Synthesis of substitution-degree-controllable dehydroabietic acid guar gum ester

Abstract

The invention belongs to the technical field of polysaccharide modification, and particularly discloses a preparation method and application of dehydroabietic acid guar gum ester with a controllable substitution degree. The preparation method comprises the following steps: dehydroabietic acid (DA), oxalyl chloride and guar gum (GG) are used as raw materials, dehydroabietic acid acyl chloride (DA-CL) is obtained through acylation reaction, and guar gum ester (DGE) is obtained through esterification reaction. According to the method, the substitution degree of the dehydroabietic acid guar gum ester can be regulated and controlled by adjusting the proportion, temperature and time of the dehydroabietic acid and the guar gum, the product obtained by the method has amphipathy, and the high-substitution product can be dissolved in common organic solvents.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer chemistry and natural polymer preparation, and particularly relates to a method for preparing dehydroabietic acid guar gum ester with controllable substitution degree. Background Art

[0002] Dehydroabietic acid, also known as dehydroabietic acid, is obtained by separating rosin through catalytic disproportionation. The molecular structure of dehydroabietic acid contains aromatic rings and carboxyl functional groups, which are relatively stable and have strong antioxidant properties. It is a substance with good biological activity and has important applications in medicine, industry, agriculture and other fields. For example, in the field of medicine, dehydroabietic acid has antifungal, anti-inflammatory and anticancer activities, and can be used to synthesize a variety of anti-tumor and anti-cancer steroidal drugs and hormone drugs. In addition, dehydroabietic acid and its derivatives can also be used to prepare pesticides, with good bactericidal, insecticidal and herbicidal activities.

[0003] Guar gum (GG), a natural nonionic galactomannan polysaccharide obtained from guar seeds, has recently become a popular choice for new material research in various fields, such as soil treatment, surface chemistry, lithium-ion and zinc-ion batteries, dye-sensitized solar cells, wound dressing and healing, and drug delivery. In addition, the large number of residual hydroxyl functional groups (-OH) on the galactomannan chain provides GG with hydrophilicity and high water solubility.

[0004] Natural polysaccharides and their derivatives have attracted much attention due to their good biocompatibility and biodegradability, providing a rich raw material basis for the research of polysaccharide esters. The important applications of polysaccharide esters in many fields such as inks, coatings, textiles, and plastics determine the necessity of in-depth research on them. Whether in traditional fields such as high-end clothing fibers and cigarette filters, or in emerging fields, polysaccharide esters have huge application potential. Therefore, an in-depth analysis of the research background of polysaccharide esters and further research work on this basis are of vital significance to promote the development of related industries. Summary of the invention

[0005] The purpose of the present invention is to provide a method for synthesizing dehydroabietic acid guar gum ester with controllable substitution degree, which can provide guidance for the substitution degree variation law and synthesis of polysaccharide esters, and can also reduce the use of organic solvents and save production costs.

[0006] The technical solution adopted by the present invention to solve the problem is: a method for synthesizing dehydroabietic acid guar gum ester with controllable substitution degree, wherein the synthesis reaction formula of dehydroabietic acid guar gum ester is:

[0007]

[0008] To achieve the above object, the solution provided by the present invention is as follows:

[0009] A synthesis of dehydroabietic acid guar gum ester with controlled degree of substitution comprises the following steps:

[0010] (1) Refining guar gum: crude guar gum powder is added to water, mechanically stirred at room temperature to prepare it into a viscous liquid, centrifuged to remove the undissolved part, and then anhydrous ethanol is added to precipitate, and then anhydrous ethanol is added while stirring to fully precipitate, and then the precipitate is washed twice with acetone and ether respectively to remove impurities, and finally the sample is freeze-dried and then ground into powder with a grinder;

[0011] (2) Preparation of dehydroabietic acid chloride: Dehydroabietic acid is dissolved in dichloromethane and reacted with oxalyl chloride. The solution is distilled under reduced pressure and then purified with water and a certain concentration of sodium hydroxide solution. Excess water is removed with anhydrous sodium sulfate, and the product is obtained by rotary evaporation after filtration.

[0012] (3) Preparation of dehydroabietic acid guar gum ester: Refined dehydroabietic acid chloride is dissolved in pyridine, and then purified guar gum is added to react under a nitrogen atmosphere and stirred thoroughly. After the reaction, the low-substituted product I (PI) is obtained by centrifugation. A certain proportion of methanol water is used as a precipitant for precipitation, and the high-substituted product II (PII) is obtained by centrifugation. The product I and the product II are dried to obtain the final product.

[0013] According to an embodiment of the present invention, in the step (1), the centrifugation time is 30 min and the rotation speed is 3500 rpm.

[0014] According to an embodiment of the present invention, in step (1), the volume ratio of the guar gum solution to ethanol is 1:1.

[0015] According to an embodiment of the present invention, in the step (2), the amount of dichloromethane used is 5 mL / g.

[0016] According to an embodiment of the present invention, in step (2), the concentration of the sodium hydroxide solution is 0.2 mol / L.

[0017] According to an embodiment of the present invention, in the step (2), the amount of anhydrous sodium sulfate used is 0.1 g / mL.

[0018] According to an embodiment of the present invention, in the step (2), the conditions for reduced pressure distillation are 70° C. for 1.5 h.

[0019] According to an embodiment of the present invention, in the step (3), pyridine is used as both a solvent and a catalyst in an amount of 15 mL.

[0020] According to an embodiment of the present invention, in the step (3), the centrifugation time is 10 min and the rotation speed is 3500 rpm.

[0021] According to an embodiment of the present invention, in the step (3), the drying temperature is 80° C. and the drying time is 12 hours.

[0022] According to an embodiment of the present invention, the reaction temperature is 40°C to 100°C, preferably 100°C.

[0023] According to an embodiment of the present invention, the molar ratio of the acylating agent to the sugar ring repeating unit is 1:1 to 1:6, preferably 1:6.

[0024] According to an embodiment of the present invention, the reaction time is 2 to 12 hours, preferably 12 hours.

[0025] According to an embodiment of the present invention, the degree of substitution of the polysaccharide ester obtained by the preparation method is 0.0027 to 1.5.

[0026] The present invention also provides the polysaccharide ester prepared by the method as described above.

[0027] Beneficial effects of the present invention:

[0028] The preparation method of the present invention can obtain the esterification product quickly and efficiently through heterogeneous reaction. In particular, the cycloalkane acylated polysaccharide which is difficult to synthesize can be synthesized quickly and efficiently. In addition, the product obtained by the method of the present invention has an adjustable degree of substitution and is soluble in common organic solvents. Thanks to the hydrophobicity of guar gum itself and the hydrophobicity of dehydroabietic acid, the esterification product has amphiphilicity and can be applied to many fields, such as drug delivery, tissue engineering, biosensing, water treatment, oil-water separation and waste gas treatment.

[0029] In addition, the method of the present application also improves the problems of large amount of solvents and low yield in the preparation process of polysaccharide esters. The preparation method of the present application has the advantages of simple process, rapidity and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FTIR images of DA-CL and DGE;

[0031] Figure 2 NMR spectra of DA-CL and DGE;

[0032] Figure 3 is the TGA diagram of DGE;

[0033] Figure 4 is the substitution degree diagram of DGE under different conditions; DETAILED DESCRIPTION

[0034] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0035] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0036] In the following embodiments, the relevant detection and characterization are as follows:

[0037] (1) Chemical structure characterization (FT-IR): The structure of the sample was characterized using an infrared spectrometer (Nicolite-6700 Thermo Electron, USA). The sample was prepared by solid sample pressing method. The sample to be tested was placed in a mortar with potassium bromide, ground thoroughly and mixed evenly. A blank sheet was prepared using pure potassium bromide as the test background. The sample to be tested was then pressed into a thin sheet and scanned in the range of 500 to 4000 cm-1.

[0038] (2) Chemical structure characterization (NMR): The hydrogen and carbon spectra of the samples were characterized using a Bruker nuclear magnetic resonance spectrometer (Avance i11 400MHz, Bruker, Germany). The solvent was deuterated chloroform and the standard substance was tetramethylsilane (TMS). The experimental conditions were a spectrum width of 1200 Hz, a pulse tilt angle of 30°, a pulse repetition time of 2 s, and a cumulative number of 16 to 240.

[0039] (3) Chemical structure characterization (TGA): A thermogravimetric analyzer (STA449F3 Netzsch-Geratebau GmbH, Germany) was used to characterize the thermal stability and grafting amount of the sample. The thermal stability of the product was characterized by the weight loss rate (mass %). 10 mg of the substance to be tested was weighed and placed in the AOS field with N2 as the protective gas. The measured temperature was 25-800°C, and the heating rate was 10°C / min.

[0040] Substitution analysis (EA): The C content of the sample was tested using an organic element analyzer (Vario EL cube, USA) in CHNS mode. The sample was completely burned in an oxidation tube at 1150°C in a pure oxygen atmosphere to produce CO2, H2O, and NO. x , SO2, SO3 and other gases, and then the mixed gas is further reduced to CO2, H2O, N2, SO2 and other gases in a reduction tube (850℃, reduced copper), separated by an adsorption-desorption column (Elementar UNICUBE: programmed temperature desorption-TPD), and then separated by a chromatographic column for thermal conductivity detection to obtain the C, H, N, S element content.

[0041] The present invention will be further described below in conjunction with embodiments:

[0042] Example 1

[0043] Purification of guar gum includes the following steps:

[0044] (1) Dissolution: First, add water into a beaker, add the crude guar gum powder under stirring, and mechanically stir at room temperature for 6 hours to completely dissolve it;

[0045] (2) Precipitation: Take an appropriate amount of solution, mix it with ethanol in a ratio of 1:1 and stir it with a glass rod to fully precipitate it, filter to remove the filtrate, and wash the precipitate twice with acetone and ether respectively;

[0046] (3) Drying: Freeze-dry the product at -45°C for 48 h using a freeze dryer and grind it into powder.

[0047] Example 2

[0048] The preparation of dehydroabietic acid chloride comprises the following steps:

[0049] (1) Dissolve 10 g of dehydroabietic acid in 50 mL of dichloromethane, add 6 mL of oxalyl chloride in an ice bath, and react at 30 °C for 5 h;

[0050] (2) After the reaction is completed, the solution is distilled under reduced pressure at 70° C. for 1.5 h, and the tail gas is absorbed with 0.5 mol / L sodium hydroxide solution;

[0051] (3) After distillation under reduced pressure, dissolve the product with 50 mL of dichloromethane, transfer the solution to a 150 mL separatory funnel, add 10 mL of water twice, shake and allow to stand for stratification, then add sodium hydroxide solution, shake and allow to stand for stratification, and collect the lower layer of liquid;

[0052] (4) Add 4 g of anhydrous sodium sulfate to the collected liquid and place it at room temperature away from light for 12 h;

[0053] (5) After filtration, the filtrate was rotary evaporated at 70°C for 1.5 h to obtain the purified acid chloride.

[0054] Example 3

[0055] The preparation of dehydroabietic acid guar gum ester comprises the following steps:

[0056] (1) Dissolve 6.36 g of refined dehydroabietic acid chloride in 15 mL of pyridine, and then add 0.54 g of purified guar gum powder;

[0057] (2) reacting at 100°C for 12 h under nitrogen atmosphere with sufficient stirring;

[0058] (3) After the reaction, the solution was centrifuged at 3500 rpm for 10 min to obtain a low-substituted product I, and then precipitated twice using 75% methanol water as a precipitant, and then centrifuged at 3500 rpm for 10 min to obtain a high-substituted product II.

[0059] The products I and II were dried in an oven at 80°C for 12 h, then ground into powder, wrapped with slow filter paper and placed in a Soxhlet extractor for extraction.

[0060] After extraction, it was dried at 80°C for 12 h to obtain the final product.

[0061] Example 4

[0062] Calculation method of substitution degree:

[0063] Elemental analysis (C, H, O) was performed by VARIO EL III analyzer, and the DS (degree of substitution) value of the acyl chloride group was calculated based on the carbon content as shown below. Among them, DS, M AGU , C%, N, and M represent the degree of substitution of the acyl chloride, the molecular weight of the anhydroglucose unit, the elemental carbon content, the number of carbons in the acyl chloride, and the molecular weight of the acyl chloride substituent, respectively.

[0065] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing dehydroabietic acid guar gum ester with controlled degree of substitution, characterized in that: The specific steps are as follows: (1) Refining guar gum by water extraction and alcohol precipitation; (2) Preparation of dehydroabietic acid chloride: dehydroabietic acid is dissolved in dichloromethane and reacted with oxalyl chloride. The solution is distilled under reduced pressure and then purified with water and a sodium hydroxide solution of a certain concentration. Excess water is removed with anhydrous sodium sulfate, and the product is obtained by filtration and distillation under reduced pressure. (3) Preparation of dehydroabietic acid guar gum ester: Refined dehydroabietic acid chloride is dissolved in pyridine, and then purified guar gum is added to react under a nitrogen atmosphere and stirred sufficiently. After the reaction is completed, the low-substituted product I is obtained by centrifugation. A certain proportion of methanol water is used as a precipitant for precipitation, and the high-substituted product II is obtained by centrifugation. The product I and the product II are extracted and dried to obtain the final product.

2. The preparation method according to claim 1, characterized in that: Dehydroabietic acid should be dissolved in dichloromethane and filtered before reacting with oxalyl chloride to remove impurities.

3. The preparation method according to claim 1, characterized in that: The molar ratio of dehydroabietic acid to oxalyl chloride was 1:1.7, and the reaction conditions were 30°C for 5 h.

4. The preparation method according to claim 1, characterized in that: The specific process of refining dehydroabietic acid chloride is as follows: dissolve dehydroabietic acid chloride in dichloromethane and transfer to a separatory funnel, add water twice respectively, shake and stand to separate layers, then add sodium hydroxide solution, shake and stand to separate layers, collect the lower light yellow liquid and add anhydrous sodium sulfate, place at room temperature, filter and then rotary evaporate the filtrate at 70°C for 1.5h to obtain refined acid chloride.

5. The preparation method according to claim 1, characterized in that: The temperature variable of the reaction of guar gum with dehydroabietic acid chloride is 40-100°C, and the molar ratio and time are 1:6 and 12h, respectively.

6. The preparation method according to claim 1, characterized in that: The molar ratio of guar gum to dehydroabietic acid chloride varied from 1:1 to 1:6, and the temperature and time were 100°C and 12 h, respectively.

7. The preparation method according to claim 1, characterized in that: The time variable of the reaction of guar gum with dehydroabietic acid chloride is 2 to 12 h, and the molar ratio and temperature are 1:6 and 100 °C, respectively.

8. The preparation method according to claim 1, characterized in that: When precipitating product II, the ratio of the precipitant methanol and water is 75% methanol and 25% water.

9. The preparation method according to any one of claims 1 to 10, characterized in that: The substitution degree of the polysaccharide ester obtained by the method is 0.0027-1.

5.

10. The polysaccharide ester prepared by the method according to any one of claims 1 to 11.

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