A method for preparing a crystal of highly water-soluble chlortetracycline hydrochloride

Abstract

The invention discloses a crystallization preparation method of a highly water-soluble chlortetracycline hydrochloride, specifically comprising the steps of dissolving, filtering, washing, acidifying, crystallizing, by studying the crystallization kinetics of chlortetracycline hydrochloride in the extraction process, crystallization thermodynamics, key parameters such as crystallization saturation curve theory, it is a kind of chlortetracycline hydrochloride extraction process that only needs to strictly control the crystallization process conditions in the secondary crystallization process, not only can the product content be improved, but also the product solubility is improved, the present invention can make the chlortetracycline hydrochloride product chlortetracycline content ≥ 92% in the European Pharmacopoeia detection standard (abbreviated as EP method), much higher than the standard of ≥ 89.5% in the European Pharmacopoeia, greatly reducing the potential risk caused by the product content not reaching the standard. The most critical point of the present invention is to greatly improve the product solubility after crystallization, reaching 0.92-1.0g / 100mL, 25°C, which is 2-4 times higher than the solubility of the original control sample.

Description

Technical Field

[0001] The invention belongs to the technical field of extraction and synthesis of antibiotics for veterinary use, and in particular relates to a method for preparing a crystal of highly water-soluble chlortetracycline hydrochloride. Background Art

[0002] Chlortetracycline (CTC), also known as chlortetracycline, has a chemical formula of C 22 H 23 ClN2O8, molecular weight is 478.88. In 1948, it was the first tetracycline antibiotic discovered by Benjamin Duggar from Streptomyces aureofaciens. The mechanism of action of chlortetracycline is that the drug can specifically bind to the A site of the 30S subunit of the bacterial ribosome, inhibit the growth of the peptide chain and affect the synthesis of bacterial proteins. It has a broad-spectrum inhibitory effect on many microorganisms such as Gram, Rickettsia, Mycoplasma, Chlamydia, and spirochetes.

[0003] Chlortetracycline is widely used as a basic drug in formulas or combined with other veterinary drugs to make compound preparations due to its mature production process, high potency, low cost of use, high safety and many other advantages. The main products on the market are Chlortetracycline Premix, Chlortetracycline Hydrochloride and its soluble powder.

[0004] Chlortetracycline hydrochloride is a salt formed by fermentation and extraction of Streptomyces aureus and finally combined with hydrochloric acid, referred to as CTC·HCl. Chlortetracycline hydrochloride products are golden yellow or yellow crystals, odorless, bitter, and gradually darken when exposed to light. They are slightly soluble in water or ethanol, and almost insoluble in acetone, ether or chloroform. As a human drug, it is mainly used to treat conjunctivitis and trachoma. As a veterinary drug, it is mainly used to treat typhoid fever, white diarrhea and other diseases in livestock and poultry.

[0005] At present, there have been many studies on the extraction method of chloramphenicol hydrochloride. For example, Chinese patent application No. CN201210426529.0 discloses a method for preparing chloramphenicol hydrochloride. After sufficient fermentation of Streptomyces aureus, the fermentation broth is purified and hydrochloric acid is added to refine the salt. The method includes acidification, plate and frame filtration, precipitation, coarse crystallization, filtration, extraction, crystallization, washing, drying, mixing and other steps. The process flow is optimized, the reaction steps are reduced, the extraction cycle is shortened, the product is stable, and the chloramphenicol hydrochloride content reaches 91-92%.

[0006] For another example, Chinese patent application number CN201010218988.0 discloses a new process for preparing chlortetracycline hydrochloride, wherein the chlortetracycline fermentation broth is pretreated, the filtrate is taken, a metal divalent salt is added, and the pH value is adjusted to 6.0-9.0 with an alkali to generate chlortetracycline divalent metal salt; the chlortetracycline divalent metal salt is dissolved in a monohydric alcohol with an acid and filtered, the filtrate is added with a filtered saturated chloride solution to precipitate chlortetracycline hydrochloride, the precipitate is filtered, washed, and dried to obtain the chlortetracycline hydrochloride product, the process is simple, only one crystallization is required, hydrochloric acid is not used in the crystallization process, and chloride is used to dissociate Cl - Under acidic conditions, it combines with chlortetracycline to form chlortetracycline hydrochloride.

[0007] For another example, Chinese patent application number CN201410057354.X discloses a method for preparing chlortetracycline hydrochloride, which is characterized in that its process steps are: first, the chlortetracycline fermentation broth is acidified, the pH is adjusted to 2.0-2.5, and then allowed to stand, and the pH is further adjusted to 4.0-4.5, and then allowed to stand and water is added to reduce its viscosity to 3000-4000 cP for pretreatment, and then membrane filtration, nanofiltration, crystallization, washing, salt formation, elution and drying are carried out in sequence to obtain chlortetracycline hydrochloride powder.

[0008] At present, due to equipment investment, environmental protection and other issues, most manufacturers still use the secondary solvent crystallization method to produce chlortetracycline hydrochloride, that is, chlortetracycline fermentation broth is refined through acidification, filtration, crystallization, dissolution, recrystallization and many other steps. However, chlortetracycline hydrochloride has poor solubility and is slightly soluble in water or ethanol. According to feedback on the use of commercially available chlortetracycline hydrochloride in recent years, chlortetracycline hydrochloride will encounter a thorny problem when used - low solubility. Generally, the solubility in drinking water is only 0.2-0.4g / 100mL at 25℃. In order to improve the solubility of chlortetracycline hydrochloride, Chinese patent application number CN202110908430.3 discloses a method for preparing ultra-high water-soluble chlortetracycline hydrochloride, which specifically includes the following steps: 1) acidification of fermentation broth; 2) double salt; 3) coarse crystal; 4) extraction; 5) recrystallization; 6) high-pressure homogenization: the material obtained in the previous step is subjected to high-pressure homogenization, with purified water as the dispersion medium, the water-to-material ratio is 1: (1-1.5), and the number of times is 10-12; 7) spray drying: the material obtained in the previous step is spray dried, the feed frequency is 20Hz, and the inlet air temperature is controlled at 175-180℃, and ultra-high water-soluble chlortetracycline hydrochloride is obtained, with a solubility of 0.9g / 100mL, 25℃. Although this method can greatly improve the solubility of chlortetracycline hydrochloride, this method is further processed by physical and chemical methods at the back end of the product, which requires additional equipment and energy input, which is bound to increase production costs.

[0009] In summary, how to develop a crystallization process that can improve the solubility of chloramphenicol hydrochloride in a high-quality, low-cost, green and environmentally friendly manner based on the original extraction process has become an innovative breakthrough that chloramphenicol hydrochloride manufacturers are striving to find in order to improve product quality and enhance product market competitiveness. Summary of the invention

[0010] The purpose of the present invention is to solve the problems of low solubility and low product content of chlortetracycline hydrochloride extracted products in the prior art. By studying the key parameters such as the crystallization kinetics, crystallization thermodynamics, and crystallization saturation curve theory of chlortetracycline hydrochloride in the extraction process, a method for preparing chlortetracycline hydrochloride with high water solubility is provided. The method is a method for preparing chlortetracycline hydrochloride with high water solubility, which only requires strict control of the crystallization process conditions in the secondary crystallization process. The method is a chlortetracycline hydrochloride extraction process that can not only increase the product content, but also improve the product solubility.

[0011] The main purpose of the present invention is achieved through the following technical solutions:

[0012] A method for preparing a crystal of highly water-soluble chlortetracycline hydrochloride comprises the following steps:

[0013] 1) preparing a dissolving solution for dissolving chlortetracycline hydrochloride: weighing 7-9 parts of inorganic chloride salt by weight, dissolving in 100 parts of monohydric alcohol, stirring to dissolve, controlling the stirring speed at 200-250 rpm, heating in a water bath during the process to accelerate the dissolution, and after the dissolution is completed, allowing the solution to stand at room temperature for use;

[0014] 2) The solution obtained in the above step is placed in a low-temperature water bath for cooling treatment, and 1000 ml of the solution is added at a ratio of 80-120% per 100 million chlortetracycline units (V / 100 million), and the chlortetracycline hydrochloride sample is weighed, and then the chlortetracycline hydrochloride is added to the solution for stirring and dissolving, and the stirring speed is controlled at 160-200 rpm. The pH of the solution is adjusted with an alkaline solution to accelerate the dissolution, and finally a chlortetracycline hydrochloride solution with a pH of 6.5-7.0 and no agglomerated impurities in the solution (indicating that it has been fully dissolved) is obtained, and the temperature is kept at 15-25°C during the period;

[0015] 3) Separate the chlortetracycline solution obtained in the above step through a filtration device, use the solution in step 1) to wash the chlortetracycline remaining in the filtration device, combine the filtrate and the washing liquid, take the clarified filtrate, detect the titer of the clarified filtrate, and control the titer to 70000-100000 μg / mL, and keep the temperature at 15-25° C.;

[0016] 4) preheating the clarified filtrate obtained in the above step in a water bath and stirring, controlling the stirring speed at 160-200rpm to make it heated evenly and reduce the generation of impurities. After reaching the preheating temperature, adding hydrochloric acid at a ratio of 8.0-12% (V / 100 million), that is, adding 0.08-0.12 liters of hydrochloric acid for every 100 million units of hydrochloride, adding hydrochloric acid evenly, after the addition of hydrochloric acid is completed, keeping the pH of the chlortetracycline hydrochloride crystal system at 0.4-0.7, increasing the stirring speed to 350-500rpm, heating to the crystallization insulation temperature, and keeping the temperature for 30-50min to obtain a chlortetracycline hydrochloride crystal mixture;

[0017] 5) The chlortetracycline hydrochloride crystal mixture obtained in the previous step is filtered by the filtering device in step 3) to obtain chlortetracycline hydrochloride wet crystals, and the residual crystallization mother liquor is rinsed with purified water with a volume of 1 / 15-1 / 25 of the crystallization mixture, and the crystallization mother liquor is rinsed 2-3 times with anhydrous ethanol with a volume of 1 / 15-1 / 25 of the crystallization mixture. After filtering, the chlortetracycline hydrochloride wet crystals are dried by a drying device to obtain chlortetracycline hydrochloride crystals;

[0018] 6) The chlortetracycline hydrochloride crystals obtained in the above step are subjected to solubility testing to obtain highly water-soluble chlortetracycline hydrochloride.

[0019] In the present invention:

[0020] The inorganic chloride salt in step 1) is selected from one or two of magnesium chloride and calcium chloride, and when mixed, they are in any proportion; the monohydric alcohol is selected from one or two of methanol and ethanol, and when mixed, they are in any proportion; the water bath is heated at a temperature of 30-45°C. The cooling treatment in step 2) is controlled within the range of 15-25°C; the unit of chloramphenicol per billion refers to the definition of 1 μg / mL as one unit, and 100 million units as 1×10 8 μg / mL; the chlortetracycline hydrochloride sample refers to a crude crystalline product with a chlortetracycline content of 75-92% or a commercially available sample after secondary crystallization; the alkaline solution is selected from 18-25 (v / v)% ammonia water.

[0021] The filtering device described in step 3) is a vacuum filtration device, a small plate-and-frame device, a refrigerated centrifuge or a combination thereof; the amount of the dissolved solution used in step 1) is generally 1 / 10-1 / 20 of the volume of the dissolved solution in step 2).

[0022] The water bath preheating temperature in step 4) is 28-32°C; the temperature raised to the crystallization insulation temperature is 35-45°C.

[0023] The drying equipment described in step 5) is selected from a blast drying oven or a vacuum heating drying oven.

[0024] The solubility test described in step 6) is to test the solubility of multiple batches according to the solubility test method of the Chinese Pharmacopoeia.

[0025] The present invention also relates to a highly water-soluble chlortetracycline hydrochloride obtained by the above-mentioned crystallization preparation method of highly water-soluble chlortetracycline hydrochloride, with a solubility of 0.92-1.0 g / 100 mL, 25° C., no sedimentation occurs within two weeks of sealed placement, a narrow particle size distribution range of 0.4-100 μm, mainly distributed in 4-80 μm, a more concentrated particle size distribution, and a more uniform particle size; under a magnification of 160 times of an optical microscope, it is light yellow, composed of a plurality of tiny small crystals gathered together, distributed in clusters in an aggregated state, similar to the shape of crystal growth, with a large crystal structure specific area, existing in a non-restrictive expansion system, and having gaps between cluster structures; according to the E.P10.0 detection method, liquid chromatography is used to detect the content, and the highly water-soluble chlortetracycline hydrochloride obtained has a chlortetracycline content of ≥92%, which is higher than the standard of E.P10.0 ≥89.5%, and other impurity components are all within the qualified range, fully meeting the export standard of chlortetracycline hydrochloride.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. The crystallization preparation method of a highly water-soluble chlortetracycline hydrochloride described in the present invention can make the chlortetracycline hydrochloride product have a chlortetracycline content of ≥92% in the European Pharmacopoeia test standard (EP method for short), which is much higher than the standard of ≥89.5% in the European Pharmacopoeia, greatly reducing the potential risk caused by the failure of the product content to meet the standard. In addition, the solubility of chlortetracycline hydrochloride obtained by the secondary crystallization process in the prior art is 0.2-0.4g / 100mL, and the most significant point of the present invention is that the solubility of the product after the crystallization of chlortetracycline hydrochloride is greatly improved. The solubility of the highly water-soluble chlortetracycline hydrochloride prepared by the method of the present invention is 0.92-1.0g / 100mL, 25°C, and no sedimentation occurs within two weeks of sealed placement. Therefore, the process of the present invention can increase the solubility by 2-4 times on the original basis, which has a significant improvement effect.

[0028] 2. The method for preparing a highly water-soluble chlortetracycline hydrochloride by crystallization described in the present invention is an innovative adjustment based on the existing secondary crystallization process, which does not change the crystallization process, does not require additional equipment investment, does not increase labor costs, is easy to operate, and is easy to promote and apply. The chlortetracycline hydrochloride raw material obtained by the present invention can be expanded to the soluble powder industry derived from it through its own high water solubility advantage, helping the chlortetracycline hydrochloride soluble powder to improve its own solubility and enhance product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a diagram of the structural formula of chlortetracycline hydrochloride;

[0030] Figure 2It is a comparison chart of the solubility of chlortetracycline hydrochloride prepared by two processes (the left one is the secondary crystallization process of the prior art, and the right one is the preparation process of the present invention);

[0031] Figure 3 The crystal structures of two kinds of chlortetracycline hydrochloride under a 160x optical microscope (the left one is the secondary crystallization process of the prior art, and the right one is the preparation process of the present invention);

[0032] Figure 4 It is a particle size distribution diagram of chlortetracycline hydrochloride obtained by the secondary crystallization process of the prior art;

[0033] Figure 5 This is a particle size distribution diagram of highly water-soluble chlortetracycline hydrochloride obtained by the inventive method of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below by way of examples, but these examples should not be considered as limiting the present invention.

[0035] Embodiment 1:

[0036] A method for preparing a crystal of highly water-soluble chlortetracycline hydrochloride comprises the following steps:

[0037] 1) Prepare 4000 mL of solution required to dissolve chlortetracycline hydrochloride: weigh 8 parts of inorganic chloride salt by weight, dissolve in 100 parts of monohydric alcohol, stir to dissolve, control the stirring speed at 200-250 rpm, heat in a water bath during the process to accelerate the dissolution, and after the dissolution is complete, let the solution stand at room temperature for use;

[0038] The inorganic chloride salt is selected from 7.5 parts of magnesium chloride and 0.5 parts of calcium chloride; the monohydric alcohol is selected from ethanol; the stirring speed is controlled at 220 rpm; the water bath heating temperature is 40°C;

[0039] 2) The solution obtained in the above step is placed in a low-temperature water bath for cooling treatment, and 1000 ml of the solution is added at a ratio of 100% per 100 million chlortetracycline units (V / 100 million), and the chlortetracycline hydrochloride sample is weighed, and then the chlortetracycline hydrochloride is added to the solution for stirring and dissolving, and the stirring speed is controlled at 180 rpm. The pH of the solution is adjusted with an alkaline solution to accelerate the dissolution, and finally a chlortetracycline hydrochloride solution with a pH of 6.8 and no agglomerate impurities in the solution (indicating that it has been fully dissolved) is obtained, and the temperature is kept at 20°C during the period;

[0040] The cooling treatment is controlled within the range of 20°C; the chlortetracycline units are defined as 1 μg / mL as one unit, and 100 million units as 1×10 8μg / mL; the chlortetracycline hydrochloride sample refers to a crude crystalline product with a chlortetracycline content of 75-92% or a commercially available sample after secondary crystallization. This weighing is 365g, and the crude crystalline product with a chlortetracycline content of 82.19%; the alkaline solution is selected from 23 (v / v)% ammonia water;

[0041] 3) The chlortetracycline solution obtained in the above step is separated by a filtration device, and the solution of step 1) is used to wash the chlortetracycline remaining in the filtration device, the filtrate and the washing liquid are combined, and the clarified filtrate is taken to detect the potency of the clarified filtrate, and the potency is controlled at 85000 μg / mL, and the temperature is kept at 20°C during the period;

[0042] The filtering device is a vacuum filtration device, a small plate-and-frame device, a refrigerated centrifuge or a combination thereof; the amount of the solution used in step 1) is generally 1 / 15 of the volume of the solution in step 2);

[0043] 4) Preheat the clarified filtrate obtained in the above step in a water bath and stir, control the stirring speed at 180rpm, so that it is heated evenly and the generation of impurities is reduced. After reaching the preheating temperature, add hydrochloric acid at a ratio of 10% (V / 100 million), that is, add 0.10 liters of hydrochloric acid for every 100 million units of hydrochloride, and add the hydrochloric acid evenly. After the addition of hydrochloric acid is completed, keep the pH of the chloramphenicol hydrochloride crystal system at 0.55, increase the stirring speed to 420rpm, raise the temperature to the crystallization insulation temperature, and keep the temperature for 40min to obtain a chloramphenicol hydrochloride crystal mixture;

[0044] The water bath preheating temperature is 30°C; the temperature raised to the crystallization insulation temperature is 40°C;

[0045] 5) filtering the chloramphenicol hydrochloride crystal mixture obtained in the previous step using the filtering device in step 3) to obtain chloramphenicol hydrochloride wet crystals, washing the residual crystal mother liquor with 1 / 20 volume of purified water of the crystal mixture, and washing twice with 1 / 20 volume of anhydrous ethanol of the crystal mixture. After filtering, the chloramphenicol hydrochloride wet crystals are dried by a drying device to obtain chloramphenicol hydrochloride crystal fine products;

[0046] The drying equipment is selected from a vacuum heating drying oven;

[0047] 6) The chlortetracycline hydrochloride crystalline fine product obtained in the previous step is tested for solubility in multiple batches according to the solubility test method of the Chinese Pharmacopoeia to obtain highly water-soluble chlortetracycline hydrochloride.

[0048] The highly water-soluble chlortetracycline hydrochloride obtained in Example 1, E.P10.0 test result:

[0049] The CTC content is 93.89%, the TC content is 4.02%, the impurity A content is 1.81%, the impurity D content is 0.05%, the impurity B content is 0.07%, the impurity E content is 0.57%, the impurity J content is 0.02%, the impurity G content is 0.00%, the impurity H content is 0.09%, the impurity L content is 0.03%, the impurity K content is 0.00%, and the single unknown content is 0.00%. The chlortetracycline content and impurity components are both qualified, and 300.4g of chlortetracycline hydrochloride fine product is obtained, with a CTC yield of 94.0%.

[0050] EP10.0 Standard:

[0051] CTC content ≥89.5%, TC content ≤6.0%, impurity A content ≤4.0%, impurity D content ≤0.2%, impurity B content ≤1.0%, impurity E content ≤1.0%, impurity J content ≤0.3%, impurity G content ≤0.2%, impurity H ≤0.2%, impurity L content ≤0.2%, impurity K ≤0.15%, single unknown content ≤0.1%.

[0052] Embodiment 2:

[0053] A method for preparing a crystal of highly water-soluble chlortetracycline hydrochloride comprises the following steps:

[0054] 1) Prepare 7000 mL of solution required to dissolve chlortetracycline hydrochloride: weigh 7 parts of inorganic chloride salt by weight, dissolve in 100 parts of monohydric alcohol, stir to dissolve, control the stirring speed at 200 rpm, heat in a water bath during the process to accelerate the dissolution, and after the dissolution is complete, let the solution stand at room temperature for use;

[0055] The inorganic chloride salt is selected from 7 parts of magnesium chloride; the monohydric alcohol is selected from a mixture of 95% by volume ethanol and 5% by volume methanol; the water bath heating temperature is 30°C;

[0056] 2) The solution obtained in the above step is placed in a low-temperature water bath for cooling treatment, and 1000 ml of the solution is added at a ratio of 80% per 100 million chlortetracycline units (V / 100 million), and the chlortetracycline hydrochloride sample is weighed, and then the chlortetracycline hydrochloride is added to the solution for stirring and dissolving, and the stirring speed is controlled at 160 rpm. The pH of the solution is adjusted with an alkaline solution to accelerate the dissolution, and finally a chlortetracycline hydrochloride solution with a pH of 6.5 and no agglomerated impurities in the solution (indicating that it has been fully dissolved) is obtained, and the temperature is kept at 15 ° C during the period;

[0057] The cooling treatment is controlled at 15°C; the chlortetracycline units are defined as 1 μg / mL as one unit, and 100 million units are 1×10 8μg / mL; the appropriate amount of chlortetracycline hydrochloride sample is 665.1 g of a crystalline crude product with a chlortetracycline content of 75.18%; the alkaline solution is an aqueous ammonia solution with a concentration of 18%;

[0058] 3) The chlortetracycline solution obtained in the above step is separated by a filtration device, and the solution of step 1) is used to wash the chlortetracycline remaining in the filtration device, the filtrate and the washing liquid are combined, and the clarified filtrate is taken to detect the potency of the clarified filtrate, and the temperature is kept at 15° C. during the process;

[0059] The filtering device is a vacuum filtration device; the amount of the solution in step 1) is generally 1 / 10 of the volume of the solution in step 2); the titer is controlled within a suitable range, which is controlled at 100000 μg / mL in this case;

[0060] 4) Preheat the clarified filtrate obtained in the above step in a water bath and stir, control the stirring speed at 160rpm, so that it is heated evenly and the generation of impurities is reduced. After reaching the preheating temperature, add hydrochloric acid at a ratio of 8.0-12% (V / 100 million), that is, add 0.08-0.12 liters of hydrochloric acid for every 100 million units of hydrochloride, and add hydrochloric acid evenly. After the addition of hydrochloric acid is completed, keep the pH of the chloramphenicol hydrochloride crystal system at 0.4-0.7, increase the stirring speed to 350-500rpm, raise the temperature to the crystallization insulation temperature, and keep the temperature for 30-50min to obtain a chloramphenicol hydrochloride crystal mixture;

[0061] The water bath preheating temperature is 28°C; the range of adding hydrochloric acid in a certain proportion is 8.0-12% ((V / 100 million), that is, 0.08-0.12 liters of hydrochloric acid are added for every 100 million units of hydrochloride, and 8.0% is used this time. At this time, the pH of the chlortetracycline hydrochloride crystallization system is maintained at 0.40; the stirring speed is increased to 350rpm; the temperature is raised to the crystallization insulation temperature is 35°C;

[0062] 5) The chlortetracycline hydrochloride crystal mixture obtained in the previous step is filtered by the filtering device in step 3) to obtain chlortetracycline hydrochloride wet crystals, and the residual crystallization mother liquor is rinsed with purified water with a volume of 1 / 15 of the crystallization mixture, and is rinsed twice with anhydrous ethanol with a volume of 1 / 15 of the crystallization mixture. After the filtration is completed, the chlortetracycline hydrochloride wet crystals are dried by a drying device to obtain chlortetracycline hydrochloride crystals;

[0063] The drying equipment is selected from a blast drying oven;

[0064] 6) The chlortetracycline hydrochloride crystalline fine product obtained in the previous step is tested for solubility in multiple batches according to the solubility test method of the Chinese Pharmacopoeia to obtain highly water-soluble chlortetracycline hydrochloride.

[0065] The highly water-soluble chlortetracycline hydrochloride obtained in Example 2, E.P10.0 test result:

[0066] The CTC content is 92.91%, the TC content is 5.17%, the impurity A content is 1.57%, the impurity D content is 0.04%, the impurity B content is 0.28%, the impurity E content is 0.49%, the impurity J content is 0.02%, the impurity G content is 0.00%, the impurity H content is 0.11%, the impurity L content is 0.05%, the impurity K content is 0.00%, and the single unknown content is 0.00%. The chlortetracycline content and impurity components are both qualified, and 508.6g of chlortetracycline hydrochloride fine product is obtained, with a CTC yield of 94.5%.

[0067] Embodiment 3:

[0068] A method for preparing a crystal of highly water-soluble chlortetracycline hydrochloride comprises the following steps:

[0069] 1) Prepare 4000 mL of solution required to dissolve chlortetracycline hydrochloride: weigh 7-9 parts of inorganic chloride salt by weight, dissolve in 100 parts of monohydric alcohol, stir to dissolve, control the stirring speed at 200-250 rpm, heat in a water bath during the process to accelerate the dissolution, and after the dissolution is complete, let the solution stand at room temperature for use;

[0070] The inorganic chloride salt is selected from 8.5 parts of magnesium chloride and 0.5 parts of calcium chloride; the monohydric alcohol is selected from a mixture of 95% by volume ethanol and 5% by volume methanol; the water bath heating temperature is 45°C;

[0071] 2) Place the solution obtained in the previous step in a low-temperature water bath for cooling treatment, add 1000 ml of solution at a ratio of 120% per 100 million chlortetracycline units (V / 100 million), weigh the chlortetracycline hydrochloride sample, and then add chlortetracycline hydrochloride to the solution for stirring and dissolving, control the stirring speed at 200 rpm, use an alkaline solution to adjust the pH of the solution to accelerate the dissolution, and finally obtain a chlortetracycline hydrochloride solution with a pH of 7.0 and no agglomerate impurities in the solution (indicating that it has been fully dissolved), and keep the temperature controlled at 25°C during the period;

[0072] The cooling treatment is controlled at 25°C; the chlortetracycline unit is defined as 1 μg / mL as one unit, and 100 million units are 1×10 8 μg / mL; the weighed amount of chlortetracycline hydrochloride sample refers to a commercial product with a chlortetracycline content of 91.23%, 548.1 g; the alkaline solution is ammonia water with a concentration of 25%;

[0073] 3) The chlortetracycline solution obtained in the above step is separated by a filtration device, and the solution of step 1) is used to wash the chlortetracycline remaining in the filtration device, the filtrate and the washing liquid are combined, and the clarified filtrate is taken to detect the potency of the clarified filtrate, and the potency is controlled at 70000 μg / mL, and the temperature is kept at 25°C during the period;

[0074] The filtering device is a vacuum filtration device; the amount of the solution in step 1) is generally 1 / 20 of the volume of the solution in step 2);

[0075] 4) Preheat the clarified filtrate obtained in the above step in a water bath and stir, control the stirring speed at 200 rpm, so that it is heated evenly and the generation of impurities is reduced. After reaching the preheating temperature, add hydrochloric acid at a ratio of 8.0-12% (V / 100 million), that is, add 0.08-0.12 liters of hydrochloric acid for every 100 million units of hydrochloride, and add hydrochloric acid evenly. After the addition of hydrochloric acid is completed, keep the pH of the chlortetracycline hydrochloride crystal system at 0.4-0.7, increase the stirring speed to 500 rpm, raise the temperature to the crystallization insulation temperature, and keep the temperature for 30-50 minutes to obtain a chlortetracycline hydrochloride crystal mixture;

[0076] The water bath preheating temperature is 32°C; the range of adding hydrochloric acid in a certain proportion is 8.0-12% ((V / 100 million), that is, 0.08-0.12 liters of hydrochloric acid are added for every 100 million units of hydrochloride, and 12% is used this time. At this time, the pH of the chlortetracycline hydrochloride crystallization system is maintained at 0.40; the stirring speed is increased to 500rpm; the temperature is increased to the crystallization insulation temperature is 45°C;

[0077] 5) The chlortetracycline hydrochloride crystal mixture obtained in the previous step is filtered by the filtering device in step 3) to obtain chlortetracycline hydrochloride wet crystals, and the residual crystallization mother liquor is rinsed with purified water with a volume of 1 / 25 of the crystallization mixture, and is rinsed three times with anhydrous ethanol with a volume of 1 / 25 of the crystallization mixture. After the filtration is completed, the chlortetracycline hydrochloride wet crystals are dried by a drying device to obtain chlortetracycline hydrochloride crystals;

[0078] The drying equipment is selected from a blast drying oven;

[0079] 6) The chlortetracycline hydrochloride crystalline fine product obtained in the previous step is tested for solubility in multiple batches according to the solubility test method of the Chinese Pharmacopoeia to obtain highly water-soluble chlortetracycline hydrochloride.

[0080] The highly water-soluble chlortetracycline hydrochloride obtained in Example 3, E.P10.0 test result:

[0081] The CTC content is 93.19%, the TC content is 4.07%, the impurity A content is 2.02%, the impurity D content is 0.06%, the impurity B content is 0.06%, the impurity E content is 0.59%, the impurity J content is 0.02%, the impurity G content is 0.00%, the impurity H content is 0.09%, the impurity L content is 0.03%, the impurity K content is 0.00%, and the single unknown content is 0.00%. The chlortetracycline content and impurity components are both qualified, and 503.3g of chlortetracycline hydrochloride fine product is obtained, with a CTC yield of 93.8%.

[0082] Comparative Example:

[0083] The preparation method of chlortetracycline hydrochloride secondary crystallization process in the prior art comprises the following steps:

[0084] 1) Acidification: Cool 20 L of chlortetracycline fermentation broth to 20° C., add oxalic acid at a volume ratio of 1.5% (g / mL), and adjust the pH to 1.4 with concentrated hydrochloric acid;

[0085] 2) Purification: Then, ferroxanthate (sodium salt) and zinc sulfate were added to the fermentation broth at a weight volume ratio of 0.2% (g / mL), wherein ferroxanthate and zinc sulfate were at a weight ratio of 1:1, and stirred for 30 minutes, and then polyacrylamide polymer after Mannich reaction was added at a volume ratio of 0.8% (v / v), stirred for 20 minutes, and the stirred fermentation broth was filtered through a plate and frame filter to obtain 10L of acidified filtrate;

[0086] 3) Double salt precipitation: add 0.10-0.35% (w / v) magnesium chloride and 0.05-0.10% (w / v) calcium carbonate, and add 25% ammonia water while stirring, adjust the pH to 7.6-7.9, and form chlortetracycline calcium magnesium double salt after reaction and precipitate, and pump it into plate and frame filtration to obtain chlortetracycline calcium magnesium double salt;

[0087] 4) Coarse crystallization: prepare 26-35% (liter / billion) of ethanol of the total amount of filtrate and washing liquid in a coarse crystal tank, gradually add the wet product of chlortetracycline calcium magnesium double salt unloaded from the plate frame under stirring, after all the double salt is added, add 11-15% (liter / billion) of hydrochloric acid of the total amount of filtrate and washing liquid, continue stirring until the double salt is completely dissolved, raise the temperature to 45-49°C, keep warm for 45-60min, obtain a crystallization liquid containing CTC.HCl coarse crystals, filter the coarse crystal liquid by plate and frame, and obtain coarse crystals of chlortetracycline hydrochloride after filtration;

[0088] 5) Extraction: prepare 90-110% (liters / billion) of ethanol of the total amount of filtrate and washing liquid in the extraction tank, then add 7% (w / v) of magnesium chloride of the actual amount of ethanol used and stir until dissolved, gradually add crude chlortetracycline hydrochloride under stirring, control the temperature below 25°C, slowly add ammonia water, adjust the pH value to 6.5-7.0, cool the crude crystal solution to 15-19°C, pump it to plate and frame filtration, and then filter it through a membrane to obtain an extract;

[0089] 6) Recrystallization: Pump the extract into a crystallization tank and preheat to 25-29°C. Add 10-20% (v / v) industrial hydrochloric acid that has been treated by membrane filtration while stirring, and heat. Control the temperature at 45-50°C, keep warm and stir for 40-60 minutes to obtain chlortetracycline hydrochloride crystals. After filtration and drying, 100g of chlortetracycline hydrochloride sample is obtained, and the total yield is about 75%.

[0090] result:

[0091] The secondary crystallization product of chlortetracycline hydrochloride was tested by EP10.0:

[0092] CTC content is 91.23%, TC content is 4.90%, impurity A content is 1.41%, impurity D content is 0.11%, impurity B content is 0.10%, impurity E content is 0.44%, impurity J content is 0.07%, impurity G content is 0.00%, impurity H content is 0.08%, impurity L content is 0.10%, impurity K content is 0.01%, and a single unknown content is 0.00%. The chlortetracycline content and impurity components are both qualified, and the solubility in drinking water is 0.30g / 100mL at 25°C. With the help of an optical microscope, similar to the attached Figure 3 As shown in the figure, under 160 times magnification, the chlortetracycline hydrochloride produced by the original secondary crystallization process is light yellow with dispersed single flake-like three-dimensional structure. With the help of dry particle size detection, it can be seen that the particle size distribution range of chlortetracycline hydrochloride produced by the original secondary crystallization process is relatively wide, 0.4-200μm, similar to the attached Figure 4 As shown, the particle size distribution is mainly between 6 and 150 μm, and is relatively dispersed.

[0093] Results and Analysis:

[0094]

[0095] 1. The highly water-soluble chlortetracycline hydrochloride obtained in Examples 1-3 was subjected to solubility testing. The solubility was tested according to the solubility test method of the Chinese Pharmacopoeia. The solubility in drinking water was 0.92, 1.0, and 0.95 g / 100 mL at 25 ° C. No sedimentation occurred within two weeks of sealed placement, and the dissolution effect was similar to that of the attached Figure 2At present, the solubility of 1.0 g / 100 mL is basically the limit of the current chlortetracycline hydrochloride crystallization process. The present invention can achieve a solubility of 0.92-1.0 g / 100 mL by optimizing the crystallization process without adding additional extraction steps.

[0096] Chinese patent application number CN202110908430.3 discloses a method for preparing ultra-high water-soluble chlortetracycline hydrochloride, which is after the crystallization process, that is, it is already a qualified final product of crystallization, and then a further physical and chemical method processing (i.e., "high pressure homogenization" step) is carried out to achieve a solubility of 1.0. Although this method can greatly improve the solubility of chlortetracycline hydrochloride, this method is a further processing at the back end of the product, which requires additional equipment and energy input, which is bound to increase production costs. In addition, optimizing the crystallization process is the technical route for improving solubility in the traditional sense recognized by most chlortetracycline hydrochloride manufacturers, and this method is a downstream improvement after the completion of the entire chlortetracycline hydrochloride extraction production process, which is equivalent to extending the traditional secondary crystallization process, and does not belong to any link in the traditional chlortetracycline hydrochloride extraction production process. Therefore, the method of the present invention is a different technical route, which can achieve the purpose of ultimately improving solubility, and the present invention also additionally improves the purity of chlortetracycline content.

[0097] Figure 2 This is a comparison chart of the solubility of chlortetracycline hydrochloride prepared by two processes (the left side is the secondary crystallization process of the prior art, and the right side is the preparation process of the present invention).

[0098] 2. With the help of an optical microscope, similar to the one shown in the attached Figure 3 As shown, Figure 3 The crystal structures of two kinds of chlortetracycline hydrochloride under a 160x optical microscope (the left one is the secondary crystallization process of the prior art, and the right one is the preparation process of the present invention);

[0099] Under a magnification of 160 times, the chloramphenicol hydrochloride produced by the secondary crystallization process of the comparative example is light yellow with a dispersed single flaky three-dimensional structure, while the highly water-soluble chloramphenicol hydrochloride obtained by the crystallization preparation method of the embodiment is light yellow and is composed of a plurality of smaller crystals gathered together in the form of aggregated clusters, similar to the shape of crystal growth. This crystal structure has a larger specific area and exists as a non-restrictive expansion system. There are gaps between the cluster structures, and the physical and chemical bonding forces such as the van der Waals force and hydrogen bond between the small crystals in the cluster are smaller than those of the single crystals in the original secondary crystallization, thereby achieving the effect of rapid dispersion into the solvent system and continuously maintaining the existence of a steady-state equilibrium solution system.

[0100] 3. By means of dry particle size detection, it can be seen that the particle size distribution range of chlortetracycline hydrochloride in the secondary crystallization process of the comparative example is relatively wide, 0.4-200 μm, similar to the attached Figure 4As shown, the particle size distribution is mainly between 6 and 150 μm, and the particle size distribution is relatively dispersed;

[0101] The particle size distribution range of the highly water-soluble chlortetracycline hydrochloride obtained by the crystallization preparation method in the embodiment is relatively narrow, ranging from 0.4 to 100 μm, similar to the attached Figure 5 As shown, it is mainly distributed in 4-80μm, the particle size distribution is more concentrated, and the particle size is more uniform. According to the E.P10.0 detection method, the content is detected by liquid chromatography. The high water-soluble chlortetracycline hydrochloride in the embodiment has a chlortetracycline content of 92.91-93.89%, which is higher than the standard of E.P10.0 ≥ 89.5%, and other impurity components are within the qualified range, fully meeting the export standard of chlortetracycline hydrochloride.

[0102] Figure 4 It is a particle size distribution diagram of chlortetracycline hydrochloride obtained by the secondary crystallization process of the prior art;

[0103] Figure 5 This is a particle size distribution diagram of highly water-soluble chlortetracycline hydrochloride obtained by the inventive method of the present invention.

[0104] The comparison of the basic properties of the embodiment and the comparative example shows that the preparation method of the embodiment is obviously better than that of the comparative example.

Claims

1. A method for preparing a highly water-soluble chlortetracycline hydrochloride crystal, characterized in that: The steps include: 1) preparing a dissolving solution for dissolving chlortetracycline hydrochloride: weighing 7-9 parts of inorganic chloride salt by weight, dissolving in 100 parts of monohydric alcohol, stirring to dissolve, controlling the stirring speed at 200-250 rpm, heating in a water bath during the process to accelerate the dissolution, and after the dissolution is completed, allowing the solution to stand at room temperature for use; 2) The solution obtained in the above step is placed in a low-temperature water bath for cooling treatment, and 1000 ml of the solution is added at a ratio of V / 100 million according to 80-120% of each 100 million chlortetracycline units. The chlortetracycline hydrochloride sample is weighed, and then the chlortetracycline hydrochloride is added to the solution for stirring and dissolving. The stirring speed is controlled at 160-200 rpm, and the pH of the solution is adjusted with an alkaline solution to accelerate the dissolution, and finally a chlortetracycline hydrochloride solution with a pH of 6.5-7.0 and no agglomerate impurities in the solution is obtained, and the temperature is kept at 15-25 ° C during the period; 3) Separate the chlortetracycline solution obtained in the above step through a filtration device, use the solution in step 1) to wash the chlortetracycline remaining in the filtration device, combine the filtrate and the washing liquid, take the clarified filtrate, detect the titer of the clarified filtrate, and control the titer to 70000-100000 μg / mL, and keep the temperature at 15-25° C.; 4) preheating the clarified filtrate obtained in the above step in a water bath and stirring, controlling the stirring speed at 160-200rpm to make it heated evenly and reduce the generation of impurities. After reaching the preheating temperature, adding hydrochloric acid at a ratio of 8.0-12% V / 100 million, that is, adding 0.08-0.12 liters of hydrochloric acid for every 100 million units of hydrochloride, adding hydrochloric acid evenly, after the addition of hydrochloric acid is completed, keeping the pH of the chlortetracycline hydrochloride crystal system at 0.4-0.7, increasing the stirring speed to 350-500rpm, heating to the crystallization insulation temperature, and keeping the temperature for 30-50min to obtain a chlortetracycline hydrochloride crystal mixture; 5) The chlortetracycline hydrochloride crystal mixture obtained in the previous step is filtered by the filtering device in step 3) to obtain chlortetracycline hydrochloride wet crystals, and the residual crystallization mother liquor is rinsed with purified water with a volume of 1 / 15-1 / 25 of the crystallization mixture, and the crystallization mother liquor is rinsed 2-3 times with anhydrous ethanol with a volume of 1 / 15-1 / 25 of the crystallization mixture. After filtering, the chlortetracycline hydrochloride wet crystals are dried by a drying device to obtain chlortetracycline hydrochloride crystals; 6) The chlortetracycline hydrochloride crystals obtained in the above step are subjected to solubility testing to obtain highly water-soluble chlortetracycline hydrochloride.

2. The method for preparing a highly water-soluble chlortetracycline hydrochloride crystal according to claim 1, characterized in that: The inorganic chloride salt in step 1) is selected from one or both of magnesium chloride and calcium chloride, and they are in any proportion when mixed; the monohydric alcohol is selected from one or both of methanol and ethanol, and they are in any proportion when mixed; the water bath is heated at a temperature of 30-45°C.

3. The method for preparing a highly water-soluble chlortetracycline hydrochloride crystal according to claim 1, characterized in that: The cooling treatment in step 2) is controlled within the range of 15-25°C; the chlortetracycline unit is defined as 1 μg / mL as one unit, and 100 million units are 1×10 8 μg / mL; the chlortetracycline hydrochloride sample refers to a crude crystalline product with a chlortetracycline content of 75-92% or a commercially available sample after secondary crystallization; the alkaline solution is selected from 18-25v / v% ammonia water.

4. The method for preparing a highly water-soluble chlortetracycline hydrochloride crystal according to claim 1, characterized in that: The filtering device described in step 3) is a vacuum filtration device, a small plate-and-frame device, a refrigerated centrifuge or a combination thereof; the amount of the dissolved solution used in step 1) is generally 1 / 10-1 / 20 of the volume of the dissolved solution in step 2).

5. The method for preparing a highly water-soluble chlortetracycline hydrochloride crystal according to claim 1, characterized in that: The water bath preheating temperature in step 4) is 28-32°C; the temperature raised to the crystallization insulation temperature is 35-45°C.

6. The method for preparing a highly water-soluble chlortetracycline hydrochloride crystal according to claim 1, characterized in that: The drying equipment described in step 5) is selected from a blast drying oven or a vacuum heating drying oven.

7. The method for preparing a highly water-soluble chlortetracycline hydrochloride crystal according to claim 1, characterized in that: The solubility test described in step 6) is to test the solubility of multiple batches according to the solubility test method of the Chinese Pharmacopoeia.

8. A highly water-soluble chlortetracycline hydrochloride, characterized in that: The highly water-soluble chlortetracycline hydrochloride is obtained by the crystallization preparation method of any one of claims 1 to 7, with a solubility of 0.92-1.0 g / 100 mL, and no sedimentation occurs within two weeks of sealing at 25°C. The particle size distribution range is 0.4-100 μm. Under a magnification of 160 times under an optical microscope, it is light yellow and is composed of a plurality of tiny small crystals gathered together in the form of aggregated clusters, similar to the shape of crystal growth. The crystal structure has a large specific area and exists in a non-restrictive expansion system. There are gaps between the cluster structures. According to the E.P10.0 detection method, the content is detected using liquid chromatography, and the obtained highly water-soluble chlortetracycline hydrochloride has a chlortetracycline content of ≥92%.

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