Thiol group-containing thiolated chitosan quaternary ammonium salt as well as preparation method and application thereof

Abstract

The invention relates to the technical field of marine chemical engineering, in particular to thiolated chitosan quaternary ammonium salt containing thiophene groups as well as a preparation method and application of the thiolated chitosan quaternary ammonium salt. The thiolated chitosan quaternary ammonium salt containing the thiophene group has a structure as shown in a formula I in the specification. The preparation method comprises the following steps: further reacting sulfhydrylated chitosan to obtain sulfhydrylated chitosan quaternary ammonium salt, and further introducing thiophene groups into the chitosan quaternary ammonium salt by taking the sulfhydrylated chitosan quaternary ammonium salt as a reaction raw material. Antioxidant activity experiments prove that the obtained thiolated chitosan quaternary ammonium salt derivative has good antioxidant activity, and can be widely researched and applied as an antioxidant in the fields of biological medicine, agriculture and the like. And the # imgabs0 # is shown in the formula 1.

Description

Technical Field

[0001] The invention relates to the technical field of marine chemical engineering, and in particular to a thiolated chitosan quaternary ammonium salt containing a thiophene group, and a preparation method and application thereof. Background Art

[0002] Chitosan is obtained by deacetylation of chitin, and its degree of deacetylation is generally 60-100%. Compared with chitin, chitosan has non-toxicity, biocompatibility, good antioxidant activity and antibacterial activity. At the same time, chitosan also has the advantages of large output and low price. However, the poor solubility of chitosan in aqueous solution has greatly limited its research and utilization. Summary of the invention

[0003] The purpose of the present invention is to provide a thiolated chitosan quaternary ammonium salt containing a thiophene group and a preparation method and application thereof.

[0004] To achieve the above object, the technical solution adopted by the present invention is: A thiolated chitosan quaternary ammonium salt containing a thiophene group, the structural formula of the thiolated chitosan quaternary ammonium salt containing a thiophene group is as follows: Formula 1, R is thiophene which is unsubstituted or substituted with at least one C1-C6 alkyl group; Among them, the average value range of n is 35-3000.

[0005] Preferably, in the formula 1, R= , , , , ; The average value range of n is 35-3000.

[0006] A method for preparing the thiolated chitosan quaternary ammonium salt containing thiophene groups, the reaction formula is: ; First, chitosan is thiolated to obtain thiolated chitosan; then the thiolated chitosan is reacted with 2,3-epoxypropyltrimethylammonium chloride to obtain thiolated chitosan quaternary ammonium salt; finally, the thiolated chitosan quaternary ammonium salt is ion exchanged with a compound containing a thiophene group to obtain a thiolated chitosan quaternary ammonium salt containing a thiophene group.

[0007] Preferably, (1) Dissolve chitosan in 1% acetic acid solution, add thiourea-containing hydrochloric acid solution dropwise to the mixed solution, adjust the pH value of the mixed solution with sodium hydroxide solution, and the pH test paper shows that the pH value of the mixed solution is 4-5. Use microwave reaction to carry out substitution reaction on the mixture to obtain thiolated chitosan; (2) dissolving the thiolated chitosan in isopropanol to obtain a mixed solution, adding an aqueous solution of 2,3-epoxypropyltrimethylammonium chloride dropwise to the mixed solution, reacting in a 75° C. water bath, dialyzing the product for 48 h, and vacuum freeze-drying to obtain a thiolated chitosan quaternary ammonium salt; (3) Dissolving the thiolated chitosan quaternary ammonium salt in water, and adding a neutral aqueous solution of a compound containing a thiophene group dropwise into the aqueous solution to carry out an ion exchange reaction, thereby finally obtaining the thiolated chitosan quaternary ammonium salt containing a thiophene group as shown in Formula 1.

[0008] In the step (1), for every 2-4 g of chitosan, 2-4.5 g of thiourea and 3-6 mL of hydrochloric acid are used; the reaction power of the microwave reactor is 640 W, and the reaction time is 2 min; the product after the reaction is precipitated with anhydrous ethanol, and washed three times to finally obtain thiolated chitosan.

[0009] In the step (2), 4.5-9 g of 2,3-epoxypropyltrimethylammonium chloride is added to every 1.5-3.5 g of thiolated chitosan, and the mixture is reacted in a water bath at 75° C. for 10 h.

[0010] In the step (3), 1.1-3.1 g of the thiophene group-containing compound is added to every 1-1.5 g of the thiolated chitosan quaternary ammonium salt.

[0011] A method for preparing the thiolated chitosan quaternary ammonium salt containing thiophene groups, and application of the thiolated chitosan quaternary ammonium salt containing thiophene groups as shown in formula 1 in preparing antioxidants in the fields of biomedicine or agriculture.

[0012] Compared with the prior art, the beneficial technical effects of the present invention are as follows: (1) The water solubility of the thiolated chitosan quaternary ammonium salt obtained by chemical modification in the present invention is improved compared with chitosan, which solves the difficulties of chitosan being difficult to dissolve in water and difficult to apply, and expands the application range of chitosan.

[0013] (2) The preparation steps of thiolated chitosan quaternary ammonium salt are simple, no by-products are produced, the purification method is simple, and there is no obvious cytotoxicity, which provides a practical path to further expand the application range of chitosan. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the infrared spectrum of chitosan.

[0015] Figure 2 This is the infrared spectrum of thiolated chitosan.

[0016] Figure 3 This is the infrared spectrum of thiolated chitosan quaternary ammonium salt.

[0017] Figure 4This is the infrared spectrum of the quaternary ammonium salt of thiolated chitosan containing 2-thiophenecarboxylic acid in Example 1 of the present invention.

[0018] Figure 5 This is the infrared spectrum of the quaternary ammonium salt of thiolated chitosan containing 3-thiophenecarboxylic acid in Example 2 of the present invention.

[0019] Figure 6 This is the infrared spectrum of the thiolated chitosan quaternary ammonium salt containing 3-methyl-2-thiophenecarboxylic acid in Example 3 of the present invention.

[0020] Figure 7 This is the infrared spectrum of the thiolated chitosan quaternary ammonium salt containing 4-methyl-2-thiophenecarboxylic acid in Example 4 of the present invention.

[0021] Figure 8 This is the infrared spectrum of the thiolated chitosan quaternary ammonium salt containing 5-methyl-2-thiophenecarboxylic acid in Example 5 of the present invention. DETAILED DESCRIPTION

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

[0023] The present invention chemically modifies the amino and hydroxyl sites of chitosan and introduces thiol groups and thiophene groups into chitosan, so that the chitosan derivatives have good water solubility and significantly improve the antioxidant activity.

[0024] Example 1 Formula (1) The structural formula of the thiolated chitosan quaternary ammonium salt containing 2-thiophenecarboxylic acid is shown in formula (1), wherein the average value range of n is 35-3000.

[0025] Preparation of thiolated chitosan quaternary ammonium salt containing 2-thiophenecarboxylic acid: Weigh chitosan (1 g, deacetylation degree > 90%, MW = 8000, see Figure 1 ) was added with acetic acid solution (50 mL, volume fraction 1%) and stirred to dissolve to obtain solution a. Thiourea (1.1 g) was weighed and dissolved in hydrochloric acid solution (3 mL, the volume ratio of concentrated hydrochloric acid to water was 1:1) to obtain solution b, which was added dropwise to solution a. The mixed solution was adjusted with sodium hydroxide solution. The pH test paper showed that the pH of the mixed solution was 4-5. The microwave reaction was carried out at a power of 640 W for 2 min. The reaction product was precipitated with anhydrous ethanol, washed three times, vacuum-dried, and ground to obtain thiolated chitosan (see Figure 2 ).

[0026] Weigh thiolated chitosan (1.77 g) and add isopropanol (40 mL). Stir and disperse in a 55°C water bath for 2 h to obtain solution c. Weigh 2,3-epoxypropyltrimethylammonium chloride (4.53 g) and add deionized water (5 mL) to dissolve to obtain solution d. Add solution d dropwise into solution c, increase the water bath temperature to 75°C, and reflux for 12 h. Dialyze the product for 48 h and freeze-dry in vacuum to obtain thiolated chitosan quaternary ammonium salt (see Figure 3 ).

[0027] Take 2-thiophenecarboxylic acid (1.153 g) and add deionized water (50 mL). Add sodium hydroxide to adjust the pH to neutral and stir until the solid is completely dissolved to obtain solution e. Take thiolated chitosan quaternary ammonium salt (0.984 g) and add deionized water (20 mL) to completely dissolve to obtain solution f. Add solution f dropwise to solution e, react at room temperature for 48 hours, and freeze-dry in vacuum to obtain thiolated chitosan quaternary ammonium salt containing 2-thiophenecarboxylic acid.

[0028] Figure 4 This is the infrared spectrum of the quaternary ammonium salt of thiolated chitosan containing 2-thiophenecarboxylic acid in Example 1 of the present invention, at 1478 cm -1 The vibration absorption peak of quaternary ammonium salt appears at 1420cm -1 The vibration absorption peak of the thiophene ring appeared at , which proved that the quaternary ammonium salt of thiolated chitosan containing 2-thiophenecarboxylic acid was successfully synthesized.

[0029] Example 2 Formula (2) The structural formula of the thiolated chitosan quaternary ammonium salt containing 3-thiophenecarboxylic acid is shown in formula (2), wherein the average value range of n is 35-3000.

[0030] The difference from Example 1 is that: Preparation of thiolated chitosan quaternary ammonium salt containing 3-thiophenecarboxylic acid: Weigh chitosan (1 g, deacetylation degree > 90%, MW = 8000, see Figure 1 ) was added with acetic acid solution (50 mL, volume fraction 1%) and stirred to dissolve to obtain solution a. Thiourea (1.1 g) was weighed and dissolved in hydrochloric acid solution (3 mL, the volume ratio of concentrated hydrochloric acid to water was 1:1) to obtain solution b, which was added dropwise to solution a. The mixed solution was adjusted with sodium hydroxide solution. The pH test paper showed that the pH of the mixed solution was 4-5. The microwave reaction was carried out at a power of 640 W for 2 min. The reaction product was precipitated with anhydrous ethanol, washed three times, vacuum-dried, and ground to obtain thiolated chitosan (see Figure 2 ).

[0031] Weigh thiolated chitosan (1.77 g) and add isopropanol (40 mL). Stir and disperse in a 55°C water bath for 2 h to obtain solution c. Weigh 2,3-epoxypropyltrimethylammonium chloride (4.53 g) and add deionized water (5 mL) to dissolve to obtain solution d. Add solution d dropwise into solution c, increase the water bath temperature to 75°C, and reflux for 12 h. Dialyze the product for 48 h and freeze-dry in vacuum to obtain thiolated chitosan quaternary ammonium salt (see Figure 3 ).

[0032] 3-Thiophenecarboxylic acid (1.153 g) was added to deionized water (50 mL), and sodium hydroxide was added thereto to adjust the pH to neutral, and the mixture was stirred until the solid was completely dissolved to obtain solution e. Thiolated chitosan quaternary ammonium salt (0.984 g) was added to deionized water (20 mL) and completely dissolved to obtain solution f. Solution f was added dropwise to solution e, and the mixture was reacted at room temperature for 48 h, and then freeze-dried in vacuum to obtain thiolated chitosan quaternary ammonium salt containing 3-thiophenecarboxylic acid.

[0033] Figure 5 This is the infrared spectrum of the quaternary ammonium salt of thiolated chitosan containing 3-thiophenecarboxylic acid in Example 2 of the present invention, at 1478 cm -1 The vibration absorption peak of quaternary ammonium salt appears at 1411cm -1 The vibration absorption peak of the thiophene ring appeared at , which proved that the quaternary ammonium salt of thiolated chitosan containing 3-thiophenecarboxylic acid was successfully synthesized.

[0034] Example 3 Formula (3) The structural formula of the thiolated chitosan quaternary ammonium salt containing 3-methyl-2-thiophenecarboxylic acid is shown in formula (3), wherein the average value range of n is 35-3000.

[0035] The difference from Example 1 is that: Preparation of thiolated chitosan quaternary ammonium salt containing 3-methyl-2-thiophenecarboxylic acid: Weigh chitosan (1 g, deacetylation degree > 90%, MW = 8000, see Figure 1 ) was added with acetic acid solution (50 mL, volume fraction 1%) and stirred to dissolve to obtain solution a. Thiourea (1.1 g) was weighed and dissolved in hydrochloric acid solution (3 mL, volume ratio of concentrated hydrochloric acid to water was 1:1) to obtain solution b, which was added dropwise to solution a. The mixed solution was adjusted with sodium hydroxide solution. The pH test paper showed that the pH of the mixed solution was 4-5. The microwave reaction was carried out at a power of 640 W for 2 min. The reaction product was precipitated with anhydrous ethanol, washed three times, vacuum-dried, and ground to obtain thiolated chitosan (see Figure 2 ).

[0036] Weigh thiolated chitosan (1.77 g) and add isopropanol (40 mL). Stir and disperse in a 55°C water bath for 2 h to obtain solution c. Weigh 2,3-epoxypropyltrimethylammonium chloride (4.53 g) and add deionized water (5 mL) to dissolve to obtain solution d. Add solution d dropwise into solution c, increase the water bath temperature to 75°C, and reflux for 12 h. Dialyze the product for 48 h and freeze-dry in vacuum to obtain thiolated chitosan quaternary ammonium salt (see Figure 3 ).

[0037] 3-Methyl-2-thiophenecarboxylic acid (1.279 g) was added to deionized water (50 mL), and sodium hydroxide was added thereto to adjust the pH to neutral, and the mixture was stirred until the solid was completely dissolved to obtain solution e. Thiolated chitosan quaternary ammonium salt (0.984 g) was added to deionized water (20 mL) and completely dissolved to obtain solution f. Solution f was added dropwise to solution e, and the mixture was reacted at room temperature for 48 h, and then vacuum-dried to obtain thiolated chitosan quaternary ammonium salt containing 3-methyl-2-thiophenecarboxylic acid.

[0038] Figure 6 This is the infrared spectrum of the quaternary ammonium salt of thiolated chitosan containing 3-methyl-2-thiophenecarboxylic acid in Example 3 of the present invention, at 1478 cm -1 The vibration absorption peak of quaternary ammonium salt appears at 1416cm -1 The vibration absorption peak of the thiophene ring appeared at , which proved that the thiolated chitosan quaternary ammonium salt containing 3-methyl-2-thiophenecarboxylic acid was successfully synthesized.

[0039] Example 4 Formula (4) The structural formula of the thiolated chitosan quaternary ammonium salt containing 4-methyl-2-thiophenecarboxylic acid is shown in formula (4), wherein the average value range of n is 35-3000.

[0040] The difference from Example 1 is that: Preparation of thiolated chitosan quaternary ammonium salt containing 4-methyl-2-thiophenecarboxylic acid: Weigh chitosan (1 g, deacetylation degree > 90%, MW = 8000, see Figure 1 ) was added with acetic acid solution (50 mL, volume fraction 1%) and stirred to dissolve to obtain solution a. Thiourea (1.1 g) was weighed and dissolved in hydrochloric acid solution (3 mL, volume ratio of concentrated hydrochloric acid to water was 1:1) to obtain solution b, which was added dropwise to solution a. The mixed solution was adjusted with sodium hydroxide solution. The pH test paper showed that the pH of the mixed solution was 4-5. The microwave reaction was carried out at a power of 640 W for 2 min. The reaction product was precipitated with anhydrous ethanol, washed three times, vacuum-dried, and ground to obtain thiolated chitosan (see Figure 2 ).

[0041] Weigh thiolated chitosan (1.77 g) and add isopropanol (40 mL). Stir and disperse in a 55°C water bath for 2 h to obtain solution c. Weigh 2,3-epoxypropyltrimethylammonium chloride (4.53 g) and add deionized water (5 mL) to dissolve to obtain solution d. Add solution d dropwise into solution c, increase the water bath temperature to 75°C, and reflux for 12 h. Dialyze the product for 48 h and freeze-dry in vacuum to obtain thiolated chitosan quaternary ammonium salt (see Figure 3 ).

[0042] 4-Methyl-2-thiophenecarboxylic acid (1.279 g) was added to deionized water (50 mL), and sodium hydroxide was added thereto to adjust the pH to neutral, and the mixture was stirred until the solid was completely dissolved to obtain solution e. Thiolated chitosan quaternary ammonium salt (0.984 g) was added to deionized water (20 mL) and completely dissolved to obtain solution f. Solution f was added dropwise to solution e, and the mixture was reacted at room temperature for 48 h, and then vacuum-dried to obtain thiolated chitosan quaternary ammonium salt containing 4-methyl-2-thiophenecarboxylic acid.

[0043] Figure 7 This is the infrared spectrum of the quaternary ammonium salt of thiolated chitosan containing 4-methyl-2-thiophenecarboxylic acid in Example 4 of the present invention, at 1471 cm -1 The vibration absorption peak of quaternary ammonium salt appears at 1430cm -1 The vibration absorption peak of the thiophene ring appeared at , which proved that the thiolated chitosan quaternary ammonium salt containing 4-methyl-2-thiophenecarboxylic acid was successfully synthesized.

[0044] Example 5 Formula (5) The structural formula of the thiolated chitosan quaternary ammonium salt containing 5-methyl-2-thiophenecarboxylic acid is shown in formula (5), wherein the average value range of n is 35-3000.

[0045] The difference from Example 1 is that: Preparation of thiolated chitosan quaternary ammonium salt containing 5-methyl-2-thiophenecarboxylic acid: Weigh chitosan (1 g, deacetylation degree > 90%, MW = 8000, see Figure 1 ) was added with acetic acid solution (50 mL, volume fraction 1%) and stirred to dissolve to obtain solution a. Thiourea (1.1 g) was weighed and dissolved in hydrochloric acid solution (3 mL, volume ratio of concentrated hydrochloric acid to water was 1:1) to obtain solution b, which was added dropwise to solution a. The mixed solution was adjusted with sodium hydroxide solution. The pH test paper showed that the pH of the mixed solution was 4-5. The microwave reaction was carried out at a power of 640 W for 2 min. The reaction product was precipitated with anhydrous ethanol, washed three times, vacuum freeze-dried, and ground to obtain thiolated chitosan (see Figure 2 ).

[0046] Weigh thiolated chitosan (1.77 g) and add isopropanol (40 mL). Stir and disperse in a 55°C water bath for 2 h to obtain solution c. Weigh 2,3-epoxypropyltrimethylammonium chloride (4.53 g) and add deionized water (5 mL) to dissolve to obtain solution d. Add solution d dropwise into solution c, increase the water bath temperature to 75°C, and reflux for 12 h. Dialyze the product for 48 h and freeze-dry in vacuum to obtain thiolated chitosan quaternary ammonium salt (see Figure 3 ).

[0047] 5-methyl-2-thiophenecarboxylic acid (1.279 g) was added to deionized water (50 mL), and sodium hydroxide was added thereto to adjust the pH to neutral, and the mixture was stirred until the solid was completely dissolved to obtain solution e. Thiolated chitosan quaternary ammonium salt (0.984 g) was added to deionized water (20 mL) and completely dissolved to obtain solution f. Solution f was added dropwise to solution e, and the mixture was reacted at room temperature for 48 h, and then vacuum-dried to obtain thiolated chitosan quaternary ammonium salt containing 5-methyl-2-thiophenecarboxylic acid.

[0048] Figure 8 This is the infrared spectrum of the quaternary ammonium salt of thiolated chitosan containing 5-methyl-2-thiophenecarboxylic acid in Example 5 of the present invention, at 1477 cm -1 The vibration absorption peak of quaternary ammonium salt appears at 1464cm -1 The vibration absorption peak of the thiophene ring appeared at , which proved that the thiolated chitosan quaternary ammonium salt containing 5-methyl-2-thiophenecarboxylic acid was successfully synthesized.

[0049] Application Examples Antioxidant activity assay (1) Determination of DPPH radical scavenging ability: The thiolated chitosan quaternary ammonium salt containing thiophene groups prepared in the above examples were subjected to DPPH radical scavenging ability determination and comparison. Chitosan, the thiolated chitosan quaternary ammonium salt obtained in Example 1 and the thiolated chitosan quaternary ammonium salt derivative containing thiophene groups obtained above were taken respectively, and two groups (experimental group and control group) of test solutions with concentration gradients of 0.1, 0.2, 0.4, 0.8 and 1.6 mg / mL were prepared in EP tubes, each with 1 mL. Deionized water (1 mL) was added to the blank group instead of the sample solution. An ethanol solution of 1,1-diphenyl-2-trinitrobenzene was prepared, 1,1-diphenyl-2-trinitrobenzene (DPPH, 35.5 mg) was taken and added to anhydrous ethanol to fully dissolve, and the volume was fixed to obtain a DPPH-ethanol solution (500 mL). DPPH-ethanol solution (2 mL) was added to each EP tube in the experimental group. At the same time, anhydrous ethanol (2 mL) was added to the control group, and DPPH-ethanol solution (2 mL) was added to the blank group. After all samples were mixed evenly, they were placed in a dark place at room temperature for 20 minutes. The absorbance of each group of samples was tested at 517 nm using an ultraviolet spectrophotometer. Each group was tested three times, and the results were averaged. The calculation formula for the DPPH free radical scavenging ability of the sample is as follows: Clearance rate (%) = [1-(A 实验 -A 对照 ) / A 空白 ]×100 Among them, A 实验 Represents the absorbance of the experimental group; A 对照 represents the absorbance of the control group; A 空白 Represents the absorbance of the blank group.

[0050] The results of the DPPH free radical scavenging ability test are shown in Table 1.

[0051] Table 1 DPPH free radical scavenging ability of test samples (%)

[0052] (2) Determination of hydroxyl radical scavenging ability: The hydroxyl radical scavenging ability of the thiolated chitosan quaternary ammonium salt containing thiophene groups prepared in the above examples was determined and compared. Chitosan, the thiolated chitosan quaternary ammonium salt obtained in Example 1 above, and the thiolated chitosan quaternary ammonium salt derivative containing thiophene groups were taken respectively, and 1 mL of the test solution with a concentration gradient of 0.1, 0.2, 0.4, 0.8, and 1.6 mg / mL was prepared in an EP tube. Deionized water (1 mL) was added to the control group and the blank group instead of the sample solution. Phosphate buffer (500 mL, containing 20.79 g disodium hydrogen phosphate dodecahydrate, 2.64 g sodium dihydrogen phosphate dihydrate, made up to volume with water), EDTA-Fe 2+Solution (100mL, ferrous sulfate heptahydrate 0.0556g, ethylenediaminetetraacetic acid disodium 0.1489g, water to volume), saffron T solution (100mL, saffron T 0.036g, phosphate buffer to volume), hydrogen peroxide solution (100mL, 30% H2O2 10mL, phosphate buffer to volume). Add EDTA-Fe to the three sets of EP tubes in turn. 2+ Solution (0.5mL), phosphate buffer (1mL), saffron T solution (1mL), hydrogen peroxide solution (1mL). The control group used phosphate buffer instead of hydrogen peroxide solution. After all samples were mixed evenly, they were heated to make them fade, and the blank group was stopped when it was completely faded. The absorbance of each group of samples was tested at 520n using a UV spectrophotometer. Each group was tested three times and the results were averaged. The formula for calculating the hydroxyl radical scavenging ability of the sample is as follows: Clearance rate (%) = [(A 实验 -A 空白 ) / (A 对照 -A 空白） ]×100 Among them, Aexperiment represents the absorbance of the experimental group; Acontrol represents the absorbance of the control group; Ablank represents the absorbance of the blank group.

[0053] The results of the hydroxyl radical scavenging ability test are shown in Table 2.

[0054] Table 2 Hydroxyl radical scavenging ability of test samples (%)

[0055] (3) Determination of reducing ability: The reducing ability of the thiolated chitosan quaternary ammonium salt containing thiophene groups prepared in the above examples was determined and compared. Chitosan, thiolated chitosan quaternary ammonium salt and thiolated chitosan quaternary ammonium salt derivative containing thiophene groups were taken respectively, and 0.5 mL of the test solution with a concentration gradient of 0.1, 0.2, 0.4, 0.8, and 1.6 mg / mL was prepared in an EP tube. Phosphate buffer (250 mL, 6.24 g of disodium hydrogen phosphate dihydrate, 3.58 g of sodium dihydrogen phosphate dodecahydrate, fixed to volume with water), potassium ferrocyanide solution (50 mL, 0.5 g of potassium ferrocyanide, fixed to volume with phosphate buffer), trichloroacetic acid solution (50 mL, 5 g of trichloroacetic acid, fixed to volume with phosphate buffer), and ferric chloride solution (50 mL, 0.05 g of ferric chloride, fixed to volume with phosphate buffer) were prepared. Potassium ferrocyanide solution (0.5 mL) and trichloroacetic acid solution (0.5 mL) were added to the sample in sequence. Take the supernatant (0.75 mL) and add water (0.6 mL) and ferric chloride solution (0.15 mL). Use a UV spectrophotometer to test the absorbance of each group of samples at 700 nm. Repeat the test three times for each group and take the average value of the results.

[0056] The results of the reduction ability test are shown in Table 3.

[0057] Table 3 Reducing ability of test samples (%)

[0058] The results show that the invention introduces active groups such as thiol groups, thiophene groups and quaternary ammonium salts into chitosan, which can significantly improve the antioxidant activity of the derivatives. At the same time, the chitosan derivatives have good water solubility, which proves that the thiolated chitosan quaternary ammonium salt containing thiophene groups has broad application prospects in the fields of medical medicine, agriculture, etc.

Claims

1. A thiolated chitosan quaternary ammonium salt containing a thiophene group, characterized in that: The structural formula of the thiolated chitosan quaternary ammonium salt containing thiophene group is as follows: , R is thiophene which is unsubstituted or substituted with at least one C1-C6 alkyl group; Among them, the average value range of n is 35-3000.

2. The thiophene-containing thiolated chitosan quaternary ammonium salt according to claim 1, characterized in that: In the structural formula, R= , , , , ; The average value range of n is 35-3000.

3. A method for preparing the thiolated chitosan quaternary ammonium salt containing thiophene groups according to claim 1, characterized in that: The reaction formula is ; Firstly, chitosan is subjected to thiolation substitution to obtain thiolated chitosan; then, the thiolated chitosan is reacted with 2,3-epoxypropyltrimethylammonium chloride to obtain thiolated chitosan quaternary ammonium salt; finally, the thiolated chitosan quaternary ammonium salt is subjected to ion exchange with a compound containing a thiophene group to obtain a thiolated chitosan quaternary ammonium salt containing a thiophene group.

4. The method for preparing the thiolated chitosan quaternary ammonium salt containing thiophene groups according to claim 3, characterized in that: (1) Dissolving chitosan in 1% acetic acid solution, adding thiourea-containing hydrochloric acid solution dropwise to the mixed solution, adjusting the pH value of the mixed solution to 4-5 using sodium hydroxide solution, and subjecting the mixture to a substitution reaction using microwave reaction to obtain thiolated chitosan; (2) dissolving the thiolated chitosan in isopropanol to obtain a mixed solution, adding 2,3-epoxypropyltrimethylammonium chloride aqueous solution dropwise to the mixed solution, reacting in a water bath at 75° C., dialyzing the product for 48 hours, and vacuum freeze-drying to obtain the thiolated chitosan quaternary ammonium salt; (3) Dissolving the thiolated chitosan quaternary ammonium salt in water, and adding a neutral aqueous solution of a thiophene group-containing compound dropwise into the aqueous solution to carry out an ion exchange reaction, thereby finally obtaining the thiolated chitosan quaternary ammonium salt containing the thiophene group.

5. The method for preparing the thiolated chitosan quaternary ammonium salt containing thiophene groups according to claim 4, characterized in that: In the step (1), for every 2-4 g of chitosan, 2-4.5 g of thiourea and 3-6 mL of hydrochloric acid are used; the reaction power of the microwave reactor is 640 W, and the reaction time is 2 min; the product after the reaction is precipitated with anhydrous ethanol, and washed three times to finally obtain thiolated chitosan.

6. The method for preparing the thiolated chitosan quaternary ammonium salt containing thiophene groups according to claim 4, characterized in that: In the step (2), 4.5-9 g of 2,3-epoxypropyltrimethylammonium chloride is added for every 1.5-3.5 g of thiolated chitosan.

7. The method for preparing the thiolated chitosan quaternary ammonium salt containing thiophene groups according to claim 4, characterized in that: In the step (3), 1.1-3.1 g of the thiophene group-containing compound is added to every 1-1.5 g of the thiolated chitosan quaternary ammonium salt.

8. An application of the thiolated chitosan quaternary ammonium salt containing thiophene groups according to claim 1, characterized in that: The thiophene group-containing thiolated chitosan quaternary ammonium salt is used in the preparation of antioxidants in the fields of biomedicine or agriculture.

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