Hydroxymethionine chelate as well as preparation method and application thereof

Abstract

The invention discloses a methionine hydroxy chelate as well as a preparation method and application thereof, the chelate can be used for preparing animal feed additives and nutritional agents and is a dual-core chelating system, and a chelating structure A and a chelating structure B both comprise central iron ions and methionine hydroxy ligands; the central iron ion of the chelating structure A is connected with the carbonyl positive coordination of the methionine hydroxy ligand of the chelating structure B; the preparation method comprises the following steps: dissolving methionine hydroxyl to prepare a ligand neutralization solution; and S2, uniformly mixing the ligand neutralization solution with a ferrous chloride tetrahydrate solution, and completely reacting. The hydroxyl methionine iron chelate is high in stability, can maintain the biological activity of iron in a complex chyme environment, can avoid absorption antagonism with trace elements such as manganese and copper, optimizes the overall mineral utilization efficiency, remarkably improves the absorption rate of animals, is mild in preparation condition and controllable in cost, is compatible with an existing feed production line, and is good in industrialization prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of animal feed additives, in particular to a hydroxymethionine chelate and a preparation method and application thereof. Background Art

[0002] Iron is the largest trace element in the Earth's crust, mostly present in oxidized or salt form. Iron is also widely distributed throughout various tissues and organs and is essential for life.

[0003] Currently, inorganic iron salts (ferrous sulfate) are the mainstream iron nutritional supplement in the animal feed additive market. However, as animal feed additives, inorganic iron salts have unavoidable negative effects and even harm. Inorganic iron compounds such as FeSO4 are bound by ionic bonds and are unstable in the digestive tract and easily dissociated. The dissociated ionic iron is easily oxidized by other substances such as copper to trivalent iron, and reacts with Cl in the chyme. - or OH - Iron ions also combine with other substances, such as iron ions, to form insoluble Fe(OH)3 or FeCl3 precipitates, which impair absorption. Furthermore, the dissociated iron ions easily combine with antinutrients (such as phytic acid, tannic acid, and soluble cellulose), forming poorly absorbed macromolecules that are excreted in feces. This has a low digestibility and is harmful to the environment. Furthermore, due to the similarity in atomic structure between iron and manganese, ionic iron and manganese share absorption and transport pathways, resulting in a competitive inhibition relationship between the two.

[0004] To compensate for the lack of inorganic iron absorption, the following methods are generally used for improvement: ① Increasing the amount of inorganic iron added to compensate for the absorption problem, however, this method actually increases the metabolic burden on animals. ② Replacing inorganic iron salts with organic iron compounds. Existing organic iron compounds such as ferrous fumarate and ferrous glycinate are both organic iron compounds, but both exist as open-chain complexes. Not only are they easily soluble in the digestive tract, but they are also susceptible to the influence of polar molecules in the environment, causing most iron ions to dissociate easily. As a result, the iron ions are actually still present in an inorganic state, which still does not solve the above-mentioned shortcomings of inorganic iron salts. Summary of the Invention

[0005] The present invention provides a hydroxymethionine chelate with stable properties and high absorption rate, and a preparation method and application thereof, in order to solve the technical problems existing in the existing carbonization process mentioned in the background technology.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is: A hydroxymethionine iron chelate is a binuclear chelate system consisting of a chelate structure A and a chelate structure B. Both the chelate structure A and the chelate structure B include a central iron ion and a hydroxymethionine ligand. One central iron ion is simultaneously coordinated with the hydroxyl oxygen and carboxyl oxygen of two hydroxymethionine ligands to form a chelate structure having a double five-membered heterocyclic ring. The central iron ion of the chelate structure A is coordinated with the carbonyl cation of the hydroxymethionine ligand of the chelate structure B.

[0007] The present invention forms a dual-core system (the center of A) by interconnecting the chelate structures A and B. Coordinated with the carbonyl oxygen of ligand B), a rigid double five-membered heterocyclic network is constructed, which greatly improves the intramolecular cohesion and enhances the stability of the molecular structure, making it stable in feed and digestive tract; the stable chelated state within the molecule blocks → Oxidation pathways to avoid the formation of The double five-membered ring chelate bond (Fe-O carboxyl / hydroxyl) has a higher bond energy than the open chain complex, effectively resisting the impact of the polar environment in the digestive tract and effectively preventing the dissociation of iron ions. Chelated Fe²⁺ circulates through amino acid channels in a molecular state, avoiding the interaction with manganese ions ( ) ion channel competition to improve absorption efficiency.

[0008] As a further preferred embodiment of the above technical solution, the coordination number of the central iron ion in the chelate structure A and the chelate structure B is 6. The central iron ion in the chelate structure A is coordinated and connected with one water molecule, and the central iron ion in the chelate structure B is coordinated and connected with two water molecules.

[0009] As a further preferred embodiment of the above technical solution, the central iron ion is a divalent iron ion.

[0010] As a further preference of the above technical solution, the crystal space group of the hydroxymethionine chelate is P , the crystallographic parameters are shown in Table 1 below.

[0011] Table 1: Crystallographic parameters of hydroxymethionine chelates

[0012] Based on the same technical concept, the present invention also provides a method for preparing the above-mentioned hydroxymethionine iron chelate, comprising the following steps: S1. dissolving hydroxymethionine to prepare a ligand neutralization solution; S2. Evenly mix the ligand neutralization solution and the ferrous chloride tetrahydrate solution. After the reaction is complete, filter and obtain the hydroxymethionine iron chelate solution.

[0013] As a further preferred embodiment of the above technical solution, the pH of the ligand neutralization solution in S1 is 8-9.5, and the concentration is 1 mol / L.

[0014] As a further preferred embodiment of the above technical solution, the molar ratio of hydroxymethionine in the ligand neutralization solution in S2 to ferrous chloride tetrahydrate in the ferrous chloride tetrahydrate solution is 10:(5~7).

[0015] As a further preferred embodiment of the above technical solution, after obtaining the solution of the hydroxymethionine iron chelate in S2, an equal volume of anhydrous ethanol is slowly added dropwise to the solution of the hydroxymethionine iron chelate, and the solution is allowed to stand and diffuse to obtain needle-shaped transparent crystals.

[0016] Based on the same technical concept, the present invention also provides an application of the above-mentioned hydroxymethionine iron chelate, which can be used to prepare animal feed additives or animal nutrients.

[0017] The present invention has the following beneficial effects: The hydroxymethionine iron chelate of the present invention is highly stable, with a closed chelate structure that resists binding by phytic acid, tannic acid, and other substances. This allows it to maintain the biological activity of iron in the complex environment of chyme. When used as an additive, it avoids absorption antagonism with trace elements such as manganese and copper, optimizing overall mineral utilization efficiency and significantly improving animal absorption. The binuclear chelate structure nearly completely blocks the dissociation of iron ions in the digestive tract, significantly reducing the amount of iron added to feed. The high absorption rate directly reduces fecal iron excretion, lowering the risk of heavy metal contamination in soil and water bodies while also avoiding oxidative stress in the animal liver and kidneys caused by excessive inorganic iron addition, thereby reducing the metabolic burden. Furthermore, the mild aqueous synthesis process (which does not require organic solvents or high temperature and pressure) ensures cost control and compatibility with existing feed production lines, promising promising prospects for industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the molecular structure of the hydroxymethionine iron chelate of Example 1.

[0019] Figure 2 Schematic diagram of the molecular arrangement inside the crystal of the hydroxymethionine iron chelate of Example 1.

[0020] Figure 3 This is the Hirshfeld surface analysis result of the hydroxymethionine iron chelate of Example 1.

[0021] Figure 4 This is the fingerprint of each force in the hydroxymethionine iron chelate of Example 1. DETAILED DESCRIPTION

[0022] The present invention will be described in detail below with reference to the embodiments thereof, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0023] Example 1: like Figure 1 As shown ( Figure 1 In the embodiment, the hydroxymethionine iron chelate is a binuclear chelate system consisting of a chelate structure A and a chelate structure B. Both the chelate structure A and the chelate structure B include a central iron ion (ferrous iron ion) and a hydroxymethionine ligand. One central iron ion is simultaneously coordinated with the hydroxyl oxygen and carboxyl oxygen of the two hydroxymethionine ligands to form a chelate structure having a double five-membered heterocyclic ring. The central iron ion of the chelate structure A is coordinated with the carbonyl positive of the hydroxymethionine ligand of the chelate structure B. The coordination number of the central iron ion in the chelate structure A and the chelate structure B is 6. The remaining coordination position of the central iron ion of the chelate structure A is occupied by one water molecule, and the remaining coordination position of the central iron ion of the chelate structure B is occupied by two water molecules.

[0024] The single crystal X-ray diffraction structure of the hydroxymethionine iron chelate of this embodiment was determined at 200 K. The diffraction data showed that the hydroxymethionine ferrous chelate crystallized at P The central metal ion, Fe(II), successfully binds to the MHA ligand via a coordination bond. The main crystallographic parameters and bond lengths are shown in Tables 2 and 3. Two Fe(II) ions bind to four deprotonated MHA molecules and three water molecules to form a neutral binuclear chelate complex. A solvent molecule bridges the coordinated water ions with the carbonyl oxygen of the ligand via intermolecular hydrogen bonding. Intramolecular hydrogen bonding also exists between the coordinated water ions and the carboxyl oxygen of the chelate complex. Therefore, the single crystal chelate formula of ferrous hydroxymethionine is [Fe2(MHA)4(H2O)3]. The four MHA molecules, with the hydroxyl oxygen and the deprotonated carboxyl oxygen as coordination sites, bind to Fe1(II) and Fe2(II) in pairs in a bidentate chelate coordination configuration. The remaining Fe1(II) sites are occupied by one coordinated water molecule and the carbonyl oxygen of the third MHA molecule, while the remaining Fe2(II) sites are occupied by two coordinated water molecules. Both metal ion centers exhibit a hexacoordinated octahedral configuration. The average bond length of Fe1-O (carboxyl oxygen) is 2.08 Å, the bond length of Fe1-O (oxygen in water) is 2.139(7) Å, and the octahedral distortion parameter of Fe1(II) is 77.5(10)°; the average bond length of Fe2-O (carboxyl oxygen) is 2.12 Å, the average bond length of Fe2-O (oxygen in water) is 2.07 Å, and the octahedral distortion parameter of Fe2(II) is 74.7(10)°, indicating that the degree of distortion of the two metal centers from the regular octahedron is small, and the coordination geometry is relatively regular. Due to the participation of the carbonyl oxygen of the third MHA molecule in the coordination, the octahedral distortion parameter of Fe1(II) is slightly larger than that of Fe2(II).

[0025] The supramolecular structure analysis of the hydroxymethionine iron chelate of this embodiment is as follows: Figure 2 As shown ( Figure 2 a is the side view of the two-dimensional layer, Figure 2 b is the top view of the two-dimensional layer, Figure 3 (c) The green box indicates the C···HC forces between layers. Each coordinated water molecule and the hydroxyl and carboxyl oxygen groups in the MHA ligand participate in hydrogen bonding, linking the molecules into a two-dimensional supramolecular layered structure. Not only are there abundant hydrogen bonds within the layers (average O···O distance of approximately 2.65 Å), but the interlayer C···HC forces (average C···C distance of approximately 3.40 Å) are also strong, demonstrating strong local order.

[0026] Hirshfeld surface analysis technique was used to further analyze the interaction between molecules. Figure 3 and Figure 4 As shown, Figure 3 provides an overall picture of the intermolecular interactions ( Figure 3 a is the ball-and-stick model of hydroxymethionine iron chelate, Figure 3 b is the Hirshfeld surface model of hydroxymethionine iron chelate. Figure 3 c is the overall fingerprint), Figure 4 Describes the fingerprint of each force ( Figure 4 (The outline of the overall fingerprint is shown in gray in the figure). Strong O···H contacts are present in the hydroxymethionine iron chelate, accounting for 29.5% of the total Hirshfeld surface area, indicating a strong role for hydrogen bonding between the molecules, consistent with single crystal structural analysis. The fingerprint also shows that due to the dense molecular arrangement, H···H interactions are more prominent, accounting for 56% of the total Hirshfeld surface area. S···H interactions account for 12.2%, and the remaining 2.3% is composed of C···H, C···O, and other interactions.

[0027] Table 2: Crystal parameters of the hydroxymethionine iron chelate of Example 1

[0028] Table 3: Structural parameters such as coordination bond length, bond angle, etc. of the hydroxymethionine iron chelate of Example 1

[0029] The preparation method of the hydroxymethionine iron chelate of this embodiment comprises the following steps: S1. Dissolve 88 wt% hydroxymethionine in an appropriate amount of water and adjust the pH thereof to about 9 with a 2 mol / L sodium hydroxide solution to prepare a ligand neutralization solution with a concentration of 1 mol / L.

[0030] S2. Take 10 mL of the neutralized solution (10 mmol) and mix it evenly with 10 mL of ferrous chloride tetrahydrate aqueous solution (6 mmol) to obtain a yellow-green turbid solution. Filter through a 10 mm filter to obtain a green and clear solution of hydroxymethionine ferrous chelate (MHA-Fe(II)).

[0031] S3. Place the ferrous hydroxymethionine chelate solution in a test tube and slowly add an equal volume of anhydrous ethanol dropwise. Allow to stand for diffusion. After three to four days, needle-shaped transparent crystals will grow on the test tube wall, with a yield of approximately 60%.

[0032] The hydroxymethionine iron chelate of this embodiment can be used to prepare animal feed additives or animal nutrients.

[0033] The following is the test content for verifying the positive effect of the hydroxymethionine iron chelate in this example as an animal feed additive: 1.1 Test sample This study was conducted at the Xingyue Tianhua Experimental Research Center pig farm in Changsha County, Hunan Province. Fourteen 35-day-old weaned pigs weighing (8.71 ± 0.11) kg were randomly divided into two groups, with seven replicates per group and one piglet per replicate. The control group received 100 mg / kg of ferrous sulfate (calculated as iron) supplemented to the basal diet, while the hydroxymethionine iron group received 70 mg / kg of hydroxymethionine iron (calculated as iron) supplemented to the basal diet. The experimental period lasted 21 days.

[0034] 1.2 Experimental diet This experiment used a corn-soybean meal basal diet, and its nutritional level was based on the Nutrient Requirements of Pigs (GB / T39235-2020). The composition and nutritional level of the experimental basal diet are shown in Table 4: Table 4: Composition and nutrient levels of experimental diets

[0035] Note: [1] Multivitamin and multimineral premix provides per kilogram of feed: Cu 115 mg, Zn 65 mg, Mn 40 mg, Se0.25 mg, I 1.2 mg, Cr 0.2 mg, VA 9 500 IU, VD3 3 000 IU, VK3 3 mg, VE 24 mg, VB13.6 mg, VB2 7.5 mg, VB6 3 mg, VB12 0.02 mg, D-biotin 0.12 mg, D-pantothenic acid 15 mg, folic acid 1.5 mg, niacinamide 30 mg.

[0036] 【2】Nutrient levels are calculated values.

[0037] 1.3 Sample collection and measurement indicators 1.3.1 Growth performance During the experiment, feed consumption and fasting weight of pigs were recorded every week, and indicators such as average daily weight gain, average daily feed intake, and feed-to-weight ratio were calculated.

[0038] Note: Average daily weight gain = (final weight - initial weight) / number of test days; Average daily feed intake = total feed intake / number of experimental days; Feed-to-weight ratio = average daily feed intake / average daily weight gain.

[0039] 1.3.2 Routine blood indicators On the morning of the 7th day and the end of the experiment, 7 piglets in each group were selected for blood sampling from the anterior vena cava. Blood was collected using anticoagulant tubes and non-anticoagulant tubes. The blood in the non-anticoagulant tube was allowed to stand at room temperature for 30 minutes for stratification, and then centrifuged at 3000 r / min for 15 minutes to obtain the supernatant for testing. The blood in the anticoagulant tube was measured using a Mindray veterinary fully automatic blood cell analyzer (Shenzhen Mindray Medical) to measure indicators such as white blood cells, red blood cells, hemoglobin, mean hematocrit, red blood cell distribution width, and red blood cell volume.

[0040] 1.3.3 Iron absorption and metabolism indicators Serum iron content, ferroportin, ferritin, hepcidin, ceruloplasmin, transferrin, and apotransferrin were measured using a microplate reader (Thermo Fisher Scientific, Germany) according to the instructions of the ELISA kit.

[0041] 1.3.4 Antioxidant index Serum glutathione peroxidase (GSH-Px), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were measured using an ELISA kit (Thermo Fisher Scientific, Germany) according to the kit instructions. All kits were purchased from Nanjing Jiancheng Bioengineering Co., Ltd.

[0042] 1.3.5 Inflammatory Factor Indicators Serum levels of IL-1β, IL-6, and TNF-α were measured using an ELISA reader (Thermo Fisher Scientific, Germany) according to the ELISA kit instructions. The kits were purchased from Wuhan Huamei Bioengineering Co., Ltd.

[0043] 1.4 Data Processing The experimental data were compared with the T-test in SPSS 26.0 software to compare the differences between the two groups, and the results were expressed as mean and standard deviation. P <0.05 indicated significant differences.

[0044] 2 Results 2.1 Effects of hydroxymethionine iron on growth performance of weaned piglets As shown in Table 5 below, there were no significant differences in average daily feed intake, average daily weight gain, final weight, and feed-to-meat ratio between the hydroxymethionine iron group and the control group ( P >0.05).

[0045] Table 5: Effects of hydroxymethionine iron on growth performance of weaned piglets

[0046] Note: Data in the same column with the same letter or no letter indicate no significant difference ( P >0.05), different letters indicate significant differences ( P <0.05); the same as in the table below.

[0047] Average daily weight gain, average daily feed intake and feed-to-weight ratio are important indicators for measuring animal growth performance. The results of this experiment showed that adding hydroxymethionine iron to the feed had no negative impact on the growth performance of weaned piglets. At the same time, the average daily feed intake increased by 9.28%, indicating that hydroxymethionine iron can improve the palatability of feed.

[0048] 2.2 Effects of hydroxymethionine iron on routine blood parameters in weaned piglets As shown in Table 6 below, compared with the control group, the number of red blood cells, hemoglobin and hematocrit in the hydroxymethionine iron group showed an upward trend (0.05< P< 0.10), but the differences in white blood cell count, mean corpuscular volume, mean hemoglobin concentration, and red blood cell distribution width were not significant ( P >0.05).

[0049] Table 6: Effects of hydroxymethionine iron on routine blood parameters in weaned piglets

[0050] Red blood cell count, hematocrit, and hemoglobin concentration are important indicators for assessing iron status in pigs. Hematocrit refers to the percentage of whole blood volume occupied by blood, and its value is closely related to red blood cell count and size. Hemoglobin content assesses the body's ability to digest and absorb iron and is also a key indicator for determining anemia. Under normal circumstances, the hemoglobin concentration in piglets ranges from 100 to 120 g / L. When the hemoglobin concentration falls below the lower limit of the normal range, the piglet may be anemic. This study found that compared with the control group, the red blood cell count, hemoglobin, and hematocrit in the hydroxymethionine iron group increased. While the hemoglobin levels in the control group were below 100 g / L, indicating iron deficiency, the hemoglobin levels in the hydroxymethionine iron group remained within the normal range, indicating that hydroxymethionine iron improved the piglets' hematopoietic function.

[0051] 2.3 Effects of hydroxymethionine iron on iron absorption and metabolism in weaned piglets As shown in Table 7 below, compared with the control group, the serum iron content of the hydroxymethionine iron group was significantly increased ( P <0.01), and the levels of ferritin, hepcidin, and apotransferrin were significantly decreased ( P <0.05).

[0052] Table 7: Effects of hydroxymethionine iron on iron absorption and metabolism in weaned piglets

[0053] Serum iron primarily consists of iron bound to transferrin in serum. Its concentration is an important indicator of the body's iron status and can be used clinically to diagnose iron deficiency anemia. Hepcidin is a key hormone in iron metabolism, maintaining iron homeostasis by inhibiting intestinal iron absorption and cellular iron release. Serum ferritin is the body's primary iron storage compound, while apotransferrin refers to transferrin that is unbound to iron. When iron deficiency anemia develops, iron requirements increase, serum iron levels decrease, and apotransferrin levels increase. In this study, supplementation with hydroxymethionine iron increased serum iron levels and decreased ferritin, hepcidin, and apotransferrin levels. This suggests that hydroxymethionine iron has higher bioavailability than ferrous sulfate and can effectively improve iron status. This may be related to the fact that hydroxymethionine iron protects iron ions through chelation, preventing the formation of insoluble compounds in the intestine, thereby enhancing intestinal absorption.

[0054] 2.4 Effects of hydroxymethionine iron on antioxidant indices in weaned piglets As shown in Table 8 below, serum CAT, GSH-PX and GSH-PX in the hydroxymethionine iron group were significantly increased compared with the control group on the 7th and 21st days of the experiment ( P <0.05), serum MDA content was significantly decreased ( P <0.01, but the difference in SOD content was not significant ( P >0.05).

[0055] Table 8: Effects of hydroxymethionine iron on antioxidant indices in weaned piglets

[0056] Free radicals in the animal body are in a state of dynamic equilibrium, and free radicals are constantly produced and eliminated by the antioxidant system. On the one hand, iron participates in the body's free radical scavenging reaction as a coenzyme of oxidoreductase. On the other hand, excess iron produces reactive oxygen species through the Fenton reaction. CAT is an iron-containing enzyme, and its main function is to participate in the process of reactive oxygen metabolism. The reactive oxygen species after SOD dismutation degradation can be degraded by catalase into non-toxic and harmless substances such as water and oxygen. MDA is the end product of lipid peroxidation, and its content can reflect the degree of oxidative damage to the body. GSH-Px can directly scavenge oxygen free radicals and protect the body from oxidative damage. In the present invention, compared with the control group, the antioxidant enzymes GSH-Px and CAT in the weaned piglets in the hydroxymethionine iron group were significantly increased, while MDA was significantly decreased, indicating that hydroxymethionine chelated iron can enhance the activity of the antioxidant enzyme system in the body and reduce the production of lipid peroxides.

[0057] Effects of 2.5-hydroxymethionine iron on inflammatory cytokine levels in weaned piglets As shown in Table 9 below, on the 7th and 21st days of the experiment, the serum IL-6, IL-1β and TNF-α levels in the hydroxymethionine iron group were significantly reduced compared with those in the control group ( P <0.01).

[0058] Table 9: Effects of hydroxymethionine iron on immune parameters of weaned piglets

[0059] IL-1β, IL-6, and TNF-α are the main pro-inflammatory factors in animal bodies. TNF-α is mainly secreted by Th1 cells and plays an important role in cellular immune responses. IL-6 is produced by Th2 cells and plays an important role in regulating humoral immune responses, while IL-1β participates in the regulation of the body's adaptive immune response. In the present invention, compared with the control group, the serum IL-6, IL-1β, and TNF-α levels in the hydroxymethionine iron group were significantly reduced, which is related to the stable structure of hydroxymethionine chelated iron, which can reduce the release of free iron and thus reduce the inflammatory response.

[0060] The experimental results show that feeding weaned piglets with hydroxymethionine iron instead of ferrous sulfate can improve the piglets' iron absorption and metabolism, enhance antioxidant function and reduce the expression of inflammatory factors.

[0061] Comparative Example 1: The preparation method of the hydroxymethionine iron chelate of this comparative example comprises the following steps: S1. Dissolve 88 wt% hydroxymethionine in an appropriate amount of water and adjust the pH thereof to about 7 with a 2 mol / L sodium hydroxide solution to prepare a ligand neutralization solution with a concentration of 1 mol / L.

[0062] S2. Take 10 mL of the neutralized solution (10 mmol) and mix it evenly with 10 mL of ferrous chloride tetrahydrate aqueous solution (6 mmol) to obtain a yellow-green turbid solution. Filter through a 10 mm filter to obtain a yellow-green filtrate.

[0063] S3. Place the filtrate in a test tube and slowly add an equal volume of anhydrous ethanol. Allow to stand for several days to diffuse. A red precipitate will form.

[0064] Comparative Example 2: The preparation method of the hydroxymethionine iron chelate of this comparative example comprises the following steps: S1. Dissolve 88 wt% hydroxymethionine in an appropriate amount of water and adjust the pH thereof to about 7 with a 2 mol / L sodium hydroxide solution to prepare a ligand neutralization solution with a concentration of 1 mol / L.

[0065] S2. Take 10 mL of the neutralized solution (10 mmol) and mix it evenly with 10 mL of ferrous chloride tetrahydrate aqueous solution (4 mmol) to obtain a yellow-green turbid solution. Filter through a 10 mm filter to obtain a green clear solution.

[0066] S3. Place the solution in a test tube and slowly add an equal volume of anhydrous ethanol. Allow to stand for diffusion. After three to four days, thin flakes of solid material will grow on the walls of the test tube. This solid material will oxidize rapidly in air.

[0067] Comparative Example 3: The preparation method of the hydroxymethionine iron chelate of this comparative example comprises the following steps: S1. Dissolve 88 wt% hydroxymethionine in an appropriate amount of water and adjust the pH thereof to about 7 with a 2 mol / L sodium hydroxide solution to prepare a ligand neutralization solution with a concentration of 1 mol / L.

[0068] S2. Take 10 mL of the neutralized solution (10 mmol) and mix it evenly with 10 mL of ferrous chloride tetrahydrate aqueous solution (6 mmol) to obtain a yellow-green turbid solution. Filter through a 10 mm filter to obtain a green clear solution.

[0069] S3. Place the solution in a test tube and slowly add an equal volume of methanol dropwise. Allow to stand for diffusion. No product is obtained after several days of standing.

[0070] The above are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered as the scope of protection of the present invention.

[0071] Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A hydroxymethionine iron chelate, characterized in that The invention relates to a binuclear chelate system composed of a chelate structure A and a chelate structure B, wherein both the chelate structure A and the chelate structure B include a central iron ion and a hydroxymethionine ligand. One central iron ion is simultaneously coordinated with the hydroxyl oxygen and carboxyl oxygen of two hydroxymethionine ligands to form a chelate structure having a double five-membered heterocyclic ring; the central iron ion of the chelate structure A is coordinated with the carbonyl cation of the hydroxymethionine ligand of the chelate structure B.

2. The hydroxymethionine iron chelate according to claim 1, characterized in that The coordination numbers of the central iron ion in the chelate structure A and the chelate structure B are both 6. The central iron ion in the chelate structure A is coordinated and connected with one water molecule, and the central iron ion in the chelate structure B is coordinated and connected with two water molecules.

3. The hydroxymethionine iron chelate according to claim 1, characterized in that The central iron ion is a divalent iron ion.

4. The hydroxymethionine iron chelate according to claim 1, characterized in that The crystal space group of the hydroxymethionine chelate is P .

5. A method for preparing the hydroxymethionine iron chelate according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. dissolving hydroxymethionine to prepare a ligand neutralization solution; S2. Evenly mix the ligand neutralization solution and the ferrous chloride tetrahydrate solution. After the reaction is complete, filter and obtain the hydroxymethionine iron chelate solution.

6. The method for preparing the hydroxymethionine iron chelate according to claim 5, characterized in that: The pH of the ligand neutralization solution described in S1 is 8-9.5, and the concentration is 1 mol / L.

7. The method for preparing the hydroxymethionine iron chelate according to claim 5, characterized in that: The molar ratio of hydroxymethionine in the ligand neutralization solution to ferrous chloride tetrahydrate in the ferrous chloride tetrahydrate solution in S2 is 10:(5~7).

8. The method for preparing the hydroxymethionine iron chelate according to any one of claims 5 to 7, characterized in that: S2: After obtaining the solution of the hydroxymethionine iron chelate, an equal volume of anhydrous ethanol is slowly added dropwise to the solution of the hydroxymethionine iron chelate, and the solution is allowed to stand and diffuse to obtain needle-shaped transparent crystals.

9. Use of the hydroxymethionine iron chelate according to any one of claims 1 to 4 or the hydroxymethionine iron chelate prepared by the preparation method according to any one of claims 5 to 8, characterized in that: The hydroxymethionine iron chelate is used for preparing animal feed additives or animal nutrients.

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