Alpinia zerumbet endophytic fungus-derived sesquiterpenoids, and preparation method and application thereof

Abstract

The invention discloses an alpinia zerumbet endophytic fungus source sesquiterpenoids compound, a preparation method and application. According to the invention, 7-butyl-4-methyloxoxepin-2 (5H)-one with antibacterial activity is separated from a liquid fermentation culture of alpinia zerumbet endophytic fungus Xylaria curta YSJ-5, and the 7-butyl-4-methyloxoxepin-2 (5H)-one is shown as a formula (I) in the specification. The 7-Butyl-4-methyloxexin-2 (5H)-one is a novel sesquiterpenoid compound, and shows good antibacterial activity to MRSA (Methicillin-Resistant Staphylococcus Aureus) and SA (Saline Albumin), and the MIC (Minimum Inhibitory Concentration) value of the 7-Butyl-4-methyloxexin-2 (5H)-one is 6.3 mu g / The invention provides a candidate drug for research and development of novel antibacterial drugs, and provides a scientific basis for development and utilization of alpinia zerumbet endophytic fungus resources. # imgabs0 #

Description

Technical Field

[0001] The invention belongs to the field of pharmaceutical biotechnology, and specifically relates to a sesquiterpenoid compound derived from an endophytic fungus of Alpinia galanga, a preparation method and an application thereof. Background Art

[0002] In the clinical field, infections caused by microorganisms such as bacteria and fungi have high morbidity and mortality, and these infections pose a severe challenge to human drug resistance. Since its first discovery in 1960, Staphylococcus aureus and methicillin-resistant Staphylococcus aureus have become common pathogens causing potentially fatal diseases in medical institutions and community settings (Rajput et al., 2021; Huang et al., 2024; Lawal et al., 2022; Azzam et al., 2023). These infectious diseases include severe soft tissue and bone infections, endocarditis, and pneumonia, which are key factors leading to high morbidity and mortality (Turner et al., 2019; Xiao et al., 2022). MRSA infections cause tens of thousands of deaths each year, bringing huge economic burdens to patients and putting great pressure on global medical resources.

[0003] Currently, the World Health Organization has listed MRSA infection as one of the major clinical challenges in the world (Cascioferro et al., 2021). The drugs used to treat MRSA infection are very limited, among which vancomycin is considered the drug of choice (Wu et al., 2021). However, the abuse of vancomycin has led to the emergence of drug-resistant strains. Vancomycin has strong toxic side effects, which limits its clinical application (Tsutsuura et al., 2021). Therefore, the global medical field urgently needs to find and develop new antibiotic drugs to meet the ongoing public health challenges (Schillaci et al., 2017).

[0004] Endophytic fungi are rich and diverse. They are located in a special environment inside plants and can produce secondary metabolites of various structures. The structural types of their compounds far exceed the range of their plant metabolites. It is easy to discover compounds with novel structures and they have multiple biological activities. Therefore, endophytic fungi have become an important resource for discovering new natural active substances and have important application potential in agriculture and pharmaceutical industries.

[0005] Alpinia zerumbet is a plant of the genus Alpinia in the Zingiberaceae family. It is known for its versatility and high value. It is not only an ornamental plant to add beauty to gardens and interiors, but also has important medicinal value. Furthermore, Alpinia zerumbet has attracted much attention for its significant pharmacological effects in antibacterial (Victório et al., 2009), insecticidal (Kerdudo et al., 2017), mite removal (Bressanin et al., 2021), antioxidant (Kuraya et al., 2017), vasodilation (Rocha et al., 2023), blood pressure reduction (Lahlou et al., 2003) and inhibition of cancer cell proliferation (Liao Liangkun et al., 2022). Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and to provide a new compound 7-butyl-4-methoxyoxepin-2(5H)-one with antibacterial activity discovered from an endophytic fungus of Zingiber officinale and a preparation method and application thereof.

[0007] The first object of the present invention is to provide a compound represented by formula (I) 7-butyl-4-methoxyoxepin-2(5H)-one,

[0008]

[0009] The second object of the present invention is to provide a method for preparing the compound 7-butyl-4-methoxyoxepin-2(5H)-one, which is separated and prepared from the fermentation culture of the endophytic fungus Xylaria curta YSJ-5.

[0010] Preferably, the preparation method comprises the following steps:

[0011] a. Preparation of solid fermentation culture of endophytic fungus Xylaria curta YSJ-5 of Ginger, the solid fermentation product was extracted with ethyl acetate, and the extract was concentrated to obtain an extract;

[0012] b. The crude extract (30.3 g) was treated by reverse phase silica gel column chromatography, using methanol: water (30:70→100:0, v / v) and methanol: acetone (10:1→1:1, v / v) as the elution system for gradient elution. In this process, five components were separated: AY-1 (4.3 g), BY-2 (5.8 g), CY-3 (3.0 g), DY-4 (8.4 g) and EY-5 (8.6 g).

[0013] Component DY-4 (8.4 g) was chromatographed on a normal phase column using a gradient elution system of dichloromethane: methanol (100:1→1:1, v / v) to obtain six subcomponents: DY-4-1 (0.1 g), DY-4-2 (1.1 g), DY-4-3 (1.2 g), DY-4-4 (1.0 g), DY-4-5 (1.0 g), and DY-4-6 (1.2 g). First, DY-4-1 was chromatographed on a Sephadex LH-20 gel column using dichloromethane: methanol (1:3, v / v) as the elution system to separate two subcomponents, DY-4-1-1 (0.07 g) and DY-4-1-2 (0.03 g). TLC thin layer chromatography was developed with n-hexane: ethyl acetate = 2:1 (v / v) to obtain component DY-4-1-1 with Rf = 0.5-0.6. After normal phase column chromatography, petroleum ether: ethyl acetate (5:1→2:1, v / v) gradient elution was used, and then further purified by reverse phase semi-preparative HPLC. The elution conditions were (MeCN / H 2 O, 50:50, v / v, 2 mL / min), 7-butyl-4-methoxyoxepin-2(5H)-one (3.0 mg) was separated therefrom, and TLC thin layer chromatography was developed with n-hexane:ethyl acetate=2:1 (v / v), Rf=0.4-0.5.

[0014] Preferably, the component DY-4-1-1 is further subjected to semi-preparative HPLC to obtain the compound 7-butyl-4-methoxyoxepin-2(5H)-one using a YMCpack ODS-A / AQ column with a mobile phase of acetonitrile / water in a volume ratio of 50:50 at a flow rate of 2 mL / min to obtain the compound 7-butyl-4-methoxyoxepin-2(5H)-one, t R 19 minutes.

[0015] Preferably, the fermentation culture of the endophytic fungus Xylaria curta YSJ-5 of the step a is prepared, comprising the following steps: on a clean bench under sterile conditions, the YSJ-5 strain is transferred to a sterilized liquid culture medium. After inoculation, the strain is shaken and cultured on a constant temperature shaker at 28°C and 120r / min for 5 days to obtain a seed solution. Subsequently, each 25mL of seed solution is inoculated into a 1000mL conical flask containing 500mL of liquid culture medium, and a total of 160 conical flasks are prepared for large-scale fermentation. These conical flasks continue to be shaken and cultured on a shaker at 28°C and 120r / min for 7 days to obtain a liquid fermentation product. The collected liquid fermentation product is filtered through 4 layers of gauze to remove the mycelium, and then the filtrate is extracted with ethyl acetate, and the organic phase is concentrated by reduced pressure concentration to finally obtain about 30.3g of YSJ-5 crude extract.

[0016] The third object of the present invention is to provide the use of the compound 7-butyl-4-methoxyoxepin-2(5H)-one or its pharmaceutically acceptable salt in the preparation of antibacterial drugs.

[0017] Preferably, the antibacterial drug is a drug against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. The fourth object of the present invention is to provide an antibacterial drug comprising an effective amount of the compound 7-butyl-4-methoxyoxepin-2(5H)-one as an active ingredient, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

[0018] Preferably, the antibacterial drug is a drug against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.

[0019] The invention also provides use of the endophytic fungus Xylaria curta YSJ-5 in preparing the compound 7-butyl-4-methoxyoxepin-2(5H)-one.

[0020] The present invention has found through experiments that the compound 7-butyl-4-methoxyoxepin-2(5H)-one has good inhibitory activity against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus, with a MIC value of 6.3 μg / mL, and has no cytotoxicity, while the MIC values ​​of the positive control drug vancomycin are 0.63 and 1.3 μg / mL, respectively. This result shows that the compound 7-butyl-4-methoxyoxepin-2(5H)-one of the present invention has relatively significant antibacterial activity.

[0021] The invention prepares and separates a compound 7-butyl-4-methoxyoxepin-2(5H)-one from an endophytic fungus Xylaria curta YSJ-5. The compound 7-butyl-4-methoxyoxepin-2(5H)-one has antibacterial activity and can be used for preparing antibacterial drugs, thereby providing a candidate compound for researching and developing new antibacterial drugs and providing a scientific basis for developing and utilizing natural active substances of endophytic fungi of medicinal plants.

[0022] The endophytic fungus Xylaria curta YSJ-5 of the present invention has been disclosed in Wei SS, Lai JY, Chen C, Zhang YJ, Nong XM, Qiu KD, Duan FF, Zou ZX, Tan HB. Sesquiterpenes and α-pyrones from an endophytic fungus Xylaria curta YSJ-5. Phytochemistry, 2024, 220: 114011 [i.e., the strain Xylaria curta in the document]. The applicant also holds the strain and preserves it in the South China Agricultural Plant Molecular Analysis and Genetic Improvement Laboratory of the South China Botanical Garden in Guangzhou, and guarantees that it will be provided to the public within 20 years from the date of application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the compound 7-butyl-4-methoxyoxepin-2(5H)-one 1 H-NMR spectrum;

[0024] Figure 2 It is the compound 7-butyl-4-methoxyoxepin-2(5H)-one 13 C-NMR spectrum;

[0025] Figure 3 It is the COSY spectrum of compound 7-butyl-4-methoxyoxepin-2(5H)-one;

[0026] Figure 4 is the HSQC spectrum of compound 7-butyl-4-methoxyoxepin-2(5H)-one;

[0027] Figure 5 is the HMBC spectrum of the compound 7-butyl-4-methoxyoxepin-2(5H)-one;

[0028] Figure 6It is the NOESY spectrum of the compound 7-butyl-4-methoxyoxepin-2(5H)-one;

[0029] Figure 7 is the structure of compound 1 and 1 H- 1 H COSY and HMBC related signals. DETAILED DESCRIPTION

[0030] The following examples are provided to further illustrate the present invention, rather than to limit the present invention.

[0031] Embodiment 1:

[0032] 1. Isolation, purification and identification of the endophytic fungus Xylaria curta YSJ-5 from Zingiber officinale

[0033] The endophytic fungus YSJ-5 of the present invention was isolated from the leaves of the Alpinia galanga plant collected from the South China Botanical Garden in Guangzhou City, Guangdong Province in December 2020. It was identified by ITS sequence analysis, blast alignment and homology analysis, and the strain was identified as Xylaria curta and named Xylaria curta YSJ-5 (hereinafter referred to as strain YSJ-5).

[0034] 2. Solid fermentation of strain YSJ-5

[0035] On a clean bench under sterile conditions, the YSJ-5 strain was transferred to the sterilized PDB liquid culture medium. After inoculation, the strain was shaken in a constant temperature shaker at 28°C and 120r / min for 5 days to obtain seed liquid. Subsequently, each 25mL of seed liquid was inoculated into a 1000mL conical flask containing 500mL of liquid culture medium, and a total of 160 conical flasks were prepared for large-scale fermentation. These conical flasks continued to be shaken in a shaker at 28°C and 120r / min for 7 days to obtain liquid fermentation products. The collected liquid fermentation products were filtered through 4 layers of gauze to remove the mycelium, and then the filtrate was extracted with ethyl acetate, and the organic phase was concentrated by reduced pressure concentration to finally obtain about 30.3g of YSJ-5 crude extract.

[0036] 3. Preparation of compound 7-butyl-4-methoxyoxepin-2(5H)-one

[0037] The crude extract of YSJ-5 (30.3 g) was treated by reverse phase silica gel column chromatography, using methanol: water (30:70→100:0, v / v) and methanol: acetone (10:1→1:1, v / v) as the elution system for gradient elution. In this process, five components were separated: 30:70 methanol water polar segment AY-1 (4.3 g), 50:50 methanol water polar segment BY-2 (5.8 g), 70:30 methanol water polar segment CY-3 (3.0 g), 90:10 methanol water polar segment DY-4 (8.4 g) and the remaining polar segment EY-5 (8.6 g).

[0038] The 90:10 methanol / water polar segment component DY-4 (8.4 g) was chromatographed on a normal phase column with a gradient elution system of dichloromethane:methanol (100:1→1:1, v / v) to obtain six subcomponents: 100:1→10:1 polar segment DY-4-1 (0.1 g), 5:1 polar segment DY-4-2 (1.1 g), 4:1 polar segment DY-4-3 (1.2 g), 3:1 polar segment DY-4-4 (1.0 g), 2:1 polar segment DY-4-5 (1.0 g), and 1:1 polar segment DY-4-6 (1.2 g). First, the 100:1→10:1 polar segment DY-4-1 was separated by Sephadex LH-20 gel column chromatography using dichloromethane:methanol (1:3, v / v) as the elution system to obtain two parts DY-4-1-1 (0.07 g) and DY-4-1-2 (0.03 g). TLC thin layer chromatography was developed with n-hexane:ethyl acetate = 2:1 (v / v) to obtain the component DY-4-1-1 with Rf = 0.5-0.6. After normal phase column chromatography, petroleum ether:ethyl acetate (5:1→2:1, v / v) gradient elution was used, and then further purified by reverse phase semi-preparative high performance liquid chromatography using YMC pack ODS-A / AQ column, and the elution conditions were (MeCN / H 2 O, 50:50, v / v, 2 mL / min), from which 7-butyl-4-methoxyoxepin-2(5H)-one (3.0 mg, t R =19min), TLC thin layer chromatography was developed with n-hexane:ethyl acetate=2:1 (v / v), Rf=0.4-0.5.

[0039] 4. Structural identification of compound 7-butyl-4-methoxyoxepin-2(5H)-one

[0040] 1 H NMR, 13C NMR and HMBC NMR spectra were measured using a Bruker Advance-500 NMR spectrometer with tetramethylsilane (TMS) as the internal standard; ESI-MS data were measured using a VGAutospec-3000 mass spectrometer.

[0041] like Figure 1-6 As shown, Figure 1 It is the compound 7-butyl-4-methoxyoxepin-2(5H)-one 1 H-NMR spectrum; Figure 2 It is the compound 7-butyl-4-methoxyoxepin-2(5H)-one 13 C-NMR spectrum; Figure 3 It is the COSY spectrum of compound 7-butyl-4-methoxyoxepin-2(5H)-one; Figure 4 is the HSQC spectrum of compound 7-butyl-4-methoxyoxepin-2(5H)-one; Figure 5 is the HMBC spectrum of the compound 7-butyl-4-methoxyoxepin-2(5H)-one; Figure 6 This is the NOESY spectrum of the compound 7-butyl-4-meth oxyoxepin-2(5H)-one.

[0042] Compound 1 (7-butyl-4-methoxyoxepin-2(5H)-one): colorless oil. 1 H NMR spectrum (Table 1) shows that one methyl proton signal [δ H 0.90 (t, J = 7.0 Hz, 3H)], 1 methoxy proton signal [δ H 3.79 (s, 3H)], 2 olefin proton signals [δ H 5.23 (d, J = 1.3 Hz, 1H), 6.07 (dd, J = 2.5, 4.6 Hz, 1H)]. 13 C NMR and HSQC data (Table 1) show that there are 11 carbon signals in the structure of this compound, including 1 methyl carbon signal [δ C 13.8 (C-11)], one oxygen-linked methyl carbon signal [δ C 56.3 (C-4b)], 4 methylene carbon signals [δ C 33.9 (C-8), 32.0 (C-5), 26.7 (C-9), 22.2 (C-10)], 2 double bond methine carbon signals [δ C 90.3(C-3),89.9(C-6)], 3 quaternary carbon signals [δC 171.7(C-7),169.8(C-4a),164.0(C-2)].

[0043] In the HMBC spectrum ( Figure 7 ), the correlation from H-3 to C-4 and C-5 was observed, H 2 -5 to the correlation of C-4 and C-6, H-6 to the correlation of C-2 and C-4, H 3 -4b to C-4a correlation, combined 1 H- 1 H-6 / H in H COSY spectrum 2 -5 related signals, indicating that the compound has a seven-membered cyclic oxepin-2-one skeleton (Fernández-García et al., 2013). 1 H- 1 In the H COSY spectrum, another spin coupling system H 3 -11 / H 2 -10 / H 2 -9 / H 2 -8, indicating that the four carbon atoms C-11 / C-10 / C-9 / C-8 are directly connected. 2 -9 to C-7, C-8 and C-10, and H 2 The correlation signals from C-8 to C-7 indicated that the side chain was attached at C-7. Therefore, the structure of compound 1 was deduced and named 7-butyl-4-methoxyoxepin-2(5H)-one.

[0044] Table 1 NMR data of compound 7-butyl-4-methoxyoxepin-2(5H)-one (δin ppm, J in Hz, CDCl 3 )

[0045]

[0046]

[0047] It was determined that the chemical structure of compound 1 (7-butyl-4-methoxyoxepin-2(5H)-one) is as shown in formula (I).

[0048]

[0049] Embodiment 2:

[0050] 1. Experimental method: Vancomycin and polymyxin B were selected as positive control drugs, and the antibacterial ability of the compound 7-butyl-4-methoxyoxepin-2(5H)-one against Staphylococcus aureus (SA, CMCC 26003), methicillin-resistant Staphylococcus aureus (MRSA, JCSC 3063) and Escherichia coli (E. coli, ATCC 8739) was evaluated by microbroth dilution technique. In this study, resazurin colorimetry was used as an intuitive indicator to determine the minimum inhibitory concentration (MIC) value of the compound (Wang M, Zhao L, Chen K, et al., 2020. Antibacterial sesquiterpenes from the stems and roots of Thuja sutchuenensis [J]. Bioorganic Chemistry, 96: 103645). Resazurin, as a blue non-fluorescent dye, can be converted to pink by reductases in living cells, while cells lacking activity cannot cause color changes and maintain a blue state. This color change provides a convenient visual identification method for evaluating the antibacterial activity of the compound. Using the 96-well plate gradient dilution method, this study efficiently and simultaneously determined the MIC values ​​of multiple compounds under the same experimental conditions. The specific experimental steps are as follows:

[0051] 1. Dissolve the test compound in DMSO reagent and prepare its concentration to 1 mg / mL. For the positive control group, use sterile water to prepare vancomycin and polymyxin B to the same concentration.

[0052] 2. Take out the SA, MRSA and E. coli strains stored in 30% glycerol cryovials from the refrigerator, use a pipette to take 200 μL of bacterial solution and add it to the sterilized Mueller-Hinton Broth broth medium. Then, place it in a constant temperature shaking incubator set at 37°C for overnight activation in preparation for subsequent experiments.

[0053] 3. Take out the activated MHB medium containing bacterial solution and measure the concentration (OD) of the bacterial solution using a UV spectrophotometer. Dilute the bacterial solution with the culture medium to OD 600 The value is 0.07, and the bacterial concentration is 1.25×10 6 CFU / mL (recorded as solution A) was used for subsequent antibacterial experiments.

[0054] 4. Dilute the resazurin indicator to 0.1 mg / mL with sterile water to prepare a sterile aqueous solution (referred to as solution B).

[0055] 5. Mix solution A and solution B in a volume ratio of 3:2 to ensure uniform mixing (referred to as solution C). Then, the MIC value of the compound was determined by the two-fold dilution method.

[0056] 6. Add 180 μL of solution C to the first row of the 96-well culture plate, and add 100 μL to the remaining wells row by row. Add 20 μL of the prepared test compound sample and positive control to the first row of wells, set up 2 parallel wells for each sample, and dilute them in sequence.

[0057] After the samples were added, the 96-well plate was placed in a 37°C constant temperature incubator for 9 hours, and the color change of the indicator in the culture plate was monitored and recorded to determine the MIC value.

[0058] 2. Experimental results: The prepared compound 7-butyl-4-methoxyoxepin-2(5H)-one exhibited good antibacterial activity against MRSA and SA, with MIC values ​​of 6.3 μg / mL (the MIC values ​​of the positive control drug vancomycin were 0.63 and 1.3 μg / mL, respectively) (Table 2). This result shows that the compound 7-butyl-4-methoxyoxepin-2(5H)-one has significant antibacterial activity. Therefore, the present invention provides a candidate compound for the research and development of new antibacterial drugs and provides a scientific basis for the development and utilization of natural active substances of plant endophytic fungi.

[0059] Table 2 Antibacterial activity data of compound 7-butyl-4-methoxyoxepin-2(5H)-one (MIC, μg / mL)

[0060]

Claims

1. The compound represented by formula (I) 7-butyl-4-methoxyoxepin-2(5H)-one, 2. A method for preparing the compound 7-butyl-4-methoxyoxepin-2(5H)-one, characterized in that: It is isolated and prepared from the fermentation culture of the endophytic fungus Xylaria curta YSJ-5.

3. The preparation method according to claim 2, characterized in that: The following steps are involved: a. Preparation of solid fermentation culture of endophytic fungus Xylaria curta YSJ-5 of Ginger, the solid fermentation product was extracted with ethyl acetate, and the extract was concentrated to obtain an extract; b. The crude extract (30.3 g) was treated by reverse phase silica gel column chromatography, using methanol: water (30:70→100:0, v / v) and methanol: acetone (10:1→1:1, v / v) as the elution system for gradient elution. This process separated 5 components: AY-1 (4.3 g), BY-2 (5.8 g), CY-3 (3.0 g), DY-4 (8.4 g) and EY-5 (8.6 g). Component DY-4 (8.4 g) was chromatographed on a normal phase column using a gradient elution system of dichloromethane: methanol (100:1→1:1, v / v) to obtain six subcomponents: DY-4-1 (0.1 g), DY-4-2 (1.1 g), DY-4-3 (1.2 g), DY-4-4 (1.0 g), DY-4-5 (1.0 g), and DY-4-6 (1.2 g). First, DY-4-1 was chromatographed on a Sephadex LH-20 gel column using dichloromethane: methanol (1:3, v / v) as the elution system to separate two subcomponents, DY-4-1-1 (0.07 g) and DY-4-1-2 (0.03 g). TLC thin layer chromatography was developed with n-hexane: ethyl acetate = 2: 1 (v / v) to obtain component DY-4-1-1 with Rf = 0.5-0.

6. After normal phase column chromatography, petroleum ether: ethyl acetate (5: 1 → 2: 1, v / v) gradient elution was used, and then further purified by reverse phase semi-preparative high performance liquid chromatography. The elution conditions were (MeCN / H2O, 50:50, v / v, 2 mL / min). 7-butyl-4-methoxyoxepin-2(5H)-one (3.0 mg) was isolated therefrom. TLC thin layer chromatography was developed with n-hexane: ethyl acetate = 2: 1 (v / v) with Rf = 0.4-0.

5.

4. The preparation method according to claim 3, characterized in that: The component DY-4-1-1 was further subjected to semi-preparative HPLC to obtain the compound 7-butyl-4-methoxyoxepin-2(5H)-one using a YMC pack ODS-A / AQ column with a mobile phase of acetonitrile / water in a volume ratio of 50:50 at a flow rate of 2 mL / min to obtain the compound 7-butyl-4-methoxyoxepin-2(5H)-one. R 19 minutes.

5. The preparation method according to claim 3, characterized in that: The step a of preparing the fermentation culture of the endophytic fungus Xylaria curta YSJ-5 of Ginger includes the following steps: on a clean bench under sterile conditions, the YSJ-5 strain is transferred to a sterilized liquid culture medium. After inoculation, the strain is shaken and cultured on a constant temperature shaker at 28°C and 120r / min for 5 days to obtain a seed solution. Subsequently, each 25mL of seed solution is inoculated into a 1000mL conical flask containing 500mL of liquid culture medium, and a total of 160 conical flasks are prepared for large-scale fermentation. These conical flasks continue to be shaken and cultured on a shaker at 28°C and 120r / min for 7 days to obtain a liquid fermentation product. The collected liquid fermentation product is filtered through 4 layers of gauze to remove the mycelium, and then the filtrate is extracted with ethyl acetate, and the organic phase is concentrated by reduced pressure concentration to finally obtain about 30.3g of YSJ-5 crude extract.

6. Use of the compound 7-butyl-4-methoxyoxepin-2(5H)-one or a pharmaceutically acceptable salt thereof in the preparation of antibacterial drugs.

7. The use according to claim 6, characterized in that: The antibacterial drug is a drug against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.

8. An antibacterial drug, characterized in that: The invention comprises an effective amount of the compound 7-butyl-4-methoxyoxepin-2(5H)-one according to claim 1, or a pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier as an active ingredient.

9. The antibacterial drug according to claim 8, characterized in that: The antibacterial drug is a drug against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.

10. Use of the endophytic fungus Xylaria curta YSJ-5 in the preparation of the compound 7-butyl-4-methoxyoxepin-2(5H)-one according to claim 1.

Images