Method for extracting macadamia nut green peel polyphenol by using eutecticevaporate solvent screened based on molecular simulation

Abstract

The invention discloses a method for extracting macadamia nut green peel polyphenol by screening a deep eutectic solvent (DES) based on molecular simulation, and belongs to the field of molecular simulation and natural product extraction. The method comprises the following steps: firstly, quantitatively analyzing the composition of the macadamia nut green peel polyphenol, then based on the composition of the green peel polyphenol, researching the dissolving-out capacity of DES composed of different hydrogen bond donors / hydrogen bond receptors on the main polyphenol of the macadamia nut by adopting molecular simulation, screening DES with different hydrogen bond donor / hydrogen bond receptor compositions and molar ratios, and determining the content of the main polyphenol in the macadamia nut. Finally, the screened DES system is subjected to process optimization, and the optimal DES proportion is obtained. The DES system can be rapidly screened on the basis of the main composition of macadamia nut green peel polyphenol, the polyphenol yield is increased, and the problems of large use amount of an organic solvent and low extraction efficiency in traditional polyphenol extraction are solved.

Description

Technical Field

[0001] The invention belongs to the field of molecular simulation and natural product extraction, and specifically relates to a method for extracting macadamia nut green peel polyphenols by screening a low eutectic solvent based on molecular simulation. Background Art

[0002] Macadamia tegrifolia is an evergreen tree of the Proteaceae family and the Macadamia genus. It is also known as macadamia nut and is mainly composed of kernel, shell and green peel. The kernel of macadamia nut, as the edible part of macadamia nut, accounts for 17% of the weight of fresh fruit, while the green peel, which accounts for 45% to 60% of the weight of fresh macadamia nut, is currently discarded at will, except for a very small amount used for composting or feed, resulting in a waste of resources. Studies have shown that the green peel of macadamia nut is rich in polyphenols and flavonoids, and has excellent antioxidant, anti-inflammatory and antibacterial activities. However, traditional polyphenol extraction usually uses organic reagents such as methanol, ethanol, ethyl acetate, dichloromethane, ether, etc. as extraction media, which has safety and environmental problems such as volatility and high toxicity. For example, the invention patent application with publication number CN106580778A discloses a macadamia nut green peel extract, macadamia nut green peel polyphenol or macadamia nut green peel water extract, which is prepared by the following method: taking macadamia nut green peel powder, soaking it three times with warm water, then adding 5% sulfuric acid, cold soaking for 24 hours, and filtering; washing the filter cake with deionized water to remove residual sulfuric acid until the washing liquid is neutral, and obtaining macadamia nut green peel polyphenol. The extraction efficiency of this method is extremely low.

[0003] In addition, the research team of the South Asian Tropical Crops Research Institute of the Chinese Academy of Tropical Agricultural Sciences published a column on the analysis and antioxidant activity of macadamia nut green peel polyphenols. They used ultrasound-assisted extraction of phenolic substances in macadamia nut green peel, and analyzed the phenolic composition through purification and liquid chromatography-mass spectrometry. The research team obtained the optimal conditions for ultrasound-assisted extraction of phenolic substances in macadamia nut green peel through response surface optimization, and the extraction rate was low.

[0004] Nowadays, deep eutectic solvents (DES), as a new type of green solvent developed in the past two decades, are composed of hydrogen bond donors and hydrogen bond acceptors. Their physical and chemical properties can be changed by changing the composition and molar ratio of hydrogen bond acceptors / hydrogen bond donors. They have the advantages of good biocompatibility, low cost, simple preparation, and environmental friendliness. In addition, the extraction efficiency of the target product is high, so they are widely used in the extraction of natural products. At present, the screening of polyphenols extracted by DES is mainly explored through a large number of experiments. However, there are many types of hydrogen bond donors and hydrogen bond acceptors, and there are significant differences in the extraction of polyphenols. The workload is large and it will cause waste of drugs. Therefore, it is necessary to develop a rapid screening method for the DES system to achieve efficient extraction of natural products. Based on this, molecular simulation was used to quickly and efficiently screen the DES system for extracting polyphenols from macadamia green peel, which not only improved the extraction rate of polyphenols, but also reduced the time-consuming solvent screening. Summary of the invention

[0005] The purpose of the present invention is to propose a method for screening low eutectic solvents based on molecular simulation for extracting macadamia nut green peel polyphenols, which can quickly screen the DES system based on the main components of macadamia nut green peel polyphenols, improve the yield of polyphenols, and solve the problems of large amount of organic solvents used and low extraction efficiency in traditional polyphenol extraction.

[0006] To achieve the above technical effects, the present invention discloses a method for screening a low eutectic solvent based on molecular simulation for extracting macadamia nut green peel polyphenols. First, the composition of macadamia nut green peel polyphenols is quantitatively analyzed. Then, based on the composition of green peel polyphenols, molecular simulation is used to study the dissolution ability of DES with different hydrogen bond acceptor / hydrogen bond donor compositions on the main polyphenols of macadamia nut, and DES with different hydrogen bond acceptor / hydrogen bond donor compositions and molar ratios are screened. Finally, the screened DES system is subjected to process optimization to obtain the optimal low eutectic solvent ratio.

[0007] The specific steps include: (1) The polyphenols from macadamia nut peel were extracted using traditional organic solvents (ethanol). The extract was concentrated under negative pressure and freeze-dried under negative pressure to obtain a crude polyphenol extract. The polyphenol composition was identified using UPLC-MSI-QTOF-MS / MS. (2) Use Chem 3D software to construct the molecular structures of target polyphenols and hydrogen bond acceptors and donors; (3) The molecular structure constructed in step (2) is structurally optimized and energetically optimized at the BP-TZVPD-FINE level using Turbomole software to obtain a reasonable molecular configuration file; (4) The relative solubility of the molecular configuration optimized in step (3) was calculated using COSMOtherm software to preliminarily determine the composition and molar ratio of hydrogen bond acceptors / hydrogen bond donors; (5) Mix the hydrogen bond acceptor and the hydrogen bond donor according to the combination and molar ratio determined in step (4), add 30% water according to the mass ratio, heat and stir at 80 °C for 8 h at a stirring speed of 150 rpm to prepare DES; (6) The crushed macadamia nut green peel powder that passed through a 60-mesh sieve was mixed with the DES prepared in step (5) at a solid-liquid ratio of 1:40, and ultrasonically extracted at 250 W in a 40°C water bath for 10 min to determine the hydrogen bond acceptor / hydrogen bond donor composition; (7) The crushed macadamia nut green peel powder that has been passed through a 60-mesh sieve is mixed with the DES (water content 20%-60%) of the hydrogen bond acceptor / hydrogen bond donor composition determined in step (6) at a solid-to-liquid ratio of 1:10-1:50, and ultrasonically extracted at an ultrasonic power of 200-400 W in a 30-70 °C water bath for 5-25 min. The obtained extract is filtered through a 0.45 µm organic filter membrane, the polyphenol concentration in the extract is determined, and the polyphenol yield is calculated.

[0008] Furthermore, in step (1), the macadamia nut green peel polyphenols mainly include 3,4-dihydroxybenzoic acid, p-hydroxybenzoic acid, 3,4-dihydroxybenzaldehyde, gallic acid and vanillic acid.

[0009] Furthermore, the hydrogen bond acceptor is choline chloride, betaine, proline, alanine, and arginine, and the hydrogen bond donor is formic acid, acetic acid, propionic acid, lactic acid, levulinic acid, ethylene glycol, glycerol, erythritol, 1,2-butanediol, 1,3-butanediol, urea, methyl urea, and acetamide; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1-1:4.

[0010] Furthermore, in the step (2), the main polyphenols in the green peel of macadamia nut, the hydrogen bond acceptors and hydrogen bond donors are constructed using Chem 3D to export a SFD format file; in the step (3), the molecular structure is structurally optimized and energetically optimized at the BP-TZVPD-FINE level using Turbomole software to export a COSMO format file.

[0011] Furthermore, in the step (4), COSMOtherm software calculates the relative solubility, the target component is set as the solute in MultipleSolvents, and the solute is defined as a solid; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1-1:4; and the relative solubility log(x_RS) is calculated at 25°C.

[0012] Furthermore, in step (6), the hydrogen bond acceptor / hydrogen bond donor composition is choline chloride and 1,2-butanediol in a molar ratio of 1:1.

[0013] Furthermore, in step (7), the extraction conditions are: DES water content 40%, ultrasonic power 285 W, solid-liquid ratio 1:43, extraction temperature 40 °C, and extraction time 10 min.

[0014] Furthermore, in step (7), the extraction rate of macadamia nut green peel polyphenols is 94.03 mg gallic acid equivalent / g sample dry weight (mg GAE / g DW).

[0015] Furthermore, in step (7), the extraction rate of macadamia nut green peel polyphenols is 5.16 times that of traditional organic solvent extraction.

[0016] The present invention has the following beneficial effects: The present invention is based on the main polyphenol composition of macadamia nut green peel, adopts a molecular simulation method, and uses the relative solubility log(x_RS) of the target substance in DES to quickly and efficiently screen the DES composition and molar ratio of macadamia nut green peel polyphenol extraction, and combines the DES composition and molar ratio verification and extraction process optimization to obtain the optimal process conditions for extracting macadamia nut green peel polyphenol by DES. The method provided by the present invention quickly and efficiently screens the DES composition and molar ratio, and greatly improves the extraction rate of macadamia nut green peel polyphenol, and the extraction rate reaches 94.03 mg GAE / g DW.

[0017] The method provided by the present invention has a significantly higher extraction rate of macadamia nut green peel than the traditional ethanol extraction method, which is 5.16 times that of the traditional ethanol extraction method. At the same time, compared with the traditional organic solvent extraction method, the method provided by the present invention is environmentally friendly, has low volatility, strong solubility, high safety, and low price, and provides a more effective method for extracting macadamia nut green peel polyphenols. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 HPLC-MS / MS spectrum of macadamia nut peel polyphenols.

[0019] Figure 2 Configuration and charge density distribution of major polyphenols in macadamia nut peel.

[0020] Figure 3 Relative solubility of target substances in DES with a hydrogen bond acceptor / hydrogen bond donor molar ratio of 1:1.

[0021] Figure 4 Relative solubility of target substances in DES with a hydrogen bond acceptor / hydrogen bond donor molar ratio of 1:2.

[0022] Figure 5 Relative solubility of the target substances in DES with a hydrogen bond acceptor / hydrogen bond donor molar ratio of 1:3.

[0023] Figure 6Relative solubility of target substances in DES with a hydrogen bond acceptor / hydrogen bond donor molar ratio of 1:4.

[0024] Figure 7 Effects of extraction conditions with different moisture contents on the extraction rate of DES polyphenols from macadamia nut peel.

[0025] Figure 8 Effects of extraction conditions with different solid-liquid ratios on the extraction rate of macadamia nut peel polyphenols using DES.

[0026] Fig. 9 Effects of different extraction temperatures on the extraction rate of macadamia nut peel polyphenols extracted by DES.

[0027] Fig.10 Effects of extraction conditions with different extraction times on the extraction rate of macadamia nut green peel polyphenols extracted by DES.

[0028] Fig.11 Effect of different ultrasonic power extraction conditions on the extraction rate of macadamia nut green peel polyphenols by DES. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field. The extraction solvents used in the experiments of the present invention are all analytically pure, and the water used is deionized water unless otherwise specified.

[0031] Example 1: Identification of macadamia nut peel polyphenols (1) Accurately weigh 1.50 g of macadamia green peel sample that passed through a 60-mesh sieve into a 100 mL extraction bottle, add 30% ethanol solution at a solid-liquid ratio of 1:45, and extract for 10 min at an ultrasonic power of 140 W and an extraction temperature of 43 °C. After the extraction, the extract was filtered, concentrated under negative pressure, and freeze-dried under negative pressure to obtain a solid powder of crude extract of macadamia green peel polyphenols.

[0032] (2) Accurately weigh 30 mg of macadamia nut green peel polyphenol extract and dissolve it in 500 μL of 30% ethanol solution containing internal standards succinic acid-2,2,3,3-d4 and L-2-chlorophenylalanine. UPLC conditions: Waters ACQUITY ultra-high performance liquid chromatography system, using ACQUITY UPLC HSS T3 column (100×2.1 mm, 1.8 μm), flow rate of 0.35 mL / min, column temperature of 40°C, injection volume of 5 μL. In positive ion mode, the mobile phases were (A) 0.1% formic acid-water solution, (B) acetonitrile, and the gradient elution program was: linear gradient program: 0-3 min 95-75% A, 5-12 min 75-56.2% A, 12-14.4 min 56.2-1% A, 14.2-14.4-15min 1-95% A. The HPLC-MS spectrum of macadamia nut peel polyphenols is shown in Figure 1 The main polyphenol composition of macadamia nut green peel is shown in Table 1.

[0033] Table 1 Main polyphenol compositions of macadamia nut peel Example 2: Molecular simulation screening of DES for extracting macadamia nut peel polyphenols (1) 3,4-dihydroxybenzoic acid, p-hydroxybenzoic acid, 3,4-dihydroxybenzaldehyde, gallic acid and vanillic acid were used as target substances. The molecular structure was constructed using Chem 3D. After structural optimization and energy optimization were performed using Turbomole software, the COSMO format file was exported to obtain the surface charge density map of the main polyphenols in the green peel of macadamia nut. Figure 2 As shown. Among them, red represents the "hydrogen acceptor" site and blue represents the "hydrogen donor" site.

[0034] (2) The surface charge density maps of hydrogen bond acceptors and hydrogen bond donors were constructed using Chem 3D and Turbomole software. The hydrogen bond acceptors were choline chloride, betaine, proline, alanine, and arginine, and the hydrogen bond donors were formic acid, acetic acid, propionic acid, lactic acid, levulinic acid, ethylene glycol, glycerol, erythritol, 1,2-butanediol, 1,3-butanediol, urea, methylurea, and acetamide.

[0035] (3) The COSMO files of the main polyphenols, hydrogen bond acceptors and hydrogen bond donors of macadamia nut green peel were imported into the COSMOtherm program. In Multiple Solvents, the target component was set as the solute, and the solute was defined as a solid. The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor was 1:1-1:4. The relative solubility log(x_RS) was calculated at 25 °C. The larger the log(x_RS) value, the stronger the solubility of the target component in DES.

[0036] (4) Use Origin mapping software to create heat maps of hydrogen bond acceptor and hydrogen bond donor molar ratios of 1:1-1:4, such as Figure 3-6 The darker the red color, the stronger the solubility of the target component in DES.

[0037] Example 3: Screening of DES-extracted macadamia nut peel polyphenols (1) According to the relative solubility log(x_RS) and heat map of the target component in DES calculated in Example 3, 20 DES were screened for verification experiments, as shown in Table 2.

[0038] (2) The hydrogen bond donor and hydrogen bond acceptor combination and molar ratio selected in step (1) of Example 3 were mixed, 30% water was added according to the mass ratio, and the mixture was heated and stirred at 80°C for 8 h at a stirring speed of 150 rpm to form a transparent liquid to prepare DES, and the viscosity of DES was measured, as shown in Table 2. Among them, the viscosity of DES with betaine as the hydrogen bond acceptor was significantly greater than that of DES with choline chloride as the hydrogen bond acceptor.

[0039] (3) Accurately weigh 0.25 g of macadamia green peel powder that had passed through a 60-mesh sieve into a 15 mL centrifuge tube, add DES at a solid-liquid ratio of 1:40, and ultrasonicate for 10 min at an ultrasonic power of 250 W and an extraction temperature of 40 °C. The extract was filtered through a 0.45 µm organic filter membrane, and the polyphenol concentration in the extract was determined. The polyphenol yield was calculated, as shown in Table 2. Among them, when the molar ratio of choline chloride to 1,2-butanediol was 1:1, the extraction rate of macadamia green peel polyphenols was the highest, at 88.61 mg GAE / g DW.

[0040] Table 2 Extraction rate of macadamia nut peel polyphenols in 20 DES Example 4: Extraction of macadamia nut green peel polyphenols based on choline chloride and 1,2-butanediol in a molar ratio of 1:1 (1) DES having a molar ratio of choline chloride to 1,2-butanediol of 1:1 was prepared by the DES preparation method in Example 3.

[0041] (2) Accurately weigh 0.25 g of macadamia nut green peel sample that passed through 60 mesh and mix it with DES (water content 20%-60%) in a molar ratio of choline chloride and 1,2-butanediol of 1:1, with a solid-liquid ratio of 1:10-1:50. Ultrasonic extraction was performed in a water bath at 30-70 ℃ with an ultrasonic power of 200-400 W for 5-25 min. The obtained extract was filtered through a 0.45 µm organic filter membrane, the polyphenol concentration in the extract was determined, and the polyphenol yield was calculated.

[0042] (3) Comparative Example 1 Effect of moisture content on DES extraction of macadamia nut peel polyphenols Accurately weigh 0.25 g of macadamia nut green peel sample that passed through 60 mesh, and mix it with choline chloride with a water content of 20%, 30%, 40%, 50%, and 60%, and 1,2-butanediol with a molar ratio of 1: 1 DES, respectively, with a solid-liquid ratio of 1:40, and ultrasonically extract it at 250 W in a 40 ℃ water bath for 10 min. The obtained extract was filtered through a 0.45 µm organic filter membrane, and the polyphenol concentration in the extract was determined. The polyphenol yield was calculated as follows: Figure 7 Among them, the extraction rate was the highest when the water content was 40%, which was 93.89 mg GAE / g DW.

[0043] (4) Comparative Example 2 Effect of solid-liquid ratio on the extraction of macadamia nut peel polyphenols by DES The preparation and extraction methods of DES are the same as those of Comparative Example 1, except that the water content is 30%, the solid-liquid ratio is 1:10, 1:20, 1:30, 1:40, 1:50, as Figure 8 Among them, the extraction rate was the highest when the solid-liquid ratio was 1:40, which was 87.61 mg GAE / gDW.

[0044] (5) Comparative Example 3 Effect of extraction temperature on DES extraction of macadamia nut peel polyphenols The preparation and extraction methods of DES are the same as those of Comparative Example 2, except that the solid-liquid ratio is 1:40 and the extraction temperatures are 30, 40, 50, 60, and 70°C. Fig. 9 Among them, the extraction rate was the highest at 70 ℃, which was 93.03 mg GAE / g DW.

[0045] (6) Comparative Example 4 Effect of extraction time on DES extraction of macadamia nut green peel polyphenols The preparation and extraction methods of DES were the same as those of Comparative Example 3, except that the extraction temperature was 40 °C and the extraction time was 5, 10, 15, 20, and 25 min. Fig.10 Among them, the extraction rate was the highest when the extraction time was 25 min, which was 92.20 mg GAE / g DW.

[0046] (7) Comparative Example 5 Effect of Ultrasonic Power on DES Extraction of Polyphenols from Macadamia Peel The preparation and extraction methods of DES were the same as those of Comparative Example 4, except that the extraction time was 10 min and the ultrasonic power was 200, 250, 300, 350, and 400 W. Fig.11 Among them, the extraction rate was the highest when the ultrasonic power was 300 W, which was 93.04 mg GAE / g DW.

[0047] Example 5: Optimization of DES extraction process for macadamia nut peel polyphenols (1) Based on Comparative Examples 1-5 in Example 4, a three-factor three-level BBD response surface experiment of moisture content, ultrasonic power, and solid-liquid ratio was conducted at an extraction temperature of 40°C and an extraction time of 10 min. The factor level table is shown in Table 3.

[0048] Table 3. BBD response surface experimental factor level table (2) A three-factor three-level BBD response surface experiment was conducted with water content, ultrasonic power, and solid-liquid ratio. The experimental design and results are shown in Table 4, and the variance analysis is shown in Table 5. The quadratic regression equation with polyphenol extraction rate (Y) as the objective function was obtained by fitting with Design Expert software: Y=-330.43672+9.29729×A+0.74734×B+5.72517×C+0.005288×A×B-0.028143×A×C-0.00009×B×C-0.117461×A 2 -0.001687×B 2 -0.052535×C 2 Among them, Y is the polyphenol extraction rate (mg GAE / g DW), A is the water content (%), B is the ultrasonic power (W), and C is the solid-to-solid ratio. From the variance analysis in Table 5, it can be seen that the model P <0.0001, and the lack of fit term is not significant, the model is available; moisture content, ultrasonic power, and solid-liquid ratio have extremely significant effects on polyphenol extraction ( P <0.01). The optimal process conditions for extracting macadamia green peel were obtained from the equation as follows: water content 40.792%, ultrasonic power 284.347W, solid-to-solid ratio 1:43.326, and the predicted value of polyphenol extraction rate under these conditions was 89.427 mg GAE / g DW. After comprehensive consideration, the extraction conditions were set as: water content 40%, ultrasonic power 285W, solid-to-solid ratio 1:43, and a verification experiment was carried out here, and the polyphenol extraction rate of macadamia green peel was obtained to be 94.03 mg GAE / g DW.

[0049] Table 4 Response surface experimental design and results Table 5 Response surface variance analysis (3) Comparative Example 6 Extraction of macadamia nut peel polyphenols using traditional organic solvents Accurately weigh 1.50 g of macadamia nut green peel polyphenol sample that has passed 60 mesh and mix it with 30% ethanol solution at a solid-liquid ratio of 1:40, and ultrasonically extract it for 10 min at an ultrasonic power of 140 W and an ultrasonic temperature of 54 °C. Under these conditions, the extraction rate of macadamia nut green peel polyphenol is 18.23 mg GAE / g DW. (4) The DES extraction rate based on molecular simulation screening is 5.16 times that of traditional organic solvent extraction.

[0050] In summary, the present invention realizes rapid screening of the composition and molar ratio of low eutectic reagents based on molecular simulation, and obtains the optimal process conditions for extracting macadamia nut green peel polyphenols through optimization. This method greatly saves manpower and material resources, reduces the practical application of medicines, and provides a method for extracting macadamia nut green peel polyphenols with simple process, green environmental protection and high extraction efficiency. The optimal process conditions for extracting macadamia nut green peel polyphenols are: a molar ratio of choline chloride and 1,2-butanediol of 1:1, a moisture content of 40%, an ultrasonic power of 285W, a solid-to-material ratio of 1:43, an extraction temperature of 40°C, and an extraction time of 10 min. It is calculated that the extraction rate of macadamia nut green peel polyphenols by the extraction method of the present invention is 94.03 mg GAE / g DW, which is 5.16 times that of the traditional ethanol extraction method.

[0051] The embodiments described above are only representative embodiments of the present invention, and their purpose is to illustrate the technical solution of the present invention, not to limit the scope of implementation of the present invention. Equivalent modifications, replacements or amendments made in accordance with the embodiments are all within the scope of application of the present invention. Please refer to the protection scope in the claims.

Claims

1. A method for extracting macadamia nut green peel polyphenols by screening a deep eutectic solvent based on molecular simulation, characterized in that: Firstly, the composition of macadamia peel polyphenols was quantitatively analyzed. Then, based on the composition of macadamia peel polyphenols, molecular simulation was used to study the dissolution capacity of DES with different hydrogen bond donor / hydrogen bond acceptor compositions on the main polyphenols of macadamia. DES with different hydrogen bond donor / hydrogen bond acceptor compositions and molar ratios were screened. Finally, the screened DES system was optimized. The specific steps include: (1) Identification of the main components of macadamia nut peel polyphenols using UPLC-MSI-QTOF-MS / MS; (2) Through quantum calculation, the molecular models of the main polyphenols, hydrogen bond donors, and hydrogen bond acceptors in the green peel of macadamia nut were established, and geometric optimization and energy optimization were performed; (3) Calculate the relative solubility of the main polyphenols in macadamia nut peel in deep eutectic solvents through molecular simulation, and preliminarily screen the composition and molar ratio of deep eutectic solvents; (4) The composition and molar ratio of the low eutectic solvent preliminarily screened in step (3) were added with 30% water and stirred in a water bath at 80°C for 8 h to prepare a homogeneous, transparent and stable low eutectic solvent, which was mixed with the macadamia nut green peel sample that had passed through a 60-mesh sieve at a solid-liquid ratio of 1:40, and ultrasonically extracted at 250 W in a water bath at 40°C for 10 min to calculate the polyphenol extraction rate and determine the types and molar ratios of hydrogen bond acceptors and hydrogen bond donors; (5) Mix the macadamia nut green peel sample that has passed through a 60-mesh sieve with the low eutectic solvent DES (water content 20%-60%) determined in step (4) at a solid-liquid ratio of 1:10-1:50, perform ultrasonic extraction at 200-400 W ultrasonic power in a 30-70 °C water bath for 5-25 min, filter the obtained extract through a 0.45 µm organic filter membrane, and calculate the polyphenol extraction rate; (6) Response surface experiments were used to determine the optimal extraction conditions for macadamia nut peel polyphenols using low eutectic solvents.

2. The method for extracting macadamia nut green peel polyphenols by screening deep eutectic solvents based on molecular simulation according to claim 1, characterized in that: In step (1), the main component of macadamia nut green peel polyphenols is used as the target component, and the green peel polyphenols at least include 3,4-dihydroxybenzoic acid, p-hydroxybenzoic acid, 3,4-dihydroxybenzaldehyde, gallic acid and vanillic acid.

3. The method for extracting macadamia nut peel polyphenols by screening deep eutectic solvents based on molecular simulation according to claim 1, characterized in that: The hydrogen bond acceptors selected in step (2) include but are not limited to choline chloride, betaine, proline, alanine, and arginine; the hydrogen bond donors include but are not limited to formic acid, acetic acid, propionic acid, lactic acid, levulinic acid, ethylene glycol, glycerol, erythritol, 1,2-butanediol, 1,3-butanediol, urea, methyl urea, and acetamide; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor includes but is not limited to 1:1-1:

4.

4. The method for extracting macadamia nut peel polyphenols by screening deep eutectic solvents based on molecular simulation according to claim 1, characterized in that: In the step (2), the main polyphenols in the green peel of macadamia nut, the hydrogen bond acceptors and hydrogen bond donors are constructed with Chem 3D to export a SFD format file; in the step (3), the molecular structure is structurally optimized and energetically optimized at the BP-TZVPD-FINE level using Turbomole software to export a COSMO format file.

5. The method for extracting macadamia nut green peel polyphenols by screening deep eutectic solvents based on molecular simulation according to claim 1, characterized in that: In the step (4), COSMOtherm software calculates the relative solubility, sets the target component as the solute in MultipleSolvents, and defines the solute as a solid; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:1-1:4; and the relative solubility log(x_RS) is calculated at 25°C.

6. The method for extracting macadamia nut peel polyphenols by screening deep eutectic solvents based on molecular simulation according to claim 1, characterized in that: In the step (5), the low eutectic solvent has a water content of 20%-60%, a solid-liquid ratio of 1:10-1:50, 30-70°C, 200-400 W, and 5-25 min.

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