Sodium alginate containing guanidine groups, and a method for preparing and using the same

Abstract

The application discloses sodium alginate containing a guanidine group and a preparation method and application thereof, and solves the problem that a complex chemical modification or a multi-component complex must be used to realize good antioxidation when the current sodium alginate-based antioxidant is prepared. The process has the characteristics of simplicity, high efficiency and economy, and has a good industrial application prospect. The method is that a one-step preparation process of the sodium alginate containing the guanidine group is designed, the sodium alginate is dissolved in deionized water, then the sodium alginate is reacted with a guanidine salt through ion exchange at a specific molar ratio at room temperature, and only simple stirring and centrifugal equipment are needed to prepare the sodium alginate containing the guanidine group which has good antioxidant activity. The application is suitable for food, medicine and agriculture and the like.

Description

Technical Field

[0001] This invention relates to the fields of food, medicine and agriculture, and specifically to a sodium alginate containing a guanidine group, its preparation method and application. Background Technology

[0002] Sodium alginate is a naturally occurring anionic polysaccharide abundant in nature. With its rich carboxyl and hydroxyl groups, sodium alginate exhibits excellent biocompatibility, biodegradability, and film-forming properties, making it an important raw material in the food and pharmaceutical industries. However, sodium alginate itself has relatively weak antioxidant activity, limiting its application in active packaging and wound dressings. To enhance its functional properties, it often requires chemical modification or compounding with other antioxidants, but this often increases process complexity and cost, and may affect its natural and safe properties. Guanidine groups are functional groups with significant bioactivity, commonly found in natural products such as creatine, exhibiting excellent antioxidant capabilities, effectively scavenging free radicals and reducing oxidative stress. Therefore, introducing guanidine groups into the structure of sodium alginate holds promise for endowing it with stronger antioxidant properties while retaining the biocompatibility of its natural polysaccharide. Grafting guanidine groups onto the sodium alginate molecular chain forms a structurally stable functionalized polysaccharide. This reaction is carried out in an aqueous phase, requiring no toxic solvents or complex catalysts, making the process green and simple. The obtained sodium alginate containing guanidine groups not only retains good water solubility and film-forming properties, but also has significantly enhanced antioxidant activity, and is expected to play an important role in functional food coatings, antioxidant medical dressings, agricultural preservation films and other fields. Summary of the Invention

[0003] The purpose of this invention is to address the deficiencies of the prior art by providing a sodium alginate containing a guanidine group, its preparation method, and its application, thereby solving the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a sodium alginate containing a guanidine group, wherein the structure of the sodium alginate containing the guanidine group is shown in formula (1). Equation (1), in Equation (1) The average degree of polymerization, n+m, ranges from 200 to 3000.

[0005] A method for preparing sodium alginate containing a guanidine group involves reacting sodium alginate directly with a guanidine salt at room temperature without the aid of a catalyst via an ion exchange reaction to obtain the product shown in formula (1), sodium alginate containing a guanidine group. The synthetic route is as follows:

[0006] A method for preparing the guanidine-containing sodium alginate described above:

[0007] Sodium alginate was completely dissolved in deionized water and then reacted with guanidine salt at room temperature for 8-14 h to obtain sodium alginate containing guanidine group as shown in formula (1). After dialysis in a dialysis bag for 2-4 days, sodium alginate solid containing guanidine group was obtained after freeze drying.

[0008] The guanidine salt is guanidine hydrochloride, methylguanidine hydrochloride, or N-ethylguanidine sulfate.

[0009] The molar ratio of the guanidine salt to sodium alginate is 1-5:1.

[0010] An application of the sodium alginate containing a guanidine group, specifically its application in the preparation of antioxidants.

[0011] The present invention has the following beneficial effects:

[0012] (1) After the sodium alginate containing guanidine group is prepared according to the present invention, its antioxidant activity is significantly improved.

[0013] (2) The sodium alginate prepared by the present invention has good biocompatibility after containing guanidine groups.

[0014] (3) The synthesis method of the present invention has the characteristics of low cost, high efficiency and green and mild conditions; the product obtained by the present invention can be widely used in food, medicine and agriculture. Attached Figure Description

[0015] Figure 1 This is the infrared spectrum of sodium alginate.

[0016] Figure 2 The infrared spectrum of guanidine-containing sodium alginate provided in this embodiment of the invention, 2354.65 cm⁻¹. -1 and 1666.19 cm -1 The peak at 1603.52 cm⁻¹ is due to the C=N stretching vibration of the guanidinyl group. -1 It is an NH bending vibration, 1404.79 cm. -1 The CN stretching vibration indicates that guanidine-containing sodium alginate has been successfully synthesized.

[0017] Figure 3 The infrared spectrum of sodium alginate containing methylguanidine provided in this embodiment of the invention, 2361.40 cm⁻¹. -1 and 1667.16 cm -1 The peak at 1605.55 cm⁻¹ is due to the C=N stretching vibration of the guanidinyl group. -1 It is an NH bending vibration, 1411.12 cm. -1 The CN stretching vibration indicates that sodium alginate containing methylguanidine has been successfully synthesized.

[0018] Figure 4The infrared spectrum of sodium alginate containing ethyl guanidine provided in this embodiment of the invention, 2355.62 cm⁻¹. -1 and 1667.26 cm -1 The peak at 1603.53 cm⁻¹ is due to the C=N stretching vibration of the guanidinyl group. -1 It is an NH bending vibration, 1409.70 cm. -1 The CN stretching vibration indicates that sodium alginate containing ethyl guanidine has been successfully synthesized. Detailed Implementation

[0019] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0020] This invention prepares sodium alginate containing guanidine groups by directly reacting sodium alginate with guanidine cations at room temperature via ion exchange reaction, and studies its scavenging ability against superoxide anion radicals and DPPH radicals, as well as its cytotoxicity to L929 cells.

[0021] The synthetic route for sodium alginate containing a guanidine group is as follows:

[0022] The average degree of polymerization, n+m, ranges from 200 to 3000.

[0023] Example 1: Equation (1)

[0024] The structural formula of guanidine-containing sodium alginate is shown in formula (1), where the value of n+m ranges from 200 to 3000.

[0025] Take 1.08 g (5 mmol) of sodium alginate (see Figure 1 After being completely dissolved in water, it was reacted with 0.48 g (5 mmol) of guanidine hydrochloride at room temperature for 8 h. After the reaction was completed, it was dialyzed for 3 days and then freeze-dried under vacuum to obtain sodium alginate containing guanidine (see [link to product]). Figure 2 ).

[0026] Figure 2 The infrared spectrum of sodium alginate containing guanidine in Example 1 of this invention is shown at 2354.65 cm⁻¹. -1 and 1666.19 cm -1 The peak at 1603.52 cm⁻¹ is due to the C=N stretching vibration of the guanidinyl group. -1 It is an NH bending vibration, 1404.79 cm. -1The result is a CN stretching vibration, which proves that sodium alginate containing guanidine was successfully synthesized.

[0027] Example 2: Equation (2)

[0028] The structural formula of sodium alginate containing methylguanidine is shown in formula (2), where the value of n+m ranges from 200 to 3000.

[0029] The difference from Example 1 is that:

[0030] Take 1.08 g (5 mmol) of sodium alginate (see Figure 1 After being completely dissolved in water, it was reacted with 0.55 g (5 mmol) of methylguanidine hydrochloride at room temperature for 8 h. After the reaction was completed, it was dialyzed for 3 days and then freeze-dried under vacuum to obtain sodium alginate containing methylguanidine (see [link to product description]). Figure 3 ).

[0031] Figure 3 The infrared spectrum of sodium alginate containing methylguanidine in Example 2 of this invention is shown at 2361.40 cm⁻¹. -1 and 1667.16cm -1 The peak at 1605.55 cm⁻¹ is due to the C=N stretching vibration of the guanidinyl group. -1 It is an NH bending vibration, 1411.12 cm. -1 The signal is a CN stretching vibration, which proves that sodium alginate containing methylguanidine was successfully synthesized.

[0032] Example 3: Equation (3)

[0033] The structural formula of sodium alginate containing ethyl guanidine is shown in formula (3), where the value of n+m ranges from 200 to 3000.

[0034] The difference from Example 1 is that:

[0035] Take 1.08 g (5 mmol) of sodium alginate (see Figure 1 After being completely dissolved in water, it was reacted with 1.36 g (5 mmol) of N-ethylguanidine sulfate at room temperature for 8 h. After the reaction was completed, it was dialyzed for 3 days and then freeze-dried under vacuum to obtain sodium alginate containing ethylguanidine (see [link to product description]). Figure 4 ).

[0036] Figure 4 The infrared spectrum of sodium alginate containing ethyl guanidine in Example 3 of this invention is shown at 2355.62 cm⁻¹. -1 and 1667.26cm-1 The peak at 1603.53 cm⁻¹ is due to the C=N stretching vibration of the guanidinyl group. -1 It is an NH bending vibration, 1409.70 cm. -1 The result is a CN stretching vibration, which proves that sodium alginate containing ethyl guanidine was successfully synthesized.

[0037] Application Example 1: Determination of Antioxidant Activity

[0038] Superoxide anion radical scavenging rate determination: The superoxide anion radical scavenging ability of sodium alginate and the guanidine-containing sodium alginate prepared in the above examples was determined and compared (Table 1): The guanidine-containing sodium alginate prepared in the above examples and the experimental sodium alginate were prepared into a stock solution with a concentration of 10 mg / mL. The stock solution was used to prepare test solutions with concentration gradients of 0.1, 0.2, 0.4, 0.8, and 1.6 mg / mL. 0.5 mL of reducing coenzyme I (NADH, 0.2453 mg / mL), 0.5 mL of methyl phenazine sulfate (PMS, 0.01838 mg / mL), and 0.5 mL of nitrotetrazole blue (NBT, 0.3657 mg / mL) were added to the experimental group in sequence. In the control group, the NADH solution was replaced with Tris-HCl buffer (1.9697 mg / mL); the blank sample solution was replaced with Tris-HCl buffer. After mixing each group of solutions, they were allowed to stand for 5 min. The absorbance of each sample at 560 nm was measured three times. The superoxide anion radical scavenging capacity of the tested samples was calculated using the following formula:

[0039] Clearance rate (%) = [1 - (A)] 样品 -A 对照 ) / A 空白 ]×100

[0040] Among them, A 样品 A represents the absorbance of the experimental group. 对照 Absorbance of the control group; A 空白 The absorbance is for the blank group.

[0041] The results of the superoxide anion free radical scavenging capacity determination are shown in Table 1:

[0042] Table 1. Superoxide anion radical scavenging capacity (%) of sodium alginate and sodium alginate containing guanidine groups.

[0043] Application Example 2: Determination of Antioxidant Activity

[0044] DPPH radical scavenging rate determination: The DPPH radical scavenging ability of sodium alginate and the guanidine-containing sodium alginate prepared in the above examples was determined and compared (Table 2): The sodium alginate and guanidine-containing sodium alginate obtained in the above examples were prepared into stock solutions with a concentration of 10 mg / mL. The sample solutions were mixed with deionized water, and 2.0 mL of DPPH / ethanol (180 μmol / L) was added, with concentrations of 0.1, 0.2, 0.4, 0.8, and 1.6 mg / mL, respectively. 2.0 mL of DPPH / ethanol was replaced with 2.0 mL of ethanol as a control. 1.0 mL of deionized water was mixed with 2.0 mL of DPPH / ethanol as a blank. Each group of solutions was mixed and incubated in the dark for 20 min. The absorbance of each group of samples at 517 nm was measured, and each sample was measured three times. The DPPH radical scavenging ability was calculated by the following formula:

[0045] Clearance rate (%) = [1 - (A)] 样品 -A 对照 ) / A 空白 ]×100

[0046] Among them, A 样品 A represents the absorbance of the experimental group. 对照 Absorbance of the control group; A 空白 The absorbance is for the blank group.

[0047] The results of the DPPH free radical scavenging capacity determination are shown in Table 2:

[0048] Table 2. DPPH radical scavenging capacity (%) of sodium alginate and sodium alginate containing guanidine groups.

[0049] Application Example 3: Biocompatibility Determination

[0050] The cytotoxicity of the samples to L929 cells was determined using the MTT assay: cell suspensions were seeded into 96-well plates and cultured to 10 × 10⁶ cells / well. 4 ~ 5 Cells / well. L929 cells were treated with samples at concentrations of 400, 200, 100, 50, and 25 μg / mL. After incubation in a cell culture incubator for 24 h, 100 μL of MTT solution (0.5 mg / mL) was added to each well, and incubation continued for 4 h. After removing the MTT solution, 150 μL of DMSO was added to each well, and the cells were shaken in the dark for 15 min. The absorbance was measured at 490 nm, and cell viability was calculated using the following formula:

[0051] Cell viability (%) = (A 样品 -A 空白 ) / (A 对照 -A 空白 )×100

[0052] Among them, A 样品 A represents the absorbance of the experimental group. 对照 Absorbance of the control group; A 空白 The absorbance is for the blank group.

[0053] The results of cell viability assays are shown in Table 3:

[0054] Table 3 Cell survival rates (%) of sodium alginate and sodium alginate containing guanidine groups

[0055] Experimental Results: The ability of sodium alginate containing guanidine groups synthesized in this invention to inhibit superoxide anion radicals and DPPH radicals is shown in Tables 1 and 2. Sodium alginate itself has weak antioxidant activity, while the antioxidant capacity of sodium alginate containing guanidine groups prepared after introducing guanidine groups is significantly better than that of sodium alginate. At a test concentration of 0.8 mg / mL, sodium alginate containing ethyl guanidine scavenged more than 57% of free radicals, and especially at the highest test concentration of 1.6 mg / mL, the scavenging rate reached more than 76%, indicating that the introduction of guanidine groups can enhance the antioxidant activity of sodium alginate.

[0056] The cytotoxicity tests of the guanidine-containing sodium alginate and sodium alginate synthesized in this invention on L929 cells are shown in Table 3. After treatment with sodium alginate samples at different test concentrations, the cell viability of L929 cells was consistently above 86%, demonstrating that sodium alginate is non-toxic. At a concentration of 25 μg / mL, the cell viability of both guanidine-containing sodium alginate and sodium alginate was above 80%, indicating that both guanidine-containing sodium alginate and sodium alginate are non-toxic at this concentration and possess good biocompatibility.

[0057] The above description is merely an embodiment of the present invention. It should be noted that those skilled in the art can make several improvements without departing from the concept of the present invention, such as replacing the type of guanidine salt, changing the molecular weight of sodium alginate, changing the concentration of reactants, etc. These improvements should also be considered within the scope of protection of the present invention.

Claims

1. A sodium alginate containing a guanidine group, characterized in that: The structure of sodium alginate containing a guanidine group is shown in formula (1): Equation (1), in Equation (1) The average degree of polymerization, n+m, ranges from 200 to 3000.

2. A method for preparing sodium alginate containing a guanidine group as described in claim 1, characterized in that: Sodium alginate is reacted directly with guanidine salt at room temperature without the need for a catalyst via ion exchange to obtain sodium alginate containing a guanidine group as shown in formula (1). The specific steps are as follows: Sodium alginate was completely dissolved in deionized water and then reacted with guanidine salt at room temperature for 8-14 h to obtain sodium alginate containing guanidine group as shown in formula (1). After dialysis in a dialysis bag for 2-4 days, sodium alginate solid containing guanidine group was obtained after freeze drying.

3. A method for preparing sodium alginate containing a guanidine group as described in claim 2: characterized in that, The guanidine salt is N-ethylguanidine sulfate.

4. A method for preparing sodium alginate containing a guanidine group as described in claim 2: characterized in that, The molar ratio of guanidine salt to sodium alginate is 1-5:

1.

5. An application of sodium alginate containing a guanidine group as described in claim 1, characterized in that: The application of sodium alginate containing guanidine groups in the preparation of antioxidants.

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