Functional tea processing technology and research methods on the inhibition of XOD activity by leaf water extract

Abstract

The invention discloses a functional tea processing technology and a method for studying the inhibition of XOD activity by leaf water extract, comprising the following steps: S1: preparing a functional tea water extract; S2: preparing a sample control without functional treatment; S3: constructing a XOD catalytic reaction system and activity inhibition evaluation; S4: taking the tea water extracts in S1 and S2 and operating them in S3; S5: taking three kinds of tea leaves and subjecting them to the same pure oxygen constant temperature oxidation for 8 hours, and calculating the activity inhibition rate of XOD; S6: taking green tea leaves and subjecting them to oxidation by different methods for 8 hours, and calculating the activity inhibition rate of XOD; S7: taking green tea leaves and subjecting them to sealed pure oxygen constant temperature oxidation for different times, and calculating the in vitro XOD activity inhibition rate. The invention can obtain the different inhibitory effects of the tea water extracts of the three kinds of tea leaves on the XOD activity, and patients with gout and hyperuricemia can effectively select the most efficient tea leaves according to their own conditions, thereby effectively inhibiting the XOD activity in vivo.

Description

Technical Field

[0001] The invention relates to the field of tea, and in particular to a functional tea processing technology and a research method for inhibiting XOD activity by leaf water extract. Background Art

[0002] Tea leaves, commonly known as tea, generally include the leaves and buds of the tea tree. Tea ingredients include catechins, cholestenone, caffeine, inositol, folic acid, and pantothenic acid, which are good for health. XOD, or xanthine oxidase, is an enzyme with low specificity that can catalyze hypoxanthine to generate xanthine and then generate uric acid, and can also directly catalyze xanthine to generate uric acid. It is a flavin enzyme containing molybdenum, non-heme iron, inorganic sulfide, and FAD. It exists in cow's milk, animals (especially the liver and kidneys of birds), insects, and bacteria.

[0003] Especially for patients with gout and hyperuricemia, it is necessary to reduce the activity of xanthine oxidase in the human body to reduce the formation of uric acid and reactive oxygen in the human body, and drinking tea can inhibit the activity of XOD to a certain extent. However, the prior art does not clearly know the different degrees of inhibition of XOD activity by different types of tea, and thus it is impossible to effectively select the most efficient tea. Summary of the invention

[0004] The invention discloses a functional tea processing technology and a research method for inhibiting XOD activity by leaf water extract, aiming to solve the technical problems in the background technology.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A functional tea processing technology comprises the following specific steps:

[0007] S1: Pick and process tea leaves from June to October (summer and autumn) in areas above 800 meters above sea level, and perform functional processing on the picked green tea, black tea and dark tea respectively;

[0008] S2: placing the green tea leaves after withering, the black tea leaves after fermentation and the dark tea leaves in a sealed container filled with pure oxygen, shaking them at a constant speed for a certain period of time under a constant temperature condition, and continuously adding pure water to moisten the tea leaves during the process;

[0009] S3: Take out green tea leaves, black tea leaves and dark tea leaves respectively, rub and shape them, and dry them (vacuum drying, 35±5° C.) to obtain functional finished green tea A, finished black tea and finished dark tea.

[0010] In a preferred embodiment, in S1, the tea polyphenols, caffeine and tea polysaccharides contents of green tea are 35±5%, 10±2% and 5±1% respectively, the tea polyphenols, caffeine and tea polysaccharides contents of black tea are 20±5%, 5±2% and 8±1% respectively, and the tea polyphenols, caffeine and tea polysaccharides contents of dark tea are 10±5%, 3±1% and 10±2% respectively.

[0011] In a preferred embodiment, in S2, the weights of green tea, black tea and dark tea are 1kg-2kg respectively, the constant temperature is 45±5°C, the uniform shaking time is 1-12h, the supplemented pure water is 100±10m, and the environment needs to be kept moist during the process.

[0012] A method for studying the inhibition of XOD activity by leaf water extract comprises the following specific steps:

[0013] S1: preparing tea water extracts A of functional finished green tea A, finished black tea and finished dark tea respectively;

[0014] (1) Weigh 60 g of finished green tea A, finished black tea, and finished dark tea, and place them in 1000 mL beakers with lids respectively;

[0015] (2) Add 300 mL of pure water to the beaker and boil for 1 h, filter the residue, add 200 mL of pure water and boil for 1 h, filter, and combine the first and second extraction filtrates;

[0016] (3) vacuum concentrating the filtrate and then freeze-drying to prepare aqueous extracts of finished green tea A, finished black tea and finished dark tea respectively;

[0017] S2: preparing green tea, black tea and dark tea water extracts without functional treatment as sample controls, respectively, and the preparation steps are the same as those in S1 above;

[0018] S3: Construction of xanthine (Xan)-xanthine oxidase (XOD) catalytic reaction system and activity inhibition evaluation;

[0019] (1) Preparation of xanthine solution:

[0020] 1mmol / L xanthine solution: accurately weigh 0.003g xanthine in 19.723mL pure water, dissolve with ultrasound, and store in dark place;

[0021] 0.3mmol / L xanthine solution: Measure 6mL of 1mmol / L xanthine solution and dilute to 20mL with 14mL of purified water;

[0022] (2) Preparation of XOD solution:

[0023] 0.1mol / LpH=7.5 sodium pyrophosphate buffer (prepared and used immediately): accurately weigh 0.6647g sodium pyrophosphate and 0.0044g ethylenediaminetetraacetic acid, add pure water and dissolve with the aid of ultrasound, transfer it into a 25mL volumetric flask and dilute to the scale with pure water, use a pH meter to determine the pH value, if it is not 7.5, adjust the pH to about 7.5 with phosphoric acid;

[0024] 7.2u / mL XOD solution: accurately weigh 0.001g xanthine oxidase (8.6u / mg) and dissolve it in 1.194mL sodium pyrophosphate buffer and store at low temperature and away from light;

[0025] 30mu / mL XOD solution: Accurately measure 0.083mL of 7.2u / mL xanthine oxidase solution and dilute to 20mL with 19.917mL of purified water.

[0026]

[0027] (3) using ultraviolet spectroscopy (UV-Vis) to scan the xanthine-xanthine oxidase catalytic reaction system solution at full wavelength, and recording the absorbance value A0 at 290±3nm;

[0028] (4) Evaluation of XOD activity inhibition

[0029] Take samples of different concentrations and proceed as follows:

[0030]

[0031] The xanthine-xanthine oxidase catalytic reaction system solution was scanned at full wavelength by ultraviolet spectroscopy (UV-Vis) and the absorbance value A1 at 290±3nm was recorded. The XOD activity inhibition rate I was calculated according to the following formula:

[0032] I(%)=(1-A1 / A0)×100%;

[0033] S4: taking the tea water extracts prepared in S1 and S2 respectively, and performing the operation in S3 to measure their inhibitory effects on in vitro XOD activity respectively, and making comparative analysis;

[0034] S5: Take the summer and autumn green tea leaves, black tea leaves and dark tea leaves after withering, and subject them to the same pure oxygen constant temperature (45±5℃) oxidation for 8 hours, then evaluate the water extracts of the green tea leaves, black tea leaves and dark tea leaves after 8 hours of oxidation in vitro Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, calculate the activity inhibition rate of different types of tea water extracts on in vitro XOD after oxidation, and determine the best processing raw materials;

[0035] S6: Take out the summer and autumn green tea leaves after withering, and oxidize them by different methods for 8 hours, then evaluate the tea water extracts of green tea A after oxidation in vitro in the Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, calculate the activity inhibition rate of different types of tea water extracts on in vitro XOD after oxidation, and determine the best oxidation method;

[0036] S7: Take out the summer and autumn green tea leaves after withering, and oxidize them for different time periods by using a closed pure oxygen constant temperature (45±5°C) oxidation method, and then evaluate the green tea leaf water extracts oxidized for different time periods in an in vitro Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, and calculate the inhibition rate of the tea water extracts oxidized for different time periods on the in vitro XOD activity, and determine the optimal oxidation time;

[0037] S8: Make the measurement results of S5-7 into corresponding charts, and then make the final judgment result based on the chart information.

[0038] In a preferred embodiment, in S6, the different oxidation methods include air blast drying oxidation (70±5°C), room temperature drying oxidation and closed pure oxygen constant temperature (45±5°C) oxidation.

[0039] In a preferred embodiment, in S7, the oxidation time includes 1 h, 2 h, 4 h, 6 h, 8 h, 10 h and 12 h.

[0040] In a preferred solution, in S8, the chart includes a bar chart and a curve chart.

[0041] As can be seen from the above, the functional tea processing technology and the research method for the inhibition of XOD activity by leaf water extract provided by the present invention first perform functional processing on green tea, black tea and dark tea, so as to facilitate the subsequent reaction of their tea water extracts with XOD and measure the activity of XOD; according to the measurement and research of the XOD activity of the tea water extracts of the three kinds of tea leaves after special treatment under non-oxidation conditions, oxidation conditions for 8 hours, different oxidation methods of green tea, and different oxidation time conditions after reaction with XOD, the different inhibitory effects of the tea water extracts of the three kinds of tea leaves on XOD activity are obtained, so that they can be ranked, and it can be obtained which treatment method can improve the inhibitory effect of tea leaves on XOD activity, and patients with gout and hyperuricemia can effectively choose the most efficient tea leaves according to their own conditions, so as to use tea leaves to effectively inhibit XOD activity in the body. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The present invention is a flow chart of a functional tea processing technology.

[0043] Figure 2The present invention provides a flow chart of a method for studying the inhibition of XOD activity by leaf water extract.

[0044] Figure 3 This is a bar graph of the inhibition rates of three tea water extracts on XOD activity in a research method for the inhibition of XOD activity by leaf water extracts proposed by the present invention.

[0045] Figure 4 This is the XOD activity spectrum of green tea water extract according to the method for studying the inhibition of XOD activity by leaf water extract proposed by the present invention (III is the concentration of 400, 500, 600, 700, 800 ug / mL).

[0046] Figure 5 This is a spectrum diagram of the XOD activity of black tea water extract according to a method for studying the inhibition of XOD activity by leaf water extract proposed by the present invention.

[0047] Figure 6 This is a spectrum diagram of the XOD activity of dark tea water extract according to a method for studying the inhibition of XOD activity by leaf water extract proposed by the present invention.

[0048] Figure 7 This is a bar graph of the inhibition rate of XOD activity by green tea water extract after oxygenation for 8 hours using different methods, according to a method for studying the inhibition of XOD activity by leaf water extract proposed in the present invention.

[0049] Figure 8 This is a spectrum diagram of the XOD activity of a green tea water extract that was dried and oxidized for 8 hours after forced air drying according to a method for studying the inhibition of XOD activity by a leaf water extract proposed in the present invention.

[0050] Fig. 9 This is a spectrum diagram of the XOD activity of a green tea water extract dried and oxidized at room temperature for 8 hours according to a method for studying the inhibition of XOD activity by leaf water extract proposed in the present invention.

[0051] Fig.10 This is a spectrum diagram of the XOD activity of green tea water extract oxidized at constant temperature with pure oxygen for 8 hours according to a method for studying the inhibition of XOD activity by leaf water extract proposed in the present invention.

[0052] Fig.11 This is a bar graph of the inhibition rates of three types of tea water extracts on XOD activity after constant temperature oxidation with pure oxygen according to a method for studying the inhibition of XOD activity by leaf water extracts proposed in the present invention.

[0053] Fig.12 This is a spectrum diagram of the XOD activity of the water extract of green tea leaves after constant temperature oxidation with pure oxygen according to a method for studying the inhibition of XOD activity by the water extract of leaves proposed in the present invention.

[0054] Fig.13This is a spectrum diagram of the XOD activity of the water extract of black tea leaves after constant temperature oxidation with pure oxygen according to a method for studying the inhibition of XOD activity by the water extract of leaves proposed in the present invention.

[0055] Fig.14 This is a spectrum diagram of the XOD activity of black tea leaf water extract after constant temperature oxidation with pure oxygen according to a method for studying the inhibition of XOD activity by leaf water extract proposed in the present invention.

[0056] Fig.15 This is a bar graph of the inhibition rate of XOD activity of green tea leaf water extract after constant temperature oxidation with pure oxygen for 1h, 2h, 4h, 6h, 8h, 10h and 12h according to a method for studying the inhibition of XOD activity by leaf water extract proposed in the present invention. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0058] Reference Figure 1 , a functional tea processing technology, comprising the following specific steps:

[0059] S1: Pick and process tea leaves from June to October (summer and autumn) in areas above 800 meters above sea level, and perform functional processing on the picked green tea, black tea and dark tea respectively;

[0060] S2: placing the green tea leaves after withering, the black tea leaves after fermentation and the dark tea leaves in a sealed container filled with pure oxygen, shaking them at a constant speed for a certain period of time under a constant temperature condition, and continuously adding pure water to moisten the tea leaves during the process;

[0061] S3: Take out green tea leaves, black tea leaves and dark tea leaves respectively, rub and shape them, and dry them (vacuum drying, 35±5° C.) to obtain functional finished green tea A, finished black tea and finished dark tea.

[0062] In a preferred embodiment, in S1, the content ratios of tea polyphenols, caffeine and tea polysaccharides in green tea are 35±5%, 10±2% and 5±1% respectively, the content ratios of tea polyphenols, caffeine and tea polysaccharides in black tea are 20±5%, 5±2% and 8±1% respectively, and the content ratios of tea polyphenols, caffeine and tea polysaccharides in dark tea are 10±5%, 3±1% and 10±2% respectively.

[0063] In a preferred embodiment, in S2, the weights of green tea, black tea and dark tea are 1kg-2kg respectively, the constant temperature is 45±5°C, the uniform shaking time is 1-12h, the supplemented pure water is 100±10m, and the environment needs to be kept moist during the process.

[0064] Reference Figure 2-15 , a method for studying the inhibition of XOD activity by leaf water extract, comprising the following specific steps:

[0065] S1: preparing tea water extracts A of functional finished green tea A, finished black tea and finished dark tea respectively;

[0066] (1) Weigh 60 g of finished green tea A, finished black tea, and finished dark tea, and place them in 1000 mL beakers with lids respectively;

[0067] (2) Add 300 mL of pure water to each beaker and boil for 1 h, filter the residue, add 200 mL of pure water and boil for 1 h, filter, and combine the first and second extraction filtrates;

[0068] (3) vacuum concentrating the filtrate and then freeze-drying to prepare aqueous extracts of finished green tea A, finished black tea and finished dark tea respectively;

[0069] S2: preparing green tea, black tea and dark tea water extracts without functional treatment as sample controls, respectively, and the preparation steps are the same as those in S1 above;

[0070] S3: Construction of xanthine (Xan)-xanthine oxidase (XOD) catalytic reaction system and activity inhibition evaluation;

[0071] (1) Preparation of xanthine solution:

[0072] 1mmol / L xanthine solution: accurately weigh 0.003g xanthine in 19.723mL pure water, dissolve with ultrasound, and store in dark place;

[0073] 0.3mmol / L xanthine solution: Measure 6mL of 1mmol / L xanthine solution and dilute to 20mL with 14mL of purified water;

[0074] (2) Preparation of XOD solution:

[0075] 0.1mol / LpH=7.5 sodium pyrophosphate buffer (prepared and used immediately): accurately weigh 0.6647g sodium pyrophosphate and 0.0044g ethylenediaminetetraacetic acid, add pure water and dissolve with the aid of ultrasound, transfer it into a 25mL volumetric flask and dilute to the scale with pure water, use a pH meter to determine the pH value, if it is not 7.5, adjust the pH to about 7.5 with phosphoric acid;

[0076] 7.2u / mL XOD solution: accurately weigh 0.001g xanthine oxidase (8.6u / mg) and dissolve it in 1.194mL sodium pyrophosphate buffer and store at low temperature and away from light;

[0077] 30mu / mL XOD solution: Accurately measure 0.083mL of 7.2u / mL xanthine oxidase solution and dilute to 20mL with 19.917mL of purified water.

[0078]

[0079] (3) using ultraviolet spectroscopy (UV-Vis) to scan the xanthine-xanthine oxidase catalytic reaction system solution at full wavelength, and recording the absorbance value A0 at 290±3nm;

[0080] (4) Evaluation of XOD activity inhibition

[0081] Take samples of different concentrations and proceed as follows:

[0082]

[0083] The xanthine-xanthine oxidase catalytic reaction system solution was scanned at full wavelength by ultraviolet spectroscopy (UV-Vis) and the absorbance value A1 at 290±3nm was recorded. The XOD activity inhibition rate I was calculated according to the following formula:

[0084] I(%)=(1-A1 / A0)×100%;

[0085] S4: taking the tea water extracts prepared in S1 and S2 respectively, and performing the operation in S3 to measure their inhibitory effects on in vitro XOD activity respectively, and making comparative analysis;

[0086] S5: Take the summer and autumn green tea leaves, black tea leaves and dark tea leaves after withering, and subject them to the same pure oxygen constant temperature (45±5℃) oxidation for 8 hours, then evaluate the water extracts of the green tea leaves, black tea leaves and dark tea leaves after 8 hours of oxidation in vitro Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, calculate the activity inhibition rate of different types of tea water extracts on in vitro XOD after oxidation, and determine the best processing raw materials;

[0087] S6: Take out the summer and autumn green tea leaves after withering, and oxidize them by different methods for 8 hours, then evaluate the tea water extracts of green tea A after oxidation in vitro in the Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, calculate the activity inhibition rate of different types of tea water extracts on in vitro XOD after oxidation, and determine the best oxidation method;

[0088] S7: Take out the summer and autumn green tea leaves after withering, and oxidize them for different time periods by using a closed pure oxygen constant temperature (45±5°C) oxidation method, and then evaluate the green tea leaf water extracts oxidized for different time periods in an in vitro Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, and calculate the inhibition rate of the tea water extracts oxidized for different time periods on the in vitro XOD activity, and determine the optimal oxidation time;

[0089] S8: Make the measurement results of S5-7 into corresponding charts, and then make the final judgment result based on the chart information.

[0090] Depend on Figure 3-6 It can be seen that the inhibition rates of the three tea water extracts on XOD activity are all negative values. The inhibitory activity of green tea water extract on XOD is: between 400-600μg / mL, the inhibition rate first decreases slowly and then increases rapidly; between 600-800μg / mL, the inhibition rate first decreases and then increases rapidly, and the lowest value (-18.23%) appears at 500μg / mL, and the highest value (-4.34%) appears at 800μg / mL; the inhibitory activity of black tea water extract on XOD is: between 400-600μg / mL, the inhibition rate first increases and then decreases, and between 600-800μg / mL, the inhibition rate first decreases and then increases rapidly. L, the inhibition rate first decreased rapidly and then increased slowly, and the lowest value (-15.14%) appeared at 700μg / mL, and the highest value (-7.41%) appeared at 500μg / mL; the inhibitory activity of black tea water extract on XOD was as follows: between 400-600μg / mL, the inhibition rate did not change much; between 600-700μg / mL, the inhibition rate decreased rapidly, between 700-800μg / mL, the inhibition rate decreased slowly, and the lowest value (-15.61%) appeared at 800μg / mL, and the highest value (-4.61%) appeared at 600μg / mL.

[0091] In a preferred embodiment, in S6, the different oxidation methods include air blast drying oxidation (70±5°C), room temperature drying oxidation and closed pure oxygen constant temperature (45±5°C) oxidation.

[0092] In a preferred embodiment, in S7, the oxidation time includes 1 h, 2 h, 4 h, 6 h, 8 h, 10 h and 12 h.

[0093] In a preferred embodiment, in S8, the chart includes a bar chart and a curve chart.

[0094] according to Figure 3In the untreated state, when the concentrations were 400, 500 and 700ug / ml, the inhibition of XOD activity was: green tea < black tea < dark tea; when the concentration was 600ug / ml, the inhibition of XOD activity was: black tea < dark tea < green tea; when the concentration was 800ug / ml, the inhibition of XOD activity was: dark tea < black tea < green tea;

[0095] according to Fig.11 , under the oxidation state of 8h, when the concentration is 400 and 600ug / ml, the inhibition effect on XOD activity is: green tea < black tea < dark tea; when the concentration is 700 and 800ug / ml, the inhibition effect on XOD activity is: black tea < green tea < dark tea; when the concentration is 500ug / ml, the inhibition effect on XOD activity is: dark tea < green tea < black tea;

[0096] In summary, it can be concluded that, with a greater probability, the inhibitory effect of tea water extract of finished tea products on XOD activity is: green tea < black tea < dark tea.

[0097] according to Figure 7 In the figure, the inhibition rate of XOD activity of green tea water extracts at various concentrations under the condition of pure oxygen constant temperature oxidation for 8 hours is at a high level. Therefore, it can be concluded that the oxidation method of pure oxygen constant temperature oxidation for tea leaves has a better inhibitory effect on XOD.

[0098] according to Fig.15 In the figure, the inhibition rate of XOD activity of green tea water extracts at various concentrations under oxidation conditions of 2h and 8h is at a high level. Therefore, it can be concluded that the inhibition of XOD is better when the tea is oxidized for 2h or 8h.

[0099] In summary, it can be concluded that the oxidation method of pure oxygen constant temperature oxidation for 2h or 8h is more effective in inhibiting XOD.

[0100] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A functional tea processing method, characterized in that: The specific steps include: S1: Pick and process tea leaves from June to October in areas above 800 meters above sea level, and perform functional processing on the picked green tea, black tea and dark tea respectively; S2: placing the green tea leaves after withering, the black tea leaves after fermentation and the dark tea leaves in a sealed container filled with pure oxygen, shaking them at a constant speed for a certain period of time under a constant temperature condition, and continuously adding pure water to moisten the tea leaves during the process; S3: Take out green tea leaves, black tea leaves and dark tea leaves respectively, rub and shape them, dry them, and vacuum dry them at 35±5 o C, obtain functional finished green tea A, finished black tea and finished dark tea; in S1, the tea polyphenols, caffeine and tea polysaccharide contents of green tea are 35±5%, 10±2% and 5±1% respectively, the tea polyphenols, caffeine and tea polysaccharide contents of black tea are 20±5%, 5±2% and 8±1% respectively, and the tea polyphenols, caffeine and tea polysaccharide contents of dark tea are 10±5%, 3±1% and 10±2% respectively; in S2, the weights of green tea, black tea and dark tea are 1kg-2kg respectively, and the constant temperature is 45±5 o C, the time of uniform shaking is 1-12h, the amount of pure water added is 100±10 m, and the environment needs to be kept moist during the process.

2. A method for studying the inhibition of XOD activity by leaf water extract, using the method of claim 1, characterized in that: The specific steps include: S1: preparing tea water extracts A of functional finished green tea A, finished black tea and finished dark tea respectively; (1) Weigh 60 g of functional finished green tea A, finished black tea and finished dark tea and put them into 1000 mL beakers with lids respectively; (2) Add 300 mL of pure water to the beaker and boil for 1 h, filter the residue, add 200 mL of pure water and boil for 1 h, filter, and combine the first and second extraction filtrates; (3) The filtrate is vacuum concentrated and then freeze-dried to prepare aqueous extracts of finished green tea A, finished black tea and finished dark tea respectively; S2: preparing green tea, black tea and dark tea water extracts without functional treatment as sample controls, respectively, and the preparation steps are the same as those in S1 above; S3: Construction of xanthine-xanthine oxidase catalytic reaction system and activity inhibition evaluation; (1) Preparation of xanthine solution: 1mmol / L xanthine solution: accurately weigh 0.003g xanthine in 19.723mL pure water, dissolve with ultrasound, and store in dark place; 0.3mmol / L xanthine solution: Measure 6mL of 1mmol / L xanthine solution and dilute to 20mL with 14mL of purified water; (2) Preparation of XOD solution: 0.1mol / L pH=7.5 sodium pyrophosphate buffer: accurately weigh 0.6647g sodium pyrophosphate and 0.0044g ethylenediaminetetraacetic acid, add to pure water and dissolve with ultrasound, transfer to a 25mL volumetric flask and dilute to the mark with pure water, use a pH meter to determine the pH value, if it is not 7.5, adjust the pH to 7.5 with phosphoric acid; 7.2 u / mL XOD solution: accurately weigh 0.001 g xanthine oxidase and dissolve it in 1.194 mL sodium pyrophosphate buffer and store at low temperature away from light; 30 mu / mL XOD solution: Accurately measure 0.083 mL of 7.2 u / mL xanthine oxidase solution and dilute to 20 mL with 19.917 mL of purified water; ； (3) scanning the xanthine-xanthine oxidase catalytic reaction system solution at full wavelength using ultraviolet spectroscopy, and recording the absorbance value A0 at 290±3nm; (4) Evaluation of XOD activity inhibition: Take samples of different concentrations and perform the following test: ； The xanthine-xanthine oxidase catalytic reaction system solution was scanned at full wavelength by ultraviolet spectroscopy, the absorbance value A1 at 290±3nm was recorded, and the XOD activity inhibition rate I was calculated according to the following formula: I(%) = (1- A1 / A0 )X100%; S4: taking the tea water extracts prepared in S1 and S2 respectively, and performing the operation in S3 to measure their inhibitory effects on in vitro XOD activity respectively, and making comparative analysis; S5: Take the summer and autumn green tea leaves, black tea leaves and dark tea leaves after withering, and subject them to the same pure oxygen constant temperature oxidation for 8 hours. Then, evaluate the water extracts of the green tea leaves, black tea leaves and dark tea leaves after oxidation for 8 hours in vitro Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, calculate the activity inhibition rate of different types of tea water extracts on in vitro XOD after oxidation, and determine the best processing raw materials; S6: Take out the summer and autumn green tea leaves after withering, and oxidize them by different methods for 8 hours, then evaluate the tea water extracts of the oxidized green tea in vitro Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, calculate the activity inhibition rate of different types of tea water extracts on in vitro XOD after oxidation, and determine the best oxidation method; S7: Take out the summer and autumn green tea leaves after withering, and oxidize them for different time periods by using a closed pure oxygen constant temperature oxidation method, and then evaluate the green tea leaf water extracts oxidized for different time periods in an in vitro Xan-XOD catalytic reaction system, record the absorbance value A1 at 290±3nm, and calculate the inhibition rate of the tea water extracts oxidized for different time periods on the in vitro XOD activity, and determine the optimal oxidation time; S8: Make the measurement results of S5-7 into corresponding charts, and then make the final judgment result based on the chart information.

3. The method for studying the inhibition of XOD activity by leaf water extract according to claim 2, characterized in that: In S6, the different oxidation methods include air blast drying oxidation, room temperature drying oxidation and closed pure oxygen constant temperature oxidation method.

4. The method for studying the inhibition of XOD activity by leaf water extract according to claim 3, characterized in that: In S7, the oxidation time includes 1 h, 2 h, 4 h, 6 h, 8 h, 10 h and 12 h.

5. The method for studying the inhibition of XOD activity by leaf water extract according to claim 4, characterized in that: In S8, the chart includes a bar chart and a curve chart.

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