A method for extracting tea polyphenols by using N-methyl pyrrolidone

Abstract

The present application relates to a kind of methods for extracting tea polyphenols using N-methyl pyrrolidone.The steps include: adding tea leaves to N-methyl pyrrolidone, mixing evenly, then extracting at 40-90°C for 30-180 min, followed by centrifugation at 4500-5500 r / min for 2-8 min, and obtaining tea polyphenol extract after filtration; the tea polyphenol extraction rate of the obtained tea polyphenol extract is determined by the ferrous tartrate colorimetric method.The present application first uses N-methyl pyrrolidone as an organic solvent for tea polyphenol extraction, effectively utilizes the good solubilizing effect of N-methyl pyrrolidone on poorly soluble drugs, and greatly improves the extraction rate of tea polyphenols.Furthermore, experiments have confirmed that compared with the conventional ethanol extraction method using an organic solvent, the extraction rate of tea polyphenols using the method provided by the present application is increased by 15.61-15.84%.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for extracting tea polyphenols using N-methyl pyrrolidone, belonging to the technical field of natural product extraction. BACKGROUND

[0002] Natural products as raw materials, using physical and chemical methods to extract effective ingredients can be used as cosmetic additives and dietary supplements, which can improve health, delay aging, prevent chronic diseases, prolong life and support the structure and function of the body. There are many methods for extracting natural organic compounds, such as Soxhlet extraction, soaking method and steam distillation method, and various solvents are selected, including water, ethanol, acetone, acetic acid, chloroform, dichloromethane, diethyl ether, ethanol and hexane, etc.

[0003] For example, in addition to containing rich vitamins, amino acids and minerals needed by humans, tea also contains tea polyphenols, tea pigments, quinones, flavonoids and other substances. Among them, tea polyphenols are a complex of polyhydroxy phenolic compounds in tea, and the main component is catechin and its derivatives, which are the main components of tea with health functions. Studies have shown that tea polyphenols have antioxidant, antibacterial, antitumor, anti-radiation and other effects, and also have the functions of lowering blood lipids and inhibiting cardiovascular diseases, and can be used in food field and daily chemical industry. Therefore, tea polyphenols have wide application and broad application prospect.

[0004] Nowadays, there are many methods for extracting polyphenols from tea, such as solvent extraction, ultrasonic extraction, microwave extraction, enzyme extraction and so on. The most important method is still solvent extraction, which uses ethanol to extract tea polyphenols from tea. However, for large tea polyphenols, the extraction rate is low when using water and ethanol as the extraction liquid, and ethanol is not suitable in some cases, so it is necessary to seek new alternative solvents.

[0005] Nitrogen-containing organic solvents such as N-methyl pyrrolidone have strong affinity with various effective components in natural products, which can greatly improve the extraction rate of effective components in natural products. Moreover, N-methyl pyrrolidone also has good solubilizing effect on poorly soluble drugs, and is an excellent solubilizer. At the same time, N-methyl pyrrolidone has been included in the list of commonly used solvents in the published "List of Cosmetics Ingredients in Use (2021 Edition)", so it can be used with confidence. However, there is currently a lack of methods for preparing natural product extraction liquid using such solvents, especially a lack of research on using such solvents to prepare tea polyphenols. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a method for extracting tea polyphenols using N-methyl pyrrolidone.

[0007] The technical solution of the present application is as follows:

[0008] A method for extracting tea polyphenols by using N-methyl pyrrolidone, comprising the following steps:

[0009] The tea leaves are added into N-methyl pyrrolidone, and after being mixed uniformly, the tea leaves are extracted at 40-90°C for 30-180 min, and then centrifuged at 4500-5500 r / min for 2-8 min, and after being filtered, tea polyphenol extract is obtained; the tea polyphenol extraction rate of the obtained tea polyphenol extract is determined by using the ferrous tartrate colorimetric method.

[0010] According to the application, preferably, the tea leaves are white tea or green tea.

[0011] According to the application, preferably, the mass-volume ratio of the tea leaves and N-methyl pyrrolidone is 1:(20-60), unit: g / mL.

[0012] Further preferably, the mass-volume ratio of the tea leaves and N-methyl pyrrolidone is 1:(25-45), unit: g / mL.

[0013] Most preferably, the mass-volume ratio of the tea leaves and N-methyl pyrrolidone is 1:(30-40), unit: g / mL.

[0014] According to the application, preferably, the extraction temperature is 75-90°C.

[0015] Most preferably, the extraction temperature is 80-85°C.

[0016] According to the application, preferably, the extraction time is 85-125 min.

[0017] Most preferably, the extraction time is 90-120 min.

[0018] According to the application, preferably, the ferrous tartrate colorimetric method is as follows:

[0019] After the tea polyphenol extract, the ferrous tartrate solution and ultrapure water are mixed, the volume is determined with a pH=7.5 phosphoric acid buffer solution, and after being shaken and mixed uniformly, the mixture is left to stand; the ultrapure water is used as a blank control to determine the absorbance, the tea polyphenol content is calculated by using a standard curve, and the tea polyphenol extraction rate is calculated according to formula (1);

[0020]

[0021] In the formula, δ% is the tea polyphenol extraction rate; A 样品 is the absorbance of the tea polyphenol extract at 540 nm wavelength; F is the dilution multiple; Vsample is the volume of the tea polyphenol extract (mL); and msample is the weight of the tea leaves (g);

[0022] The standard curve is y = 0.00806x - 0.03004, R 2 = 0.99998.

[0023] The technical features and benefits of the present application are as follows:

[0024] 1. The present application first uses N-methyl pyrrolidone as an organic solvent for tea polyphenol extraction, effectively utilizing the good solubilizing effect of N-methyl pyrrolidone on poorly soluble drugs, greatly improving the extraction rate of tea polyphenol. And through experiments, it is proved that compared with the conventional ethanol extraction method as an organic solvent, the extraction rate of tea polyphenol using the method provided by the present application is increased by 15.61-15.84%. At the same time, N-methyl pyrrolidone has been included in the published "Catalogue of Cosmetics Raw Materials (2021 Edition)", which can be used as a common solvent.

[0025] 2. The tea polyphenol extraction method provided by the present application is simple to operate, easy to scale up, environmentally friendly in preparation process, low in energy consumption, low in required raw material price, easy to obtain, and meets the current requirements of sustainable development and green chemistry.

[0026] 3. After antioxidant test, it is found that the DPPH free radical scavenging rate, hydroxyl radical scavenging rate and antioxidant effect of the tea polyphenol product prepared by the extraction method of the present application are higher than those of ascorbic acid at the same concentration, and the tea polyphenol product can be used for preparing free radical scavenging drugs, preparations and other commercialized derivative products, such as cosmetics, dressings, health products, etc. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The tea polyphenol standard curve drawn for Example 1.

[0028] Figure 2 The graph of the influence of the mass-volume ratio involved in Examples 1-10 on the extraction rate of tea polyphenol.

[0029] Figure 3 The graph of the influence of the extraction time involved in Examples 11-22 on the extraction rate of tea polyphenol.

[0030] Figure 4 The graph of the influence of the extraction temperature involved in Examples 23-44 on the extraction rate of tea polyphenol.

[0031] Figure 5 The DPPH free radical scavenging rate comparison graph of tea polyphenol and ascorbic acid at the same concentration in Test Example 1.

[0032] Figure 6 The hydroxyl radical scavenging rate comparison graph of tea polyphenol and ascorbic acid at the same concentration in Test Example 2.

[0033] Figure 7A comparison chart of total antioxidant capacity of tea polyphenols and ascorbic acid of the same concentration in Test Example 3. DETAILED DESCRIPTION

[0034] The application will be further described below by specific examples, but not limited thereto.

[0035] The experimental methods described in the examples are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0036] The DPPH free radical scavenging capacity assay kit, the hydroxyl radical scavenging capacity assay kit, and the total antioxidant capacity assay kit are all purchased from Beijing Boxi Shengong Technology Co., Ltd.

[0037] In the following examples, single-factor tests are respectively performed on the application to obtain column charts of the effects of mass-volume ratio, extraction time, and extraction temperature on tea polyphenol extraction rate, and to obtain optimal mass-volume ratio, optimal extraction time, and optimal extraction temperature from the column charts. Then, according to the optimal mass-volume ratio, optimal extraction time, and optimal extraction temperature, orthogonal experiments are designed with tea polyphenol extraction amount as the observation factor, each group of experiments is repeated 3 times, and the optimal extraction conditions are obtained.

[0038] Example 1

[0039] 1. A method for extracting tea polyphenols by using N-methyl pyrrolidone, comprising the following steps:

[0040] 0.5 g of white tea is weighed into a stoppered ethylene tube (25 mL), 10 mL of N-methyl pyrrolidone is added, and after uniform mixing, extraction is performed at 70℃ for 60 min, followed by centrifugation at 5000 r / min for 2-8 min, and after filtration, tea polyphenol extract is obtained; 3 experiments are performed according to this method, and 3 portions of tea polyphenol extract are obtained.

[0041] 2. The tea polyphenol extraction rate of the obtained tea polyphenol extract is determined by the ferrous tartrate colorimetric method, and the specific method is as follows:

[0042] (1) Take 0.1 g ferrous sulfate and 0.5 g potassium sodium tartrate with an analytical balance, add distilled water, dissolve thoroughly by stirring, and then transfer to a 100 mL volumetric flask, dilute to the mark, and shake to obtain a ferrous tartrate solution. Take 1.1997 g disodium hydrogen phosphate and 0.1857 g sodium dihydrogen phosphate, add distilled water, stir, and dilute to 100 mL to obtain a pH 7.5 phosphate buffer solution; take gradient mass standard tea polyphenol samples, respectively, add distilled water to dissolve, stir to dissolve until clear, and then transfer to a 100 mL volumetric flask, dilute to the mark, to obtain tea polyphenol standard solutions with gradient concentrations of 20, 40, 60, 80, and 100 μg / mL. Then take 1 mL of tea polyphenol standard solutions with gradient concentrations of 20, 40, 60, 80, and 100 μg / mL in a 25 mL stoppered ethylene tube, respectively, add 4 mL distilled water, 5 mL ferrous tartrate solution, dilute to the mark with the pH 7.5 phosphate buffer solution, shake to mix, and let stand for 10 min. Use a UV spectrophotometer, a 10 mm cuvette, and determine the absorbance values of the different concentrations of samples. Plot a standard curve with the concentration c (μg·mL -1 ) of the tea polyphenol standard as the abscissa and the absorbance value at 540 nm as the ordinate, and the results are shown in Figure 1 .

[0043] As shown in Figure 1 , the equation of the standard curve is y = 0.00806x - 0.03004, R 2 = 0.99998, and the absorbance and the concentration of tea polyphenol have a good correlation, so the extraction amount of tea polyphenol can be calculated by the standard curve.

[0044] (2) Take 2 mL of the tea polyphenol extract prepared in this example into a 25 mL volumetric flask, add 8.0 mL distilled water and 5.0 mL ferrous tartrate solution, mix, dilute to the mark with the phosphate buffer solution, mix, let stand for 10 min, and determine the absorbance at 540 nm with a blank solution as the reference, and calculate the content of tea polyphenol in the tea polyphenol extract by the standard curve. Finally, calculate the extraction rate of tea polyphenol according to formula (1);

[0045]

[0046] In the formula, δ% is the extraction rate of tea polyphenol; A 样品 is the absorbance of the tea polyphenol extract at 540 nm; F is the dilution factor; Vsample is the volume of the tea polyphenol extract (mL); and msample is the weight of the tea leaves (g).

[0047] Example 2

[0048] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, and the mass-volume ratio is 30:1.

[0049] Example 3

[0050] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1.

[0051] Example 4

[0052] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 25 mL, and the mass-volume ratio is 50:1.

[0053] Example 5

[0054] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 30 mL, and the mass-volume ratio is 60:1.

[0055] Example 6

[0056] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, and the green tea is used instead of white tea.

[0057] Example 7

[0058] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, and the green tea is used instead of white tea, and the mass of green tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, and the mass-volume ratio is 30:1.

[0059] Example 8

[0060] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, and the green tea is used instead of white tea, and the mass of green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1.

[0061] Example 9

[0062] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 25 mL, and the mass-to-volume ratio is 50:1.

[0063] Example 10

[0064] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 30 mL, and the mass-to-volume ratio is 60:1.

[0065] Example 11

[0066] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-to-volume ratio is 30:1, and the extraction time is 30 min.

[0067] Example 12

[0068] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-to-volume ratio is 30:1, and the extraction time is 60 min.

[0069] Example 13

[0070] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-to-volume ratio is 30:1, and the extraction time is 90 min.

[0071] Example 14

[0072] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-to-volume ratio is 30:1, and the extraction time is 120 min.

[0073] Example 15

[0074] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-to-volume ratio is 30:1, and the extraction time is 150 min.

[0075] Example 16

[0076] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the white tea has a mass of 0.5 g, the N-methyl pyrrolidone has a volume of 15 mL, the mass-volume ratio is 30:1, and the extraction time is 180 min.

[0077] Example 17

[0078] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, the green tea has a mass of 0.5 g, the N-methyl pyrrolidone has a volume of 20 mL, the mass-volume ratio is 40:1, and the extraction time is 30 min.

[0079] Example 18

[0080] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, the green tea has a mass of 0.5 g, the N-methyl pyrrolidone has a volume of 20 mL, the mass-volume ratio is 40:1, and the extraction time is 60 min.

[0081] Example 19

[0082] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, the green tea has a mass of 0.5 g, the N-methyl pyrrolidone has a volume of 20 mL, the mass-volume ratio is 40:1, and the extraction time is 90 min.

[0083] Example 20

[0084] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, the green tea has a mass of 0.5 g, the N-methyl pyrrolidone has a volume of 20 mL, the mass-volume ratio is 40:1, and the extraction time is 120 min.

[0085] Example 21

[0086] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, the green tea has a mass of 0.5 g, the N-methyl pyrrolidone has a volume of 20 mL, the mass-volume ratio is 40:1, and the extraction time is 150 min.

[0087] Example 22

[0088] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea is green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1; the extraction time is 180 min.

[0089] Example 23

[0090] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, and the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 40°C.

[0091] Example 24

[0092] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, and the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 45°C.

[0093] Example 25

[0094] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, and the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 50°C.

[0095] Example 26

[0096] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, and the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 55°C.

[0097] Example 27

[0098] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of the white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, and the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 60°C.

[0099] Example 28

[0100] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 65°C.

[0101] Example 29

[0102] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 70°C.

[0103] Example 30

[0104] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 75°C.

[0105] Example 31

[0106] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 80°C.

[0107] Example 32

[0108] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 85°C.

[0109] Example 33

[0110] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the mass of white tea is 0.5 g, the volume of N-methyl pyrrolidone is 15 mL, the mass-volume ratio is 30:1; the extraction time is 120 min, and the extraction temperature is 90°C.

[0111] Example 34

[0112] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 40°C.

[0113] Example 35

[0114] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 45°C.

[0115] Example 36

[0116] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 50°C.

[0117] Example 37

[0118] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 55°C.

[0119] Example 38

[0120] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 60°C.

[0121] Example 39

[0122] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of white tea, and the mass of the green tea is 0.5 g, the volume of N-methyl pyrrolidone is 20 mL, and the mass-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 65°C.

[0123] Example 40

[0124] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, and the mass of the green tea is 0.5 g, the volume of the N-methyl pyrrolidone is 20 mL, and the mass-to-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 70°C.

[0125] Example 41

[0126] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, and the mass of the green tea is 0.5 g, the volume of the N-methyl pyrrolidone is 20 mL, and the mass-to-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 75°C.

[0127] Example 42

[0128] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, and the mass of the green tea is 0.5 g, the volume of the N-methyl pyrrolidone is 20 mL, and the mass-to-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 80°C.

[0129] Example 43

[0130] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, and the mass of the green tea is 0.5 g, the volume of the N-methyl pyrrolidone is 20 mL, and the mass-to-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 85°C.

[0131] Example 44

[0132] A method for extracting tea polyphenols by using N-methyl pyrrolidone, the specific steps are the same as those in Example 1, except that the tea leaves are green tea, the green tea is used instead of the white tea, and the mass of the green tea is 0.5 g, the volume of the N-methyl pyrrolidone is 20 mL, and the mass-to-volume ratio is 40:1; the extraction time is 90 min, and the extraction temperature is 90°C.

[0133] Comparative Example 1

[0134] A method for extracting tea polyphenols, the specific steps are the same as those in Example 1, except that the solvent selected is ethanol, and the ethanol is used instead of the N-methyl pyrrolidone.

[0135] Comparative Example 2

[0136] A method for extracting tea polyphenols, the specific steps are the same as example 1, the difference is that the solvent is selected as 15 mL of ethanol, ethanol is used instead of N-methyl pyrrolidone, the mass-volume ratio is 30:1, the extraction time is 125 min, and the extraction temperature is 80°C.

[0137] Comparative example 3

[0138] A method for extracting tea polyphenols, the specific steps are the same as example 1, the difference is that the solvent is selected as 15 mL of ethanol, ethanol is used instead of N-methyl pyrrolidone, the mass-volume ratio is 30:1, the extraction time is 125 min, and the extraction temperature is 80°C.

[0139] Comparative example 4

[0140] A method for extracting tea polyphenols, the specific steps are the same as example 1, the difference is that the solvent is selected as 15 mL of ethanol, ethanol is used instead of N-methyl pyrrolidone, the mass-volume ratio is 30:1, the extraction time is 125 min, and the extraction temperature is 80°C.

[0141] Test example 1

[0142] The extraction rate of tea polyphenols prepared in examples 1-10 is determined according to the method described in example 1, the effect of the mass-volume ratio of tea leaves and N-methyl pyrrolidone on the extraction rate of tea polyphenols is obtained, and the results are shown in Figure 2 .

[0143] From Figure 2 it can be seen that when the mass-volume ratio increases, the extraction rate of tea polyphenols shows an upward trend. For white tea, the rising amplitude is obvious in the interval of 1:(20-30), while for green tea, the rising amplitude is obvious in the interval of 1:(20-40), which is due to the increase of the mass-volume ratio, the contact surface between tea leaves and solvent is prolonged, resulting in the acceleration of the exudation speed of tea polyphenols. However, the increase of the extraction solvent leads to longer diffusion time required for tea polyphenols, and the probability of dissolution of other impurities increases, when the mass-volume ratio increases to a certain extent, the dissolution rate of tea polyphenols in the solvent approaches saturation, and the increase of the dissolution rate becomes slow.

[0144] Test example 2

[0145] The extraction rate of tea polyphenols prepared in examples 11-22 is determined according to the method described in example 1, the effect of the extraction time on the extraction rate of tea polyphenols is obtained, and the results are shown in Figure 3 .

[0146] From Figure 3It can be seen that the extraction rate of tea polyphenols increases with the extension of extraction time, reaching a maximum at 120 min for white tea and 90 min for green tea, followed by a downward trend. With prolonged extraction time, the frequency and speed of molecular motion are enhanced, thereby increasing solvent permeability, improving the dissolution rate and content of effective components of tea polyphenols, and increasing the extraction rate. However, excessively long extraction times may lead to oxidation of tea polyphenols and structural changes in some tea polyphenols, while the continued dissolution of other impurities causes back osmosis, thus reducing the extraction rate of tea polyphenols.

[0147] Test Example 3

[0148] The extraction rates of tea polyphenols prepared in Examples 23-44 were determined according to the method described in Example 1. The effect of extraction temperature on the extraction rate of tea polyphenols was obtained, and the results are as follows: Figure 4 As shown.

[0149] from Figure 4 It can be seen that with the increase of extraction temperature, the rate of tea polyphenols diffusing out of the cells accelerates, and the extraction rate of tea polyphenols increases accordingly. White tea reaches its peak at 80℃, and green tea reaches its peak at 85℃. Afterward, the extraction rate decreases, possibly because excessively high temperatures damage the cell walls and some polyphenol structures in the tea leaves, and also accelerate the oxidation of tea polyphenols, reducing the effective content of tea polyphenols and thus decreasing the extraction rate.

[0150] Test Example 4

[0151] Based on the results obtained from test examples 1-3, according to Figure 2 Preliminary analysis determined that 30:1 was the optimal mass-to-volume ratio for extracting polyphenols from white tea, while 40:1 was the optimal ratio for extracting polyphenols from green tea. Furthermore, 25:1, 30:1, 35:1 and 35:1, 40:1, 45:1 were selected as potentially optimized values ​​for the mass-to-volume ratio of white tea to green tea. Figure 3 The optimal extraction time for white tea polyphenols was 120 min, while for green tea it was 90 min. 115 min, 120 min, 125 min and 85 min, 90 min, 95 min were considered as potential optimal extraction times for white and green tea. Figure 4 The optimal extraction temperature for white tea polyphenols was found to be 80℃, and for green tea polyphenols, it was 85℃. Optimizable values ​​for the extraction times of white tea and green tea were selected as 75℃, 80℃, 85℃ and 80℃, 85℃, 90℃.

[0152] Using the optimal mass-volume ratio, optimal extraction time, and optimal extraction temperature as independent variables, and the extraction rate of tea polyphenols as the response value, an orthogonal experiment was conducted, and the results of the orthogonal experiment are shown in Tables 1 and 2.

[0153] Table 1

[0154]

[0155] Table 2

[0156]

[0157]

[0158] From the range analysis results of Tables 1-2, the three factors affecting the content of tea polyphenols in white tea and green tea are mass-volume ratio > extraction temperature > extraction time, the optimal extraction conditions for extracting white tea polyphenols by N-methyl pyrrolidone are mass-volume ratio 30:1, extraction at 85°C for 125 min, and the optimal extraction conditions for extracting green tea polyphenols are mass-volume ratio 40:1, extraction at 85°C for 95 min. The optimal extraction parameters are not in the orthogonal experiment conditions, and need to be verified. Under the optimal extraction parameters, the extraction rate of white tea polyphenols by the extraction method of the present application is 21.38%, and the extraction rate of green tea polyphenols is 23.91%.

[0159] Test Example 5

[0160] The extraction rates of tea polyphenols prepared in Comparative Examples 1-4 were determined according to the method described in Example 1, the extraction rate of white tea polyphenols in Comparative Example 1 was 5.77%, the extraction rate of green tea polyphenols in Comparative Example 2 was 8.01%, the extraction rate of white tea polyphenols in Comparative Example 3 was 8.52%, and the extraction rate of green tea polyphenols in Comparative Example 4 was 14.36%,

[0161] From the comparison of experimental data, compared with the conventional extraction method using ethanol as the organic solvent, the extraction rate of tea polyphenols by the extraction method of the present application is increased by 15.61-15.84%. This shows that the present application first uses N-methyl pyrrolidone as the organic solvent for the extraction of tea polyphenols, effectively utilizes the good solubilization of N-methyl pyrrolidone for poorly soluble drugs, and greatly improves the extraction rate of tea polyphenols.

[0162] Test Example 1

[0163] The white tea polyphenol extract and the green tea polyphenol extract were obtained by the method for extracting tea polyphenols by N-methyl pyrrolidone described in Example 1, and according to the optimal extraction conditions for extracting white tea polyphenols and the optimal extraction conditions for extracting green tea polyphenols described in Test Example 4.

[0164] Then, the DPPH radical scavenging ability test kit was used, the white tea tea polyphenol extract and the green tea tea polyphenol extract were diluted to 0.02895 mg / mL, and the same concentration of ascorbic acid solution was prepared, and then the DPPH radical scavenging ability of the white tea tea polyphenol diluent, the green tea tea polyphenol diluent and the ascorbic acid solution was determined by ultraviolet-visible spectrophotometry. For the specific dilution process and determination method, please refer to the test kit instruction manual, and the results are shown in Table 1. Figure 5

[0165] Test Example 2

[0166] The white tea tea polyphenol extract and the green tea tea polyphenol extract were obtained by the method of extracting tea polyphenols with N-methyl pyrrolidone described in Example 1 according to the optimal extraction conditions of white tea tea polyphenols and the optimal extraction conditions of green tea tea polyphenols described in Test Example 4.

[0167] Then, the hydroxyl radical scavenging ability test kit was used, the white tea tea polyphenol extract and the green tea tea polyphenol extract were diluted to 0.0579 mg / mL, and the same concentration of ascorbic acid solution was prepared, and then the hydroxyl radical scavenging ability of the white tea tea polyphenol diluent, the green tea tea polyphenol diluent and the ascorbic acid solution was determined by ultraviolet-visible spectrophotometry. For the specific dilution process and determination method, please refer to the test kit instruction manual, and the results are shown in Table 2. Figure 6

[0168] Test Example 3

[0169] The white tea tea polyphenol extract and the green tea tea polyphenol extract were obtained by the method of extracting tea polyphenols with N-methyl pyrrolidone described in Example 1 according to the optimal extraction conditions of white tea tea polyphenols and the optimal extraction conditions of green tea tea polyphenols described in Test Example 4.

[0170] Then, the total antioxidant capacity test kit was used, the white tea tea polyphenol extract and the green tea tea polyphenol extract were diluted to 0.1737 mg / mL, and the same concentration of ascorbic acid solution was prepared, and then the total antioxidant capacity of the white tea tea polyphenol diluent, the green tea tea polyphenol diluent and the ascorbic acid solution was determined by ultraviolet-visible spectrophotometry. For the specific dilution process and determination method, please refer to the test kit instruction manual, and the results are shown in Table 3. Figure 7

[0171] As can be seen from Table 1, the DPPH radical scavenging rate of the white tea tea polyphenol of Test Example 1 is 84.7%, and the DPPH radical scavenging rate of the green tea tea polyphenol is 82.1%, which is far more than 23.7% of ascorbic acid at the same concentration. Figure 5 As can be seen from Table 2, the hydroxyl radical scavenging rate of the white tea tea polyphenol of Test Example 2 is 87.9%, and the hydroxyl radical scavenging rate of the green tea tea polyphenol is 86.2%, which is far more than 23.7% of ascorbic acid at the same concentration.

[0172] Figure 6 ​​​​It can be seen that the scavenging rate of hydroxyl radicals of white tea polyphenols in Experiment Example 2 was 29.8%, the scavenging rate of hydroxyl radicals of green tea polyphenols was 28.1%, while the scavenging rate of ascorbic acid at the same concentration was only 6.8%.

[0173] Depend on Figure 7 It can be seen that the total antioxidant capacity of white tea polyphenols in Experiment 1 is 2.91 μmol / mL, and the total antioxidant capacity of green tea polyphenols is 3.67 μmol / mL, which is higher than that of ascorbic acid at the same concentration of 2.03 μmol / mL.

[0174] The data above shows that the tea polyphenol products prepared by the extraction method of this invention have higher DPPH free radical scavenging rate, hydroxyl free radical scavenging rate, and antioxidant effect than ascorbic acid at the same concentration. They can be used to prepare drugs, preparations, and other commercial derivatives for scavenging free radicals, such as cosmetics, dressings, and health products.

[0175] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for extracting tea polyphenols using N-methylpyrrolidone, characterized in that, The steps include the following: Tea leaves were added to N-methylpyrrolidone and mixed evenly. The mixture was then extracted at 75-90℃ for 30-180 min, followed by centrifugation at 4500-5500 r / min for 2-8 min. After filtration, the tea polyphenol extract was obtained. The extraction rate of tea polyphenols in the obtained tea polyphenol extract was determined by the ferrous tartrate colorimetric method. The mass-to-volume ratio of tea leaves to N-methylpyrrolidone is 1:(20~60), unit: g / mL.

2. The method for extracting tea polyphenols using N-methylpyrrolidone as described in claim 1, characterized in that, The tea leaves mentioned are either white tea or green tea.

3. The method for extracting tea polyphenols using N-methylpyrrolidone as described in claim 1, characterized in that, The mass-to-volume ratio of the tea leaves and N-methylpyrrolidone is 1:(25~45), unit: g / mL.

4. The method for extracting tea polyphenols using N-methylpyrrolidone as described in claim 3, characterized in that, The mass-to-volume ratio of the tea leaves and N-methylpyrrolidone is 1:(30~40), unit: g / mL.

5. The method for extracting tea polyphenols using N-methylpyrrolidone as described in claim 1, characterized in that, The extraction temperature is 80~85℃.

6. The method for extracting tea polyphenols using N-methylpyrrolidone as described in claim 1, characterized in that, The extraction time is 85-125 minutes.

7. The method for extracting tea polyphenols using N-methylpyrrolidone as described in claim 6, characterized in that, The extraction time is 90-120 minutes.

8. The method for extracting tea polyphenols using N-methylpyrrolidone as described in claim 1, characterized in that, The ferrous tartrate colorimetric method is specifically as follows: After mixing the tea polyphenol extract, ferrous tartrate solution and ultrapure water, the volume was adjusted with phosphate buffer solution at pH 7.5, shaken and mixed, and then allowed to stand. The absorbance was measured using ultrapure water as a blank control. The tea polyphenol content was calculated using the standard curve, and the extraction rate of tea polyphenols was calculated according to formula (1). （1） In the formula: δ% is the extraction rate of tea polyphenols; A 样品 The absorbance of the tea polyphenol extract was measured at a wavelength of 540 nm; F represents the dilution factor; V represents the absorbance of the extract. 样品 The volume of tea polyphenol extract (mL); m 样品 The weight of the tea leaves is in grams. The standard curve is y = 0.00806x - 0.03004, R0 2 =0.99998.

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