Chinese herbal medicine antibacterial packaging film and preparation method thereof

Abstract

The invention discloses a Chinese herbal medicine antibacterial packaging film and a preparation method thereof. The preparation method of the Chinese herbal medicine antibacterial packaging film comprises the following steps: (1) heating and stirring polyethylene glycol and chlorogenic acid powder in a solvent, and uniformly mixing to obtain a polyol system; and (2) adding a dicyclohexylmethane 4, 4 '-diisocyanate solution into the polyol system, continuously heating and stirring under the action of a catalyst, after the reaction is finished, casting onto a template, standing to remove bubbles, and drying to obtain the Chinese herbal medicine antibacterial film. Researches show that the Chinese herbal medicine antibacterial packaging film prepared by the method has good antibacterial performance; the surface of chlorogenic acid is negatively charged, so that the chlorogenic acid can be tightly combined with an LPS site of an outer membrane of gram-negative bacteria through electrostatic interaction, Mg < 2 + > ions are chelated, the stability of a bacterial membrane is destroyed, the permeability of a cell membrane is increased, and finally, the bacteria gradually die.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to an antibacterial packaging film for Chinese herbal medicine and a preparation method thereof. Background Art

[0002] With the continuous improvement of the quality of life, people pay more and more attention to the safety performance of food packaging materials, which requires film materials to have certain antibacterial properties. Polyurethane is a commonly used film material in the field of food packaging; but the antibacterial properties of polyurethane itself are not ideal. Therefore, the current research focuses on developing a polyurethane film material that can resist different fungi to meet the diverse needs of different fields.

[0003] Chlorogenic acid (CA) is derived from Chinese herbal medicine and is a phenolic compound found in coffee beans. Its molecular chain contains a large number of phenolic hydroxyl groups and benzene rings, which provide active groups for chemical modification. CA has good biocompatibility and is non-toxic, so it can be used as an important raw material for chemical synthesis. In addition, because CA can change the permeability of cell membranes, it has antibacterial activity against a variety of microorganisms, including bacteria, yeast, and mold. A large number of studies have shown that chlorogenic acid also has antioxidant effects.

[0004] However, there is no report on the use of chlorogenic acid in the preparation of antibacterial polyurethane films. Summary of the invention

[0005] In order to overcome at least one of the technical problems existing in the prior art, the present invention provides an antibacterial packaging film for Chinese herbal medicine and a preparation method thereof.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention first provides a method for preparing an antibacterial packaging film of Chinese herbal medicine, which comprises the following steps:

[0008] (1) heating and stirring polyethylene glycol and chlorogenic acid powder in a solvent to mix evenly to obtain a polyol system;

[0009] (2) Adding dicyclohexylmethane 4,4'-diisocyanate solution to the polyol system, and continuing to heat and stir under the action of a catalyst, after the reaction is completed, casting onto a template, standing to remove bubbles, and drying to obtain a Chinese herbal antibacterial film.

[0010] Preferably, in step (1), the weight ratio of polyethylene glycol to chlorogenic acid powder is 94-98:2-6.

[0011] Preferably, the polyethylene glycol in step (1) is polyethylene glycol 200.

[0012] Preferably, the heating and stirring in step (1) specifically refers to heating and stirring under a nitrogen environment.

[0013] Preferably, the heating and stirring in step (1) refers to stirring the reaction at 60-70° C. for 1-2 h.

[0014] Preferably, in step (2), the molar ratio of hydroxyl groups in the polyol system to isocyanate bonds in dicyclohexylmethane 4,4'-diisocyanate is 1:1.

[0015] Preferably, the amount of catalyst added in step (2) is 0.1 to 1.5% of the total mass of hydroxyl groups in the composition.

[0016] Preferably, the heating and stirring in step (2) specifically refers to stirring the reaction at 60-70° C. for 3-6 hours.

[0017] Most preferably, the heating and stirring in step (2) specifically refers to stirring the reaction at 65° C. for 4 h.

[0018] Preferably, the drying in step (2) specifically refers to drying at 60-70° C. for 8-12 hours.

[0019] Most preferably, the drying in step (2) specifically refers to drying at 65° C. for 10 h.

[0020] The present invention also provides a Chinese herbal medicine antibacterial packaging film prepared by the above preparation method.

[0021] Beneficial effects: The present invention provides a new method for preparing a Chinese herbal medicine antibacterial packaging film; studies have shown that the Chinese herbal medicine antibacterial packaging film prepared by the method of the present invention has good antibacterial properties; this is because the surface of chlorogenic acid has a negative charge, which can be tightly bound to the LPS site of the outer membrane of Gram-negative bacteria through electrostatic interaction, chelating Mg 2+ ions, thereby destroying the stability of the bacterial membrane, increasing the permeability of the cell membrane, and ultimately leading to the gradual death of the bacteria. In addition, chlorogenic acid also has the ability to destroy the integrity of the bacterial cell wall and can have a significant effect on the membrane permeability of Gram-positive bacteria, thereby achieving the purpose of antibacterial. DETAILED DESCRIPTION

[0022] The present invention is further explained below in conjunction with specific examples, but the examples do not limit the present invention in any form.

[0023] Example 1 Preparation of Chinese herbal medicine antibacterial packaging film

[0024] (1) Accurately weigh 2.96 g of polyethylene glycol 200 and 0.2024 g of chlorogenic acid powder after grinding uniformly using an electronic analytical balance, pour them into a round-bottom flask containing 2 mL of tetrahydrofuran, place them in a constant temperature oil bath, stir at 65° C. under a nitrogen atmosphere until completely dissolved, and react for 1 hour, wherein the stirring speed is 2000 r / min. After the reaction is completed, a polyol system is obtained; accurately weigh 3.747 g of dicyclohexylmethane 4,4'-diisocyanate solution using an electronic analytical balance, add it to the polyol system, stir for 5 minutes, and then drop 50 μL of dibutyltin dilaurate catalyst into the above solution, and then react at 65° C. for 4 hours, wherein the stirring speed is 2000 r / min. During this period, an appropriate tetrahydrofuran solvent is added according to the reaction viscosity of the system so that the final concentration of the polyurethane is 30% of the weight of tetrahydrofuran. After the reaction is completed, a film-forming liquid is obtained;

[0025] (2) The film-forming liquid is cast on a polytetrafluoroethylene template by a tape-casting method and placed at room temperature for 12 hours. After the solvent evaporates, the template is placed in a vacuum drying oven at a drying temperature of 65° C. and dried for 10 hours to form a film, thereby obtaining the Chinese herbal medicine antibacterial packaging film.

[0026] Example 2 Preparation of Chinese herbal medicine antibacterial packaging film

[0027] (1) Accurately weigh 2.90 g of polyethylene glycol 200 and 0.4048 g of chlorogenic acid powder after grinding uniformly using an electronic analytical balance, pour them into a round-bottom flask containing 2 mL of tetrahydrofuran, place them in a constant temperature oil bath, stir at 65° C. under a nitrogen atmosphere until completely dissolved, and react for 1 hour, wherein the stirring speed is 2000 r / min. After the reaction is completed, a polyol system is obtained; accurately weigh 3.747 g of dicyclohexylmethane 4,4'-diisocyanate solution using an electronic analytical balance, add it to the polyol system, stir for 5 minutes, and then drop 50 μL of dibutyltin dilaurate catalyst into the above solution, and then react at 65° C. for 4 hours, wherein the stirring speed is 2000 r / min. During this period, an appropriate tetrahydrofuran solvent is added according to the reaction viscosity of the system so that the final concentration of the polyurethane is 30% of the weight of tetrahydrofuran. After the reaction is completed, a film-forming liquid is obtained;

[0028] (2) The film-forming liquid is cast on a polytetrafluoroethylene template by a tape-casting method and placed at room temperature for 12 hours. After the solvent evaporates, the template is placed in a vacuum drying oven at a drying temperature of 65° C. and dried for 10 hours to form a film, thereby obtaining the Chinese herbal medicine antibacterial packaging film.

[0029] Example 3 Preparation of Chinese herbal medicine antibacterial packaging film

[0030] (1) Accurately weigh 2.84 g of polyethylene glycol 200 and 0.6072 g of chlorogenic acid powder after grinding uniformly using an electronic analytical balance, pour them into a round-bottom flask containing 2 mL of tetrahydrofuran, place them in a constant temperature oil bath, stir at 65° C. under a nitrogen atmosphere until completely dissolved, and react for 1 hour at a stirring speed of 2000 r / min. After the reaction is completed, a polyol system is obtained; accurately weigh 3.747 g of dicyclohexylmethane 4,4'-diisocyanate solution using an electronic analytical balance, add it to the polyol system, stir for 5 minutes, and then drop 50 μL of dibutyltin dilaurate catalyst into the above solution, and then react at 65° C. for 4 hours at a stirring speed of 2000 r / min. During this period, an appropriate tetrahydrofuran solvent is added according to the reaction viscosity of the system so that the final concentration of the polyurethane is 30% of the weight of tetrahydrofuran. After the reaction is completed, a film-forming liquid is obtained;

[0031] (2) The film-forming liquid is cast on a polytetrafluoroethylene template by a tape-casting method and placed at room temperature for 12 hours. After the solvent evaporates, the template is placed in a vacuum drying oven at a drying temperature of 65° C. and dried for 10 hours to form a film, thereby obtaining the Chinese herbal medicine antibacterial packaging film.

[0032]

Determination of antibacterial properties

[0033] According to the QB / T 2591-2003 test standard, the antibacterial ability of the Chinese herbal medicine antibacterial packaging films prepared in Examples 1 to 3 was tested. First, the Chinese herbal medicine antibacterial packaging films to be tested were cut into 20×20 mm pieces and sterilized with ultraviolet light for 30 minutes. Then, the bacterial solution was diluted to a film concentration of 10 with phosphate buffered saline (PBS). 6 CFU / mL, and then 200 μL of bacterial solution was added to the surface of the antibacterial packaging film of the Chinese herbal medicine to be tested, and covered with a 10×10 mm polypropylene film that does not react with the bacterial solution. After co-culture for 10 hours, the co-culture solution was diluted to 10 with PBS. 4 CFU / mL. The bacterial solution that was not co-cultured but covered with a membrane was used as a control, and 40 μL of the bacterial solution was spread on the agar plate with a coating stick and incubated at 37°C. Within 12 hours, the colonies of different samples were recorded using a camera. In parallel with more than 3 groups, the colony growth of each sample was observed. The antibacterial rate (AR) was calculated according to the following formula.

[0034] AR (%) = (1-D sample / D control ) × 100 %

[0035] Where: AR is the antibacterial rate of the composite film, %; D sample is the number of colonies in the experimental group; D control is the number of colonies in the blank group;

[0036] The results showed that with the increase of the amount of chlorogenic acid introduced, the antibacterial properties of the obtained film material were significantly improved; among them, the antibacterial rate of the Chinese herbal antibacterial packaging film prepared in Example 3 against Escherichia coli (E.Coli) and Staphylococcus aureus (S.Aureus) was most significantly improved, increasing to 99.53% and 93.33% respectively, indicating that the Chinese herbal antibacterial packaging film prepared by the present invention has excellent antibacterial properties.

[0037] Chlorogenic acid (CA) has stronger antibacterial activity against Gram-negative bacteria than Gram-positive bacteria. Since the outer membrane of Gram-negative bacteria contains lipopolysaccharide (LPS) and protein, they bind to divalent cations and maintain the stability of the bacterial structure through electrostatic interaction. However, the surface of chlorogenic acid molecules carries a negative charge, which can tightly bind to the LPS site through electrostatic interaction and chelate divalent cations, thereby destroying the stability of the outer membrane of Gram-negative bacteria, increasing the permeability of the cell membrane, and further affecting the overall stability of the cell structure, ultimately leading to the gradual death of bacteria. In addition, chlorogenic acid also has the ability to destroy the integrity of bacterial cell walls and can have a significant effect on the membrane permeability of Gram-positive bacteria. When chlorogenic acid penetrates into the bacterial cell wall, it can interfere with the synthesis process of the cell wall, causing cracks or holes in the cell wall, which in turn causes the substances inside the bacteria to leak out, destroying the life activities of the bacteria, thereby achieving the purpose of antibacterial.

Claims

1. A method for preparing a Chinese herbal medicine antibacterial packaging film, characterized in that: The following steps are included: (1) heating and stirring polyethylene glycol and chlorogenic acid powder in a solvent to mix evenly to obtain a polyol system; (2) Adding dicyclohexylmethane 4,4'-diisocyanate solution to the polyol system, and continuing to heat and stir under the action of a catalyst, after the reaction is completed, casting onto a template, standing to remove bubbles, and drying to obtain a Chinese herbal antibacterial film.

2. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: In step (1), the weight ratio of polyethylene glycol to chlorogenic acid powder is 94-98:2-6.

3. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: The polyethylene glycol in step (1) is polyethylene glycol 200.

4. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: The heating and stirring in step (1) specifically refers to heating and stirring under a nitrogen environment.

5. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: The heating and stirring in step (1) refers to stirring the reaction at 60-70° C. for 1-2 h.

6. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: In step (2), the molar ratio of the hydroxyl group in the polyol system to the isocyanate bond in dicyclohexylmethane 4,4'-diisocyanate is 1:

1.

7. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: The amount of the catalyst added in step (2) is 0.1 to 1.5% of the total mass of hydroxyl groups in the composition.

8. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: The heating and stirring in step (2) specifically refers to stirring the reaction at 60-70° C. for 3-6 hours. Most preferably, the heating and stirring in step (2) specifically refers to stirring the reaction at 65° C. for 4 h.

9. The method for preparing the antibacterial packaging film of Chinese herbal medicine according to claim 1, characterized in that: The drying described in step (2) specifically refers to drying at 60-70° C. for 8-12 hours. Most preferably, the drying in step (2) specifically refers to drying at 65° C. for 10 h.

10. The antibacterial packaging film of Chinese herbal medicine prepared by the preparation method according to any one of claims 1 to 9.