A glutamic acid modified astragalus polysaccharide, a preparation method thereof and antioxidant application thereof

Abstract

The present application relates to the technical field of polysaccharide modification, and specifically discloses a glutamic acid modified astragalus polysaccharide, a preparation method thereof and an antioxidant application thereof. The preparation method comprises the following steps: adding a glutamic acid aqueous solution and epichlorohydrin into an alkaline solution, uniformly mixing, reacting at 50-60 DEG C for 2-3 hours to obtain an intermediate product; uniformly mixing astragalus polysaccharide, an alkaline solution and an alcohol solution, adding the intermediate product, reacting at 50-60 DEG C for 3-5 hours to obtain the glutamic acid modified astragalus polysaccharide. The present application uses naturally degradable astragalus polysaccharide as a substrate, and modifies the astragalus polysaccharide by using glutamic acid through a reasonable and feasible green process, so that the antioxidant property of the astragalus polysaccharide is significantly improved, and the water-insoluble content is obviously reduced, thereby effectively increasing the addition amount of the astragalus polysaccharide in cosmetics, significantly improving the practicability, and having a wide application prospect in antioxidant and anti-aging cosmetics.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polysaccharide modification, and particularly relates to glutamic acid modified astragalus polysaccharide and a preparation method and antioxidant application thereof. BACKGROUND

[0002] The human body suffers from ultraviolet rays, mental stress and other adverse stimuli every day, which can cause the body to produce excess free radicals, leading to damage to normal cells and tissues of the human body, thereby causing some health problems. Antioxidants can remove excess free radicals in cells and have an important role in human health. Chemically synthesized antioxidants, such as butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and the like, have high toxic side effects on the human body. The most commonly used antioxidant vitamin C has low stability, and the diene alcohol structure in its molecular structure is easily oxidized by air, thereby losing antioxidant activity. Therefore, the research on new natural antioxidants with high efficiency and safety has been the focus of researchers at home and abroad.

[0003] Astragalus polysaccharide is connected by D-galacturonic acid through an alpha-1,4 glycosidic bond, and arabinose, xylose, galactose, rhamnose and fucose exist in the side chain structure. Astragalus polysaccharide can be used as an immune enhancer to stimulate the immune system of animals and has important effects in anti-tumor, anti-virus, antioxidant, blood glucose control and improvement of cardiovascular function, and therefore, the activity research and application of astragalus polysaccharide have been paid more and more attention by people. However, astragalus polysaccharide has defects such as poor water solubility, high content of water insoluble matter, poor acid and alkali resistance and low biological activity, which greatly limits its application. Therefore, modification of astragalus polysaccharide plays a crucial role in expanding the practical application range of astragalus polysaccharide. SUMMARY

[0004] In view of the problems of poor water solubility, high content of water insoluble matter, poor acid and alkali resistance and low biological activity of the existing astragalus polysaccharide, the present application provides a glutamic acid modified astragalus polysaccharide, a preparation method and antioxidant application thereof.

[0005] To solve the above technical problems, the technical scheme provided by the present application is as follows:

[0006] A glutamic acid modified astragalus polysaccharide, the chemical structural formula of which is shown as formula I:

[0007]

[0008] Formula I

[0009] wherein n is 200-600, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 are selected from -H or R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 cannot be -H simultaneously.

[0010] The main chain component of astragalus polysaccharide molecules is more, the glycosidic bond is stable, and the intermolecular hydrogen bond is more easily formed, resulting in a tight molecular structure and poor hydrophilic ability, which is greatly limited in practical application; and the astragalus polysaccharide has low antioxidant property, and it is difficult to achieve ideal antioxidant effect in cosmetics.

[0011] In view of the problems of poor water solubility and low biological activity of the existing astragalus polysaccharide, the present application grafts glutamic acid to the astragalus polysaccharide, introduces multiple carboxyl groups into the astragalus polysaccharide molecules, increases the electrostatic repulsion in the astragalus polysaccharide molecules, makes the molecular chain relaxed, reduces the close and tight hydrogen bond in the molecules, improves the water solubility of the astragalus polysaccharide, and at the same time, makes the astragalus polysaccharide have more surface area and more opportunities to contact with free radicals, greatly improves the antioxidant property. The glutamic acid modified astragalus polysaccharide provided by the present application has stable performance, is green and degradable, has high water solubility and antioxidant property, and is expected to become a new green macromolecular antioxidant to replace synthetic antioxidants, and has wide potential application value.

[0012] During the test process, the inventors tried to graft and modify various polysaccharides with amino acids to improve the water solubility and antioxidant property of the polysaccharide substances, and unexpectedly found that the modification of the astragalus polysaccharide with glutamic acid can significantly improve the antioxidant property and water solubility of the astragalus polysaccharide. The hydroxyl radical scavenging rate of the 0.5 mg / mL glutamic acid modified astragalus polysaccharide aqueous solution can reach 97.6±3.5%, which is significantly better than the antioxidant property of the astragalus polysaccharide itself (the hydroxyl radical scavenging rate is 2.95±1.2%); and the hydroxyl radical scavenging rate of the 1 mg / mL glutamic acid modified astragalus polysaccharide aqueous solution can reach 100%, and the hydroxyl radical scavenging rate of the astragalus polysaccharide aqueous solution with the same concentration is only 31.6±1.9%, while the hydroxyl radical scavenging rate of the vitamin C aqueous solution with the same concentration is 97.5%, which is far beyond the expectation of the inventors and achieves an unexpected technical effect.

[0013] Preferably, the molar substitution degree of the is 0.4-1.0.

[0014] It should be noted that the conformation of the above glutamic acid includes L and D types.

[0015] The present application also provides a preparation method of the above glutamic acid modified astragalus polysaccharide, at least comprising the following steps:

[0016] Step a, the glutamic acid aqueous solution and epichlorohydrin are added into the alkaline solution, mixed uniformly, and reacted at 50-60 DEG C for 2-3 hours to obtain an intermediate product;

[0017] Step b, the astragalus polysaccharide, the alkaline solution and the alcohol solution are mixed uniformly, the intermediate product is added, and reacted at 50-60 DEG C for 3-5 hours to obtain the glutamic acid modified astragalus polysaccharide.

[0018] The preparation method of the glutamic acid modified astragalus polysaccharide provided by the application uses epichlorohydrin as a connecting agent and adopts a two-step method to prepare the glutamic acid modified astragalus polysaccharide. First, the glutamic acid neutralized by alkali is reacted with epichlorohydrin, so that the amino group of sodium glutamate is reacted with the ring-opening reaction of the epoxy group of epichlorohydrin, and then the intermediate product is obtained by dehydrochlorination under alkaline conditions. Then, the hydroxyl group of the astragalus polysaccharide is activated by deprotonation reaction using alkali, and then etherification reaction is carried out between the oxygen negative ion of the astragalus polysaccharide and the intermediate product. The reaction retains the amino group and the carboxyl group of glutamic acid, so that the biological characteristics of glutamic acid are retained, the antioxidant property and the water solubility of the synthesized glutamic acid modified astragalus polysaccharide are obviously improved, and thus the practical application range of the astragalus polysaccharide is improved.

[0019] The principle of preparing the glutamic acid modified astragalus polysaccharide is as follows:

[0020] The reaction formula of the reaction between glutamic acid and epichlorohydrin is shown in formula (1):

[0021]

[0022] Formula (1)

[0023] The reaction formula of the reaction between the intermediate product and the astragalus polysaccharide is shown in formula (2):

[0024]

[0025] Formula (2)

[0026] Wherein, n is 200-600, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 are selected from -H or , and R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 cannot be -H at the same time.

[0027] Preferably, in step a, the mass concentration of the glutamic acid aqueous solution is 50%-60%.

[0028] Preferably, in steps a and b, the alkaline solution is a sodium carbonate solution, a sodium hydroxide solution or a potassium hydroxide solution.

[0029] Further preferably, in steps a and b, the mass concentration of the alkaline solution is 30% to 35%.

[0030] Preferably, in step a, the molar ratio of the base in the alkaline solution to glutamic acid is 1.5:1 to 2:1.

[0031] By controlling the molar ratio of glutamic acid to base, the carboxyl group of glutamic acid can be fully protected to prevent self-condensation of glutamic acid during the reaction, thereby fully retaining the carboxyl group and improving the reaction efficiency of glutamic acid with epichlorohydrin.

[0032] Preferably, in step a, the molar ratio of epichlorohydrin to glutamic acid is 0.5:1 to 1:1.

[0033] By controlling the ratio of epichlorohydrin to glutamic acid, side reactions caused by excess epichlorohydrin can be avoided.

[0034] Preferably, in step b, the molar ratio of the base in the alkaline solution to the intermediate product is 1:1 to 1.4:1.

[0035] By controlling the amount of base added, the hydrogen bonds in astragalus polysaccharide can be broken, the intermolecular forces can be weakened, and the molecular chains can be relaxed, which is conducive to the subsequent modification reaction and improves the reaction efficiency.

[0036] Preferably, in step b, the molar ratio of the intermediate product to astragalus polysaccharide is 0.5:1 to 1.2:1.

[0037] If the molar ratio of the intermediate product to astragalus polysaccharide is too small, there are few effective functional groups grafted onto the astragalus polysaccharide molecules, and the antioxidant capacity cannot be effectively improved; if the molar ratio of the intermediate product to astragalus polysaccharide is too large, there are too many effective functional groups in the astragalus polysaccharide, which can easily cause the molecular chains to agglomerate, and the antioxidant capacity cannot be effectively improved.

[0038] Preferably, the ratio of the intermediate product to astragalus polysaccharide can ensure that the glutamic acid-modified astragalus polysaccharide prepared has good antioxidant properties and water solubility.

[0039] Preferably, in step b, the alcohol solution is an isopropyl alcohol aqueous solution, an ethanol aqueous solution or a tert-butyl alcohol aqueous solution, and the mass concentration thereof is 70% to 80%.

[0040] Preferably, in step b, the amount of the alcohol solution added is 2.8 to 3.2 times the mass of the astragalus polysaccharide.

[0041] The preferred alcohol solution and the addition amount of the alcohol solution can promote the intermediate to fully react with the astragalus polysaccharide, obtain a moderate degree of substitution, ensure the effective improvement of the antioxidant property and the water solubility, and improve the reaction efficiency.

[0042] It should be noted that after the reaction in steps a and b is completed, ethanol is added to the reaction system for precipitation and washing, and then the corresponding product is obtained through filtration and freeze-drying.

[0043] Further, in step b, after the reaction is completed, hydrochloric acid is first added to adjust the pH to about 6, and then ethanol is added for precipitation and washing.

[0044] The preparation method of the glutamic acid modified astragalus polysaccharide provided by the present application is simple, the reaction conditions are mild, the modified astragalus polysaccharide prepared has stable performance and strong antioxidant capacity, and can be used as a natural antioxidant, and has potential application value in the preparation of antioxidant and anti-aging cosmetics.

[0045] The present application also provides the use of the above-mentioned glutamic acid modified astragalus polysaccharide in the preparation of anti-aging cosmetics.

[0046] The present application uses naturally degradable astragalus polysaccharide as a substrate, and modifies the astragalus polysaccharide by using glutamic acid through a reasonable and feasible green process, so that the antioxidant property of the astragalus polysaccharide is significantly improved, the water-insoluble content is greatly reduced, the hydroxyl radical clearance rate can reach 97.6±3.5% or more, and the solubility (25℃) of the modified astragalus polysaccharide is reduced from 9% to 0.85%, which can effectively increase the addition amount of the astragalus polysaccharide in cosmetics, significantly improve the practicability, and has a broad application prospect in antioxidant and anti-aging cosmetics. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 The infrared spectrum of the glutamic acid modified astragalus polysaccharide prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0049] In order to better illustrate the present application, the following examples are further illustrated.

[0050] Example 1

[0051] The present embodiment provides a preparation method of glutamic acid modified astragalus polysaccharide, comprising the following steps:

[0052] Step a; 14.71 g (0.1 mol) of glutamic acid, 26.40 g (0.2 mol) of 30.3% sodium hydroxide aqueous solution, 14 g of water and 9.25 g (0.1 mol) of epichlorohydrin were uniformly mixed, and the temperature was raised to 50°C for 3 h. After the reaction was completed, the lower precipitate was washed with 85% ethanol until the upper liquid was clear, and then freeze-dried to obtain an intermediate product;

[0053] Step b; 16.2 g of astragalus polysaccharide (0.1 mol), 48.6 g of 75% isopropyl alcohol aqueous solution and 7.92 g (0.06 mol) of 30.3% sodium hydroxide aqueous solution were uniformly mixed, and the temperature was raised to 50°C. Then, 12.36 g (0.05 mol) of the intermediate product prepared in the above step was added, and the reaction was carried out at 55°C for 3.5 h. After the reaction was completed, 8.52 g (0.07 mol) of 30% hydrochloric acid was added to neutralize to pH 6.0. Then, ethanol was added to the reaction liquid for washing and precipitation, and the filter cake was dried to constant weight to obtain glutamic acid modified astragalus polysaccharide as shown in formula I, with a water insoluble content of 0.97% and a glutamic acid substitution degree of 0.42.

[0054]

[0055] Formula I

[0056] wherein n is 200-600, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 are selected from -H or , and R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 cannot be -H at the same time.

[0057] The infrared spectra of astragalus polysaccharide and glutamic acid modified astragalus polysaccharide prepared in this example are shown in Figure 1 The O-H stretching vibration peak appears near 3410 cm -1 , the methylene stretching vibration peak appears near 2926 cm -1 , 1655 cm -1 and 1442 cm -1 correspond to the symmetric and asymmetric stretching vibration peaks of carboxyl. The peak at 1320 cm -1 corresponds to the N-H stretching vibration peak, which proves the successful grafting of glutamic acid on the astragalus polysaccharide molecules.

[0058] Example 2

[0059] The embodiment provides a preparation method of glutamic acid modified astragalus polysaccharide, which comprises the following steps:

[0060] Step a; 14.71g (0.1mol) glutamic acid, 26.00g (0.15mol) 32.5% potassium hydroxide solution, 10g water and 7.40g (0.08mol) epichlorohydrin are uniformly mixed, and the temperature is increased to 55 DEG C and reacted for 2.5h; after the reaction is completed, 85% ethanol aqueous solution is added to wash until the upper liquid is clear, and the lower precipitate is freeze-dried to obtain an intermediate product;

[0061] Step b, 16.2g astragalus polysaccharide (0.1mol), 45.4g 70% tert-butyl alcohol aqueous solution and 13.82g (0.08mol) 32.5% potassium hydroxide solution are uniformly mixed, the temperature is increased to 50 DEG C, 19.78g (0.08mol) intermediate product prepared in the above step is added, and the reaction is carried out at 60 DEG C for 3h; after the reaction is completed, 10.95g (0.09mol) 30% hydrochloric acid is added to neutralize to pH 6.1, the filter cake is dried to constant weight to obtain the glutamic acid modified astragalus polysaccharide shown in formula I, the water insoluble content is 0.86%, and the glutamic acid substitution degree is 0.67.

[0062]

[0063] Formula I

[0064] Wherein, n is 200-600, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 are selected from -H or , and R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 cannot be -H at the same time.

[0065] Example 3

[0066] The embodiment provides a preparation method of glutamic acid modified astragalus polysaccharide, which comprises the following steps:

[0067] Step a; 14.71g (0.1mol) glutamic acid, 51.50g (0.17mol) 35% sodium carbonate aqueous solution, 12g water and 4.63g (0.05mol) epichlorohydrin are uniformly mixed, and the temperature is increased to 60 DEG C and reacted for 2h; after the reaction is completed, anhydrous ethanol is added to wash until the upper liquid is clear, and the lower precipitate is freeze-dried to obtain an intermediate product;

[0068] Step b, 16.2 g of astragalus polysaccharide (0.1 mol), 51.9 g of 80% ethanol aqueous solution and 48.46 g (0.16 mol) of 35% sodium carbonate aqueous solution were uniformly mixed, heated to 50°C, 29.66 g (0.12 mol) of the above prepared intermediate was added, and reacted at 50°C for 5 h. After the reaction was completed, ethanol was added to the reaction solution for washing and sedimentation. The filter cake was dried to constant weight to obtain glutamic acid modified astragalus polysaccharide as shown in formula I, with a water insoluble content of 0.81% and a glutamic acid substitution degree of 0.95.

[0069]

[0070] Formula I

[0071] wherein n is 200-600, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 are selected from -H or , and R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 , R 11 and R 12 cannot be -H at the same time.

[0072] Comparative Example 1

[0073] The present comparative example provides a preparation method of glycine modified astragalus polysaccharide, specifically comprising the following steps:

[0074] Step a, 7.51 g (0.1 mol) of glycine, 26.40 g (0.2 mol) of 30.3% sodium hydroxide aqueous solution, 14 g of water and 9.25 g (0.1 mol) of epichlorohydrin were uniformly mixed, heated to 50°C and reacted for 3 h. After the reaction was completed, anhydrous ethanol was added to the reaction solution for washing until the upper liquid was clear. The lower precipitate was freeze-dried to obtain an intermediate product;

[0075] Step b, 16.2 g of astragalus polysaccharide (0.1 mol), 48.6 g of 75% isopropanol aqueous solution and 7.92 g (0.06 mol) of 30.3% sodium hydroxide aqueous solution were uniformly mixed, heated to 50°C, 12.36 g (0.05 mol) of the above prepared intermediate was added, and reacted at 55°C for 3.5 h. After the reaction was completed, 8.52 g (0.07 mol) of 30% hydrochloric acid was added to neutralize to pH 6.0. The filter cake was dried to constant weight to obtain glycine modified astragalus polysaccharide, with a water insoluble content of 0.94% and a glycine substitution degree of 0.44.

[0076] Performance test

[0077] 1. Degree of substitution test

[0078] The degree of substitution of glutamic acid modified astragalus polysaccharide and glycine modified astragalus polysaccharide is determined by acid-base titration method, and the specific steps are as follows:

[0079] The 732 type cation exchange resin is placed in a beaker, soaked and stirred in 3 mol / L hydrochloric acid solution for 0.5 h, and then washed with distilled water for several times until no Cl - can be detected in the water solution. Then the 732 type cation exchange resin is placed in 2.2 mol / L sulfuric acid solution and soaked and stirred for 3 h, and then washed with distilled water for several times until no SO4 2- can be detected in the water solution, thereby obtaining the activated cation exchange resin.

[0080] 2 g of astragalus polysaccharide, glutamic acid modified astragalus polysaccharide and glycine modified polysaccharide are respectively dispersed in 80 mL of 80% ethanol aqueous solution, and exchanged with the activated cation exchange resin (3 times of the mass of the polysaccharide sample) for 3 h to ensure that the sodium ions of the amino acid modified astragalus polysaccharide are all exchanged into hydrogen ions. The activated cation exchange resin is separated, and the polysaccharide sample is dried to constant weight. The exchanged polysaccharide sample of m g is accurately weighed, dissolved in 15 mL of 0.08 mol / L sodium hydroxide solution, and the sodium hydroxide solution is back titrated with 0.08 mol / L hydrochloric acid solution. The amount of hydrochloric acid used is recorded, and the amount of sodium hydroxide consumed by the uronic acid of the astragalus polysaccharide itself is removed, and the consumption of sodium hydroxide for grafting glutamic acid is calculated.

[0081] DS = M1A / (1-M2A)

[0082] A = (C1V1-C2V2) / m

[0083] In the formula, DS is the degree of substitution of carboxyl in the sample; M1 is the molar mass of a single astragalus sugar unit, g / mol; M2 is the molar mass of the amino acid monomer reacted with the astragalus polysaccharide, g / mol; C1 is the concentration of sodium hydroxide, mol / L; V1 is the volume of consumed sodium hydroxide, L; C2 is the concentration of hydrochloric acid, mol / L; V2 is the volume of consumed hydrochloric acid, L; and m is the mass of the titrated sample, g.

[0084] 2. Water insoluble content test

[0085] The glutamic acid modified astragalus polysaccharide prepared in Examples 1-3 is subjected to water insoluble content test according to the provisions of Chinese Pharmacopoeia 2005 edition. The test results prove that the water insoluble content of the glutamic acid modified astragalus polysaccharide prepared in the examples of the present application is less than 1%, which is significantly lower than the water insoluble content (9%) of unmodified astragalus polysaccharide, which is of great importance for the subsequent application of astragalus polysaccharide in antioxidant and anti-aging cosmetics.

[0086] 3. Antioxidant performance test

[0087] 3.1 Hydroxyl radical scavenging activity

[0088] The astragalus polysaccharide, the glutamic acid-modified astragalus polysaccharide prepared in Example 1, the glycine-modified astragalus polysaccharide prepared in Comparative Example 1 and vitamin C were respectively prepared into sample solutions of 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL and 5 mg / mL with deionized water.

[0089] 1.5 mL of the above-prepared sample solution, 1.5 mL of 0.6 mmol / L salicylic acid-ethanol solution and 1.5 mL of 0.6 mmol / L hydrogen peroxide solution were uniformly mixed, reacted at 37°C for 35 min, and the absorbance was measured at a wavelength of 510 nm.

[0090] Hydroxyl radical scavenging rate (%) = (A0-A1) / A0*100%

[0091] In the formula: A0 is the absorbance of the blank ABTS solution without adding the sample solution;

[0092] A1 is the absorbance of the ABTS solution with the sample solution added.

[0093] The results are shown in Table 1.

[0094] Table 1 Hydroxyl radical scavenging rate (%)

[0095]

[0096] It can be seen from the results that the glutamic acid-modified astragalus polysaccharide has excellent hydroxyl radical scavenging activity, and the hydroxyl radical scavenging rate of the 0.5 mg / mL glutamic acid-modified astragalus polysaccharide aqueous solution can reach the effect comparable to that of vitamin C, and is significantly higher than that of the glycine-modified astragalus polysaccharide and the unmodified astragalus polysaccharide, which is a green macromolecular antioxidant with great application prospect.

[0097] 3.2 ABTS radical scavenging activity

[0098] 7 mmol / L ABTS aqueous solution and 2.45 mmol / L potassium persulfate aqueous solution were uniformly mixed in a volume ratio of 1:1, placed in the dark for 12 h, diluted 41 times with 0.2 mol / L, pH 6.6 sodium dihydrogen phosphate-disodium hydrogen phosphate buffer solution to obtain ABTS solution.

[0099] The Astragalus polysaccharide, the glutamic acid-modified Astragalus polysaccharide prepared in Example 1, the glycine-modified Astragalus polysaccharide prepared in Comparative Example 1 and vitamin C were respectively prepared into sample solutions of 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL and 5 mg / mL with deionized water. 4 mL of the prepared ABTS solution and 1.5 mL of the sample solution were mixed uniformly, and the absorbance was measured at 734 nm.

[0100] ABTS clearance rate (%) = (A0-A1) / A0*100%

[0101] In the formula, A0 is the absorbance of the blank ABTS solution without the sample solution;

[0102] A1 is the absorbance of the ABTS solution with the sample solution.

[0103] The results are shown in Table 2.

[0104] Table 2 ABTS clearance rate (%)

[0105]

[0106] It can be seen from the results that the glutamic acid-modified Astragalus polysaccharide has excellent ABTS free radical scavenging activity, and the hydroxyl radical clearance rate of the 2 mg / mL glutamic acid-modified Astragalus polysaccharide aqueous solution can reach the effect equivalent to that of vitamin C, and is significantly higher than that of the glycine-modified Astragalus polysaccharide and the unmodified Astragalus polysaccharide, and is a green macromolecular antioxidant with great application prospect.

[0107] The above only describes the preferred embodiments of the present application and should not be used to limit the present application, and any modification, equivalent replacement or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A glutamic acid-modified astragalus polysaccharide, characterized in that, Its chemical structural formula is shown in Formula I: Formula I Where n is 200~600, R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 and R 12 Selected from -H or respectively And R1, R2, R3, R4, R5, R6, R7, R8, R9, R 10 R 11 and R 12 It cannot be -H at the same time.

2. The glutamic acid-modified astragalus polysaccharide as described in claim 1, characterized in that, The The molar substitution degree is 0.4~1.

0.

3. A method for preparing glutamic acid-modified astragalus polysaccharide according to claim 1 or 2, characterized in that, It should include at least the following steps: Step a: Add the aqueous solution of glutamic acid and epichlorohydrin to the alkaline solution, mix well, and react at 50℃~60℃ for 2h~3h to obtain the intermediate product; Step b: Mix the astragalus polysaccharide, alkaline solution and alcohol solution evenly, add the intermediate product, and react at 50℃~60℃ for 3h~5h to obtain glutamic acid modified astragalus polysaccharide.

4. The preparation method of glutamic acid-modified astragalus polysaccharide as described in claim 3, characterized in that, In steps a and b, the alkaline solution is a sodium carbonate solution, a sodium hydroxide solution, or a potassium hydroxide solution; and / or In steps a and b, the mass concentration of the alkaline solution is 30% to 35%.

5. The preparation method of glutamic acid-modified astragalus polysaccharide as described in claim 4, characterized in that, In step a, the molar ratio of alkali to glutamic acid in the alkaline solution is 1.5:1 to 2:1; and / or In step b, the molar ratio of alkali to intermediate product in the alkaline solution is 1:1 to 1.4:

1.

6. The method for preparing glutamic acid-modified astragalus polysaccharide as described in claim 3, characterized in that, In step a, the molar ratio of epichlorohydrin to glutamic acid is 0.5:1 to 1:1; and / or In step a, the mass concentration of the glutamic acid aqueous solution is 50%~60%.

7. The method for preparing glutamic acid-modified astragalus polysaccharide as described in claim 3, characterized in that, In step b, the molar ratio of the intermediate product to Astragalus polysaccharide is 0.5:1 to 1.2:

1.

8. The method for preparing glutamic acid-modified astragalus polysaccharide as described in claim 3, characterized in that, In step b, the alcohol solution is an aqueous solution of isopropanol, an aqueous solution of ethanol, or an aqueous solution of tert-butanol, wherein its mass concentration is 70% to 80%.

9. The method for preparing glutamic acid-modified astragalus polysaccharide as described in claim 8, characterized in that, In step b, the amount of alcohol solution added is 2.8 to 3.2 times the mass of the Astragalus polysaccharide.

10. The application of the glutamic acid-modified astragalus polysaccharide according to claim 1 or 2 in the preparation of anti-aging cosmetics.

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