A method for preparing hydroxybutyl chitosan
The one-pot reaction in ethanol medium for the preparation of hydroxybutyl chitosan solves the problems of low substitution degree, numerous side reactions, and high cost in existing technologies, achieving a high-efficiency and low-cost preparation process suitable for the production of hydroxybutyl chitosan in the biopharmaceutical field.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARVEST PHARMA HUNAN CO LTD
- Filing Date
- 2026-04-10
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies for hydroxybutyl chitosan have low substitution rates, numerous side reactions, high production costs, and complex processes, resulting in low production efficiency.
Ethanol was used as the reaction medium, and chitosan, 1,2-epoxybutane and sodium hydroxide were directly mixed in a one-pot reaction. By controlling the reaction conditions and post-processing steps, the preparation process was simplified and the grafting efficiency and purity were improved.
It significantly improves the grafting efficiency and purity of hydroxybutyl chitosan, reduces production costs, simplifies production steps, and improves production efficiency, making it suitable for large-scale industrial production.
Smart Images
Figure CN122167615A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of biomedical technology, and in particular to a method for preparing hydroxybutyl chitosan. Background Technology
[0002] Chitosan is a natural biopolymer synthesized from chitin through deacetylation. Its molecular chain contains two active functional groups: -NH2 and -OH. Modification of these functional groups can form compounds with different structures and properties, suitable for various applications. Hydroxybutyl chitosan (HBC) is a modified polysaccharide obtained by introducing hydroxybutyl groups into the chitosan molecular chain. It retains the natural biological activity of chitosan and exhibits temperature-sensitive properties and good water solubility, making it widely used in wound dressings, drug delivery, and tissue repair.
[0003] For example, according to publication numbers CN116143954A and CN102276756B, existing technologies for preparing hydroxybutyl chitosan generally employ a stepwise method. The core steps involve first alkalizing the chitosan, removing excess alkali, and then subjecting the alkalized chitosan to a nucleophilic ring-opening addition reaction with 1,2-epoxybutane, branching hydroxybutyl side links onto the chitosan backbone. Finally, drying yields hydroxybutyl chitosan. In aqueous systems, due to strong hydrogen bonds and a rigid structure, chitosan molecular chains may violently aggregate or form dense gels in alkaline water, resulting in the internal hydroxyl and amino groups being "encapsulated," leading to uneven alkalization. A large number of water molecules will strongly solvate (surround) the OH groups. - and the generated chitosan amino anions (-NH - ) and hydroxyl oxygen anion (-O - The presence of hydroxybutyl chitosan, to some extent, masks its nucleophilic activity, resulting in low substitution levels. Furthermore, existing technologies use alkaline aqueous solutions as the reaction solvent. 1,2-Epoxybutane readily undergoes hydrolysis and ring-opening, and readily polymerizes under alkaline catalysis, leading to raw material waste, increased production costs, and impurities from hydrolysis affecting the purity of the final product. Additionally, existing preparation methods typically use 10 mL of 50% NaOH aqueous solution per 1 g of chitosan during alkalization, requiring approximately 7.5 g of sodium hydroxide, resulting in high usage and production costs. Moreover, existing preparation methods involve complex steps and long production times. Summary of the Invention
[0004] Therefore, it is necessary to provide a method for preparing hydroxybutyl chitosan to solve the problems of low degree of substitution, numerous side reactions, and low efficiency in the existing traditional aqueous phase method.
[0005] To achieve the above objectives, this application provides a method for preparing hydroxybutyl chitosan, which includes the following steps:
[0006] Step (1): Add chitosan, ethanol, 1,2-epoxybutane and sodium hydroxide to the reaction flask. The concentration of ethanol is 50%-95%. Stir at 60℃-70℃ for 18h-48h to obtain the first solution.
[0007] Step (2): Cool the first solution to 20℃-30℃, adjust the pH to 7-8 with hydrochloric acid, add hot water at 50℃-60℃, and stir at 50℃-60℃ for 0.2h-1h to obtain a second solution with flocculent matter;
[0008] Step (3): Filter the second solution to obtain a filter cake. Wash the filter cake with hot water at 50℃-60℃ and then filter it to obtain the initial product.
[0009] Step (4): Dry the initial product at 50℃-60℃ for 8h-24h to obtain hydroxybutyl chitosan.
[0010] Optionally, in step (1), the ratio of ethanol to chitosan is 3g:1g to 15g:1g.
[0011] Preferably, in step (1), the ratio of ethanol to chitosan is 6g:1g.
[0012] Optionally, in step (1), the ratio of 1,2-epoxybutane to chitosan is 3g:1g to 15g:1g.
[0013] Preferably, in step (1), the ratio of 1,2-epoxybutane to chitosan is 6g:1g.
[0014] Optionally, in step (1), the ratio of sodium hydroxide to chitosan is 0.01g:1g to 0.08g:1g.
[0015] Preferably, in step (1), the ratio of sodium hydroxide to chitosan is 0.02g:1g.
[0016] Optionally, in step (1), the concentration of ethanol is 95%.
[0017] Optionally, in step (2), the amount of hot water added is 400g.
[0018] Optionally, in step (3), the amount of hot water used is 200g.
[0019] Compared with the prior art, the beneficial effects of the method for preparing hydroxybutyl chitosan provided in this application are as follows:
[0020] (1) The way in which ethanol breaks the hydrogen bonds between chitosan molecules may be different from that of water. Ethanol has a moderate swelling effect on chitosan, which can penetrate into the interior of chitosan without completely dissolving it. This may put the chitosan molecular chain in a swollen but more conducive to the exposure of functional groups, greatly improving the accessibility of amino and hydroxyl groups and increasing the grafting efficiency (degree of substitution).
[0021] (2) The solubility of 1,2-epoxybutane in ethanol is much better than its solubility in water. Ethanol, as a homogeneous medium, can better accommodate both the hydrophobic 1,2-epoxybutane and the swollen chitosan, forming a more homogeneous reaction microenvironment, which greatly improves mass transfer and makes the reaction proceed faster and more uniformly at the molecular level.
[0022] (3) Although ethanol is also a nucleophile, its nucleophilicity is much weaker than that of water, and even weaker than that of amino anions. Therefore, in the ethanol system, the side reaction of 1,2-epoxybutane hydrolysis by water is greatly suppressed, and it reacts almost exclusively with the highly reactive chitosan amino and hydroxy anions, thereby significantly improving the grafting efficiency (degree of substitution). Moreover, the suppression of 1,2-epoxybutane hydrolysis can reduce the amount of 1,2-epoxybutane used and reduce the generation of impurities, thereby reducing the production cost of hydroxybutyl chitosan and improving its purity.
[0023] (4) Compared with the existing technology of first alkalizing chitosan and then reacting it with 1,2-epoxybutane, this application adopts the "one-pot method" to directly mix chitosan, ethanol, 1,2-epoxybutane and sodium hydroxide to carry out the reaction, which simplifies the preparation method of hydroxybutyl chitosan, reduces the production difficulty, reduces the production time, improves the production efficiency, and is suitable for large-scale industrial production.
[0024] (5) The amount of sodium hydroxide used in this application is significantly reduced, which further reduces the production cost of hydroxybutyl chitosan. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 The thermosensitive effect diagram of hydroxybutyl chitosan provided in the embodiments of this application. Detailed Implementation
[0027] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.
[0028] Unless otherwise specified, all materials and reagents used in the embodiments of this application are commercially available.
[0029] Comparative Example 1
[0030] Hydroxybutyl chitosan was prepared according to the method disclosed in patent application CN102276756A. In Comparative Example 1, 1.0 g of chitosan was dispersed in 10 mL of NaOH solution (50%, w / w) at room temperature, which translates to approximately 7.5 g of sodium hydroxide per 1 g of chitosan. The chitosan in Comparative Example 1 was alkalized for 24 h, then 1,2-epoxybutane was added and the mixture was stirred for another 24 h. The total pretreatment time was 48 h.
[0031] Example 1
[0032] Step (1): Add 40g chitosan, 240g 95% ethanol, 240g 1,2-epoxybutane and 0.8g sodium hydroxide to the reaction flask, and stir and reflux at 60℃-70℃ for 24h.
[0033] Step (2): Cool down to 20℃-30℃, adjust pH to 7-8 with hydrochloric acid, add 400g of hot water at 50-60℃, and after adding, maintain the temperature at 50-60℃ and stir for 30 minutes.
[0034] Step (3): Filter while hot. Wash the filter cake with 200g of hot water at 50-60℃, filter by suction, and discharge.
[0035] Step (4): Dry the product by blowing air at 50℃-60℃ for 12 hours, and then discharge the product to obtain hydroxybutyl chitosan.
[0036] In Example 1, 0.02g of sodium hydroxide was used per 1g of chitosan, which significantly reduced the amount of sodium hydroxide used. The pretreatment time in Example 1 was 24h.
[0037] Comparative Examples 2-4
[0038] The preparation methods of Comparative Examples 2-4 are the same as those of Example 1, except that the reaction medium ethanol in step (1) is replaced. The types of reaction media in step (1) of Comparative Examples 2-4 are adjusted according to Table 2.
[0039] Examples 2-4
[0040] The preparation methods of Examples 2-4 are the same as those of Example 1, except that the concentration of ethanol in the reaction medium in step (1) is different. The concentration of ethanol in step (1) of Examples 2-4 is adjusted according to Table 3.
[0041] Examples 5-8
[0042] The preparation methods of Examples 5-8 are the same as those of Example 1, except that the amount of 95% ethanol used in step (1) is different. The amount of 95% ethanol used in step (1) of Examples 5-8 is adjusted according to Table 4.
[0043] Examples 9-12
[0044] The preparation methods of Examples 9-12 are the same as those of Example 1, except that the amount of 1,2-epoxybutane used in step (1) is different. The amount of 1,2-epoxybutane used in step (1) of Examples 9-12 is adjusted according to Table 5.
[0045] Examples 13-16
[0046] The preparation methods of Examples 13-16 are the same as those of Example 1, except that the amount of sodium hydroxide used in step (1) is different. The amount of sodium hydroxide used in step (1) of Examples 13-16 is adjusted according to Table 6.
[0047] Determination of degree of substitution
[0048] Elemental analysis (Dos, 2009) determines the degree of substitution of chitosan and hydroxybutyl chitosan by measuring the mass percentages of N, C, and H.
[0049] Determination of water solubility
[0050] The solubility range of the sample was determined according to the method described in the pharmacopoeia: hydroxybutyl chitosan solid was ground into a fine powder and dissolved in distilled water at 4°C. The mixture was vigorously shaken for 30 seconds every 5 minutes, and the dissolution was observed over 30 minutes. Complete dissolution was considered complete when no visible solute particles remained.
[0051] Table 1: Physicochemical properties of hydroxybutyl chitosan from Example 1 and Comparative Example 1
[0052]
[0053] As shown in Table 1, the degree of substitution of the hydroxybutyl chitosan prepared in Example 1 is greater than that of the hydroxybutyl chitosan prepared in Comparative Example 1. Both the hydroxybutyl chitosan prepared in Example 1 and Comparative Example 1 are readily soluble in water.
[0054] Given that the hydroxybutyl chitosan prepared in Example 1 and Comparative Example 1 are both readily soluble in water, the preparation method of Example 1 is simpler, reduces production difficulty, shortens production time, and improves production efficiency; the amount of 1,2-epoxybutane used in Example 1 is less, reducing production costs; the amount of sodium hydroxide used in Example 1 is significantly reduced, further reducing production costs.
[0055] Table 2: Effect of reaction medium on the physicochemical properties of hydroxybutyl chitosan
[0056]
[0057] According to Table 2, among the hydroxybutyl chitosans prepared in Example 1 and Comparative Examples 2-4 with 95% ethanol, methanol, isopropanol and water as reaction media, the hydroxybutyl chitosan prepared with 95% ethanol as the reaction medium had the highest degree of substitution.
[0058] Table 3: Effect of ethanol concentration on the physicochemical properties of hydroxybutyl chitosan
[0059]
[0060] As shown in Table 3, among the four ethanol concentrations of 50%, 70%, 95%, and anhydrous ethanol in Examples 1-4, the hydroxybutyl chitosan prepared with 95% ethanol concentration has the highest degree of substitution.
[0061] Table 4: Effect of 95% ethanol dosage on the physicochemical properties of hydroxybutyl chitosan
[0062]
[0063] As shown in Table 4, in Examples 1 and 5-8, within the range of 3 to 12 times the amount of chitosan used (95% ethanol), the degree of substitution of hydroxybutyl chitosan increased with increasing 95% ethanol content. The largest increase in the degree of substitution occurred when the 95% ethanol content increased from 3 to 6 times the amount of chitosan. Conversely, the degree of substitution decreased when the 95% ethanol content increased from 12 to 15 times the amount of chitosan.
[0064] Table 5: Effect of 1,2-epoxybutane dosage on the physicochemical properties of hydroxybutyl chitosan
[0065]
[0066] As shown in Table 5, in Examples 1 and 9-12, within the range of 3 to 15 times the amount of chitosan used (using 1,2-epoxybutane), the degree of substitution of hydroxybutyl chitosan increased with increasing 1,2-epoxybutane usage. The increase in the degree of substitution of hydroxybutyl chitosan was greatest when the amount of 1,2-epoxybutane increased from 3 to 6 times the amount of chitosan.
[0067] Table 6: Effect of sodium hydroxide dosage on the physicochemical properties of hydroxybutyl chitosan
[0068]
[0069] As shown in Table 6, in Examples 1 and 13-16, within the range of sodium hydroxide dosage from 0.01 times to 0.08 times the chitosan dosage, the degree of substitution of hydroxybutyl chitosan increased with the increase of sodium hydroxide dosage. The increase in the degree of substitution of hydroxybutyl chitosan was greatest when the sodium hydroxide dosage increased from 0.01 times to 0.02 times the chitosan dosage.
[0070] Table 7: Elemental Analysis of Hydroxybutyl Chitosan and Chitosan
[0071]
[0072] The degree of substitution of hydroxybutyl chitosan is expressed as the average number of hydroxybutylated groups on each glucosamine or N-acetylglucosamine unit (Blanchard, 1999). The mass percentages of N, C, and H in the hydroxybutyl chitosan and chitosan prepared in Example 1 were determined by elemental analysis to determine the hydroxybutyl content in the product.
[0073] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0074] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.
Claims
1. A method for preparing hydroxybutyl chitosan, characterized in that, Includes the following steps: (1) Add chitosan, ethanol, 1,2-epoxybutane and sodium hydroxide to the reaction flask, wherein the concentration of ethanol is 50%-95%, and stir at 60℃-70℃ for 18h-48h to obtain the first solution; (2) The first solution is cooled to 20℃-30℃, the pH is adjusted to 7-8 with hydrochloric acid, hot water at 50℃-60℃ is added, and the solution is stirred at 50℃-60℃ for 0.2h-1h to obtain a second solution with flocculent matter; (3) Filter the second solution to obtain a filter cake. Wash the filter cake with hot water at 50℃-60℃ and then filter it to obtain the initial product. (4) The initial product is dried in a forced-air dryer at 50℃-60℃ for 8h-24h to obtain hydroxybutyl chitosan.
2. The method for preparing hydroxybutyl chitosan according to claim 1, characterized in that, In step (1), the ratio of ethanol to chitosan is 3g:1g to 15g:1g.
3. The method for preparing hydroxybutyl chitosan according to claim 2, characterized in that, In step (1), the ratio of ethanol to chitosan is 6g:1g.
4. The method for preparing hydroxybutyl chitosan according to claim 3, characterized in that, In step (1), the ratio of 1,2-epoxybutane to chitosan is 3g:1g-15g:1g.
5. The method for preparing hydroxybutyl chitosan according to claim 4, characterized in that, In step (1), the ratio of 1,2-epoxybutane to chitosan is 6g:1g.
6. The method for preparing hydroxybutyl chitosan according to claim 5, characterized in that, In step (1), the ratio of sodium hydroxide to chitosan is 0.01g:1g to 0.08g:1g.
7. The method for preparing hydroxybutyl chitosan according to claim 6, characterized in that, In step (1), the ratio of sodium hydroxide to chitosan is 0.02g:1g.
8. The method for preparing hydroxybutyl chitosan according to any one of claims 1-7, characterized in that, In step (1), the concentration of ethanol is 95%.
9. The method for preparing hydroxybutyl chitosan according to any one of claims 1-7, characterized in that, In step (2), the amount of hot water added is 400g.
10. The method for preparing hydroxybutyl chitosan according to any one of claims 1-7, characterized in that, In step (3), the amount of hot water used is 200g.