Preparation method of typical bamboo leaf C-glycoside flavone magnetic molecularly imprinted polymer

Abstract

The invention relates to the technical field of plant processing, in particular to a preparation method of a typical bamboo leaf C-glycoside flavone magnetic molecularly imprinted polymer. The preparation method comprises the following steps: designing bamboo leaf carbon glycoside flavone as a template molecule, and preparing a magnetic molecularly imprinted nano polymer MIP with a core-shell structure by adopting a surface molecular imprinting technology; the characterization of TEM, XRD, VSM, FT-IR and the like proves that the prepared MIP is successfully synthesized, and the satisfactory adsorption capacity (for template molecules of 16.10 mg / g) is obtained. The MIP is added into the bamboo leaf flavonoid crude extract, and the total flavonoid content obtained after adsorption is increased from 24% to 90% or above. Six flavonoid compounds are detected from the high-purity flavonoids through HPLC (High Performance Liquid Chromatography), and four C-glycoside flavonoids account for 90.73%; the content of the rubisoside and the isorubisoside is 33-40%, the content of the vitexin and the isovitexin is 40-48%, and the value and the biological activity of the bamboo leaf flavonoid extract are remarkably increased.

Description

Technical Field

[0001] The present invention relates to the technical field of plant processing. More specifically, the present invention relates to a method for designing and synthesizing a magnetic molecularly imprinted polymer using a typical C-glycosyl flavonoid as a template molecule and a method for selectively enriching high-purity C-glycosyl flavonoid compounds. Background Art

[0002] Flavonoids are organic compounds present in plants with various physiological functions, such as antioxidant, anti-inflammatory, antibacterial, antiviral, and antitumor effects, and can be used to prevent the occurrence of various diseases such as cardiovascular diseases and cancer and to treat inflammatory diseases such as arthritis and gout. Utilizing the high affinity of molecularly imprinted polymers for flavonoids as adsorbents to identify flavonoid compounds from complex natural extracts to obtain high-purity natural total flavonoids has broad application prospects in the fields of functional foods, medicine, and daily chemicals.

[0003] Bamboo leaves, as a natural plant with both medicinal and edible uses, have a long history and wide application value in China. It contains rich beneficial components such as flavonoid compounds, polysaccharides, special amino acids, and trace elements. Bamboo leaf flavonoids (BLF) mainly exist in the forms of orientin, isoorientin, vitexin, and isovitexin, and have various effects such as anti-myocardial ischemia, anti-aging, antioxidant, and antibacterial effects. Bamboo leaf flavonoids are C-glycosyl flavonoids, in which the glycosyl group is connected to the flavonoid nucleus by a C-C bond. Compared with conventional O-glycosyl flavonoids, it has the following advantages: 1. Stable structure, not easily degraded, can be stored for a long time. The flavonoid C-glycoside is connected by a C-C bond, not easily undergoing electron shift or chemical bond cleavage, and the structure is relatively stable; 2. Enhanced hydrophilicity, easy to diffuse in the human body or animal body, facilitating the research and development of health foods or drugs; 3. Can penetrate deep into the lesion site and directly exert the drug effect.

[0004] Obtaining high-purity BLF can significantly improve the value of the extract. Exploring more efficient and more environmentally friendly methods for extracting and purifying BLF is the research focus. Commonly used methods for purifying BLF include techniques such as resin adsorption method, column chromatography, and membrane separation method. However, these methods have the disadvantages of consuming a large amount of time and organic solvents and poor selectivity. At the same time, there is a lack of innovative research on the selective enrichment and application of C-glycosyl flavonoids such as orientin, isoorientin, vitexin, and isovitexin in bamboo leaves. Magnetic molecularly imprinted polymers (MIP) have attracted extensive attention in extraction and separation due to their excellent biocompatibility, low toxicity, high strength and durability, superparamagnetism, and rapid separation ability. In view of this, the purpose of the present invention is to study the obtaining of high-purity bamboo leaf C-glycosyl flavonoids from natural bamboo leaf extracts, and a preparation method of a magnetic molecularly imprinted polymer of typical bamboo leaf C-glycosyl flavonoids is designed, providing a rapid, reliable, and economical method for the separation and enrichment of bamboo leaf flavonoid compounds, which has important practical value for the research of active ingredients in traditional Chinese medicine. Summary of the Invention

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] 1. Preparation of magnetic particles for a typical carbon-glycoside flavonoid magnetic molecularly imprinted polymer from bamboo leaves includes:

[0007] 1) Preparation and characterization of Fe3O4 nanoparticles: Dissolve 1 part of FeCl3·6H2O in ethylene glycol with a concentration of 15 - 30 g / L. Add 0.5 - 2 parts of polyethylene glycol to the solution. Ultrasonic dispersion is preferably 30 min. To make the solution mix more evenly, add 3 - 6 parts of anhydrous sodium acetate. After stirring the solution until it is clear and transparent, transfer the solution to a reaction kettle and react at preferably 180 - 200 °C for 8 - 10 h. Then wash it alternately with water and absolute ethanol 3 - 5 times and dry it under vacuum at 40 - 80 °C to obtain Fe3O4 nanoparticles with a particle size maintained at 50 - 200 nm;

[0008] 2) Preparation and characterization of Fe3O4@SiO2 nanoparticles: Add the Fe3O4 nanoparticles obtained in step 1) to an ethanol solution with a mass concentration of 40 - 80%, with a concentration of 1 - 3 g / L. Ultrasonic dispersion is preferably 30 min to make the Fe3O4 disperse more evenly. Add 1 - 5 mL of ammonia water to the solution. After stirring for 10 - 30 min, dropwise add 1 - 5 mL of tetraethyl orthosilicate drop by drop under the liquid surface. React this mixture at 40 - 50 °C and 300 - 500 r / min for 12 - 24 h. After magnetic separation, wash it alternately with absolute ethanol and water 3 times and dry it under vacuum at 40 - 60 °C to obtain Fe3O4@SiO2 nanoparticles with a particle size in the range of 50 - 200 nm.

[0009] 3) Functional modification and characterization of Fe3O4@SiO2 nanoparticles: Disperse the Fe3O4@SiO2 nanoparticles in a 50 - 80% ethanol solution, ultrasonic for 10 - 30 min, add 5 - 10 mL of ammonia water, add a modifier, mechanically stir at 200 - 500 r / min, and react at 60 - 80 °C for 12 - 24 h. After magnetic separation, obtain a black solid, wash it with ethanol 4 - 5 times, and dry it under vacuum at 40 - 60 °C to obtain modified Fe3O4@SiO2 magnetic nanoparticles with a particle size maintained at 50 - 300 nm.

[0010] 4) Magnetic molecularly imprinted polymer MIP of typical carbon-glycoside flavonoids from bamboo leaves. The template molecule of carbon-glycoside flavonoids from bamboo leaves and the functional monomer are dispersed in a solvent at a molar ratio of 1:4 to 1:8, and stored at 4 °C for 5 to 12 h to obtain a prepolymer solution. Preferably, it is stored for 10 to 12 h to make the self-assembly reaction more complete. Then, modified Fe3O4@SiO2 particles and a crosslinking agent are added. The molar ratio of the template molecule to the crosslinking agent is 1:10 to 1:50. An initiator is added under nitrogen protection, and the molar ratio of the template molecule to the initiator is 1:1 to 1:3. After nitrogen is introduced for 10 to 30 min, it is sealed and polymerized at 50 to 70 °C. The reaction product is washed with a methanol-acetic acid mixture until the ultraviolet absorption peak of the template molecule cannot be detected in the eluent. Then, it is dried in vacuum at 40 to 60 °C to obtain the magnetic molecularly imprinted polymer MIP of typical carbon-glycoside flavonoids from bamboo leaves, and the particle size is kept at 50 to 300 nm.

[0011] 2. According to the method described in claim 1, the template molecule is characterized in that it is at least one of carbon-glycoside flavonoids such as orientin, isoorientin, vitexin or isovitexin, and the molecular weight is in the range of 400 to 500.

[0012] 3. According to the method described in claim 1, the functional monomer is characterized in that it is a monomer compound with a conjugated double bond, preferably one of acrylic acid, 2-vinylpyridine, 4-vinylpyridine or methacrylic acid.

[0013] 4. According to the method described in claim 1, the initiator is characterized in that it is azobisisobutyronitrile or benzoyl peroxide. Preferably, the initiator is azobisisobutyronitrile; the crosslinking agent is ethylene glycol dimethacrylate or butyl acrylate. Preferably, the crosslinking agent is ethylene glycol dimethacrylate; the solvent is acetonitrile or methanol.

[0014] 5. According to the method described in claim 1, the mixture is characterized in that it is a mixture of methanol and acetic acid in a volume ratio of 7:3 to 9:1.

[0015] 6. According to the method described in claim 1, the enriched and prepared carbon-glycoside flavonoids from bamboo leaves are characterized in that: a crude flavonoid extract from bamboo leaves with a mass fraction of 15 to 25% is mixed with the magnetic molecularly imprinted polymer MIP. After adsorption, the MIP is eluted, and the eluent is analyzed by HPLC to obtain 6 flavonoid compounds, including 4 flavonoid glycoside compounds; the total flavonoid content is increased to more than 90%; the content of orientin and isoorientin is 33 to 40%, and the content of vitexin and isovitexin is 40 to 48%; the molecularly imprinted polymer is the magnetic molecularly imprinted polymer of typical carbon-glycoside flavonoids from bamboo leaves described in claim 1, and the 6 flavonoid glycoside compounds are luteolin, orientin, isoorientin, apigenin, vitexin and isovitexin.

[0016] The present invention has the following beneficial effects:

[0017] 1. In the present invention, the magnetic molecularly imprinted polymer MIP can selectively adsorb high-purity C-glycosyl flavonoids (the ratio of C-glycosyl flavonoids to non-C-glycosyl flavonoids is close to 90:10), and increase the total flavonoid content to more than 90%.

[0018] 2. The designed magnetic molecularly imprinted polymer MIP of the present invention can adsorb and separate 6 flavonoid compounds, among which 4 flavonoid glycoside compounds, the contents of orientin and isoorientin are 33 - 45%, and the contents of vitexin and isovitexin are 40 - 48%, significantly increasing the value and biological activity of flavonoid extracts.

[0019] 3. The magnetic molecularly imprinted nanomaterial MIP prepared in the present invention has good reusability and thermal stability, which conforms to the development concept of green chemistry and chemical engineering; the synthesis is simple, the yield is high, and it is suitable for large-scale production and application; it can be rapidly separated under an external magnetic field, and the application of surface imprinting technology can effectively avoid the problem of product loss caused by the embedding of binding sites and achieve rapid mass transfer. Description of the Drawings

[0020] Figure 1 Schematic diagram of the preparation and application of MIP;

[0021] Figure 2 TEM images of magnetic particles Fe3O4 (a), Fe3O4@SiO2 (b), and MIP (c);

[0022] Figure 3 FT-IR spectra (a) of magnetic particles Fe3O4, Fe3O4@SiO2, MIP, and NIP; VSM curves (b) of magnetic particles Fe3O4, Fe3O4@SiO2, and MIP; XRD patterns (c) of magnetic particles Fe3O4, Fe3O4@SiO2, and MIP;

[0023] Figure 4 Isothermal adsorption curve of MIP for vitexin;

[0024] Figure 5 Adsorption kinetic curve of MIP for vitexin;

[0025] Figure 6 Selective adsorption of MIP and NIP for orientin, isoorientin, vitexin, isovitexin, and other competing compounds;

[0026] Figure 7 Comparison of HPLC chromatograms of the initial crude extract of bamboo leaf flavonoids, the solution after adding MIP, and the methanol eluate, (a) orientin, (b) isoorientin, (c) vitexin, (d) isovitexin, (e) luteolin, (f) apigenin. Detailed Embodiments

[0027] The present invention will be further described below in conjunction with embodiments. The following embodiments are illustrative and not restrictive, and the protection scope of the present invention cannot be limited by the following embodiments.

[0028] Example 1

[0029] 1) Preparation of Fe3O4 nanoparticles

[0030] Dissolve 1 part of FeCl3·6H2O in ethylene glycol, with a preferred concentration of 15 - 18 g / L. Add 0.8 part of polyethylene glycol to the solution and disperse it ultrasonically for 15 min. Add 3 - 4 parts of anhydrous sodium acetate, stir the solution until it is clear and transparent, then transfer the solution to a 200 mL reaction kettle and react at 200 °C for 10 h. Perform magnetic separation and wash it alternately with water and absolute ethanol 3 times. After vacuum drying at 40 °C for 2 h, Fe3O4 nanoparticles are obtained.

[0031] 2) Preparation of Fe3O4@SiO2 nanoparticles

[0032] Add Fe3O4 particles to an 80% ethanol - water mixed solution, with a preferred concentration of 1 g / L, and disperse it ultrasonically for 10 min. Add 5 mL of ammonia water to the solution, stir for 10 min, and then dropwise add 1.5 mL of tetraethyl orthosilicate drop by drop under the liquid surface. React the mixture at 45 °C and 500 r / min for 12 h, perform magnetic separation, wash it alternately with absolute ethanol and water 3 times, and vacuum dry at 40 °C for 2 h to obtain Fe3O4@SiO2 nanoparticles.

[0033] 3) Preparation of modified nanoparticles

[0034] Take 0.2 g of Fe3O4@SiO2 nanoparticles, add 40 mL of ultrapure water and 160 mL of absolute ethanol, ultrasonicate for 10 min, add 10 mL of ammonia water and 2 mL of a modifier. The preferred modifier is 3 - (Trimethoxysilyl)propyl methacrylate (MPS). Stir mechanically at 250 r / min and react at 60 °C for 24 h. After magnetic separation, a black solid is obtained, washed 4 - 5 times with ethanol, and vacuum dried at 40 °C for 2 h to obtain the powder Fe3O4@SiO2@MPS.

[0035] 4) Preparation of magnetic molecularly imprinted polymer MIP

[0036] Dissolve 43.2 mg of vitexin in 15 mL of methanol by ultrasonic treatment for 10 min, add 63.6 μL of MMA and ultrasonic for 20 min, and store at 4 °C for 12 h. Place 0.1 g of Fe3O4@SiO2@MPS nanoparticles in 25 mL of acetonitrile solvent, ultrasonic for 15 min, then add the prepolymer solution and mix evenly, and react at room temperature for 3 h. Then add 3 mmol of crosslinking agent and 40 mg of initiator. The crosslinking agent is ethylene glycol dimethacrylate and the initiator is azobisisobutyronitrile. After purging with nitrogen for 30 min, seal and react at 60 °C for 24 h. Use a methanol - acetic acid (volume ratio 9:1) mixed solution as the solvent, and elute the product by Soxhlet extraction until no ultraviolet absorption peak can be detected in the eluent, that is, the template molecule in the molecularly imprinted polymer has been removed. Then wash with methanol until neutral, and dry in vacuum at 40 °C for 2 h to obtain magnetic imprinted polymer (MMIP). Without adding the template molecule vitexin, prepare magnetic non - imprinted polymer (NIP) in the same way.

[0037] The schematic diagram of the preparation and application of the magnetic molecularly imprinted polymer MIP prepared in this example is as Figure 1 , and the structural characterization results are as follows: (1) Transmission electron microscope image (TEM)

[0038] Figure 2 The TEM photos of magnetic particles Fe3O4, Fe3O4@SiO2 and MIP are shown. It can be observed from the figure that the magnetic particle Fe3O4 is spherical or square, and both Fe3O4@SiO2 and MIP are spherical. Compared with Figure 2 (a), Figure 2 (b) has an additional light - colored outer layer, which is formed by the encapsulation of SiO2, indicating the successful preparation of Fe3O4@SiO2. The imprinted polymer MIP shows an obvious core - shell structure, and the nanoparticle core is completely wrapped by the imprinted polymer shell layer, proving the successful preparation of the flavonoid magnetic molecularly imprinted polymer.

[0039] (2) Fourier transform infrared spectroscopy (FT - IR)

[0040] The results are shown in Figure 3 , and magnetic particles Fe3O4, Fe3O4@SiO2, modified Fe3O4@SiO2 particles, MIP, and NIP are characterized by FT - IR. From Figure 3As can be seen, Fe3O4 and Fe3O4@SiO2 have strong absorption peaks at 571 and 576 cm-1 respectively, which correspond to the characteristic stretching absorption peaks of Fe-O in Fe3O4. In addition, Fe3O4@SiO2 has a strong absorption peak at 1089 cm-1, which is produced by the stretching vibration of Si-O-R or Si-O-Si, indicating that SiO2 has been successfully modified on the surface of Fe3O4 particles. For MIP and NIP, 1131 cm-1 corresponds to C-O-C, and 1630 and 1724 cm-1 correspond to C=C and C=O respectively, which are derived from the reaction raw materials AIBN, MMA, and EGDMA, indicating that the polymerization reaction is successful.

[0041] (3) VSM analysis

[0042] Figure 2 b shows the VSM curves of Fe3O4, Fe3O4@SiO2, and MIP. As can be seen from the figure, all three curves pass through the origin, so they are all superparamagnetic and can quickly respond to the external magnetic field. Among them, the saturation magnetization intensity of Fe3O4 is 65.89 A·m 2 / kg, while the saturation magnetization intensities of Fe3O4@SiO2 and MIP are lower. This is because a layer of SiO2 is coated on the outer layer of Fe3O4@SiO2 and MIP particles, which has a certain blocking effect on the magnetic field, resulting in a slight decrease in the magnetization intensity.

[0043] (4) X-ray diffraction pattern (XRD)

[0044] Figure 3 c shows the XRD patterns of the magnetic particles Fe3O4, Fe3O4@SiO2, and MIP. Analysis shows that the three magnetic particles have obvious characteristic absorption peaks at 2θ of 30.2°, 35.6°, 43.2°, 53.2°, 57.2°, and 62.8°, corresponding to the six crystal planes (220), (311), (400), (422), (511), and (440) of Fe3O4. It shows that the position of the diffraction peak of Fe3O4 will not change after surface modification, and these magnetic particles are all centered on Fe3O4.

[0045] Example 2

[0046] Adsorption test for vitexin

[0047] (1) Adsorption isotherm curve

[0048] Weigh 10 mg of MIP and NIP separately into conical flasks, add 1.5 mL of vitexin solution with a concentration of 100 - 1000 μg / mL, seal and shake in a constant temperature shaker at 40 °C for 1 h. After magnetic separation, filter through a 0.45 μm microporous membrane. Measure the concentration of vitexin in the filtrate by high performance liquid chromatography at a wavelength of 350 nm. Calculate the equilibrium adsorption capacity Q (mg / g) of vitexin according to the change in the mass concentration of vitexin before and after adsorption. The calculation formula is as follows:

[0049] Q = (Co - Ce) * V / m

[0050] In the formula, Co is the initial mass concentration of vitexin (mg / mL), Ce is the equilibrium mass concentration (mg / mL), V is the volume of the solution (mL), and m is the mass of MMIP and NIP (g).

[0051] (2) Adsorption kinetics

[0052] Weigh 50 mg of MMIP and NIP separately into conical flasks, add 10 mL of vitexin standard solution (0.6 mg / mL), seal and shake in a constant temperature shaker at 40 °C. After magnetic separation, at 10, 20, 30, 60, 90, 120, 180, and 240 min, take the solution and filter through a 0.45 μm microporous membrane. Measure the change in the concentration of vitexin in the filtrate by HPLC at a wavelength of 350 nm, and calculate the adsorption amount of MMIP to vitexin at different times.

[0053] As Figure 4 shown, with the increase in the concentration of the vitexin solution, the adsorption amount of MIP gradually increases; when the mass concentration of vitexin reaches 0.6 mg / L, it reaches equilibrium, and the adsorption amount is 14.6 mg / g. Compared with NIP, MIP obviously has a higher adsorption amount. As Figure 5 shown, the adsorption amount of MIP to vitexin increases rapidly in a short time, and the adsorption amount approaches saturation (Q = 16.1 mg / g) at 90 min. With the extension of the oscillation time, the adsorption rate decreases and tends to be stable.

[0054] Example 3

[0055] Comparison of selective adsorption of orientin, isoorientin, vitexin, isovitexin, luteolin, and apigenin

[0056] Prepare standard solutions of orientin, isoorientin, vitexin, isovitexin, luteolin, and apigenin at 0.6 mg / mL respectively for the selective adsorption experiment, and measure the adsorption amounts of MIP or NIP in different adsorption systems for the template molecules orientin, isoorientin, vitexin, isovitexin and their structural analogs luteolin and apigenin. Weigh 10 mg of MIP and NIP and place them in a 25 ml conical flask. Add 1.5 mL of 0.6 mg / mL vitexin, isovitexin, orientin, isoorientin, luteolin, and apigenin solutions respectively. Seal and shake in a constant temperature shaker at 40 °C for 1 h. After magnetic separation, detect the concentration of the filtrate by HPLC, and calculate the adsorption amounts of each substance respectively.

[0057] The experimental results are as Figure 6 shown. The MIP with orientin, isoorientin, vitexin, and isovitexin as imprinted template molecules showed specific adsorption for orientin, isoorientin, vitexin, and isovitexin, and the adsorption ability was greater than that of the other two structurally similar molecules. In comparison, NIP adsorbed all six molecules, but mainly through non-specific adsorption, and there was no difference in the adsorption amount. In addition, since the other two molecules have similar molecular structures, the adsorption ability of MIP for other molecules was also stronger than that of the NIP group, and the closer the molecular structure was to the template molecule structure, the stronger the specific adsorption.

[0058] Example 4

[0059] Weigh 35 mg of bamboo leaf extract with a total flavonoid content of 24% and transfer it to a 100 mL volumetric flask. Dilute it to the mark with methanol. Weigh 20 mg of MIP and place it in a 50 mL conical flask. Add 20 mL of the above-mentioned ginkgo extract solution. Seal and shake in a constant temperature shaker at 40 °C for 1 h. Filter through a 0.45 μm microporous filter membrane, and detect the components in the filtrate by liquid phase to investigate the adsorption performance of MIP for bamboo leaf extract.

[0060] Chromatographic conditions: BDS Hypersil TM C18 column (250 mm × 4.6 mm, 5 μm); methanol as mobile phase A, and 0.5% formic acid aqueous solution as mobile phase B for gradient elution. Gradient elution conditions: 0 - 20 min, 35%A, 65%B; 20 - 25 min, 35%A → 50%A, 65%B → 50%B; 25 - 35 min, 50%A, 50%B; 35 - 36 min, 50%A → 100%A, 50%B → 0%B; 36 - 45 min, 100%A → 35%A, 0%B → 65%B; 45 - 50 min, 35%A, 65%B. The flow rate is 1.0 mL / min, the detection wavelength is 350 nm, the injection volume is 10 μL, and the column temperature is 30 °C.

[0061] As Figure 7As shown, when MIP was added to the crude flavonoid extract solution, the total flavonoid content increased from 24% to over 90% after adsorption. Six flavonoid compounds were detected in the high-purity flavonoids by HPLC, including four C-glycosyl flavones, accounting for 90.73%. The contents of isoorientin and orientin were between 33% and 40%, and the contents of vitexin and isovitexin were between 40% and 48%.

[0062] Table 1. HPLC retention parameters of six flavonoids in the eluted solution

[0063]

[0064] In summary, the present invention uses a typical C-glycosyl flavone as a template to prepare a magnetic flavonoid molecularly imprinted polymer MIP. Combining HPLC analysis can provide a rapid, reliable, and economical method for separating high-purity flavonoid compounds from complex natural extracts with similar structures. This work provides a new strategy for the separation and enrichment of flavonoid compounds and has important practical value for the research of active ingredients in traditional Chinese medicine.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a magnetic molecularly imprinted polymer for typical carbon-glycoside flavonoids in bamboo leaves, characterized in that, It includes the following steps: 1) Preparation and characterization of Fe3O4 nanoparticles: Dissolve 1 part of FeCl3·6H2O in ethylene glycol with a concentration of 15 - 30 g / L. Add 0.5 - 2 parts of polyethylene glycol to the solution, disperse it by ultrasonic wave for 10 - 30 min, add 3 - 6 parts of anhydrous sodium acetate, stir the solution until it is clear and transparent, then transfer the solution to a reaction kettle, react at 150 - 200 °C for 5 - 10 h, wash it alternately with water and absolute ethanol for 3 - 5 times, and dry it under vacuum at 40 - 80 °C to obtain Fe3O4 nanoparticles with the particle size maintained at 50 - 200 nm; 2) Preparation and characterization of Fe3O4@SiO2 nanoparticles: Add the Fe3O4 nanoparticles obtained in step 1) to an ethanol solution with a mass concentration of 40 - 80%, with a concentration of 1 - 3 g / L, disperse it by ultrasonic wave for 10 - 30 min, add 1 - 5 mL of ammonia water to the solution, stir for 10 - 30 min, then dropwise add 1 - 5 mL of tetraethyl orthosilicate drop by drop under the liquid surface. React this mixture at 40 - 50 °C and 300 - 500 r / min for 12 - 24 h. After magnetic separation, wash it alternately with absolute ethanol and water for 3 times, and dry it under vacuum at 40 - 60 °C to obtain Fe3O4@SiO2 nanoparticles with the particle size in the range of 50 - 200 nm; 3) Functional modification and characterization of Fe3O4@SiO2 nanoparticles: Take Fe3O4@SiO2 nanoparticles and disperse them in an ethanol solution of 50 - 80%, ultrasonicate for 10 - 30 min, add 5 - 10 mL of ammonia water, add a modifier, mechanically stir at 200 - 500 r / min, react at 60 - 80 °C for 12 - 24 h. After magnetic separation, obtain a black solid, wash it with ethanol for 4 - 5 times, and dry it under vacuum at 40 - 60 °C to obtain modified Fe3O4@SiO2 magnetic nanoparticles with the particle size of 50 - 300 nm; 4) Magnetic molecularly imprinted polymer MIP of typical carbon - glycoside flavonoids in bamboo leaves: Disperse the template molecule of carbon - glycoside flavonoids in bamboo leaves and the functional monomer in a solvent at a molar ratio of 1:4 - 1:8, and store it at 4 °C for 5 - 12 h to obtain a prepolymer solution. Preferably, store it for 10 - 12 h to make the self - assembly reaction more complete. Then add the modified Fe3O4@SiO2 particles and a cross - linker. The molar ratio of the template molecule to the cross - linker is 1:10 - 1:

50. Under nitrogen protection, add an initiator. The molar ratio of the template molecule to the initiator is 1:1 - 1:

3. After introducing nitrogen for 10 - 30 min, seal it and carry out a polymerization reaction at 50 - 70 °C. Wash the reaction product with a methanol - acetic acid mixture until the ultraviolet absorption peak of the template molecule cannot be detected in the eluent, and then dry it under vacuum at 40 - 60 °C to prepare the molecularly imprinted polymer MIP of typical carbon - glycoside flavonoids in bamboo leaves with the particle size maintained at 50 - 300 nm.

2. According to the method described in claim 1, the template molecule is characterized by being at least one of carbon - glycoside flavonoids such as isoorientin, orientin, vitexin or isovitexin, and the molecular weight is in the range of 400 - 500.

3. The method according to claim 1, wherein the functional monomer is a monomer compound having a conjugated double bond, preferably one of acrylic acid, 2-vinylpyridine, 4-vinylpyridine or methacrylic acid.

4. The method according to claim 1, wherein the initiator is azobisisobutyronitrile or benzoyl peroxide, the crosslinking agent is ethylene glycol dimethacrylate or butyl acrylate, and the solvent is acetonitrile or methanol.

5. The method according to claim 1, wherein the mixed solution is a mixture of methanol and acetic acid in a volume ratio of 7:3 to 9:

1.

6. The method according to claim 1, wherein the prepared bamboo leaf carbon glycoside flavonoids by enrichment are characterized in that: a crude bamboo leaf flavonoid extract with a mass fraction of 15-25% is mixed with a magnetic molecularly imprinted polymer MIP, the adsorbed MIP is eluted, and the eluate is analyzed by HPLC to obtain 6 flavonoid compounds, including 4 flavone glycoside compounds; the total flavonoid content is increased to more than 90%; the contents of isoorientin and orientin are 33-40%, and the contents of vitexin and isovitexin are 40-48%; the molecularly imprinted polymer is the bamboo leaf typical carbon glycoside flavonoid magnetic molecularly imprinted polymer according to claim 1, and the 6 flavone glycoside compounds are luteolin, orientin, isoorientin, apigenin, vitexin and isovitexin.

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