Crystal form of acetyl L-carnitine hydrochloride and preparation, composition and application thereof

Abstract

The invention discloses a crystal form A of acetyl L-carnitine hydrochloride, a preparation method of the crystal form A, and a bulk drug, a food additive, a feed additive and a composition containing the crystal form A. The crystal form A of the acetyl L-carnitine hydrochloride is good in solubility, high in stability, high in purity, regular in shape and suitable for being applied to bulk drugs, food additives and feed additives. The preparation method is simple in process, the crystal form A can be obtained at high yield through in-situ crystallization of a reaction solution and dispersion of ethanol, and the preparation method is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the fields of active pharmaceutical ingredients, food additives, and feed additives, specifically to a compound crystal form, its preparation method, composition, and uses. Background Technology

[0002] Acetyl-L-carnitine hydrochloride, commonly known as acetyl-L-carnitine chloride or acetyl-L-carnitine hydrochloride, is a naturally occurring substance found in the body, particularly abundant in muscles, the brain, and sperm. It participates in a series of important metabolic processes in the human body, removing acetyl groups from cells and assisting in energy transfer. It possesses functions such as muscle building, improved memory, nerve protection, and enhanced male sperm motility, and is therefore frequently used in food additives, health products, and pharmaceuticals. Multiple animal studies have confirmed that acetyl-L-carnitine hydrochloride supplementation can significantly improve sperm motility, density, and the proportion of normally morphological sperm in animals. Therefore, acetyl-L-carnitine hydrochloride also has wide applications in poultry breeding. Foods, health products, and feeds containing acetyl-L-carnitine hydrochloride are generally formulated as solid mixtures, liquid packets, or capsules for ease of consumption. Pharmaceuticals containing acetyl-L-carnitine hydrochloride are generally in the form of liquid injections or solid granules. Therefore, the purity, solubility, and stability of acetyl-L-carnitine hydrochloride raw materials are crucial to the quality of food, pharmaceuticals, and feed.

[0003] According to the method disclosed in Chinese Patent CN102557972A, crude acetyl-L-carnitine hydrochloride was crystallized with isopropanol to obtain a powdered refined acetyl-L-carnitine hydrochloride (crystal form I). Crystallization of the crude acetyl-L-carnitine hydrochloride with ethanol yielded irregular small granules of refined acetyl-L-carnitine hydrochloride (crystal form II). Recrystallization of the refined acetyl-L-carnitine hydrochloride with acetone yielded a powdered refined acetyl-L-carnitine hydrochloride (crystal form III). All three forms of solid acetyl-L-carnitine hydrochloride exhibit low content, solubility, and stability. No other superior crystal forms have been reported to date. Summary of the Invention

[0004] In view of the above-mentioned problems in the prior art, the present invention provides a technical solution to solve the above problems.

[0005] In a first aspect, the present invention provides a crystal form A of acetyl-L-carnitine hydrochloride, wherein the characteristic diffraction peaks of its X-ray powder diffraction pattern, expressed in 2θ using Cu-Ka radiation, include 11.746±0.2°, 23.464±0.2°, 20.824±0.2°, 14.965±0.2°, 26.373±0.2°, and 30.066±0.2°, but exclude 17.935±0.2° and 18.148±0.2°; preferably, during simultaneous thermal analysis, its differential scanning calorimetry spectrum shows a single absorption peak at 197.8±3℃; preferably, under normal temperature and pressure conditions, its solubility in pure water is greater than 850 mg / mL; preferably, its shape is a rectangular columnar body.

[0006] A second aspect of the present invention provides a method for preparing acetyl-L-carnitine hydrochloride crystal form A, the specific steps of which include: S1: Using L-carnitine and excess acetyl chloride as raw materials and acetic acid as solvent, an acetyl-L-carnitine hydrochloride solution was prepared. S2: Removes excess acetyl chloride and 85%~95% of acetic acid; S3: Acetyl-L-carnitine hydrochloride crystallizes in the remaining 5%~15% acetic acid solution; S4: Add ethanol to disperse the crystals in the obtained solid-liquid mixture; S5: Perform solid-liquid separation to obtain crystal form A.

[0007] Preferably, in step S3, a seed crystal of crystal form A is added before crystallization.

[0008] In a third aspect, the present invention provides a pharmaceutical ingredient comprising acetyl-L-carnitine hydrochloride crystal form A as described in the present invention or comprising acetyl-L-carnitine hydrochloride crystal form A prepared using the method described in the present invention.

[0009] In a fourth aspect, the present invention provides a food additive comprising acetyl-L-carnitine hydrochloride crystal form A as described in the present invention or comprising acetyl-L-carnitine hydrochloride crystal form A prepared using the method described in the present invention.

[0010] In a fifth aspect, the present invention provides a feed additive comprising acetyl-L-carnitine hydrochloride crystal form A as described in the present invention or comprising acetyl-L-carnitine hydrochloride crystal form A prepared using the method described in the present invention.

[0011] In a sixth aspect, the present invention provides the use of the crystal form A, the active pharmaceutical ingredient, or the composition described herein in muscle building, maintenance of nerve health, and maintenance of male reproductive health, preferably in the preparation of drugs, health products, or feeds for treating or preventing diseases selected from diseases such as muscular atrophy, neurological diseases, and male reproductive health issues.

[0012] A seventh aspect of the invention provides the use of the crystal form A, the active pharmaceutical ingredient, the feed additive, or the composition described in this application in maintaining the neurological health of poultry, assisting in poultry breeding, and increasing muscle content.

[0013] The positive effects of this invention are mainly reflected in the following aspects: (1) During industrial-scale trial production, the inventors used small-scale conditions to scale up the production and unexpectedly discovered that acetyl-L-carnitine hydrochloride could crystallize in the residual reaction solvent acetic acid during scale-up production. After adding ethanol to disperse the crystals, regular crystal form A could be obtained. This in-situ crystallization method is different from all crystallization methods disclosed in the prior art. The crystal form A obtained by this scale-up reaction is also different from the crystal morphology obtained by the small-scale experiment.

[0014] (2) Compared with the crystal forms I, II, and III disclosed in the prior art, the crystal form A described in this invention has the following advantages: regular shape, less tendency to clump, good stability under strong light and humid conditions, strong cohesion (low flowability), high tap density, and greater solubility. It has good advantages whether used as a raw material, food additive, or feed additive, such as convenient storage and transportation, stable quality, and better meeting consumer needs. On the other hand, raw materials with high tap density can be compressed into a smaller space, such as making smaller capsules or tablets, which are easier for patients to swallow.

[0015] (3) Acetyl L-carnitine hydrochloride is hygroscopic. Compared with crystal form A, crystal forms I, II and III of acetyl L-carnitine hydrochloride have stronger hygroscopicity. Therefore, crystal form A has stronger hygroscopic resistance and stronger stability in humid environments.

[0016] (4) This invention discovers that by in-situ crystallization of the reaction solution followed by the addition of ethanol to disperse the crystals, a regularly shaped rectangular columnar crystal form A can be obtained. Furthermore, in the particle group of crystal form A, based on weight ratio, more than 30% of the particles have a particle size of 425μm to 825μm. Compared to existing crystal forms in powder, flake, or irregular small particle form, the rectangular columnar crystal form A of this invention has a shorter filtration time and is less prone to clogging the filter during industrial production. It is also less likely to generate dust during drying and sieving, thus reducing the risk of clogging workshop ventilation pipes and minimizing the risk of safety accidents due to dust explosions.

[0017] (5) Existing technologies and conventional industrial production methods all involve concentrating the reaction solution. After all the solvent is concentrated, a dry crude acetyl-L-carnitine hydrochloride is obtained. The crude product is then recrystallized using isopropanol, acetone, and ethanol. This method is not only energy-intensive but also has a very low yield and produces an impure product. To improve the yield, the mother liquor after recrystallization is usually reused multiple times in industry. The method for preparing crystal form A described in this invention involves direct in-situ crystallization in the reaction solution, followed by dispersing the crystals by adding ethanol. This directly yields high-purity crystal form A with a regular shape in high yield, which not only improves production efficiency and reduces energy consumption but also enhances the stability of acetyl-L-carnitine hydrochloride. Attached Figure Description

[0018] Figure 1 This is the X-ray powder diffraction (XRPD) pattern of acetyl-L-carnitine hydrochloride crystal form A. The horizontal axis represents 2θ (º), and the vertical axis represents intensity (count). Figure 2 This is the X-ray powder diffraction (XRPD) pattern of acetyl-L-carnitine hydrochloride product B prepared in Example 3. The horizontal axis represents 2θ (º), and the vertical axis represents intensity (count). Figure 3 X-ray powder diffraction (XRPD) pattern of acetyl-L-carnitine hydrochloride crystal form I. The horizontal axis represents 2θ (º), and the vertical axis represents intensity (count). Figure 4 This is a simulated X-ray powder diffraction (XRPD) pattern of crystal form IV. Figure 5 These are photos of acetyl-L-carnitine hydrochloride crystals, type A, that have been stored for one year. Figure 6 These are photos of acetyl-L-carnitine hydrochloride crystal form I particles that have been stored for one year. Figure 7 This is the thermogravimetric analysis (TGA-DTG) spectrum of acetyl-L-carnitine hydrochloride crystal form A; Figure 8 This is a scanning electron microscope image of acetyl-L-carnitine hydrochloride crystal form A; Figure 9 This is a morphological diagram of acetyl-L-carnitine hydrochloride crystal form A; Figure 10 This is a morphological diagram of acetyl-L-carnitine hydrochloride crystal form I; Figure 11 This is a morphological diagram of acetyl-L-carnitine hydrochloride crystal form II; Figure 12 This is a morphological diagram of acetyl-L-carnitine hydrochloride crystal form III. Detailed Implementation

[0019] In one specific embodiment, the crystal form A uses Cu-Ka radiation, and the characteristic diffraction peaks of the X-ray powder diffraction pattern expressed in 2θ values ​​include any one or more of 211.746±0.2°, 23.464±0.2°, 20.824±0.2°, 14.965±0.2°, 26.373±0.2°, and 30.326±0.2°.

[0020] In one specific implementation, the crystal form A is subjected to Cu-Ka radiation, and the X-ray powder diffraction pattern expressed in 2θ values ​​is as follows: Figure 1 As shown.

[0021] In one specific implementation, differential scanning calorimetry (DSC) was used to analyze crystal form A. The DSC spectrum showed that crystal form A had an initial temperature of approximately 185.9 °C and a single absorption peak at approximately 197.8 °C. The TG spectrum showed that crystal form A had no significant mass change in the range of room temperature to 185.9 °C, with a mass retention rate of 100%. In the range of 185.9 °C to 210.9 °C, the mass loss rate was 55.63%, and in the range of 245.2 °C to 267.5 °C, the mass loss rate was 20.23%.

[0022] In one specific implementation scheme, the thermogravimetric analysis (DSC-TGA) spectrum of crystal form A is as follows: Figure 6 As shown. It should be noted that for the same crystal form, the position of the endothermic peak in DSC may vary due to factors such as the measuring instrument, measuring method / conditions, etc. The position of the endothermic peak may have an error of ±3℃ for any specific crystal form. Therefore, this error should be taken into account when determining each crystal form, and it is within the scope of this application.

[0023] It should be noted that since organic compounds containing hydrochloride salts easily decompose to release HCl, and HCl can easily corrode DSC instruments, under normal circumstances, DSC-TGA is used to perform thermogravimetric analysis on organic compounds containing hydrochloride salts.

[0024] In one specific implementation scheme, crystal form A was dissolved in pure water under normal temperature and pressure conditions. When an excess of crystal form A was added and crystal form A no longer dissolved, the solubility of crystal form A in pure water was analyzed. Three parallel experiments were conducted, and it was found that the solubility of crystal form A in pure water was greater than 850 mg / mL.

[0025] In one specific implementation scheme, under normal temperature and pressure conditions, simulating the gastric juice environment of the human body, a buffer solution with pH 1.2 was prepared. Crystal form A was dissolved in the buffer solution with pH 1.2. When an excess of crystal form A was added and crystal form A no longer dissolved, the solubility of crystal form A in the buffer solution with pH 1.2 was analyzed. Three parallel experiments were conducted, and it was found that the solubility of crystal form A in the buffer solution with pH 1.2 was greater than 830 mg / mL.

[0026] In one specific implementation scheme, under normal temperature and pressure conditions, simulating the intestinal fluid environment of the human body, a buffer solution with pH 6.8 was prepared. Crystal form A was dissolved in the buffer solution with pH 6.8. When an excess of crystal form A was added and crystal form A no longer dissolved, the solubility of crystal form A in the buffer solution with pH 6.8 was analyzed. Three parallel experiments were conducted, and it was found that the solubility of crystal form A in the buffer solution with pH 6.8 was greater than 800 mg / mL.

[0027] In one specific implementation, crystal form A is observed to be a rectangular columnar shape by visual inspection, mobile phone photography, or scanning electron microscopy (SEM). Compared to powders and amorphous materials, rectangular columnar shapes are easier to obtain during solid-liquid separation and require less filtration time.

[0028] In one specific implementation, the particle size and shape of the crystal form A particle group are analyzed by sieving. Among the crystal form A particles, by weight, particles with a diameter of 425μm to 825μm (20-40 mesh) account for 32.87%, particles with a diameter of 250μm to 425μm (40-60 mesh) account for 46.98%, and particles with a diameter of 180μm to 250μm (60-80 mesh) account for 17.45%.

[0029] In one specific implementation method, acetyl-L-carnitine hydrochloride is prepared as follows: S1: Mix L-carnitine with glacial acetic acid, heat to 65℃~75℃ to completely dissolve L-carnitine, cool to 15℃~25℃, slowly add excess acetyl chloride, and after the addition is complete, heat the reaction solution to 45℃~55℃ to carry out the reaction. S2: Reduced pressure distillation at 40℃~50℃ to remove excess acetyl chloride, and at 60℃~80℃ to remove 85%~95% of acetic acid; S3: Acetyl-L-carnitine hydrochloride crystals crystallize in the remaining 5%~15% acetic acid solution; S4: Add ethanol to disperse the crystals in the obtained solid-liquid mixture; S5: Perform solid-liquid separation to obtain crystal form A.

[0030] In a specific implementation, preferably, in step S1, the mass ratio of L-carnitine to glacial acetic acid is 1:2 to 1:2.2.

[0031] In one specific implementation, preferably, in step S1, the molar ratio of L-carnitine to acetyl chloride is 1:2 to 1:2.25.

[0032] In a specific implementation scheme, preferably, after the acetyl chloride is added in step S1, the mixture needs to be kept warm.

[0033] In a specific implementation, preferably, the distillation pressure in step S2 is -0.1 MPa to -0.05 MPa.

[0034] In a specific implementation, preferably, in step S3, before crystallization, a seed crystal of crystal form A is added.

[0035] In a specific implementation, preferably, in step S4, the mass ratio of ethanol to acetic acid is 7:1 to 24:1.

[0036] In a specific implementation, preferably, in step S4, after adding ethanol, the temperature is lowered to 10°C~20°C before solid-liquid separation is performed to obtain crystal form A.

[0037] The terminology used in this invention, such as "dispersed crystals," refers to the process of adding a poor solvent to a crystallization system to disperse aggregated crystals.

[0038] The term "solid-liquid separation" as used in this invention refers to separating the solid and liquid in a solid-liquid mixture by filtration; preferably, the "solid-liquid separation" further includes the step of drying the separated solid.

[0039] The terminology used in this invention, such as "crude compound," refers to substances with low purity and many impurities that require further purification before they can be used as "raw materials," "food additives," or "feed additives."

[0040] The terminology used in this invention, such as "refined compound," refers to a substance with increased purity compared to "crude compound." Specifically, it refers to a substance with high purity suitable for use as a "pharmaceutical raw material," "food additive," or "feed additive."

[0041] The terminology used in this invention, such as "active drug substance," refers to an active pharmaceutical ingredient (especially the active ingredient in a formulation) or synthetic intermediate that can be further used to prepare or produce various formulations. It is prepared by chemical synthesis or biotechnology and is intended to be used as a pharmaceutical powder, crystal, or other form, but is not intended for direct consumption by the subject.

[0042] In one specific embodiment, the weight percentage of crystal form A in the active pharmaceutical ingredient is 80.0% to 100%, for example, 81.0%, 82.0%, 83.0%, 84.0%, 85.0%, 86.0%, 87.0%, 88.0%, 89.0%, 90.0%, 91.0%, 92.0%, 93.0%, 94.0%, 95.0%, 96.0%, 97.0%, 98.0%, 99.0%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or 100%. In addition to crystal form A, the active pharmaceutical ingredient may also include amorphous forms of the compound, other crystal forms, water, or other substances within the permissible range of quality standards, such as impurities or solvent residues.

[0043] The term "food additive" as used in this invention refers to raw materials (especially active ingredients, also known as active ingredients) or synthetic intermediates that can be further used in the preparation or production of various foods and functional foods. These substances are prepared by chemical synthesis or biotechnology and are used as powders, crystals, or other forms of food or functional foods, but cannot be directly consumed in large quantities by the subjects.

[0044] In one specific embodiment, the weight percentage of crystal form A in the food additive is 80.0% to 100%, for example, 81.0%, 82.0%, 83.0%, 84.0%, 85.0%, 86.0%, 87.0%, 88.0%, 89.0%, 90.0%, 91.0%, 92.0%, 93.0%, 94.0%, 95.0%, 96.0%, 97.0%, 98.0%, 99.0%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or 100%. In addition to crystal form A, the food additive may also include amorphous forms of the compound, other crystal forms, water, or other substances within the permissible range of quality standards, such as impurities or solvent residues.

[0045] The terminology used in this invention, such as "feed additive," refers to raw materials (especially effective ingredients, also known as active ingredients) or synthetic intermediates that can be further used in the preparation or production of various feeds and functional feeds. These substances are prepared by chemical synthesis or biotechnology and are used as powders, crystals, or other forms of feed or functional feeds, but cannot be directly consumed in large quantities by test animals.

[0046] In one specific embodiment, the weight percentage of crystal form A in the feed additive is 80.0% to 100%, for example, 81.0%, 82.0%, 83.0%, 84.0%, 85.0%, 86.0%, 87.0%, 88.0%, 89.0%, 90.0%, 91.0%, 92.0%, 93.0%, 94.0%, 95.0%, 96.0%, 97.0%, 98.0%, 99.0%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, 99.9%, or 100%. In addition to crystal form A, the feed additive may also include amorphous forms of the compound, other crystal forms, water, or other substances within the permissible range of quality standards, such as impurities or solvent residues.

[0047] In one specific embodiment, the crystal form A described in this application constitutes 1% to 99.9% of the composition by weight. For example, the crystal form of the compound described in this application constitutes 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 5% by weight in the composition. 0%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.2%, 99.8%, 99.9%.

[0048] In one specific embodiment, the composition described in this application is a stable pharmaceutical composition.

[0049] In one specific implementation, the composition described in this application is a pharmaceutical composition, a special medical food composition, a health food composition, a functional food composition, a general food composition, a functional feed composition, or a general feed composition.

[0050] In one specific embodiment, this application provides a composition comprising the active pharmaceutical ingredient and one or more pharmaceutically acceptable excipients.

[0051] As used in this invention, the term "pharmaceuticalally acceptable excipient" refers to an excipient that does not cause significant irritation to organisms and does not impair the biological activity and properties of the administered active ingredient (such as crystal form A of the compound described in this invention or the active pharmaceutical ingredient). Specifically, pharmaceutically acceptable excipients include, but are not limited to: diluents, fillers, disintegrants, wetting agents, lubricants, pH adjusters, buffers, colorants, flavoring agents, preservatives, or other conventional additives.

[0052] The pharmaceutically acceptable excipients for forming a pharmaceutical composition with crystal form A as described in this invention may depend on the intended method of administering the pharmaceutical composition.

[0053] The crystal form A (or the active pharmaceutical ingredient) described in this invention may have systemic and / or local activity. Therefore, it can be administered in suitable manner, such as via oral, parenteral, pulmonary, nasal, sublingual, lingual, oral, rectal, vaginal, skin, transdermal, conjunctival, or auditory routes, or as an implant or scaffold. For these routes of administration, the crystal form of the compound described in this application can be administered in a suitable form.

[0054] As a specific embodiment of the present invention, the crystal form A, the active pharmaceutical ingredient, the food additive, or the composition are used in muscle building, maintaining nerve health, and maintaining male reproductive health.

[0055] As a specific embodiment of the present invention, the crystal form A, the active pharmaceutical ingredient, the feed additive, or the composition are used in maintaining the neurological health of poultry, assisting in poultry breeding, and increasing muscle content.

[0056] Unless otherwise specified, the content of acetyl-L-carnitine hydrochloride in this invention refers to the content relative to the standard.

[0057] Unless otherwise specified, the standard of acetyl-L-carnitine hydrochloride used in this invention was purchased from CATO Research Chemicals Inc.; conforming to ISO 17034:2016 and ISO 9001:2015 standards; batch number: No.:202509160160.

[0058] Unless otherwise specified, the purity of acetyl-L-carnitine hydrochloride in this invention refers to the percentage of the peak area of ​​acetyl-carnitine hydrochloride relative to the total peak area, calculated by peak area normalization under the liquid phase detection conditions described in this invention.

[0059] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0060] Example Example 1: Preparation of Acetyl-L-carnitine hydrochloride crystal form A A 20L-scale experiment was conducted. 3.22 kg of L-carnitine was mixed with 6.5 kg–7 kg of glacial acetic acid, and the mixture was heated to 65°C–75°C to completely dissolve the L-carnitine. The resulting solution was cooled to 15°C–25°C, and 3.14 kg of acetyl chloride was added dropwise over approximately 4 hours, maintaining the temperature for 1 hour. The reaction solution was then heated to 45°C–55°C and reacted for 4 hours. The remaining acetyl chloride was removed at -0.1 MPa to -0.05 MPa and 40°C–50°C. At MPa ~ -0.05 MPa and 60℃ ~ 80℃, 85% ~ 95% of acetic acid is removed, and acetyl-L-carnitine hydrochloride solid is precipitated. 7.5 kg ~ 8 kg of ethanol is added to the obtained solid-liquid mixture to disperse the solid. The mixture is stirred for 2 hours to dissolve impurities and a small amount of unreacted raw material. The temperature is lowered to 10℃ ~ 20℃ and kept at that temperature for one hour. Acetyl-L-carnitine hydrochloride crystals are filtered out, and the filtration time is recorded (Buchner funnel, -0.08 MPa). After filtration, the product is dried to obtain crystal form A.

[0061] Weigh the samples, analyze the content of crystal form A using HPLC, and analyze the mesh size and particle size of the prepared crystal form A particles using a sieve machine.

[0062] The analysis results are as follows: (1) The mass of crystal form A is 4.37 kg, the yield is 91.2%, and the content is 99.94% (relative to the standard).

[0063] (2) By weight, the particle size distribution of crystal form A is as follows: 32.87% of the particles are 20-40 mesh (425μm-825μm in diameter), 46.98% of the particles are 40-60 mesh (250μm-425μm in diameter), and 17.45% of the particles are 60-80 mesh (180μm-250μm in diameter).

[0064] The standard was purchased from CATO Research Chemicals Inc.; it conforms to ISO 17034:2016 and ISO 9001:2015 standards; lot number: No.: 202509160160).

[0065] Example 2: In-situ crystallization of acetyl-L-carnitine hydrochloride A 20L-scale experiment was conducted. 3.22 kg of L-carnitine was mixed with 6.5 kg to 7 kg of glacial acetic acid, mechanically stirred, and heated to 65℃ to 75℃ to completely dissolve the L-carnitine raw material. The resulting solution was cooled to 15℃ to 25℃, and 3.14 kg of acetyl chloride was added dropwise over approximately 4 hours, with the temperature maintained for 1 hour. The reaction solution was then heated to 45℃ to 55℃ and reacted for 4 hours. The remaining acetyl chloride was removed at -0.1 MPa to -0.05 MPa and 40℃ to 50℃. 85% to 95% of the acetic acid was removed at -0.1 MPa to -0.05 MPa and 60℃ to 80℃, precipitating acetyl-L-carnitine hydrochloride solid. Due to the high freezing point of acetic acid, the temperature was lowered to 20℃ to 30℃ and maintained for one hour. The acetyl-L-carnitine hydrochloride crystals were filtered out, dried, and in-situ crystallized acetyl-L-carnitine hydrochloride (block-shaped solid) was obtained.

[0066] Weighing and HPLC analysis showed that the mass of the blocky acetyl-L-carnitine hydrochloride was 4.12 kg, with a yield of 86.0% and a purity of 90.34% (relative to the standard).

[0067] A comparison of the experimental results from Examples 1 and 2 shows that if crystallization is performed directly in the acetic acid reaction solution, the resulting product is a blocky solid acetyl-L-carnitine hydrochloride. Not only is the yield low, but the content is also only 90.34% compared to the standard, indicating poor quality that does not meet the requirements for use as a food additive or pharmaceutical raw material. Furthermore, because acetic acid has a high freezing point (below 16°C), it solidifies on its own. Therefore, in conventional experiments and industrial production, acetic acid is not used as a crystallization solvent to allow the product to crystallize at low temperatures.

[0068] Example 3: Small-scale preparation of acetyl-L-carnitine hydrochloride Following the process parameters in Example 1, a small-scale preparation of acetyl-L-carnitine hydrochloride was carried out. 322g of L-carnitine was mixed with 650g-700g of glacial acetic acid, stirred magnetically, and heated to 65℃-75℃ to completely dissolve the L-carnitine raw material. The resulting solution was cooled to 15℃-25℃, and 314g of acetyl chloride was added dropwise over approximately 4 hours, with the mixture kept at this temperature for 1 hour. The reaction solution was then heated to 45℃-55℃ and reacted for 4 hours. The remaining acetyl chloride was removed at -0.1MPa to -0.05MPa and 40℃-50℃. Finally, 85%-95% of the acetic acid was removed at -0.1MPa to -0.05MPa and 60℃-80℃.

[0069] After most of the acetic acid was removed, a small amount of white powder precipitated out. The mixture was cooled to 10℃~20℃ and held for one hour to obtain a large amount of acetyl-L-carnitine hydrochloride powder. 75g~80g of ethanol was added to the obtained solid-liquid mixture, and the mixture was stirred for 2 hours to dissolve impurities and a small amount of unreacted raw material. The mixture was then cooled to 10℃~20℃ and held for one hour. The solid acetyl-L-carnitine hydrochloride was filtered out and dried to obtain a mixture of powdered and needle-like acetyl-L-carnitine hydrochloride (the morphology of the small-scale product differed from that of the pilot-scale product), designated as product B.

[0070] The weight of acetyl-L-carnitine hydrochloride was 389 g, and the yield was 81.3%, with a purity of 99.14% (relative to the standard). HPLC analysis showed that the yield of acetyl-L-carnitine hydrochloride was 389 g, the yield was 81.3%, and the purity was 99.14% (relative to the standard).

[0071] Example 4: Small-scale preparation of acetyl-L-carnitine hydrochloride crystal form A The process of Example 3 was improved while keeping other process conditions unchanged. After the reaction was completed, acetyl chloride was removed, and 85% of acetic acid was evaporated. Two crystals of crystal form A obtained in Example 1 were added to different positions of the reaction vessel. The temperature was lowered to 10°C to 20°C and kept at that temperature for 1 hour to obtain a small amount of rectangular columnar crystals. The temperature was kept at that temperature for 3 hours to obtain a large amount of rectangular columnar crystals. 75g to 80g of ethanol was added to the obtained solid-liquid mixture and stirred for 2 hours to dissolve impurities and a small amount of unreacted raw materials. The temperature was lowered to 10°C to 20°C and kept at that temperature for 1 hour. The solid acetyl-L-carnitine hydrochloride was filtered out and dried to obtain acetyl-L-carnitine hydrochloride crystal form A in the shape of rectangular columnar crystals.

[0072] The mass of acetyl-L-carnitine hydrochloride was 410.3 g, with a yield of 85.7% and a purity of 99.98% (relative to the standard). HPLC analysis showed that the yield was 85.7%.

[0073] As can be seen from Examples 3 and 4, without adding seed crystals, it is difficult to obtain crystal form A under small-scale conditions. After obtaining crystal form A by scaling up the reaction, crystal form A can be obtained by adding seed crystals of crystal form A to the small-scale system.

[0074] Example 5: Repeating the experiment in the CN102557972A publication. Repeat Examples 1, 2 and 3 in the CN102557972A publication to prepare acetyl-L-carnitine hydrochloride crystal form I (isopropanol crystal), crystal form II (ethanol crystal), and crystal form III (acetone crystal).

[0075] Example 6: XRPD Detection Experiment Crystal form A, product B, and crystal form I were sampled and ground. The ground powder was then subjected to XRPD testing. The testing methods are shown in Table 1.

[0076] Test results are shown Figure 1 , Figure 2 and Figure 3 : Figure 1 The X-ray powder diffraction pattern (XRPD) for crystal form A is shown. Figure 2 The X-ray powder diffraction pattern (XRPD) for product B is shown. Figure 3 This is the X-ray powder diffraction pattern (XRPD) of crystal form I.

[0077] Table 1: XRPD detection methods for crystal form A and crystal form I

[0078] Table 2 shows the X-ray powder diffraction pattern data corresponding to crystal form A after grinding, listing the diffraction angle 2θ and the relative intensity (expressed as a percentage relative to the strongest peak).

[0079] Table 2: X-ray powder diffraction pattern data of crystal form A

[0080] Table 3 shows the X-ray powder diffraction pattern data of product B after grinding, listing the diffraction angle 2θ and the relative intensity (expressed as a percentage relative to the strongest peak).

[0081] Table 3: X-ray powder diffraction pattern data of product B

[0082] Table 4 shows the X-ray powder diffraction pattern data corresponding to crystal form I after grinding, which lists the diffraction angle 2θ and the relative intensity (expressed as a percentage relative to the strongest peak).

[0083] Table 4: X-ray powder diffraction pattern data of crystal form I

[0084] Example 7: XRPD peak simulation was performed on the crystal form disclosed in HP Weber, Acetyl-L-carnitine Hydrochloride, ActaCryst. (1995). C51, 2570-2572.

[0085] The aforementioned literature obtained crystal IV of acetyl-L-carnitine hydrochloride by diffusing acetone vapor into a methanol-saturated solution containing dissolved hydrochloride. The unit cell parameters of crystal IV are as follows: a = 8.571 ± 0.001 α = 90° b = 8.842 ± 0.001β - 90° c=16.607±0.001γ=90° Using the cell parameters obtained from the CCDC in this paper, XRPD pattern simulation was performed using Mercury software. The resulting pattern is shown below. Figure 4 .

[0086] Depend on Figure 1 , Figure 2 , Figure 3 , Figure 4 It can be seen that the XRPD diagrams of crystal form A are different from those of product B, crystal form I, and crystal form IV.

[0087] Example 8: The experiment in the CN102557972A publication was scaled up and compared with Example 1 in terms of filtering time and the ease of product clumping.

[0088] According to the process conditions of Example 1 in the CN102557972A publication, the feed of L-carnitine was scaled up to 3.22 kg, and the feed amounts of acetyl chloride, acetic acid, and isopropanol were scaled up accordingly. The filtration time (Buchner funnel, -0.08 MPa) was recorded, and the obtained product was dried to obtain crystal form I.

[0089] Take 100g each of the crystal form A product obtained in Example 1 and the crystal form I product obtained in the above-mentioned scaled-up preparation, put them into a dry sealed bag, and place the sealed bag containing the products in a cool and dry cardboard box for one year to observe the clumping situation. Figure 5 Crystal form A after one year of storage. Figure 6 Crystal form I after one year of storage.

[0090] The filtration time and product agglomeration in Examples 1 and 8 are analyzed in Table 5.

[0091] Table 5: Comparison of filtration time and clumping status

[0092] As can be seen from the filtration times of Examples 1 and 8, the rectangular columnar crystal form A is easier to filter, which can greatly reduce the filtration time in industrial production and improve production efficiency. On the other hand, since crystal form A consists of regularly shaped particles, it is less likely to generate dust during drying and sieving, and is less likely to clog the ventilation devices in the finishing workshop in industrial production, nor is it likely to cause hazards such as dust explosions.

[0093] Depend on Figure 5 and Figure 6 It can be seen that crystal form A did not clump after one year, while crystal form I clumped after one year. The experimenters found that crystal form III showed obvious clumping after one month, and some crystal particles of crystal form II agglomerated into clumps after one month.

[0094] Example 9: Content Comparison Experiment The crystal forms A, I, II, and III prepared in Examples 1 and 5 were prepared into solutions and compared with the standard (purchased from CATO Research Chemicals Inc.; conforming to ISO 17034:2016 and ISO 9001:2015 standards; batch number: No.: 202509160160). The content was analyzed based on HPLC data, and the data are shown in Table 6.

[0095] Table 6: Comparison of the content of crystal form A with crystal forms I, II, and III

[0096] By comparing with the standard, we found that crystal form III had the lowest content of acetyl-L-carnitine hydrochloride, followed by crystal form I, crystal form II could reach 99%, while crystal form A could reach 99.9%.

[0097] Example 10: Hygroscopicity and stability under humid conditions Accurately weigh approximately 10 mg of each sample from crystal form A, crystal form I, crystal form II, and crystal form III using a 0.01 g balance, place them into lyophilized plastic vials, and then accurately weigh the total weight of the vials after adding the samples. After sampling, simultaneously place all samples openly in a 1 L glass beaker, maintaining an ambient temperature of 25°C and a humidity of 60% RH. After 15 days, remove the vials and accurately weigh them. Simultaneously, detect changes in HPLC purity and impurities. Changes in mass after moisture absorption are shown in Table 7, and changes in purity and impurities are shown in Table 8.

[0098] Table 7: Sample weight change over time under humid conditions

[0099] As shown in Table 7, under humid conditions, crystal form A has the best resistance to moisture absorption, crystal form I has the worst resistance, crystal form II has the second best resistance, and crystal form III has the third best resistance.

[0100] Table 8: Changes in sample purity and impurities over time under humid conditions

[0101] Note a: Under the same testing conditions, the purity of the standard is 74.23%.

[0102] As shown in Table 8, crystal form A has the best stability in a humid environment. Crystal forms I, II, and III show a sharp decrease in purity and a sharp increase in the content of croton betaine impurities in a humid environment.

[0103] Example 11: Solubility Comparison Experiment The specific method is as follows: (1) Prepare a buffer solution with pH 1.2 Weigh 0.2g of KCl solid, dissolve it in about 50mL of pure water, and then slowly add 0.2M hydrochloric acid (measure 1.7mL of concentrated hydrochloric acid and slowly add it to about 80mL of pure water, cool it and then make up to 100mL to obtain 0.2M hydrochloric acid) to adjust the pH of the solution to 1.2±0.05 and set aside.

[0104] (2) Prepare a pH 6.8 buffer solution Weigh 0.68g of potassium dihydrogen phosphate solid, dissolve it in about 70mL of pure water, and adjust the pH to 6.80±0.05 with 1M sodium hydroxide solution.

[0105] (3) Sample preparation Under normal temperature and pressure conditions, acetyl-L-carnitine crystal forms A, I, II, and III were dissolved in 1 mL centrifuge tubes containing 0.15 mL of pure water, 0.15 mL of a buffer solution with pH 1.2, and 0.15 mL of a buffer solution with pH 6.8, respectively, until saturated. After standing for a short time, the supernatant was taken for HPLC analysis. The experiment was repeated three times in parallel, and the acetyl-L-carnitine hydrochloride content in each saturated supernatant was calculated. The pH 1.2 buffer solution simulated the environment in gastric juice, and the pH 6.8 buffer solution simulated the environment in intestinal juice.

[0106] The experimental results are shown in Table 9.

[0107] The experimental results show that crystal form A has the highest solubility in pure water, a buffer solution with pH 1.2, and a buffer solution with pH 6.8. In pure water, the solubility of crystal form A exceeds 850 mg / mL; in a buffer solution with pH 1.2, the solubility exceeds 830 mg / mL; and in a buffer solution with pH 6.8, the solubility exceeds 800 mg / mL. The solubilities of crystal forms I, II, and III are all below 800 mg / mL in all three solutions.

[0108] Example 12: Liquidity Experiment (1) Loose density test: Take four accurately graduated sample vials and weigh them precisely using a balance of 0.01%. Let crystal form A, crystal form I, crystal form II, and crystal form III fall into each vial in a free-fall state until the top of the solid is level with the 1mL mark. Gently scrape the top with a spatula, accurately weigh the total loose weight of each sample, and calculate the loose density of each crystal.

[0109] (2) Tap density test: The vial containing four samples in (1) was dropped vertically from a height of 2-3 cm in a free-fall manner. This was repeated several times, with the corresponding crystal sample added at the same time, until the top of the tapped solid was level with the 1 mL mark. The top was then leveled with a spatula. The total tapped weight of each sample was accurately weighed, and the tapped density of each crystal was calculated.

[0110] Flowability = (tap density - loose density) / tap density × 100%, experimental data are shown in Table 10.

[0111] Table 10: Liquidity Experiment Data

[0112] As shown in Table 10, crystal form A has the highest tap density, and can hold 0.6726 g of sample in a 1 mL vial. If the same mass of crystal form I were placed in a vial, it would require 1.35 mL of volume space. Therefore, using crystal form A as a raw material allows it to be compressed into a smaller space, such as smaller capsules or tablets, making it easier for patients to swallow.

[0113] As can be seen from the experimental data in Table 10, crystal form A has lower fluidity. For downstream products of acetyl-L-carnitine hydrochloride, such as premixes containing acetyl-L-carnitine hydrochloride (food additives or feed additives), low fluidity can effectively reduce the separation or stratification caused by vibration during transportation and storage, and maintain the homogeneity of the mixture.

[0114] Example 13: Illumination Stability Test Four parallel samples were taken from each of crystal form A, crystal form I, crystal form II, and crystal form III, with each sample weighing 20 mg. The samples were then spread evenly on the bottom of four 1 mL quartz glass vials, which were placed open in a light chamber for intense light irradiation at an intensity of 4500 lx ± 500 lx and a temperature of 25 °C. Samples were taken and analyzed on the 6th and 12th days of irradiation to compare the changes in the content of each sample. The experimental results are shown in Table 11.

[0115] Table 11: Changes in purity and content under light conditions

[0116] As can be seen from the experimental data in Table 11, under illumination, the contents of crystal form A, crystal form I, crystal form II and crystal form III all decrease, but the content of crystal form A decreases the least. Therefore, under illumination, crystal form A is the most stable.

[0117] Example 14: TG-DSC Detection TG-DSC was performed on crystal form A, and the detection method is shown in Table 12.

[0118] Figure 7 The thermogravimetric analysis (TGA-DTG) spectrum of crystal form A is shown.

[0119] Table 12: TG-DSC Detection Methods

[0120] Example 15: Scanning Electron Microscopy (SEM) Analysis Samples of crystal form A were taken and analyzed by scanning electron microscopy. The detection methods are shown in Table 13, and the detection results are shown in [Table 13]. Figure 8 .

[0121] Table 13: SEM Detection Methods

[0122] The SEM images show that crystal form A is a rectangular columnar structure.

Claims

1. A crystal form A of acetyl-L-carnitine hydrochloride, characterized in that, Using Cu-Ka radiation, the characteristic diffraction peaks of the X-ray powder diffraction pattern, expressed in 2θ, include 11.746±0.2°, 23.464±0.2°, 20.824±0.2°, 14.965±0.2°, 26.373±0.2°, and 30.066±0.2°, but do not include 17.935±0.2° and 18.148±0.2°.

2. The crystal form A as described in claim 1, characterized in that, The X-ray powder diffraction pattern of crystal form A is basically as shown in Figure 1.

3. Crystal form A as described in claim 1, characterized in that, The differential scanning calorimetry spectrum of crystal form A shows a single absorption peak at 197.8±3℃.

4. Crystal form A as described in claim 1, characterized in that, The crystal form A is a rectangular columnar shape.

5. Crystal form A as described in claim 1, characterized in that, The solubility of crystal form A in pure water at room temperature is greater than 850 mg / mL.

6. A method for preparing acetyl-L-carnitine hydrochloride crystal form A, characterized in that, The process includes the following steps: S1: Using L-carnitine and excess acetyl chloride as raw materials and acetic acid as solvent, prepare an acetyl-L-carnitine hydrochloride solution; S2: Remove excess acetyl chloride and 85%~95% of acetic acid; S3: Crystallize the acetyl-L-carnitine hydrochloride in the remaining 5%~15% acetic acid solution; S4: Add ethanol to the obtained solid-liquid mixture to disperse the crystals; S5: Perform solid-liquid separation to obtain crystal form A.

7. The method according to claim 6, characterized in that, In step S3, before crystallization, a seed crystal of crystal form A is added.

8. The method according to claim 6, characterized in that, In step S4, the mass ratio of ethanol to acetic acid is 7:1 to 24:

1.

9. A pharmaceutical raw material, food additive, or feed additive, characterized in that, It includes crystal form A as described in any one of claims 1 to 5 or crystal form A prepared by the method described in any one of claims 6 to 8.

10. The active pharmaceutical ingredient, food additive, or feed additive as described in claim 9, characterized in that... The weight percentage of crystal form A in the active pharmaceutical ingredient, food additive, or feed additive is 80.0% to 100%.

11. The active pharmaceutical ingredient, food additive, or feed additive as described in claim 9, characterized in that, Based on particle size, more than 30% of the crystal form A in the active pharmaceutical ingredient, food additive, or feed additive has a particle size of 425μm to 825μm by weight.

12. A composition, characterized in that, It comprises crystal form A according to any one of claims 1 to 5 or crystal form A prepared by the method according to any one of claims 6 to 8, and one or more pharmaceutically acceptable excipients.

13. The application of crystal form A as described in any one of claims 1 to 5, or crystal form A prepared by the method described in any one of claims 6 to 8, in muscle growth, maintenance of nerve health, and maintenance of male reproductive health.

14. The composition of claim 12, for use in muscle building, maintenance of nerve health, and maintenance of male reproductive health.

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