A method for extracting flavonoids from Ampelopsis grossedentata and its application in feed additives

Abstract

The present invention belongs to the field of natural product extraction, and particularly relates to a method for extracting flavonoids from Ampelopsis grossedentata. The present invention uses a deep eutectic solvent and an ionic liquid to form an aqueous two-phase system, which has high selectivity for flavonoids in Ampelopsis grossedentata. The extraction rate of flavonoids is as high as 96.6%, and the purity is as high as 98.9%. In addition, the extraction conditions of the present invention are mild, with a low extraction temperature, a short extraction time, and no need to use corrosive reagents such as inorganic salts, which is environmentally friendly and suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of natural product extraction, and particularly relates to a method for extracting flavonoids from Ampelopsis grossedentata and its application in feed additives. Background Art

[0002] Ampelopsis grossedentata is a plant of the genus Ampelopsis in the Vitaceae family, also known as Ampelopsis grossedentata ( Ampelopsis grossedentata ), which has been used as a health tea and Chinese herbal medicine for hundreds of years. This plant is mainly distributed in areas south of the Yangtze River such as Fujian, Yunnan, Guangdong, Guangxi, Guizhou, and Hunan, and is a plant with both medicinal and edible properties. The flavonoids in Ampelopsis grossedentata are mainly divided into flavones, flavonols, isoflavones, flavanones, chalcones, and anthocyanidins, etc. The flavonoids (also known as total flavonoids) in Ampelopsis grossedentata have various pharmacological activities such as anti-inflammatory, antibacterial, hypoglycemic, hypolipidemic, antihypertensive, antioxidant, anti-atherosclerotic, liver-protecting, and anti-tumor effects.

[0003] In addition, flavonoid compounds (also known as total flavonoids) have a strong inhibitory effect on Escherichia coli, Salmonella, and Staphylococcus aureus in the intestine, and at the same time have a powerful ability to scavenge free radicals, can increase the antioxidant capacity of intestinal tissues and the liver, reduce the inflammatory response in the body. Therefore, applying flavonoid compounds as feed additives in livestock and poultry breeding has the effects of improving the production performance of livestock and poultry, enhancing disease resistance and immunity, reducing and preventing the occurrence of digestive tract inflammation, and improving meat quality.

[0004] Currently, the processes for extracting flavonoids from Ampelopsis grossedentata mainly include hot water extraction method, organic solvent extraction method, alkaline water or alkaline dilute alcohol extraction method, high-speed counter-current chromatography extraction method, supercritical carbon dioxide extraction method, enzyme extraction method, etc.

[0005] CN109692248A discloses a method for extracting total flavonoids from Ampelopsis grossedentata, which overcomes the disadvantages of high extraction temperature and difficult separation and purification in the conventional alcohol extraction method. However, the above method requires the use of biological enzymes, and the extraction rate and purity are very low.

[0006] CN106581319A discloses an ultrasonic extraction process for total flavonoids from Ampelopsis grossedentata, which comprises the following process steps: (1) drying and pulverizing the stems and leaves of fresh Ampelopsis grossedentata, screening through a 20-100 mesh sieve to obtain Ampelopsis grossedentata coarse powder; (2) adding ethanol with a volume fraction of 60-80% to the Ampelopsis grossedentata coarse powder according to a material-liquid ratio of Ampelopsis grossedentata coarse powder: ethanol of 1:25-35 for soaking; (3) performing ultrasonic extraction 1-3 times after soaking for 20-40 min, 20-40 min each time, filtering and combining the filtrates to obtain an ultrasonic extraction solution of total flavonoids from Ampelopsis grossedentata, and the yield of total flavonoids is 35-40%. However, the above method still has the problem of low extraction rate, and the extraction time is long and the efficiency is low, which is not suitable for industrial production.

[0007] CN101810735A discloses a method for extracting total flavonoids from Ampelopsis grossedentata, which comprises the following steps: (1) soaking dry leaves of Ampelopsis grossedentata in an alcohol solvent for 1-5 hours; (2) filtering the above alcohol solution, subjecting the filter residue to microwave radiation treatment, then combining it with the filtrate, adding them all to water at 85-100 °C, and heating and extracting at 85-100 °C for 50-140 minutes; (3) filtering the above extraction solution, concentrating the filtrate to 1 / 3-1 / 4 of its volume, then adding water thereto and crystallizing and separating at 0-10 °C. However, the above method has a high extraction temperature, a long extraction time, and a low extraction rate of total flavonoids.

[0008] Based on the problems of harsh extraction conditions, low extraction rate, and low flavonoid purity existing in the prior art, it is urgent to develop a new method for extracting flavonoids from Ampelopsis grossedentata. Summary of the Invention

[0009] Aiming at the deficiencies existing in the prior art, the present invention aims to provide a method for extracting flavonoids from Ampelopsis grossedentata, which has mild extraction conditions, high extraction rate, and high flavonoid purity. To achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for extracting flavonoids from Ampelopsis grossedentata, comprising the following steps:

[0011] Step 1): drying and pulverizing the fresh stems and leaves of Ampelopsis grossedentata, screening through a 50-100 mesh sieve to obtain Ampelopsis grossedentata coarse powder, and storing it in the dark for standby;

[0012] Step 2): mixing a hydrogen bond acceptor and a hydrogen bond donor evenly and heating, then adding deionized water to obtain an aqueous solution of a deep eutectic solvent for standby; adding deionized water to an ionic liquid to obtain an aqueous solution of the ionic liquid for standby;

[0013] Step 3): sequentially adding the aqueous solution of the deep eutectic solvent and the aqueous solution of the ionic liquid described in Step 2) to the Ampelopsis grossedentata coarse powder; performing ultrasonic extraction and then standing for stratification, and separating the upper ionic liquid phase containing flavonoids;

[0014] Step 4): Extract the ionic liquid phase described in step 3) with ethyl acetate, separate the ethyl acetate phase, and obtain flavonoids by concentration under reduced pressure and vacuum drying.

[0015] Among them, the structure of the ionic liquid described in step 2) is: .

[0016] In some embodiments, the hydrogen bond acceptor described in step 2) is benzyltriethylammonium chloride, and the hydrogen bond donors are ethanolamine, diethanolamine or triethanolamine; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(2 - 5).

[0017] In some embodiments, the water content of the aqueous solution of the deep eutectic solvent described in step 2) is 30wt% - 60wt%; the water content of the aqueous solution of the ionic liquid is 30wt% - 60wt%.

[0018] In some embodiments, the mass - to - volume ratio of the crude Ampelopsis grossedentata powder to the aqueous solution of the deep eutectic solvent is 1g:(5 - 10)mL; the mass - to - volume ratio of the crude Ampelopsis grossedentata powder to the aqueous solution of the ionic liquid is 1g:(5 - 10)mL.

[0019] In some embodiments, the ultrasonic extraction temperature in step 3) is 30 - 50°C and the extraction time is 10 - 20 min.

[0020] In some embodiments, a method for extracting flavonoids from Ampelopsis grossedentata includes the following steps:

[0021] Step 1): Dry and crush the fresh Ampelopsis grossedentata stems and leaves, pass through a 50 - mesh sieve to obtain the crude Ampelopsis grossedentata powder, and keep it in the dark for later use.

[0022] Step 2): Place benzyltriethylammonium chloride and ethanolamine in a beaker at a molar ratio of 1:4, stir magnetically at 70°C until the system becomes a clear, transparent and viscous liquid, then cool to 25°C, add deionized water to make the water content of the system 40wt%, which is the aqueous solution of the deep eutectic solvent, and keep it for later use; add the ionic liquid to the beaker, add deionized water to make the water content of the system 50wt%, which is the aqueous solution of the ionic liquid, and keep it for later use.

[0023] Step 3): Weigh 10g of the crude Ampelopsis grossedentata powder into a conical flask, add 50mL of the aqueous solution of the deep eutectic solvent described in step 2) and 100mL of the aqueous solution of the ionic liquid; seal it and place it in a constant - temperature water bath, ultrasonicate for 10 min under the conditions of 30°C and 100W, let it stand for stratification, and separate the upper ionic liquid phase containing flavonoids.

[0024] Step 4: Take the ionic liquid phase obtained in step 3), add 300mL of ethyl acetate for extraction, separate the ethyl acetate phase, and obtain flavonoids by concentration under reduced pressure and vacuum drying.

[0025] In some embodiments, a method for extracting flavonoids from Ampelopsis grossedentata includes the following steps:

[0026] Step 1): Dry and crush the fresh stems and leaves of Ampelopsis grossedentata, sieve through a 100-mesh sieve to obtain coarse Ampelopsis grossedentata powder, and keep it in the dark for later use;

[0027] Step 2): Place benzyltriethylammonium chloride and triethanolamine in a beaker according to a molar ratio of 1:2, magnetically stir at 70 °C until the system becomes a clear, transparent and viscous liquid, then cool to 25 °C, add deionized water to make the water content of the system 60 wt%, which is the aqueous solution of the deep eutectic solvent, and keep it for later use; Add the ionic liquid to the beaker, add deionized water to make the water content of the system 50 wt%, which is the aqueous solution of the ionic liquid, and keep it for later use;

[0028] Step 3): Weigh 10 g of the coarse Ampelopsis grossedentata powder into a conical flask, add 50 mL of the aqueous solution of the deep eutectic solvent and 100 mL of the aqueous solution of the ionic liquid described in Step 2); Seal and place it in a constant temperature water bath, ultrasonically treat for 10 min under the conditions of 30 °C and 100 W, let it stand for stratification, and separate the upper ionic liquid phase containing flavonoids;

[0029] Step 4): Take the ionic liquid phase obtained in Step 3), add 300 mL of ethyl acetate for extraction, separate the ethyl acetate phase, and obtain flavonoids through reduced pressure concentration and vacuum drying.

[0030] On the other hand, the present invention also protects the application of the flavonoids extracted by the above method as a feed additive.

[0031] In some embodiments, the flavonoids extracted by the present invention have a strong inhibitory effect on Escherichia coli, Salmonella and Staphylococcus aureus in the intestine, and at the same time have a strong ability to scavenge free radicals, can increase the antioxidant capacity of intestinal tissues and the liver, reduce the in vivo inflammatory response, and can be widely used in livestock and poultry breeding, with the effects of improving the production performance of livestock and poultry, enhancing disease resistance and immunity, reducing and decreasing the occurrence of digestive tract inflammation, and improving meat quality.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1) The present invention uses a deep eutectic solvent and an ionic liquid to form a two-aqueous-phase system, which has high selectivity for flavonoids in Ampelopsis grossedentata, enabling flavonoids to be selectively enriched in the ionic liquid phase. The extraction rate of flavonoids in the present invention is as high as 96.6% and the purity is as high as 98.9%.

[0034] 2) The extraction conditions of the present invention are mild, with a low extraction temperature and a short extraction time, and there is no need to use corrosive reagents such as inorganic salts, which is environmentally friendly and suitable for industrial production. Detailed implementation manners

[0035] The following non-limiting examples can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way. The following content is merely an exemplary illustration of the scope claimed by the present invention. Those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes and modifications should also fall within the scope claimed by the present invention.

[0036] When the examples give a numerical range, it should be understood that unless otherwise specified in the present invention, any value at both ends of each numerical range and any value between the two ends can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0037] The present invention will be further described below by way of specific examples. All kinds of chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified.

[0038] Flavonoid extraction rate = mass of extracted flavonoid / mass of flavonoid in Ampelopsis grossedentata × 100%;

[0039] Flavonoid purity = mass of flavonoid in the extract / mass of the extract × 100%.

[0040] Among them, the method for measuring the content of flavonoid in the Ampelopsis grossedentata sample and the extract is as follows: Using dihydromyricetin as the standard, the content of flavonoid is measured by Al(Cl) 3 spectrophotometry. The method can refer to "Xiong Haoping, Determination of total flavonoids in Ampelopsis grossedentata by spectrophotometry, Food Science, Vol. 25, No. 2, 2004".

[0041] Example 1 Preparation of ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2

[0042] Step 1: Preparation of [C 4 (C 2 H 5 Oim) 2 [Br] 2

[0043] ;

[0044] Add 1,4-bis(1-imidazole)butane (0.1 mol), 2-bromoethanol (0.25 mol), and N,N-dimethylformamide (100 mL) to the reactor, heat up to 80 °C and stir for 48 h. After the reaction is completed, add ether (300 mL) to the reaction mixture to form a precipitate, filter and dry to obtain a white solid [C4 (C 2 H 5 Oim) 2 [Br] 2 , with a yield of 80.3%.

[0045] Step 2: Preparation of ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 ;

[0046]

[0047] Dissolve the C 4 (C 2 H 5 Oim) 2 (Br) 2 (0.1 mol) obtained in Step 1 in distilled water (100 mL), and use an anion exchange resin to exchange the original anion in the ionic liquid with hydroxide ions to obtain the [C 4 (C 2 H 5 Oim) 2 [OH] 2 intermediate. Then, add acetic acid (0.3 mol) to the [C 4 (C 2 H 5 Oim) 2 [OH] 2 intermediate, and raise the temperature to 40 °C and stir for 48 h. After the reaction is completed, rotate and evaporate to remove the distilled water. Dissolve the obtained crude product in THF and wash it repeatedly to remove the excess acetic acid. Then, dry it under vacuum to obtain the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 , with a yield of 95.8%.

[0048] 1 H-NMR (400 MHz, DMSO- d 6 ): δ(ppm): 9.58(s, 2H), 7.84(s 2H), 7.75(s2H), 4.33 - 4.24(m, 8H), 3.69 (t, 6H), 1.78 - 1.72(m, 4H), 1.60(s, 6H).

[0049] Example 1

[0050] ​A method for extracting flavonoids from Ampelopsis grossedentata, comprising the following steps:

[0051] Step 1): Dry and crush the fresh Ampelopsis grossedentata stems and leaves, pass through a 50-mesh sieve to obtain the crude Ampelopsis grossedentata powder, and keep it in the dark for later use;

[0052] Step 2): Place benzyltriethylammonium chloride and ethanolamine in a beaker according to a molar ratio of 1:4, magnetically stir at 70 °C until the system becomes a clear, transparent and viscous liquid, then cool to 25 °C, add deionized water to make the water content of the system 40 wt%, which is the aqueous solution of the eutectic solvent, and keep it for later use; Add the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 obtained in Preparation Example 1 into the beaker, add deionized water to make the water content of the system 50 wt%, which is the aqueous solution of the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 , and keep it for later use.

[0053] Step 3): Weigh 10 g of the crude Ampelopsis grossedentata powder into a conical flask, add 50 mL of the aqueous solution of the eutectic solvent described in Step 2 and 100 mL of the aqueous solution of the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 . Seal and place it in a constant temperature water bath, ultrasonicate for 10 min under the conditions of 30 °C and 100 W, let it stand for layer separation, and separate the upper ionic liquid phase containing flavonoids.

[0054] Step 4): Take the ionic liquid phase obtained in Step 3, add 300 mL of ethyl acetate for extraction, separate the ethyl acetate phase, and obtain the flavonoid product through reduced pressure concentration and vacuum drying. The extraction rate is 96.6% and the flavonoid purity is 98.9%.

[0055] Example 2

[0056] A method for extracting flavonoids from Ampelopsis grossedentata, comprising the following steps:

[0057] Step 1): Dry and crush the fresh Ampelopsis grossedentata stems and leaves, pass through a 70-mesh sieve to obtain the crude Ampelopsis grossedentata powder, and keep it in the dark for later use;

[0058] Step 2): Place benzyltriethylammonium chloride and diethanolamine in a beaker in a molar ratio of 1:3, magnetically stir at 70 °C until the system becomes a clear, transparent and viscous liquid, then cool to 25 °C, add deionized water to make the water content of the system 50 wt%, which is the aqueous solution of the deep eutectic solvent, and set aside; Add the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 obtained in Preparation Example 1 into the beaker, add deionized water to make the water content of the system 60 wt %, which is the aqueous solution of the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 , and set aside.

[0059] Step 3): Weigh 10 g of gross Ampelopsis grossedentata powder into a conical flask, add 50 mL of the aqueous solution of the deep eutectic solvent described in Step 2 and 100 mL of the aqueous solution of the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 . Seal and place it in a constant temperature water bath, ultrasonicate for 10 min under the conditions of 30 °C and 100 W, let it stand for layering, and separate the upper ionic liquid phase containing flavonoids.

[0060] Step 4): Take the ionic liquid phase obtained in Step 3, add 300 mL of ethyl acetate for extraction, separate the ethyl acetate phase, and obtain the flavonoid product through reduced pressure concentration and vacuum drying, with an extraction rate of 95.1% and a flavonoid purity of 98.6%.

[0061] Example 3

[0062] A method for extracting flavonoids from Ampelopsis grossedentata, comprising the following steps:

[0063] Step 1): Dry and crush fresh Ampelopsis grossedentata stems and leaves, pass through a 100-mesh sieve to obtain gross Ampelopsis grossedentata powder, and set aside in the dark;

[0064] Step 2): Place benzyltriethylammonium chloride and triethanolamine in a beaker in a molar ratio of 1:2, magnetically stir at 70 °C until the system becomes a clear, transparent and viscous liquid, then cool to 25 °C, add deionized water to make the water content of the system 60 wt%, which is the aqueous solution of the deep eutectic solvent, and set aside; Add the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2Add it to a beaker and add deionized water to make the water content of the system 50 wt%, which is the aqueous solution of the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 . Set it aside for later use.

[0065] Step 3): Weigh 10 g of crude Ampelopsis grossedentata powder into a conical flask, add 50 mL of the aqueous solution of the eutectic solvent described in Step 2, and 100 mL of the aqueous solution of the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 . Seal it and place it in a constant temperature water bath. Ultrasonic it for 10 min under the conditions of 30 °C and 100 W, let it stand for layering, and separate the upper ionic liquid phase containing flavonoids.

[0066] Step 4): Take the ionic liquid phase obtained in Step 3, add 300 mL of ethyl acetate for extraction, separate the ethyl acetate phase, and obtain the flavonoid product through reduced pressure concentration and vacuum drying. The extraction rate is 94.4% and the flavonoid purity is 98.8%.

[0067] Comparative Example 1

[0068] On the basis of Example 1, replace the ionic liquid [C 4 (C 2 H 5 Oim) 2 [Ac] 2 with 1-butyl-3-methylimidazolium trifluoroacetate, and the other operation steps and conditions are the same as those in Example 1.

[0069] The results show that the extraction rate of flavonoids is 84.7% and the flavonoid purity is 95.2%.

[0070] Comparative Example 2

[0071] On the basis of Example 1, replace benzyltriethylammonium chloride with choline chloride, and the other operation steps and conditions are the same as those in Example 1.

[0072] The results show that the extraction rate of flavonoids is 89.3% and the flavonoid purity is 96.5%.

[0073] Comparative Example 3

[0074] On the basis of Example 1, replace ethanolamine with ethylene glycol, and the other operation steps and conditions are the same as those in Example 1.

[0075] The results show that the extraction rate of flavonoids is 90.2% and the flavonoid purity is 97.6%.

[0076] The above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to list all implementation manners here. Thus, the obvious changes or alterations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for extracting flavonoids from rattan tea, comprising the following steps: Step 1): Dry the fresh stems and leaves of Ampelopsis ulmoides and crush them, pass through a 50-100 mesh sieve to obtain Ampelopsis ulmoides coarse powder, and keep it away from light for later use; Step 2): Mix the hydrogen bond acceptor and the hydrogen bond donor evenly and heat them, then add deionized water to obtain an aqueous solution of a low eutectic solvent for later use; add deionized water to the ionic liquid to obtain an aqueous solution of the ionic liquid for later use; Step 3): adding the aqueous solution of the low eutectic solvent and the aqueous solution of the ionic liquid in step 2) to the crude powder of rattan tea in sequence; standing and stratifying after ultrasonic extraction, separating the upper ionic liquid phase containing flavonoids; Step 4): extracting the ionic liquid phase in step 3) with ethyl acetate, separating the ethyl acetate phase, concentrating under reduced pressure, and vacuum drying to obtain flavonoids; Wherein, the structure of the ionic liquid in step 2) is: ; Step 2) the hydrogen bond acceptor is benzyltriethylammonium chloride, the hydrogen bond donor is ethanolamine, diethanolamine or triethanolamine; the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:(2-5).

2. The method according to claim 1, characterized in that: Step 2) The water content of the aqueous solution of the low eutectic solvent is 30wt%~60wt%; the water content of the aqueous solution of the ionic liquid is 30wt%~60wt%.

3. The method according to claim 1, characterized in that The mass volume ratio of the crude powder of rattan tea to the aqueous solution of the low eutectic solvent is 1g:(5~10)mL; the mass volume ratio of the crude powder of rattan tea to the aqueous solution of the ionic liquid is 1g:(5~10)mL.

4. The method according to claim 1, characterized in that The ultrasonic extraction temperature of step 3) is 30-50°C and the extraction time is 10-20 minutes.

5. The method according to claim 1, characterized in that The following steps are involved: Step 1): Dry the fresh stems and leaves of Rhizoma Atractylodis Macrocephalae and crush them, pass through a 50-mesh sieve to obtain coarse powder of Rhizoma Atractylodis Macrocephalae and keep it away from light for later use; Step 2): Benzyltriethylammonium chloride and ethanolamine are placed in a beaker at a molar ratio of 1:4, and magnetically stirred at 70°C until the system becomes a clear, transparent viscous liquid, then cooled to 25°C, and deionized water is added to make the water content of the system 40wt%, which is an aqueous solution of a low eutectic solvent, which is set aside; the ionic liquid is added to the beaker, and deionized water is added to make the water content of the system 50wt%, which is an aqueous solution of the ionic liquid, which is set aside; Step 3): Weigh 10g of rattan tea crude powder into a conical flask, add 50mL of the aqueous solution of the low eutectic solvent in step 2) and 100mL of the aqueous solution of the ionic liquid; seal and place in a constant temperature water bath, ultrasonicate for 10min at 30°C and 100W, stand and separate, and separate the upper ionic liquid phase containing flavonoids; Step 4: Take the ionic liquid phase obtained in step 3, add 300 mL of ethyl acetate for extraction, separate the ethyl acetate phase, concentrate under reduced pressure, and vacuum dry to obtain flavonoids.

6. The method according to claim 1, characterized in that The following steps are involved: Step 1): Dry the fresh stems and leaves of Ampelopsis ulmoides and crush them, pass through a 100-mesh sieve to obtain Ampelopsis ulmoides coarse powder, and keep it away from light for later use; Step 2): Benzyltriethylammonium chloride and triethanolamine are placed in a beaker at a molar ratio of 1:2, and magnetically stirred at 70°C until the system becomes a clear, transparent viscous liquid, then cooled to 25°C, and deionized water is added to make the water content of the system 60wt%, that is, an aqueous solution of a low eutectic solvent, which is set aside; the ionic liquid is added to the beaker, and deionized water is added to make the water content of the system 50wt%, that is, an aqueous solution of the ionic liquid, which is set aside; Step 3): Weigh 10g of rattan tea crude powder into a conical flask, add 50mL of the aqueous solution of the low eutectic solvent in step 2) and 100mL of the aqueous solution of the ionic liquid; seal and place in a constant temperature water bath, ultrasonicate for 10min at 30°C and 100W, stand and separate, and separate the upper ionic liquid phase containing flavonoids; Step 4): Take the ionic liquid phase obtained in step 3), add 300 mL of ethyl acetate for extraction, separate the ethyl acetate phase, concentrate under reduced pressure, and vacuum dry to obtain flavonoids.

7. Use of flavonoids extracted by the method of any one of claims 1 to 6 as feed additive.

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