Method for extracting stevioside in stevia rebaudiana by using natural eutectic solvent

Abstract

The invention discloses a method for extracting stevioside in stevia rebaudiana by using a natural eutectic solvent, and belongs to the technical field of natural product extraction. The method comprises the following steps: crushing dried stevia rebaudiana leaves to obtain stevia rebaudiana powder; performing extraction treatment on the stevia rebaudiana powder by adopting an aqueous solution of a natural eutectic solvent, then standing, filtering and collecting filtrate; and concentrating the filtrate, loading the concentrated filtrate to macroporous adsorption resin, eluting, and drying to obtain the stevioside. According to the method, the natural eutectic solvent which is green, environment-friendly, low in cost and high in designability is used as the extracting agent, the use of a traditional solvent is reduced, operation is easy, consumed time is short, the method has high extraction efficiency, and the technical problems that an existing stevioside extraction process is complex, and the product purity is low are effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of natural product extraction and separation technology, specifically relating to a method for extracting steviol glycosides from stevia using a natural eutectic solvent. Background Technology

[0002] Stevia is a branching shrub belonging to the Asteraceae family, native to northeastern Paraguay. It is now also cultivated in Xinjiang, Anhui, Shandong, and other regions of China. Its leaves are rich in bioactive compounds such as steviol glycosides (SGs), protein, cellulose, amino acids, lipids, carotenoids, and ascorbic acid. SGs are tetracyclic diterpenoids naturally found in stevia, comprising approximately 14% of the dried leaves. The contents of each component in SGs are as follows: Rebaudioside A (RA) accounts for about 50-60%, and its sweetness is about 350-450 times that of sucrose; Stevioside (STV) accounts for about 20-30%, and its sweetness is 200-300 times that of sucrose; Rebaudioside C (RC) accounts for about 1%, and its sweetness is about 120-500 times that of sucrose; while the contents of other components such as Rebaudioside B (RB), Rebaudioside D (RD), Rebaudioside E (RE), Rebaudioside F (RF), Dulcoside A (DA), and Rubusoside (Rub) are all in small amounts.

[0003] Because stevia glycosides (SGs) possess natural high sweetness and physiological benefits without affecting the viscosity and gelling properties of food, they are widely used in the beverage and food industries in some regions as a healthy and natural alternative to sucrose and aspartame. In December 2008, the U.S. Food and Drug Administration (FDA) declared that high-purity RA purified from stevia could be considered safe. In 2010, the European Food Safety Authority (EFSA) assessed the safety of steviol glycosides and established acceptable daily intakes (ADIs). Traditional sucrose is high in calories, and excessive consumption can lead to serious health problems such as obesity and elevated blood sugar. Therefore, SGs, as natural, zero-calorie, and safe sweeteners, are increasingly popular as a substitute for sucrose. While satisfying the need for sweetness, they also possess anti-inflammatory, anti-obesity, anti-diabetic, blood pressure-lowering, anti-caries, and anti-cancer properties, and are widely used in the brewing, beverage, chemical, and pharmaceutical industries.

[0004] Steviosides are readily soluble in water and alcohol solvents, therefore, water or ethanol-water solutions are generally chosen as solvents for extracting steviol glycosides from stevia. Existing extraction techniques for steviol glycosides include solvent extraction, ultrasonic or microwave-assisted solvent extraction, and supercritical fluid extraction. Liu et al. (Food and Bioproducts Processing, 2010, 88, 215–221) used ultrasonic-assisted extraction with water as the solvent to extract steviol glycosides from stevia leaves at an extraction temperature of 68 ℃, a power of 60 W, and an extraction time of 32 min, with a yield of 169.0 ± 1.7 mg / g. Carbonell-Capella et al. (Journal of Food Processing and Preservation, 2017, 41(5), e13179) used microwave-assisted extraction with water as the solvent to extract steviol glycosides from stevia leaves, achieving the highest yields at 400 W, 50 ℃, and 1.2 min, yielding 48.0 mg / g of steviol glycosides (STV) and 23.0 mg / g of steviol glycosides (RA). Erkucuk et al. (The Journal of Supercritical Fluids, 2009, 51(1), 29–35) used supercritical fluid extraction (SFI) with CO2 + 70% ethanol (v / v) as the extraction solvent. Under conditions of 21.1 MPa, 80℃, and 60 minutes, the STV yield was 36.66 mg / g and the RA yield was 17.79 mg / g. However, ultrasonic, microwave-assisted, and supercritical fluid extraction methods require sophisticated equipment, resulting in high equipment investment costs and high energy consumption. Therefore, most companies use traditional solvent extraction methods to produce steviol glycosides. However, traditional solvent extraction suffers from low efficiency and high solvent and time consumption.

[0005] Currently, in response to the shortcomings of traditional solvent extraction, there is an urgent need to develop a green, efficient, low-cost extraction technology suitable for large-scale industrial production to meet the ever-increasing demand for steviol glycosides. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for extracting steviol glycosides from stevia using a natural eutectic solvent, so as to solve the technical problems of high solvent consumption, long extraction time and low extraction efficiency in the prior art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a method for extracting steviol glycosides from stevia using a natural eutectic solvent, characterized by comprising the following steps: 1) Crush the dried stevia leaves to obtain stevia powder; 2) Stevia powder was extracted using an aqueous solution of a natural eutectic solvent, then filtered and the filtrate was collected; 3) After concentrating the filtrate, the sample was loaded onto a macroporous adsorption resin, eluted, and then dried to obtain steviol glycosides.

[0008] Preferably, the natural eutectic solvent is a mixture of hydrogen bond donors and hydrogen bond acceptors; both the hydrogen bond donors and hydrogen bond acceptors are natural components.

[0009] More preferably, the hydrogen bond donor is one of ethylene glycol, glycerol, urea, lactic acid, oxalic acid, malonic acid, malic acid, propionic acid, maleic acid, levulinic acid, ascorbic acid, glutamic acid, tartaric acid, aconitic acid, citric acid, caffeic acid, erythritol, ribitol, sorbitol, L-rhamnose, D-mannose, galactose, xylose, glucose, sucrose, maltose, L-sorbose, trehalose, and raffinose.

[0010] More preferably, the hydrogen bond acceptor is one of choline chloride, betaine, ammonium acetate, alanine, glycine, proline, arginine, L-carnitine, glucose, maltose, xylose, and glycerol.

[0011] More preferably, the molar ratio of hydrogen bond donors to hydrogen bond acceptors in the natural eutectic solvent is between 2:1 and 1:2.

[0012] Preferably, the natural eutectic solvent accounts for 30% to 95% of the total mass of the aqueous solution of the natural eutectic solvent.

[0013] Preferably, in step 2), the ratio of stevia powder to the aqueous solution of natural eutectic solvent is 1:5 to 1:40, the temperature during the extraction process is 20 to 90°C, and the extraction time is 30 to 150 min.

[0014] Preferably, in step 3), the natural eutectic solvent is first washed off with distilled water, then impurities are washed off with ethanol solution, and then steviol glycosides are washed off with eluent. The eluent is collected and steviol glycosides are obtained by rotary evaporation.

[0015] More preferably, impurities are washed away with a 10% to 40% ethanol solution, and steviol glycosides are eluted with a 20% to 100% ethanol solution.

[0016] Preferably, the macroporous adsorption resin is one of D101, AB-8, X-5 and NKA-9.

[0017] During elution, first wash away the eutectic solvent with distilled water, then wash away impurities with 10%-40% ethanol solution, and then elute the stevia polysaccharide with 20%-100% ethanol solution. Remove the eluent by rotary evaporation, and place the solid in a drying oven to dry to constant weight.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for extracting steviol glycosides from stevia using a natural eutectic solvent. It employs an innovative combined approach of a natural eutectic solvent and macroporous adsorption resin, achieving a technological breakthrough through synergistic effects. Firstly, using an aqueous solution of a natural eutectic solvent instead of traditional solvents to extract steviol glycosides from stevia significantly increases its solubility. The solubility of steviol glycosides in eutectic solvents is typically 2-5 times that in pure water, allowing for efficient dissolution with a small amount of solvent, thus effectively reducing solvent consumption. Secondly, considering that polysaccharides have higher solubility in water, and while many other polysaccharides are insoluble in ethanol, steviol glycosides have some solubility in ethanol, but even higher solubility in water, and even higher solubility in eutectic solvents. This effectively solves the problem of long extraction times. On the other hand, co-using with macroporous adsorption resins is key to solving the problem of low purification efficiency. While extraction with only a eutectic solvent aqueous solution can improve dissolution efficiency, subsequent separation still requires a large amount of solvent (such as organic solvent elution). The addition of macroporous adsorption resins enables selective adsorption purification, avoiding the repeated solvent concentration and extraction steps in traditional processes, thus reducing secondary solvent consumption. Simultaneously, elution difficulty is reduced; the co-use of eutectic solvents and macroporous adsorption resins only requires a low-concentration ethanol solution to complete elution, further reducing total solvent consumption. Therefore, macroporous adsorption resin separation achieves the separation of steviol glycosides from natural eutectic solvents, allowing the eutectic solvents to be recovered and reused, reducing production costs. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] Example 1 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 10 mL of a 45 wt% betaine:propionic acid (pre-formed in a 1:2 molar ratio) aqueous solution, soak at 70°C for 2 hours, filter, and collect the filtrate.

[0022] Step 2, Adsorption and Elution: Load the filtrate onto an AB-8 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 15 mL of 30% ethanol solution, and finally elute with 20 mL of 70% ethanol solution.

[0023] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 149.5 mg, with a purity of 86.71%.

[0024] Example 2 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 20 mL of a 45 wt% betaine: ethylene glycol (pre-formed in a 1:2 molar ratio) aqueous solution, soak at 80°C for 1 hour, filter, and collect the filtrate.

[0025] Step 2, Adsorption and Elution: Load the filtrate onto a D101 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 15 mL of 20% ethanol solution, and finally elute with 20 mL of 60% ethanol solution.

[0026] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 129.83 mg, with a purity of 81.23%.

[0027] Example 3 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 30 mL of a 45 wt% betaine:urea (pre-formed in a 1:2 molar ratio) aqueous solution, soak at 50°C for 150 minutes, filter, and collect the filtrate.

[0028] Step 2, Adsorption and Elution: Load the filtrate onto an X-5 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 10 mL of 20% ethanol solution, and finally elute with 20 mL of 80% ethanol solution.

[0029] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, and dry it to obtain 110.31 mg with a purity of 79.24%.

[0030] Example 4 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 40 mL of a 45 wt% aqueous solution of betaine: levulinic acid (pre-formed in a 1:2 molar ratio), soak at 70°C for 2 hours, filter, and collect the filtrate.

[0031] Step 2, Adsorption and Elution: Load the filtrate onto a NAK-9 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 20 mL of 25% ethanol solution, and finally elute with 20 mL of 80% ethanol solution.

[0032] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 130.38 mg, with a purity of 84.35%.

[0033] Example 5 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 10 mL of 45 wt% L-carnitine:propionic acid (pre-formed in a 1:2 molar ratio) aqueous solution, soak at 60°C for 2 hours, filter, and collect the filtrate.

[0034] Step 2, Adsorption and Elution: Load the filtrate onto an AB-8 resin adsorption column. First, wash away the eutectic solvent with 10 mL of distilled water (to be recovered and reused), then wash away impurities with 10 mL of 20% ethanol solution, and finally elute with 20 mL of 70% ethanol solution.

[0035] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 137.05 mg, with a purity of 85.99%.

[0036] Example 6 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 30 mL of 45 wt% L-carnitine: ethylene glycol (pre-formed in a 1:2 molar ratio), soak at 75°C for 2 hours, filter, and collect the filtrate.

[0037] Step 2, Adsorption and Elution: Load the filtrate onto a D101 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 20 mL of 35% ethanol solution, and finally elute with 20 mL of 50% ethanol solution.

[0038] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 99.51 mg, with a purity of 80.98%.

[0039] Example 7 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 30 mL of a 45 wt% L-carnitine:urea (pre-formed in a 1:2 molar ratio) aqueous solution, soak at 55°C for 30 minutes, filter, and collect the filtrate.

[0040] Step 2, Adsorption and Elution: Load the filtrate onto an X-5 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 20 mL of 30% ethanol solution, and finally elute with 20 mL of 60% ethanol solution.

[0041] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 120.68 mg, with a purity of 79.66%.

[0042] Example 8 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 15 mL of a 45 wt% L-carnitine: levulinic acid (pre-formed in a 1:2 molar ratio) aqueous solution (1:2 + 45 wt%), soak at 70℃ for 50 minutes, filter, and collect the filtrate.

[0043] Step 2, Adsorption and Elution: Load the filtrate onto a NAK-9 resin adsorption column. First, wash away the eutectic solvent with 10 mL of distilled water (to be recovered and reused), then wash away impurities with 10 mL of 20% ethanol solution, and finally elute with 20 mL of 75% ethanol solution.

[0044] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 134.37 mg, with a purity of 83.67%.

[0045] Example 9 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 20 mL of 45 wt% aqueous solution of choline chloride: ethylene glycol (pre-formed in a 1:2 molar ratio), soak at 75°C for 2 hours, filter, and collect the filtrate.

[0046] Step 2, Adsorption and Elution: Load the filtrate onto an AB-8 resin adsorption column. First, wash away the eutectic solvent with 15 mL of distilled water (to be recovered and reused), then wash away impurities with 15 mL of 30% ethanol solution, and finally elute with 20 mL of 70% ethanol solution.

[0047] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 135.18 mg, with a purity of 85.96%.

[0048] Example 10 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 10 mL of a 45 wt% aqueous solution of choline chloride and urea (pre-formed in a 1:2 molar ratio), soak at 75°C for 1 hour, filter, and collect the filtrate.

[0049] Step 2, Adsorption and Elution: Load the filtrate onto an X-5 resin adsorption column. First, wash away the eutectic solvent with 10 mL of distilled water (to be recovered and reused), then wash away impurities with 10 mL of 25% ethanol solution, and finally elute with 15 mL of 70% ethanol solution.

[0050] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 107.85 mg, with a purity of 79.24%.

[0051] Example 11 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 25 mL of a 45 wt% proline:oxalic acid (pre-formed in a 1:1 molar ratio) aqueous solution, soak at 70°C for 150 minutes, filter, and collect the filtrate.

[0052] Step 2, Adsorption and Elution: Load the filtrate onto a D101 resin adsorption column. First, wash away the eutectic solvent with 10 mL of distilled water (to be recovered and reused), then wash away impurities with 20 mL of 30% ethanol solution, and finally elute with 20 mL of 70% ethanol solution.

[0053] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 96.04 mg, with a purity of 80.79%.

[0054] Example 12 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 20 ml of a 45 wt% proline:tartaric acid (pre-formed in a 1:1 molar ratio) aqueous solution (1:1 + 45 wt%), soak at 75°C for 2 hours, filter, and collect the filtrate.

[0055] Step 2, Adsorption and Elution: Load the filtrate onto an AB-8 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 20 mL of 15% ethanol solution, and finally elute with 20 mL of 75% ethanol solution.

[0056] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, and dry it to obtain 118.46 mg with a purity of 85.51%.

[0057] Example 13 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 30 mL of a 45 wt% proline:citric acid (pre-formed in a 1:1 molar ratio) aqueous solution, soak at 70°C for 2 hours, filter, and collect the filtrate.

[0058] Step 2, Adsorption and Elution: Load the filtrate onto a D101 resin adsorption column. First, wash away the eutectic solvent with 20 mL of distilled water (to be recovered and reused), then wash away impurities with 20 mL of 20% ethanol solution, and finally elute with 30 mL of 70% ethanol solution.

[0059] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 106.04 mg, with a purity of 81.05%.

[0060] Example 14 A method for extracting steviol glycosides from stevia using a natural eutectic solvent includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 15 mL of a 45 wt% aqueous solution of choline chloride and citric acid (pre-formed in a 1:2 molar ratio), soak at 75°C for 2 hours, filter, and collect the filtrate.

[0061] Step 2, Adsorption and Elution: Load the filtrate onto an X-5 resin adsorption column. First, wash away the eutectic solvent with 10 mL of distilled water (to be recovered and reused), then wash away impurities with 10 mL of 30% ethanol solution, and finally elute with 15 mL of 60% ethanol solution.

[0062] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 99.34 mg, with a purity of 78.93%.

[0063] Comparative Example 1 A method for extracting steviol glycosides from stevia includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 30 mL of pure water, soak at 70℃ for 2 hours, filter, and collect the filtrate.

[0064] Step 2, Adsorption and Elution: Load the filtrate onto an AB-8 resin adsorption column, wash away impurities with 10 mL of 30% ethanol solution, and finally elute with 20 mL of 70% ethanol solution.

[0065] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 113.28 mg, with a purity of 71.03%.

[0066] The results show that the purity of the steviol glycosides extracted by the method of the present invention is higher than that of the method in Comparative Example 1.

[0067] Comparative Example 2 A method for extracting steviol glycosides from stevia includes the following steps: Step 1, Extraction: Add 1 g of stevia powder to the extraction vessel, add 30 mL of 70% ethanol aqueous solution, soak at 70℃ for 2 hours, filter, and collect the filtrate.

[0068] Step 2, Adsorption and Elution: Load the filtrate onto an AB-8 resin adsorption column, wash away impurities with 10 mL of 30% ethanol solution, and finally elute with 20 mL of 70% ethanol solution.

[0069] Step 3, concentration and drying: Collect the eluent, rotary evaporate the eluent to obtain steviol glycoside solid powder, dry to obtain 108.90 mg, with a purity of 70.35%.

[0070] The results show that the purity of the steviol glycosides extracted by the method of the present invention is higher than that of the method in Comparative Example 2.

[0071] Yields were calculated based on the results of the above embodiments and comparative examples. The calculation process is as follows: Yield (extraction yield) = Mass of pure steviol glycosides actually extracted / Mass of total steviol glycosides in stevia raw material × 100%.

[0072] Note: The stevioside content in commonly used stevia powder is about 10%-18%, and this calculation is based on 14% (a commonly used intermediate value).

[0073] Total steviol glycosides mass in stevia raw material: Raw material dosage: 1 g = 1000 mg; assuming the mass fraction of steviol glycosides in the raw material is 14%. The total steviol glycoside mass is: raw material mass × steviol glycoside mass fraction in raw material = 1000 mg × 14% = 140 mg.

[0074] Taking Example 1 as an example The actual mass of pure steviol glycosides extracted: The mass of the dried solid powder is known to be 149.5 mg, and the purity is 86.71%.

[0075] Mass of pure steviol glycosides = Mass of solid powder × Purity = 149.5 mg × 86.71% ≈ 129.63 mg The calculated yield is: 129.63 mg / 140 mg × 100% = 92.59%.

[0076] Other embodiments were calculated according to the above method, and the results are shown in Table 1. Table 1 records the yield and purity results of all embodiments.

[0077] Table 1

[0078] As can be seen, compared with the comparative example, the purity of all embodiments of this application is significantly higher than that of the comparative example. Only a few embodiments (Example 11) have a relatively lower yield than the comparative example 1, but the purity is relatively high. This shows that the method of this application can effectively solve the problems of complex extraction process and low product purity of existing steviol glycosides, and has high extraction efficiency.

[0079] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for extracting steviol glycosides from stevia using a natural eutectic solvent, characterized in that, Includes the following steps: 1) Crush the dried stevia leaves to obtain stevia powder; 2) Stevia powder was extracted using an aqueous solution of a natural eutectic solvent, then filtered and the filtrate was collected; 3) After concentrating the filtrate, the sample was loaded onto a macroporous adsorption resin, eluted, and then dried to obtain steviol glycosides.

2. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 1, characterized in that, The natural eutectic solvent is a mixture of hydrogen bond donors and hydrogen bond acceptors; both the hydrogen bond donors and hydrogen bond acceptors are made from natural components.

3. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 2, characterized in that, The hydrogen bond donor is one of the following: ethylene glycol, glycerol, urea, lactic acid, oxalic acid, malonic acid, malic acid, propionic acid, maleic acid, levulinic acid, ascorbic acid, glutamic acid, tartaric acid, aconitic acid, citric acid, caffeic acid, erythritol, ribitol, sorbitol, L-rhamnose, D-mannose, galactose, xylose, glucose, sucrose, maltose, L-sorbose, trehalose, and raffinose.

4. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 2, characterized in that, The hydrogen bond acceptor is one of choline chloride, betaine, ammonium acetate, alanine, glycine, proline, arginine, L-carnitine, glucose, maltose, xylose, and glycerol.

5. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 2, characterized in that, The molar ratio of hydrogen bond donors to hydrogen bond acceptors in the natural eutectic solvent is between 2:1 and 1:

2.

6. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 1, characterized in that, The natural eutectic solvent accounts for 30% to 95% of the total mass of the aqueous solution of the natural eutectic solvent.

7. A method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 1, characterized in that, In step 2), the ratio of stevia powder to the aqueous solution of natural eutectic solvent is 1:5 to 1:40, the temperature during the extraction process is 20 to 90°C, and the extraction time is 30 to 150 min.

8. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 1, characterized in that, In step 3), the natural eutectic solvent is first washed with distilled water, then impurities are washed away with ethanol solution, and then steviol glycosides are washed away with eluent. The eluent is collected and steviol glycosides are obtained by rotary evaporation.

9. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 8, characterized in that, Impurities were washed away with 10%–40% ethanol solution, and steviol glycosides were eluted with 20%–100% ethanol solution.

10. The method for extracting steviol glycosides from stevia using a natural eutectic solvent according to claim 1, characterized in that, The macroporous adsorption resin is one of D101, AB-8, X-5 and NKA-9.

Images