Method for extracting gutta-percha from folium cortex eucommiae and application of gutta-percha

Abstract

The invention discloses a method for extracting gutta-percha from folium cortex eucommiae and application of the gutta-percha. The method comprises the following steps: crushing dried folium cortex eucommiae into folium cortex eucommiae powder and / or shredded folium cortex eucommiae; mixing the pretreated folium cortex eucommiae with a composite extracting agent, and stirring and extracting; filtering and separating the extracted mixture to obtain an extracting solution containing gutta-percha; purifying the obtained extracting solution to obtain a purified solution of the gutta-percha; freezing the obtained purified solution to precipitate the gutta-percha, and then separating the precipitate to obtain crude gutta-percha; and washing and decolorizing the obtained crude gutta-percha by using absolute ethyl alcohol, and then drying to obtain the pure gutta-percha. Compared with the prior art, by optimizing an extraction solvent system and a purification process, efficient and high-purity extraction of the gutta-percha is achieved without complex biological fermentation pretreatment or high-pressure harsh conditions, the process route is short, the solvent is green and safe, and the method is suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of eucommia ulmoides gum preparation, and particularly relates to a method for extracting eucommia ulmoides gum from eucommia ulmoides leaves and application. BACKGROUND

[0002] Eucommia ulmoides is a unique and valuable economic tree species and medicinal plant, and its leaves, bark and fruits are rich in a natural high molecular material, eucommia ulmoides gum (trans-1, 4-polyisoprene). Eucommia ulmoides gum has a broad application prospect in the fields of tire manufacturing, aerospace, medical materials and special functional materials due to its unique rubber-plastic dual nature, and is regarded as a strategic bio-based material to alleviate the shortage of natural rubber resources.

[0003] However, eucommia ulmoides gum is embedded in the solid lignocellulose cell wall in the form of solid particles, and is difficult to extract and separate, which is a key bottleneck restricting its industrial development. Traditional extraction methods mainly include chemical method, physical method and biological method. The chemical method such as solvent extraction method (using benzene, toluene, chloroform and other organic solvents) has relatively high extraction rate, but has problems of great solvent toxicity, difficult recovery, serious environmental pollution and safety hazards caused by high temperature and high pressure operation. For example, the method disclosed in CN104495840B uses benzene or toluene to extract under high pressure of 120-140 MPa. The physical method such as mechanical crushing and alkali cooking is often complex in process, seriously damages the structure of the gum, leads to the decline of product performance, and has high energy consumption and low purity. The biological method mainly uses microorganisms (such as edible fungi) or enzyme preparations to ferment the raw materials to destroy the cell wall. For example, CN118530472A discloses a method for extracting eucommia ulmoides gum by using white ghost fungus to ferment eucommia ulmoides leaves. Although this method is relatively environmentally friendly, it has problems of long fermentation period (usually 8-10 days), strict condition control, complex strain culture, complicated subsequent purification steps, and unstable extraction efficiency and gum purity.

[0004] In recent years, in order to overcome the above defects, researchers have been committed to developing green, efficient and low-cost extraction technologies. For example, some studies use complex enzymatic pretreatment combined with petroleum ether extraction to improve the extraction rate, but the cost of enzymes is high, and the process steps are still complex. Some research teams have proposed a new way of using green low eutectic solvent (such as lactic acid-zinc chloride) coupled with biological method, which has made progress in extraction efficiency and purity. However, the preparation, recovery and integration with traditional process of the low eutectic solvent still face challenges in industrialization.

[0005] Therefore, it is still a technical problem to be solved in the field to develop an eucommia ulmoides gum extraction method which is simple in process, mild in condition, high in extraction efficiency and product purity, environmentally friendly and easy to implement in industrialization. SUMMARY

[0006] The present application aims at overcoming the deficiencies of the prior art, and provides a method for extracting eucommia ulmoides gum from eucommia ulmoides leaves; the method realizes efficient and high-purity extraction of eucommia ulmoides gum under the condition of no complex biological fermentation pretreatment or high-pressure harsh condition, has a short process route, uses green and safe solvents, and is suitable for large-scale production.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0008] A method for extracting eucommia ulmoides gum from eucommia ulmoides leaves, comprising the following steps:

[0009] S1, raw material pretreatment: crushing dry eucommia ulmoides leaves into eucommia ulmoides leaf powder and / or eucommia ulmoides leaf silk;

[0010] S2, composite solvent extraction: mixing the eucommia ulmoides leaves pretreated in step S1 with a composite extraction agent, and stirring and extracting at a temperature of 60-80 DEG C;

[0011] S3, solid-liquid separation: filtering and separating the mixture after the extraction in step S2 to obtain an extraction liquid containing eucommia ulmoides gum;

[0012] S4, purification treatment: purifying the extraction liquid obtained in step S3 to obtain a purified solution of eucommia ulmoides gum;

[0013] S5, freeze gelation: freezing the purified solution obtained in step S4 at a temperature of-15 DEG C to-25 DEG C to precipitate and separate the eucommia ulmoides gum, and obtaining crude eucommia ulmoides gum;

[0014] S6, decolorization and drying: washing and decolorizing the crude eucommia ulmoides gum obtained in step S5 with anhydrous ethanol, and then drying, to obtain high-purity eucommia ulmoides gum.

[0015] Preferably, in step S2, the composite extraction agent comprises petroleum ether, sorbitol monooleate and gamma-valerolactone, and the volume ratio of the petroleum ether, sorbitol monooleate and gamma-valerolactone is 1:(0.05-0.1):(0.05-0.2), more preferably 1:0.05:0.1.

[0016] Preferably, in step S2, the solid-liquid ratio of the eucommia ulmoides leaves to the composite extraction agent is 1g:(5-20)mL; and the extraction time is 2-6 hours.

[0017] Preferably, the extraction process in step S2 is carried out under ultrasonic assistance, the ultrasonic power is 200-400 W, and the frequency is 20-40 KHz, so as to accelerate the diffusion of solutes and improve the extraction efficiency.

[0018] Preferably, in step S4, the purification reagent used in the purification treatment is a mixed solvent formed by L-proline, citric acid and glycerol, wherein the L-proline, citric acid and glycerol are mixed in a molar ratio of (0.5-1):(0.5-1):2; and the volume ratio of the purification reagent to the extract is 1:1.

[0019] L-proline is an amphoteric amino acid with amino and carboxyl groups, which is easily soluble in water, and the nitrogen atom and oxygen atom in the molecular structure of L-proline can act as hydrogen bond acceptors and donors. Citric acid is a tricarboxylic acid containing three carboxyl groups and one hydroxyl group, which is easily soluble in water and can provide abundant protons (H + ). Glycerol is a trihydric alcohol containing three hydroxyl groups, which has strong hygroscopicity and water solubility. When the three are mixed in a specific ratio, the protons provided by citric acid can strongly interact with the amino groups of L-proline, the carboxyl groups of L-proline and the hydroxyl groups of glycerol, forming a dynamic and complex hydrogen bond network and protonation environment. This network has strong solubility and high selectivity for the polar impurities (such as lignin degradation products, pigments, tannins, sugars, protein residues, etc.) commonly found in the extract of eucommia ulmoides rubber. These impurity molecules usually contain multiple hydroxyl groups, phenolic hydroxyl groups, carboxyl groups and other functional groups, which can easily embed and stably exist in the hydrogen bond network, thereby being efficiently extracted from the petroleum ether phase containing eucommia ulmoides rubber.

[0020] Preferably, in step S4, the purification reagent used in the purification treatment is ethanol with a volume concentration of 40%, and the volume ratio of the purification reagent to the extract is 1:1.

[0021] Preferably, in step S5, the freezing temperature is -18±2℃, and the freezing time is 10-12 hours.

[0022] Preferably, in step S5, the separation is performed by centrifugal separation, and the centrifugal speed is 9000-11000 rpm, and the centrifugal time is 8-12 minutes.

[0023] Preferably, in step S6, the drying is vacuum drying or normal temperature drying, and the drying temperature is 25-35℃, more preferably 25-30℃.

[0024] Preferably, in step S6, the yield of the eucommia ulmoides rubber obtained is ≥4%, more preferably 4-6%.

[0025] Preferably, in step S6, the purity of the eucommia ulmoides rubber obtained is ≥99%.

[0026] In addition, the present application also provides an application of eucommia ulmoides rubber, wherein the eucommia ulmoides rubber extracted by the above method is used for preparing tires, medical elastomers or shape memory materials.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] 1) Significantly Improved Extraction Efficiency and Purity: This invention abandons the complex pathways of existing technologies that rely on long-term bio-fermentation (e.g., 4-6 days), high-pressure solvent extraction (e.g., 120-140 MPa), or strong alkaline cooking (e.g., 110-160℃). Instead, it employs a petroleum ether / sorbitan monooleate / γ-valerol composite solvent for extraction under mild conditions of 60-80℃. This design has multiple synergistic effects: petroleum ether, as the main solvent, efficiently dissolves Eucommia gum; sorbitan monooleate, as a nonionic surfactant, significantly reduces the interfacial tension between the solvent and the plant cell wall, enhancing penetration and wetting, and promoting colloidal release; γ-valerol, as a green solvent, effectively swells the lignocellulose in the plant cell wall, physically loosening the bond between the colloidal substance and the matrix. This triple synergy of "dissolution-penetration-swelling" enables highly efficient dissolution of Eucommia gum without the need for drastic degradation. Subsequent treatment with specific purification reagents (such as the L-proline-citric acid-glycerol ternary system) and low-temperature freezing at -15℃ to -25℃ achieves highly selective removal of impurities such as pigments and lignin by utilizing differences in solubility and crystallization behavior. Therefore, this invention can achieve an extraction yield of ≥4% and a purity of over 99%, significantly superior to traditional solvent methods (low extraction rate, unstable purity) and biological methods (long cycle, extraction rate generally 2-3%).

[0029] 2) Significantly Simplified Process and Mildened Conditions: Existing technologies, whether it's mold-induced fermentation (cumbersome steps, several days in length), the all-biological enzymatic method (requiring multiple enzymes for step-by-step processing), or the combination of steam explosion and chemical cooking, all involve multi-step, long-cycle, and demanding pretreatment. This invention completely avoids these complex pretreatments. Its main process is simplified to: pulverization → compound solvent extraction → purification → freeze gelation → drying. All steps are carried out at normal pressure and medium to low temperatures (≤80℃). This not only significantly shortens the production cycle (from over ten days to 1-2 days) and improves production efficiency, but also significantly reduces energy consumption and equipment investment (eliminating the need for fermenters, autoclaves, steam explosion devices, etc.), making the process easier to scale up industrially in conventional chemical workshops.

[0030] 3) Fundamental Improvement in Environmental Friendliness and Production Safety: Traditional chemical methods heavily rely on toxic solvents such as benzene, toluene, and chloroform, resulting in significant environmental pollution and safety hazards. While biological methods are relatively environmentally friendly, they may generate fermentation wastewater and involve complex process control. The core solvents of this invention—petroleum ether, sorbitan monooleate, and γ-valerolactone—are all low-toxicity or biodegradable green chemicals. γ-valerolactone, in particular, is a bio-based solvent with outstanding environmental friendliness. The preferred purification step utilizes a ternary system of L-proline, citric acid, and glycerol, all of which are bio-based, edible, and green components, completely avoiding the use of heavy metal salts (such as zinc chloride) or strong acids and bases. The entire process does not generate difficult-to-treat organic wastewater or high-salt wastewater, and the solvents are easily recycled, truly practicing the principles of green chemistry and solving the core pain point of "severe environmental pollution" in traditional methods.

[0031] 4) Effective Protection of Product Molecular Structure and Properties: Harsh extraction conditions can damage the natural polymer structure of Eucommia ulmoides gum. For example, prolonged fermentation or strong alkaline cooking may lead to oxidation and molecular chain degradation of Eucommia ulmoides gum. This invention employs a gentle physicochemical method throughout the process (gentle heating, swelling with a green solvent, and low-temperature precipitation), minimizing the damage to the trans-1,4-polyisoprene molecular chains caused by strong shear, high temperature, and strong chemical reactions. This helps maintain the high degree of polymerization, intact crystalline structure, and natural rubber-plastic duality of Eucommia ulmoides gum, laying a material foundation for its application in high-end fields such as high-performance tires and shape memory materials. Attached Figure Description

[0032] Figure 1 The raw material for extracting Eucommia gum in this invention is dried Eucommia leaves.

[0033] Figure 2 This invention relates to Eucommia gum extracted from Eucommia leaves.

[0034] Figure 3 The infrared spectrum of the Eucommia ulmoides gum obtained in Example 1 of the present invention is shown. Detailed Implementation

[0035] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0036] In this invention, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0037] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0038] It should be understood that in various embodiments of the present invention, the order of the above-mentioned processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0039] According to a first aspect of the present invention, the present invention provides a method for extracting eucommia gum from eucommia leaves, comprising the following steps:

[0040] S1. Raw material pretreatment: The dried Eucommia ulmoides leaves are crushed into Eucommia ulmoides leaf powder and / or Eucommia ulmoides leaf shreds;

[0041] S2. Compound solvent extraction: The Eucommia ulmoides leaves pretreated in step S1 are mixed with the compound extractant and extracted by stirring at a temperature of 60-80°C; preferably, the stirring rate is 100-300 rpm, and the extraction operation is repeated at least 3 times.

[0042] S3. Solid-liquid separation: The mixture extracted in step S2 is filtered and separated to obtain an extract containing eucommia gum;

[0043] S4. Purification treatment: The extract obtained in step S3 is purified to obtain a purified solution of Eucommia ulmoides gum.

[0044] S5. Freezing and precipitating the gum: The purified solution obtained in step S4 is frozen at a temperature of -15℃ to -25℃ to precipitate the gum. The precipitate is then separated to obtain crude gum.

[0045] S6. Decolorization and drying: The crude Eucommia gum obtained in step S5 is washed and decolorized with anhydrous ethanol, and then dried to obtain high-purity Eucommia gum.

[0046] The method provided by this invention has the following advantages:

[0047] 1) High extraction efficiency and high purity: By employing a specific ratio of petroleum ether / sorbitan monooleate / γ-valerol composite solvent, this system exhibits excellent selectivity and solubility for Eucommia ulmoides gum. Simultaneously, the polarity of γ-valerol helps dissolve some pigments and impurities, enabling efficient extraction even under mild conditions (60-80℃). The subsequent low-temperature cryopreservation step utilizes the difference in solubility between Eucommia ulmoides gum and impurities at low temperatures to achieve efficient purification, eliminating the need for complex chromatography or repeated dissolution-precipitation operations. The Eucommia ulmoides gum obtained by this method can achieve a purity of over 99% and an extraction yield of over 4%.

[0048] 2) Simple process and mild conditions: This invention completely avoids the complex microbial fermentation (usually requiring several days), high-pressure extraction (e.g., exceeding 100 MPa), or strong acid and alkali treatment steps in existing technologies. The entire process only includes unit operations such as crushing, extraction, separation, purification, freezing, and drying. The process is short, simple to operate, and the reaction conditions are mild (atmospheric pressure, medium and low temperature), with low energy consumption.

[0049] 3) Green, environmentally friendly, and safe: The main solvents are petroleum ether / sorbitan monooleate / γ-valerol, which significantly reduces toxicity compared to toxic solvents such as benzene, toluene, and chloroform used in traditional methods. Furthermore, these solvents are biodegradable and environmentally friendly. The entire process does not generate large amounts of difficult-to-treat acidic or alkaline waste liquids or fermentation residues, thus reducing the pressure on waste treatment.

[0050] 4) Excellent product performance: Due to the mild extraction conditions, the damage to the Eucommia ulmoides gum molecular chain caused by strong mechanical shearing, high temperature or strong chemical action is avoided. The resulting Eucommia ulmoides gum has a high molecular weight and complete molecular structure, retaining its natural trans-1,4-polyisoprene structure. It has good crystallization performance, which is beneficial to subsequent processing and application.

[0051] 5) Easy to industrialize: The equipment used are all conventional chemical equipment (such as reactors, filters, freezers, and dryers), without the need for special bio-fermentation tanks or ultra-high pressure vessels. The process parameters are easy to control, making it suitable for scale-up and continuous production. Compared with the production cycle of more than ten days of existing biological extraction methods, the extraction time of Eucommia ulmoides gum in this invention is shortened to 1-2 days, significantly improving production efficiency.

[0052] In one embodiment of the present invention, in step S2, the composite extractant includes petroleum ether, sorbitan monooleate and γ-valerolactone, and the volume ratio of petroleum ether, sorbitan monooleate and γ-valerolactone is 1:(0.05~0.1):(0.05~0.2), more preferably 1:0.05:0.1.

[0053] To achieve efficient synergy, the content ratio of each component needs to be strictly controlled. If the sorbitol monooleate content is too low, the penetration and wetting effect will be insufficient; if it is too high, it may lead to over-emulsification, making subsequent separation difficult. Within this range, the γ-valerol content achieves optimal swelling without excessively altering the polarity of the solvent system, thus affecting the solubility of eucommia gum in petroleum ether. This optimized ratio ensures optimal extraction kinetics and extraction rate with the lowest additive dosage, balancing cost and efficiency.

[0054] The mechanism of action of the composite extractant formed by petroleum ether, sorbitol monooleate, and γ-valerol in this invention is as follows:

[0055] The superior performance of this compound extractant stems from its carefully designed "three-in-one" structure, where each component plays a unique and complementary role, together creating an efficient, mild, and highly selective extraction environment.

[0056] Petroleum ether: As a highly efficient solvent for dissolving and enriching substances, petroleum ether is a weakly polar, low-boiling-point general-purpose solvent with high selectivity for lipid-soluble substances. In the extraction of Eucommia ulmoides gum, the core role of petroleum ether is to efficiently dissolve the non-polar target product released from plant cells—trans-1,4-polyisoprene (Eucommia ulmoides gum)—and enrich it in the organic phase. Its low-boiling-point characteristic also facilitates subsequent solvent recovery, reducing energy consumption and the risk of degradation of heat-sensitive substances.

[0057] Sorbitol monooleate: As a surfactant and penetration enhancer, sorbitol monooleate is a nonionic surfactant, an oily liquid at room temperature, insoluble in water but soluble in hot oil and organic solvents. In this composite system, it plays a crucial role:

[0058] a) Reducing interfacial tension and enhancing wetting and penetration: Eucommia gum is encapsulated within the dense plant cell walls composed of lignin, cellulose, etc. Pure petroleum ether has limited wettability on polar cell walls. Adding a small amount of sorbitan monooleate significantly reduces the interfacial tension between the composite solvent and the plant solid surface due to its amphiphilic structure (lipophilic oleate chain and hydrophilic dehydrated sorbitan ring). This allows the solvent mixture to penetrate more quickly and deeply into the micropores and fiber bundles of Eucommia leaf powder, ensuring full contact with the matrix encapsulating the gum and opening physical channels for dissolution.

[0059] b) Possible micelle-assisted solubilization: In petroleum ether, sorbitan monooleate may form reverse micelles or microstructures. The hydrophilic core of these micro-aggregates may act on certain polar components in the cell wall (such as trace amounts of bound water and polar impurities), helping to loosen the cell wall structure or prevent the newly dissolved eucommia gum molecules from re-aggregating, thus playing a role in dispersion and stabilization.

[0060] γ-Valactone: As a green swelling agent and mass transfer promoter, γ-valactone is a recognized green solvent derived from biomass (such as straw cellulose) and exhibits excellent swelling properties for many polymeric materials. In this invention, its addition brings about a qualitative improvement:

[0061] a) Swelling of plant cell walls: γ-valerol can penetrate and swell the lignocellulose network in Eucommia ulmoides leaves. This swelling effect can physically expand the microstructure of the cell wall, destroy the mechanical entanglement and physical adsorption between Eucommia ulmoides gum fibers and the surrounding matrix such as lignin and hemicellulose, making the gum fibers easier to detach.

[0062] b) Promotes mass transfer: Studies have shown that γ-valerol can effectively promote the mass transfer of other reagents (such as catalysts and water) within the polymer matrix. During extraction, it likely promotes the diffusion of petroleum ether and sorbitan monooleate into the deeper layers of the cell wall, as well as the diffusion of dissolved eucommia gum into the bulk solvent, thereby accelerating the kinetics of the entire extraction process.

[0063] c) Environmental friendliness and mildness: As a bio-based green solvent, the addition of γ-valerol enhances the environmental friendliness of the entire composite system. Simultaneously, its mild swelling effect prevents damage to the Eucommia ulmoides gum molecular chains that may be caused by strong acids, strong alkalis, or harsh mechanical treatments, helping to maintain the natural polymer structure and properties of Eucommia ulmoides gum.

[0064] The synergistic effect among the components of the ternary extraction system: petroleum ether is responsible for the final dissolution and transport of the target compound; sorbitan monooleate acts as the "vanguard," improving the wetting and penetration of the raw material by the solvent and playing a role at the interface; γ-valerolactone acts as the "engineer," swelling and loosening the cell wall structure from the inside, and paving the way for mass transfer. The combination of these three components in a specific ratio achieves a synergistic enhancement of the entire chain of plant raw material extraction, from "surface wetting" to "internal structural loosening" and then to "efficient dissolution and transfer of the target compound," which is impossible to achieve with a single solvent or a poorly designed mixed solvent.

[0065] The composite extractant of this invention has several significant advantages over individual extractants such as petroleum ether, toluene, or ethanol:

[0066] 1) Higher extraction efficiency and yield: Due to the synergistic wetting, penetration, swelling, and mass transfer promoting effects, this composite solvent can more thoroughly contact and release the eucommia gum encapsulated in the cell wall. It is expected that under the same extraction time and temperature conditions, its extraction rate will be significantly higher than that of petroleum ether or ethanol alone. Ethanol itself has poor solubility for eucommia gum, resulting in a low extraction rate, while although petroleum ether has good solubility, its extraction may be incomplete due to limited penetration efficiency.

[0067] 2) Improved extraction selectivity and high potential for product purity: The system is designed with a focus on physical permeation, swelling, and dissolution rather than drastic chemical degradation. The addition of sorbitan monooleate and γ-valerol may help to separate Eucommia gum from other cell wall components more "cleanly," reducing the co-solubility of polar impurities such as pigments and polysaccharides. Petroleum ether itself has weak solubility for polar impurities; with the synergistic effect of the composite system, it is expected to directly yield crude extracts with lower impurity content, reducing the burden on subsequent purification.

[0068] 3) Milder processing conditions and potentially lower energy consumption: Efficient penetration and swelling mean that the same extraction effect can be achieved at lower temperatures or in shorter extraction times, thus reducing energy consumption. The swelling effect of γ-valerol reduces dependence on high temperatures, which is beneficial for energy conservation and protecting product quality.

[0069] 4) Enhanced environmental friendliness and safety: The main solvent, petroleum ether, has a low boiling point and is easily recyclable. The key additive, sorbitan monooleate, is a widely used food and cosmetic-grade emulsifier with low toxicity; γ-valerolactone is a green solvent. The entire composite system avoids the use of toxic solvents such as benzene and toluene, or highly corrosive reagents, thus better meeting the requirements of green chemistry and safe production.

[0070] 5) Solvent system stability and applicability: The three components are miscible and can form a homogeneous composite solvent, which is easy to operate. The formulation ratio has been optimized to ensure the synergistic effect is maximized, while avoiding the adverse effects that may be caused by an excessive amount of a certain component (such as over-emulsification leading to separation difficulties).

[0071] In summary, the petroleum ether / sorbitol monooleate / γ-valerol composite extractant provided by this invention, through ingenious component design and synergistic mechanism, achieves multiple improvements in efficiency, selectivity, environmental friendliness, and process friendliness in solving the technical challenge of Eucommia ulmoides gum extraction, providing a highly creative and promising new path for the green and efficient extraction of Eucommia ulmoides gum.

[0072] In one embodiment of the present invention, in step S2, the solid-liquid ratio of Eucommia ulmoides leaves to the compound extractant is 1g:(5-20)mL; the extraction time is 2-6 hours.

[0073] In one embodiment of the present invention, the extraction process in step S2 is carried out under ultrasonic assistance, with an ultrasonic power of 200-400W and a frequency of 20-40kHz, to accelerate solute diffusion and improve extraction efficiency. The ultrasonic cavitation effect generates strong mechanical vibrations and microjets, which can further disrupt the microstructure of plant cells, accelerate the penetration of the composite solvent into the raw material, and accelerate the diffusion of dissolved eucommia gum into the main solvent. This can significantly shorten the time required to achieve the same extraction rate, or further increase the extraction rate within the same time frame, and is an effective means of enhancing the mass transfer process.

[0074] In one embodiment of the present invention, in step S4, the purification reagent used for purification is a mixed solvent of L-proline, citric acid, and glycerol, with a molar ratio of (0.5~1):(0.5~1):2; and the volume ratio of the purification reagent to the extract is 1:1. This ternary purification reagent system is an innovative purification scheme of the present invention. Unlike existing systems, it is entirely composed of bio-based, non-toxic components. Its strong hydrogen bond network has extremely high solubility selectivity for polar impurities such as lignin, pigments, and polysaccharides, while being almost insoluble in non-polar Eucommia ulmoides gum. Through simple mixing and separation, most impurities can be "pulled" into the purification reagent, thereby greatly improving purification efficiency and replacing the cumbersome purification steps that require multiple precipitation and washing in the traditional method. This is the core guarantee for obtaining ultra-high purity (≥99%) Eucommia ulmoides gum.

[0075] The mechanism of action and advantages of the ternary mixed purification solvent formed by L-proline-citric acid-glycerol in this invention are as follows:

[0076] 1) Highly efficient dissolution and chemical action on impurities: The unique composition of this ternary purification solvent gives it a strong ability to dissolve and transform the main impurities in crude Eucommia ulmoides gum.

[0077] a) Selective dissolution of lignin: Citric acid, as a strong hydrogen bond donor, works synergistically with proline to effectively disrupt the ether and ester bonds in lignin, thus dissolving it. This differs from traditional alkaline methods or certain acid-based co-solvent extractions of lignin, which often lead to condensation. The addition of glycerol in this system may have a protective effect, reducing lignin condensation and making it easier to remove.

[0078] b) Removal of pigments and waxes: The polar environment of this ternary purification solvent can dissolve pigments such as chlorophyll and carotenoids, as well as waxes on plant surfaces. The presence of glycerol enhances the system's solubility for polar impurities.

[0079] c) Effects on hemicellulose and proteins: The mild acidic environment and hydrogen bond network can hydrolyze some of the hemicellulose and denature the proteins, thereby allowing them to detach from the colloidal surface and enter the liquid phase.

[0080] 2) The "repulsion" and protective effect on Eucommia ulmoides gum: Eucommia ulmoides gum (trans-1,4-polyisoprene) is a highly nonpolar crystalline polymer. The ternary purification solvent, however, is a highly polar hydrogen-bonded network system. According to the principle of "like dissolves like," it has extremely low solubility for nonpolar Eucommia ulmoides gum. Therefore, during purification, the ternary purification solvent primarily acts to encapsulate and adhere to polar impurities on the surface of Eucommia ulmoides gum, while the gum itself remains in a solid phase, achieving highly efficient selective separation. Simultaneously, the mild chemical conditions (non-strong acids, strong bases, or heavy metal salts) minimize damage to the Eucommia ulmoides gum molecular chains (especially its trans double bond structure) during purification, such as oxidation, hydrolysis, or degradation, thus protecting the gum's high degree of polymerization, intact crystalline structure, and natural rubber-plastic duality.

[0081] 3) Environmental friendliness and sustainability: All components of this system (L-proline, citric acid, and glycerol) are bio-based, biodegradable, and low-toxicity or non-toxic substances, fully complying with green chemistry principles. The entire purification process does not generate difficult-to-treat toxic waste liquids or high-salinity wastewater, significantly reducing the environmental footprint and purification costs. This has obvious environmental advantages compared to traditional chemical methods using toxic solvents such as benzene and toluene, and eutectic solvents that require the treatment of waste liquids containing metal salts. In addition, the purification reagent system has a large polarity difference from the extraction solvent petroleum ether, making it easy to separate and recover, thus reducing process costs.

[0082] In summary, the L-proline-citric acid-glycerol ternary purification reagent used in this invention operates on the core mechanism of constructing a highly polar microenvironment with a strong hydrogen-bonding network and protonation capability through a specific ratio. This generates a significant synergistic solvation effect, thereby achieving efficient and selective dissolution and extraction of various polar impurities. Simultaneously, this system, due to its significant polarity difference with the solvent used to dissolve Eucommia ulmoides gum, achieves gentle and efficient physical separation, perfectly preserving the natural structure of the gum. Compared to traditional purification agents such as ethanol, it offers comprehensive and significant advantages in purity improvement, product protection, environmental friendliness, and process synergy, representing an innovative solution to the key challenges of efficient and green purification of Eucommia ulmoides gum.

[0083] In one embodiment of the present invention, in step S4, the purification reagent used for purification is ethanol with a volume concentration of 40%, and the volume ratio of the purification reagent to the extract is 1:1.

[0084] In one embodiment of the present invention, in step S5, the freezing temperature is -18±2℃, and the freezing time is 10-12 hours. The low temperature of around -18℃ is the optimal temperature window for the crystallization and precipitation of Eucommia ulmoides gum, which ensures that it precipitates efficiently in a regular crystal form, while most impurities remain in the solution.

[0085] In one embodiment of the present invention, in step S5, the separation is performed by centrifugation at a speed of 9000-11000 rpm for 8-12 minutes. The specific centrifugation speed and time ensure complete collection of the tiny Eucommia ulmoides gum crystals while removing most of the residual mother liquor, thus improving the colloid yield and initial purity and creating favorable conditions for subsequent decolorization and drying.

[0086] In one embodiment of the present invention, in step S6, the drying is vacuum drying or room temperature drying, with a drying temperature of 25-35°C, more preferably 25-30°C. Low-temperature drying is used to avoid thermal oxidation or agglomeration of the eucommia gum due to high temperatures, thus protecting its surface properties and molecular weight. Vacuum drying can further remove residual trace solvents, ensuring the purity of the final product. This reflects the present invention's comprehensive protection of product quality throughout the entire process chain.

[0087] In one embodiment of the present invention, in step S6, the extraction yield of the Eucommia gum is ≥4%; more preferably 4~6%.

[0088] In one embodiment of the present invention, in step S6, the purity of the obtained Eucommia gum is ≥99%.

[0089] According to a second aspect of the present invention, the present invention also provides an application of Eucommia ulmoides gum, wherein the Eucommia ulmoides gum extracted by the above method is used to prepare tires, medical elastomers or shape memory materials.

[0090] The present invention will be further described in detail below with reference to specific embodiments.

[0091] Example 1

[0092] A method for extracting eucommia gum from eucommia leaves, the specific steps of which are as follows:

[0093] (1) Raw material pretreatment: Take 100.0g of commercially available dried Eucommia ulmoides leaves, crush them with a plant pulverizer, and pass them through a 40-mesh sieve to obtain Eucommia ulmoides leaf powder.

[0094] (2) Compound solvent extraction: The above-mentioned Eucommia ulmoides leaf powder was placed in a 2000mL three-necked flask equipped with a stirrer and reflux condenser, and a compound extraction solvent consisting of 500mL petroleum ether, 25mL sorbitan monooleate (Span 80), and 50mL γ-valerol (volume ratio 1:0.05:0.1) was added. Extraction was carried out for 4 hours at 200rpm under a water bath at 70℃. Simultaneously, ultrasonic treatment with a power of 300W and a frequency of 28kHz was applied.

[0095] (3) Solid-liquid separation: After extraction, filter the mixture while it is still hot using a Buchner funnel and qualitative filter paper to separate the residue and obtain a dark brown extract.

[0096] (4) Purification: Transfer the extract obtained in step (3) to a separatory funnel and add an equal volume (approximately 575 mL) of purification reagent. The purification reagent is prepared by mixing L-proline, citric acid, and glycerol in a molar ratio of 1:1:2 at 80°C with stirring. Vigorously shake at room temperature for 5 minutes and allow to stand for phase separation. The lower layer is a dark-colored purification reagent phase (rich in impurities), and the upper layer is a light yellow petroleum ether phase (containing eucommia gum). Separate and collect the upper petroleum ether phase.

[0097] (5) Freezing and gelation: The collected upper petroleum ether phase was transferred to a low-temperature freezer at -20°C and left to stand for 12 hours. A large amount of white flocculent precipitate was observed to precipitate out.

[0098] (6) Centrifugation: Centrifuge the above mixture at low temperature (0-5℃) (10000 rpm, 10 minutes), carefully discard the supernatant, and obtain a white precipitate (crude Eucommia gum).

[0099] (7) Decolorization and drying: Wash the precipitate three times with 20 mL of anhydrous ethanol pre-cooled to 0℃. Place the washed precipitate in a vacuum drying oven and dry it to constant weight at 30℃ and -0.09 MPa to obtain a white flake or powdered Eucommia ulmoides gum product, which is designated as sample E1.

[0100] After weighing, 4.63g of Eucommia ulmoides gum product was obtained, and the extraction yield was calculated to be 4.63%, with a purity of 99.5%.

[0101] Example 2

[0102] The difference between this embodiment and Embodiment 1 is that the proportion of the compound extractant and the extraction conditions are adjusted.

[0103] (1) The raw material pretreatment is the same as in Example 1.

[0104] (2) Compound solvent extraction: The compound extractant was prepared by mixing petroleum ether, sorbitol monooleate, and γ-valerol in a volume ratio of 1:0.1:0.2, with a total volume of 1000 mL. Extraction was carried out by stirring in a water bath at 60 °C for 6 hours without applying ultrasound.

[0105] Steps (3) to (7) are the same as in Example 1.

[0106] 4.28g of Eucommia ulmoides gum product was obtained, with an extraction yield of 4.28% and a purity of 99.1%.

[0107] Example 3

[0108] The difference between this embodiment and Embodiment 1 is that the proportion of the purification reagent is adjusted.

[0109] Steps (1) to (3) are the same as in Example 1.

[0110] (4) Purification treatment: The purification reagent is prepared by L-proline, citric acid and glycerol in a molar ratio of 0.5:0.5:2.

[0111] Steps (5) to (7) are the same as in Example 1.

[0112] 4.44g of Eucommia ulmoides gum product was obtained, with an extraction yield of 4.44% and a purity of 99.3%.

[0113] Comparative Example 1 (extraction with petroleum ether alone)

[0114] This comparative example is used to demonstrate the synergistic effect of the compound extractant compared to the single petroleum ether.

[0115] The steps are basically the same as in Example 1, except that in step (2), 575 mL of petroleum ether is used as the extraction agent, and sorbitol monooleate and γ-valerol are not added. Other conditions (temperature 70°C, time 4 h, ultrasound assistance) are the same as in Example 1.

[0116] Results: A total of 3.41g of Eucommia ulmoides gum product was obtained, with an extraction yield of 3.41% and a purity of 96.8%. The product color was slightly darker than that of the sample in Example 1.

[0117] Comparative Example 2 (purified from single ethanol)

[0118] This comparative example is used to demonstrate the advantages of ternary purification reagents over traditional purification reagents.

[0119] The steps are basically the same as in Example 1, except that: Step (4) purification: the extract obtained in step (3) is transferred to a separatory funnel, an equal volume of 40% ethanol aqueous solution is added, the mixture is vigorously shaken at room temperature for 5 minutes, and allowed to stand for separation. The upper petroleum ether phase is separated and collected.

[0120] Results: 4.05 g of Eucommia ulmoides gum product was obtained, with an extraction yield of 4.05% and a purity of 98.4%. The extraction yield (4.05%) and purity (98.4%) were both lower than those of Example 1 (4.63%, 99.5%) using a ternary purification reagent.

[0121] Comparative Example 3 (referencing the bio-fermentation method of patent CN118530472A)

[0122] This comparative example is used to compare the efficiency and cycle time of existing biological methods. The method disclosed in the prior art document CN118530472A was simulated: a xylan culture medium was prepared, inoculated with liquid *Coprinus eucommia* strain, and mixed with 100.0 g of dried *Eucommia ulmoides* leaves from the same batch. The mixture was then fermented in a solid-state incubator at 28°C for 9 days. After drying the fermentation product, it was extracted by hot reflux at 90°C for 24 hours using petroleum ether as a solvent. The extract was then cooled at -20°C to separate the gel and dried.

[0123] Results: The entire process took more than 10 days. The final yield of Eucommia ulmoides gum was 3.02%, with a purity of 95.2%. The process was complex, time-consuming, and far less efficient than this invention.

[0124] Comparative Example 4 (without freezing gelation step)

[0125] This comparative example is used to demonstrate the critical role of the cryopreservation gelation step in purity.

[0126] The steps are basically the same as in Example 1, except that in step (5), freezing is not performed. Instead, the purified petroleum ether phase is rotary evaporated at 70°C and concentrated to about 1 / 5 of its original volume. Then, 3 times the volume of cold methanol (pre-cooled at -20°C) is slowly added to the concentrate to precipitate it. The subsequent washing and drying steps are the same.

[0127] Results: The obtained Eucommia gum product was a light yellow viscous substance that clumped after drying. The final product yield was 4.10g, with an extraction rate of 4.10%, but the purity was only 96.1%, and the product had poor color and appearance.

[0128] Comparative Example 5 (The compound extractant is petroleum ether + sorbitol monooleate)

[0129] This comparative example is used to demonstrate the indispensability of γ-valerolactone in the ternary compound extractant.

[0130] The steps are basically the same as in Example 1, except that in step (2), the compound extractant consists of 500 mL of petroleum ether and 25 mL of sorbitol monooleate (i.e., without γ-valerol).

[0131] Results: 3.78g of Eucommia ulmoides gum product was obtained, with an extraction yield of 3.78% and a purity of 97.5%. The extraction yield was lower than that in Example 1.

[0132] Comparative Example 6 (The compound extractant is petroleum ether + γ-valerol)

[0133] This comparative example is used to demonstrate the indispensability of sorbitol monooleate in the ternary compound extractant.

[0134] The steps are basically the same as in Example 1, except that in step (2), the compound extractant consists of 500 mL of petroleum ether and 50 mL of γ-valerol (i.e., it does not contain sorbitol monooleate).

[0135] Results: 3.92 g of Eucommia ulmoides gum product was obtained, with an extraction yield of 3.92% and a purity of 98.0%. The extraction rate was still lower than that in Example 1, and the filtration rate of the extract was slow, indicating that the permeability may be poor.

[0136] Comparative Example 7 (purification reagent: glycerol + L-proline)

[0137] This comparative example is used to demonstrate the indispensability of citric acid in ternary purification reagents.

[0138] The steps are basically the same as in Example 1, except that in step (4), the purification reagent is made by mixing glycerol and L-proline in a molar ratio of 2:1 (i.e., without citric acid).

[0139] Results: After purification, the two phases did not separate clearly, indicating poor impurity removal. The final Eucommia ulmoides gum product was dark in color, with an extraction yield of 4.25% but a purity of only 97.2%.

[0140] Comparative Example 8 (purification reagent: glycerol + citric acid)

[0141] This comparative example is used to demonstrate the indispensability of L-proline in ternary purification reagents.

[0142] The steps are basically the same as in Example 1, except that in step (4), the purification reagent is made by mixing glycerol and citric acid in a molar ratio of 2:1 (i.e., without L-proline).

[0143] Results: The lower aqueous phase was lighter in color after purification, but a small amount of eucommia gum was also observed to flocculate in the petroleum ether phase. The final yield of eucommia gum was 4.15%, with a purity of 97.8%.

[0144] Test methods and results analysis

[0145] 1. Determination of extraction yield

[0146] The extraction yield was calculated using the following formula: Eucommia gum extraction yield (%) = (mass of dried Eucommia gum product / mass of dried Eucommia leaves before extraction) × 100%. The extraction yield data for each example and comparative example are summarized in Table 1.

[0147] 2. Purity determination

[0148] The purity of Eucommia ulmoides gum was determined and calculated according to GB / T8086-2008 "Determination of Impurity Content in Natural Raw Rubber". The specific steps were as follows: Approximately 2g (m0) of dried Eucommia ulmoides gum sample was accurately weighed and placed in an Erlenmeyer flask. An appropriate amount of rubber solvent containing 2-thiol-benzothiazole was added, and the mixture was heated to dissolve. The sample was filtered through a pre-dried, constant-weight filter sieve with a pore size of 45μm (mass m1). The filter sieve and the retained impurities were washed with petroleum ether, dried to constant weight, and the total mass m2 was obtained. The purity calculation formula was: Purity (%) = 1 - [(m2 - m1) / m0] × 100%; where: m0 is the mass of the Eucommia ulmoides gum sample (g); m1 is the mass of the empty sieve (g); and m2 is the total mass of the empty sieve and impurities (g). The purity data of each example and comparative example are summarized in Table 1.

[0149] 3. Infrared spectroscopy characterization

[0150] The Eucommia ulmoides gum sample E1 obtained in Example 1 was characterized using Fourier transform infrared spectroscopy (FT-IR). Approximately 1 mg of the sample was mixed with 200 mg of potassium bromide (KBr), ground, and then compressed into tablets. The tablets were prepared at wavenumbers of 4000-400 cm⁻¹. - ¹ Scan within the range, resolution 2.0 cm - ¹. The obtained spectrum is as follows Figure 3 As shown.

[0151] Depend on Figure 3 It can be seen that the obtained Eucommia ulmoides gum spectrum is at 2854 cm⁻¹. -1 and 2918cm -1 The position is the stretching vibration of the methyl group, 2848 cm⁻¹ -1 The point is the stretching vibration of the methylene group, 1669 cm⁻¹ -1 This indicates the presence of stretching vibrations of carbon-carbon double bonds, occurring at 800–1500 cm⁻¹. -1 Numerous absorption peaks were observed within the range, indicating the vibrations and coupling between carbon-hydrogen bonds, carbon-carbon single bonds, and methyl and methylene groups. The spectrum was largely consistent with that of standard trans-1,4-polyisoprene, and no obvious impurity characteristic peaks were observed, confirming that the obtained product was high-purity Eucommia ulmoides gum.

[0152] Table 1 Comparison of extraction effects between the examples and comparative examples

[0153] No. Yield (%) Purity (%) Example 1 4.63 99.5 Example 2 4.28 99.1 Example 3 4.44 99.3 Comparative Example 1 3.41 96.8 Comparative Example 2 4.05 98.4 Comparative Example 3 3.02 95.2 Comparative Example 4 4.10 96.1 Comparative Example 5 3.78 97.5 Comparative Example 6 3.92 98.0 Comparative Example 7 4.25 97.2 Comparative Example 8 4.15 97.8

[0154] Based on the data in Table 1 and the accompanying drawings, the beneficial effects of this invention have been fully verified:

[0155] 1) Synergistic effect of the ternary composite extractant: The extraction yield of Example 1 (4.63%) was significantly higher than that of Comparative Example 1 (3.41%), which used petroleum ether alone. Meanwhile, Comparative Examples 5 and 6, which lacked either component (γ-valerolactone or sorbitol monooleate), also had lower extraction yields (3.78%, 3.92%) than Example 1. This demonstrates that the combination of petroleum ether, sorbitol monooleate, and γ-valerolactone in a specific ratio produces a synergistic effect of "1+1+1>3". Sorbitol monooleate improves the wetting and penetration of the raw material by the solvent, while the swelling effect of γ-valerolactone on the cell wall promotes mass transfer; together, they help petroleum ether to dissolve Eucommia ulmoides gum more efficiently and thoroughly.

[0156] 2) High selectivity of the ternary purification reagent: Example 1 used an L-proline / citric acid / glycerol ternary purification reagent, achieving the highest purity (99.5%). Comparative Example 2, purified using conventional 40% ethanol, had a slightly lower purity (98.4%). Furthermore, Comparative Examples 7 and 8, lacking either citric acid or L-proline, showed significantly lower purity (97.2%, 97.8%), demonstrating that the strong hydrogen-bonded network synergistically formed by the ternary components exhibits unique and highly efficient solubility selectivity for impurities such as lignin and pigments, which is key to achieving ultra-high purity.

[0157] 3) Necessity of the cryogenic separation step: Comparative Example 4 used a method of solvent evaporation followed by methanol precipitation. Although the yield was similar to that of Example 1, the purity was significantly reduced to 96.1%, and the product properties were poor. This indicates that cryogenic separation at low temperatures of -18°C to -25°C can utilize the significant difference in crystallization behavior between Eucommia ulmoides gum and impurities at low temperatures to achieve purer crystallization separation, which is an indispensable step to ensure high purity.

[0158] 4) Advanced overall process: The embodiments of this invention achieved an extraction yield of over 4% and a purity of over 99% within approximately 24 hours. In contrast, the existing bio-fermentation method simulated in Comparative Example 3 had a cycle of over 10 days, with a yield of only 3.02% and a purity of only 95.2%. This fully demonstrates the overwhelming advantages of this invention in terms of "simple process, high efficiency, and short cycle." Furthermore, this invention uses petroleum ether, bio-based additives, and green purification agents throughout the process, avoiding highly toxic solvents such as benzene and toluene, as well as strong acids and alkalis, demonstrating outstanding environmental friendliness.

[0159] 5) Product structure integrity: such as Figure 3 As shown, the infrared spectrum of the Eucommia ulmoides gum product obtained in Example 1 is basically consistent with the spectrum of standard trans-1,4-polyisoprene, with no degradation or oxidation characteristic peaks, indicating that the mild process conditions of the present invention effectively protect the natural polymer chain structure of Eucommia ulmoides gum.

[0160] In summary, this invention, through the organic combination of a specific ratio of ternary composite extractant, an innovative ternary purification reagent, and an optimized cryopreservation process, successfully provides a new extraction route for Eucommia ulmoides gum that is highly efficient (≥4%), produces products with high purity (≥99%), has a short processing cycle (1-2 days), is environmentally friendly, and easily industrialized. The comparative data from the examples and comparative cases strongly support the scope of the claims and demonstrate that this invention represents a significant advancement and inventive step compared to existing technologies.

[0161] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for extracting eucommia gum from eucommia leaves, characterized in that: Includes the following steps: S1. Raw material pretreatment: The dried Eucommia ulmoides leaves are crushed into Eucommia ulmoides leaf powder and / or Eucommia ulmoides leaf shreds; S2. Compound solvent extraction: The Eucommia ulmoides leaves pretreated in step S1 are mixed with the compound extractant and extracted by stirring at a temperature of 60~80℃. S3. Solid-liquid separation: The mixture extracted in step S2 is filtered and separated to obtain an extract containing eucommia gum; S4. Purification treatment: The extract obtained in step S3 is purified to obtain a purified solution of Eucommia ulmoides gum. S5. Freezing and precipitating the gum: The purified solution obtained in step S4 is frozen at a temperature of -15℃ to -25℃ to precipitate the gum. The precipitate is then separated to obtain crude gum. S6. Decolorization and drying: The crude Eucommia gum obtained in step S5 is decolorized with anhydrous ethanol and then dried to obtain pure Eucommia gum.

2. The method for extracting eucommia gum from Eucommia leaves according to claim 1, characterized in that: In step S2, the composite extractant includes petroleum ether, sorbitan monooleate and γ-valerolactone, and the volume ratio of petroleum ether, sorbitan monooleate and γ-valerolactone is 1:(0.05~0.1):(0.05~0.2).

3. The method for extracting eucommia gum from Eucommia leaves according to claim 1 or 2, characterized in that: In step S2, the solid-liquid ratio of Eucommia ulmoides leaves to the compound extractant is 1g:(5-20)mL; the extraction time is 2-6 hours.

4. The method for extracting eucommia gum from Eucommia leaves according to claim 1, characterized in that: The extraction process in step S2 is carried out under ultrasonic assistance, with an ultrasonic power of 200-400W and a frequency of 20-40KHz.

5. The method for extracting eucommia gum from eucommia leaves according to claim 1, characterized in that: In step S4, the purification reagent used in the purification process is a mixed solvent of L-proline, citric acid and glycerol, and the molar ratio of L-proline, citric acid and glycerol is (0.5~1): (0.5~1): 2; and the volume ratio of the purification reagent to the extract is 1:

1.

6. The method for extracting eucommia gum from eucommia leaves according to claim 1, characterized in that: In step S5, the freezing temperature is -18±2℃ and the freezing time is 10-12 hours.

7. The method for extracting eucommia gum from eucommia leaves according to claim 1, characterized in that: In step S5, the separation is carried out by centrifugation, with a centrifugation speed of 9000-11000 rpm and a centrifugation time of 8-12 minutes.

8. The method for extracting eucommia gum from eucommia leaves according to claim 1, characterized in that: In step S6, the drying is vacuum drying or room temperature drying, and the drying temperature is 25-35℃.

9. The method for extracting eucommia gum from eucommia leaves according to claim 1, characterized in that: In step S6, the extraction yield of the obtained Eucommia gum is ≥4%; the purity of the obtained Eucommia gum is ≥99%.

10. An application of Eucommia ulmoides gum, characterized in that: Eucommia gum extracted by the method according to any one of claims 1 to 9 can be used to prepare tires, medical elastomers or shape memory materials.

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