A process for preparing apigenin by hydrolysis and recovering rhamnose from mother liquor and its application

Abstract

The invention discloses a process for preparing apigenin by hydrolysis and recovering rhamnose from a mother liquor. The process comprises the following steps: mixing a wild sumac glycoside raw material with dilute sulfuric acid, heating for hydrolysis and filtering to obtain a filtered mother liquor and a filter cake; washing the filter cake with purified water and drying to obtain a crude apigenin product; recrystallizing to obtain a refined apigenin product; deacidifying the filtered mother liquor and concentrating it to obtain a concentrated mother liquor; adding high-sugar-tolerant yeast to the concentrated mother liquor and fermenting it at a heat preservation temperature to obtain a fermentation liquid; heating the fermentation liquid, adding sugar, decolorizing it with activated carbon and filtering it to obtain a filtrate; concentrating the filtrate and then crystallizing it at a low temperature, performing solid-liquid separation with a centrifuge to obtain a crude rhamnose product; drying the crude rhamnose product to obtain a crude rhamnose product; and refining to obtain a refined rhamnose product. The invention achieves the purpose of preparing two high-yield products by one process, solves the problems of high cost and large amount of waste in apigenin extraction and highly polluted solvent generated by extracting rhamnose from organic matter in the prior art, and has high yield, low cost, low environmental harm and high economic benefit.

Description

Technical Field

[0001] The present invention relates to the technical field of biomedicine, and in particular to a process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor and its application. Background Art

[0002] Apigenin is a flavonoid compound widely distributed in nature, primarily found in plants of the Thymelaeaceae, Verbenaceae, and Selaginellaceae families. It possesses numerous biological activities, including anti-tumor, cardiovascular and cerebrovascular protection, antiviral, and antibacterial properties, and holds great potential for application. However, its low concentration in natural plants and low extraction yield have limited its development and application.

[0003] The following methods are currently available for preparing apigenin: Plant-based extraction methods, however, are complex and difficult to purify due to the low apigenin content in plants. This results in excessive consumption and waste of raw materials, low purity and yield, and limited practical application value. Enzymatic hydrolysis methods, however, are expensive and require high storage and handling requirements, and are prone to inactivation, resulting in high production costs and hindering industrial application. Semi-synthetic methods, however, use naringin as a raw material to synthesize apigenin. Although the high naringin content makes it suitable for industrial application, the use of organic solvents such as pyridine causes environmental pollution and does not meet environmental protection requirements.

[0004] Rhamnose, also known as 6-deoxy-L-mannose, is widely found in plant polysaccharides, glycosides, plant gums, and bacterial polysaccharides. Its sweetness is 33% of sucrose, and it can be used to measure intestinal permeability, used as a sweetener, and used in the production of flavors and fragrances. Rhamnose, a trace sugar, is widely distributed in plants and can be found in the form of sugars in many plant glycosides such as quercetin and isohesperidin, polysaccharides, especially pectin and pectin, and in succinic acid. Existing rhamnose production technologies mainly include the following: Strain fermentation, which utilizes engineered microbial strains to ferment and produce rhamnose. However, the efficiency of microbial strains is generally low, and the process conditions are difficult to control, resulting in high costs. The plant raw material extraction method uses seaweed, gum arabic and other raw materials rich in rhamnose for separation and extraction. This method requires catalytic degradation of biomass, resulting in a large amount of raw material waste. The yield based on the input of plant raw materials is very low and cannot meet the needs of industrial production. In addition, the extraction of rhamnose from plant raw materials uses a high-concentration methanol solution to purify rhamnose. Methanol is toxic and seriously pollutes the environment. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical defects in the production of apigenin and rhamnose in the prior art, and provide a process for preparing apigenin by hydrolysis and recovering rhamnose by mother liquor and its application, so as to achieve the purpose of preparing two high-yield, high-purity and high-content products by one process, and solve the problems in the prior art of difficult industrial production of apigenin, environmental pollution and organic solvent pollution caused by extraction of rhamnose. The invention has high yield, low cost, small environmental harm, high economic benefit and high value for industrial application.

[0006] In order to solve this technical problem, the present invention provides the following technical solutions:

[0007] A process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor comprises the following steps:

[0008] S1: Mix the wild sumac glycoside raw material with dilute sulfuric acid, heat to boiling for hydrolysis, cool and filter to obtain a filtration mother liquor and a filter cake;

[0009] S2: The filter cake is washed with pure water until the filtrate is colorless and pH neutral, and then dried to obtain crude apigenin; the crude apigenin is recrystallized from methanol solution to obtain refined apigenin;

[0010] S3: deacidifying the filtered mother liquor to a pH value of 4-6, and concentrating it to a relative density of 1.07-1.12 to obtain a concentrated mother liquor;

[0011] S4: adding high-sugar-tolerant yeast to the concentrated mother liquor and fermenting the mixture at room temperature to obtain a fermentation liquid;

[0012] S5: After heating the fermentation liquid, sugar is added, decolorized with activated carbon, and filtered to obtain a filtrate;

[0013] S6: concentrating the filtrate and then crystallizing it at low temperature to obtain a solid-liquid mixture, and separating the solid-liquid mixture by a centrifuge to obtain a crude wet product of rhamnose;

[0014] S7: drying the crude wet rhamnose to obtain crude rhamnose; and refining the crude rhamnose to obtain refined rhamnose.

[0015] The method adopts wild sumac glycoside to carry out hydrolysis reaction to prepare apigenin, and the reaction process is simple and the cost is low; no organic solvent is used, which will not cause environmental pollution and has good economic benefits; and the hydrolysis mother liquor can be effectively utilized to recover rhamnose, further improving the economic benefits; the use of high-sugar-tolerant yeast for heat preservation fermentation can improve the purity of rhamnose, thereby increasing the rhamnose content, and avoids the generation of organic solvents when extracting rhamnose in the existing technology, and the reaction conditions are mild.

[0016] Preferably, in step S1, the mass volume ratio of rhubarb glycoside to dilute sulfuric acid is 1 g:10-15 ml, the concentration of dilute sulfuric acid is 4.5%-5.0%, the mixture is heated to boiling, and the hydrolysis reaction time is 5-7 h.

[0017] The optimized mass-to-volume ratio of rhamnoside to dilute sulfuric acid results in a better hydrolysis effect, thereby increasing the yield of apigenin and rhamnose.

[0018] Preferably, the concentration of the methanol solution in step S2 is 85%-95%, and the amount used is 10-12 times the volume of the crude apigenin. The recrystallization process is heating and reflux at 70-80°C for 2-3 hours, and filtration is performed to obtain an apigenin filtrate; the apigenin filtrate is concentrated to 0.30-0.35 of the original volume, and then refrigerated and crystallized at 2-5°C for 12-16 hours. The apigenin filter cake is collected by filtration, and the filter cake is washed with water until there is no alcohol taste, and then the filter cake is placed in an oven at 60-80°C to dry to obtain a refined apigenin product.

[0019] Preferably, the deacidification in step S3 is performed using an electrodialysis membrane.

[0020] Electrodialysis membrane deacidification utilizes ion exchange membranes under the influence of an electric field to remove and recover ionic substances from a solution. Specifically, cation exchange membranes and anion exchange membranes are alternately placed between a pair of electrodes. A direct current causes anions to accumulate on the anode side and cations to accumulate on the cathode side. These cations then pass through the cation and anion exchange membranes and migrate to the acid chamber, removing acid from the filtered mother liquor and raising its pH. The filtered acid can be reused, reducing energy consumption and emissions, offering environmental benefits and high economic benefits.

[0021] Preferably, the amount of high-sugar-tolerant yeast used in step S4 is 1%-2% of the volume of the concentrated mother liquor, the fermentation temperature is maintained at 35-40°C, and the fermentation time is maintained at 16-20 hours. The absence of glucose spots in the fermentation broth by thin-layer chromatography (TLC) can indicate the end of fermentation. Fermentation can remove glucose from the concentrated mother liquor and increase the purity of rhamnose. By optimizing the fermentation temperature and time, excellent fermentation conditions and results are achieved.

[0022] Preferably, the heating temperature in step S5 is 50-60° C., the amount of sugar-containing activated carbon used is 5%-8% by weight of the fermentation liquid, and the decolorization time is 1-2 h.

[0023] Preferably, in step S6, the filtrate is concentrated to a relative density of 1.25-1.28, the crystallization time is 18-24 hours, and the crystallization temperature is below -10°C.

[0024] Preferably, the drying temperature of the crude wet rhamnose in step S7 is 40°C-60°C.

[0025] Preferably, the refining process in step S7 is to use 2-3.5 times the volume ratio of ethanol solution to heat and dissolve the crude rhamnose at 50-60 ° C, add 2% sugar and reflux with activated carbon for decolorization, filter and concentrate the filtrate to a specific gravity of 1.25-1.28, then crystallize at below -10 ° C for 18h-24h, use a centrifuge for solid-liquid separation, and dry the solid at 40 ° C-60 ° C to obtain the refined rhamnose.

[0026] The present application also provides the application of the above-mentioned process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor in the preparation of apigenin and rhamnose.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] The hydrolysis of wild sumac glycosides is used to produce apigenin, resulting in a high-purity refined apigenin exceeding 98%. The mother liquor from the hydrolysis can also be recycled, avoiding pollution while recovering a high content of rhamnose, with the resulting refined rhamnose content exceeding 98%. Both products have high yields, and the process is simple, low-cost, environmentally friendly, and highly economical.

[0029] The process of recovering rhamnose uses high-sugar-tolerant yeast for heat preservation fermentation. High-sugar-tolerant yeast is suitable for higher fermentation temperatures, thereby shortening the fermentation time and improving production efficiency. The reaction conditions are mild and the process is simple and easy to control.

[0030] Electrodialysis membrane deacidification uses an ion exchange membrane under the action of an electric field to deacidify and recover ionic substances in the solution. The filtered acid can be reused, reducing consumption and emissions, being environmentally friendly and highly economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0032] Figure 1 This is a chromatogram of apigenin obtained in Example 1 of the present invention;

[0033] Figure 2 This is a chromatogram of rhamnose obtained in Example 1 of the present invention;

[0034] Figure 3 This is the chromatogram of apigenin standard;

[0035] Figure 4 This is the chromatogram of rhamnose standard. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0037] In the present invention, above and below are used as descriptive words and are inclusive. For example, the crystallization temperature is below -10°C, which includes -10°C and other temperatures below -10°C.

[0038] The present invention provides a process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor and its application, using rhamnose as a raw material to prepare apigenin and rhamnose. The process comprises the following steps:

[0039] 1. Hydrolysis: Add the wild sumac glycoside raw material to a dilute sulfuric acid solution, stir and mix, and heat to boiling for hydrolysis. Maintain boiling for 5-7 hours, then cool to room temperature and filter to obtain a filtration mother liquor and a filter cake. The filter cake is mainly composed of apigenin, and also contains trace amounts of rhamnose and glucose. The filtration mother liquor contains sulfuric acid, rhamnose, glucose, and a small amount of apigenin.

[0040] 2. Preparation of crude apigenin: Wash the filter cake with purified water until the filtrate is colorless and the pH of the filtrate is neutral, specifically between 6.8 and 7.2, indicating that the sulfuric acid component on the surface of the filter cake has been removed. Dry the filter cake in an oven to obtain crude apigenin.

[0041] The filtrate after washing the filter cake contains components such as sulfuric acid, rhamnose, and glucose, which can be collected and mixed with the filtered mother liquor in step 1 for reuse. Considering that the effective ingredient content of the filtrate in step 2 is average and decreases with washing, considering the recovery cost and economic value, only the first half of the filtrate after washing the filter cake can be collected, and the subsequent filtrate can be treated as waste and no longer used.

[0042] 3. Preparation of refined apigenin: Place the crude apigenin in a methanol solution, heat under reflux at 70-80°C for 2-3 hours, then filter to remove impurities and obtain an apigenin filtrate. Concentrate the apigenin filtrate, then crystallize it at 2-5°C, and filter to obtain an apigenin filter cake. Apigenin, rhamnose, and glucose have different solubilities and crystallization temperatures in methanol. Through the methanol dissolution, concentration, and crystallization steps, rhamnose, glucose, and other impurities in the crude apigenin can be effectively removed, effectively improving the purity of the refined apigenin. Wash the apigenin filter cake with purified water until there is no alcohol smell, then dry it in an oven to obtain the refined apigenin. Due to the low volatilization temperature of methanol, no reagent testing is required during the purified water wash. The absence of alcohol smell proves that the methanol content in the crude apigenin is extremely low, and the oven drying process will also completely evaporate the methanol.

[0043] Because the heating reflux process is used, the concentration of methanol solvent in the filtrate remaining after filtering the celogenin filter cake is still high. After the filtrate is concentrated, the methanol solvent can be reused. At the same time, the liquid after washing the celogenin filter cake is recovered. The liquid contains a small amount of methanol solvent. After measuring the methanol concentration, this liquid can be directly recycled and reused as needed, or purified and reused. This effectively saves methanol consumption.

[0044] 4. Concentration of filtered mother liquor: The filtered mother liquor obtained in the first step, or the mixed liquor after the filtered mother liquor is mixed with the washing filtrate in the second step, contains a large amount of acid components and needs to be deacidified first. The present application adopts electrodialysis membrane deacidification, which is to use ion exchange membrane to deacidify and recover the ionic substances of the solution under the action of an electric field. Specifically, a cation exchange membrane and an anion exchange membrane are alternately arranged between a pair of electrodes, and a direct current is used to make an anion gather to the anode side, and a cation gather to the cathode side, and move to the acid chamber through the cation exchange membrane and the anion exchange membrane, thereby removing the acid in the filtered mother liquor and raising the pH value of the filtered mother liquor to 4-6. After deacidification, the filtered mother liquor is concentrated to a relative density of 1.07-1.12 to obtain a concentrated mother liquor. The volume of the concentrated mother liquor is one-fifth to one-seventh of the volume of the filtered mother liquor. The concentration process effectively reduces the liquid volume, thereby effectively saving the amount of high-sugar-tolerant yeast in the subsequent steps.

[0045] 5. Fermentation: High-sugar-tolerant yeast is added to the concentrated mother liquor for fermentation, consuming the glucose in the concentrated mother liquor. After fermentation is complete, a fermentation broth is obtained. The fermentation broth is heated, sugar is added, decolorized with activated carbon, and filtered to obtain a filtrate. Using high-sugar-tolerant yeast can shorten fermentation time and improve production efficiency.

[0046] 6. Preparation of crude rhamnose: The filtrate is concentrated and then crystallized at low temperature to obtain a solid-liquid mixture containing solids and liquids. The solid-liquid mixture is placed in a centrifuge for solid-liquid separation, resulting in a solid, crude rhamnose. The crude rhamnose is then dried to obtain crude rhamnose. Using a centrifuge for solid-liquid separation allows for sufficient collection of rhamnose and improves yield.

[0047] 7. Preparation of refined rhamnose: Crude rhamnose is dissolved in an ethanol solution by heating. Sugar is then added and decolorized with activated carbon. Impurities are then removed by filtration. The resulting filtrate is concentrated and fully crystallized at low temperature. The resulting solid-liquid separation is then performed in a centrifuge to obtain solid rhamnose. The solid is then dried in an oven to obtain refined rhamnose. Using ethanol as a solvent for refined rhamnose, due to its slightly lower polarity, ethanol can remove organic impurities such as apigenin from the rhamnose.

[0048] The purity of the refined apigenin obtained by the above process reaches more than 98%, and the refined rhamnose content reaches more than 98%; taking wild sumac glycoside as the starting material, the yield of apigenin is more than 45%, the yield of rhamnose is more than 30%, and the total yield is more than 75%. The economic value is very high, and the cost is low, and it can be applied industrially on a large scale. There is basically no waste in the entire process. Although the sulfuric acid used as a reactant is consumed, the remaining acid can be effectively recovered in the electrodialysis membrane deacidification process, avoiding the waste of acid. The solvents used, such as methanol and ethanol, can also be effectively recycled and reused. Example 1

[0049] 1. Hydrolysis: Weigh 200 g of wild sumac glycoside raw material and add it to 2 L of 4.5% dilute sulfuric acid solution. Heat to boiling and maintain for 5 hours. Then cool to room temperature and filter to obtain the mother liquor and filter cake.

[0050] 2. Preparation of crude apigenin: Rinse the filter cake with purified water until the filtrate is colorless and the pH value of the filtrate is neutral, and dry the filter cake in an oven at 60°C to obtain crude apigenin.

[0051] 3. Preparation of refined apigenin: Prepare an 85% methanol solution that is 10 times the volume of the crude apigenin. Place the crude apigenin in the methanol solution, heat and reflux at 70°C for 2 hours, then filter to remove impurities and obtain an apigenin filtrate. Concentrate the apigenin filtrate to 0.3 of its original volume, then refrigerate and crystallize at 2°C for 12 hours. Filter again to obtain an apigenin filter cake. Wash the apigenin filter cake with purified water until it is free of alcohol, then dry it in an oven at 60°C to obtain refined apigenin. The purity of the refined apigenin was measured to be 99.1%.

[0052] 4. Concentration of the filtered mother liquor: The filtered mother liquor is deacidified using an electrodialysis membrane. Ionic substances in the solution are deacidified and recovered using an ion exchange membrane under the action of an electric field. The pH value of the deacidified liquid is measured to be between 4 and 6. It is then concentrated to a relative density of 1.07 to obtain a concentrated mother liquor.

[0053] 5. Fermentation: Add 2% by volume of high-sugar-tolerant yeast to the concentrated mother liquor and ferment for 16 hours at a temperature of 35°C. Check the fermentation broth for the absence of glucose spots using thin-layer chromatography. Heat the broth to 50°C and add 5% by weight of sugar to the broth. Decolorize with activated carbon for 1 hour and filter to obtain the filtrate.

[0054] 6. Preparation of crude rhamnose: The filtrate was concentrated to a relative density of 1.25, then placed in a -10°C environment for crystallization for 18 hours to obtain a solid-liquid mixture containing solids and liquids. The solid-liquid mixture was placed in a centrifuge for solid-liquid separation to obtain crude wet rhamnose. The crude wet rhamnose was dried in an oven at 40°C to obtain crude rhamnose.

[0055] 7. Preparation of refined rhamnose: Prepare a 75% ethanol solution twice the volume of crude rhamnose. Add rhamnose to the solution and heat to 50°C with stirring to dissolve. Add 2% sugar by weight and decolorize with activated carbon under reflux for 1 hour. Filter to remove impurities, concentrate the resulting filtrate to a relative density of 1.25, and crystallize at -10°C for 18 hours. Then, centrifuge for solid-liquid separation to obtain a rhamnose solid. Dry the solid in an oven at 40°C to obtain refined rhamnose. The refined rhamnose content is measured to be 98.8%. Example 2

[0056] 1. Hydrolysis: Weigh 200 g of wild sumac glycoside raw material and add it to 2.4 L of 4.75% dilute sulfuric acid solution. Heat to boiling and maintain for 6 hours. Then cool to room temperature and filter to obtain the mother liquor and filter cake.

[0057] 2. Preparation of crude apigenin: Rinse the filter cake with purified water until the filtrate is colorless and the pH value of the filtrate is neutral, and dry the filter cake in an oven at 70°C to obtain crude apigenin.

[0058] 3. Preparation of refined apigenin: Prepare a 90% methanol solution that is 11 times the volume of the crude apigenin. Place the crude apigenin in the methanol solution, heat and reflux at 75°C for 2.5 hours, then filter to remove impurities and obtain an apigenin filtrate. Concentrate the apigenin filtrate to 0.35 of its original volume, then refrigerate and crystallize at 4°C for 14 hours, and filter again to obtain an apigenin filter cake. Wash the apigenin filter cake with purified water until it is free of alcohol, then dry it in an oven at 70°C to obtain refined apigenin. The purity of the refined apigenin was measured to be 98.7%.

[0059] 4. Concentration of the filtered mother liquor: The filtered mother liquor is deacidified using an electrodialysis membrane. Ionic substances in the solution are deacidified and recovered using an ion exchange membrane under the action of an electric field. The pH value of the deacidified liquid is measured to be between 4 and 6. It is then concentrated to a relative density of 1.1 to obtain a concentrated mother liquor.

[0060] 5. Fermentation: Add 1.5% by volume of high-sugar-tolerant yeast to the concentrated mother liquor for fermentation. Maintain the fermentation temperature at 37.5°C for 18 hours. Check the fermentation broth for the absence of glucose spots using thin-layer chromatography. Heat the broth to 55°C and add 6% by weight of sugar to the broth. Decolorize with activated carbon for 1.5 hours and filter to obtain the filtrate.

[0061] 6. Preparation of crude rhamnose: The filtrate was concentrated to a relative density of 1.27, then placed in a -12°C environment for crystallization for 20 hours to obtain a solid-liquid mixture containing solids and liquids. The solid-liquid mixture was placed in a centrifuge for solid-liquid separation to obtain crude wet rhamnose. The crude wet rhamnose was dried in an oven at 50°C to obtain crude rhamnose.

[0062] 7. Preparation of refined rhamnose: Prepare a 75% ethanol solution three times the volume of crude rhamnose. Add rhamnose to the solution and heat to 55°C with stirring to dissolve. Add 2% sugar by weight and decolorize with activated carbon under reflux for 1.5 hours. Filter to remove impurities, concentrate the resulting filtrate to a relative density of 1.27, and crystallize at -12°C for 20 hours. Then, centrifuge for solid-liquid separation to obtain a rhamnose solid. Dry the solid in an oven at 50°C to obtain refined rhamnose. The refined rhamnose content is measured to be 99.2%. Example 3

[0063] 1. Hydrolysis: Weigh 200 g of wild sumac glycoside raw material and add it to 3 L of 5.0% dilute sulfuric acid solution. Heat to boiling and maintain for 7 hours. Then cool to room temperature and filter to obtain the mother liquor and filter cake.

[0064] 2. Preparation of crude apigenin: Rinse the filter cake with purified water until the filtrate is colorless and the pH value of the filtrate is neutral, and dry the filter cake in an oven at 80°C to obtain crude apigenin.

[0065] 3. Preparation of refined apigenin: Prepare a 95% methanol solution that is 12 times the volume of the crude apigenin. Place the crude apigenin in the methanol solution, heat and reflux at 80°C for 3 hours, then filter to remove impurities and obtain an apigenin filtrate. Concentrate the apigenin filtrate to 0.35 of its original volume, then refrigerate and crystallize at 5°C for 16 hours. Filter again to obtain an apigenin filter cake. Wash the apigenin filter cake with purified water until it is free of alcohol, then dry it in an oven at 80°C to obtain refined apigenin. The purity of the refined apigenin was measured to be 98.9%.

[0066] 4. Concentration of the filtered mother liquor: The filtered mother liquor is deacidified using an electrodialysis membrane. Ionic substances in the solution are deacidified and recovered using an ion exchange membrane under the action of an electric field. The pH value of the deacidified liquid is measured between 4 and 6. It is then concentrated to a relative density of 1.12 to obtain a concentrated mother liquor.

[0067] 5. Fermentation: Add 1% by volume of high-sugar-tolerant yeast to the concentrated mother liquor and ferment for 20 hours at 40°C. Check the fermentation broth for the absence of glucose spots using thin-layer chromatography. Heat the broth to 60°C and add 8% by weight of sugar to decolorize the broth with activated carbon for 2 hours. Filter to obtain the filtrate.

[0068] 6. Preparation of crude rhamnose: The filtrate was concentrated to a relative density of 1.28, then placed in a -15°C environment for crystallization for 24 hours to obtain a solid-liquid mixture containing solids and liquids. The solid-liquid mixture was centrifuged for solid-liquid separation to obtain crude wet rhamnose. The crude wet rhamnose was dried in an oven at 60°C to obtain crude rhamnose.

[0069] 7. Preparation of refined rhamnose: Prepare a 75% ethanol solution 3.5 times the volume of crude rhamnose. Add rhamnose to the solution and heat to 60°C with stirring to dissolve. Add 2% sugar by weight and decolorize with activated carbon under reflux for 2 hours. Filter to remove impurities, concentrate the resulting filtrate to a relative density of 1.28, and crystallize at -15°C for 24 hours. After solid-liquid separation in a centrifuge, obtain a solid rhamnose product. Dry the solid product in an oven at 60°C to obtain refined rhamnose. The refined rhamnose content is measured to be 99.2%.

[0070] The purity of apigenin and rhamnose content obtained in Example 1 were determined using the HPLC method:

[0071] Apigenin purity detection method:

[0072] Chromatographic conditions: octadecylsilane bonded silica gel as filler; 0.5% formic acid aqueous solution-acetonitrile (60:40) as mobile phase; detection wavelength: 285 nm; flow rate: 1.0 mL / min; column temperature: 30°C; injection volume: 10 μL.

[0073] Preparation of test solution: Take an appropriate amount of the product, weigh accurately, dissolve it in mobile phase and quantitatively dilute it to make a solution containing approximately 0.1 mg per 1 ml.

[0074] Preparation of standard solution: Take an appropriate amount of apigenin standard, weigh accurately, dissolve in mobile phase and quantitatively dilute to make a solution containing approximately 0.1 mg per 1 ml.

[0075] Determination method: Accurately measure the test solution and standard solution, inject them into the liquid chromatograph respectively, record the chromatogram, and calculate by area percentage.

[0076] Rhamnose content detection method:

[0077] Chromatographic conditions: a high-efficiency sugar column (250 mm × 4.6 mm, 5 μm); acetonitrile-water (4:1) as the mobile phase; flow rate: 1.0 mL / min; column temperature: 30°C; injection volume: 10 μL.

[0078] Preparation of test solution: Take an appropriate amount of the product, weigh accurately, dissolve it in mobile phase and quantitatively dilute it to make a solution containing approximately 16 mg per 1 ml.

[0079] Preparation of standard solution: Take an appropriate amount of rhamnose standard, weigh accurately, dissolve in mobile phase and quantitatively dilute to make a solution containing approximately 16 mg per 1 ml.

[0080] Determination method: Accurately measure the test solution and standard solution, inject them into liquid chromatograph respectively, and record the chromatogram.

[0081] from Figure 1 and Figure 3 It can be seen that the purity of the obtained apigenin can reach more than 98%. Figure 2 and Figure 4 It can be seen that the obtained rhamnose content is high, reaching more than 98%.

[0082] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor, characterized in that: The following steps are involved: S1: Mix the wild sumac glycoside raw material with dilute sulfuric acid, heat to boiling for hydrolysis, cool and filter to obtain a filtration mother liquor and a filter cake; S2: The filter cake is washed with pure water until the filtrate is colorless and pH neutral, and then dried to obtain crude apigenin; the crude apigenin is recrystallized from methanol solution to obtain refined apigenin; S3: deacidifying the filtered mother liquor to a pH value of 4-6, and concentrating it to a relative density of 1.07-1.12 to obtain a concentrated mother liquor; S4: adding high-sugar-tolerant yeast to the concentrated mother liquor and fermenting the mixture at room temperature to obtain a fermentation liquid; S5: After heating the fermentation liquid, sugar is added, decolorized with activated carbon, and filtered to obtain a filtrate; S6: concentrating the filtrate and then crystallizing it at low temperature to obtain a solid-liquid mixture, and separating the solid-liquid mixture by a centrifuge to obtain a crude wet product of rhamnose; S7: drying the crude wet rhamnose to obtain crude rhamnose; and refining the crude rhamnose to obtain refined rhamnose.

2. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: In step S1, the mass volume ratio of rhubarb glycoside to dilute sulfuric acid is 1 g:10-15 ml, the concentration of dilute sulfuric acid is 4.5%-5.0%, and the mixture is heated to boiling. The hydrolysis reaction time is 5-7 hours.

3. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: In step S2, the concentration of the methanol solution is 85%-95%, and the amount used is 10-12 times the volume of the crude apigenin. The recrystallization process is to heat and reflux at 70-80°C for 2-3 hours, and obtain the apigenin filtrate after filtration; the apigenin filtrate is concentrated to 0.30-0.35 of the original volume, and then refrigerated and crystallized at 2-5°C for 12-16 hours, and the apigenin filter cake is collected by filtration, and the filter cake is washed with water until there is no alcohol taste, and then placed in an oven at 60-80°C for drying to obtain the apigenin fine product.

4. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: In step S3, deacidification is performed using an electrodialysis membrane.

5. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: In step S4, the amount of high-sugar-tolerant yeast used is 1%-2% of the volume of the concentrated mother liquor, the fermentation temperature is 35-40° C., and the fermentation time is 16 h-20 h.

6. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: The heating temperature in step S5 is 50-60° C., the amount of activated carbon for sugar is 5%-8% of the weight of the fermentation liquid, and the decolorization time is 1-2 hours.

7. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: In step S6, the filtrate is concentrated to a relative density of 1.25-1.28, the crystallization time is 18-24 hours, and the crystallization temperature is below -10°C.

8. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: The drying temperature of the crude wet rhamnose in step S7 is 40° C.-60° C.

9. The process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to claim 1, characterized in that: The refining process in step S7 is to use 2-3.5 times the volume of ethanol solution to dissolve the crude rhamnose by heating at 50-60°C, add 2% sugar and decolorize it with activated carbon under reflux, filter and concentrate the filtrate to a specific gravity of 1.25-1.28, then crystallize it at below -10°C for 18h-24h, use a centrifuge to separate the solid and liquid, and dry the solid at 40°C-60°C to obtain the refined rhamnose.

10. Use of the process for preparing apigenin by hydrolysis and recovering rhamnose from the mother liquor according to any one of claims 1 to 9 in preparing apigenin and rhamnose.

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