A quaternary ammonium salt compound containing a cyclic dipeptide structure, and its preparation method and application

Abstract

The present invention relates to the field of biomedicine technology, and in particular to a quaternary ammonium salt compound containing a cyclic dipeptide structure, a preparation method and an application thereof, wherein the quaternary ammonium salt compound containing a cyclic dipeptide structure has a structure shown in Formula I. Compared with the prior art, the present invention is innovative in structure, based on a cyclic histidine dimer, and for the first time, it is modified with multiple substituents containing quaternary ammonium salts and hydrophobic ends, thereby obtaining a series of small molecule cyclic antimicrobial peptides with good water solubility. The performance of the material can be regulated and screened by changing the quaternary ammonium salt substituent, and finally a small molecule cyclic quaternary ammonium salt antimicrobial material with good antimicrobial activity, high selectivity, low hemolytic toxicity and good biocompatibility is obtained.

Description

Technical Field

[0001] The present invention relates to the field of biomedicine technology, and in particular to a quaternary ammonium salt compound containing a cyclic dipeptide structure, and a preparation method and application thereof. Background Art

[0002] Since the discovery of penicillin, antibiotics have played an important role in the field of antimicrobial therapy. However, due to the abuse of antibiotics, microbial resistance to antibiotics is steadily increasing, resulting in the failure of traditional antibiotics, while the research and development of new antibiotics is almost at a standstill. Therefore, there is an urgent need to develop new antimicrobial drugs with broad-spectrum antimicrobial properties and less likely to induce microbial resistance.

[0003] As early as the last century, people have conducted a lot of research on the antibacterial effect of small molecule quaternary ammonium salts, and found that long-chain alkyl quaternary ammonium salts such as hexadecyltrimethylammonium bromide have strong antibacterial effects. However, organic small molecule quaternary ammonium salt antibacterial materials generally have the disadvantages of easy elution, easy volatility, difficult processing, poor chemical stability, etc. in long-term use. In addition, most quaternary ammonium salt materials are highly irritating, have poor biocompatibility, and usually have high hemolytic toxicity, which limits their application in organisms. They are mostly used as drug patches and are difficult to be administered orally or by injection.

[0004] Antimicrobial peptides have broad-spectrum antimicrobial activity, have a strong killing effect on bacteria, and are usually not easy to develop drug resistance. However, the content of antimicrobial peptides in animals and plants is extremely small. Extracting antimicrobial peptides from animals has low yield, long time, complex process, and high cost, and cannot achieve large-scale production. This has become the biggest obstacle to the practical application of antimicrobial peptides. Summary of the invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a quaternary ammonium salt compound containing a cyclic dipeptide structure with high biocompatibility, and a preparation method and application thereof.

[0006] To achieve the above object, the present invention provides a quaternary ammonium salt compound containing a cyclic dipeptide structure, having a structure shown in Formula I:

[0007] Formula I;

[0008] Wherein, n is an integer from 0 to 10; R1 is -N + R2R3R4;

[0009] The R2, R3, and R4 are independently selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C6-C20 aryl, or substituted or unsubstituted C4-C20 heteroaryl;

[0010] The substituents in the substituted C1-C10 alkyl, substituted C6-C20 aryl or substituted C4-C20 heteroaryl are each independently selected from one or more of halogen, C6-C20 aryl and C4-C20 heteroaryl.

[0011] Preferably, n is 2, 4, 6 or 8.

[0012] Preferably, R2, R3, and R4 are independently selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted condensed aromatic group formed by condensing 2-3 phenyl groups, or substituted or unsubstituted 5-membered to 6-membered monocyclic heteroaromatic group;

[0013] The substituents in the substituted C1-C10 alkyl, substituted phenyl, substituted fused aryl formed by condensing 2-3 phenyl groups, or substituted five-membered to six-membered monocyclic heteroaryl are independently selected from one or more of halogen, phenyl, fused aryl formed by condensing 2-3 phenyl groups, or five-membered to six-membered monocyclic heteroaryl.

[0014] Preferably, the R1 is selected from the structure shown in Formula II, Formula III or Formula IV:

[0015] Formula II; Formula III; Formula IV;

[0016] In formula II, m is an integer of 1 to 9.

[0017] Preferably, m is 1, 3, 5, 7 or 9.

[0018] The present invention also provides a method for preparing the above-mentioned quaternary ammonium salt compound containing a cyclic dipeptide structure, comprising the following steps:

[0019] The cyclic histidine dipeptide iodide having a structure of formula V is subjected to a substitution reaction with a tertiary amine NR2R3R4 to obtain a quaternary ammonium salt compound having a cyclic dipeptide structure having a structure of formula I;

[0020] Formula V; Formula I;

[0021] Wherein, n is an integer from 0 to 10; R1 is -N + R2R3R4;

[0022] The R2, R3, and R4 are independently selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C6-C20 aryl, or substituted or unsubstituted C4-C20 heteroaryl;

[0023] The substituted C1-C10 alkyl, substituted C6-C20 aryl or substituted C4-C20 heteroaryl are each independently selected from one or more of halogen, C6-C20 aryl and C4-C20 heteroaryl.

[0024] Preferably, the molar ratio of the cyclic histidine dipeptide iodide having the structure of formula V to the tertiary amine NR2R3R4 is 1:4-20;

[0025] The tertiary amine has a structure shown in Formula VI, Formula VII or Formula VIII:

[0026] Formula VI; Formula VII; Formula VIII;

[0027] The solvent for the substitution reaction includes one or more of dimethyl sulfoxide, N,N-dimethylformamide and acetonitrile;

[0028] The temperature of the substitution reaction is 40-100° C.; the time of the substitution reaction is 12-72 h.

[0029] Preferably, the cyclic histidine dipeptide iodide having the structure of formula V is prepared according to the following method:

[0030] The cyclic histidine dipeptide having a structure of Formula IX is reacted with a diiodoalkane having a structure of Formula X under alkaline conditions to obtain a cyclic histidine dipeptide iodide having a structure of Formula V;

[0031] Formula IX; Formula X.

[0032] Preferably, the molar ratio of the cyclic histidine dipeptide having the structure of formula IX to the diiodoalkane having the structure of formula X is 1:(4-20);

[0033] The alkaline condition is provided by an alkaline substance; the alkaline substance is selected from one or more of potassium carbonate, sodium hydroxide and potassium hydroxide;

[0034] The molar ratio of the cyclic histidine dipeptide having the structure of Formula IX to the alkaline substance is 1:(2-8);

[0035] The solvent of the reaction includes one or more of acetone, N,N-dimethylformamide and acetonitrile;

[0036] The reaction temperature is 60-100° C. and the reaction time is 24-72 h.

[0037] The present invention also provides an application of the quaternary ammonium salt compound containing a cyclic dipeptide structure as an antibacterial material.

[0038] The present invention provides a quaternary ammonium salt compound containing a cyclic dipeptide structure, which has a structure shown in formula I. Compared with the prior art, the present invention is innovative in structure. Based on the cyclic histidine dimer, it is modified with multiple substituents containing quaternary ammonium salts and hydrophobic ends for the first time, thereby obtaining a series of small molecule cyclic antibacterial peptides with good water solubility. The performance of the material can be regulated and screened by changing the quaternary ammonium salt substituents, and finally a small molecule cyclic quaternary ammonium salt antibacterial material with good antibacterial activity, high selectivity, low hemolytic toxicity and good biocompatibility is obtained. Experimental results show that the quaternary ammonium salt compound containing a cyclic dipeptide structure provided by the present invention has excellent antibacterial activity and high selectivity against Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli), and can destroy the integrity of bacterial cell membranes through physical interactions, showing the characteristics of rapid bacterial killing. The quaternary ammonium salt material containing a cyclic dipeptide provided by the present invention can suppress the survival rate of multiple bacteria to less than 1% within 30 minutes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a hydrogen nuclear magnetic resonance spectrum of the quaternary ammonium salt material containing a cyclic dipeptide prepared in Example 21 of the present invention;

[0040] Figure 2 A bar chart showing the minimum inhibitory concentration of the quaternary ammonium salt material containing a cyclic dipeptide prepared in Examples 5 to 32 of the present invention against Staphylococcus aureus;

[0041] Figure 3 A bar chart showing the minimum inhibitory concentration of the quaternary ammonium salt material containing a cyclic dipeptide prepared in Examples 5 to 32 of the present invention against Escherichia coli;

[0042] Figure 4 This is a diagram of bacterial morphology after being treated with the quaternary ammonium salt material containing cyclic dipeptide in Example 21 of the present invention;

[0043] Figure 5 This is a result graph of the number of colonies at different time points after treatment with the quaternary ammonium salt material containing a cyclic dipeptide in Example 21 of the present invention;

[0044] Figure 6 This is a graph showing the hemolytic toxicity characterization results of the quaternary ammonium salt material containing a cyclic dipeptide prepared in some embodiments of the present invention. DETAILED DESCRIPTION

[0045] In order to further illustrate the present invention, the following is a detailed description in conjunction with the embodiments. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the invention.

[0046] The present invention provides a quaternary ammonium salt compound containing a cyclic dipeptide structure, having a structure shown in Formula I:

[0047] Formula I;

[0048] Wherein, n is an integer from 0 to 10; R1 is -N + R2R3R4;

[0049] The R2, R3, and R4 are independently selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C6-C20 aryl, or substituted or unsubstituted C4-C20 heteroaryl;

[0050] The substituents in the substituted C1-C10 alkyl, substituted C6-C20 aryl or substituted C4-C20 heteroaryl are each independently selected from one or more of halogen, C6-C20 aryl and C4-C20 heteroaryl.

[0051] The n is any integer from 0 to 10. In some specific embodiments of the present invention, the n is 2, 4, 6 or 8, or a range value with any of the above values ​​as the upper limit or lower limit.

[0052] In a specific embodiment provided by the present invention, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C6-C20 aryl, or substituted or unsubstituted C4-C20 heteroaryl; the substituents in the substituted C1-C10 alkyl, substituted C6-C20 aryl, or substituted C4-C20 heteroaryl are each independently selected from one or more of halogen, C6-C20 aryl, and C4-C20 heteroaryl; preferably, the substituents in the substituted C1-C10 alkyl, substituted C6-C20 aryl, or substituted C4-C20 heteroaryl are each independently selected from one or more of halogen, C6-C20 aryl, and C4-C20 heteroaryl. More preferably, the substituents in the substituted C1~C10 alkyl, substituted C6~C20 aryl or substituted C4~C20 heteroaryl are each independently selected from one or more of halogen, phenyl, a condensed ring aryl formed by condensing 2~3 phenyls or a five-membered to six-membered monocyclic heteroaryl; More preferably, the substituents in the substituted C1~C10 alkyl, substituted C6~C20 aryl or substituted C4~C20 heteroaryl are each independently selected from one or more of halogen, phenyl or naphthyl; the halogen is any halogen well known to those skilled in the art without any special limitation, and is preferably Cl, Br or I in the present invention.

[0053] In a specific embodiment provided by the present invention, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1~C10 alkyl, substituted or unsubstituted C6~C10 aryl, or substituted or unsubstituted C4~C10 heteroaryl; the substituents in the substituted C1~C10 alkyl, substituted C6~C10 aryl, or substituted C4~C10 heteroaryl are each independently selected from one or more of halogen, C6~C20 aryl, and C4~C20 heteroaryl; preferably, the substituents in the substituted C1~C10 alkyl, substituted C6~C10 aryl, or substituted C4~C10 heteroaryl are each independently selected from one or more of halogen, C6~C10 More preferably, the substituents in the substituted C1~C10 alkyl, substituted C6~C10 aryl or substituted C4~C10 heteroaryl are each independently selected from one or more of halogen, phenyl, a condensed ring aryl formed by 2~3 phenyls or a five-membered to six-membered monocyclic heteroaryl; More preferably, the substituents in the substituted C1~C10 alkyl, substituted C6~C10 aryl or substituted C4~C10 heteroaryl are each independently selected from one or more of halogen, phenyl or naphthyl; the halogen is any halogen well known to those skilled in the art without any particular limitation, and in the present invention, Cl, Br or I are preferred.

[0054] In a specific embodiment provided by the present invention, R2, R3, and R4 are each independently selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted phenyl, substituted or unsubstituted fused ring aromatic group formed by condensing 2-3 phenyl groups, or substituted or unsubstituted five-membered to six-membered monocyclic heteroaryl; the substituents in the substituted C1-C10 alkyl, substituted phenyl, substituted fused ring aromatic group formed by condensing 2-3 phenyl groups, or substituted five-membered to six-membered monocyclic heteroaryl are each independently selected from one or more of halogen, C6-C20 aryl, and C4-C20 heteroaryl; preferably, the substituents in the substituted C1-C10 alkyl, substituted phenyl, substituted fused ring aromatic group formed by condensing 2-3 phenyl groups, or substituted five-membered to six-membered monocyclic heteroaryl are each independently selected from More preferably, the substituents in the substituted C1~C10 alkyl, substituted phenyl, substituted fused ring aryl formed by condensing 2~3 phenyls or substituted five-membered to six-membered monocyclic heteroaryl are independently selected from halogen, phenyl, fused ring aryl formed by condensing 2~3 phenyls or one or more of five-membered to six-membered monocyclic heteroaryl; More preferably, the substituents in the substituted C1~C10 alkyl, substituted phenyl, substituted fused ring aryl formed by condensing 2~3 phenyls or substituted five-membered to six-membered monocyclic heteroaryl are independently selected from halogen, phenyl or naphthyl; the halogen is any halogen well known to those skilled in the art without special restrictions, and is preferably Cl, Br or I in the present invention.

[0055] In a specific embodiment provided by the present invention, the R1 is selected from the structure shown in Formula II, Formula III or Formula IV:

[0056] Formula II; Formula III; Formula IV;

[0057] In formula II, m is an integer of 1 to 9. In some specific embodiments of the present invention, m is 1, 3, 5, 7, 9, or a range value with the above values ​​as the upper or lower limit.

[0058] Curved lines indicate connection locations.

[0059] The quaternary ammonium salt compound provided by the present invention is based on a cyclic histidine dimer, which is modified with a quaternary ammonium salt to obtain an organic small molecule antibacterial material with good antibacterial activity, high selectivity and low toxicity. In addition, due to the cyclic dipeptide structure, it has good biocompatibility and greatly reduces hemolytic toxicity.

[0060] The quaternary ammonium salt compound containing a cyclic dipeptide provided by the present invention has excellent antibacterial activity and high selectivity against Gram-positive bacteria Staphylococcus aureus (S. aureus) and Gram-negative bacteria Escherichia coli (E. coli), and can destroy the integrity of bacterial cell membranes through physical interactions, showing the characteristics of rapid bacterial killing. The quaternary ammonium salt compound containing a cyclic dipeptide provided by the present invention can suppress the survival rate of multiple bacteria to less than 1% within 30 minutes.

[0061] The present invention also provides a method for preparing the quaternary ammonium salt compound containing a cyclic dipeptide structure, comprising the following steps: subjecting a cyclic histidine dipeptide iodide having a structure of formula V to a substitution reaction with a tertiary amine NR2R3R4 to obtain a quaternary ammonium salt compound containing a cyclic dipeptide structure having a structure of formula I;

[0062] Formula V; Formula I;

[0063] Wherein, n is an integer from 0 to 10; R1 is -N + R2R3R4;

[0064] The R2, R3, and R4 are independently selected from substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C6-C20 aryl, or substituted or unsubstituted C4-C20 heteroaryl;

[0065] The substituted C1-C10 alkyl, substituted C6-C20 aryl or substituted C4-C20 heteroaryl are each independently selected from one or more of halogen, C6-C20 aryl and C4-C20 heteroaryl.

[0066] The range of n in the cyclic histidine dipeptide iodide having the structure of Formula V is the same as described above and will not be repeated here.

[0067] In the above-mentioned tertiary amine NR2R3R4, the ranges of R2, R3 and R4 are the same as those described above and will not be repeated here.

[0068] In some specific embodiments of the present invention, the tertiary amine NR2R3R4 has a structure shown in Formula VI, Formula VII or Formula VIII:

[0069] Formula VI; Formula VII; Formula VIII;

[0070] m is an integer of 1 to 9. The range of m is the same as described above and will not be repeated here.

[0071] The present invention has no particular limitation on the source of the tertiary amine, which can be any commercially available one.

[0072] According to the present invention, the molar ratio of the cyclic histidine dipeptide iodide having the structure of formula V to the tertiary amine NR2R3R4 is preferably 1:4-20, more preferably 1:(5-15), further preferably 1:(8-12), and most preferably 1:10.

[0073] According to the present invention, the cyclic histidine dipeptide iodide having the structure of formula V is subjected to a substitution reaction with a tertiary amine NR2R3R4 in a solvent; the solvent for the substitution reaction preferably includes one or more of dimethyl sulfoxide, N,N-dimethylformamide and acetonitrile.

[0074] The present invention has no particular limitation on the amount of the above-mentioned solvent, and the amount of the solvent used can be used to dissolve the reaction raw materials. In a specific embodiment provided by the present invention, the ratio of the cyclic histidine dipeptide iodide having the structure of formula V to the solvent is preferably 1-5 g: 10-50 mL, more preferably 1-3 g: 10-50 mL, more preferably 1 g: 10-50 mL, and most preferably 1 g: 30-40 mL.

[0075] According to the present invention, the temperature of the substitution reaction is preferably 40-100°C, more preferably 60-90°C, more preferably 70-80°C, and most preferably 75°C; the time of the substitution reaction is preferably 12-72 h, more preferably 24-72 h, and more preferably 48 h.

[0076] In some specific embodiments of the present invention, after the above substitution reaction is completed, the following steps are further included:

[0077] The product solution after the reaction is precipitated with ether, washed and dried to obtain a quaternary ammonium salt compound containing a cyclic dipeptide structure having a structure of formula I.

[0078] In some specific embodiments of the present invention, the volume ratio of the solvent in the substitution reaction to diethyl ether is preferably 1:5-10, more preferably 1:8-10.

[0079] The present invention has no particular limitation on the sedimentation, washing and drying methods, and any sedimentation, washing and drying methods well known to those skilled in the art may be used.

[0080] The present invention has no particular limitation on the preparation method of the cyclic histidine dipeptide iodide having the structure of formula V, and the cyclic histidine dipeptide iodide can be prepared according to methods well known to those skilled in the art. Preferably, the cyclic histidine dipeptide iodide having the structure of formula IX is reacted with a diiodoalkane having the structure of formula X under alkaline conditions to obtain a cyclic histidine dipeptide iodide having the structure of formula V;

[0081] Formula IX; Formula X.

[0082] Wherein, n is any integer from 0 to 10.

[0083] The range of n is the same as described above and will not be repeated here.

[0084] In some specific embodiments of the present invention, the diiodoalkane is specifically 1,4-diiodobutane, 1,6-diiodohexane, 1,8-diiodooctane or 1,10-diiododecane.

[0085] According to the present invention, the molar ratio of the cyclic histidine dipeptide having the structure of formula IX to the diiodoalkane having the structure of formula X is preferably 1:(4-20), more preferably 1:(4-15), further preferably 1:(4-10), further preferably 1:(4-8), and most preferably 1:6.

[0086] According to the present invention, the alkaline conditions are preferably provided by an alkaline substance; the alkaline substance is preferably one or more of potassium carbonate, sodium hydroxide and potassium hydroxide; the molar ratio of the cyclic histidine dipeptide having the structure of formula IX to the alkaline substance is preferably 1:(2-8), more preferably 1:(2-5), further preferably 1:(2-4), and most preferably 1:3.

[0087] According to the present invention, the reaction is preferably carried out in an organic solvent; the solvent of the reaction preferably includes one or more of acetone, N,N-dimethylformamide and acetonitrile.

[0088] The present invention has no particular limitation on the amount of the above-mentioned solvent, and any amount that can be used to dissolve the reaction raw materials can be used. In a specific embodiment provided by the present invention, 1-5 g: 10-50 mL, more preferably 1-3 g: 10-50 mL, more preferably 1 g: 10-50 mL, and most preferably 1 g: 20-30 mL.

[0089] According to the present invention, the reaction temperature is preferably 60-100°C, more preferably 60-90°C, more preferably 70-80°C, and most preferably 75°C; the reaction time is preferably 24-72 h, more preferably 36-72 h, and more preferably 48 h.

[0090] In some specific embodiments of the present invention, after the above reaction is completed, the following steps are further included:

[0091] The product solution after the reaction is precipitated with ether, washed and dried to obtain a cyclic histidine dipeptide iodide having a structure of formula V.

[0092] In some specific embodiments of the present invention, the volume ratio of the solvent in the reaction to diethyl ether is preferably 1:5-10, more preferably 1:8-10.

[0093] The present invention has no particular limitation on the sedimentation, washing and drying methods, and any sedimentation, washing and drying methods well known to those skilled in the art may be used.

[0094] The present invention has no particular limitation on the source of the cyclic histidine dipeptide having the structure of Formula IX. Optionally, the cyclic histidine dipeptide having the structure of Formula IX is prepared according to the method disclosed in Chinese Patent Publication No. CN113754598B.

[0095] In a specific embodiment provided by the present invention, the cyclic histidine dipeptide having the structure of formula IX is prepared according to the following method: 45 g of L-histidine raw material and 180 mL of ethylene glycol are added to a round-bottom flask, the heating is turned on, the heating temperature is set to 197°C, and the reaction is refluxed for 24 hours. The reaction solution is poured into 800 mL of deionized water for sedimentation, filtered, and then stirred and washed with 800 mL of deionized water, repeated three times, and vacuum dried to obtain a product, which is a cyclic histidine dipeptide having the structure shown in formula (IX).

[0096] The quaternary ammonium salt compound containing a cyclic dipeptide structure provided by the present invention is simple to synthesize and easy to process, and at the same time, because it contains a cyclic peptide structure, it has good biocompatibility.

[0097] The quaternary ammonium salt compound containing a cyclic dipeptide provided by the present invention can show good in vitro bactericidal effect on Gram-positive and Gram-negative bacteria, can interact with bacterial cell membranes to cause bacterial death, and shows rapid bactericidal kinetics, and can kill more than 99% of bacteria within 30 minutes.

[0098] Based on this, the present invention also provides the use of the above-mentioned quaternary ammonium salt compound containing a cyclic dipeptide structure as an antibacterial material.

[0099] The present invention also provides an application of the quaternary ammonium salt compound containing a cyclic dipeptide structure in the preparation of antibacterial drugs.

[0100] To further illustrate the present invention, a quaternary ammonium salt compound containing a cyclic dipeptide structure, a preparation method thereof and an application thereof provided by the present invention are described in detail below in conjunction with examples.

[0101] The present invention has no particular limitation on the sources of all raw materials, and any raw materials purchased from the market or prepared according to conventional methods known to those skilled in the art can be used.

[0102] The standard strains of Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) were purchased from Shandong Lu Microbiological Technology Co., Ltd. Methicillin-resistant Staphylococcus aureus (MRSA ATCC 43300) was provided by the First Clinical Hospital of Jilin University. Example 1

[0103] Synthesis of cyclic histidine dipeptide iodide having the structure of formula (V), wherein n=2:

[0104] Weigh 1.0 g (3.65 mmol) of cyclic histidine dimer having the structure of formula (IX), add 20 mL of DMF and 1.51 g (10.95 mmol) of potassium carbonate, then add 6.77 g (21.9 mmol) of 1,4-diiodobutane having the structure of formula (X), stir and react at 75°C for 48 h, pour into 160 mL of ether for sedimentation, wash the precipitate with ether after centrifugation and dry to obtain a yellow powder product, which is the iodide of cyclic histidine dipeptide having the structure of formula (V). Example 2

[0105] Synthesis of cyclic histidine dipeptide iodide having the structure of formula (V), wherein n=4:

[0106] Weigh 1.0 g (3.65 mmol) of a cyclic histidine dimer having a structure of formula (IX), add 20 mL of DMF and 1.51 g (10.95 mmol) of potassium carbonate, then add 7.39 g (21.9 mmol) of 1,6-diiodohexane having a structure of formula (X), stir the reaction at 75°C for 48 h, pour into 160 mL of ether for sedimentation, centrifuge, wash the precipitate with ether and dry it to obtain a yellow powder product, which is a cyclic histidine dipeptide iodide having a structure of formula (V). Example 3

[0107] Synthesis of cyclic histidine dipeptide iodide having the structure of formula (V), wherein n=6:

[0108] Weigh 1.0 g (3.65 mmol) of cyclic histidine dimer having the structure of formula (IX), add 20 mL of DMF and 1.51 g (10.95 mmol) of potassium carbonate, then add 8.00 g (21.9 mmol) of 1,8-diiodooctane having the structure of formula (X), stir and react at 75°C for 48 h, pour into 160 mL of ether for sedimentation, wash the precipitate with ether after centrifugation and dry to obtain a yellow powder product, which is the iodide of cyclic histidine dipeptide having the structure of formula (V). Example 4

[0109] Synthesis of cyclic histidine dipeptide iodide having the structure of formula (V), wherein n=8:

[0110] Weigh 1.0 g (3.65 mmol) of cyclic histidine dimer having the structure of formula (IX), add 20 mL of DMF and 1.51 g (10.95 mmol) of potassium carbonate, then add 8.62 g (21.9 mmol) of 1,10-diiododecane having the structure of formula (X), stir and react at 75°C for 48 h, pour into 160 mL of ether for sedimentation, wash the precipitate with ether after centrifugation and dry to obtain a yellow powder product, which is the iodide of cyclic histidine dipeptide having the structure of formula (V). Example 5

[0111] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=2 in both the structures of formula (I) and formula (V):

[0112] 0.301 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.219 g (3.00 mmol) of N,N-dimethylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 6

[0113] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=2 in both the structures of formula (I) and formula (V):

[0114] 0.301 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.304 g (3.00 mmol) of N,N-dimethylbutylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 7

[0115] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=2 in both the structures of formula (I) and formula (V):

[0116] 0.301 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.388 g (3.00 mmol) of N,N-dimethylhexylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 8

[0117] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=2 in both the structures of formula (I) and formula (V):

[0118] 0.301 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.472 g (3.00 mmol) of N, N-dimethyloctylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 9

[0119] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=2 in both the structures of formula (I) and formula (V):

[0120] 0.301 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.556 g (3.00 mmol) of N, N-dimethyldecylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 10

[0121] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=2 in both the structures of formula (I) and formula (V):

[0122] 0.301 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.406 g (3.00 mmol) of N, N-dimethylbenzylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 11

[0123] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=2 in both the structures of formula (I) and formula (V):

[0124] 0.301 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.448 g (3.00 mmol) of N,N-dimethyl-2-phenylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 12

[0125] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=4 in both the structures of formula (I) and formula (V):

[0126] 0.335 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.219 g (3.00 mmol) of N,N-dimethylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 13

[0127] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=4 in both the structures of formula (I) and formula (V):

[0128] 0.335 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.304 g (3.00 mmol) of N,N-dimethylbutylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 14

[0129] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=4 in both the structures of formula (I) and formula (V):

[0130] 0.335 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.388 g (3.00 mmol) of N,N-dimethylhexylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 15

[0131] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=4 in both the structures of formula (I) and formula (V):

[0132] 0.335 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.472 g (3.00 mmol) of N,N-dimethyloctylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Example 16

[0133] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=4 in both the structures of formula (I) and formula (V):

[0134] 0.335 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.556 g (3.00 mmol) of N,N-dimethyldecylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 17

[0135] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=4 in both the structures of formula (I) and formula (V):

[0136] 0.335 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.406 g (3.00 mmol) of N, N-dimethylbenzylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 18

[0137] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=4 in both the structures of formula (I) and formula (V):

[0138] 0.335 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.448 g (3.00 mmol) of N,N-dimethyl-2-phenylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 19

[0139] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=6 in both the structures of formula (I) and formula (V):

[0140] 0.369 g (0.300 mmol) of the iodide of cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.219 g (3.00 mmol) of N,N-dimethylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 20

[0141] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=6 in both the structures of formula (I) and formula (V):

[0142] 0.369 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.304 g (3.00 mmol) of N, N-dimethylbutylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 21

[0143] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=6 in both the structures of formula (I) and formula (V):

[0144] 0.369 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.388 g (3.00 mmol) of N,N-dimethylhexylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 22

[0145] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=6 in both the structures of formula (I) and formula (V):

[0146] 0.369 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.472 g (3.00 mmol) of N, N-dimethyloctylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 23

[0147] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=6 in both the structures of formula (I) and formula (V):

[0148] 0.369 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.556 g (3.00 mmol) of N,N-dimethyldecylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 24

[0149] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=6 in both the structures of formula (I) and formula (V):

[0150] 0.369 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.406 g (3.00 mmol) of N, N-dimethylbenzylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 25

[0151] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=6 in both the structures of formula (I) and formula (V):

[0152] 0.369 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.448 g (3.00 mmol) of N,N-dimethyl-2-phenylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 26

[0153] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=8 in both the structures of formula (I) and formula (V):

[0154] 0.403 g (0.300 mmol) of the iodide of cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.219 g (3.00 mmol) of N,N-dimethylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 27

[0155] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=8 in both the structures of formula (I) and formula (V):

[0156] 0.403 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.304 g (3.00 mmol) of N,N-dimethylbutylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 28

[0157] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=8 in both the structures of formula (I) and formula (V):

[0158] 0.403 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.388 g (3.00 mmol) of N,N-dimethylhexylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 29

[0159] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=8 in both the structures of formula (I) and formula (V):

[0160] 0.403 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.472 g (3.00 mmol) of N,N-dimethyloctylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 30

[0161] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=8 in both the structures of formula (I) and formula (V):

[0162] 0.403 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.556 g (3.00 mmol) of N,N-dimethyldecylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 80 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 31

[0163] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=8 in both the structures of formula (I) and formula (V):

[0164] 0.403 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.406 g (3.00 mmol) of N, N-dimethylbenzylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I). Embodiment 32

[0165] Synthesis of a quaternary ammonium salt material containing a cyclic dipeptide having a structure of formula (I), wherein n=8 in both the structures of formula (I) and formula (V):

[0166] 0.403 g (0.300 mmol) of the iodide of the cyclic histidine dipeptide having the structure of formula (V) was weighed and dissolved in 10 mL of DMF, and then 0.448 g (3.00 mmol) of N,N-dimethyl-2-phenylethylamine was added thereto. After stirring and reacting at 75°C for 48 h, the mixture was poured into 160 mL of ether for sedimentation. After centrifugation, the precipitate was washed with ether and dried to obtain a yellow powder product, which is a quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I).

[0167] Detection Example

[0168] The quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I) obtained in the above embodiment of the present invention was tested.

[0169] See also Figure 1 , Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the quaternary ammonium salt material containing a cyclic dipeptide prepared in Example 21 of the present invention. Figure 1 It can be seen that the side group of the cyclic histidine dipeptide iodide is successfully substituted into a quaternary ammonium salt form, thereby obtaining a quaternary ammonium salt material having the structure of formula (I).

[0170] The in vitro antibacterial activity of quaternary ammonium salt materials containing cyclic dipeptides was tested by well plate assay:

[0171] The quaternary ammonium salt material containing a cyclic dipeptide having the structure of formula (I) prepared in some embodiments of the present invention was co-cultured with Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922) or methicillin-resistant Staphylococcus aureus (ATCC 43300), and the minimum inhibitory concentration (MIC) thereof was detected:

[0172] First, Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), or methicillin-resistant Staphylococcus aureus (MRSA) were inoculated in fresh MH medium and cultured at 37°C for 12 h. The bacteria in the logarithmic phase were diluted with fresh medium and the bacteria (100.0 μL, 1×10 6CFU / mL) was added to a 96-well plate. The quaternary ammonium salt material containing the cyclic dipeptide was diluted with PBS (pH=7.4) by gradient dilution. Then, PBS (pH = 7.4) as a control group and the diluted quaternary ammonium salt material containing the cyclic dipeptide were added to the 96-well plate, shaken for 60 s using a microplate reader to mix them evenly, and the optical density at 600 nm was measured. The culture plate was incubated at 37°C for 24 h, and then the optical density of the microbial solution was measured at 600 nm. MIC is the lowest concentration at which no bacterial growth can be detected.

[0173] The minimum inhibitory concentration results of the quaternary ammonium salt materials containing cyclic dipeptides having the structure of formula (I) prepared in Examples 5 to 32 against different bacteria are shown in Table 1.

[0174] Table 1 Minimum inhibitory concentration (MIC, µg / mL) of the quaternary ammonium salt materials containing cyclic dipeptides prepared in Examples 5 to 32 against different bacteria

[0175]

[0176] As can be seen from Table 1, the quaternary ammonium salt materials containing cyclic dipeptides prepared in Examples 5 to 32 have antibacterial activity against Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922), and the MIC value of the materials can reach as low as 2 µg / mL. The bar chart drawn based on the experimental results in Table 1 is as follows: Figure 2 and Figure 3 As shown, Figure 2 This is a bar chart showing the minimum inhibitory concentration of the quaternary ammonium salt material containing cyclic dipeptide prepared in Examples 5 to 32 against Staphylococcus aureus. Figure 3 The bar chart shows the minimum inhibitory concentrations of the quaternary ammonium salt materials containing cyclic dipeptides against Escherichia coli prepared in Examples 5 to 32. For some of the materials with excellent antibacterial effects, the minimum inhibitory concentrations against MRSA were further characterized, and the results are shown in Table 2.

[0177] Table 2 Minimum inhibitory concentration (MIC, µg / mL) of quaternary ammonium salt materials prepared in some examples against MRSA

[0178]

[0179] It can be seen from Table 2 that some examples, especially the quaternary ammonium salt materials prepared in Example 21, have good antibacterial activity against methicillin-resistant Staphylococcus aureus (ATCC 43300).

[0180] The bacterial cell membrane-destroying ability of the quaternary ammonium salt material containing cyclic dipeptide was verified by photographing the morphology of bacterial cell membranes after treatment with the material using a scanning electron microscope:

[0181] First, Staphylococcus aureus and Escherichia coli were inoculated into fresh MH medium and cultured at 37°C for 12 h, washed three times with PBS (pH = 7.4) and resuspended. The final concentration of the bacterial solution was 2 × 10 6 CFU / mL. 500.0 μL of bacterial suspension and 500.0 μL of quaternary ammonium salt material solution containing cyclic dipeptide at a concentration of 20 μg / mL were mixed evenly, incubated at 37°C for 120 min, and the treated bacterial samples were collected by centrifugation and then washed twice with PBS. Next, they were fixed with 4% paraformaldehyde solution at 25°C for 12 h. Subsequently, the samples were washed once with PBS and dehydrated with gradient ethanol solutions (25%, 50%, 75% and 100%). Finally, the bacterial samples were dropped on a silicon wafer and the treated bacterial samples were observed by scanning electron microscopy (SEM).

[0182] See also Figure 4 , Figure 4 This is the bacterial morphology after being treated with the quaternary ammonium salt material containing cyclic dipeptide in Example 21 of the present invention.

[0183] from Figure 4 It can be seen that the quaternary ammonium salt material containing cyclic dipeptide has a good ability to destroy bacterial cell membranes.

[0184] The bactericidal kinetics of quaternary ammonium salt materials containing cyclic dipeptides against Staphylococcus aureus and Escherichia coli were verified by using the bacterial plate count method:

[0185] Bacteria (Staphylococcus aureus or Escherichia coli) were inoculated in fresh MH medium and cultured at 37°C for 12 h, washed three times with PBS (pH = 7.4) and resuspended to obtain a concentration of 1×10 6 CFU / mL bacterial solution. The quaternary ammonium salt material containing cyclic dipeptide was dissolved in PBS to prepare solutions with concentrations of 2×MIC and 4×MIC, and ofloxacin, a commonly used clinical antibiotic, was used as a control. Ofloxacin was dissolved in PBS to prepare a 2 μg / mL solution. 1 mL of each of the three solutions and PBS was taken in a centrifuge tube, and 1 mL of the above bacterial suspension was added to each of the four groups, mixed evenly, and treated for 2, 5, 10, 20, 30, 60 and 120 min, respectively. At each time point, 100.0 μL of the mixed solution was added dropwise to the LB agar plate and spread evenly, cultured at 37°C for 24h, and the bactericidal rate of the quaternary ammonium salt material containing cyclic dipeptide was calculated by colony counting. According to the final concentration of each group of materials after mixing with the bacterial solution, each group was named: 1×MIC group, 2×MIC group, ofloxacin group, and PBS group.

[0186] See also Figure 5 , Figure 5The statistical results of the number of colonies at different time points after treatment with the quaternary ammonium salt material containing cyclic dipeptide in Example 21 of the present invention are shown in Table 3. The data corresponding to each point in the figure are shown in Table 3.

[0187] Table 3 Statistical table of bactericidal kinetics of quaternary ammonium salt materials prepared in Example 21 against Staphylococcus aureus and Escherichia coli

[0188]

[0189] from Figure 5 It can be seen that the quaternary ammonium salt material containing cyclic dipeptide has rapid bactericidal kinetics.

[0190] The biocompatibility of the quaternary ammonium salt material containing cyclic dipeptide was verified by characterizing the hemolytic toxicity of the material to sheep erythrocytes:

[0191] First, a certain volume of 4% sheep red blood cells was centrifuged, washed three times with PBS (pH=7.4), and then resuspended in an equal volume of PBS solution. The materials prepared in each embodiment listed in Table 1 were dissolved in PBS to prepare a solution with a concentration of 1 mg / mL, 500 μL of each group of materials were taken in a centrifuge tube, and 500 μL of the above sheep red blood cell suspension was added and mixed. 500 μL of deionized water and sheep red blood cells were mixed in equal volumes as a positive control group, and 500 μL of PBS solution and sheep red blood cells were mixed in equal volumes as a negative control group. Each group was incubated in a 37°C incubator for 2 hours, then centrifuged, and the color depth of the supernatant in the centrifuge tube was recorded by taking a photo. The darker the color of the supernatant, the closer it is to the positive control group, indicating that the more red blood cells are ruptured, and the stronger the hemolytic toxicity of the corresponding material.

[0192] See also Figure 6 , Figure 6 This is a graph showing the hemolytic toxicity characterization results of the quaternary ammonium salt materials containing cyclic dipeptides prepared in various examples listed in Table 2.

[0193] from Figure 6 It can be seen that the quaternary ammonium salt materials containing cyclic dipeptides prepared in Examples 15, 20, 21, 24, 25, and 27 have good biocompatibility and low hemolytic toxicity, and almost do not cause rupture of red blood cells at a concentration far higher than the bactericidal concentration of the material (500 μg / mL).

[0194] The above is a detailed introduction to a quaternary ammonium salt antibacterial material containing a cyclic dipeptide structure provided by the present invention, its preparation method and application. The principle and implementation mode of the present invention are described in detail using specific examples herein. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in the technical field, without departing from the principle of the present invention, the present invention can also be improved and modified in several ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims, and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the textual expression of the claims, or if they include equivalent structural elements that are not substantially different from the textual expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A quaternary ammonium salt compound containing a cyclic dipeptide structure, characterized in that: It has the structure shown in Formula I: Where R1 is -N + R2R3R4; Said n is 2, 4, 6 or 8; The R2, R3, and R4 are independently selected from substituted or unsubstituted C1-C10 alkyl and phenyl groups; The substituents in the substituted C1-C10 alkyl group are each independently selected from phenyl.

2. The quaternary ammonium salt compound according to claim 1, characterized in that The R1 is selected from the structure shown in Formula II, Formula III or Formula IV: In formula II, m is an integer of 1-9.

3. The quaternary ammonium salt compound according to claim 2, characterized in that The m is 1, 3, 5, 7 or 9.

4. A method for preparing a quaternary ammonium salt compound containing a cyclic dipeptide structure according to claim 1, characterized in that: The following steps are involved: The cyclic histidine dipeptide iodide having a structure of formula V is subjected to a substitution reaction with a tertiary amine NR2R3R4 to obtain a quaternary ammonium salt compound having a cyclic dipeptide structure having a structure of formula I; 5. The preparation method according to claim 4, characterized in that: The molar ratio of the cyclic histidine dipeptide iodide having the structure of formula V to the tertiary amine NR2R3R4 is 1:4-20; The tertiary amine has a structure shown in Formula VI, Formula VII or Formula VIII: The solvent for the substitution reaction includes one or more of dimethyl sulfoxide, N,N-dimethylformamide and acetonitrile; The temperature of the substitution reaction is 40 to 100° C.; the time of the substitution reaction is 12 to 72 hours.

6. The preparation method according to claim 4, characterized in that: The cyclic histidine dipeptide iodide having the structure of formula V is prepared according to the following method: The cyclic histidine dipeptide having a structure of Formula IX is reacted with a diiodoalkane having a structure of Formula X under alkaline conditions to obtain a cyclic histidine dipeptide iodide having a structure of Formula V; 7. The preparation method according to claim 6, characterized in that: The molar ratio of the cyclic histidine dipeptide having the structure of formula IX to the diiodoalkane having the structure of formula X is 1:4-20; The alkaline condition is provided by an alkaline substance; the alkaline substance is selected from one or more of potassium carbonate, sodium hydroxide and potassium hydroxide; The molar ratio of the cyclic histidine dipeptide having the structure of Formula IX to the alkaline substance is 1:2-8; The solvent of the reaction includes one or more of acetone, N,N-dimethylformamide and acetonitrile; The reaction temperature is 60-100° C.; the reaction time is 24-72 hours.

8. Use of the quaternary ammonium salt compound containing a cyclic dipeptide structure according to any one of claims 1 to 3 or the quaternary ammonium salt compound containing a cyclic dipeptide structure prepared by the preparation method according to any one of claims 4 to 7 in the preparation of antibacterial materials.

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