Wild jujube pulp polyphenol extraction process based on deep eutectic solvent

Abstract

The invention provides a wild jujube pulp polyphenol extraction process based on a deep eutectic solvent. The deep eutectic solvent (DES) technology is adopted to optimize the extraction process of the wild jujube pulp polyphenol, and the antioxidant activity of the extracted wild jujube pulp polyphenol is evaluated. According to the method, five different eutectic solvents are prepared and screened, and choline chloride / levulinic acid (ChCl / LA) is determined as the optimal solvent of wild jujube pulp polyphenol. Through single factor and orthogonal experiment optimization, the optimal extraction conditions of the wild jujube pulp polyphenol are determined as follows: the water content is 10%, the extraction time is 40 min, the extraction temperature is 60 DEG C, the material-liquid ratio is 1: 30 g / mL, and the polyphenol yield can reach 10.5 mg / g and is increased by 1.6 times compared with that before optimization. The method provides a technical path for green and efficient extraction and high-valued utilization of wild jujube pulp polyphenol, and provides reference for deep application of DES in plant resources.

Description

Technical Field

[0001] The invention belongs to the technical field of plant extraction, and in particular relates to a process for extracting polyphenols from jujube pulp based on a low eutectic solvent. Background Art

[0002] Saline-alkali land is a special type of soil whose high salinity and alkalinity significantly impact plant growth and quality. To better develop saline-alkali land as a reserve resource, tapping the potential of saline-alkali land crops is particularly important. The skin, pulp, and kernel of the fruit all have medicinal value. The pulp, in particular, is rich in polyphenols, which, when consumed, can strengthen the spleen and stomach, nourish the heart and calm the mind, and have various benefits, including sedative, hypnotic, antioxidant, and antidepressant properties. [1-3] At present, the development of sour jujube kernel is relatively mature and its value is relatively higher. However, this leads to the low utilization rate of its by-product, sour jujube pulp.

[0003] The jujube kernels are obtained by processing them in a non-standard way, which causes a large amount of pulp to rot and deteriorate due to its high water content, resulting in 30-40% of the jujube pulp being discarded every year. [4-5] , which not only causes waste of resources, but also pollutes the environment.

[0004] Studies have found that polyphenols have significant antioxidant properties. [6] , anti-inflammatory [7] , antibacterial [4] , anti-cancer [3] The extraction efficiency and quality of polyphenols, the main active ingredients in jujube pulp, directly affect the comprehensive utilization and development of jujube. However, the current traditional polyphenol extraction methods (such as organic solvent extraction) have problems such as low extraction efficiency, solvent residues and environmental pollution, which are difficult to meet the requirements of green chemistry and sustainable development. [8] Therefore, developing an efficient, environmentally friendly and green extraction technology has become an important direction for improving the high value utilization of sour jujube pulp. [9] .

[0005] Deep eutectic solvent (DES) is a new type of green solvent. It has gradually become a research hotspot in the field of plant polyphenol extraction due to its low toxicity, biodegradability, low cost and high solubility. [10-11] Through the interaction between hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA), DES can form an effective dissolution system, which is particularly suitable for the extraction of various bioactive substances, especially polyphenols, and provides a new method for the efficient extraction of polyphenols from jujube pulp.

[12] However, the application of DES in the extraction of polyphenols from jujube pulp is relatively rare and is still in its infancy. There are still research gaps in solvent selection, extraction process optimization, antioxidant activity, and its interaction with polyphenols. [13-15] In addition, existing research mainly focuses on the screening of single solvents, but lacks systematic optimization of key process parameters (such as water content, temperature, time, etc.) during the DES extraction process, which seriously limits the practical application of DES in extracting polyphenols. [16-19] . Summary of the Invention

[0006] The present invention aims to provide a process for extracting polyphenols from jujube pulp based on a deep eutectic solvent.

[0007] In order to achieve the purpose of the present invention, in the first aspect, the present invention provides a process for extracting polyphenols from jujube pulp based on a low eutectic solvent, wherein the jujube pulp is dried at a low temperature (such as 55°C) and crushed to obtain jujube pulp powder; the jujube pulp powder is mixed with a low eutectic solvent and extracted at a certain temperature, and the obtained extract contains polyphenol compounds.

[0008] Preferably, the deep eutectic solvent is a choline chloride-levulinic acid deep eutectic solvent.

[0009] More preferably, the molar mass ratio of choline chloride to levulinic acid in the deep eutectic solvent is 1:1.2.

[0010] More preferably, the water content of the deep eutectic solvent is 10%.

[0011] More preferably, the solid-liquid ratio of the sour jujube pulp powder to the low eutectic solvent is 1 g:30 mL.

[0012] Preferably, the extraction temperature is 60°C and the extraction time is 40 minutes.

[0013] Furthermore, the sour jujube pulp is dried at low temperature, crushed and passed through an 80-mesh sieve to obtain sour jujube pulp powder.

[0014] In a second aspect, the present invention provides jujube pulp polyphenols extracted according to the process.

[0015] In a third aspect, the present invention provides the use of the sour jujube pulp polyphenols in the preparation of antioxidants.

[0016] In a fourth aspect, the present invention provides the application of the sour jujube pulp polyphenols in the field of food and health care products.

[0017] By means of the above technical solution, the present invention has at least the following advantages and beneficial effects:

[0018] The present invention uses the pulp of jujube as the research object. First, five DESs were prepared, and the extraction rate of polyphenols in jujube pulp was used as the evaluation index. The effects of factors such as water content, material-liquid ratio, extraction time, and extraction temperature on the extraction rate of polyphenols in jujube pulp were optimized through single-factor and orthogonal experiments, and the optimal extraction process for jujube pulp polyphenols was finally determined. At the same time, the microstructural changes of jujube pulp before and after DES extraction were observed by scanning electron microscopy, revealing the mechanism of interaction between DES and polyphenols. In addition, antioxidant activity was measured to determine whether the extracted jujube pulp polyphenols have application potential in the food and medical fields. These research findings provide a technical path for the green and efficient extraction and high-value utilization of jujube pulp polyphenols, and also provide a reference for the in-depth application of DES in plant resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a polyphenol standard curve in a preferred embodiment of the present invention.

[0020] Figure 2 Fourier transform infrared spectroscopic analysis of preferred embodiments of the present invention. (a) DES-1, urea, and Chlorhexidine dichloride; (b) DES-2, levulinic acid, and Chlorhexidine dichloride; (c) DES-3, ethylene glycol, and Chlorhexidine dichloride; (d) DES-4, glycerol, and Chlorhexidine dichloride; and (e) DES-5, lactic acid, and Chlorhexidine dichloride.

[0021] Figure 3 This is the effect of different extraction solvents on the extraction rate of polyphenols from sour jujube pulp in a preferred embodiment of the present invention.

[0022] Figure 4 Figure 2 shows the effects of different factors on the yield of polyphenols from jujube pulp in a preferred embodiment of the present invention: (a) extraction temperature, (b) DES water content, (c) extraction time, and (d) solid-liquid ratio.

[0023] Figure 5 These are scanning electron micrographs of the original jujube pulp powder (A, D), the jujube pulp powder after 70% ethanol extraction (B, E), and the jujube pulp powder after DES extraction (C, F) in a preferred embodiment of the present invention (A, B and C are 50X, D, E and F are 300X).

[0024] Figure 6 This is the DPPH radical scavenging activity of the jujube pulp polyphenols in a preferred embodiment of the present invention.

[0025] Figure 7 ABTS of jujube pulp polyphenols in a preferred embodiment of the present invention + Free radical scavenging activity.

[0026] Figure 8 It is the total reducing capacity of the polyphenols in the pulp of the sour jujube in the preferred embodiment of the present invention. DETAILED DESCRIPTION

[0027] Due to the stress of the growing environment, saline-alkali land jujube is rich in active substances such as polyphenols and flavonoids, and is widely used in functional foods and active ingredient extraction. However, compared with jujube kernels, the extraction and utilization of polyphenols in jujube pulp has not been fully developed and has great potential. The present invention uses deep eutectic solvent (DES) technology to optimize the extraction process of jujube pulp polyphenols and evaluate the antioxidant activity of the extracted jujube pulp polyphenols. We prepared 5 different deep eutectic solvents and screened them, and determined that choline chloride / levulinic acid (ChCl / LA) was the best solvent for jujube pulp polyphenols. After single-factor and orthogonal experimental optimization, the optimal extraction conditions for jujube pulp polyphenols were determined: water content of 10%, extraction time of 40min, extraction temperature of 60℃, and solid-liquid ratio of 1:30g / mL. The polyphenol yield can reach 10.5mg / g, which is 1.6 times higher than before optimization. Scanning electron microscopy (SEM) results showed that the surface pores of the residue after extraction with a low eutectic solvent were more abundant. Subsequently, the spike recovery experiment verified that the data could truly reflect the content of the target substance in the sample. The antioxidant experiment showed that the DPPH and ABTS of the jujube pulp polyphenols at 0.04 mg / mL and 0.07 mg / mL were significantly higher than those of the zizyphus jujuba pulp polyphenols. + The free radical scavenging rate is better than that of ascorbic acid (VC) at the same concentration. And the reducing power increases with the increase of concentration. 50 The present invention provides a new idea for the high efficiency and sustainable development of DES in the extraction of plant polyphenols.

[0028] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

[0029] Example 1 Optimization of the extraction process of polyphenols from jujube pulp based on deep eutectic solvent and study of their antioxidant activity

[0030] 1 Materials and Methods

[0031] 1.1 Experimental Materials and Reagents

[0032] Jujube was provided by Dongying Guangyuan Biotechnology Co., Ltd., Dongying City, Shandong Province; gallic acid standard (purity 99%) was provided by Hefei Bomei Biotechnology Co., Ltd.; Folin phenol reagent and total antioxidant capacity (T-AOC) kit (FRAP method) were provided by Beijing Solaibao Technology Co., Ltd.; choline chloride, urea, levulinic acid, ethylene glycol, glycerol, lactic acid, anhydrous sodium carbonate, potassium persulfate, and anhydrous ethanol were purchased from Shanghai MacLean Biochemical Technology Co., Ltd. and were all analytical grade; 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) reagent and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) were all standards with a purity of 99.9%; deionized water was used.

[0033] 1.2 Experimental instruments

[0034] FW-135 high-speed pulverizer (Tianjin Test Instrument Co., Ltd.), Spectra MAX190 multifunctional microplate reader (Beijing Kedeyuanyang Technology Co., Ltd.), DK-8 constant temperature water bath (Shanghai Yiheng Technology Co., Ltd.), 84-1 magnetic stirrer (Shanghai Meiyingpu Instrument Manufacturing Co., Ltd.), TENSOR 27 Fourier transform near-infrared spectrometer (Bruker Technology Co., Ltd., Germany), SCIENTZ-18N vacuum freeze dryer (Ningbo Xinzhi Biotechnology Co., Ltd.), SU8010 cold field emission scanning electron microscope (HITACH Co., Ltd., Japan), 2-6 refrigerated centrifuge (Merck Sigma-Aldrich Trading Co., Ltd., Germany), HEAL DORCE NW ultrapure water system (Hong Kong Likang Biomedical Technology Holding Group Co., Ltd., China).

[0035] 1.2 Experimental methods

[0036] 1.2.1 Pretreatment of sour jujube

[0037] After preliminary screening to remove bad and inferior jujube pulp, it is washed with clean water to remove surface impurities, the pulp is separated from the core, and the pulp portion is retained; the pulp is placed in a forced air drying oven and dried at 55°C to remove excess moisture in the pulp; the dried jujube pulp is crushed with a high-speed grinder and passed through an 80-mesh sieve; the obtained jujube pulp powder is sealed and placed in a desiccator, and stored dry at room temperature away from light for later use.

[0038] 1.2.2DES preparation and characterization

[0039] The DES preparation method for extracting polyphenols from jujube pulp refers to the method of Li

[20] When preparing DES, various types of low eutectic solvents are synthesized by HBD and HBA.

[21] As shown in Table 1, choline chloride (ChCl) was used as a hydrogen bond acceptor, and urea, levulinic acid, ethylene glycol, glycerol, and lactic acid were used as hydrogen bond donors, respectively, in a 1:1.2 molar mass ratio. The mixture was heated and stirred at 90°C until a uniform, transparent, and stable liquid was formed. These mixtures were labeled DES-1, DES-2, DES-3, DES-4, and DES-5, respectively. The eutectic mixture was then cooled to room temperature, sealed, and stored for later use. A certain amount of water was added to adjust the viscosity of DES.

[14]

[22] In order to verify the structural characteristics of DES, the synthesized DES system and its components were characterized and analyzed using Fourier transform infrared spectroscopy.

[23] -

[24] .

[0040] Table 1 Preparation of ChCl-based DES

[0041]

[0042] 1.2.3DES Screening

[0043] The DES system prepared according to Section 1.2.2 was used to extract polyphenols from the jujube pulp; the extraction rate was used as an indicator to screen the best DES for subsequent experiments. The specific operation method is as follows: accurately weigh 1.0g of jujube pulp powder and place it in a 50mL centrifuge tube, add 16mL of DES and 4mL of deionized water respectively, and extract at a constant temperature of 50°C for 40min. After the extraction, the crude liquid was centrifuged at 8000rpm for 10min, filtered, and the supernatant was collected to determine the polyphenol extraction rate. In order to evaluate the DES extraction effect, the extraction solvent 70% (v / v) ethanol solution was set as a control, and parallel experiments were carried out using the same operating conditions. Each group of experiments was repeated 3 times.

[25] .

[0044] 1.2.4 Drawing of polyphenol standard curve and yield calculation

[0045] The polyphenol content was determined by the Folin-Ciocalteu method. [9]Tan Tianyu et al. improved the method by accurately weighing 5.0 mg of gallic acid standard, dissolving it in deionized water and saturating it to 25 mL to prepare a stock solution of gallic acid standard with a concentration of 0.20 mg / mL. Accurately pipette 0 μL, 250 μL, 1250 μL, 2500 μL, 3750 μL, and 5000 μL of the stock solution into a 5.0 mL volumetric flask and dilute to volume to obtain a series of standard solutions with concentrations of 0.00, 0.01, 0.05, 0.10, 0.15, and 0.20 mg / mL, respectively. Take 0.1 mL of each standard solution, add 0.3 mL of 10% Folin phenol reagent in turn, vortex mix, add 0.6 mL of 12% (w / v) Na2CO3 solution, and dilute to 5.0 mL. After reacting at room temperature in the dark for 1 hour, measure the absorbance at 765 nm, and use gallic acid concentration as the horizontal axis and absorbance value as the vertical axis to draw a standard curve ( Figure 1 ). The regression equation y=2.1457x+0.0841 and the correlation coefficient R 2 =0.9992.

[0046] The jujube pulp extract was centrifuged at 8000 rpm for 10 min, the supernatant was collected and transferred to a centrifuge tube, 1.0 mL of the supernatant was pipetted, 0.3 mL of 10% Folin phenol reagent was added, and vortexed for 3 min to allow it to react fully, followed by 0.6 mL of 12% (w / v) Na2CO3 solution was added, mixed, and the volume was made up to 5.0 mL with deionized water, and the reaction was allowed to stand in the dark for 1 h, and the absorbance was measured at 765 nm.

[26] The polyphenol yield (W) is calculated according to the following formula:

[0047] W=(c×v×n) / m

[0048] Where:

[0049] W——yield of polyphenols from jujube pulp, mg / g;

[0050] c——polyphenol mass concentration, mg / mL;

[0051] v——fixed volume, mL;

[0052] n——dilution multiple;

[0053] m——sample mass, g.

[0054] 1.2.5 Single-factor experiment

[0055] Jujube pulp powder was used as raw material, and DES-2 was used as the extraction solvent. The extraction time, extraction temperature, water content, and feed liquid were adjusted as variable factors to extract jujube pulp polyphenols. The extract was centrifuged at 8000 rpm for 10 min, and 1.0 mL of the supernatant was collected. The polyphenol yield was calculated according to the method in 1.2.4

[27] .

[0056] (1) Effect of different extraction times on polyphenol extraction rate

[0057] A single-factor experimental design was performed using DES-2 as the extraction solvent, a fixed solid-liquid ratio of 1:20 g / mL, a fixed water content of the extraction solvent (low eutectic solvent) of 20%, and an extraction temperature of 50°C. The extraction time was set as 10 min, 20 min, 30 min, 40 min, and 50 min as variables for polyphenol extraction from jujube pulp. After the extraction, the mixture was centrifuged at 8000 rpm for 10 min, 1.0 mL of the supernatant was aspirated, and the polyphenol yield was calculated according to method 1.2.4.

[0058] (2) Effect of different extraction temperatures on polyphenol extraction rate

[0059] Use DES-2 as the extraction solvent, fix the solid-liquid ratio at 1:20 g / mL, the water content of the extraction solvent at 20%, and the extraction time at 40 min. Set the extraction temperatures at 30°C, 40°C, 50°C, 60°C, and 70°C as variables to extract polyphenols from jujube pulp. After the extraction, centrifuge at 8000 rpm for 10 min, aspirate 1.0 mL of the supernatant, and calculate the polyphenol yield according to method 1.2.4.

[0060] (3) Effect of different water contents of extraction solvent on polyphenol extraction rate

[0061] Use DES-2 as the extraction solvent, fix the solid-liquid ratio at 1:20 g / mL, the extraction time at 40 min, the extraction temperature at 50°C, and set the water content of the extraction solvent to 10%, 20%, 30%, 40% and 50% as variables to extract polyphenols from jujube pulp. After the extraction, centrifuge at 8000 rpm for 10 min, aspirate 1.0 mL of the supernatant, and calculate the polyphenol yield according to method 1.2.4.

[0062] (4) Effect of different solid-liquid ratios on polyphenol extraction rate

[0063] Using DES-2 as the extraction solvent, the fixed water content was 20%, the extraction time was 40 min, the extraction temperature was 50℃, and the solid-liquid ratio was set as 1:10 g / mL, 1:20 g / mL, 1:30 g / mL, 1:40 g / mL and 1:50 g / mL as variables for the extraction of polyphenols from jujube pulp. After the extraction, centrifuge at 8000 rpm for 10 min, and draw 1.0 mL of the supernatant. The polyphenol yield was calculated according to the method in 1.2.4.

[0064] 1.2.7 Orthogonal Experimental Design

[0065] Accurately weigh 0.5g of jujube pulp powder in a 15mL centrifuge tube. Based on the results of the single factor experiment, L9(34 An orthogonal experimental design was used to optimize the extraction process. Polyphenol yield was used as the evaluation metric. Four key factors (water content, extraction time, extraction temperature, and solid-liquid ratio) were evaluated, with three levels for each factor (Table 2). Three replicates were performed for each combination, and the results were averaged. IBM SPSS Statistics 26 statistical software was used to analyze the relationships between water content, extraction time, extraction temperature, solid-liquid ratio, and polyphenol extraction yield to determine the optimal extraction process parameters.

[0066] Table 2 Orthogonal test factor level table

[0067] level Water content (%) Extraction time (min) Extraction temperature (℃) Solid-liquid ratio (g / mL) 1 10 30 50 1:10 2 20 40 60 1:20 3 30 50 70 1:30

[0068] 1.2.8 Microstructure of Jujube Fruit

[0069] The effects of different extraction solvents on the microstructure of jujube pulp were investigated. DES-2 and 70% ethanol were used as extraction solvents, respectively. Polyphenols were extracted according to the optimized extraction process. The residues after extraction were collected and dried at low temperature. Jujube pulp powder samples before and after extraction were prepared. The samples were dispersed and fixed on the test copper plate. The surface morphology of the samples was observed by scanning electron microscopy (SEM), and the microstructural changes of the samples were compared and analyzed.

[28] .

[0070] 1.2.9 Spike recovery experiment

[0071] The accuracy of the assay method is assessed by measuring spike recovery. This involves adding a quantitative amount of standard substance to a sample matrix containing a known analyte, analyzing the sample according to the sample preparation steps, and then calculating the ratio of the resulting value to the theoretical value. Specifically, accurately weigh 1.0 mL of a sample with a known polyphenol concentration and add 1.0 mg of gallic acid standard to each sample. Determine the polyphenol content according to the assay method described in 1.2.4. Repeat the assay five times for each sample. Calculate the recovery, P, using the following formula.

[0072] C1=m1÷V1

[0073] C2=m2÷V2

[0074]

[0075] Where:

[0076] P——spike recovery, %;

[0077] C1——measured sample concentration, mg / mL;

[0078] m1——substance content in the sample, mg / g;

[0079] V2——sample volume, mL;

[0080] C2——measured concentration of spiked sample, mg / mL;

[0081] m2——the content of the substance in the spiked sample, mg / g;

[0082] V2——volume of spiked sample, mL;

[0083] C3——Standard amount, mg.

[0084] 1.2.10 DPPH free radical scavenging ability determination

[0085] The polyphenol extract of jujube pulp was diluted to prepare 2 mL of jujube pulp polyphenol extract with concentrations of 0.04 mg / mL, 0.07 mg / mL, 0.15 mg / mL, 0.30 mg / mL, 0.60 mg / mL, 0.70 mg / mL, 0.80 mg / mL, and 1.00 mg / mL, respectively. 2 mL of 0.1 mmol / L DPPH ethanol solution was added to each of the solutions and mixed thoroughly. At the same time, a blank group (with anhydrous ethanol instead of the sample solution), a background group (with anhydrous ethanol instead of the DPPH solution), and a positive control group (with ascorbic acid (VC) instead of the sample solution) were set up. The solution was reacted in the dark for 30 minutes, and the absorbance was measured at 517 nm.

[0086]

[0087] Where:

[0088] A1, absorbance of polyphenols in jujube pulp;

[0089] A2, absorbance of background group solution;

[0090] A0 is the absorbance of the blank group.

[0091] 1.2.11ABTS + Free radical scavenging rate assay

[0092] The polyphenol extract from the fruit pulp of the Chinese jujube was diluted to prepare 1 mL of each of the following concentrations: 0.04 mg / mL, 0.07 mg / mL, 0.15 mg / mL, 0.30 mg / mL, 0.60 mg / mL, 0.70 mg / mL, 0.80 mg / mL, and 1.00 mg / mL. The ABTS working solution was prepared by mixing 7 mM ABTS solution and 2.45 mM K₂S₂O₂ in equal proportions. The mixture was incubated in the dark for 12–16 h before use. The solution was diluted with anhydrous ethanol to an absorbance of 0.7 ± 0.02 at 734 nm. Ten μL of the sample solution was added to 1 mL of the ABTS working solution as the reaction group. A blank control (using anhydrous ethanol instead of the sample solution), a background control (using anhydrous ethanol instead of the ABTS working solution), and a positive control (using VC instead of the sample solution) were also prepared. The reaction was incubated in the dark for 10 min, and the absorbance was measured at 734 nm.

[0093]

[0094] Where:

[0095] A1, absorbance of polyphenols in jujube pulp;

[0096] A2, absorbance of background group solution;

[0097] A0 is the absorbance of the blank group.

[0098] 1.2.12 Determination of total reducing power

[0099] The jujube pulp polyphenol extract was diluted to prepare jujube pulp polyphenol extracts with concentrations of 0.04 mg / mL, 0.07 mg / mL, 0.15 mg / mL, 0.30 mg / mL, 0.60 mg / mL, 0.70 mg / mL, 0.80 mg / mL, and 1.00 mg / mL, respectively, and the antioxidant properties of the samples were determined using a total antioxidant capacity kit.

[0100] 1.2.13 Data Processing

[0101] All data were obtained through three parallel experiments and analyzed using IBM SPSS Statistics 26 software. The results were expressed as mean ± standard deviation, with P < 0.05 indicating a statistically significant difference. The data were plotted using Origin 2018 software.

[0102] 2. Results and Analysis

[0103] 2.1 Preparation and characterization of deep eutectic solvents

[0104] Fourier transform infrared spectroscopy was used to characterize DES and its components: choline chloride (ChCl), urea, levulinic acid, ethylene glycol, glycerol, and lactic acid, and to analyze the formation of hydrogen bonds between the raw material components and the synthesized DES. Figure 2 As shown in the figure, the FTIR spectra of all samples are similar, with two obvious characteristic peaks. Figure 2 (ae), divided at 1600cm -1 There are several characteristic peaks near 3300 cm, which can be attributed to the stretching vibration mode of C=C or C=O bond. -1 An obvious broad peak was observed near the DES system. This characteristic peak is usually closely related to the stretching vibration of OH or NH. Due to the enhanced hydrogen bond interaction in the system, the position and shape of the absorption peaks of NH and OH change, which is specifically manifested in the broadening and red shift of the absorption peak of the synthesized DES system.

[29] -

[30] Further analysis of the FTIR spectra of the DES-1-DES-5 system showed that the -1 、3359cm -1 、3305cm -1 、3324cm -1 、3347cm -1 Characteristic absorption peaks were observed at 3600 cm-1 and 3600 cm-2, which can be attributed to the change of vibration frequency of free OH under the action of hydrogen bonds: -1 The stretching vibration peak of OH shifts to a lower wave number of 3200-3400 cm due to the enhanced intermolecular force and the formation of hydrogen bond network. -1 Interval[ 30] For example, the FTIR spectrum of DES-2 clearly overlaps the spectra of ChCl and levulinic acid, with the 1750 and 1046 cm -1 The absorption peaks at 3600-3300 cm represent the stretching vibration of C-O and -CH2 bonds. -1 The hydroxyl stretching vibration absorption peak of DES-2 is broader than that of ChCl and levulinic acid, indicating that a large number of intermolecular hydrogen bonds are formed between the two.

[32] The results showed that a large number of hydrogen bonds were formed in the DES system, while the structure of each component did not change, indicating that the DES system was successfully prepared.

[23]

[33] .

[0105] 2.2 Effects of different extraction solvents on the yield of polyphenols in jujube pulp

[0106] Effects of different extraction solvents on the extraction rate of polyphenols from jujube pulp Figure 3As shown, the results showed that the polyphenol extraction rate of DES was higher than that of traditional ethanol extraction solvents. For example, the polyphenol contents of jujube pulp extracted by DES-1, DES-2, DES-3, DES-4 and DES-5 were 4.90 mg / g, 6.34 mg / g, 5.18 mg / g, 4.96 mg / g and 4.63 mg / g, respectively; among them, DES-2 showed the best extraction effect, and its polyphenol content was 1.6 times higher than that of traditional ethanol extraction solvents, which may be closely related to the polar characteristics of DES-2 and its molecular structure: the organic acid in the hydrogen donor component contains functional groups such as carbonyl and carboxyl, which can form strong hydrogen bond interactions with polyphenols in the raw materials.

[19] Therefore, DES-2 (choline chloride / levulinic acid) was used as the extraction solvent for polyphenols from jujube pulp and was applied in subsequent experimental studies.

[0107] 2.3 Effects of different factors on the yield of polyphenols in jujube pulp

[0108] 2.3.1 Effect of extraction temperature on the yield of polyphenols in jujube pulp

[0109] Depend on Figure 4 (a) It can be seen that within the range of 40-60℃, the yield of polyphenols in jujube pulp increased significantly with increasing temperature. This may be because the increase in temperature increased the interaction between polyphenols and the matrix, promoted the dissolution of polyphenols in jujube pulp, and at the same time, higher temperature improved the diffusion and penetration ability of DES. When the extraction temperature was 60℃, the extraction yield reached the maximum value of 6.51 mg / g; however, when the extraction temperature increased to 70-80℃, the polyphenol yield decreased significantly. This may be because the high temperature caused the polyphenols in jujube pulp to be degraded and destroyed, resulting in a significant decrease in the yield.

[34] The results showed that temperature had a significant effect on the yield of polyphenols from the pulp of sour jujube, and 60℃ was determined to be the optimal extraction temperature for polyphenols from the pulp of sour jujube.

[0110] 2.3.2 Effect of DES water content on polyphenol yield in jujube pulp

[0111] Depend on Figure 4 As shown in (b), with the increase of water content, the yield of polyphenols from jujube pulp showed a trend of first increasing and then decreasing. When the water content was lower than 20% (v / v), the high viscosity of the extraction solvent limited the mass transfer efficiency of jujube pulp polyphenols to the DES medium. When the water content exceeded 20% (v / v), the yield of polyphenols gradually decreased, which may be due to the fact that excess water weakened the hydrogen bond interaction between jujube pulp polyphenols and DES.

[35] It is worth noting that the extraction efficiency at 40% water content decreased by 1.67 mg / g compared to 3.56 mg / g at 30% (v / v). This may be because the unique hydrogen bond network structure of DES was destroyed by the addition of a large amount of water, thereby increasing the polarity of the extraction medium and causing a significant decrease in the extraction yield.

[27] The results showed that the polyphenol yield peaked at 20% (v / v) water content in DES, corresponding to a polyphenol yield of 4.56 mg / g. This result may be attributed to the fact that the optimal water content reduced the viscosity and surface tension of DES, while simultaneously improving DES fluidity and enhancing the mass transfer efficiency of the solvent into the raw plant, thereby promoting the dissolution of polyphenols in DES. Therefore, a 20% (v / v) water content was determined to be the optimal choice for polyphenol extraction from jujube pulp.

[0112] 2.3.3 Effect of extraction time on the yield of polyphenols in jujube pulp

[0113] Depend on Figure 4 (c) It can be seen that when the extraction time is within the range of 10 to 40 minutes, the polyphenol extraction rate in the extract is significantly positively correlated with the extraction time. As time increases, the polyphenol yield gradually increases, reaching a maximum value of 8.21 mg / g when the extraction time is 40 minutes. The reason may be that increasing the extraction time can promote the contact between the extraction solvent and the sour jujube pulp, which is beneficial for the diffusion of polyphenols into the solution, thereby increasing the polyphenol yield. When the extraction time exceeds 40 minutes, the continued increase in time will lead to a decrease in the extraction rate. This may be because the long-term heating causes the phenolic hydroxyl groups in the polyphenols to undergo chemical reactions, destroying the structure of the polyphenols, resulting in a decrease in the extraction rate.

[36] -

[37] Therefore, 40 minutes is the best extraction time.

[0114] 2.3.4 Effect of material-liquid ratio on the yield of polyphenols in jujube pulp

[0115] In order to improve the extraction efficiency and maximize the cost-effectiveness, the effect of the material-liquid ratio on the yield of polyphenols from jujube pulp was systematically studied. Figure 4As shown in (d), the polyphenol yield first increases and then decreases with increasing solid-liquid ratio. When the solid-liquid ratio is 1:40 g / mL, the polyphenol yield reaches a maximum of 5.8 mg / g. This may be because the continuous increase in the solid-liquid ratio allows the polyphenols to diffuse better into the solution, thereby improving the extraction yield. When the solid-liquid ratio continues to increase to the range of 1:40 g / mL to 1:50 g / mL, the contact area between the extraction solvent and the sample decreases due to the increase in solution volume, which not only reduces the extraction yield but also produces unnecessary byproducts and increases actual costs. It was also found that the extraction efficiency did not significantly improve within the solid-liquid ratio range of 1:30 g / mL to 1:40 g / mL. Considering the extraction efficiency and solvent consumption, 1:30 g / mL was selected as the optimal solid-liquid ratio. This condition not only meets the requirements for the extraction of polyphenols from jujube pulp, but also effectively reduces solvent usage, showing good practical application value.

[0116] 2.4 Orthogonal test process optimization

[0117] Water content (A), extraction time (B), extraction temperature (C), and solid-liquid ratio (D) were selected as the investigation factors to design a four-level three-factor orthogonal experiment to carry out the optimization experiment of the polyphenol extraction process of jujube pulp. The experimental results and analysis are shown in Table 3.

[0118] The range analysis in Table 3 revealed that D > C > A > B, meaning that the order of influence of the four factors on the polyphenol yield from jujube pulp during the extraction process was solid-liquid ratio > extraction temperature > water content > extraction time. The solid-liquid ratio had the greatest significant effect on the polyphenol extraction rate, while extraction time had the least significant effect. The optimal parameters for the jujube pulp polyphenol extraction process were determined to be A1B2C2D3: water content 10%, extraction time 40 min, extraction temperature 60°C, and solid-liquid ratio 1:30 g / mL. Under these conditions, the polyphenol yield was 10.5 mg / g, the highest among all experimental groups and 1.64 times higher than the initial method. Therefore, these parameters were determined to be the optimal extraction process conditions. The variance analysis results in Table 4 show that the solid-liquid ratio, water content, and extraction temperature all had significant effects on the polyphenol extraction rate from jujube pulp.

[0119] Table 3 Orthogonal experiment results

[0120]

[0121] Table 4 Index variance analysis table

[0122] source sum of squares degrees of freedom variance F-number Significance A 0.294 2 0.147 0.02 * B 0.086 2 0.043 0.00 C 0.682 2 0.341 0.04 * D 17.715 2 8.858 25.99 **

[0123] Note: ** indicates extremely significant difference (P < 0.05), * indicates significant difference (P < 0.01)

[0124] 2.5 Changes in the microstructure of jujube pulp before and after extraction

[0125] Figure 5 The scanning electron microscopy results of the sample residues obtained after the sour jujube pulp was extracted with different extraction solvents at different magnifications are shown. Figure 5 Figures A and D show that the unextracted jujube pulp powder is smooth and has no holes, and is in the form of granules. Figure 5 Figures B and E show that after 70% (v / v) ethanol extraction, the pulp powder of the sour jujube fruit was flat and had less granular structure; it is worth noting that, Figure 5 F shows that the residue after DES extraction has almost no granular structure and has a large number of evenly distributed pores on the surface. This morphological feature indicates that DES can better penetrate the sample itself and achieve the extraction effect. At the same time, based on previous experiments, it was found that under the conditions of high concentration of DES (water content 10% (v / v)) and long extraction time (<40min), DES and polyphenols have an interactive effect, among which high concentration of DES has a positive effect on the activity of the extract; this may also be the reason why DES can improve the extraction rate of polyphenols.

[37] -

[41] .

[0126] 2.6 Spike recovery

[0127] As shown in Table 5, 1.0 mL of sample extraction solution was weighed respectively, and the total phenol content in the sample was measured to be 0.95, 0.89, and 0.90 mg / mL, respectively. Then, 1.0 mg of gallic acid standard was added to the sample solution and the determination was carried out according to the same method. According to the recovery formula, the recovery rates were calculated to be 97%, 98%, and 100%, respectively. The average recovery rate was 99%, and the RSD was 1.6%, indicating that the quantitative analysis of polyphenol content determined by this method is accurate and feasible.

[0128] Table 5 Spike recovery

[0129]

[0130] 2.7 Study on the antioxidant activity of polyphenols in the pulp of jujube

[0131] 2.7.1 DPPH free radical scavenging rate determination

[0132] Jujube pulp polyphenols have a significant scavenging ability for DPPH free radicals, such as Figure 6The results showed that within the concentration range of 0.04 to 1.0 mg / mL, the clearance rate showed a significant dose-dependence, increasing from 42.1% to 92.0%, indicating that its free radical capture efficiency was high; when the concentration exceeded 0.3 mg / mL, the rate of increase in the clearance rate slowed down, reaching 91.5% at 0.6 mg / mL, which was comparable to the clearance rate of VC; and within the concentration range of 0.6 to 1.0 mg / mL, the clearance rate tended to be stable, which may mean that the antioxidant capacity has approached saturation.

[42] Through comparative studies with VC, we found that the clearance rate of jujube pulp polyphenols reached 60.6% at a concentration not exceeding 0.15 mg / g, which was comparable to the 61.2% clearance rate of VC under the same conditions. In addition, the half-maximal inhibitory concentration (IC 50 The value of VC was 0.06 mg / g, which is lower than VC's 0.13 mg / g. This shows that under low concentration conditions, jujube pulp polyphenols exhibit a stronger free radical scavenging ability. These research results are consistent with recent research reports on the antioxidant activity of plant polyphenols, further proving that jujube pulp polyphenols, as a natural antioxidant, have significant application potential in the fields of food and health products.

[43]

[43] .

[0133] 2.7.2ABTS + Free radical scavenging rate assay

[0134] according to Figure 7 As shown, the effects of polyphenols and VC in jujube pulp on ABTS + The free radical scavenging ability showed concentration dependence. In the concentration range of 0.04-0.3 mg / mL, the scavenging rate of jujube pulp polyphenols increased from 19.32% to 59.07%, while the scavenging rate of VC increased from 11.73% to 66.62%. This shows that in this concentration range, the dose-effect curve of VC is more significant. However, when the concentration was increased to 0.6 mg / mL, the scavenging rates of jujube pulp polyphenols and VC reached 89.24% and 91.35%, respectively, and the two were close; while at 0.7 mg / mL, the scavenging rate of jujube pulp polyphenols (98.56%) was significantly higher than that of VC (93.82%) at the same concentration. The results show that under high concentration conditions, jujube pulp polyphenols have stronger free radical saturation scavenging ability. This phenomenon of quickly reaching a saturated scavenging state at high concentrations may be related to the cooperative electron donation mechanism of phenolic hydroxyl groups.

[45] It is noteworthy that the maximum clearance of both substances was close to 100%, which is consistent with the dose-response characteristics of typical antioxidants.

[46] In summary, the polyphenols in the pulp of jujube showed a strong free radical scavenging ability, revealing its great potential application value as a natural antioxidant in the fields of food and medicine.

[0135] 2.7.3 Determination of total reducing capacity

[0136] according to Figure 8 As shown, the reducing abilities of both jujube pulp polyphenols and VC increased with increasing concentration, although their dose-effect relationships exhibited some variability. Within the concentration range of 0.013–0.029 mg / mL, the total reducing power of VC (3.12–4.85 μmol / mL) was significantly higher than that of jujube pulp polyphenols (1.87–3.04 μmol / mL), indicating that VC exhibited strong electron-donating capacity even at extremely low concentrations, likely due to its high-reduction potential of the enediol structure. However, with continued concentration increases, the rate of increase in the reducing power of jujube pulp polyphenols accelerated. Within the concentration range of 0.148–0.220 mg / mL, the reducing power of jujube pulp polyphenols increased from 5.03 μmol / mL to 7.50 μmol / mL, at which point the reducing efficiency of jujube pulp polyphenols approached that of VC. This phenomenon suggests that at higher concentrations, the polyhydroxybenzene ring structure in jujube pulp polyphenols may enhance electron transfer capacity through a synergistic effect. Based on these conclusions, jujube pulp polyphenols showed a reduction potential comparable to that of VC at concentrations > 0.067 mg / mL.

[47] , confirming that sour fruit polyphenols have the development value of being a natural antioxidant

[47] .

[0137] The present invention uses low eutectic solvent technology to extract polyphenols from the pulp of sour jujube, systematically optimizes the extraction process parameters, analyzes the influence of different factors on the yield of polyphenols, and evaluates the antioxidant activity of polyphenols in the pulp of sour jujube. Compared with traditional solvents, DES-2 (choline chloride / levulinic acid) shows significant advantages when used as an extraction solvent, and its polyphenol yield is increased by 1.6 times. Through single-factor and orthogonal experiments, the optimal extraction process conditions were determined to be 20% water content, 40min extraction time, 60°C extraction temperature, and 1:30g / mL solid-liquid ratio. Under these conditions, the polyphenol yield can reach 10.5mg / g. Scanning electron microscopy shows that DES has a good ability to penetrate the sample and can significantly improve the extraction efficiency of polyphenols. The results of the antioxidant experiment show that when the sour jujube pulp polyphenols are at 0.04mg / mL and 0.07mg / mL, DPPH and ABTS + The free radical scavenging rate is better than that of VC at the same concentration. And the reducing ability increases with the increase of concentration. Its IC 50 The present invention confirms the high efficiency of DES in the field of plant polyphenol extraction and provides a new research idea for the green extraction and application of jujube pulp polyphenols by regulating its extraction process.

[0138] Although the present invention has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

[0139] References:

[0140] [1]ZHANG Y, LI Y, REN X, et al. Comparative study on the nutritional quality of peanut in saline and non-saline land[J]. Foods, 2024, 13(23):3751-3751.

[0141] [2] Jin Zhichang, Liu Guoqiang, Wu Hongxia. Main characteristics and supporting cultivation techniques of the new jujube variety 'Xingsuan No. 19'[J]. Yantai Fruit Trees, 2025, (01): 20-21.

[0142] [3] Ye Hui. Study on the extraction, separation and activity of polyphenols from jujube peel[D]. Tianjin University of Science and Technology, 2009.

[0143] [4] Guo Shuai, Li Xiaoguang, Sun Yehong, et al. A review of the current status of the development of the jujube industry in Xingtai [J]. Agricultural Technology and Equipment, 2024, (12): 68-69+73.

[0144] [5] Gong Li, Jie Junbo, Lai Changjiangsheng, et al. Research progress on comprehensive utilization of jujube seeds and their by-products [J]. Chinese Journal of Experimental Traditional Chinese Medicine, 2021, 27(03): 222-230.

[0145] [6]ZOU B,LI T,XU Y,et al.Structural identification and antioxidantpotency evaluation of pomelo vinegar polyphenols[J].Food Bioscience,2022,47:101674.

[0146] [7] Gao Min, Wang Qing, Wang Xinlan, et al. Research progress in the extraction of flavonoids using deep eutectic solvents[J]. Chemical Engineer, 2024, 38(02): 55-58.

[0147] [8] Wang Yu, He Yunxiang, Hong Gonghua, et al. Research progress on high-value transformation and application of plant polyphenols[J]. Chinese Science: Chemistry, 2025, 55(01): 37-49.

[0148] [9] Tan Tianyu. Study on extraction of pomegranate seed polyphenols by deep eutectic solvent and its microencapsulation[D]. Hebei University of Engineering, 2022.

[0149]

[10] Chemat F, Vian MA, Cravotto G. Green extraction of natural products: Concept and principles [J]. International Journal of MolecularSciences, 2012, 13(7): 8615-8627.

[0150]

[11] YANG L, BRENT JF, BAI JM, et al. Natural deep eutectic solvents: Properties, applications, and perspectives. [J]. Journal of Natural Products, 2018, 81(3): 679-690.

[0151]

[12] DAI Y,SPRONSEN VJ,WITKAMP G,et al.Natural deep eutectic solvents as new potential media for green technology[J].Analytica Chimica Acta,2013:76661-68.

[0152]

[13] QIAN J, LI HY, LUO D, et al. Green extraction of α-nitroso-β-naphthol from wastewater using hydrophobic deep eutectic solvents: A comprehensive study of efficiency and mechanism [J]. Environmental Pollution, 2025, 369125855-125855.

[0153]

[14] Yuan Keying, Wang Haochen, Mao Yu, et al. Research progress of deep eutectic solvents in the extraction of plant active ingredients[J]. Journal of Mudanjiang Medical College, 2022, 43(02): 101-103.

[0154]

[15] ZHANG HL, ZHAO WT, BAT, et al. Sustainable extraction of polyphenols from millet using switchabledeep eutectic solvents[J]. LWT-FoodScience and Technology, 2022,170:114082.

[0155]

[16] ALASALVAR H.Ultrasound technology and eco-friendly solvents forextracting antioxidant phenolic compounds from immortelle(Helichrysumitalicum)flowers:A comparative study on conventional and natural deepeutectic solvents[J].Microchemical Journal,2025,208112390-112390.

[0156]

[17] LIU Y, FRIESEN JB, MCALPINE JB, et al. Natural deep eutecticsolvents: Properties, applications, and perspectives. [J]. Journal of Natural Products, 2018, 81(3): 679-690.

[0157]

[18] MARIANA R, CRUZ MF, ERWANN D. Application of deep eutectic solvents (DES) for phenolic compounds extraction: Overview, challenges, and opportunities [J]. Journal of Agricultural and Food Chemistry, 2017, 65(18): 3591-3601.

[0158]

[19] ELIK A,Altunay N.Optimization of deep eutectic solvent basedultrasonic assisted microextraction for determination of zearalenone residuesin foods[J].Journal of Food Composition and Analysis,2024,132:106304.

[0159]

[20] LI L,LV J,WANG X,et al.Green extraction of polyphenols fromelaeagnus angustifolia L.Using natural deep eutectic solvents and evaluationof bioactivity[J].Molecules,2024,29(11):2412.

[0160]

[21] ABBOTT A P,CAPPER G,DAVIE D L,RASHEED R K.Novel solventproperties of choline chloride / urea mixtures[J].Chemical Communications(Cambridge,England),2003,(1):70-1.

[0161]

[22] ZHAO B Y,XU P,YANG F X,et al.Biocompatibledeep eutectic solventsbased on choline chloride:Characterization and application to the extractionof rutin from sophora japonica[J].ACS Sustainable Chemistry&Engineering,2015,3(11):2746-2755.

[0162]

[23] MS,LONGO,MA,DEIVE FJ,et al.Synthesis and characterization of a lipase-friendly DES based on cholinium dihydrogenphosphate[J].Journal of Molecular Liquids,2021,340.

[0163] [twenty four] A,et al.Synthesis and characterization of alipase-friendly DES based on cholinium dihydrogen phosphate[J].Journal ofMolecular Liquids,2021,340:117230.

[0164]

[25] SONG Z, HU

[0165]

[26] Xiong Ruqin, Li Ping, Wang Rui. Determination of total phenol content in Zanthoxylum bungeanum L. by Folin-Ciocalteu colorimetry[J]. Chinese Condiments, 2019, 44(10): 140-143.

[0166]

[27] DAI Y,WITKAMP G,VERPOORTE R,et al. Tailoring properties of naturaldeep eutectic solvents with water to facilitate their applications[J].FoodChemistry,2015,18714-19.

[0167]

[28] K, N, GV,et al.Natural deep eutectic solvents asbeneficial extractants for enhancement of plant extracts bioactivity[J].LWT-Food Science and Technology,2016,7345-51.

[0168]

[29] TANG L,HUANG H.Evaluation of pineapple peel cellulosenanocrystals / EGCG complexes for improving the stability of curcumin emulsion[J].Cellulose,2022,29(11):6123-6141.

[0169]

[30] Liu Runpeng. Preparation and performance study of high antifreeze gelatin hydrogel[D]. Qilu University of Technology, 2024.

[0170]

[31] JI HR,LV P L.Mechanistic insights into the lignin dissolutionbehaviors of a recyclable acid hydrotrope,deep eutectic solvent(DES),andionic liquid(IL)[J].Green Chemistry,2020,22(4):1378-1387.

[0171]

[32] Li Huan. Application research of deep eutectic solvents in the detection of bisphenol compounds in food and environment[D]. Shanghai Ocean University, 2024.

[0172]

[33] SHAFIE HM,YUSOF R,GAN C.Synthesis of citric acid monohydrate-choline chloride based deep eutectic solvents(DES)and characterization oftheir physicochemical properties[J].Journal of Molecular Liquids,2019,288-111081.

[0173]

[34] H,KUREK AM.Deep eutectic solvents for the extraction ofpolyphenols from food plants[J].Food Chemistry,2024,444:138629.

[0174]

[35] PURIFICATION T.Reports on purification technology findings from northeast forestry university provide new insights (Application of naturaldeep eutectic solvents for extraction and determination of phenolics inCajanus cajan leaves by ultra performance liquid)[J].Chemicals&Chemistry,2015,1038:1-10.

[0175]

[36] ZHANG L,WANG M. Optimization of deep eutectic solvent-basedultrasound-assisted extraction of polysaccharides from Dioscorea oppositaThunb[J]. International Journal of Biological Macromolecules, 2017, 95675-681.

[0176]

[37] Su Jingyuan, Zhang Jing, Liu Xin, et al. Optimization of extraction technology of black wheat bran polyphenols by deep eutectic solvent using response surface methodology [J]. Grain and Oils, 2024, 37(03): 22-26.

[0177]

[38] T,PHILIPPE S,SAMIRA B,et al.Deep eutectic solvents for theextraction and stabilization of Ecuadorian quinoa(Chenopodium quinoa Willd.)saponins[J].Journal of Cleaner Production,2022,363:132609.

[0178]

[39] Sun Yan, Cui Xusheng, Liu Jing, et al. Optimization of the extraction process of flavonoids from jujube leaves and their anti-oxidative damage activity in Caenorhabditis elegans [J]. Food Industry Science and Technology, 2020, 41(08): 143-150.

[40] Su Jingyuan, Zhang Jing, Liu Xin, et al. Optimization of the extraction process of polyphenols from black wheat bran using deep eutectic solvents using response surface methodology [J]. Grain and Oils, 2024, 37(03): 22-26.

[0179]

[41] NIDA A, DILDAR A.DES-based microwave-and ultrasound-assisted extraction of natural products from Rumex hastatus as per response surfacemethodology[J].Sustainable Chemistry and Pharmacy, 2023,36:101289.

[0180]

[42] Prior RL, Wu

[0181]

[43] Feng S M,Luo Z S,Zhang Y B,et al.Phytochemical contents andantioxidant capacities of different parts of two sugarcane(Saccharumofficinarum L)cultivars[J].Food Chemistry.2014,151:452-458.

[0182]

[44] Dai J,Mumper R J.Plant phenolics:Extraction,analysis and theirantioxidant and anticancer properties[J].Molecules2010,15(10):7313-7352.

[0183]

[45] Balasundram N,Sundram K,Samman S.Phenolic compounds in plants andagri-industrial by-products:Antioxidant activity,occurrence,and potentialuses[J]Food Chemistry,2006,99(1):191-203.

[0184]

[46] Li Y,Jiang B,Zhang T,Mu W.Antioxidant and free radical-scavengingactivities of chickpea protein hydrolysate(CPH)[J]Food Chemistry,2008,106(2):444-450.

[0185]

[47] Prior R L,Wu X,Schaich K.Standardized methods for thedetermination of antioxidant capacity and phenolics in foods and dietarysupplements[J]Journal of Agricultural and Food Chemistry.2005,53(10):4290-302.

[0186]

[48] Zhang H,Tsao R.Dietary polyphenols,oxidative stress andantioxidant and anti-inflammatory effects[J]Current Opinion in Food Science,2016,8:33-42.

Claims

1. A process for extracting polyphenols from jujube pulp based on a deep eutectic solvent, characterized in that: The jujube pulp is dried at low temperature and crushed to obtain jujube pulp powder; the jujube pulp powder is mixed with a deep eutectic solvent and extracted at a certain temperature, and the obtained extract contains polyphenol compounds; The deep eutectic solvent is a choline chloride-levulinic acid deep eutectic solvent.

2. The process according to claim 1, characterized in that The molar mass ratio of choline chloride to levulinic acid in the deep eutectic solvent is 1:1.

2.

3. The process according to claim 2, characterized in that The water content of the deep eutectic solvent is 10%.

4. The process according to claim 3, characterized in that The material-liquid ratio of the sour jujube pulp powder to the low eutectic solvent is 1g:30mL.

5. The process according to claim 1, characterized in that The extraction temperature was 60 ℃ and the extraction time was 40 min.

6. The process according to any one of claims 1 to 5, characterized in that The sour jujube pulp is dried at low temperature and then crushed and passed through an 80-mesh sieve to obtain sour jujube pulp powder.

7. The polyphenols from the sour jujube pulp obtained by extraction according to the process described in any one of claims 1 to 6.

8. Use of the sour jujube pulp polyphenols according to claim 7 in the preparation of antioxidants.

9. Use of the sour jujube pulp polyphenols according to claim 7 in the fields of food and health products.

Images