阅读说明：本技术 新型离子液体单体及其聚合物的制备并应用于分离茶多酚 (Preparation of novel ionic liquid monomer and polymer thereof and application of novel ionic liquid monomer and polymer thereof in separation of tea polyphenol ) 是由 宋航 于 2019-08-30 设计创作，主要内容包括：本发明涉及天然活性成分的分离技术领域,合成了一类新的氨基酸双阳离子型离子液体单体及其聚合物,并用于选择性吸附茶多酚。该类氨基酸离子液体具有更好的生物兼容性,尤其是吸附茶叶提取液中茶多酚的选择性很突出。将该类新型离子液体单体进一步聚合形成一类新的聚合物,该聚合物对于茶多酚的吸附容量显著高于其他吸附介质。将该聚合物用于茶叶提取液,能够选择性地吸附茶多酚(吸附容量可达500mg/g吸附剂),而将其他杂质成分例如咖啡碱等留在提取液中。该方法的应用简化了传统的茶多酚制备工艺；不用有机溶剂及吸附剂能够循环使用,也具有优良的生态环保和安全性。该方法为从茶叶中提取与制备高纯度茶多酚提供了一种高效的新途径。(The invention relates to the technical field of separation of natural active ingredients, synthesizes a novel amino acid dicationic ionic liquid monomer and a polymer thereof, and is used for selectively adsorbing tea polyphenol. The amino acid ionic liquid has better biocompatibility, and particularly has outstanding selectivity for adsorbing tea polyphenol in tea extract. The novel ionic liquid monomer is further polymerized to form a novel polymer, and the adsorption capacity of the polymer on the tea polyphenol is obviously higher than that of other adsorption media. The polymer is used in tea extractive solution, and can selectively adsorb tea polyphenols (adsorption capacity of 500mg/g adsorbent), and retain other impurity components such as caffeine in the extractive solution. The method simplifies the conventional tea polyphenol preparation process; can be recycled without using organic solvents and adsorbents, and has excellent ecological environmental protection and safety. The method provides a new high-efficiency way for extracting and preparing high-purity tea polyphenol from tea leaves.)

1. An amino acid dicationic ionic liquid monomer, which is characterized in that the structural formula is 1

General structural formula 1(n ═ 3-8)

An amino acid dicationic ionic liquid polymer, which is characterized in that the structural formula is 2

The structural formula is general formula 2(n ═ 3-8).

2. A method for preparing the amino acid dicationic ionic liquid monomer according to claim 1, characterized in that: proportional Br (CH)₂)_nBr (CH) was weighed in a molar ratio of 3-8 to 1:2₂)_nBr and N-vinyl imidazole are put into a reactor, acetonitrile is taken as a solvent, and the reaction is carried out for 24 hours under the condition of 82 ℃ circulation reflux by continuous magnetic stirring; after the reaction is finished, the solvent is removed by evaporation, and the mixture is washed for 1-2 times by ethyl acetate and acetone in sequence to obtain (ViIm)₂C_n(Br)₂(ii) a Dissolving with water (ViIm)₂C_n(Br)₂Then, the solution was poured into a charged styrene 201X 7 type strongly basic anion exchange resin to carry out an exchange reaction to obtain (ViIm)₂C_n(OH)₂A solution; equimolar amounts of L-Proline are weighed in (ViIm)₂C_n(OH)₂The solution was stirred at room temperature for 24 hours, and after completion of the neutralization reaction, the product was formed (ViIm)₂C_n(L-Pro)₂Distilling under reduced pressure to remove the solvent to obtain the target product ionic liquid monomer (ViIm)₂C_n(L-Pro)₂。

3. A method for preparing the amino acid dicationic ionic liquid polymer according to claim 1, characterized in that: the monomer (ViIm)₂C_n(L-Pro)₂(n-3-8) to MBA in a molar ratio of 3: 5-15, initiator K₂S₂O₄The dosage of the ionic liquid is 2-12 percent (the addition amount of the initiator/the total mass of the reaction raw materials), the temperature is 30-100 ℃, and the ionic liquid is polymerized in polar solvents (water, methanol and ethanol) in the polymerization process; and (3) after the polymerization is finished, washing the polymer for 2 times by using pure water, and drying the polymer for 48 hours to obtain a light yellow solid ionic liquid polymer.

4. An ionic liquid polymer as claimed in claim 1, for use in selective adsorption of tea polyphenols in a tea extract, wherein: after synthesizing the light yellow solid ionic liquid polymer, grinding and sieving the light yellow solid ionic liquid polymer, and carrying out adsorption separation on the tea polyphenol by using the polymer with 200-350 meshes. The initial concentration of tea polyphenol in the extracting solution is 1g/L-10g/L, the solid-to-liquid ratio of the ionic liquid polymer to the extracting solution is 60:10-50, the temperature is 25-65 ℃, the adsorption time is 150min-450min, and the adsorption capacity can reach 500 mg/g.

5. An ionic liquid polymer as claimed in claim 1 for selective adsorption of tea polyphenols wherein: desorbing the ionic liquid polymer after adsorbing the tea polyphenol, wherein 1-5% of hydrochloric acid methanol solution (V/V) is used as a desorption solvent, the desorption time is 8min, and the desorption rate can reach 93%; the ionic liquid polymer can be reused.

Technical Field

The invention relates to the field of separation of natural active ingredients, in particular to preparation of a novel ionic liquid monomer and a polymer thereof, and application of the ionic liquid monomer and the polymer thereof in separation of tea polyphenol.

Background

The Tea polyphenol TP (Tea Polyphenols, TP) has the highest content in Tea leaves, and accounts for about 15-30% of the dry weight of the Tea leaves. Catechin (Catechinic Acid) is an active ingredient of TP, mainly comprising a series of similar isomers such as ECGC, ECG and EC, etc. TP has wide bioactivity, can be used for preventing cardiovascular diseases, atherosclerosis and arrhythmia, has good effect of reducing blood lipid, and has obvious effect on hyperlipidemia and essential hypertension. Based on the above characteristics, TP is widely used in the fields of medicine, health care, food industry, daily chemicals, adjuvant drug therapy, and the like.

Because the tea polyphenol has complex structure, more active sites, easy inactivation and poor stability, and the chemical total synthesis is difficult to realize in the industrial production, the extraction from the tea is the main way for obtaining the tea polyphenol. The current industrialized method for extracting tea polyphenol is to extract the mixed solution of tea polyphenol and other substances from tea raw materials, and then to remove the other substances by adopting different separation methods and devices with various characteristics, thereby obtaining the high-purity tea polyphenol product.

The other substances in the extract mixture are collectively called impurities, including at least polysaccharides, pectins, celluloses, caffeine and tea polyphenols, and the components are very complicated. In order to remove the impurities, a process flow of using an organic solvent for precipitation and liquid-liquid extraction for multiple times is often adopted in industrial production, the process flow is long, the use amount of the organic solvent is large, the difficulty in controlling the volatilization of the organic solvent and completely recovering organic components in waste liquid is high, and the energy-saving and environment-friendly effects are in urgent need of improvement.

In the development process of further improving the classical or traditional process, when some industrial technologies are used for separating and purifying tea polyphenol by using an organic solvent, the technologies such as an ion precipitation method, a resin adsorption method, membrane separation and the like are combined, so that the use amount of the organic solvent can be reduced, and the traditional process flow can be shortened to a certain extent.

There are still many problems such as the use of heavy metals such as zinc to form precipitates with tea polyphenols and thus separate them from caffeine. Although the tea polyphenol product is of high purity, there is a risk of heavy metals remaining in the product.

Resin adsorption processes use the adsorption characteristics of the resin and a selective eluent to effect separation from other leaching components. For example, a process study of preparing a tea polyphenol fine product by a dungeon et al (dungeon, huying, zhangjianhua. adsorbent resin method [ J ]. food science, 2002,23(11):68-73.) proposed that a chemically synthesized adsorbent resin NKA-2 was used as an adsorbent for tea polyphenol, 80% ethanol, 7 times the mass of tea dust, was used as an extraction solvent, the pH value was 3, the extraction was carried out 2 times at 70-80 ℃, and the extraction rate of the finally obtained product was 13.65%. But the resin adsorption method has the defects of large using amount of column packing, high price, easy inactivation and short service life; the equipment investment and the operation cost of large-scale continuous production are high, and the process uses a plurality of volatile organic solvents, so that the ecological environment-friendly effect is not good enough.

In recent years, several new methods for separating and purifying tea polyphenols have appeared. The study on the adsorption performance of porous starch on tea polyphenol and the oxidation resistance of a compound thereof (tea science, 2015(5): 473-. It can be seen that although the new proposed method uses less organic solvent, has mild separation and adsorption conditions and excellent adsorption selectivity, its very low adsorption capacity (only 25.72mg tea polyphenol/g starch) will result in the need of using very large amount of adsorbent, which makes it difficult to realize industrial application.

If only tea polyphenol can be selectively adsorbed without adsorbing other impurities, the separation and purification process of tea polyphenol is greatly simplified. However, the main problem is that the adsorbent has both excellent selectivity and high adsorption capacity. Despite the extensive research that has been done, no actual breakthrough progress has been seen.

The Ionic Liquid (IL) has low synthesis cost, and meanwhile, compared with the traditional solvent, the Ionic liquid has many other special properties, such as wide liquid range, good thermal stability, strong designability, low vapor pressure, low volatility, good conductivity, good recycling performance and the like, is used for extraction, adsorption, catalysts and other processes, and shows good application value. Recent studies have found that when part of the ionic liquid structure has dication, the properties or performance may change significantly. However, the rules and mechanism of the changes are still clear.

Polyionic liquids combine some properties of ionic liquids and polymers, and have many excellent characteristics, such as excellent mechanical stability, ionic conductivity, processability, durability, chemical compatibility and controllability, and the like. In recent years, polyionic liquids have attracted much attention in the fields of materials, separation and purification, electrochemistry, catalysts and the like due to the special structure and properties of polyionic liquids. In the field of food and drug application of ionic liquid, the safety of the ionic liquid is extremely important. A large number of researches show that the imidazole ionic liquid has good safety, and particularly some recent ionic liquids of natural amino acids have the characteristics of good biocompatibility, no toxicity and the like, and have better safety. For example, Shunhun et al developed a highly efficient and selective method for extracting and separating tea polyphenols and caffeine from tea leaves (patent application: preparation and application of immobilized ionic liquid of tentacle amino acid type 2018). Firstly, 1-alkyl-3-methylimidazole ferric chloride ionic liquids with different carbon chain lengths are synthesized: MIMFeCl₄、C₂MIMFeCl₄、C₃MIMFeCl₄、C₄MIMFeCl₄、C₅MIMFeCl₄(ii) a And complexing the magnetic ionic liquid and the tea polyphenol to form a precipitate with low solubility by using the aqueous solution of the caffeine in the condition that the pH value of the aqueous solution is 5-6, and keeping the caffeine in a liquid phase to separate the tea polyphenol from the caffeine by filtering. Actually, the precipitate of the magnetic ionic liquid and the tea polyphenol needs to be dissolved again by acid water, then is extracted by ethyl acetate, and is evaporated under reduced pressure to remove the ethyl acetate, and finally the purified tea polyphenol can be obtained. The adsorption capacity can reach 162mg tea polyphenol/g adsorbent (precipitator) under the optimal condition, the performance of selectively adsorbing tea polyphenol is excellent, and the adsorption capacity is greatly improvedHigh. However, after the tea polyphenol and the caffeine are separated, the theophylline in the liquid phase needs to be separated, carbonyl iron powder CIP is added to be preferentially combined with the magnetic ionic liquid to generate a complex which is insoluble in water and most solvents, a filter cake after filtration is the CIP-MIL complex, the main bioactive component in the filtrate is the caffeine, the magnetic ionic liquid can be dissolved in water after the CIP-MIL complex is suspended by water, the CIP forms solid precipitates to be separated from a solution system, and therefore the ionic liquid and the CIP can be repeatedly used.

Compared with the prior art, the invention has the following advantages:

a novel dicationic ionic liquid based on imidazole parent nucleus and taking natural amino acid as cation is synthesized, and further forms an ionic liquid copolymer (hereinafter referred to as polymer) with N, N' -Methylene Bisacrylamide (MBA) cross-linking agent, and the polymer is presented as a gel-state aggregate in water. Therefore, on one hand, the advantage that the novel ionic liquid has obvious specificity and selectivity on tea polyphenol can be exerted, and on the other hand, the characteristic that the gel aggregate can obviously improve the adsorption capacity is also utilized.

Through the research of years, particularly the research of structural design and synthesis of ionic liquid, polymerization optimization of aggregates and the like, the novel adsorbent which has good biocompatibility and outstanding selectivity to tea polyphenol, particularly has adsorption capacity as high as 500mg of tea polyphenol/g of adsorbent, breaks through the long-term technical bottleneck, almost does not use organic solvent in the whole process, has outstanding ecological environment-friendly effect, obviously simplifies the process flow, obviously reduces the equipment and operation cost, and has good economy.

The beneficial effects of the project

(1) A new imidazole amino acid dicationic ionic liquid is designed and synthesized, and the ionic liquid has good biocompatibility and better selectivity.

(2) The dicationic ionic liquid and MBA are polymerized into a novel ionic liquid polymer, and the polymer has the adsorption selectivity of the ionic liquid to tea polyphenol and the excellent adsorption capacity of the polymer.

(3) By utilizing the polymer, a new method for high-efficiency selective adsorption separation of tea polyphenol is established. By using the polyion liquid to directionally adsorb the tea polyphenol, a series of complicated process routes such as complicated experimental steps, use and recovery of a large amount of organic solvent, removal of impurities and the like in the traditional process for separating and purifying the tea polyphenol are solved, so that the tea polyphenol is more efficiently and conveniently separated and purified, and the ionic liquid is convenient to recycle.

Drawings

To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are required to be used in the embodiments will be briefly described below, and it should be understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope.

FIG. 1 a1 ViImC_nSynthetic route to L-Pro monocationic ionic liquids (n ═ 3,4,5,6) a2(ViIm)₂C_n(L-Pro)₂Synthetic route of dicationic ionic liquids (n ═ 3,4,5, 6).

FIG. 2A 1 imidazole ionic liquid copolymer A2 imidazole ionic liquid polymer synthesis route.

FIG. 3 is a nuclear magnetic hydrogen spectrum of a polymerized monomer of a dicationic ionic liquid, [ ViIm]₂C₃[L-pro]₂:¹H NMR(400MHz,D₂O)δ7.79(d,2H),7.59(d,2H),7.13-7.09(m,2H),5.79-5.76(m,2H),5.42-5.40(m,2H),4.37-4.34(m,4H),3.93-3.90(m,2H),3.29-3.27(m,2H),3.15-3.13(m,2H),2.56-2.53(m,2H),2.25-2.23(m,2H),2.22-1.88(m,6H).

FIG. 4 is a nuclear magnetic hydrogen spectrum of a polymerized monomer of a dicationic ionic liquid, [ ViIm]₂C₄[L-pro]₂:¹H NMR(400MHz,D₂O)δ7.75(d,2H),7.56(d,2H),7.14-7.08(m,2H),5.79-5.75(m,2H),5.41-5.38(m,2H),4.24-4.20(m,4H),3.95-3.90(m,2H),3.29-3.27(m,2H),3.18-3.15(m,2H),2.28-2.26(m,2H),1.93-1.90(m,4H),1.32-1.27(m,4H),0.92-0.88(m,2H).

FIG. 5 is a nuclear magnetic hydrogen spectrum of a polymerized monomer of a dicationic ionic liquid, [ ViIm]₂C₅[L-pro]₂:¹H NMR(400MHz,D₂O)δ7.75(d,2H),7.55(d,2H),7.14-7.08(m,2H),5.79-5.75(m,2H),5.41-5.38(m,2H),4.24-4.19(m,4H),4.03-4.00(m,2H),3.33-3.32(m,2H),3.27-3.22(m,2H),2.29-2.26(m,2H),1.97-1.90(m,8H),1.32-1.27(m,4H),0.92-0.88(m,2H).

FIG. 6 is a nuclear magnetic hydrogen spectrum of a polymerized monomer of a dicationic ionic liquid, [ ViIm]₂C₆[L-pro]₂:¹H NMR(400MHz,D₂O)δ7.74(d,2H),7.55(d,2H),7.14-7.07(m,2H),5.79-5.74(m,2H),5.40-5.37(m,2H),4.22-4.19(m,4H),3.99-3.96(m,2H),3.23-3.20(m,2H),320-3.19(m,2H),2.28-2.25(m,2H),1.96-1.93(m,8H),1.28-1.23(m,8H),0.82-0.80(m,2H).

FIG. 7 shows IL (ViImC) provided by the present invention₃-L-Pro), MBA-only polymer (Pol 0) and ionic liquid polymer ViImC₃IR spectrum of-L-Pro (pol c), characteristic peaks for MBA polymerization which are 1651cm^-11528cm, flexural vibration absorption peak at C ═ O^-1A strong absorption peak of bending vibration at N-H (characteristic of the N-H trans conformation). Similarly, the corresponding absorption peak can be found at the corresponding position in the ionic liquid polymer, which indicates that the MBA component participates in the formation of the polymer. Comparing the infrared patterns of MBA polymerization and ionic liquid polymer, the ionic liquid polymer was found to be 3429cm^-1The absorption peak is obviously enhanced because the water absorption of the amino acid ionic liquid is particularly strong, so that the water absorption peak of the ionic liquid polymer is strong, and the ionic liquid polymer is observed at 1385cm^-1、1225cm^-1、1176cm^-1And 760cm^-1The absorption peak at (A) is also significantly enhanced due to the addition of the IL component. The largest difference in the infrared spectra of the ionic liquid polymer and MBA polymerization was at 1459cm^-1A new peak appeared at 1459cm^-1Is the absorption peak of the imidazole ring in IL. From the spectral signature above, it was initially demonstrated that IL participates in the polymerization reaction to form a co-polymer.

FIG. 8 shows that for further analysis of the surface structure of the polymer material according to the invention, Pol 0 (MBA polymer only) and Pol c (ionic liquid ViImC) were observed by scanning electron microscopy₃-L-Pro Polymer) Material TableMorphological characteristics of the faces. The electron microscope results show that the surfaces of the two polymers are rough, the materials are more brittle after the ionic liquid is added, and the milled section is smooth.

FIG. 9 Pol c (ionic liquid ViImC) according to the invention₃-L-Pro polymer) ionic liquid polymer, sieving the ground ionic liquid polymer to obtain 200-350 mesh polymer, and analyzing the particle size of the polymer, wherein the average particle size is about 50 mu m.

FIG. 10 shows an ionic liquid according to the invention (ViImC)₆L-Pro) adsorption results of the polymer material on the tea polyphenol, and SEM characterization is carried out before and after the polymer adsorbs the tea polyphenol and after the tea polyphenol is eluted.

FIG. 11 shows that the selective adsorption effect of the adsorbent on tea polyphenols and caffeine is examined in order to verify the selective adsorption effect of the ionic liquid polymer adsorbent. FIG. 11(a) is an HPLC chart of each component in a crude sample of tea polyphenol wherein each component is determined by the HPLC peak time of its standard, indicating that the main component of tea polyphenol is EGCG; FIG. 11(b) shows the residual components in the adsorbed tea polyphenol sample, in which the main component EGCG and the minor component ECG in the original sample almost disappear, while the other components are basically remained in the sample liquid, indicating that the selective adsorption of the tea polyphenol main component EGCG and ECG is prominent. Fig. 11(c) shows the actual green tea extract sample, in which the active ingredients including tea polyphenols (EGC, EGCG and EC) and caffeine (caffeine) to be removed are mainly contained. FIG. 11(d) shows the results of the adsorption of the green tea extract with the polymer of the present invention, in which the active ingredients of tea polyphenols (EGC and EGCG) are hardly contained in the extract, but caffeine is substantially retained, and it can be seen that the effect of selectively adsorbing tea polyphenols to remove caffeine is excellent.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The following is a specific description of the preparation of the ionic liquid monomer and the polymer thereof provided by the embodiments of the present invention and the method for adsorbing tea polyphenol.