungus ( Magnaporthe rice ) and Fusarium oxysporum ( Fusarium oxysporum ).

[0017] The diseases controlled by the above pesticide composition are tobacco target spot, tobacco red spot, rice sheath blight, rice blast, and white lotus rot.

[0018] The present invention has the following advantages: The antifungal isoquinoline derivative Ntic3 provided by this invention can inhibit various fungal diseases occurring on rice, tobacco, and lotus. This derivative can also be combined with difenoconazole or pyraclostrobin to control fungal diseases in rice and tobacco, showing promising development prospects. Attached Figure Description

[0019] Figure 1 It is an isoquinoline derivative Ntic3 1 H NMR. Detailed Implementation

[0020] The present invention will be further described below with reference to the embodiments and accompanying drawings, but the present invention is not limited to the following embodiments.

[0021] Example 1: Indoor effect of isoquinoline derivative Ntic3 on fungal diseases The structural formula of the isoquinoline derivative Ntic3 is as follows: ; Purchased from Shanghai Taoshu Biotechnology Co., Ltd., purity: >99% (HPLC method). 1 H NMR image as follows Figure 1 As shown.

[0022] The pathogen of tobacco target spot disease, *Citrus fulvidraco*, was isolated spontaneously. Cucumber beetle (Frank)Donk), Alternaria alternata, the pathogen of tobacco red spot disease ( Alternaria alternata (Fries) Keisslar), the pathogen of rice sheath blight, Rhizoctonia solani ( Rhizoctonia solani Kühn), rice blast fungus ( Magnaporth rice ) and the pathogen of white lotus rot fungus, Fusarium oxysporum lotus-specific type ( Fusarium oxysporum f. sp. nelumbicola). The mycelial growth rate method was used to determine the indoor toxicity of the isoquinoline derivative Ntic3 against the above five pathogens. The specific procedure is as follows: 1. Preparation of drug-containing culture medium Accurately weigh the isoquinoline derivative Ntic3 and dissolve it in DMSO solution to prepare a stock solution. Then, dilute it to the target concentration with 0.1% Tween-80 aqueous solution. Shake the diluted solution and sterilized PDA medium at a volume ratio of 1:9 (drug solution: medium) to prepare drug-containing plates with a target concentration of 50 μg / mL. Add the same volume of 0.1% Tween-80 to the blank control. Commercially available azoxystrobin (25% suspension) and jinggangmycin (4% aqueous solution) were directly diluted to the target concentration with 0.1% Tween-80 aqueous solution.

[0023] 2. Toxicity testing The pathogen was inoculated onto PDA plates and pre-cultured for 5 days. Mycelial cakes were created at the edge 1 / 3 of the culture medium using a 5 mm diameter punch. These cakes were then transferred to PDA plates containing the drug and those without the drug, and incubated at 28°C for 3 days. Each treatment was repeated three times. When the mycelia in the blank control covered 2 / 3 of the culture medium, the colony diameter was measured using the cross-sectional method, and the average value was calculated. The inhibition rate of the compound on the mycelia was calculated using the following formula: Antibacterial rate (%) = ×100% Table 1. Indoor toxicity of isoquinoline derivative Ntic3 against five pathogenic fungi. Table 1 shows that the isoquinoline derivative Ntic3 exhibits good inhibitory effects against various plant pathogenic fungi, including *Tobacco Target Spot Fungus*, *Tobacco Red Spot Fungus*, *Rice Sheath Blight Fungus*, *Rice Blast Fungus*, and *White Lotus Rot Fungus*, demonstrating broad-spectrum antibacterial activity. At the same concentration (50 μg / mL), the inhibitory activity of isoquinoline derivative Ntic3 against the five pathogenic fungi was significantly higher than that of the commercially available fungicide Jinggangmycin, and comparable to that of the commercially available fungicide Azoxystrobin. In conclusion, the isoquinoline derivative Ntic3 has high application potential and development value in the control of fungal diseases in crops.

[0024] Example 2: Indoor combined toxicity of isoquinoline derivative Ntic3 and difenoconazole against rice sheath blight pathogen. The combined toxicity of the fungicides was determined in vitro using the mycelial growth rate method. *Rhizoctonia solani*, the causal agent of rice sheath blight, was inoculated onto PDA plates and pre-cultured for 5 days. Mycelial cakes were then created at the edges of the colonies using a 5 mm diameter punch, and subsequently transferred to a series of plates containing different concentrations of the fungicide for 3 days. Each treatment was repeated three times. After 3 days, the colony diameter was examined, and the inhibition rate on mycelia was calculated. The EC50 of each fungicide was calculated. 50 Values ​​were used to establish a virulence regression equation and R0. 2 EC 50 With a 95% confidence limit, the combined effect of isoquinoline derivative Ntic3 and difenoconazole under combined treatment was determined by the Wadley method, and the synergy ratio (SR) was calculated. SR < 0.5 was considered antagonistic, SR > 1.5 was considered synergistic, and SR between 0.5 and 1.5 was considered additive.

[0025] Antibacterial rate (%) = ×100%; EC 50 (Theory) = ; SR= ; Where a and b represent the proportions of the two agents in the mixture, respectively.

[0026] Table 2. Combined toxicity of isoquinoline derivative Ntic3 and difenoconazole against rice sheath blight pathogen. Table 2 shows that isoquinoline derivative Ntic3 and difenoconazole have good inhibitory effects on rice sheath blight pathogens, and the inhibitory activity of the combination of the two is higher than that of their individual use. At different mixing ratios, the synergistic coefficients of the two range from 1.2288 to 1.6383, showing varying degrees of synergistic or additive effects; among them, the synergistic coefficient is 1.6383 when the mixing ratio is 1:9, showing a significant synergistic effect. In conclusion, the combination of isoquinoline derivative Ntic3 and difenoconazole can effectively inhibit the proliferation of rice sheath blight pathogens, and to a certain extent, reduce the amount of commercially available pesticides used, thus mitigating the development of resistance when pesticides are used alone.

[0027] Example 3: Indoor combined virulence of isoquinoline derivative Ntic3 and pyraclostrobin against rice blast fungus. The mycelial growth rate method was used. Rice blast fungus was inoculated onto PDA plates and pre-cultured for 5 days. Mycelial cakes were then created at the edges of the colonies using a 5mm diameter punch, and subsequently transferred to a series of plates containing different concentrations of fungicides and incubated for 5 days. Each treatment was repeated three times. After 5 days, the colony diameter was checked, and the inhibition rate on mycelia was calculated. The EC50 of each fungicide was calculated using SPSS software. 50 Values ​​were used to establish a virulence regression equation and R0. 2 EC 50 At a 95% confidence limit, the combined effect of isoquinoline derivative Ntic3 and pyraclostrobin under combined treatment was determined by the Wadley method, and the synergistic coefficient SR was calculated.

[0028] Table 3. Combined toxicity of isoquinoline derivative Ntic3 and pyraclostrobin against rice blast fungus. Table 3 shows that the combined use of isoquinoline derivative Ntic3 and pyraclostrobin exhibits superior inhibitory activity against rice blast fungus compared to either agent alone. At different mixing ratios, the synergistic coefficients ranged from 1.1858 to 1.5579, all demonstrating varying degrees of synergistic effect. The synergistic coefficient was 1.5579 at a mixing ratio of 1:9, showing a significant synergistic effect. These results indicate that the combined use of isoquinoline derivative Ntic3 and pyraclostrobin has considerable application potential in inhibiting rice blast fungus and can effectively suppress its proliferation.

[0029] Example 4: Combined indoor virulence of isoquinoline derivative Ntic3 and difenoconazole against tobacco target spot pathogens. The mycelial growth rate method was used. *Tobacco target spot pathogen* was inoculated onto PDA plates and pre-cultured for 5 days. Mycelial cakes were then created at the edges of the colonies using a 5mm diameter punch, and subsequently transferred to a series of plates containing different concentrations of the fungicide and incubated for 5 days. Each treatment was repeated three times. After 5 days, the colony diameter was checked, and the inhibition rate of mycelium was calculated. The EC50 of each fungicide was calculated using SPSS software. 50 Values ​​were used to establish a virulence regression equation and R0. 2 EC 50 At a 95% confidence limit, the combined effect of isoquinoline derivative Ntic3 and difenoconazole under combined treatment was determined by the Wadley method, and the synergy ratio (SR) was calculated.

[0030] Table 4. Combined virulence of isoquinoline derivative Ntic3 and difenoconazole against *Tobacco Target Spot*. Table 4 shows that the combined use of isoquinoline derivative Ntic3 and difenoconazole exhibits superior inhibitory activity against *Tobacco Target Spot* causal agent compared to either agent alone. At different mixing ratios, the synergistic coefficients ranged from 0.7521 to 1.3509, all demonstrating varying degrees of additive effect. The synergistic effect was most significant at a mixing ratio of 3:7, with a coefficient of 1.3509. These results indicate that the combined use of isoquinoline derivative Ntic3 and difenoconazole has potential application in inhibiting the proliferation of *Tobacco Target Spot* causal agent.

[0031] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. The application of an isoquinoline derivative in the control of plant pathogens, characterized in that, The structural formula of the isoquinoline derivative is: ； The plant pathogen was selected from *Cucurbita cylindrica* (a type of fungus). Thanatephorus cucumeris Alternaria alternata ( ) Alternaria alternate Rhizoctonia solani ( ), Rhizoctonia solani Rhizoctonia solani Rice blast fungus ( Magnaporthe oryzae ) and Fusarium oxysporum ( Fusarium oxysporum ).

2. A pesticide composition, characterized in that, The active ingredients include 。 3. The pesticide composition according to claim 2, characterized in that, It also includes other active pesticide ingredients and / or inert excipients.

4. The pesticide composition according to claim 3, characterized in that, The active ingredient in the pesticide is a fungicide.

5. The pesticide composition according to claim 3, characterized in that, The active ingredient of the pesticide is difenoconazole or pyraclostrobin.

6. The pesticide composition according to claim 5, characterized in that, The mass ratio of isoquinoline derivative to difenoconazole is 1:9-9:1; the mass ratio of isoquinoline derivative to pyraclostrobin is 1:9-9:

1.

7. The pesticide composition according to claim 5, characterized in that, The mass ratio of isoquinoline derivative to difenoconazole is 1:9 or 7:3; the mass ratio of isoquinoline derivative to pyraclostrobin is 1:

9.

8. The pesticide composition according to claim 2, characterized in that, The target pest of the above pesticide composition is *Trichophyton mentagrophytes* (Cucurbita spp.). Thanatephorus cucumeris Alternaria alternata ( ) Alternaria alternate Rhizoctonia solani ( ), Rhizoctonia solani Rhizoctonia solani Rice blast fungus ( Magnaporthe oryzae ) and Fusarium oxysporum ( Fusarium oxysporum ).

9. The pesticide composition according to claim 2, characterized in that, The diseases to be controlled are tobacco target spot, tobacco red spot, rice sheath blight, rice blast, and white lotus rot.

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