Dendrobium polysaccharide iron chelate and preparation method thereof

Abstract

The invention relates to the technical field of biological medicines, and discloses a dendrobium polysaccharide iron chelate and a preparation method thereof. Dendrobium polysaccharide is proved to have various effects of enhancing immunity, protecting stomach and intestine, regulating blood sugar, improving cardiovascular health, resisting aging, protecting liver, resisting fatigue, promoting bone health and the like, the dendrobium polysaccharide is used as a carrier of an iron element, and the iron element is successfully loaded on the dendrobium polysaccharide through plasma treatment, so that the preparation method is simple, and the cost is low. The dendrobium polysaccharide iron chelate is prepared. Compared with a traditional iron supplement, the method for loading the iron element has the advantages of being small in molecular weight and easy to absorb, has high bioavailability and can have good application value in the fields of food, medicine and the like.

Description

Technical Field

[0001] The present invention relates to the field of biomedical technologies, and particularly to a dendrobium polysaccharide iron chelate and a preparation method thereof. Background Art

[0002] Iron deficiency anemia (IDA) is a common nutritional deficiency disorder, mainly manifested as symptoms such as fatigue, dizziness, and pale complexion. In the treatment and prevention of IDA, oral iron supplements are necessary. Although ferrous salts are effective, they have certain side effects on the gastrointestinal tract, such as diarrhea, upper abdominal pain, constipation, etc. Therefore, it is necessary to develop iron supplements with low or no toxicity and side effects.

[0003] In the prior art, iron ions are often loaded by bioactive peptides to prepare iron-chelated peptides as iron supplements. By using bioactive peptides to load iron, on the one hand, the polypeptide can transport the loaded iron to the organism to promote intestinal iron transport and absorption, and on the other hand, the biological activity can endow the iron supplement with more functions.

[0004] For example, Chinese Patent with publication number CN119039415A discloses a milk source phosphorylated peptide and its application in the preparation of an iron supplement. This patent significantly increases the iron transport amount in the Caco-2 small intestinal epithelial cell model through the specific binding of the milk source phosphorylated peptide to ferrous ions and its strong chelating ability with iron, thereby enabling the iron-chelated peptide to have good activity in enhancing intestinal iron absorption.

[0005] The problems existing in using polypeptide to load iron element as an iron supplement in the prior art CN119039415A include: although using polypeptide to load iron element can increase the iron transport amount to a certain extent, due to the relatively large molecular weight of most polypeptides, the absorption effect of the iron supplement based on polypeptide-loaded iron element by organisms is poor, and the iron supplement effect on organisms is limited. Therefore, more iron element carriers and more iron supplements need to be found to meet people's needs. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a dendrobium polysaccharide iron chelate and a preparation method thereof.

[0007] The specific technical solution of the present invention is as follows: In the first aspect, the present invention provides a preparation method of a dendrobium polysaccharide iron chelate, which is characterized by comprising the following steps: Step S1: Perform plasma treatment on dendrobium polysaccharide; Step S2: Mix the plasma-treated dendrobium polysaccharide with iron ions, stir and process, and purify to obtain the dendrobium polysaccharide iron chelate.

[0008] In the present invention, polysaccharides from Dendrobium officinale are used as carriers for iron elements. Through plasma treatment, iron elements are successfully loaded onto polysaccharides from Dendrobium officinale, and a polysaccharide-iron chelate of Dendrobium officinale is prepared. The plasma treatment has the following three functions: First, it can reduce the molecular weight of polysaccharides from Dendrobium officinale, causing depolymerization, improving its solubility and fluidity, and thus increasing its contact area with metal ions; Second, it promotes the cross-linking of polysaccharides to form a three-dimensional structure, improving its selective chelating ability for specific metal ions and enhancing the chelating force; Third, by reducing the molecular weight of polysaccharides from Dendrobium officinale, the particle size of the obtained polysaccharide-iron chelate of Dendrobium officinale is reduced, making it easily absorbed by organisms.

[0009] The method for loading iron elements in the present invention has the characteristics of small molecular weight and easy absorption compared with traditional iron supplements, and has a high bioavailability.

[0010] As a preference of the above preparation method, the plasma treatment method is as follows: Place polysaccharides from Dendrobium officinale in a plasma device, use air as the treatment gas, and adjust the treatment voltage to 100 ± 1 V and the treatment current to 1 ± 0.1 A. For example, the plasma device can be a dielectric barrier discharge (DBD) plasma device.

[0011] As a preference of the above preparation method, the treatment time of the plasma treatment is 2 - 15 minutes.

[0012] As a preference of the above preparation method, sodium citrate is further added to the mixture obtained by mixing. Sodium citrate can promote the chelation of iron ions with polysaccharides from Dendrobium officinale.

[0013] As a preference of the above preparation method, the amount of sodium citrate added to the mixture obtained by mixing is such that the mass ratio of polysaccharides from Dendrobium officinale to sodium citrate is 1:(1 - 2).

[0014] The amount of iron ions added can be added according to the required iron-loading amount, and it can be added in excess and later removed by purification.

[0015] As a preference of the above preparation method, the pH of the mixture obtained by mixing is adjusted to 8.0 - 9.0.

[0016] As a preference of the above preparation method, the temperature of the stirring treatment is 45 - 55 °C and the time is 1 - 3 h.

[0017] As a preference of the above preparation method, the purification method is as follows: Centrifuge the substance obtained by the stirring treatment, dialyze the supernatant obtained by centrifugation with a dialysis bag with a cut-off molecular weight of 2000 Da, collect the retentate and mix it with absolute ethanol, then centrifuge, collect the precipitate, dissolve it in water to obtain a solution, and freeze-dry the obtained solution to obtain the polysaccharide-iron chelate of Dendrobium officinale.

[0018] In a second aspect, the present invention provides a polysaccharide iron chelate of Dendrobium officinale.

[0019] In a third aspect, the present invention provides an application of the polysaccharide iron chelate of Dendrobium officinale in the preparation of an iron supplement.

[0020] Compared with the prior art, the present invention has the following technical effects: (1) By treating the polysaccharide of Dendrobium officinale with plasma, the polysaccharide of Dendrobium officinale can be loaded with more iron elements and has strong iron chelating ability.

[0021] (2) The polysaccharide iron chelate of Dendrobium officinale prepared by the present invention has a small molecular weight and a small particle size, and can have high solubility and absorption rate in vivo, and high bioavailability.

[0022] (3) The polysaccharide of Dendrobium officinale has been proven to have various effects such as enhancing immunity, protecting the gastrointestinal tract, regulating blood sugar, improving cardiovascular health, anti-aging, protecting the liver, anti-fatigue and promoting bone health. The preparation method of the present invention is simple, and on the basis of ensuring the basic effects of the polysaccharide of Dendrobium officinale, a large iron element loading amount and high bioavailability can be ensured. The preparation method of the present invention can have good application value in the fields of food, medicine and the like. Description of the Drawings

[0023] Figure 1 is the particle size distribution diagram of the polysaccharide iron chelate of Dendrobium officinale with and without plasma treatment; Figure 2 is the UV spectrogram of the polysaccharide iron chelate of Dendrobium officinale with and without plasma treatment; Figure 3 is the FT-IR spectrogram of the polysaccharide iron chelate of Dendrobium officinale with and without plasma treatment; Figure 4 is the SEM diagram of the polysaccharide of Dendrobium officinale, the polysaccharide iron chelate obtained in Example 1 and Comparative Example 1; Figure 5 is the SEM diagram of the polysaccharide iron chelate obtained in Example 2, Example 3 and Example 4. Detailed Embodiments

[0024] The present invention will be further described below in conjunction with the embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are usually only a part of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art without creative efforts based on the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0025] In the embodiments of the present invention, the iron content in polysaccharide iron chelate of Dendrobium officinale is determined by o-phenanthroline ultraviolet spectrophotometry; the stability of iron ions under acidic and alkaline conditions is used as an evaluation index; particle size measurement technology is used to evaluate the particle size of polysaccharide iron chelate of Dendrobium officinale; Fourier transform infrared spectroscopy (FT-IR) is used to analyze the binding mode between iron ions and polysaccharide in polysaccharide iron chelate of Dendrobium officinale; scanning electron microscopy (SEM) is used to observe the microscopic morphology of polysaccharide iron chelate of Dendrobium officinale.

[0026] In the present invention, the polysaccharide of Dendrobium officinale used as the raw material can be obtained by conventional extraction techniques from Dendrobium officinale, such as the following methods: (1) Extraction: Weigh 10 g of Dendrobium officinale powder, add pure water according to a ratio of 1:100 (g:mL), heat to 80 °C for extraction for 4 hours, and then return to room temperature. Centrifuge the extract at 4000 rpm for 20 min, and collect the supernatant.

[0027] (2) Alcohol precipitation: Add 95% ethanol to the supernatant collected above, and the added ratio is: That is, add 986.8 mL of 95% ethanol to 1727 mL of supernatant. After mixing, perform alcohol precipitation, let it stand overnight (12 hours), centrifuge at 4000 rpm for 20 min the next day, and collect the precipitate. Redissolve the precipitate with pure water and freeze-dry to obtain polysaccharide of Dendrobium officinale.

[0028] In the embodiments of the present invention, the polysaccharide of Dendrobium officinale prepared by the above method is used as the raw material. In addition, the raw material polysaccharide of Dendrobium officinale of the present invention can also be obtained by other existing technologies or is the polysaccharide of Dendrobium officinale sold on the market.

[0029] In the embodiments of the present invention, sodium hydroxide or / and hydrochloric acid are used to adjust the pH of the system.

[0030] Example 1 Dissolve polysaccharide of Dendrobium officinale (DOP) in water to prepare an aqueous solution of polysaccharide of Dendrobium officinale with a concentration of 1 mg / mL (the concentration is 0.1%). Place the aqueous solution of polysaccharide of Dendrobium officinale in a dielectric barrier discharge (DBD) plasma device for treatment. The treatment parameters are: treatment voltage 100 V, treatment current 1 A, treatment time 2 min, and the treatment gas is air. Add 1 mL of FeCl with a concentration of 2 M to the aqueous solution of polysaccharide of Dendrobium officinale after plasma treatment. 3 ·6H 2The O solution was added with 0.2% sodium citrate and mixed evenly to obtain a mixed solution. The pH of the mixed solution was adjusted to 8.5 with sodium hydroxide and hydrochloric acid. The mixed solution was heated in a water bath to 50 °C and stirred for 2 hours, then centrifuged at 4000 r for 10 minutes. The supernatant was taken for dialysis, and the dialysis was carried out through a dialysis bag with a molecular weight cut-off of 2000 Da. The retentate in the dialysis bag was collected, added with 4 times the volume of absolute ethanol, mixed evenly, centrifuged at 4000 r for 10 minutes, the precipitate was collected and redissolved in water to obtain a solution, and the obtained solution was freeze-dried to obtain polysaccharide iron chelate of Dendrobium officinale.

[0031] Example 2 Compared with Example 1, the difference is that the plasma treatment time is 5 min. The following steps were carried out: Dendrobium officinale polysaccharide (DOP) was dissolved in water to prepare an aqueous solution of Dendrobium officinale polysaccharide with a concentration of 1 mg / mL (the concentration was 0.1%). The aqueous solution of Dendrobium officinale polysaccharide was placed in a dielectric barrier discharge (DBD) plasma device for treatment. The treatment parameters were: treatment voltage 100 V, treatment current 1 A, treatment time 10 min, and the treatment gas was air. 1 mL of FeCl with a concentration of 2 M was added to the aqueous solution of Dendrobium officinale polysaccharide after plasma treatment 3 ·6H 2 The O solution was added with 0.2% sodium citrate and mixed evenly to obtain a mixed solution. The pH of the mixed solution was adjusted to 8.5 with sodium hydroxide and hydrochloric acid. The mixed solution was heated in a water bath to 50 °C and stirred for 2 hours, then centrifuged at 4000 r for 10 minutes. The supernatant was taken for dialysis, and the dialysis was carried out through a dialysis bag with a molecular weight cut-off of 2000 Da. The retentate in the dialysis bag was collected, added with 4 times the volume of absolute ethanol, mixed evenly, centrifuged at 4000 r for 10 minutes, the precipitate was collected and redissolved in water to obtain a solution, and the obtained solution was freeze-dried to obtain polysaccharide iron chelate of Dendrobium officinale.

[0032] Example 3 Compared with Example 1, the difference is that the plasma treatment time is 10 min. The following steps were carried out: Dendrobium officinale polysaccharide (DOP) was dissolved in water to prepare an aqueous solution of Dendrobium officinale polysaccharide with a concentration of 1 mg / mL (the concentration was 0.1%). The aqueous solution of Dendrobium officinale polysaccharide was placed in a dielectric barrier discharge (DBD) plasma device for treatment. The treatment parameters were: treatment voltage 100 V, treatment current 1 A, treatment time 10 min, and the treatment gas was air. 1 mL of FeCl with a concentration of 2 M was added to the aqueous solution of Dendrobium officinale polysaccharide after plasma treatment 3 ·6H 2The O solution was added with 0.2% sodium citrate and mixed evenly to obtain a mixed solution. The pH of the mixed solution was adjusted to 8.5 with sodium hydroxide and hydrochloric acid. The mixed solution was heated in a water bath to 50 °C and stirred for 2 hours, then centrifuged at 4000 r for 10 minutes. The supernatant was taken for dialysis, and the dialysis was carried out through a dialysis bag with a molecular weight cut-off of 2000 Da. The retentate in the dialysis bag was collected, added with 4 times the volume of absolute ethanol, mixed evenly, centrifuged at 4000 r for 10 minutes, the precipitate was collected and redissolved with water to obtain a solution, and the obtained solution was freeze-dried to obtain polysaccharide iron chelate of dendrobium officinale.

[0033] Example 4 Compared with Example 1, the difference is that the plasma treatment time is 15 min. The following steps were carried out: Dendrobium officinale polysaccharide (DOP) was dissolved in water to prepare an aqueous solution of dendrobium officinale polysaccharide with a concentration of 1 mg / mL (the concentration was 0.1%). The aqueous solution of dendrobium officinale polysaccharide was placed in a dielectric barrier discharge (DBD) plasma device for treatment. The treatment parameters were: treatment voltage 100 V, treatment current 1 A, treatment time 15 min, and the treatment gas was air. 1 mL of a 2 M FeCl 3 ·6H 2 O solution was added, and 0.2% sodium citrate was added and mixed evenly to obtain a mixed solution. The pH of the mixed solution was adjusted to 8.5 with sodium hydroxide and hydrochloric acid. The mixed solution was heated in a water bath to 50 °C and stirred for 2 hours, then centrifuged at 4000 r for 10 minutes. The supernatant was taken for dialysis, and the dialysis was carried out through a dialysis bag with a molecular weight cut-off of 2000 Da. The retentate in the dialysis bag was collected, added with 4 times the volume of absolute ethanol, mixed evenly, centrifuged at 4000 r for 10 minutes, the precipitate was collected and redissolved with water to obtain a solution, and the obtained solution was freeze-dried to obtain polysaccharide iron chelate of dendrobium officinale.

[0034] Example 5 Dendrobium officinale polysaccharide (DOP) was dissolved in water to prepare an aqueous solution of dendrobium officinale polysaccharide with a concentration of 1 mg / mL (the concentration was 0.1%). The aqueous solution of dendrobium officinale polysaccharide was placed in a dielectric barrier discharge (DBD) plasma device for treatment. The treatment parameters were: treatment voltage 101 V, treatment current 0.9 A, treatment time 2 min, and the treatment gas was air. 1 mL of a 2 M FeCl 3 ·6H 2Dissolve the polysaccharide from Dendrobium officinale (DOP) in water to prepare an aqueous solution of polysaccharide from Dendrobium officinale with a concentration of 1 mg / mL (the concentration is 0.1%). Add 0.1% sodium citrate to the solution and mix well to obtain a mixed solution. Adjust the pH of the mixed solution to 8.0 with sodium hydroxide and hydrochloric acid. Heat the mixed solution in a water bath to 45 °C and stir for 3 hours, then centrifuge at 4000 r for 10 minutes. Take the supernatant for dialysis, and the dialysis is carried out through a dialysis bag with a molecular weight cut-off of 2000 Da. Add 4 volumes of absolute ethanol to the retained substance in the dialysis bag, mix well, centrifuge at 4000 r for 10 minutes, collect the precipitate, redissolve it in water to obtain a solution, and freeze-dry the obtained solution to obtain the polysaccharide-iron chelate of Dendrobium officinale.

[0035] Example 6 Dissolve the polysaccharide from Dendrobium officinale (DOP) in water to prepare an aqueous solution of polysaccharide from Dendrobium officinale with a concentration of 1 mg / mL (the concentration is 0.1%). Place the aqueous solution of polysaccharide from Dendrobium officinale in a dielectric barrier discharge (DBD) plasma device for treatment. The treatment parameters are: treatment voltage 99 V, treatment current 1.1 A, treatment time 2 min, and the treatment gas is air. Add 1 mL of a 2 M FeCl 3 ·6H 2 O solution, and add 0.2% sodium citrate, mix well to obtain a mixed solution. Adjust the pH of the mixed solution to 9.0 with sodium hydroxide and hydrochloric acid. Heat the mixed solution in a water bath to 55 °C and stir for 1 hour, then centrifuge at 4000 r for 10 minutes. Take the supernatant for dialysis, and the dialysis is carried out through a dialysis bag with a molecular weight cut-off of 2000 Da. Add 4 volumes of absolute ethanol to the retained substance in the dialysis bag, mix well, centrifuge at 4000 r for 10 minutes, collect the precipitate, redissolve it in water to obtain a solution, and freeze-dry the obtained solution to obtain the polysaccharide-iron chelate of Dendrobium officinale.

[0036] Comparative Example 1 Compared with Example 1, the difference is that no plasma treatment is carried out. The following steps are carried out: Dissolve the polysaccharide from Dendrobium officinale (DOP) in water to prepare an aqueous solution of polysaccharide from Dendrobium officinale with a concentration of 1 mg / mL (the concentration is 0.1%). Add 1 mL of a 2 M FeCl 3 ·6H 2 O solution, and add 0.2% sodium citrate, mix well to obtain a mixed solution. Adjust the pH of the mixed solution to 8.5 with sodium hydroxide and hydrochloric acid. Heat the mixed solution in a water bath to 50 °C and stir for 2 hours, then centrifuge at 4000 r for 10 minutes. Take the supernatant for dialysis, and the dialysis is carried out through a dialysis bag with a molecular weight cut-off of 2000 Da. Add 4 volumes of absolute ethanol to the retained substance in the dialysis bag, mix well, centrifuge at 4000 r for 10 minutes, collect the precipitate, redissolve it in water to obtain a solution, and freeze-dry the obtained solution to obtain a solid.

[0037] Performance Characterization Determination of Iron Content in Chelate Take the chelate polysaccharide solids obtained in Examples 1 to 4 and Comparative Example 1, and test the iron content therein by the phenanthroline method. The results are shown in Table 1. Further, dissolve the above chelate polysaccharide solids in deionized water to prepare dendrobium polysaccharide iron solutions, and use sodium hydroxide and acidic potassium ferrocyanide to detect the dendrobium polysaccharide iron solutions obtained in Examples 1 to 4 and Comparative Example 1. It is found that no reddish-brown precipitate and blue precipitate appear immediately in the solutions. This indicates that the structure of the dendrobium polysaccharide iron chelate is stable and does not contain free Fe 3+ .

[0038] Table 1 Group Iron content (%) Example 1 24.35±2.19 Example 2 30.63±0.35 Example 3 33.89±0.92 Example 4 27.40±1.42 Comparative Example 1 14.88±1.28 Determination of Chelate Particle Size Take the chelate polysaccharide solids obtained in Examples 1 to 4 and Comparative Example 1, and the raw material dendrobium polysaccharide, and test their particle sizes. The results are shown in Figure 1 , where DOP represents the raw material dendrobium polysaccharide, DOP-Fe(Ⅲ)2min represents Example 1, DOP-Fe(Ⅲ)5min represents Example 2, DOP-Fe(Ⅲ)10min represents Example 3, DOP-Fe(Ⅲ)15min represents Example 4, and DOP-Fe(Ⅲ) represents Comparative Example 1.

[0039] It can be seen from the particle size test results that the particle sizes of the dendrobium polysaccharide chelates (Examples 1 to 4, Comparative Example 1) are significantly smaller than those of the dendrobium polysaccharide. This indicates that the structure of the dendrobium polysaccharide itself is relatively loose and the degree of crosslinking is large, so it is characterized by a large particle size; in the process of forming a chelate with iron ions, the strength of the coordination effect is greater than the intermolecular force, thus forming a denser structure, resulting in a smaller particle size. From Example 1 to Example 4, compared with the dendrobium polysaccharide iron chelate in Comparative Example 1, the iron content increases significantly, which can greatly enhance the strength of the coordination effect in the chelate. Therefore, Examples 1 to 4 are characterized by smaller particle sizes. The reduction of particle size is beneficial to the digestion and absorption of molecules in the body. This indicates that the dendrobium polysaccharide iron chelate of the present invention is expected to have high solubility and absorption rate and high bioavailability in vivo.

[0040] Examples 1 to 4, the plasma treatment times were 2 min, 5 min, 10 min, and 15 min respectively. As the plasma treatment time became longer (the plasma treatment intensity gradually increased), the particle size change in Examples 1 to 4 showed a trend of first decreasing within 2 to 10 minutes and then increasing after 15 minutes. From the analysis of the particle size test results combined with the test results of iron content, the trend of the particle size first decreasing and then increasing was due to the combined effects of plasma treatment promoting iron chelation and plasma treatment promoting polysaccharide molecular depolymerization. Specifically, increasing the plasma treatment intensity would promote the cross-linking of polysaccharides to form a three-dimensional structure, thereby enhancing its selective chelating ability for specific metal ions and improving the chelating force, which was reflected in the gradually increasing iron content in Examples 1 to 3; under low-intensity plasma treatment, the polysaccharides of Dendrobium officinale could undergo depolymerization, reducing the molecular weight and particle size of the polysaccharides of Dendrobium officinale, which was reflected in the gradually decreasing particle size within 2 to 10 minutes in Examples 1 to 3; when the plasma treatment intensity was less than 10 min, for example, in Examples 1 to 3, as the plasma intensity increased, the polysaccharides cross-linked to form chelation sites, resulting in a gradual increase in iron content. However, at this time, under the dual effects of the particle size reduction caused by depolymerization and the particle size reduction caused by the increase in coordination strength, the particle size decreased with the increase in plasma treatment intensity within 2 to 10 minutes; but when the plasma treatment intensity exceeded 10 min, for example, under the 15-min plasma treatment in Example 4, at this time, the promoting polymerization and cross-linking effects caused by the increase in plasma intensity were the main ones, which would lead to an increase in the particle size of the chelate.

[0041] Determination of Chelate UV Take the chelate polysaccharide solids obtained in Examples 1 to 4 and Comparative Example 1, and take the raw material polysaccharides of Dendrobium officinale, and test their ultraviolet absorption spectra (UV, Ultraviolet spectrum). The results are shown in Figure 2 , where DOP represents the raw material polysaccharides of Dendrobium officinale, DOP-Fe(Ⅲ)2min represents Example 1, DOP-Fe(Ⅲ)5min represents Example 2, DOP-Fe(Ⅲ)10min represents Example 3, DOP-Fe(Ⅲ)15min represents Example 4, and DOP-Fe(Ⅲ) represents Comparative Example 1.

[0042] As Figure 2 shown, when scanning the chelate in the 200 - 600 nm wavelength band, the absorption peak near 300 nm was particularly prominent, and with the extension of the treatment time, the absorbance gradually increased, indicating an increase in absorbance, which might be caused by the formation of the complex or the coordination reaction. The absorbance value at 310 nm reflected the number of Fe-O bonds. The results showed that the polysaccharides of Dendrobium officinale (Examples 1 to 4) treated by plasma had more binding sites with iron ions.

[0043] Determination of Chelate by FT-IR Take the chelate polysaccharide solids obtained in Examples 1 to 4 and Comparative Example 1, and take the raw material Dendrobium officinale polysaccharide, and test their Fourier transform infrared spectra (FT-IR, Fourier Transform Infrared Spectroscopy). The results are shown in Figure 3 , where DOP represents the raw material Dendrobium officinale polysaccharide, DOP-Fe(Ⅲ) 2min represents Example 1, DOP-Fe(Ⅲ) 5min represents Example 2, DOP-Fe(Ⅲ) 10min represents Example 3, DOP-Fe(Ⅲ) 15min represents Example 4, and DOP-Fe(Ⅲ) represents Comparative Example 1.

[0044] As Figure 3 shown, a sharp absorption peak was formed near 680 nm in the chelate, which is also the characteristic absorption peak of the Fe-O bond, further indicating that the reaction between Dendrobium officinale polysaccharide and iron ions may involve the coordination effect and the rearrangement process of hydrogen bonds.

[0045] Observation of Chelate Morphology Use a scanning electron microscope (SEM) to observe the microscopic morphology of the chelate polysaccharide solids obtained in Examples 1 to 4 and Comparative Example 1, and take the raw material Dendrobium officinale polysaccharide. The results are shown in Figure 4 and Figure 5 , where DOP represents the raw material Dendrobium officinale polysaccharide, DOP-Fe(Ⅲ) 2min represents Example 1, DOP-Fe(Ⅲ) 5min represents Example 2, DOP-Fe(Ⅲ) 10min represents Example 3, DOP-Fe(Ⅲ) 15min represents Example 4, and DOP-Fe(Ⅲ) represents Comparative Example 1.

[0046] From Figure 4 and Figure 5 it can be seen that the structure of the Dendrobium officinale polysaccharide molecule itself is relatively loose and the degree of crosslinking is relatively large. In the chelates of Examples 1 to 4 and Comparative Example 1, obvious granular structures appeared. After plasma treatment (Examples 1 to 4), the chelates showed a more compact aggregated structure, indicating that the plasma treatment had an obvious effect on the microscopic structure of the chelates, which may enhance their stability and integrity.

[0047] The raw materials and equipment used in the present invention are all common raw materials and equipment in the art without special instructions; the methods used in the present invention are all conventional methods in the art without special instructions.

[0048] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a dendrobium polysaccharide iron chelate, characterized in that: The following steps are involved: Step S1: treating the dendrobium polysaccharide with plasma; Step S2: mixing the plasma-treated dendrobium polysaccharide with iron ions, stirring and purifying the mixture to obtain a dendrobium polysaccharide iron chelate.

2. The method for preparing a dendrobium polysaccharide iron chelate according to claim 1, characterized in that: The plasma treatment method is as follows: placing the dendrobium polysaccharide in a plasma device, using air as a treatment gas, adjusting the treatment voltage to 100±1V, and the treatment current to 1±0.1A.

3. A method for preparing a dendrobium polysaccharide iron chelate as claimed in claim 1 or 2, characterized in that: The plasma treatment time is 2 to 15 minutes.

4. The method for preparing a dendrobium polysaccharide iron chelate according to claim 1, characterized in that: Sodium citrate is also added to the mixture obtained by mixing.

5. A method for preparing a dendrobium polysaccharide iron chelate as claimed in claim 1 or 4, characterized in that: The amount of sodium citrate added to the mixture obtained by mixing is such that the mass ratio of dendrobium polysaccharide to sodium citrate is 1:(1~2).

6. A method for preparing a dendrobium polysaccharide iron chelate as claimed in claim 1 or 4, characterized in that: The pH of the mixture obtained by mixing is adjusted to 8.0-9.

0.

7. The method for preparing a dendrobium polysaccharide iron chelate according to claim 1, characterized in that: The stirring treatment is carried out at a temperature of 45-55°C and for a time of 1-3 h.

8. The method for preparing a dendrobium polysaccharide iron chelate according to claim 1, characterized in that: The purification method comprises the following steps: centrifuging the substance obtained by stirring, dialyzing the supernatant obtained by centrifugation with a dialysis bag with a molecular weight cutoff of 2000 Da, collecting the retentate and mixing it with anhydrous ethanol, then centrifuging it, collecting the precipitate and dissolving it in water to obtain a solution, and freeze-drying the obtained solution to obtain the dendrobium polysaccharide iron chelate.

9. The Dendrobium polysaccharide-iron chelate prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the dendrobium polysaccharide iron chelate prepared by the preparation method according to any one of claims 1 to 8 in the preparation of an iron supplement.

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