Method for obtaining high-content madecassoside from centella asiatica through membrane separation method

Abstract

The invention discloses a method for obtaining high-content madecassoside from centella asiatica by using a membrane separation method, which comprises the following steps: extraction: crushing a centella asiatica raw material, and extracting by using an ethanol solution to obtain a centella asiatica extracting solution; the centella asiatica extracting solution is filtered and centrifuged, and impurities and macromolecular substances in the centella asiatica extracting solution are removed; membrane separation: carrying out ultrafiltration separation on the pretreated extracting solution through an ultrafiltration membrane, and intercepting impurities of which the molecular weight is greater than that of madecassoside, so as to obtain permeate containing madecassoside; a concentration step: concentrating the permeate through a nanofiltration membrane to obtain a concentrated solution with high content of madecassoside; and a drying step: drying the concentrated solution to obtain a solid product with high content of madecassoside. The method has the beneficial effects that impurities are effectively removed, and the purity of madecassoside is improved; the operation process is simple and easy to control, and the production cost is reduced; and high-content madecassoside can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of natural product extraction, and in particular to a method for obtaining high-content madecassoside from Centella asiatica by using a membrane separation method. Background Art

[0002] Centella asiatica (L.) Urban, also known as iron lantern, money tooth grass, copper coin grass, horse hoof grass, and Gout root, is a perennial herbaceous plant of the genus Centella in the family Apiaceae. The stem is creeping, slender, and roots on the nodes; the leaves are membranous to herbaceous, round, kidney-shaped or horseshoe-shaped; the umbel has 3 to 4 flowers, the petals are ovate, purple-red or milky white; the fruit is flat on both sides, and the surface is hairy or smooth; the flowering and fruiting period is from April to October. Centella asiatica has the effects of clearing away heat and dampness, promoting blood circulation and stopping bleeding, and detoxifying and reducing swelling. It is mainly used to treat fever, cough and asthma, sore throat, enteritis, dysentery, etc.; it has a tender texture and good palatability and can be eaten raw; the leaves of Centella asiatica are beautiful, evergreen all year round, resistant to trampling, and have a good effect in preventing soil erosion. It is an excellent lawn plant. The key active ingredient in Centella asiatica is madecassoside, which has shown great application potential in the fields of medicine and cosmetics. It has multiple physiological activities such as promoting wound healing, inhibiting scar hyperplasia, anti-oxidation and regulating immunity.

[0003] In the traditional extraction process, solvent extraction is mainly used to obtain madecassoside. For example, organic solvents are used to extract Centella asiatica multiple times, but this method has many disadvantages. First, the amount of organic solvents used is large, which not only increases the cost, but also the residue of organic solvents may cause potential harm to the environment and human health. Secondly, the operation process of multiple extractions is cumbersome, the extraction efficiency is low, and it is difficult to meet the needs of large-scale industrial production. In addition, the extracts obtained by traditional methods have a high impurity content, and the subsequent separation and purification are difficult, which makes it difficult to ensure the purity and quality of the product.

[0004] In addition to solvent extraction, some other extraction technologies have been tried for the extraction of madecassoside. For example, although column chromatography has certain advantages in separation and purification, it is complicated to operate, requires a lot of time and manpower, and the cost of column chromatography fillers is relatively high. Supercritical fluid extraction has high equipment requirements, large investment, and relatively high operating costs, which limits its wide application in actual production.

[0005] At present, with the increasing requirements for the quality and purity of natural products, as well as the urgent need for efficient, environmentally friendly, and low-cost extraction processes in industrial production, the existing methods for extracting madecassoside can no longer meet the needs of the market. Therefore, it is of great practical significance to develop a new, efficient, and high-content extraction method for makingcassoside. Summary of the invention

[0006] In order to solve the above problems, especially to address the deficiencies in the prior art, the present invention provides a method for obtaining high-content madecassoside from Centella asiatica by membrane separation, which can solve the above problems.

[0007] To achieve the above purpose, the present invention adopts the following technical means:

[0008] A method for obtaining high-content madecassoside from Centella asiatica by membrane separation, comprising the following steps:

[0009] Step 1: Extraction:

[0010] After the Centella asiatica raw material is crushed, an ethanol solution is used for extraction to obtain a Centella asiatica extract;

[0011] Step 2: Preprocessing:

[0012] Filtering and centrifuging the Centella asiatica extract in step 1 to remove impurities and macromolecular substances;

[0013] Step 3: Membrane separation:

[0014] The extract obtained after the pretreatment in step 2 is subjected to ultrafiltration separation through an ultrafiltration membrane to retain impurities with a molecular weight greater than that of madecassoside, thereby obtaining a permeate containing madecassoside;

[0015] Step 4: Concentration step:

[0016] The permeate in step 3 is concentrated through a nanofiltration membrane to obtain a concentrated solution with a high content of madecassoside;

[0017] Step 5: Drying step:

[0018] The concentrated liquid in step 4 is dried to obtain a solid product with a high content of madecassoside.

[0019] A further solution of the present invention is that in step one, the Centella asiatica raw material is fresh, mildew-free, and pest-free Centella asiatica; the Centella asiatica raw material is first washed and dried and then crushed; the Centella asiatica raw material is crushed by a mechanical crushing method, and the particle size of the crushed Centella asiatica powder is 20-80 mesh.

[0020] The above beneficial effects are that fresh, mildew-free, disease-free and insect-free Centella asiatica is selected as the extraction raw material. When collecting, attention should be paid to selecting areas with good growth environment and fertile soil to ensure that the content of madecassoside in Centella asiatica is high.

[0021] The collected Centella asiatica is carefully cleaned to remove dirt, dust and other impurities on the surface. It can be cleaned by rinsing with running water to ensure thorough cleaning. The cleaned Centella asiatica can be dried naturally or dried at low temperature to reduce the moisture content to a certain level, which is convenient for subsequent crushing.

[0022] The dried Centella asiatica is crushed. The degree of crushing has an important influence on the extraction efficiency. The Centella asiatica can be crushed into powders of different particle sizes by mechanical crushing. Through experiments, it is found that when the particle size of the crushed Centella asiatica powder is between 20-80 mesh, the extraction effect is more ideal.

[0023] A further solution of the present invention is that in step 1, the concentration of the ethanol solution is 50-80%, the extraction temperature is 50-70° C., and the extraction time is 2-4 hours.

[0024] The above beneficial effects are due to the advantages of ethanol solution: after a large number of experimental comparisons, it was found that ethanol solution is an ideal solvent for extracting madecassoside. Ethanol has good solubility and can effectively dissolve madecassoside and other active ingredients in Centella asiatica. At the same time, ethanol is relatively safe and environmentally friendly and can be easily removed in the subsequent processing process.

[0025] Extraction experiments were conducted on ethanol solutions of different concentrations. The experimental results showed that when the concentration of the ethanol solution was between 50-80%, the extraction rate of madecassoside was higher. Within this concentration range, ethanol can reduce the dissolution of impurities while ensuring its solubility, which is beneficial to subsequent separation and purification.

[0026] Temperature and time are also important factors in the extraction process. Experiments were conducted with different extraction temperatures and times. When the extraction temperature was between 50-70°C and the extraction time was 2-4 hours, a higher extraction efficiency could be obtained. Too low a temperature would result in a slow extraction speed, while too high a temperature might cause some of the active ingredients to decompose; too short an extraction time would result in incomplete extraction, while too long a time might increase the dissolution of impurities.

[0027] You can choose a multifunctional extraction tank and other equipment for extraction. This equipment can realize automatic control to ensure the stability and repeatability of the extraction process. During the extraction process, pay attention to the control of the stirring speed so that the Centella asiatica powder is fully in contact with the ethanol solution to improve the extraction efficiency.

[0028] A further solution of the present invention is that in step 2, the filtration uses a microporous filter membrane with a pore size of 0.2-0.5 microns; the centrifugal speed is 3000-5000 rpm, and the centrifugal time is 10-20 minutes.

[0029] The above beneficial effect lies in that a microporous filter membrane with a pore size of 0.2-0.5 microns is selected for filtration. This pore size filter membrane can effectively intercept larger impurity particles in the extract, such as undissolved plant residues, some macromolecular impurities, etc.

[0030] You can use plate and frame filter or filter element filter and other equipment for filtering operation. During the filtering process, the filtering pressure should be kept stable to avoid damage to the filter membrane caused by pressure fluctuation. At the same time, you should pay attention to the control of filtering speed. Too fast filtering speed may cause impurities to penetrate the filter membrane and affect the filtering effect.

[0031] The filtration effect was evaluated by testing the turbidity, impurity content and other indicators of the extract before and after filtration. The turbidity of the extract after filtration was significantly reduced, and the impurity content was reduced, providing a good foundation for subsequent centrifugal treatment.

[0032] A further solution of the present invention is that in step 2, the Centella asiatica extract is centrifuged in a tubular centrifuge or a disc centrifuge.

[0033] The above beneficial effect is that the centrifugal force generated by the centrifuge is utilized to cause the macromolecular impurities and insoluble substances in the extract to settle to the bottom of the centrifuge tube or on the drum wall of the centrifuge under the action of the centrifugal force, thereby achieving the purpose of separation.

[0034] Experiments have shown that a good separation effect can be achieved when the centrifugal speed is 3000-5000 rpm and the centrifugal time is 10-20 minutes. If the speed is too low or the centrifugal time is too short, the impurities will not be completely separated; if the speed is too high or the centrifugal time is too long, it may lead to the loss of effective ingredients or increased equipment loss.

[0035] You can choose a tubular centrifuge or a disc centrifuge for centrifugal operation. These devices have high separation efficiency and stability and can meet the needs of industrial production.

[0036] A further embodiment of the present invention is that in step three, the molecular weight cut-off of the ultrafiltration membrane is 1000-5000 Daltons.

[0037] The above beneficial effect lies in that an ultrafiltration membrane with a molecular weight cutoff of 1000-5000 Dalton is selected. The molecular weight of madecassoside is relatively small. By selecting an ultrafiltration membrane with a suitable molecular weight cutoff, impurities with a molecular weight greater than madecassoside, such as macromolecular substances such as proteins and polysaccharides, can be effectively retained, while small molecular substances such as madecassoside can be allowed to pass through the ultrafiltration membrane, thereby achieving preliminary separation and purification.

[0038] A further solution of the present invention is that in step three, the ultrafiltration membrane is an ultrafiltration membrane made of polysulfone or polyacrylonitrile; the operating pressure of the ultrafiltration membrane is 0.1-0.5 MPa; and the operating temperature is 20-40°C.

[0039] The above beneficial effect is that the material of the ultrafiltration membrane has an important influence on its performance. Ultrafiltration membranes made of polysulfone and polyacrylonitrile can be selected. These materials have good chemical stability, mechanical strength and pollution resistance, and can maintain good performance during long-term operation.

[0040] Control of operating pressure: In the ultrafiltration process, the operating pressure has an important influence on the ultrafiltration flux and separation effect. Generally speaking, when the operating pressure is between 0.1-0.5MPa, the ultrafiltration membrane can maintain a higher flux and better separation effect. Too low pressure will lead to a smaller ultrafiltration flux and affect production efficiency; too high pressure may damage the ultrafiltration membrane or cause impurities to penetrate the ultrafiltration membrane.

[0041] Temperature also has a certain impact on the ultrafiltration process. As the temperature rises, the ultrafiltration flux will increase, but the effect of temperature on the stability of madecassoside should also be considered. Generally speaking, it is more appropriate to control the temperature of the ultrafiltration process between 20-40℃.

[0042] A further embodiment of the present invention is that in step 4, the molecular weight cutoff of the nanofiltration membrane is 100-500 Daltons.

[0043] The above beneficial effect lies in selecting a nanofiltration membrane with a molecular weight cutoff of 100-500 Daltons. The molecular weight cutoff of the nanofiltration membrane is smaller than that of the ultrafiltration membrane, and can further intercept small molecular impurities in the permeate, while concentrating effective ingredients such as madecassoside.

[0044] Similar to ultrafiltration membranes, nanofiltration membranes can also be made of polysulfone and polyacrylonitrile. These nanofiltration membranes have good chemical corrosion resistance, thermal stability and mechanical strength, and can meet the requirements of the nanofiltration process.

[0045] A further solution of the present invention is that in step four, the operating pressure of the nanofiltration membrane is 0.5-2 MPa.

[0046] The above beneficial effect lies in the adjustment of operating pressure: the operating pressure of the nanofiltration process is generally between 0.5-2MPa. Compared with the ultrafiltration process, the nanofiltration process requires a higher operating pressure to ensure the flux and separation effect of the nanofiltration membrane. When adjusting the operating pressure, it is necessary to optimize it according to the performance of the nanofiltration membrane and the properties of the permeate to avoid adverse effects of too high or too low pressure on the nanofiltration process.

[0047] Control of concentration multiple: During the nanofiltration process, the concentration of madecassoside can be adjusted by controlling the concentration multiple. A concentration multiple that is too high may cause a sharp drop in the flux of the nanofiltration membrane, or even block the nanofiltration membrane; a concentration multiple that is too low may not achieve the expected concentration effect. Generally speaking, it is more appropriate to control the concentration multiple between 5-10 times.

[0048] A further embodiment of the present invention is that in step five, the drying process is carried out by spray drying or vacuum freeze drying.

[0049] The above beneficial effects are due to the principle of spray drying: the concentrated liquid is atomized into tiny droplets through an atomizer, and then the water is quickly evaporated in a hot air flow, so that the droplets are dried into a powdery product. Spray drying has the advantages of fast drying speed and good product quality, and is suitable for large-scale industrial production.

[0050] Choice of atomizer: You can choose centrifugal atomizer, pressure atomizer or airflow atomizer. Different types of atomizers have different atomization effects and application ranges. Centrifugal atomizers are suitable for high-viscosity concentrates; pressure atomizers are suitable for low-viscosity concentrates; airflow atomizers are suitable for occasions with high requirements for atomized particle size.

[0051] Optimization of drying parameters: During the spray drying process, it is necessary to optimize parameters such as inlet air temperature, outlet air temperature, and atomization pressure. Generally speaking, a better drying effect can be obtained when the inlet air temperature is between 150-200°C, the outlet air temperature is between 70-90°C, and the atomization pressure is between 0.2-0.5MPa.

[0052] Product quality control: Product quality is controlled by testing the moisture content, particle size distribution, madecassoside content and other indicators of the dried powder product to ensure that the product meets the relevant quality standards and requirements.

[0053] Principle of vacuum freeze drying: freeze the concentrated liquid first to turn the water into solid ice, and then sublime the solid ice directly into water vapor under vacuum conditions to achieve the purpose of drying. Vacuum freeze drying can maximize the activity and nutritional components of the product and is suitable for occasions with high requirements for product quality.

[0054] Control of the freezing process: During the freezing process, the freezing temperature and freezing speed must be controlled. Generally speaking, the freezing temperature is between -40--20℃ and the freezing speed is moderate, which can ensure that the concentrate is evenly frozen and avoid the formation of large ice crystals that affect the drying effect.

[0055] Design of vacuum system: Vacuum freeze drying requires an efficient vacuum system. The vacuum degree should generally be between 1-10Pa to ensure that solid ice can sublime smoothly. At the same time, the vacuum system should be regularly maintained to ensure its stable performance.

[0056] Monitoring of the drying process: During the vacuum freeze-drying process, the temperature, pressure, product weight and other indicators of the drying chamber should be monitored in real time. By monitoring these indicators, the drying parameters can be adjusted in time to ensure the smooth progress of the drying process.

[0057] Beneficial effects of the present invention:

[0058] 1. The present invention adopts membrane separation technology, which can effectively remove impurities and improve the purity of madecassoside.

[0059] 2. Compared with the traditional method, the present invention has the advantages of simple operation process, easy control and reduced production cost.

[0060] 3. The present invention can obtain high-content madecassoside by optimizing the extraction and membrane separation conditions, thereby improving the quality and added value of the product. DETAILED DESCRIPTION

[0061] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Example 1

[0063] A method for obtaining high-content madecassoside from Centella asiatica by membrane separation, comprising the following steps:

[0064] Step 1: Extraction:

[0065] Select fresh, mildew-free, disease-free and insect-free Centella asiatica as a raw material, wash and dry the Centella asiatica raw material and then grind it, the particle size of the grinded Centella asiatica powder is 20 mesh, and after the Centella asiatica raw material is grinded, an ethanol solution is used for extraction, the concentration of the ethanol solution is 50%, the extraction temperature is 50°C, and the extraction time is 2 hours to obtain a Centella asiatica extract;

[0066] Step 2: Preprocessing:

[0067] The Centella asiatica extract in step 1 is filtered and centrifuged to remove impurities and macromolecular substances therein; the filtration is performed using a microporous filter membrane with a pore size of 0.2 microns, the centrifugal speed is 3000 rpm, and the centrifugal time is 10 minutes; the Centella asiatica extract is centrifuged in a tubular centrifuge;

[0068] Step 3: Membrane separation:

[0069] The extract after the pretreatment in step 2 is subjected to ultrafiltration separation through an ultrafiltration membrane, and the impurities with a molecular weight cutoff greater than that of madecassoside are retained to obtain a permeate containing madecassoside; the molecular weight cutoff of the ultrafiltration membrane is 1000 Daltons; the ultrafiltration membrane is an ultrafiltration membrane made of polysulfone or polyacrylonitrile; the operating pressure of the ultrafiltration membrane is 0.1 MPa; and the operating temperature is 20°C;

[0070] Step 4: Concentration step:

[0071] The permeate in step 3 is concentrated through a nanofiltration membrane to obtain a concentrated solution with a high content of madecassoside; the molecular weight cutoff of the nanofiltration membrane is 100 Daltons; and the operating pressure of the nanofiltration membrane is 0.5 MPa;

[0072] Step 5: Drying step:

[0073] The concentrated solution in step 4 is dried by spray drying to obtain a solid product with a high content of madecassoside.

[0074] Example 2

[0075] A method for obtaining high-content madecassoside from Centella asiatica by membrane separation, comprising the following steps:

[0076] Step 1: Extraction:

[0077] Select fresh, mildew-free, disease-free and insect-free Centella asiatica as a raw material, wash and dry the Centella asiatica raw material and then grind it, the particle size of the grinded Centella asiatica powder is 60 mesh, and after the Centella asiatica raw material is grinded, an ethanol solution is used for extraction, the concentration of the ethanol solution is 60%, the extraction temperature is 60°C, and the extraction time is 3 hours to obtain a Centella asiatica extract;

[0078] Step 2: Preprocessing:

[0079] The Centella asiatica extract in step 1 is filtered and centrifuged to remove impurities and macromolecular substances therein; the filtration is performed using a microporous filter membrane with a pore size of 0.3 microns, the centrifugal speed is 4000 rpm, and the centrifugal time is 15 minutes; the Centella asiatica extract is centrifuged in a tubular centrifuge;

[0080] Step 3: Membrane separation:

[0081] The extract obtained after the pretreatment in step 2 is subjected to ultrafiltration separation through an ultrafiltration membrane, and the impurities with a molecular weight cutoff greater than that of madecassoside are retained to obtain a permeate containing madecassoside; the molecular weight cutoff of the ultrafiltration membrane is 3000 Daltons; the ultrafiltration membrane is an ultrafiltration membrane made of polysulfone or polyacrylonitrile; the operating pressure of the ultrafiltration membrane is 0.3 MPa; and the operating temperature is 30°C;

[0082] Step 4: Concentration step:

[0083] The permeate in step 3 is concentrated through a nanofiltration membrane to obtain a concentrated solution with a high content of madecassoside; the molecular weight cutoff of the nanofiltration membrane is 300 Daltons; and the operating pressure of the nanofiltration membrane is 1 MPa;

[0084] Step 5: Drying step:

[0085] The concentrated solution in step 4 is dried by spray drying to obtain a solid product with a high content of madecassoside.

[0086] Example 3

[0087] A method for obtaining high-content madecassoside from Centella asiatica by membrane separation, comprising the following steps:

[0088] Step 1: Extraction:

[0089] Select fresh, mildew-free, disease-free and insect-free Centella asiatica as a raw material, wash and dry the Centella asiatica raw material and then grind it, the particle size of the grinded Centella asiatica powder is 80 mesh, and after the Centella asiatica raw material is grinded, an ethanol solution is used for extraction, the concentration of the ethanol solution is 80%, the extraction temperature is 70°C, and the extraction time is 4 hours to obtain a Centella asiatica extract;

[0090] Step 2: Preprocessing:

[0091] The Centella asiatica extract in step 1 is filtered and centrifuged to remove impurities and macromolecular substances therein; the filtration is performed using a microporous filter membrane with a pore size of 0.5 microns, the centrifugal speed is 5000 rpm, and the centrifugal time is 20 minutes; the Centella asiatica extract is centrifuged in a disc centrifuge;

[0092] Step 3: Membrane separation:

[0093] The extract obtained after the pretreatment in step 2 is subjected to ultrafiltration separation through an ultrafiltration membrane, and the impurities with a molecular weight cutoff greater than that of madecassoside are retained to obtain a permeate containing madecassoside; the molecular weight cutoff of the ultrafiltration membrane is 5000 Daltons; the ultrafiltration membrane is made of polysulfone or polyacrylonitrile; the operating pressure of the ultrafiltration membrane is 0.5 MPa; and the operating temperature is 40°C;

[0094] Step 4: Concentration step:

[0095] The permeate in step 3 is concentrated through a nanofiltration membrane to obtain a concentrated solution with a high content of madecassoside; the molecular weight cutoff of the nanofiltration membrane is 500 Daltons; and the operating pressure of the nanofiltration membrane is 2 MPa;

[0096] Step 5: Drying step:

[0097] The concentrated solution in step 4 is dried by vacuum freeze drying to obtain a solid product with a high content of madecassoside.

[0098] The examples given in the present invention are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for obtaining high-content madecassoside from Centella asiatica by membrane separation, characterized in that: The following steps are involved: Step 1: Extraction: After the Centella asiatica raw material is crushed, an ethanol solution is used for extraction to obtain a Centella asiatica extract; Step 2: Preprocessing: Filtering and centrifuging the Centella asiatica extract in step 1 to remove impurities and macromolecular substances; Step 3: Membrane separation: The extract obtained after the pretreatment in step 2 is subjected to ultrafiltration separation through an ultrafiltration membrane to retain impurities with a molecular weight greater than that of madecassoside, thereby obtaining a permeate containing madecassoside; Step 4: Concentration step: The permeate in step 3 is concentrated through a nanofiltration membrane to obtain a concentrated solution with a high content of madecassoside; Step 5: Drying step: The concentrated liquid in step 4 is dried to obtain a solid product with a high content of madecassoside.

2. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 1, characterized in that: In step one, the Centella asiatica raw material is fresh, mildew-free, disease-free and insect-free Centella asiatica; the Centella asiatica raw material is firstly washed and dried and then crushed; the Centella asiatica raw material is crushed by mechanical crushing, and the particle size of the crushed Centella asiatica powder is 20-80 mesh.

3. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 2, characterized in that: In step 1, the concentration of the ethanol solution is 50-80%, the extraction temperature is 50-70° C., and the extraction time is 2-4 hours.

4. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 1, characterized in that: In step 2, the filtration uses a microporous filter membrane with a pore size of 0.2-0.5 microns; the centrifugal speed is 3000-5000 rpm, and the centrifugal time is 10-20 minutes.

5. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 4, characterized in that: In step 2, the Centella asiatica extract is centrifuged in a tubular centrifuge or a disc centrifuge.

6. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 1, characterized in that: In step three, the molecular weight cut-off of the ultrafiltration membrane is 1000-5000 Daltons.

7. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 6, characterized in that: In step three, the ultrafiltration membrane is an ultrafiltration membrane made of polysulfone or polyacrylonitrile; the operating pressure of the ultrafiltration membrane is 0.1-0.5 MPa; and the operating temperature is 20-40°C.

8. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 1, characterized in that: In step 4, the molecular weight cut-off of the nanofiltration membrane is 100-500 Daltons.

9. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 8, characterized in that: In step 4, the operating pressure of the nanofiltration membrane is 0.5-2 MPa.

10. The method for obtaining high-content madecassoside from Centella asiatica by membrane separation according to claim 1, characterized in that: In step five, the drying process is carried out by spray drying or vacuum freeze drying.