A wolfberry polysaccharide-zinc complex, a preparation method thereof and application thereof in zinc supplement preparations

Abstract

A wolfberry polysaccharide-zinc complex, a preparation method thereof and application thereof in zinc supplement preparations. The present application belongs to the technical field of high polymer polysaccharide chelation. The present application solves the problems of high cost, low output rate and low zinc content in the preparation of zinc supplement preparations in the prior art. The present application obtains low molecular weight wolfberry polysaccharide with a weight average molecular weight of about 3680 Da by incomplete hydrolysis of wolfberry polysaccharide. The zinc ion chelation rate of the wolfberry polysaccharide-zinc complex prepared by the present application can reach 95-98%, and the zinc content can reach 28-35%, which is much higher than that of the prior art. The wolfberry polysaccharide-zinc complex prepared by the present application has the advantages of high bioavailability, low toxicity, easy digestion and absorption, etc., and exhibits excellent biological activity in antioxidant, blood sugar reduction, anti-inflammatory, antibacterial and liver protection, etc. It can also be used as a high-quality zinc supplement.

Description

Technical Field

[0001] This invention belongs to the field of polymer polysaccharide chelation technology, specifically relating to a wolfberry polysaccharide-zinc complex, its preparation method, and its application in zinc supplements. Background Technology

[0002] Lycium barbarum polysaccharides are important active ingredients in Lycium barbarum, possessing various biological effects such as anti-tumor, antioxidant, anti-aging, and anti-inflammatory properties, demonstrating significant research value and application potential. The antioxidant activity of Lycium barbarum polysaccharides can scavenge free radicals in the body, reduce oxidative stress damage to cells, enhance the function of the body's immune system, and improve the body's resistance to pathogens. Lycium barbarum polysaccharides can also improve the sensitivity of pancreatic islet cells, increase serum insulin levels, thereby effectively controlling blood sugar fluctuations and regulating blood sugar levels, helping to maintain blood sugar within the normal range.

[0003] Zinc is an essential trace element for the human body, primarily obtained through food. Compared to other trace elements, zinc is more closely related to our lives, influencing physiological processes such as protein and DNA synthesis, cell growth and proliferation, hormone function, immune defense mechanisms, and metabolic regulation. However, when the body is deficient in zinc, it can be obtained through zinc supplements. Common zinc supplements currently available are mainly inorganic metal salts such as zinc gluconate, zinc lactate, and zinc sulfate. These supplements are costly to prepare, have low yields, and low zinc content, requiring large doses to achieve the desired zinc supplementation effect. By chelating polysaccharides with divalent zinc ions to prepare polysaccharide-zinc complexes, organic zinc supplements are formed. These supplements possess advantages such as high bioavailability, low toxicity, and easy digestion and absorption, exhibiting excellent biological activity in areas such as antioxidation, hypoglycemia, anti-inflammation, antibacterial activity, and liver protection. Existing research shows that the chelation rate of polysaccharides-zinc is low, and the zinc content in the complex is also low. Patent CN109776694A discloses a method for preparing a copper, iron, and zinc triple chelate from brown algae polysaccharides and its application; the zinc content of the chelate in this patent is 8.5%. Patent CN112048025A discloses a water-soluble soybean polysaccharide zinc chelate as a zinc supplement, its preparation method, and its application; the zinc content of the chelate in this patent is 2-3%. Patent CN113201078B discloses a method for preparing a rice bran polysaccharide zinc chelate and its application; the zinc content of the chelate in this patent is 8-15%. Therefore, developing a low-cost zinc supplement with high zinc content is of great significance for economic and pharmaceutical development. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of high cost, low yield and low zinc content in the preparation of zinc supplements in the prior art. This invention provides a wolfberry polysaccharide-zinc complex, its preparation method and its application in zinc supplements.

[0005] The technical solution of the present invention is as follows:

[0006] One objective of this invention is to provide a method for preparing a Lycium barbarum polysaccharide-zinc complex, wherein the method includes:

[0007] S1: Dissolve wolfberry polysaccharide in HCl solution, heat in a water bath and adjust the pH to 7 to obtain a neutral solution. Cool the solution, add anhydrous ethanol and let it stand for alcohol precipitation. Centrifuge and dry to obtain incompletely hydrolyzed wolfberry polysaccharide.

[0008] S2: Dissolve the incompletely hydrolyzed Lycium barbarum polysaccharide obtained in S1 in distilled water to obtain a Lycium barbarum polysaccharide solution;

[0009] S3: The pH value of the wolfberry polysaccharide solution in S2 was adjusted by dilute sulfuric acid solution. After heating in a water bath, ZnSO4 solution was added dropwise with stirring. After sonication, the reaction was stirred again. After cooling, the reaction solution was obtained. Anhydrous ethanol was added to the reaction solution and allowed to stand for alcohol precipitation. After centrifugation and drying, the wolfberry polysaccharide-zinc complex was obtained.

[0010] Further specifying, the specific steps of S1 are as follows: dissolve 90-99% pure Lycium barbarum polysaccharide in a 1-1.5 mol / L HCl solution, heat in a water bath at 90-100℃ for 10-20 min, adjust the pH to 7 with 6-8 mol / L NaOH to obtain a neutral solution and cool it, then add anhydrous ethanol and allow it to stand for alcohol precipitation, finally centrifuge at 5000-10000 rpm and dry at 60-80℃ to obtain incompletely hydrolyzed Lycium barbarum polysaccharide with a weight-average molecular weight of 3000-4500 Da.

[0011] Further specified, the ratio of wolfberry polysaccharide to HCl solution in S1 is 1-5 g: 50 mL, and the volume ratio of anhydrous ethanol to neutral solution is 3-4: 1.

[0012] Further specified, the concentration of the incompletely hydrolyzed Lycium barbarum polysaccharide solution in S2 is 8-12 g / L; the volume ratio of the Lycium barbarum polysaccharide solution in S2 to the ZnSO4 solution in S3 is 1:1-2.

[0013] Further specifying the steps for S3, the pH value of the Lycium barbarum polysaccharide solution in S2 is adjusted using 0.01–0.03 mol / L dilute sulfuric acid solution. After heating in a water bath to 50–80°C, 0.1–0.2 mol / L ZnSO4 solution is added dropwise with stirring. After sonication, the mixture is stirred for 2.5–3.5 h. After cooling, anhydrous ethanol is added to the reaction solution and allowed to stand at 4°C for 6–12 h. Finally, the mixture is centrifuged at 5000–10000 rpm for 5–10 min and dried at 60–80°C to obtain the Lycium barbarum polysaccharide-zinc complex.

[0014] Further specified, the pH value of S3 is 5-6.

[0015] Further specified, the ultrasonic power in S3 is 120-360W, and the ultrasonic time is 5-10min.

[0016] Further specifying, the volume ratio of anhydrous ethanol to the reaction solution in S3 is 3 to 4:1.

[0017] The second objective of this invention is to provide a Lycium barbarum polysaccharide-zinc complex prepared by the above-mentioned preparation method, wherein the zinc ion chelation rate of the Lycium barbarum polysaccharide-zinc complex is 95-98% and the zinc ion content is 28-35%.

[0018] A third objective of this invention is to provide an application of the above-mentioned wolfberry polysaccharide-zinc complex in zinc supplements.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] (1) The Lycium barbarum polysaccharide selected in this invention is a major active ingredient of Lycium barbarum, mainly composed of arabinose, rhamnose, xylose, mannose, galactose and glucose, with each monosaccharide linked by pyranoside bonds. Lycium barbarum polysaccharide contains a large number of hydroxyl structures, which can complex with zinc ions. Therefore, this invention uses Lycium barbarum polysaccharide and zinc sulfate as the main raw materials to prepare Lycium barbarum polysaccharide-zinc complex. The materials used in this invention are widely available, inexpensive, and the preparation method is simple, which is conducive to industrial production.

[0021] (2) This invention obtains low molecular weight Lycium barbarum polysaccharides with a weight-average molecular weight of approximately 3680 Da by incomplete hydrolysis of Lycium barbarum polysaccharides. The zinc ion chelation rate of the Lycium barbarum polysaccharide-zinc complex prepared by this invention with this lower molecular weight can reach 95-98%, and the zinc content can reach 28-35%, which is much higher than that of the prior art, and the antioxidant capacity is significantly improved compared with Lycium barbarum polysaccharides. This is because after hydrolysis of Lycium barbarum polysaccharides, the molecular weight is reduced from tens of thousands of Da to several thousand Da, and the molecular conformation is decomposed from large molecules to smaller molecules, exposing more hydroxyl groups that can bind with zinc ions. On the other hand, ultrasonic treatment increases the probability of zinc ions contacting hydroxyl groups, thereby increasing the chelation rate and zinc ion content of the complex, achieving an effect far superior to that of the prior art.

[0022] (3) The wolfberry polysaccharide-zinc complex prepared by the present invention has advantages such as high bioavailability, low toxicity, and easy digestion and absorption. It exhibits excellent biological activity in terms of anti-oxidation, hypoglycemia, anti-inflammation, antibacterial and liver protection. Of course, it can also be used as a low-cost, high-content organic zinc supplement. Attached Figure Description

[0023] Figure 1 The chromatogram of the incompletely hydrolyzed Lycium barbarum polysaccharide prepared in Example 3;

[0024] Figure 2This is a comparison chart showing the superoxide anion free radical scavenging rates of the wolfberry polysaccharide from Example 3 and the prepared wolfberry polysaccharide-zinc complex.

[0025] Figure 3 This is a comparison chart of the hydroxyl radical scavenging rates of the Lycium barbarum polysaccharide from Example 3 and the prepared Lycium barbarum polysaccharide-zinc complex.

[0026] Figure 4 The infrared spectra of the wolfberry polysaccharide and the prepared wolfberry polysaccharide-zinc complex in Example 3 are shown. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0029] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0030] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0031] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0032] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0033] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] Example 1:

[0035] Weigh 2g of Lycium barbarum polysaccharide with a purity of 90-99%, dissolve it in 50mL of HCl solution (1mol / L), heat in a 95℃ water bath for 15min, adjust the pH to neutral with 6mol / L NaOH to obtain a neutral solution, cool to room temperature, add 4 times the volume of anhydrous ethanol to the neutral solution, let stand at 4℃ for 8h, centrifuge at 10000rpm, and dry in an oven at 70℃ to obtain incompletely hydrolyzed Lycium barbarum polysaccharide;

[0036] 100 mg of incompletely hydrolyzed Lycium barbarum polysaccharide was dissolved in 10 mL of distilled water to obtain a Lycium barbarum polysaccharide solution. The pH of the Lycium barbarum polysaccharide solution was adjusted to 5.5 with 0.02 mol / L dilute sulfuric acid. The solution was placed in a 50 °C water bath, and 15 mL of ZnSO4 (0.1 mol / L) solution was added dropwise. The solution was sonicated at 240 W for 8 min and the reaction was continued for 3 h to obtain a reaction solution. The solution was cooled to room temperature, and 4 times the volume of anhydrous ethanol was added. The solution was allowed to stand at 4 °C for 8 h and centrifuged at 8000 rpm for 5 min to obtain a precipitate. The precipitate was dried in a 70 °C oven to obtain the Lycium barbarum polysaccharide-zinc complex.

[0037] Example 2:

[0038] Weigh 2g of Lycium barbarum polysaccharide with a purity of 90-99%, dissolve it in 50mL of HCl solution (1mol / L), heat in a 95℃ water bath for 15min, adjust the pH to neutral with 6mol / L NaOH to obtain a neutral solution, cool to room temperature, add 4 times the volume of anhydrous ethanol to the neutral solution, let stand at 4℃ for 8h, centrifuge at 10000rpm, and dry in an oven at 70℃ to obtain incompletely hydrolyzed Lycium barbarum polysaccharide;

[0039] 100 mg of incompletely hydrolyzed Lycium barbarum polysaccharide was dissolved in 10 mL of distilled water to obtain a Lycium barbarum polysaccharide solution. The pH of the Lycium barbarum polysaccharide solution was adjusted to 5.2 with 0.02 mol / L dilute sulfuric acid. The solution was then placed in a 60 °C water bath, and 10 mL of ZnSO4 (0.1 mol / L) solution was added dropwise. The solution was sonicated at 360 W for 5 min and the reaction was continued for 3 h to obtain a reaction solution. The solution was cooled to room temperature, and 4 times the volume of anhydrous ethanol was added. The solution was allowed to stand at 4 °C for 8 h and then centrifuged at 8000 rpm for 5 min to obtain a precipitate. The precipitate was dried in a 70 °C oven to obtain the Lycium barbarum polysaccharide-zinc complex.

[0040] Example 3:

[0041] Weigh 2g of Lycium barbarum polysaccharide with a purity of 90-99%, dissolve it in 50mL of HCl solution (1mol / L), heat in a 95℃ water bath for 15min, adjust the pH to neutral with 6mol / L NaOH to obtain a neutral solution, cool to room temperature, add 4 times the volume of anhydrous ethanol to the neutral solution, let stand at 4℃ for 8h, centrifuge at 10000rpm, and dry in an oven at 70℃ to obtain incompletely hydrolyzed Lycium barbarum polysaccharide;

[0042] 100 mg of incompletely hydrolyzed Lycium barbarum polysaccharide was dissolved in 10 mL of distilled water to obtain a Lycium barbarum polysaccharide solution. The pH of the Lycium barbarum polysaccharide solution was adjusted to 5.5 with 0.02 mol / L dilute sulfuric acid. The solution was placed in a 70 °C water bath, and 15 mL of ZnSO4 (0.1 mol / L) solution was added dropwise. The solution was sonicated at 120 W for 10 min and the reaction was continued for 2.5 h to obtain a reaction solution. The solution was cooled to room temperature, and 4 times the volume of anhydrous ethanol was added. The solution was allowed to stand at 4 °C for 8 h and centrifuged at 8000 rpm for 5 min to obtain a precipitate. The precipitate was dried in a 70 °C oven to obtain the Lycium barbarum polysaccharide-zinc complex.

[0043] Comparative Example 1:

[0044] The difference between Comparative Example 1 and Example 1 is that the pH of the wolfberry polysaccharide solution was adjusted to 4.5 with 0.02 mol / L dilute sulfuric acid, while the other parameters and steps were the same as in Example 1.

[0045] Comparative Example 2:

[0046] The difference between Comparative Example 2 and Example 2 is that 5 mL of ZnSO4 (0.1 mol / L) solution was added, while the other parameters and steps were the same as in Example 2.

[0047] Comparative Example 3:

[0048] The difference between Comparative Example 3 and Example 3 is that the water bath temperature after adjusting the wolfberry polysaccharide solution with 0.02 mol / L dilute sulfuric acid is 40°C. All other parameters and steps are the same as in Example 3.

[0049] Comparative Example 4:

[0050] The difference between Comparative Example 4 and Example 1 is that no ultrasonic treatment was performed, while all other parameters and steps were the same as in Example 1.

[0051] Comparative Example 5:

[0052] The only difference between Comparative Example 5 and Example 3 is that unhydrolyzed Lycium barbarum polysaccharide is used to carry out a chelation reaction with zinc sulfate; all other parameters and steps are the same as in Example 3.

[0053] Figure 1 The chromatogram shows the incompletely hydrolyzed Lycium barbarum polysaccharide prepared in Example 3. The molecular weight of the hydrolyzed Lycium barbarum polysaccharide was determined by gel filtration chromatography, and the results are as follows. Figure 1 As shown, from Figure 1 We can see that the weight-average molecular weight of the incompletely hydrolyzed wolfberry polysaccharide is 3688 Da.

[0054] The zinc chelation rate and zinc content in the Lycium barbarum polysaccharide-zinc complexes of Examples 1-3 and Comparative Examples 1-5 were determined:

[0055] Determination of free Zn in the reaction system by EDTA titration 2+ The specific method for determining the content of free Zn is as follows: Take 1 mL of the reaction solution before the final alcohol precipitation of the Lycium barbarum polysaccharide-zinc complex prepared in Examples 1-3 and Comparative Examples 1-5, adjust the pH of the solution to 7-8 with 10% ammonia water, add 0.2 mL of ammonia-ammonium chloride buffer solution, add one drop of Eriochrome Black T indicator, shake well, and immediately titrate slowly with EDTA standard solution. Calculate the free Zn in the reaction system according to the following formula (1). 2+ The content of is calculated according to the following formula (2) to determine the chelation rate of the wolfberry polysaccharide-zinc complex.

[0056]

[0057] (1) In the formula: C1 represents free Zn 2+ The concentrations are: C0 represents the concentration of the EDTA standard solution, V1 represents the total volume of the solution before titration, and V0 represents the volume of EDTA standard solution consumed.

[0058]

[0059] (2) In the formula: C1 represents free Zn 2+ The concentration, C2 indicates the addition of Zn 2+ The concentration.

[0060] The zinc content in the wolfberry polysaccharide-zinc complexes prepared in Examples 1-3 and Comparative Examples 1-5 was determined according to the standard GB 5009.14-2017 "National Food Safety Standard - Determination of Zinc in Food". The results are shown in Table 1.

[0061] Table 1. Zinc chelation rate and zinc content in the Lycium barbarum polysaccharide-zinc complexes of Examples 1-3 and Comparative Examples 1-5.

[0062] Example 1 96.7％ 32.3％ Example 2 95.3％ 30.7％ Example 3 97.5％ 34.2％ Comparative Example 1 78.3％ 22.3％ Comparative Example 2 43.6％ 13.6％ Comparative Example 3 83.8％ 24.7％ Comparative Example 4 87.4％ 26.7％ Comparative Example 5 88.6％ 27.2％

[0063] As can be seen from Table 1, the zinc chelation rate in the wolfberry polysaccharide-zinc complexes prepared in Examples 1-3 is greater than 95%, and the zinc content is greater than 30%. In contrast, the zinc chelation rate in the wolfberry polysaccharide-zinc complexes prepared in Comparative Examples 1-5 is less than 90%, and the zinc content is less than 28%. Furthermore, Comparative Examples 1-5 and Examples 1-3 differ only in one parameter, demonstrating that the technical solution of the present invention can effectively improve the zinc chelation rate and zinc content in the wolfberry polysaccharide-zinc complex.

[0064] Determination of superoxide anion free radical scavenging capacity:

[0065] The Lycium barbarum polysaccharide-zinc complex prepared in Example 3 was used to prepare solutions of Lycium barbarum polysaccharide and Lycium barbarum polysaccharide-zinc complex at different concentrations (0.2, 0.4, 0.6, 0.8, 1.0 mg / mL). 1 mL of each sample was added to 4.5 mL of Tris-HCl buffer (50 mmol / L, pH 8.2) and mixed thoroughly. After reacting for 20 min in a 25°C water bath, 0.1 mL of pyrogallol solution (3 mmol / L) was added, and the reaction was continued at 25°C for another 5 min. The reaction was then terminated by adding 1 mL of 8 mmol / L hydrochloric acid. The absorbance A1 of the solution was measured at 320 nm using a visible spectrophotometer. Distilled water was used as a blank control to measure the absorbance A0. The absorbance A2 was measured using 0.1 mL of distilled water instead of the pyrogallol solution (3 mmol / L). The formula for calculating the superoxide anion radical scavenging rate is as follows:

[0066]

[0067] Figure 2 This is a comparison chart showing the superoxide anion free radical scavenging rates of the *Lycium barbarum* polysaccharide from Example 3 and the prepared *Lycium barbarum* polysaccharide-zinc complex. Figure 2It can be seen that, at the same concentration, the Lycium barbarum polysaccharide-zinc complex has a better scavenging ability against superoxide anion free radicals than Lycium barbarum polysaccharide. This is because Lycium barbarum polysaccharide and Zn... 2+ After binding, the resulting wolfberry polysaccharide-zinc complex reacts more stably with the intermediates generated by the free radical reaction, thus the wolfberry polysaccharide-zinc complex has a stronger ability to scavenge free radicals and is more beneficial to human health.

[0068] Hydroxyl radical scavenging ability determination:

[0069] The Lycium barbarum polysaccharide-zinc complex prepared in Example 3 was used to prepare Lycium barbarum polysaccharide and Lycium barbarum polysaccharide-zinc complex solutions of different concentrations (0.2, 0.4, 0.6, 0.8, 1.0 mg / mL). 1 mL of the sample solution was added to 1 mL of ferrous sulfate solution (9 mmol / L) and 1 mL of salicylic acid solution (9 mmol / L). After thorough mixing, the solution was allowed to stand at room temperature for 5 min. Then, 1 mL of H2O2 solution (8.8 mmol / L) was added, and the mixture was stirred. The solution was then reacted in a 37°C water bath for 30 min. The absorbance A1 of the solution was measured at a wavelength of 510 nm using a visible spectrophotometer. Distilled water was used as a blank control to measure the absorbance A0. The absorbance A2 was obtained by replacing 1 mL of H2O2 solution (8.8 mmol / L) with 1 mL of distilled water. The formula for calculating the hydroxyl radical scavenging rate is as follows:

[0070]

[0071] Figure 3 This is a comparison chart showing the hydroxyl radical scavenging rates of the *Lycium barbarum* polysaccharide from Example 3 and the prepared *Lycium barbarum* polysaccharide-zinc complex. From... Figure 3 It can be seen that, at the same concentration, the scavenging ability of the Lycium barbarum polysaccharide-zinc complex for hydroxyl radicals is significantly better than that of Lycium barbarum polysaccharide. This is because when Lycium barbarum polysaccharide combines with zinc ions, the resulting coordination structure enhances the interaction with the exposed active groups, thereby strengthening the reaction efficiency with free radicals.

[0072] Figure 4 The images show the infrared spectra of the Lycium barbarum polysaccharide and the prepared Lycium barbarum polysaccharide-zinc complex from Example 3. Figure 4 As shown, both Lycium barbarum polysaccharide and the Lycium barbarum polysaccharide-zinc complex exhibit typical characteristic absorption peaks of polysaccharides. Lycium barbarum polysaccharide shows a peak at 3434.76 cm⁻¹. -1 The wavelength at which the absorption peak of the -OH group in the Lycium barbarum polysaccharide molecule is located is 1633.79 cm⁻¹. -1 The wavelength corresponds to the stretching vibration peak of C=O, at 1400.95 cm⁻¹. -1 The wavelength near the target wavelength is the vibrational absorption peak of CH, at 1063.49 cm⁻¹. -1The strong absorption peak at 3434.76 cm⁻¹ belongs to the asymmetric vibration of COC or COH on the sugar ring, which is a characteristic absorption peak of pyranose. Overall, the parameters and shapes of the two are quite similar, indicating that zinc chelation did not destroy the basic structure of Lycium barbarum polysaccharides. Furthermore, after zinc chelation, the original absorption peak at 3434.76 cm⁻¹... -1 and 1063.49cm -1 The peaks at that location redshifted to 3489.6 cm⁻¹. -1 and 1113.81cm -1 The presence of this peak indicates a red shift in the absorption peaks after compounding; the wolfberry polysaccharide-zinc complex reaches a peak at 618.24 cm⁻¹. -1 The appearance of new sharp absorption peaks is caused by the bending vibration of Zn-O bonds. The changes in peak shape and the formation of new absorption peaks indicate that a complex has been formed between zinc ions and wolfberry polysaccharides, proving the successful preparation of this invention.

[0073] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a Lycium barbarum polysaccharide-zinc complex, characterized in that, The method described: S1: Dissolve 90-99% pure Lycium barbarum polysaccharide in 1-1.5 mol / L HCl solution, heat in a water bath at 90-100℃ for 10-20 min, adjust the pH to 7 with 6-8 mol / L NaOH to obtain a neutral solution, cool, then add anhydrous ethanol and let stand at 4℃ for 6-12 h, finally centrifuge at 5000-10000 rpm and dry at 60-80℃ to obtain incompletely hydrolyzed Lycium barbarum polysaccharide with a weight-average molecular weight of 3000-4500 Da; the ratio of Lycium barbarum polysaccharide to HCl solution is 1-5 g: 50 mL, and the volume ratio of anhydrous ethanol to neutral solution is 3-4: 1; S2: Dissolve the incompletely hydrolyzed Lycium barbarum polysaccharide obtained in S1 in distilled water to obtain a Lycium barbarum polysaccharide solution; the concentration of the incompletely hydrolyzed Lycium barbarum polysaccharide solution is 8~12 g / L; the volume ratio of the Lycium barbarum polysaccharide solution in S2 to the ZnSO4 solution in S3 is 1:1~2; S3: Adjust the pH of the Lycium barbarum polysaccharide solution in S2 using 0.01~0.03mol / L dilute sulfuric acid solution. After heating in a water bath to 50~80℃, add 0.1~0.2mol / L ZnSO4 solution dropwise with stirring. After sonication, stir for 2.5~3.5h. After cooling, obtain the reaction solution. Add anhydrous ethanol to the reaction solution and let it stand at 4℃ for 6~12h. Finally, centrifuge at 5000~10000rpm for 5~10min and dry at 60~80℃ to obtain the Lycium barbarum polysaccharide-zinc complex. The pH value is 5~6; the ultrasonic power is 120~360W; the ultrasonic time is 5~10min; and the volume ratio of anhydrous ethanol to the reaction solution is 3~4:

1.

2. The Lycium barbarum polysaccharide-zinc complex prepared by the method described in claim 1, characterized in that, The zinc ion chelation rate in the wolfberry polysaccharide-zinc complex is 95-98%, and the zinc ion content is 28-35%.

3. The application of the Lycium barbarum polysaccharide-zinc complex according to claim 2 in zinc supplements.

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