A hydrophilic transformable ternary eutectic solvent, a preparation method and application thereof

Abstract

The application discloses a hydrophilic convertible ternary eutectic solvent and a preparation method and application thereof, and belongs to the technical field of plant active substance extraction. The hydrophilic convertible ternary eutectic solvent is prepared by taking tetrabutylammonium chloride, dichloroacetic acid and ethylene glycol as raw materials. The eutectic solvent can be used as an extraction reagent to extract polyphenol components in sorghum bran. Compared with traditional extraction reagents, 70% ethanol and 70% methanol, the ternary eutectic solvent greatly improves the yield of polyphenols in sorghum bran.

Description

Technical Field

[0001] This invention belongs to the field of plant active substance extraction technology, and particularly relates to a hydrophilic convertible ternary eutectic solvent, its preparation method and application. Background Technology

[0002] Sorghum is the world's fifth largest food crop, after rice, wheat, corn, and barley. Bran is a component of sorghum and contains various phenolic compounds, flavonoids, and proanthocyanidins; the phenolic content in bran is six times that of the grain. Because sorghum bran contains tannins, an anti-nutritional factor, it not only affects the taste but also reduces the body's utilization of nutrients. Therefore, sorghum bran is often discarded during production, resulting in waste. Promoting the utilization of sorghum bran is therefore of great significance.

[0003] In the extraction of active substances, traditional organic solvents, such as methanol and ethanol, are commonly used as extraction agents. However, the yield of sorghum bran polyphenols extracted using traditional organic solvents is low, and they are highly toxic, have poor biodegradability, low utilization, and large-scale use can cause environmental pollution. How to extract sorghum bran polyphenols efficiently and non-toxically is a technical problem that needs to be solved.

[0004] Eutectic solvents (DES) are a new generation of extraction solvents that can replace traditional extraction solvents. Composed of a halide salt (i.e., hydrogen bond acceptor) and one or two hydrogen bond donors, DES offer advantages such as biodegradability, low toxicity, and low cost, making them excellent solvents for separation, materials science, biocatalysis, and organic synthesis. The hydrogen bonding between the DES donor and acceptor also generates intermolecular forces with the target analyte, thus achieving extraction. Currently, DES is widely used for the extraction of polyphenols, flavonoids, polysaccharides, proteins, and other components from various raw materials. However, traditional DES cannot be reused, resulting in significant waste. Therefore, developing a simple, rapid, and highly efficient recoverable DES as an extractant is of significant practical importance. Summary of the Invention

[0005] To address the problems of low extraction yield, high toxicity, poor biodegradability, potential environmental pollution, and difficulty in recovering extracts from existing extractants, this invention proposes a hydrophilic, convertible ternary eutectic solvent, its preparation method, and its application. This provides a new approach to polyphenol extraction processes.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the objectives of this invention is to provide a hydrophilic, convertible ternary eutectic solvent, which is composed of tetrabutylammonium chloride, dichloroacetic acid and ethylene glycol in a ratio of (4-4.5)g:(2-2.5)g:1mL.

[0008] The second objective of this invention is to provide a method for preparing the hydrophilic convertible ternary eutectic solvent, comprising the following steps: mixing tetrabutylammonium chloride, dichloroacetic acid and ethylene glycol, heating and stirring to obtain a uniform, transparent and clear viscous liquid; mixing the viscous liquid with ultrapure water to obtain the hydrophilic convertible ternary eutectic solvent.

[0009] Furthermore, the amount of ultrapure water added is such that the water content of the resulting hydrophilic convertible ternary eutectic solvent is 0-35% and not 0.

[0010] Furthermore, the heating and stirring are carried out at 45-80°C for 20-50 minutes.

[0011] The third objective of this invention is to provide an application of the aforementioned hydrophilic, convertible ternary eutectic solvent in the extraction of polyphenolic components from plants.

[0012] The fourth objective of this invention is to provide a method for extracting polyphenols from sorghum bran using the aforementioned hydrophilic, convertible ternary eutectic solvent, comprising the following steps:

[0013] The sorghum bran is crushed and sieved to obtain sorghum bran powder;

[0014] The sorghum bran powder was added to the hydrophilic convertible ternary eutectic solvent and ultrasonically treated to obtain an extract.

[0015] The extract was centrifuged, resulting in two phases: an upper aqueous phase containing sorghum bran polyphenols and a lower hydrophobic eutectic solvent phase. The upper aqueous phase was then collected as the sorghum bran polyphenol extract.

[0016] Furthermore, the sieving is performed through an 80-mesh sieve.

[0017] Furthermore, the ratio of the sorghum bran powder to the hydrophilic convertible ternary eutectic solvent is 1 g: (10-50) mL.

[0018] Furthermore, the parameters for the ultrasonic treatment are: power 250W, temperature 20-60℃, and time 20-60min.

[0019] Furthermore, the centrifugation parameters are: rotation speed 3000-5000 rpm, time 5-15 min, and temperature 0 to -12℃.

[0020] Further, ultrapure water is added to the hydrophobic eutectic solvent phase, and the mixture is heated and stirred to convert it into a hydrophilic, convertible ternary eutectic solvent. The amount of water added is such that the resulting eutectic solvent has a water content of 0-35% and is not zero.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] This invention prepares a hydrophilic, convertible ternary eutectic solvent using tetrabutylammonium chloride, dichloroacetic acid, and ethylene glycol in a specific ratio. This eutectic solvent can be used as an extraction reagent to extract polyphenols from sorghum bran. Compared to traditional extraction reagents such as 70% ethanol and 70% methanol, using a ternary eutectic solvent to extract polyphenols from sorghum bran significantly improves the yield of polyphenols. Specific advantages are as follows:

[0023] 1) The eutectic solvent of the present invention significantly improves the yield of sorghum bran polyphenols as an extractant, with yields increased by 2.5 times and 2 times respectively compared to 70% ethanol and 70% methanol;

[0024] 2) The prepared ternary eutectic solvent is a eutectic solvent that can quickly convert its hydrophilicity and hydrophobicity. The hydrophilic eutectic solvent can be converted into a hydrophobic eutectic solvent by low-temperature centrifugation. Then, the hydrophobic eutectic solvent is added to ultrapure water according to a certain solvent water content to obtain a hydrophilic eutectic solvent, thereby realizing the interconversion between hydrophilicity and hydrophobicity.

[0025] 3) This invention provides a method for extracting polyphenols from sorghum bran using a hydrophilic, convertible ternary eutectic solvent. This method can be applied in the field of plant active ingredient extraction technology, and the extraction yield is significantly improved compared to traditional solvents. Simultaneously, the used solvent can be rapidly recycled and reused in new samples by utilizing the temperature-responsive nature of the extraction reagent and its interconversion between hydrophilic and hydrophobic properties. After recycling, the polyphenol extraction yield does not significantly decrease. This technology solves the problem of rapid recycling of extraction reagents, effectively reducing waste and cost, and aligns with the principles of high efficiency and sustainable development.

[0026] This invention employs pulverization and ultrasonic treatment to pretreat sorghum bran, thereby disrupting its structure and making it easier for polyphenols in the sorghum bran to dissolve. When using a hydrophilic ternary eutectic solvent as the extraction reagent, the polyphenol components can be extracted more efficiently.

[0027] The method of this invention is simple and quick to operate, with mild solvent preparation conditions, low cost, high efficiency, environmental protection, and sustainable recycling, which conforms to the concepts of safety, efficiency and sustainable development. Compared with traditional solvents, the extraction efficiency is significantly improved, while the losses from hydrolysis and biodegradation can be effectively reduced. Attached Figure Description

[0028] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0029] Figure 1 The effect of the water content of the eutectic solvent on the yield of sorghum bran polyphenols in Example 1;

[0030] Figure 2 The effect of the material-to-liquid ratio on the yield of sorghum bran polyphenols in Example 2;

[0031] Figure 3 This illustrates the effect of ultrasonic temperature on the yield of sorghum bran polyphenols in Example 3.

[0032] Figure 4 The effect of ultrasonic time on the yield of sorghum bran polyphenols in Example 4;

[0033] Figure 5 The effect of repeated use of the eutectic solvent in Example 5 on the yield of sorghum bran polyphenols. Detailed Implementation

[0034] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0035] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0038] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0039] This invention innovatively establishes a method for extracting polyphenols from sorghum bran using tetrabutylammonium chloride, dichloroacetic acid, and ethylene glycol as extraction reagents. It utilizes a hydrophilic eutectic solvent to extract polyphenols, and then uses the hydrophobicity of the eutectic solvent to separate the polyphenols from the sorghum bran. Furthermore, the extraction reagents can be recovered for further extraction, thus achieving sustainable utilization. This solves the problems of high cost, high consumption, and low yield currently encountered in the industry.

[0040] This invention utilizes tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol as a eutectic solvent to extract polyphenols from sorghum bran, achieving a significantly higher yield than traditional extraction methods. Furthermore, this solvent system has the potential to further improve the yield during the extraction process. Compared to traditional extraction solvents such as 70% ethanol and 70% methanol, the method using a ternary eutectic solvent to extract polyphenols from sorghum bran significantly increases the yield by approximately 2.5 times and 2 times, respectively.

[0041] The ternary eutectic solvent-water system exhibits temperature-responsive characteristics. The critical solution temperature of the tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol-water system is approximately -4°C. At this lower critical solution temperature, the number of hydrogen bonds between the ternary eutectic solvent and water in the aqueous solution is relatively small, resulting in weaker hydrogen bond interactions. Consequently, the interaction force between the ternary eutectic solvent and water decreases, while the internal interaction force within the ternary eutectic solvent increases. Simultaneously, the low temperature makes the intermolecular structure of water more compact, further strengthening the internal interaction force compared to the interaction force between the ternary eutectic solvent and water. Therefore, the ternary eutectic solvent gradually separates from the eutectic solvent-water system, and the volume of the separated supernatant gradually approaches the volume of water within the ternary eutectic solvent-water system. At -4°C, the ternary eutectic solvent aggregates and undergoes a phase transition. Between -4°C and -12°C, the volume of the separated supernatant is approximately equal to the volume of water in the ternary eutectic solvent (tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol)-water system, allowing for easy separation of the ternary eutectic solvent from the aqueous solution. Above 10°C, the number of hydrogen bonds between the ternary eutectic solvent and water in the aqueous solution is relatively high, and the hydrogen bond interactions are strong. Therefore, the interaction force between the ternary eutectic solvent and water increases, while the internal interaction force within the ternary eutectic solvent weakens. The interaction force between the ternary eutectic solvent and water is stronger than the internal interaction force within water. Therefore, above 10°C, the ternary eutectic solvent cannot be separated from the ternary eutectic solvent-water system.

[0042] This invention provides a method for extracting polyphenols from sorghum bran using a hydrophilic, convertible ternary eutectic solvent, comprising the following steps:

[0043] S1. Sample pretreatment: The sorghum bran sample is crushed using a pulverizer and then sieved to obtain sorghum bran powder sample;

[0044] S2. Preparation of ternary eutectic solvent: Tetrabutylammonium chloride, dichloroacetic acid, and ethylene glycol are mixed in a certain proportion (the ratio is (4-4.5)g∶(2-2.5)g∶1mL, preferably 2.35g∶1.28g∶0.55mL), heated and stirred for a certain time to obtain a uniform, transparent, and clear viscous solution. The viscous solution is then fully mixed with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 0-35% and not 0, which is used for extracting polyphenols from sorghum bran.

[0045] S3. Add the processed sorghum bran powder to the prepared ternary eutectic solvent and extract polyphenols using ultrasonic assistance to obtain the extract.

[0046] S4. Centrifuge the above extract to obtain two phases. The upper layer is an aqueous phase containing sorghum bran polyphenols, and the lower layer is a hydrophobic eutectic solvent phase. The upper aqueous phase is the sorghum bran polyphenol extract. The polyphenol yield is measured using a UV spectrophotometer.

[0047] In step S1 of some preferred embodiments of the present invention, the sieving process is performed by filtering with an 80-mesh sieve.

[0048] In step S2 of some preferred embodiments of the present invention, the heating and stirring are carried out at 45-80°C for 20-50 minutes to obtain a uniform, transparent, and clear viscous liquid. A certain amount of ultrapure water is added to the viscous liquid to prepare a ternary eutectic solvent with a water content of 0-35% and not zero, more preferably 30%.

[0049] In step S3 of some preferred embodiments of the present invention, the ultrasonic auxiliary conditions are an ultrasonic power of 250W, an ultrasonic temperature of 20-60℃, and an ultrasonic time of 20-60min; more preferably, the ultrasonic temperature is 30-50℃ and the ultrasonic time is 40min. The ratio of sorghum bran powder to hydrophilic convertible ternary eutectic solvent is 1g:(10-50)mL, preferably 1g:30mL.

[0050] In step S4 of some preferred embodiments of the present invention, the centrifugation conditions are a centrifugation speed of 3000-5000 rpm, a centrifugation time of 5-15 min, and a centrifugation temperature of 0℃ to -12℃; more preferably, the speed is 4000 rpm, the time is 10 min, and the temperature is -4℃. The lower hydrophobic eutectic solvent phase is then added to ultrapure water according to its water content, thus converting it into a hydrophilic eutectic solvent.

[0051] Unless otherwise specified, "room temperature" in this invention refers to 25±2℃.

[0052] All raw materials used in the following embodiments of the present invention are commercially available.

[0053] The following embodiments are further illustrations of the technical solution of the present invention.

[0054] Example 1: Optimization of water content in convertible ternary eutectic solvent

[0055] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0056] S2. Preparation of ternary eutectic solvent: Mix 2.35g tetrabutylammonium chloride, 1.28g dichloroacetic acid, and 0.55mL ethylene glycol and place them in a 50mL beaker. Place a rotor in the beaker and seal it with plastic wrap. Heat the beaker to 45℃ using a magnetic stirrer and stir until a uniform, transparent, and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain ternary eutectic solvents with water contents of 0%, 10%, 20%, 30%, and 35%, respectively.

[0057] S3. Accurately weigh 0.5g of the sieved sorghum bran powder sample and add it to a centrifuge tube. Add it to 10mL of ternary eutectic solvent at a material-to-liquid ratio of 1g:20mL. After sonicating the mixture at 250W power and 40℃ for 30min, centrifuge at 4000rpm for 10min at -4℃. Collect the supernatant to obtain the extract.

[0058] Establishment of the gallic acid standard curve: 0, 100, 200, 300, 400, and 500 μL of 1 mg / mL gallic acid standard solution were respectively placed in 10 mL volumetric flasks. 1.6 mL of distilled water and 2 mL of ferrous tartrate solution were added sequentially, and the mixture was brought to the mark with phosphate buffer solution at pH 7.5. The mixture was shaken several times to ensure thorough mixing. The group without gallic acid standard solution was used as a control. The absorbance was measured at 540 nm. A standard curve was plotted with absorbance value Y as the ordinate and standard gallic acid concentration X (mg / mL) as the abscissa. The regression equation was Y = 19.435X - 0.0209, R0. 2 =0.9988, indicating a good linear correlation.

[0059] Pipette 0.1 mL of the test solution (the extract obtained in step S3) into a 25 mL stoppered colorimetric tube, then add 0.4 mL of ultrapure water, 0.5 mL of ferrous tartrate solution, and 1.5 mL of phosphate buffer solution with pH = 7.5. Cover the tube, shake well, and measure the absorbance at 540 nm. Calculate the polyphenol content according to the regression equation above, and calculate the yield according to the formula for polyphenol yield.

[0060]

[0061] Where C is the polyphenol concentration (mg / mL) obtained from the standard curve; V0 is the volume (mL) of the sample solution after dilution; V1 is the volume (mL) of the initial extract of sorghum bran polyphenols after dilution; V2 is the volume (mL) of the sample solution during measurement; and m is the mass (g) of the sorghum bran polyphenol powder.

[0062] Experimental results are as follows Figure 1As shown, changes in water content can translate into significant differences in physicochemical properties, such as viscosity, solubility, or polarity. The viscosity, polarity, and surface tension of eutectic solvents vary with different proportions of water added, affecting polyphenol yield. Water, acting as a hydrogen bond acceptor (HBA) or hydrogen bond donor (HBD), can disrupt the hydrogen bond network, thereby reducing viscosity and surface tension, which is beneficial for mass transfer. Simultaneously, the addition of water reduces extraction costs and increases the polarity of the extractant, thus promoting the extraction of polar analytes rather than weakly polar analytes. During the experiments, it was found that when the water content was less than 30%, the solution could not separate into an aqueous phase and a hydrophobic eutectic solvent. Only when the water content was between 30% and 35% could the solution separate into two phases, allowing for the recovery and reuse of the lower hydrophobic eutectic solvent layer. Figure 1 As can be seen, the extraction efficiency decreases with increasing water content, possibly due to excessive dilution disrupting the molecular interactions between components and leading to the loss of their solvation properties. The polyphenol yield is higher at a water content of 30% than at 35%. Therefore, a water content of 30% is preferred.

[0063] Example 2: Optimization of the feed-to-liquid ratio of convertible ternary eutectic solvent

[0064] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0065] S2. Preparation of ternary eutectic solvent: Mix 2.35g tetrabutylammonium chloride, 1.28g dichloroacetic acid, and 0.55mL ethylene glycol and place them in a 50mL beaker. Place a rotor in the beaker and seal it with plastic wrap. Heat the beaker to 45℃ using a magnetic stirrer and stir until a uniform, transparent, and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 30%.

[0066] S3. Accurately weigh 0.5g of the sieved sorghum bran powder sample and add it to a centrifuge tube. Add the mixture to a ternary eutectic solvent at material-to-liquid ratios of 1g:10mL, 1g:20mL, 1g:30mL, 1g:40mL, and 1g:50mL, respectively. Sonicate the resulting mixture at 250W power and 40℃ for 30min, then centrifuge at -4℃ and 4000rpm for 10min. Collect the supernatant to obtain the extract. Calculate the polyphenol content using the gallic acid standard curve and calculate the polyphenol yield according to the calculation formula in Example 1.

[0067] Pipette 0.1 mL of the test solution into a 25 mL stoppered colorimetric tube, then add 0.4 mL of ultrapure water, 0.5 mL of ferrous tartrate solution, and 1.5 mL of phosphate buffer solution with pH = 7.5. Cover the tube, shake well, and measure the absorbance at 540 nm. Calculate the yield according to the formula in Example 1.

[0068] Experimental results are as follows Figure 2 As shown. By selecting an appropriate solid-liquid ratio, the diffusion of the solvent in the material can be accelerated, thereby improving the extraction efficiency of the target component and reducing the amount of extractant. Furthermore, an appropriate volume of solvent can absorb sufficient ultrasonic energy to promote cell wall rupture, thus effectively leaching polyphenols. From Figure 2 As can be seen, the yield of polyphenols increases with the increase of the solid-liquid ratio, reaching its highest value at a solid-liquid ratio of 1:30 (g:mL). With further increases in the solid-liquid ratio, the yield begins to decrease, showing an overall trend of first increasing and then decreasing. This is because, on the one hand, when the liquid ratio is relatively small, the high viscosity of the extract affects the cavitation effect of ultrasound, hindering energy transfer and reducing extraction efficiency. On the other hand, excessive liquid leads to powder dispersion and a decrease in the interaction forces between substances, thus reducing extraction efficiency. Therefore, a solid-liquid ratio of 1:30 (g:mL) is preferred.

[0069] Example 3: Optimization of Ultrasonic Extraction Temperature

[0070] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0071] S2. Preparation of ternary eutectic solvent: Mix 2.35g tetrabutylammonium chloride, 1.28g dichloroacetic acid, and 0.55mL ethylene glycol and place them in a 50mL beaker. Place a rotor in the beaker and seal it with plastic wrap. Heat the beaker to 45℃ using a magnetic stirrer and stir until a uniform, transparent, and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 30%.

[0072] S3. Accurately weigh 0.5g of the sieved sorghum bran powder sample and add it to a centrifuge tube. Add it to a ternary eutectic solvent at a material-to-liquid ratio of 1g:30mL. Sonicate the resulting mixture at 250W power and temperatures of 20℃, 30℃, 40℃, 50℃, and 60℃ for 30min. Then centrifuge at -4℃ at 4000rpm for 10min and collect the supernatant to obtain the extract.

[0073] Pipette 0.1 mL of the test solution into a 25 mL stoppered colorimetric tube, then add 0.4 mL of ultrapure water, 0.5 mL of ferrous tartrate solution, and 1.5 mL of phosphate buffer solution with pH = 7.5. Cover the tube, shake well, and measure the absorbance at 540 nm. Calculate the polyphenol content using the gallic acid standard curve, and calculate the yield according to the calculation formula in Example 1.

[0074] Experimental results are as follows Figure 3 As shown in the figure, the yield of polyphenols initially increases with increasing ultrasonic temperature, reaching its highest level at 40℃. With further increases in ultrasonic temperature, the yield of polyphenols decreases, indicating that higher extraction temperature increases the migration rate of DES, while increasing the solubility of the target component in DES. Furthermore, higher solution temperature weakens hydrogen bonding within the cell wall, thereby promoting the dissolution and disruption of the cell wall by DES and improving extraction efficiency. However, excessively high temperatures may degrade some sensitive or unstable substances, leading to a decrease in extraction efficiency. Therefore, an ultrasonic extraction temperature of 40℃ is preferred.

[0075] Example 4: Optimization of Ultrasonic Extraction Time

[0076] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0077] S2. Preparation of ternary eutectic solvent: Mix 2.35g tetrabutylammonium chloride, 1.28g dichloroacetic acid, and 0.55mL ethylene glycol and place them in a 50mL beaker. Place a rotor in the beaker and seal it with plastic wrap. Heat the beaker to 45℃ using a magnetic stirrer and stir until a uniform, transparent, and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 30%.

[0078] S3. Accurately weigh 0.5g of the sieved sorghum bran powder sample and add it to a centrifuge tube. Add it to a ternary eutectic solvent at a material-to-liquid ratio of 1g:30mL. Sonicate the resulting mixture at 250W power and 40℃ for 20min, 30min, 40min, 50min, and 60min respectively. Then centrifuge at -4℃ at 4000rpm for 10min and collect the supernatant to obtain the extract.

[0079] Pipette 0.1 mL of the test solution into a 25 mL stoppered colorimetric tube, then add 0.4 mL of ultrapure water, 0.5 mL of ferrous tartrate solution, and 1.5 mL of phosphate buffer solution with pH = 7.5. Cover the tube, shake well, and measure the absorbance at 540 nm. Calculate the polyphenol content using the gallic acid standard curve, and calculate the yield according to the calculation formula in Example 1.

[0080] Experimental results are as follows Figure 4 As shown, in ultrasound-assisted extraction, ultrasonic cavitation plays a crucial role in improving extraction efficiency and shortening extraction time. From Figure 4 As can be seen, the yield of polyphenols increases with increasing ultrasonic extraction time. This phenomenon may be due to the faster dissolution rate of the target component over time, with the highest polyphenol yield at 40 min. As the ultrasonic extraction time continues, the polyphenol yield decreases, possibly because prolonged ultrasound can damage the active ingredients, leading to a decrease in extraction efficiency. Therefore, a ultrasonic extraction time of 40 min is preferred.

[0081] Example 5: Recovery of the eutectic solvent and subsequent extraction

[0082] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0083] S2. Preparation of ternary eutectic solvent: Mix 2.35g tetrabutylammonium chloride, 1.28g dichloroacetic acid, and 0.55mL ethylene glycol and place them in a 50mL beaker. Place a rotor in the beaker and seal it with plastic wrap. Heat the beaker to 45℃ using a magnetic stirrer and stir until a uniform, transparent, and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 30%.

[0084] S3. Accurately weigh 0.5g of the sieved sorghum bran powder sample and add it to a centrifuge tube. Add it to a ternary eutectic solvent at a material-to-liquid ratio of 1g:30mL. After sonicating the mixture at 250W power and 40℃ for 40min, centrifuge at 4000rpm for 10min at -4℃. Collect the supernatant to obtain the extract. Calculate the polyphenol content using the gallic acid standard curve (recorded as 0 cycles).

[0085] The yield of sorghum bran polyphenols was calculated according to the formula in Example 1, and the yield of sorghum bran polyphenols was 22.154 mg / g.

[0086] After the two phases separate during centrifugation, the lower layer of hydrophobic eutectic solvent is added to ultrapure water at a water content of 30%, and then magnetically stirred and heated to make it a homogeneous, stable, and transparent liquid. At this point, the hydrophobic eutectic solvent is converted into a hydrophilic eutectic solvent, which is used to extract new sorghum bran samples. The above operation steps are repeated to extract new sorghum bran samples (referred to as 1, 2, 3, 4, 5, and 6 cycles, respectively).

[0087] Experimental results are as follows Figure 5As shown in the figure (the percentage on each bar represents the percentage change in polyphenol yield compared to cycle 0; that is, if the polyphenol yield is 100% after cycle 0, then after one cycle, the polyphenol yield will decrease to 87% compared to cycle 0, and so on). This embodiment investigated the effect of recycling the eutectic solvent on the polyphenol yield of sorghum bran. The results showed that the polyphenol yield of sorghum bran did not decrease significantly with the increase in the number of times the eutectic solvent was reused. This indicates that the tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol selected in this invention has good reusability as a convertible eutectic solvent.

[0088] Comparative Example 1

[0089] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0090] S2. Mix the sorghum bran powder sample with 70% ethanol (volume concentration) at a material-to-liquid ratio of 1g:30mL. After sonicating the mixture at 250W power and 40℃ for 40min, centrifuge at -4℃ at 4000rpm for 10min and collect the supernatant to obtain the extract. Calculate the polyphenol content using the gallic acid standard curve.

[0091] The polyphenol yield was calculated according to the formula in Example 1. The results showed that, compared with traditional ethanol extraction, the yield of sorghum bran polyphenols extracted with a ternary eutectic solvent was significantly increased by 2.5 times.

[0092] Comparative Example 2

[0093] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0094] S2. Mix the sorghum bran powder sample with 70% methanol (volume concentration) at a material-to-liquid ratio of 1g:30mL. After sonicating the mixture at 250W power and 40℃ for 40min, centrifuge at -4℃ at 4000rpm for 10min and collect the supernatant to obtain the extract. Calculate the polyphenol content using the gallic acid standard curve.

[0095] The polyphenol yield was calculated according to the formula in Example 1. The results showed that, compared with traditional methanol extraction, the yield of sorghum bran polyphenols extracted with a ternary eutectic solvent was significantly increased by 2 times.

[0096] Therefore, it can be seen that the yield of sorghum bran polyphenols obtained by the technical method used in this invention is significantly higher than that of traditional techniques.

[0097] Comparative Example 3

[0098] S1. Sample pretreatment: Dry the sorghum bran sample, crush it with a pulverizer, and then pass it through an 80-mesh sieve to obtain sorghum bran powder sample;

[0099] S2. The sorghum bran powder sample was thoroughly mixed with 16 kinds of eutectic solvents (DES), such as choline chloride-glucose and choline chloride-malonic acid, at a material-liquid ratio of 1g:30mL. See the table below for details. The resulting mixture was sonicated at 250W power and 40℃ for 40min, and then centrifuged at 4000rpm for 10min at -4℃. The supernatant was collected to obtain the extract. The polyphenol content was calculated using the gallic acid standard curve.

[0100] The polyphenol yield was calculated according to the formula in Example 1, and the yield of sorghum bran polyphenols is shown in the table below:

[0101] Table 1 Effect of different DES on polyphenol yield

[0102]

[0103]

[0104] Therefore, it can be seen that the ternary eutectic solvent (tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol) used in this invention has a significantly higher yield of polyphenols extracted from sorghum bran than other eutectic solvents.

[0105] Comparative Example 4

[0106] Same as Example 5, except that in step S2, the preparation of the ternary eutectic solvent is as follows: First, adjust the ratio of tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol to 8.5g:2g:1mL, mix them and place them in a 50mL beaker, put in a rotor and seal it with plastic wrap, heat it to 45°C using a magnetic stirrer, and stir until a uniform, transparent and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 30%.

[0107] The yield of sorghum bran polyphenols was calculated according to the formula in Example 1, and the yield of sorghum bran polyphenols was 16.849 mg / g.

[0108] Comparative Example 5

[0109] Same as Example 5, except that in step S2, the preparation of the ternary eutectic solvent is as follows: First, adjust the ratio of tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol to 4g:4g:1mL, mix them and place them in a 50mL beaker, put in a rotor and seal it with plastic wrap, heat it to 45°C using a magnetic stirrer, and stir until a uniform, transparent and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 30%.

[0110] The yield of sorghum bran polyphenols was calculated according to the formula in Example 1, and the yield of sorghum bran polyphenols was 18.216 mg / g.

[0111] Comparative Example 6

[0112] Similar to Example 5, the difference lies in the preparation of the ternary eutectic solvent in step S2: First, adjust the ratio of tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol to 2g∶1g∶1mL, mix and place in a 50mL beaker, put in a rotor and seal with plastic wrap, heat to 45°C using a magnetic stirrer, and stir until a uniform, transparent and clear viscous solution is obtained. Mix the viscous solution with ultrapure water in a certain proportion to obtain a ternary eutectic solvent with a water content of 30%.

[0113] The yield of sorghum bran polyphenols was calculated according to the formula in Example 1, and the yield of sorghum bran polyphenols was found to be 15.884 mg / g.

[0114] Therefore, it can be seen that the yield of sorghum bran polyphenols obtained by using the amount of tetrabutylammonium chloride-dichloroacetic acid-ethylene glycol in the technical method adopted in this invention is significantly higher than that of Comparative Examples 4, 5 and 6.

[0115] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for extracting polyphenols from sorghum bran using a hydrophilic, convertible ternary eutectic solvent, characterized in that, Includes the following steps: The sorghum bran is crushed and sieved to obtain sorghum bran powder; The sorghum bran powder was added to a hydrophilic convertible ternary eutectic solvent and ultrasonically treated to obtain an extract. The extract was centrifuged, resulting in two phases: an upper aqueous phase containing sorghum bran polyphenols and a lower hydrophobic eutectic solvent phase. The upper aqueous phase was then collected as the sorghum bran polyphenol extract. The temperature for centrifugation is 0℃ to -12℃; The hydrophilic convertible ternary eutectic solvent is composed of tetrabutylammonium chloride, dichloroacetic acid and ethylene glycol in a ratio of (4-4.5) g: (2-2.5) g: 1 mL; The preparation method of the hydrophilic convertible ternary eutectic solvent includes the following steps: mixing tetrabutylammonium chloride, dichloroacetic acid and ethylene glycol, heating and stirring to obtain a uniform, transparent and clear viscous liquid; mixing the viscous liquid with ultrapure water to obtain the hydrophilic convertible ternary eutectic solvent; the water content of the hydrophilic convertible ternary eutectic solvent is 0-35% and not 0.

2. The method according to claim 1, characterized in that, The ratio of the amount of sorghum bran powder to the amount of the hydrophilic convertible ternary eutectic solvent is 1 g : (10-50) mL.

3. The method according to claim 1, characterized in that, The parameters for the ultrasonic treatment are: power 250W, temperature 20-60℃, and time 20-60min.

4. The method according to claim 1, characterized in that, The centrifugation parameters are: rotation speed 3000-5000 rpm, time 5-15 min.

5. The method according to claim 1, characterized in that, When ultrapure water is added to the hydrophobic eutectic solvent phase and the mixture is heated and stirred, it is transformed into a hydrophilic convertible ternary eutectic solvent.

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