A method for refining high-purity vitamin A palmitate

Abstract

The present invention discloses for the first time a method for refining high-purity vitamin A palmitate, which can effectively control the levels of oxidative impurities, isomers and polymers in the product, and the obtained product remains stable under conventional storage conditions. The refining method comprises: dissolving crude vitamin A palmitate in a solvent, adding acetonitrile and an antioxidant, heating to dissolve, cooling to crystallize, and filtering; transferring the filter cake to a reactor, adding a solvent, supplementing an antioxidant, and concentrating to obtain a high-purity vitamin A palmitate finished product. The present invention provides a method for refining high-purity vitamin A palmitate, which is suitable for scale-up production and has good product stability.

Description

Technical Field

[0001] The present invention belongs to the field of pharmaceutical chemical synthesis technology, and specifically relates to a method for refining high-purity vitamin A palmitate. Background Art

[0002] The structural formula of vitamin A palmitate is as follows:

[0003]

[0004] In the pharmacopoeia, retinol, vitamin A acetate, and vitamin A palmitate are collectively referred to as vitamin A. Vitamin A is a fat-soluble vitamin and an essential nutrient for the human body. Retinol is chemically reactive and easily destroyed by acids, air, oxidants, high temperatures, or ultraviolet light. Vitamin A palmitate, on the other hand, is relatively stable and is widely used in food and pharmaceuticals.

[0005] Vitamin A palmitate is the raw material for preparations such as Multivitamin (12) for injection, 12-complex vitamins for injection, Multivitamin injection (13) (10 / 3), Multivitamin (13) for injection, Multivitamin injection for children (13), Multivitamin (13) for injection for children, Fat-soluble vitamin (I) for injection, and Fat-soluble vitamin (II) for injection.

[0006] The synthesis process of vitamin A palmitate mainly uses vitamin A acetate as the starting material, which is hydrolyzed to produce retinol, which is then condensed with palmitic acid to produce vitamin A palmitate. The starting material, vitamin A acetate, will produce degradation impurities such as oxidative impurities, isomers, and polymers during long-term storage. During the production of retinol, due to its poor stability and easy degradation, degradation impurities from the starting material and intermediates will be introduced into vitamin A palmitate. In addition, vitamin A palmitate is oily, making it difficult to develop a purification process. In particular, the oxidative impurities of vitamin A are reported in references (Chem. Res. Toxicol. 2005, 18, 129-138. and Int J Vitam Nutr Res. 1992, 62(3), 201-208.), and most of the oxidative impurities are epoxy structures. Epoxy structures are warning structures of genotoxic impurities, which pose potential safety risks.

[0007] All-trans vitamin A palmitate is the most stable and effective active ingredient in vitamin A palmitate. During production, storage, and transportation, many factors can cause vitamin A palmitate to isomerize, thereby affecting its activity and effectiveness. Cis and trans isomers vary significantly in their bioavailability, with the cis isomer of vitamin A palmitate exhibiting lower bioactivity than the all-trans isomer. The 13-cis isomer has a relative activity of 76%, the 11-cis isomer has a relative activity of 31%, the 9-cis isomer has a relative activity of 19%, and the 9,13-bis-cis isomer has a relative activity of only 16% (Yu An. Study on the Stability of Vitamin A [D]. Hangzhou: Zhejiang University, 2012). The content of each cis-isomer impurity affects the efficacy and safety of vitamin A palmitate API and its related preparations. Therefore, strict control of the limits of each impurity isomer can ensure the efficacy and safety of vitamin A palmitate API and its related preparations.

[0008] In existing literature, Wanhua Chemical patents CN 112724059 and CN 113122870 report on the purification of vitamin A palmitate. The product was crystallized using alcoholic solvents at -2 to 20°C, primarily methanol and ethanol. Due to the significant differences in polarity between the substances, methanol and ethanol have been shown to separate from vitamin A palmitate at low temperatures, preventing effective purification. Isopropyl alcohol and other solvents have a certain solubility for the product. When using isopropyl alcohol as a solvent for crystallization below 0°C, isopropyl alcohol readily forms solvates with the product, making filtration difficult. Furthermore, alcoholic solvents have limited effectiveness in removing degradation impurities, such as oxidative impurities. It has also been found that solvated vitamin A palmitate is more susceptible to the formation of oxidative impurities.

[0009] CN 118812405 reports a purification method for increasing the purity and content of vitamin A palmitate and reducing residual organic solvents. The method involves adding crude vitamin A palmitate to a ketone solvent, heating and stirring to dissolve the product, and then cooling the product to an alcohol solvent for crystallization. This product contains very low residual organic solvents (less than 0.1%). This purification method is primarily intended to reduce the residual organic solvent content of vitamin A palmitate, but does not specify the content of impurities, particularly the cis-isomer, in the finished vitamin A palmitate.

[0010] CN 102424662 reports a method for separating and purifying vitamin A palmitate. This method removes palmitic acid through low-temperature crystallization and separates vitamin A palmitate and vitamin A acetate using liquid-liquid extraction or silica gel column chromatography. This method involves column chromatography and is not suitable for scale-up production. Furthermore, this method is only applicable to palmitic acid and vitamin A acetate, not to the removal of the cis-isomer of vitamin A palmitate.

[0011] CN1072646C reports a method for purifying stabilized vitamin A, limiting the concentration of vitamin A cis-isomer impurities to less than 2%, ensuring the effectiveness and safety of vitamin A palmitate-related preparations. However, this process is only applicable to the preparation of stabilized vitamin A, resulting in low purity. Furthermore, the purification process requires heating and pressure control, making it complex.

[0012] Vitamin A palmitate is an oily substance that solidifies into a paste, making it difficult to purify. Process impurities and degradation impurities within it can affect product quality and safety. With the increasing emphasis on pharmaceutical consistency evaluation, quality control of vitamin A palmitate is becoming increasingly critical. However, existing technologies lack clear limits for the content of impurities such as isomers in vitamin A palmitate, and there is also a lack of technologies for producing high-quality, high-purity vitamin A palmitate. Therefore, developing a purification method for vitamin A palmitate to obtain high-purity, stable-quality vitamin A palmitate is of great significance. Summary of the Invention

[0013] In order to overcome the shortcomings of the above-mentioned technologies, the present invention provides a method for refining high-purity vitamin A palmitate, which can effectively control the levels of isomers, oxidative impurities and polymers in the product, and the obtained product remains stable under conventional storage conditions.

[0014] The purification method of vitamin A palmitate is as follows:

[0015] Step (1) dissolving crude vitamin A palmitate in a solvent, adding acetonitrile and an antioxidant, heating to dissolve, cooling to crystallize, and filtering.

[0016] Step (2) The filter cake is transferred to a reactor, a solvent is added, an antioxidant is added, and the product of vitamin A palmitate is obtained by concentration.

[0017] The above-mentioned purification method is characterized in that the dissolving solvent for vitamin A palmitate described in step (1) is one of acetone, ethyl acetate, and isopropyl alcohol; the dissolving solvent is 1 to 4 times the mass of vitamin A palmitate; the acetonitrile is 1 to 4 times the mass of vitamin A palmitate; and the ratio of solvent to acetonitrile is 1:0.5 to 3.

[0018] The above-mentioned purification method is characterized in that the antioxidant described in step (1) is one of racemic α-tocopherol, 2,6-di-tert-butyl-4-methylphenol, and vitamin E; and the amount of the antioxidant is 0.1% to 2% of the mass of vitamin A palmitate.

[0019] The above purification method is characterized in that the dissolution temperature in step (1) is 15~40°C, preferably 20-35°C; and the crystallization temperature is -15~10°C, preferably -15~0°C.

[0020] The above refining method is characterized in that the dissolving solvent described in step (2) is one of n-heptane, n-hexane, and petroleum ether, or a combination in any proportion, and the amount used is 2 to 5 times the amount of vitamin A palmitate fed.

[0021] The above-mentioned purification method is characterized in that the antioxidant described in step (2) is one of racemic α-tocopherol, 2,6-di-tert-butyl-4-methylphenol, and vitamin E; and the amount of the antioxidant used is 0.9% to 2% of the mass of vitamin A palmitate.

[0022] The beneficial effects produced by the present invention are:

[0023] 1) The yield of vitamin A palmitate obtained by the refining process of the present invention is as high as 93%, the purity is as high as 99.38%, the cis-isomer impurity content limit is no more than 1wt%, the maximum single impurity content is no more than 0.10wt%, the total impurity limit is no more than 2.0wt%, the polymer limit is no more than 0.5wt%, and the palmitic acid limit is no more than 0.5wt%, ensuring the effectiveness and safety of vitamin A palmitate-related preparations.

[0024] 2) The refining process of this invention involves adding an antioxidant twice, further ensuring the stability of the finished vitamin A palmitate under standard storage conditions. Accelerated stability data from 0 days, 1 month, 2 months, 3 months, and 6 months demonstrates the excellent stability of the product produced using this process, with isomeric impurity content limited to no more than 1wt%, and a maximum of no more than 0.10wt% for any single impurity. Furthermore, the growth of polymer, isomer, and oxidized impurities is slow.

[0025] 3) The refining process of the present invention avoids the solvation phenomenon produced in the refining process using alcohol solvents. The product is uniformly precipitated in the crystallization system, has strong impurity removal ability, is simple to operate, has a high yield, and is suitable for scale-up production.

[0026] 4) The refining method is simple to operate, has no special requirements for equipment, and does not involve special raw materials. It is suitable for large-scale production. The refined vitamin A palmitate meets the requirements of vitamin A palmitate raw materials for preparations such as multivitamins for injection (12), 12 complex vitamins for injection, multivitamin injection (13) (10 / 3), multivitamins for injection (13), pediatric multivitamin injection (13), pediatric multivitamin injection (13), fat-soluble vitamins for injection (I), and fat-soluble vitamins for injection (II). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the HPLC spectrum of high-purity vitamin A palmitate prepared in Example 8;

[0028] Figure 2This is the peak result of the HPLC spectrum of the high-purity vitamin A palmitate prepared in Example 8. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific implementation methods. The following description is only for the purpose of explaining the present invention. The scope of protection of the present invention is not limited to these embodiments. Those skilled in the art should understand that equivalent replacements or corresponding improvements made to the contents of the present invention are still within the scope of protection of the present invention.

[0030] The present invention is described in detail with specific examples below, but is not limited to this patent.

[0031] The detection method of vitamin A palmitate in this technology is as follows:

[0032] The method for detecting related substances and contents of vitamin A palmitate refers to the method disclosed in patent document CN 108445098 "An analytical method for detecting impurities in vitamin A palmitate": high performance liquid chromatography, the chromatographic column is an octadecylsilane bonded silica gel chromatographic column, the mobile phase A is 5 mmol / L ammonium acetate solution (the pH value is adjusted to 4.5 with glacial acetic acid)-methanol, the volume ratio is 30:70, the mobile phase B is methanol-isopropanol, the volume ratio is 55:45, the detection wavelength is 325 nm, the column temperature is 30 ° C, the flow rate is 1.0 mL / min, and the mobile phases A and B are carried out according to the gradient elution program:

[0033]

[0034] The HPLC detection method for 13-cis isomer, 9,13-bis-cis isomer, and 9-cis isomer in vitamin A palmitate is high performance liquid chromatography, and the chromatographic conditions are as follows: chromatographic column: octadecylsilane bonded silica gel chromatographic column; flow rate: 1.0 mL / min; detection wavelength: 325 nm; column temperature: 30°C; isocratic elution; mobile phase: n-hexane-isopropanol (999.5:0.5).

[0035] Example 1

[0036] Add 30 g crude vitamin A palmitate into dissolving solvent and acetonitrile, and 0.08 g racemic α-tocopherol. Heat to 20-35°C under nitrogen protection, stir and dissolve until clear. After dissolving, cool to -10-5°C, stir and crystallize for 1 hour, and filter.

[0037] The filter cake was dissolved in 80 mL of n-hexane. After the solution was clear, 0.36 g of racemic α-tocopherol was added. The mixture was stirred for 5 to 10 minutes and concentrated under reduced pressure until the n-hexane concentration was ≤ 0.5%. This gave the finished product of vitamin A palmitate. The following table shows the test monitoring data of vitamin A palmitate prepared by each process:

[0038]

[0039] Note: The volume ratio of the dissolving solvent and acetonitrile to the mass ratio of crude vitamin A palmitate is 1~4ml:1g, expressed as 1~4V.

[0040] Example 2

[0041] Add 30 g crude vitamin A palmitate to 90 mL of isopropanol and 90 mL of acetonitrile, and 0.06 g of 2,6-di-tert-butyl-4-methylphenol. Heat to 20°C to 35°C under nitrogen protection, stir to dissolve clearly, then cool to -15°C to -10°C, stir to crystallize for 1 hour, and filter.

[0042] The filter cake was dissolved in 80 mL of n-heptane. After the solution was clear, 0.4 g of 2,6-di-tert-butyl-4-methylphenol was added. The mixture was stirred for 5 to 10 minutes and concentrated under reduced pressure until the n-heptane concentration was ≤ 0.5%. Vitamin A palmitate was obtained with a yield of 92%.

[0043] Example 3

[0044] Add 30 g crude vitamin A palmitate to 90 mL of acetone and 60 mL of acetonitrile, and 0.6 g of vitamin E. Heat to 20°C to 35°C under nitrogen protection, stir and dissolve until clear. After dissolving, cool to -5°C to 0°C, stir and crystallize for 1 hour, and filter.

[0045] The filter cake was dissolved in 80 mL of n-heptane, and after the solution was clear, 0.4 g of vitamin E was added, stirred for 5 to 10 minutes, and concentrated under reduced pressure until the n-heptane concentration was ≤ 0.5%, to obtain the finished product of vitamin A palmitate with a yield of 78%.

[0046] Example 4

[0047] Add 30 g crude vitamin A palmitate to 90 mL of isopropanol and 90 mL of acetonitrile, and 0.04 g of racemic α-tocopherol. Heat to 20°C to 35°C under nitrogen protection, stir and dissolve until clear. After dissolving, cool to -5°C to 0°C, stir and crystallize for 2 hours, and filter.

[0048] The filter cake was dissolved in 80 mL of n-heptane, and after the solution was clear, 0.5 g of racemic α-tocopherol was added, stirred for 5 to 10 minutes, and concentrated under reduced pressure until the n-heptane concentration was ≤ 0.5%, thereby obtaining the finished product of vitamin A palmitate with a yield of 85%.

[0049] Example 5 Accelerated stability study of the product of Example 4

[0050] Vitamin A palmitate is stored at a temperature below 15°C. 20g of the product from Example 4 was placed in a soda-lime glass molded pharmaceutical bottle and subjected to accelerated stability tests at a temperature of 25°C ± 2°C and a relative humidity of 60% ± 5% for 0 days, 1 month, 3 months, and 6 months. The accelerated tests demonstrated that the product produced using this process exhibited excellent stability, with a maximum single impurity content of no more than 0.10wt%, and slow growth of polymers and isomers.

[0051]

[0052] Example 6

[0053] Add 30 g crude vitamin A palmitate to 90 mL of isopropanol and 90 mL of acetonitrile, and 0.04 g of racemic α-tocopherol. Heat to 20°C to 35°C under nitrogen protection, stir and dissolve until clear. After dissolving, cool to -5°C to 0°C, stir and crystallize for 2 hours, and filter.

[0054] The filter cake was dissolved in 80 mL of n-heptane, and after the solution was clear, 0.27 g of racemic α-tocopherol was added, stirred for 5 to 10 minutes, and concentrated under reduced pressure until the n-heptane concentration was ≤ 0.5%, to obtain the finished product of vitamin A palmitate with a yield of 83%.

[0055] Example 7

[0056] Add 30 g crude vitamin A palmitate to 90 mL of isopropanol and 90 mL of acetonitrile, and 0.04 g of racemic α-tocopherol. Heat to 20°C to 35°C under nitrogen protection, stir and dissolve until clear. After dissolving, cool to -5°C to 0°C, stir and crystallize for 2 hours, and filter.

[0057] The filter cake was dissolved in 80 mL of n-heptane, and after the solution was clear, 0.6 g of racemic α-tocopherol was added, stirred for 5 to 10 minutes, and concentrated under reduced pressure until the n-heptane concentration was ≤ 0.5%, thereby obtaining the finished product of vitamin A palmitate with a yield of 85%.

[0058] Example 8

[0059] Add 30 g crude vitamin A palmitate into dissolving solvent and acetonitrile, and 0.08 g racemic α-tocopherol. Heat to 20-35°C under nitrogen protection, stir and dissolve until clear. After dissolving, cool to -10-5°C, stir and crystallize for 1 hour, and filter.

[0060] The filter cake was dissolved in 80 mL of n-hexane. After the solution became clear, 0.36 g of racemic α-tocopherol was added, and the mixture was stirred for 5-10 minutes. The mixture was concentrated under reduced pressure until the n-hexane concentration was ≤ 0.5%, thereby obtaining the finished product of vitamin A palmitate in a yield of 92%. The following table shows the content of vitamin A palmitate, 13-cis isomer, 9,13-bis-cis isomer, and 9-cis isomer in the high-purity vitamin A palmitate prepared in this example:

[0061] 。

Claims

1. A method for refining high-purity vitamin A palmitate, characterized in that: The preparation method comprises: Step 1, dissolving crude vitamin A palmitate in a first solvent, adding acetonitrile and antioxidant A, heating to dissolve, cooling to crystallize, and filtering; The first solvent is selected from one of acetone, ethyl acetate and isopropanol; The antioxidant A is selected from one of racemic α-tocopherol, 2,6-di-tert-butyl-4-methylphenol and vitamin E; The mass ratio of the first solvent volume to vitamin A palmitate is 1-4 mL: 1 g; The mass ratio of the acetonitrile volume to vitamin A palmitate is 1-4 mL: 1 g; The volume ratio of the first solvent to acetonitrile is 1:0.5-3; The amount of the antioxidant A is 0.1% to 2% of the mass of vitamin A palmitate; The temperature of the heating and dissolving is 20-35°C; The cooling crystallization temperature is -15~0°C; Step 2: transferring the filter cake to a reactor, adding a second solvent, adding antioxidant B, and concentrating to obtain a high-purity vitamin A palmitate finished product; The second solvent is selected from one of n-heptane, n-hexane and petroleum ether; The antioxidant B is selected from one of racemic α-tocopherol, 2,6-di-tert-butyl-4-methylphenol and vitamin E; The volume ratio of the second solvent to vitamin A palmitate is 2-5 mL: 1 g; The amount of the antioxidant B is 0.9% to 2% of the mass of vitamin A palmitate; The total HPLC content of cis-isomer impurities in the impurities of the high-purity vitamin A palmitate finished product is no more than 1.0 wt %.

2. The refining method according to claim 1, characterized in that Step 1, dissolving crude vitamin A palmitate in a first solvent, adding acetonitrile and antioxidant A, heating to dissolve, cooling to crystallize, and filtering; The first solvent is one of isopropanol, acetone, and ethyl acetate, and the mass ratio of the first solvent to vitamin A palmitate is 3 mL:1 g; The mass ratio of the acetonitrile to vitamin A palmitate feed is 3 mL:1 g; The dosage of the antioxidant A is 0.27% of the mass of vitamin A palmitate feed; Step 2: The filter cake is transferred to a reaction kettle, a second solvent is added, antioxidant B is added, and the mixture is concentrated to obtain a finished product of vitamin A palmitate; The second solvent is n-hexane, and the mass ratio of the second solvent to the vitamin A palmitate is 2.67 mL: 1 g; The amount of the antioxidant B used is 1.2% of the mass of vitamin A palmitate.

3. The purification method according to claim 1, characterized in that: Step 1, dissolving crude vitamin A palmitate in a first solvent, adding acetonitrile and antioxidant A, heating to dissolve, cooling to crystallize, and filtering; The first solvent is one of isopropanol, acetone, and ethyl acetate, and the mass ratio of the first solvent to vitamin A palmitate is 3 mL:1 g; The mass ratio of the acetonitrile to vitamin A palmitate feed is 3 mL:1 g; The dosage of the antioxidant A is 2% of the mass of vitamin A palmitate feed; Step 2: The filter cake is transferred to a reaction kettle, a second solvent is added, antioxidant B is added, and the mixture is concentrated to obtain a finished product of vitamin A palmitate; The second solvent is n-heptane, and the mass ratio of the second solvent to the vitamin A palmitate is 2.67 mL: 1 g; The amount of the antioxidant B is 1.3% of the mass of vitamin A palmitate.

4. The method according to claim 1, characterized in that: The cis isomer impurities in the high-purity vitamin A palmitate finished product impurities include one or more of 13-cis isomer, 9,13-di-cis isomer, and 9-cis isomer.

5. According to any one of the methods of claims 1-4, the content of 13-cis isomer in the cis isomer impurities in the finished vitamin A palmitate ester is not higher than 0.5wt%, the content of 9,13-bis-cis isomer is not higher than 0.5wt%, and the content of 9-cis isomer is not higher than 0.5wt%.

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