A method for preparing L-carnosine spherical crystals

Abstract

This invention discloses a method for preparing L-carnosine spherical crystals, comprising the following steps: dissolving L-carnosine in a good solvent, water, to obtain an aqueous solution containing L-carnosine; controlling the temperature of the aqueous solution and continuously stirring; adding a poor solvent to the L-carnosine-containing aqueous solution to precipitate L-carnosine spherical crystals; and separating and drying the spherical crystals to obtain the L-carnosine spherical crystals. The good solvent is water; the poor solvent is N,N-dimethylformamide and / or dimethyl sulfoxide. The preparation process of the L-carnosine crystals prepared by this invention is simple, involving only water and a poor solvent, and the process is straightforward. The particle size can be adjusted by the concentration of the aqueous solution and the stirring rate, resulting in an average particle size of 50–200 μm. The product particles are rounded, have high flowability, an angle of repose of 30°–37°, and a bulk density of 0.4–0.7 g / cm³. 3 This solved the problems of poor crystal morphology and poor particle flowability of L-carnosine.

Description

Technical Field

[0001] This invention belongs to the field of drug crystallization technology, specifically relating to a method for preparing L-carnosine spherical crystals. Background Technology

[0002] L-Carnosine (CAS No. 305-84-0), also known as β-alanyl-L-histidine, is a natural dipeptide formed by the condensation of β-alanine and L-histidine. Studies have shown that L-carnosine has important physiological and pharmacological functions such as anti-oxidation, anti-aging, scavenging of free radicals in the body, chelation of transition metals, and prevention of ulcers. It has certain biological activities for various diseases such as hypertension, heart disease, Alzheimer's disease, cataracts, and anti-tumor effects, and has a wide range of applications in the fields of medicine, health care, food, and cosmetics.

[0003] In industrial production, L-carnosine crystals are mostly flaky or needle-like, causing numerous downstream processing problems, such as poor powder properties and easy agglomeration. Current research and patents mainly focus on the production and synthesis methods of L-carnosine and its bioactivity, with less research on its crystallization and refining processes. A suitable recrystallization refining process can significantly improve the crystal morphology of the product, thereby enhancing its powder properties and ultimately affecting the subsequent processing and use of L-carnosine crystals. To save on the granulation process, directly preparing spherical crystals through controlled crystallization has the effect of simplifying the process and improving product quality. Spherical crystals have higher flowability, bulk density, stability, particle uniformity, and lower filtration pressure. To solve the problems of low bulk density and undesirable crystal habit during L-carnosine crystallization, the preparation of L-carnosine spherical particles has become a research hotspot. Currently, spherical aggregates can be obtained by adding L-carnosine aqueous solution to anhydrous ethanol (Yanan Zhou, et al. Self-assembly of Monodispersed Carnosine Spherical Crystals in Reverse Antisolvent Crystallization Process, Crystal Growth & Design, 2019). Monodisperse L-carnosine spherical crystals with an average particle size of 211 μm were prepared in the literature, but the sphericity and bulk density of the product need further improvement.

[0004] This invention provides an efficient and green L-carnosine spherical crystallization process to prepare L-carnosine spherical crystals with uniform particles, good flowability, high bulk density, and industrial-scale production capability. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for improving the flowability of L-carnosine in order to prepare L-carnosine spherical particles with regular shape, dense particles, good flowability, and strong industrial operability, which are not prone to aggregation.

[0006] To solve the above-mentioned technical problems, the present invention discloses the following technical solution:

[0007] A method for preparing L-carnosine spherical crystals includes the following steps: dissolving L-carnosine in a good solvent to obtain a solution containing L-carnosine; controlling the temperature of the solution and continuously stirring; adding a poor solvent to the solution containing L-carnosine; precipitating L-carnosine spherical crystals; and obtaining the L-carnosine spherical crystals by separation and drying.

[0008] Wherein, the good solvent is water; the poor solvent is N,N-dimethylformamide and / or dimethyl sulfoxide.

[0009] The concentration of L-carnosine in the L-carnosine-containing solution is 0.05–0.3 g / g, preferably 0.1–0.2 g / g, such as 0.1 g / g, 0.15 g / g, 0.2 g / g, 0.25 g / g, etc.

[0010] The stirring temperature is 20-35℃, preferably 25-30℃, such as 20℃, 25℃, 30℃, 35℃, etc.

[0011] The stirring speed is 100-700 rpm, preferably 200-400 rpm, such as 100 r / min, 300 r / min, 500 r / min, 700 r / min, etc.; preferably, the stirring method is mechanical stirring.

[0012] The volume ratio of the poor solvent to the good solvent is 2 to 8:1, preferably 3 to 5:1, such as 2:1, 4:1, 6:1, 8:1, etc.

[0013] The addition rate of the undesirable solvent is 0.1 to 1 mL / min, preferably 0.2 to 0.7 mL / min, such as 0.1 mL / min, 0.3 mL / min, 0.5 mL / min, 0.7 mL / min, 0.9 mL / min, etc.

[0014] In this process, stirring continues after the addition of the undesirable solvent, followed by aging. Preferably, the stirring time is 0–4 hours, more preferably 1–2 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, etc. The stirring temperature and rate are the same as before, such as the stirring temperature being 20–35°C, more preferably 25–30°C, such as 20°C, 25°C, 30°C, 35°C, etc. The stirring speed is 100–700 rpm, more preferably 200–400 rpm, such as 100 rpm, 300 rpm, 500 rpm, 700 rpm, etc. Preferably, mechanical stirring is used. Preferably, the aging time is 1–2 hours.

[0015] The separated parts are then washed and dried.

[0016] The washing method involves washing with ethanol or an aqueous ethanol solution 3 to 5 times.

[0017] The separation is a solid-liquid separation, preferably filtration.

[0018] The drying conditions are under reduced pressure; preferably, the drying temperature is 25-50°C and the drying time is 12-48 hours.

[0019] In some embodiments, the technical solution of the present invention is as follows:

[0020] (1) Dissolve L-carnosine in a good solvent, water, and prepare an aqueous solution with an L-carnosine concentration of 0.05 to 0.3 g / g at room temperature;

[0021] (2) The temperature of the L-carnosine aqueous solution is controlled at 20-35℃ and stirred continuously at a stirring rate of 100-700 r / min.

[0022] (3) Add the undesirable solvent N,N-dimethylformamide and / or dimethyl sulfoxide to the L-carnosine aqueous solution in step (2) above, with a dropping rate of 0.1 to 1 mL / min, and the volume ratio of the undesirable solvent to the good solvent in the L-carnosine solution is 2 to 8.

[0023] (4) After the undesirable solvent is added, continue stirring for 0 to 4 hours under the temperature and stirring rate conditions of step (2) above to grow crystals; after crystallization, the precipitated L-carnosine spherical crystals are subjected to solid-liquid separation, washing and drying in sequence.

[0024] In step (4), the crystal growth time is preferably 1 to 2 hours.

[0025] The L-carnosine spherical crystals prepared by the method of this invention are spherical particles with an average particle size of 50–200 μm, preferably 50–130 μm, such as 70, 90, 110, 130, 150, 170, and 190 μm; an angle of repose of 30–37°, such as 31, 32, 33, 34, and 35°; and a bulk density of 0.4–0.7 g / cm³. 3 For example, 0.5, 0.6 g / cm³ 3 Compared to the spherical crystals with an average particle size of 211 μm, a bulk density of 0.224 g / mL, and an angle of repose of 39° obtained in the article published by Yanan Zhou et al., the spherical crystals prepared by the method of this invention have a smaller average particle size, a higher bulk density, and a smaller angle of repose. Therefore, the spherical crystals obtained by this invention have better flowability than those in the prior art.

[0026] The present invention can control the size of spherical products by adjusting the concentration of L-carnosine aqueous solution in step (1) and the stirring rate in step (2). The smaller the concentration of L-carnosine aqueous solution and the larger the stirring rate, the smaller the particle size of the L-carnosine spherical products obtained.

[0027] Beneficial effects:

[0028] (1) The preparation process of the spherical crystal product of the present invention is simple, and the spherical crystal particles obtained are compact and round, with high sphericity.

[0029] (2) The L-carnosine spherical particles obtained by this invention have a higher bulk density, which is 0.4–0.7 g / cm³. 3 The spherical product has a smaller angle of repose, ranging from 30 to 37°, resulting in better flowability. Furthermore, the L-carnosine spherical particles obtained by this invention have smaller crystal diameters and larger specific surface areas, which helps improve the bioavailability of the drug and has good application and development prospects. Attached Figure Description

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0031] Figure 1 The image shows a scanning electron microscope (SEM) image of the L-carnosine spherical crystals prepared according to the present invention (Example 3).

[0032] Figure 2 This is a scanning electron microscope image of L-carnosine spherical crystals in the prior art (Comparative Example 1).

[0033] Figure 3 The images show the XRD patterns of L-carnosine raw material and L-carnosine spherical crystals from Example 3 of this invention. Detailed Implementation

[0034] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0035] Unless otherwise specified, the solid-liquid separation described in the following examples is performed using isothermal filtration. The temperature and stirring rate of the crystallization operation are maintained during the aging process.

[0036] Example 1: A method for preparing L-carnosine spherical crystals, comprising the following steps:

[0037] (1) At room temperature, dissolve 2g of L-carnosine raw material in 10mL of water to prepare an L-carnosine aqueous solution of 0.2g / g, and put the prepared solution into a jacketed crystallizer;

[0038] (2) Under the conditions of controlling the aqueous solution temperature at 30℃ and the stirring rate at 300r / min, 30mL of N,N-dimethylformamide was added to the above L-carnosine solution at a rate of 0.2mL / min using a peristaltic pump.

[0039] (3) After the solution is mixed, L-carnosine spherical crystals precipitate. After the unsuitable solvent is completely added, continue stirring to grow crystals for another 2 hours. The product obtained by stirring is separated into solid and liquid by filtration, washed three times with 95% ethanol aqueous solution, and dried in a vacuum chamber under reduced pressure at a temperature of 40°C for 24 hours.

[0040] The obtained product has a purity of 98.9%, an average particle size of 102 μm, and a bulk density of 0.57 g / cm³. 3 The angle of repose is 36°.

[0041] Example 2: A method for preparing L-carnosine spherical crystals, comprising the following steps:

[0042] (1) At room temperature, dissolve 2g of L-carnosine raw material in 10mL of water to prepare an L-carnosine aqueous solution of 0.2g / g, and put the prepared solution into a jacketed crystallizer;

[0043] (2) Under the conditions of controlling the aqueous solution temperature at 30℃ and the stirring rate at 200r / min, 30mL of dimethyl sulfoxide was added to the above L-carnosine solution at a rate of 0.3mL / min using a peristaltic pump.

[0044] (3) After the solution is mixed, L-carnosine spherical crystals precipitate. After the unsuitable solvent is completely added, continue stirring to grow crystals for another 2 hours. The product obtained by stirring is separated into solid and liquid by filtration, washed three times with anhydrous ethanol, and dried under reduced pressure at a temperature of 40°C for 24 hours.

[0045] The obtained product has a purity of 98.8%, an average particle size of 126 μm, and a bulk density of 0.45 g / cm³. 3 The angle of repose is 37°.

[0046] Example 3: A method for preparing L-carnosine spherical crystals, comprising the following steps:

[0047] (1) At room temperature, dissolve 1g of L-carnosine raw material in 10mL of water to prepare an L-carnosine aqueous solution of 0.1g / g, and put the prepared solution into a jacketed crystallizer;

[0048] (2) Under the conditions of controlling the aqueous solution temperature at 25℃ and the stirring rate at 200r / min, 50mL of dimethyl sulfoxide was added to the above L-carnosine solution at a rate of 0.3mL / min using a peristaltic pump.

[0049] (3) After the solution is mixed, L-carnosine spherical crystals precipitate. After the unsuitable solvent is completely added, continue stirring to grow crystals for another 1 hour. The product obtained by stirring is filtered for solid-liquid separation, washed three times with 85% ethanol aqueous solution, dried under reduced pressure at 30°C for 48 hours.

[0050] The obtained product has a purity of 98.9%, an average particle size of 98 μm, and a bulk density of 0.50 g / cm³. 3 The angle of repose is 35°.

[0051] Example 4: A method for preparing L-carnosine spherical crystals, comprising the following steps:

[0052] (1) At room temperature, dissolve 1.5g of L-carnosine raw material in 10mL of water to prepare an L-carnosine aqueous solution of 0.15g / g. Place the prepared solution into a jacketed crystallizer.

[0053] (2) Under the conditions of controlling the aqueous solution temperature at 25℃ and the stirring rate at 400r / min, 50mL of dimethyl sulfoxide was added to the above L-carnosine solution at a rate of 0.5mL / min using a peristaltic pump.

[0054] (3) After the solution is mixed, L-carnosine spherical crystals precipitate. After the unsuitable solvent is completely added, continue stirring to grow crystals for another 1 hour. The product obtained by stirring is separated into solid and liquid by filtration, washed three times with 95% ethanol aqueous solution, dried under reduced pressure at 30°C for 24 hours.

[0055] The obtained product has a purity of 98.7%, an average particle size of 107 μm, and a bulk density of 0.62 g / cm³. 3 The angle of repose is 34°.

[0056] Example 5: A method for preparing L-carnosine spherical crystals, comprising the following steps:

[0057] (1) At room temperature, dissolve 1g of L-carnosine raw material in 10mL of water to prepare an L-carnosine aqueous solution of 0.1g / g, and put the prepared solution into a jacketed crystallizer;

[0058] (2) Under the conditions of controlling the aqueous solution temperature at 25℃ and the stirring rate at 400r / min, 45mL of dimethyl sulfoxide was added to the above L-carnosine solution at a rate of 0.2mL / min using a peristaltic pump.

[0059] (3) After the solution was mixed, L-carnosine spherical crystals precipitated. After the unsuitable solvent was completely added, the mixture was stirred for another 1.5 hours to allow the crystals to grow. The mixture was then subjected to solid-liquid separation, washed three times with 90% ethanol aqueous solution, and dried under reduced pressure at 40°C for 18 hours.

[0060] The obtained product has a purity of 98.6%, an average particle size of 83 μm, and a bulk density of 0.54 g / cm³. 3 The angle of repose is 34°.

[0061] Example 6: A method for preparing L-carnosine spherical crystals, comprising the following steps:

[0062] (1) At room temperature, dissolve 1.5g of L-carnosine raw material in 10mL of water to prepare an L-carnosine aqueous solution of 0.15g / g. Place the prepared solution into a jacketed crystallizer.

[0063] (2) Under the conditions of controlling the aqueous solution temperature at 25℃ and the stirring rate at 200r / min, 30mL of a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide with a volume ratio of 1:1 was added to the above L-carnosine solution at a rate of 0.7mL / min using a peristaltic pump.

[0064] (3) After the solution is mixed, L-carnosine spherical crystals precipitate. After the unsuitable solvent is completely added, continue stirring to grow crystals for another 2 hours. The product obtained by stirring is filtered for solid-liquid separation, washed with water 3 times, dried under reduced pressure at a temperature of 35°C for 48 hours.

[0065] The obtained product has a purity of 98.5%, an average particle size of 117 μm, and a bulk density of 0.47 g / cm³. 3 The angle of repose is 36°.

[0066] Comparative Example 1: Method for preparing spherical crystals of L-carnosine spherical aggregates in the literature (Yanan Zhou, et al. Self-assembly of Monodispersed Carnosine Spherical Crystals in Reverse Antisolvent Crystallization Process, Crystal Growth & Design, 2019).

[0067] (1) Add 36 mL of ethanol solution to the jacketed crystallizer, control the temperature at 30 °C, and continuously stir with mechanical stirring at a speed of 300 r / min;

[0068] (2) Add 12 mL of L-carnosine aqueous solution with a concentration of 0.175 g / mL to the crystallization vessel dropwise at a rate of 0.1 mL / min;

[0069] (3) After the L-carnosine aqueous solution was added dropwise, it was filtered directly without aging, washed three times with anhydrous ethanol, and the obtained solid product was dried in a vacuum drying oven at 25°C for 24 hours.

[0070] The appearance of the obtained product is as follows Figure 2 The product has a purity of 98.2%, an average particle size of 385 μm, and a bulk density of 0.15 g / cm³. 3 The angle of repose is 39°.

[0071] By comparing Example 3 with Comparative Example 1, it can be seen that the spherical crystals obtained by the method of the present invention have smaller particle size, are more rounded and dense, and have better flowability.

[0072] Comparative Example 2:

[0073] The only difference from Example 1 is that ethanol was used as a poor solvent for crystallization during the preparation process, while the other conditions were the same as in Example 1.

[0074] Comparing Example 1 with Comparative Example 2, the crystal sphericity in Comparative Example 2 was very poor, and compact spherical particles could not be formed. When N,N-dimethylformamide and / or dimethyl sulfoxide are not used as unsuitable solvents during the preparation process, L-carnosine spherical products cannot be effectively obtained.

[0075] Comparative Example 3:

[0076] The only difference from Example 1 is that the crystallization temperature used in the preparation process is 40°C, while the other conditions are the same as in Example 1.

[0077] By comparing Example 1 with Comparative Example 3, the product obtained in Comparative Example 3 was an imperfect spherical crystal or a spherical crystal with low density. When the temperature was too high during the preparation process, the solubility of L-carnosine in the solution was high, and the solubility required for spherical growth could not be met during the crystallization process, resulting in imperfect spherical crystals.

[0078] The scanning electron microscope (SEM) images and XRD results of the product obtained by this invention are as follows: Figure 1 and Figure 3 As shown, compared with the morphology image obtained in Comparative Example 1, the product obtained by the present invention has better sphericity and integrity. XRD analysis reveals that the L-carnosine spherical crystals prepared by the present invention belong to the same crystal structure as the L-carnosine raw material, and no solid-phase transformation has occurred.

[0079] The preparation process of L-carnosine crystals using this invention is simple, involving only water and unsuitable solvents, resulting in a straightforward process. The particle size can be adjusted by varying the aqueous solution concentration and stirring rate, with an average particle size of 50–200 μm. The product particles are rounded, highly fluid, with an angle of repose of 30°–37° and a bulk density of 0.4–0.7 g / cm³. 3 This solved the problems of poor crystal morphology and poor particle flowability of L-carnosine.

[0080] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing L-carnosine spherical crystals, characterized in that, Includes the following steps: L-carnosine was dissolved in a good solvent to obtain a solution containing L-carnosine with a concentration of 0.05~0.3 g / g. The solution was stirred at 100~700 rpm at 20~35℃. An unsuitable solvent was added to the L-carnosine-containing solution at a rate of 0.2~0.7 mL / min. After the addition of the unsuitable solvent was completed, stirring was continued to grow crystals, and L-carnosine spherical crystals precipitated. After separation and drying, the L-carnosine spherical crystals were obtained. The good solvent is water; the bad solvent is N,N-dimethylformamide and / or dimethyl sulfoxide; the volume ratio of the bad solvent to the good solvent is 2~8:1; The L-carnosine spherical crystals are spherical particles; the average particle size of the L-carnosine spherical crystals is 50~130 μm, the angle of repose of the L-carnosine spherical crystals is 30~37°, and the bulk density of the L-carnosine spherical crystals is 0.4~0.7 g / cm³. 3 .

2. The preparation method according to claim 1, characterized in that, The concentration of L-carnosine in the solution containing L-carnosine is 0.1~0.2 g / g.

3. The preparation method according to claim 1, characterized in that, The stirring temperature is 25~30℃.

4. The preparation method according to claim 1, characterized in that, The stirring speed is 200~400 rpm.

5. The preparation method according to claim 1, characterized in that, The volume ratio of the poor solvent to the good solvent is 3~5:

1.

6. The preparation method according to claim 1, characterized in that, The crystal growth time is 0~4 h.

7. The preparation method according to claim 1, characterized in that, The crystal growth time is 1-2 hours.

8. The preparation method according to claim 1, characterized in that, After separation, the material is washed and dried; the washing method is to wash with ethanol or an aqueous ethanol solution 3 to 5 times.

9. The preparation method according to claim 1, characterized in that, The separation is a solid-liquid separation; the drying conditions are under reduced pressure.

10. The preparation method according to claim 1, characterized in that, The separation is achieved through filtration; the drying temperature is 25~50℃, and the time is 12~48 h.

11. The L-carnosine spherical crystals prepared by the method according to any one of claims 1 to 10, characterized in that, The L-carnosine spherical crystals are spherical particles; the average particle size of the L-carnosine spherical crystals is 50~130 μm; the angle of repose of the L-carnosine spherical crystals is 30~37°; and the bulk density of the L-carnosine spherical crystals is 0.4~0.7 g / cm³. 3 .

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