A natural product against potato scab and its preparation method and application

Abstract

The application discloses an anti-potato scab natural product and a preparation method and application thereof. The natural product chain is any one of compounds of Streptomyces sp. FXJ1.172, and a structural formula is shown in the following. The application carries out fermentation on Streptomyces sp. FXJ1.172, and separates the fermentation product to obtain the above-mentioned Streptomyces sp. FXJ1.172. The inventors find that the compounds have good inhibiting effect on Streptomyces sp. pathogenic strains causing potato scab, and further plant pot experiments show that the compounds can effectively prevent and control the occurrence of potato scab and reduce the disease degree.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of medicine, and particularly relates to a natural product for resisting potato scab and a preparation method and application thereof. BACKGROUND

[0002] Potato is the second most important food security crop after rice and wheat in the world. However, its production is threatened by a variety of plant pathogens. Among them, potato common scab (PCS) is a soil-borne and seed-borne disease caused by Streptomyces scabies and related plant pathogenic Streptomyces. PCS forms necrotic lesions on potato tubers, greatly reducing the market value of potato crops, thus leading to disastrous economic losses. Although people have been working on the control of PCS for decades, this disease is still largely difficult to control, and global potato growers urgently need new pesticides or biological control agents to solve this stubborn problem.

[0003] Actinomycetes are a class of gram-positive bacteria with high G+C content (69-78%), which have a complex morphological development differentiation process and rich secondary metabolite synthesis ability, and are widely distributed in various habitats such as soil, ocean, plants, etc. Streptomyces is a large class of evolutionarily higher phylogenetic lineage of actinomycetes, which has numerous secondary metabolic pathways and is the main source of natural products. The secondary metabolites produced by Streptomyces account for more than one-third of the total number of active natural products of microorganisms and have broad-spectrum activity, such as antibacterial, antifungal, antiparasitic, antitumor, immunosuppressive agents, etc., and are widely used in medicine, agriculture and animal husbandry, etc. SUMMARY

[0004] An object of the present application is to provide a series of natural products streptolateritic acids and a preparation method.

[0005] The natural product streptolateritic acid provided by the present application is any one of streptolateritic acids A-D, and the structural formula is as follows:

[0006]

[0007] R=H: streptolateritic acid A (1) R=OH: streptolateritic acid C (3)

[0008]

[0009] R=H: streptolateritic acid B (2) R=OH: streptolateritic acid D (4)

[0010] The method for preparing the natural product Streptomyces sp. FXJ1.172, comprising the following steps: fermenting Streptomyces sp. FXJ1.172 to obtain a fermentation product; and separating the fermentation product to obtain the Streptomyces sp. FXJ1.172.

[0011] The fermentation conditions can be specifically as follows: 28℃, 220rpm oscillation culture for 10 days.

[0012] The culture medium used in the fermentation is a liquid SSC culture medium, and the raw materials added in the liquid SSC culture medium per liter are as follows: 20g soluble starch, 10g soybean powder, 5g calcium carbonate, and the balance is water; the liquid SSC culture medium further adds carbonyl cyanide 3-chlorophenylhydrazone (CCCP) with a final concentration of 1μg / mL.

[0013] The fermentation can be specifically as follows: transferring 2mL of seed culture into a 500mL triangular flask containing 200mL of liquid SSC culture medium, adding carbonyl cyanide 3-chlorophenylhydrazone (CCCP) to make the final concentration 1μg / mL, and continuing to ferment at 28℃ constant temperature shaker with 220rpm speed for 10 days.

[0014] The seed culture can be specifically an OD 600nm =0.6-0.8 seed culture.

[0015] The preparation method of the seed culture can be specifically as follows: taking 1mL of Streptomyces sp. FXJ1.172 spore suspension (spore concentration about 2.5×10 6 CFU / mL) and inoculating into a 50mL centrifuge tube containing 10mL of liquid TSB culture medium, and activating at 28℃ constant temperature shaker with 220rpm speed for 48h to obtain the seed culture.

[0016] The raw materials added in the liquid TSB culture medium per liter are as follows: 17g of tryptone, 3g of soybean hydrolysate, 2.5g of glucose, 5g of NaCl, 2.5g of K2HPO4, and the balance is water, pH 7.1-7.5.

[0017] Specifically, a method for preparing a natural product Streptomyces sp. FXJ1.172, comprising the following steps:

[0018] 1) fermenting Streptomyces sp. FXJ1.172 to obtain a fermentation product;

[0019] 2) centrifuging the fermentation product to collect mycelium and supernatant respectively; extracting the mycelium with anhydrous ethanol to collect ethanol extract; extracting the supernatant with ethyl acetate to collect ethyl acetate extract;

[0020] 3) concentrating the ethanol extract and the ethyl acetate extract to dryness under reduced pressure respectively, dissolving the combined concentrate in methanol, centrifuging, and taking the supernatant;

[0021] 4) separating the supernatant by high performance liquid chromatography to obtain the chain red soil acids A-D.

[0022] In step 2) of the above method, the ratio of the mycelium to anhydrous ethanol is 20 g:200 mL, and the anhydrous ethanol is extracted overnight; the supernatant is extracted with an equal volume of ethyl acetate, and the ethyl acetate extraction is performed for 3 hours.

[0023] In step 3) of the above method, the ratio of the combined concentrate to methanol is 0.5 g:2 mL.

[0024] In step 4) of the above method, the chromatographic conditions of the high performance liquid chromatography are as follows:

[0025] The chromatographic column is a Waters Xbridge octyl decyl silane column with a specification of 4.6x150 mm, 5 μm;

[0026] The flow rate is 1.0 ml / min;

[0027] A binary solvent system using water as phase A and methanol as phase B is used for linear gradient elution;

[0028] The gradient elution conditions are as follows:

[0029]

[0030] The detector is a diode array detector, and the monitoring absorption wavelength is selected between 190 and 800 nm.

[0031] Chain red soil acid A (retention time=16.2 min), chain red soil acid B (retention time=16.3 min), chain red soil acid C (retention time=14.2 min), and chain red soil acid D (retention time=14.3 min) are obtained. The corresponding compounds are prepared by collecting the eluate, drying, and preparing at the above retention times.

[0032] Specifically, another method for preparing the natural product chain red soil acids A-D includes the following steps:

[0033] a) fermenting Streptomyces sp. FXJ1.172 to obtain a fermentation product;

[0034] b) centrifuging the fermentation product to collect mycelium; extracting the mycelium with anhydrous ethanol to collect ethanol extract;

[0035] c) concentrating and drying the ethanol extract to obtain a crude extract, and subjecting the crude extract to gradient elution on a silica gel column (100-200 mesh) using CHCl3:CH3OH (volume ratio from 95:5 to 70:30) as mobile phase, and collecting all elution fractions;

[0036] d) purifying the elution fractions on a Sephadex LH-20 gel column and subjecting them to isocratic elution with methanol, and collecting methanol elution fractions;

[0037] e) separating the methanol elution fractions by reverse phase high performance liquid chromatography to obtain the above-mentioned chainzhi acid A-D.

[0038] In the step b) of the above method, the ratio of mycelium to anhydrous ethanol is 1000g:10L, and the extraction time can be 12 hours.

[0039] In the step e) of the above method, the chromatographic conditions of high performance liquid chromatography are as follows:

[0040] The chromatographic column is Supelco Ascentis C18 column with a size of 100x21.1mm and a particle size of 5μm;

[0041] The mobile phase is acetonitrile / water (37:63, v / v) with a flow rate of 2.0mL / min;

[0042] The detector is diode array detector;

[0043] The detection wavelength is 220nm;

[0044] The HPLC retention time of the final product is: chainzhi acid A retention time=9.2min, chainzhi acid B retention time=11.1min, chainzhi acid C retention time=6.0min, and chainzhi acid D retention time=7.4min.

[0045] Another object of the present application is to provide the use of the above-mentioned chainzhi acid A-D.

[0046] The use provided by the present application is the use of the above-mentioned chainzhi acid A-D in the preparation of antibacterial drugs or in the prevention and treatment of potato scab.

[0047] Further, the antibacterial drug can inhibit Streptomyces pathogenic bacteria causing potato scab. Further, the potato scab is caused by Streptomyces pathogenic bacteria. The Streptomyces pathogenic bacteria are specifically Streptomyces scabiei CGMCC 4.1765, Streptomyces fimicarius CGMCC 4.1836, and Streptomyces luridiscabiei CGMCC 4.3490.

[0048] It is another object of the present application to provide an antibacterial drug.

[0049] The antibacterial drug provided by the present application comprises at least one compound of Streptolateritic acids A-D.

[0050] Further, the antibacterial drug can inhibit Streptomyces pathogenic bacteria causing potato scab.

[0051] The present application also provides a method for preventing and treating potato scab.

[0052] The method for preventing and treating potato scab provided by the present application comprises applying an effective amount of at least one compound of Streptolateritic acids A-D to potato crops, seeds of potato crops, soil, or a cultivation carrier.

[0053] The Streptomyces sp. FXJ1.172 used in the present application is a strain of Streptomyces isolated from a red soil sample in Jiangxi Province by the inventors, and has good biological activity. The inventors have isolated a series of natural products, Streptolateritic acids A-D, from the strain by optimizing fermentation conditions, and found that the compounds have good inhibitory effect on Streptomyces pathogenic bacteria causing potato scab. Further, plant pot experiments show that the compounds can effectively prevent and treat potato scab and reduce the degree of disease. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 Figure 1 is a growth morphology diagram of Streptomyces sp. FXJ1.172;

[0055] Figure 2 Figure 5 is a high-performance liquid chromatogram of Streptolateritic acids A-D;

[0056] Figure 3 Figure 6 is a high-resolution mass spectrum of Streptolateritic acids A-D;

[0057] Figure 4 Figure 7 is a1H-NMR spectrum of Streptolateritic acid A; 11H NMR spectrum (500MHz, solvent: CD3OD);

[0058] Figure 5 For alkaline acid A 13 C10 NMR spectrum (125 MHz, solvent: CD3OD);

[0059] Figure 6 The Dept135 NMR spectrum of aldocarboxylic acid A (500MHz, solvent: CD3OD);

[0060] Figure 7 The COSY spectrum of aldocarboxylic acid A is shown (500 MHz, solvent: CD3OD).

[0061] Figure 8 The HSQC spectrum of aldocarboxylic acid A is shown (500 MHz, solvent: CD3OD).

[0062] Figure 9 The HMBC spectrum of aldocarboxylic acid A (500MHz, solvent: CD3OD);

[0063] Figure 10 The NOESY spectrum of aldocarboxylic acid A (500MHz, solvent: CD3OD);

[0064] Figure 11 For alkaline B 1 1H NMR spectrum (500MHz, solvent: CD3OD);

[0065] Figure 12 For alkaline B 13 C10 NMR spectrum (125 MHz, solvent: CD3OD);

[0066] Figure 13 For alkaline acid C 1 1H NMR spectrum (500MHz, solvent: CD3OD);

[0067] Figure 14 For alkaline acid C 13 C10 NMR spectrum (125 MHz, solvent: CD3OD);

[0068] Figure 15 For alkaline D 1 1H NMR spectrum (500MHz, solvent: CD3OD);

[0069] Figure 16 For alkaline D 13 C10 NMR spectrum (125 MHz, solvent: CD3OD);

[0070] Figure 17 Figures of inhibition zone effect of Streptomyces sp. A-D against three strains of potato scab pathogen Streptomyces scabiei and Streptomyces sp. FXJ1.172;

[0071] Figure 18 Inhibition of common scab of potato by Streptomyces sp. A and C in laboratory greenhouse; (A) negative control (sterile water), showing no common scab symptoms at all; (B) positive control (S. scabiei CGMCC 4.1765 T ), showing common scab symptoms; (C-D) after 6 hours (attachment phase) and 14 days (infection phase) of inoculation with S. scabiei 4.1765 T , Streptomyces sp. A (4 μg mL –1 ) was added; (E-F) after 6 hours (attachment phase) and 14 days (infection phase) of inoculation with S. scabiei 4.1765 T seeded, Streptomyces sp. C (16 μg mL –1 ) was added. DETAILED DESCRIPTION

[0072] The present application is further described in conjunction with the following examples, which in no way are intended to limit the scope of the application. The methods described are routine methods unless otherwise specified. The raw materials described are publicly available from commercial sources unless otherwise specified.

[0073] The Streptomyces sp. FXJ1.172 used in the following examples is the Streptomyces sp. FXJ1.172 described in the following document: Liu M, Liu N, Shang F, Huang Y: Activation and identification of NC-1, a cryptic cyclodepsipeptide from red soil-derived Streptomyces sp. FXJ1.172. Eur J Org Chem, 2016, Jun 19; 2016(23): 3943-3948. which is publicly available from the applicant and can only be used for repeating the experiments of the present application.

[0074] The strain growth morphology of the Streptomyces sp. FXJ1.172 is shown in Figure 1 .

[0075] Example 1, Fermentation method of Streptomyces sp. A (small scale fermentation and metabolite analysis)

[0076] An appropriate amount (1 mL) of Streptomyces sp. FXJ1.172 spore suspension (spore concentration about 2.5 x 10 6 CFU / mL) was inoculated into a 50 mL centrifuge tube containing 10 mL liquid TSB medium (containing 1.7% tryptone, 0.3% soybean hydrolysate, 0.25% glucose, 0.5% NaCl, 0.25% K2HPO4, pH 7.1-7.5) and activated at 28°C on a constant temperature shaker at 220 rpm for 48 h as a seed culture (OD 600nm CFU / mL) was inoculated into a 50 mL centrifuge tube containing 10 mL liquid TSB medium (containing 1.7% tryptone, 0.3% soybean hydrolysate, 0.25% glucose, 0.5% NaCl, 0.25% K2HPO4, pH 7.1-7.5) and activated at 28°C on a constant temperature shaker at 220 rpm for 48 h as a seed culture (OD

[0077] HPLC detection:

[0078] Injection volume: 20 μl

[0079] Detection wavelength: Chain red soil acid (254 nm).

[0080] HPLC analysis was performed on a Shimadzu Prominence HPLC system using a Waters Xbridge octyl decyl silane column (4.6 x 150 mm, 5 μm). The injection volume of the sample was 20 μL. A binary solvent system using water as phase A and methanol as phase B was used for gradient elution.

[0081] Mobile phase: A: methanol; B: water; flow rate: 1.0 ml / min;

[0082] Elution condition: linear gradient elution

[0083]

[0084] The monitoring absorption wavelength between 190 and 800 nm was screened by a diode array detector to obtain chainzhusuanacid A (retention time = 16.2 min), chainzhusuanacid B (retention time = 16.3 min), chainzhusuanacid C (retention time = 14.2 min) and chainzhusuanacid D (retention time = 14.3 min), and their chromatograms are shown in Fig. 1. The above compounds were prepared by collecting the eluent at the above retention time and drying. Figure 2

[0085] Example 2, Fermentation preparation method of chainzhusuanacid (mass fermentation and separation and purification)

[0086] The seed culture of Streptomyces sp. FXJ1.172 (same as Example 1) was cultured in SSC liquid medium (500 mL conical flask 50 x 200 mL, total 10 L) with the addition of CCCP (final concentration 1 μg / mL) at 28°C, 220 rpm for 10 days. After the fermentation was completed, the mycelium was harvested by centrifugation at 5000 rpm for 15 min, and extracted with 10 L of ethanol under stirring for 12 h at room temperature. The organic extract was filtered using a Buchner funnel and dried using a rotary evaporator to obtain 100 g of crude extract. 100 g of silica gel powder (Qingdao Marine Chemicals, specification 100-200 mesh, product code CXGJF-03-N3) was added and stirred uniformly, and then packed into a silica gel column and gradient eluted using CHCl3:CH3OH (volume ratio from 95:5 to 70:30) as the mobile phase. All the eluted fractions were collected, combined and concentrated to 10 mL, and then added to a Sephadex LH-20 gel column and repeatedly eluted through the Sephadex LH-20 column using CH3OH to remove fatty acids and other lipophilic impurities.

[0087] The final product was analyzed by HPLC using a Supelco Ascentis C18 column (100 x 21.1 mm, 5 μm) connected to a Shimadzu SPD-M20A instrument, with acetonitrile / water (37:63, v / v) as the mobile phase, a flow rate of 2.0 mL / min, and a PDA detector for detecting the absorbance at 220 nm. The HPLC retention time and the obtained mass of the final product were as follows: chainzhusuanacid A (7.2 mg, retention time = 9.2 min), chainzhusuanacid B (1.8 mg, retention time = 11.1 min), chainzhusuanacid C (7.4 mg, retention time = 6.0 min), and chainzhusuanacid D (1.8 mg, retention time = 7.4 min).

[0088] Chainzhusuanacid A (1): colorless solid; [α] 25 D +39.69 (c = 0.010, CH3OH); UV / vis (CH3OH) λ max ​(log e) 208 (2.81) nm; IR (neat) vmax 3288, 2964, 2926, 2869, 1702, 1649, 1418, 1388, 1287, 1249, 1023, 969 cm -1 ; HRESIMS m / z 587.2848 [M-H] - (calcd for C 32 H 44 O 10 , 587.2856).

[0089] Stemphylium acidum B (2): colorless solid; [a] 25 D +43.33 (c = 0.003, CH3OH); UV / vis (CH3OH) λ max (log e) 206 (2.38) nm; IR (neat) vmax 3284, 2963, 2932, 2867, 1702, 1655, 1442, 1413, 1388, 1283, 1251, 1025, 970 cm -1 ; HRESIMS m / z 587.2849 [M-H] - (calcd for C 32 H 44 O 10 , 587.2856).

[0090] Stemphylium acidum C (3): colorless solid; [a] 25 D +23.36 (c = 0.013, CH3OH); UV / vis (CH3OH) λ max (log e) 207 (2.80) nm; IR (neat) vmax 3288, 2980, 2959, 2865, 1708, 1651, 1436, 1386, 1226, 1025, 973 cm -1 ; HRESIMS m / z 603.2820 [M-H] - (calcd for C 32 H 44 O 11 , 603.2806).

[0091] Stemphylium acidum D (4): colorless solid; [a] 25 D +32.22 (c = 0.003, CH3OH); UV / vis (CH3OH) λ max(log e) 206 (2.63) nm; IR (neat) v max 3285, 2975, 2867, 1703, 1652, 1583, 1439, 1414, 1286, 1224, 1026, 970 cm -1 ; HRESIMS m / z 603.2811 [M-H] - (calcd for C 32 H 44 O 11 , 603.2806).

[0092] The high resolution mass spectra of streptolateritic acids A-D are shown in Figure 3 ;

[0093] The structure identification spectra of streptolateritic acid A are shown in Figures 4-10 ;

[0094] The structure identification spectra of streptolateritic acid B are shown in Figures 11-12 ;

[0095] The structure identification spectra of streptolateritic acid C are shown in Figures 13-14 ;

[0096] The structure identification spectra of streptolateritic acid D are shown in Figures 15-16 .

[0097] Example 3: Determination of antibacterial activity of streptolateritic acids A-D

[0098] The MIC (Minimal inhibitory concentration) of aerobic actinomycetes was determined by using the modified micro-broth dilution method. The lyophilized powder of streptolateritic acids A-D was initially dissolved in DMSO, and then diluted with sterile water to a 2% DMSO solution for testing. In the CAMHB medium (Beijing Coolab Science and Technology Co., Ltd., item number MM3031), 50 μL of pathogenic Streptomyces culture containing 0.5 x 10 6 CFU / mL was added, and an equal volume of compound solution was added, and incubated at 28°C for 48 h. The antibacterial drug sensitivity was determined by using the double dilution method, with the compound concentration ranging from 0.125 μg / mL to 128 μg / mL. The MIC value was obtained by turbidity analysis. All experiments were biologically repeated three times, and the median was taken as the value of MIC. Ampicillin, ciprofloxacin, chloramphenicol, piperacillin, rifampicin, tetracycline and vancomycin were used as positive controls.

[0099] The strains evaluated in this example include: Streptomyces scabiei CGMCC 4.1765 TStreptomyces fimicarius CGMCC 4.1836, Streptomyces luridiscabiei CGMCC 4.3490, both purchased from China General Microbiological Culture Collection Center. The evaluation results are shown in Table 1.

[0100] Table 1 Minimum inhibitory concentrations of chain red soil acids A-D and some antibiotics on three strains of potato scab pathogenic Streptomyces

[0101]

[0102]

[0103] According to the antibacterial activity evaluation, compared with the control group of antibiotics, chain red soil acids A-D showed similar or better inhibitory activity compared with the control antibiotics. Among them, the inhibitory ability of A / B without hydroxylation at position C23 was stronger than that of C / D with hydroxylation.

[0104] From the inhibition zone results of Figure 1 , it can be seen that chain red soil acids A-D have good inhibitory effect on the growth of the above three strains of potato scab pathogenic bacteria (CGMCC 4.1765, CGMCC 4.1836, CGMCC 4.3490), and have no obvious inhibitory effect on the producing bacteria itself (FXJ1.172).

[0105] Example 3: Test the inhibitory effect of chain red soil acid A or C on potato scab at the plant level by potato pot experiment

[0106] Potato pot experiment was used to detect the prevention and control of potato laboratory pot scab. The experiment was carried out in a greenhouse. 10 mL of S. scabiei CGMCC 4.1765 T bacterial suspension (concentration 10 9 CFU / mL) was injected into the root of potato virus-free seedling to ensure that potato was infected with scab. 6h (attachment period) and 14d (infection period) after inoculation of S. scabiei in the experimental group, 10 mL of chain red soil acid A (concentration 4 μg / mL) or chain red soil acid C (concentration 16 μg / mL) was injected into the root of each seedling, and the same amount of sterile water was added as control. According to the growth of the plants, the same amount of water was supplemented in time. The day and night temperature was 23℃ / 18℃, the relative humidity was 70%, and the light intensity was 1000 lux. After cultivation to the potato setting period (about 90d), the tubers with diameter length more than 3 cm were washed clean under tap water, and the percentage of tuber area covered by scab was scored according to the scab disease grading standard. The disease index and incidence rate of the experimental group and the control group were calculated, and the control effect was calculated.

[0107] Disease index was calculated according to the following formula:

[0108] Disease index = [∑(n x 1 + n x 2 + n x 3 + n x 4 + n x 5) / (N x 5)] x 100. (n = number of tubers corresponding to the numerical grade. N = total number of potato tubers assessed).

[0109] 1-5 score table refers to the percentage of the area of scab disease infection:

[0110] 0: no scab disease symptoms; 1: 0-12.5% of the area is infected; 2: 12.6-25% of the area is infected; 3: 26-50% of the area is infected; 4: 51-75% of the area is infected; 5: 76-100% of the area is infected.

[0111] Control effect = (disease index of the control group - disease index of the treatment group) / disease index of the control group x 100%.

[0112] The results of the evaluation of the control effect of chain red soil acid on potato scab are shown in Table 2.

[0113] Table 2 Control effect of chain red soil acid on potato scab

[0114]

[0115] Note: 4.1765 is a pathogenic strain of potato scab. The compounds chain red soil acid A or C were added 6 hours or 14 days after the virus-free potato seedlings were inoculated with scab bacteria, and the potatoes were harvested after 90 days to evaluate the control effect.

[0116] The inhibitory effect of chain red soil acid A and C on common potato scab in a laboratory greenhouse is shown in Figure 18 As can be seen from the figure, both chain red soil acid A and chain red soil acid C can effectively inhibit potato scab. It is shown that the chain red soil acid provided by the present application can effectively prevent and control the occurrence of potato scab and reduce the disease at the plant level.

Claims

1. The natural product alkaline acid, which is any compound of alkaline acid AD, has the following structural formula: 。 2. The method for preparing aldocarboxylic acid AD according to claim 1 comprises the following steps: fermenting Streptomyces FXJ1.172 to obtain a fermentation product; separating the fermentation product to obtain aldocarboxylic acid AD.

3. The method for preparing aldocarboxylic acid (AD) according to claim 2, characterized in that: The specific fermentation conditions are: 28℃, 220rpm shaking culture for 10 days; Alternatively, the fermentation medium used is liquid SSC medium, and the raw materials added to each liter of liquid SSC medium are as follows: 20g soluble starch, 10g soybean flour, 5g calcium carbonate, and the remainder is water; the liquid SSC medium also contains carbonyl cyanide 3-chlorophenylhydrazine, so that its final concentration is 1μg / mL.

4. The method for preparing aldocarboxylic acid (AD) according to claim 2 or 3, characterized in that: The preparation method specifically includes the following steps: 1) Fermenting Streptomyces FXJ1.172 yielded the fermentation product; 2) Centrifuge the fermentation product and collect the mycelium and supernatant separately; extract the mycelium with anhydrous ethanol and collect the ethanol extract; The supernatant was extracted with ethyl acetate, and the ethyl acetate extract was collected. 3) Concentrate the ethanol extract and the ethyl acetate extract to dryness under reduced pressure, combine the concentrates, dissolve them in methanol, centrifuge, and collect the supernatant. 4) The supernatant was separated by high performance liquid chromatography to obtain the alkaline acid AD.

5. The method for preparing aldocarboxylic acid (AD) according to claim 4, characterized in that: In step 2), the ratio of mycelium to anhydrous ethanol is 20g:200mL, and the extraction is performed overnight with anhydrous ethanol; the supernatant is extracted with an equal volume of ethyl acetate for 3 hours. Alternatively, in step 3), the ratio of the combined concentrate to methanol is 0.5g:2mL; Alternatively, in step 4), the chromatographic conditions for high-performance liquid chromatography are: The chromatographic column was a Waters Xbridge C18 column, 4.6 × 150 mm, 5 μm; Flow rate: 1.0 ml / min; Linear gradient elution was performed using a binary solvent system with water as phase A and methanol as phase B. The gradient elution conditions are as follows: from 0 to 15 min, the volume percentage of phase A decreases from 80% to 0%; from 15 min to 20.5 min, the volume percentage of phase A remains at 0%; from 20.5 min to 20.51 min, the volume percentage of phase A increases from 0% to 80%; from 20.51 min to 26.51 min, the volume percentage of phase A remains at 80%, and the water in phase A is ddH2O. Detector: Diode array detector, screening for absorption wavelengths between 190 nm and 800 nm; The eluent with a retention time of 16.2 min was collected, concentrated, and dried to obtain the alkaline acid A. The eluent with a retention time of 16.3 min was collected, concentrated, and dried to obtain the chain red oxalic acid B; The eluent with a retention time of 14.2 min was collected, concentrated, and dried to obtain the alkaline acid C. The eluent with a retention time of 14.3 min was collected, concentrated, and dried to obtain the chain red oxalic acid D.

6. The method for preparing aldocarboxylic acid (AD) according to claim 2 or 3, characterized in that: The preparation method specifically includes the following steps: a) Fermenting Streptomyces FXJ1.172 to obtain fermentation product; b) Centrifuge the fermentation product and collect the mycelium; extract the mycelium with anhydrous ethanol and collect the ethanol extract; c) The ethanol extract is concentrated and dried to obtain a crude extract. The crude extract is then subjected to gradient elution on a silica gel column with a 100-200 mesh using a mobile phase with a CHCl3:CH3OH volume ratio ranging from 95:5 to 70:30, and all eluted fractions are collected. d) The eluent was purified using a Sephadex LH-20 gel column, eluted isocratically with methanol, and the methanol eluent was collected. e) The methanol elution fraction is separated by reversed-phase high-performance liquid chromatography to obtain the alkyne AD.

7. The method for preparing aldocarboxylic acid (AD) according to claim 6, characterized in that: In step b) of the method, the ratio of mycelium to anhydrous ethanol is 1000g:10L, and the extraction time is 12 hours. Alternatively, in step e) of the method, the chromatographic conditions for high-performance liquid chromatography are: The chromatographic column was a Supelco Ascentis C18 column, with dimensions of 100 × 21.1 mm and a diameter of 5 µm; Mobile phase: acetonitrile / water, volume ratio 37:63; flow rate: 2.0 mL / min; Detector: Diode array detector; Detection wavelength: 220 nm; HPLC retention times of the final products: Retention time of alkyne A = 9.2 min, retention time of alkyne B = 11.1 min, retention time of alkyne C = 6.0 min, retention time of alkyne D = 7.4 min.

8. The use of any compound of the alkyne AD according to claim 1 in the preparation of antibacterial drugs or in the prevention and treatment of potato scab disease.

9. The application according to claim 8, characterized in that: The antimicrobial drug can inhibit Streptomyces pathogens that cause potato scabies; or, the potato scabies is caused by Streptomyces pathogens.

10. An antibacterial agent comprising at least one compound of the aldocarboxylic acid AD as described in claim 1.

11. The antibacterial drug according to claim 10, characterized in that: The antibacterial drug can inhibit the pathogenic bacteria Streptomyces that cause potato scab disease.

12. A method for controlling potato scab disease, comprising applying an effective amount of at least one compound of the red oxalic acid AD as described in claim 1 to potato crops, potato seeds, soil or cultivation carrier.

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