Daofu rhododendron essential oil, preparation method and application thereof

Abstract

The present invention discloses a Daofu Rhododendron essential oil, its preparation method, and application. The oil is prepared from leaves, buds, and / or annual branches of the Daofu Rhododendron plant through a subcritical extraction-molecular distillation refining process. The essential oil contains 25% or more canool and 64% or more total alcohol compounds. The essential oil also exhibits the following physical and chemical properties: a refractive index of 1.5, stable specific gravity, low peroxide value, saponification value of 15-10 mg / g, and iodine value of 145-141 g / 100 g. The essential oil can be used in skincare, cosmetics, and fragrance applications. The canool content in the essential oil is significantly higher than that of other prior art Daofu Rhododendron essential oil extraction methods. The total alcohol content is 64% or more, enriching the essential oil's chemical composition and significantly enhancing its biological activity. The essential oil also exhibits good optical stability, and the stable specific gravity indicates that the oil's composition is unlikely to change significantly during storage and use.

Description

Technical Field

[0001] The present invention belongs to the technical field of plant essential oil extraction, and relates to an essential oil with a high content of canthiol extracted from Rhododendron dawuense HPYang, an extraction method thereof, and applications of the essential oil in the fields of skin care products, cosmetics and fragrances. Background Art

[0002] Daofu Rhododendron is a rare plant that grows at high altitudes, primarily between 3,800 and 4,500 meters. Due to its unique habitat and biological characteristics, this plant is rich in chemical compounds and possesses a variety of potential biological activities. In recent years, with the deepening of research on natural plant resources, Daofu Rhododendron has gradually attracted attention, particularly in the fields of flavors, fragrances, and skincare.

[0003] Daofu rhododendron contains a variety of volatile components, including alkenes, alcohols, ketones, and aldehydes. These components not only give Daofu rhododendron its unique aroma but also possess potential biological activities. For example, some components have anti-inflammatory, antioxidant, and moisturizing properties. Studies have shown that the chemical composition of Daofu rhododendron varies significantly depending on altitude. The main components and content of Daofu rhododendron essential oils and hydrosols produced at altitudes of 3,800 and 4,000 meters are essentially the same, while those produced at 4,200 meters show significant differences in the types and content of components.

[0004] At present, the extraction methods of plant essential oils mainly include steam distillation, cold pressing, supercritical fluid extraction, etc. However, these methods have some limitations when extracting Daofu Rhododendron essential oil. For example, although steam distillation is simple to operate, the extraction time is long and may lead to the loss of some volatile components. Although supercritical fluid extraction has high extraction efficiency, the equipment cost is high and the operation is complicated. Daofu Rhododendron extract is obtained by vacuum freeze drying → crushing → heating and condensing → ultrasonic-assisted ethanol extraction → petroleum ether extraction → ethyl acetate extraction → macroporous adsorption resin separation → C18 column and Sephadex LH20 gel chromatography column purification; the process is complex and the equipment operation requirements are high, which is not suitable for industrial production. In addition, the existing methods often find it difficult to balance the aroma of the essential oil and the retention of bioactive components during the extraction process.

[0005] Due to its unique chemical composition and biological activity, Daofu Rhododendron essential oil has broad application potential. In the flavor and fragrance industry, Daofu Rhododendron essential oil can be used to blend high-end perfumes and cosmetic fragrances, providing a unique aroma experience. In the skincare industry, Daofu Rhododendron essential oil's anti-inflammatory, antioxidant, and moisturizing properties make it a valuable ingredient in the development of new skincare products. For example, certain components can promote water absorption and transport in the skin, improving its ability to retain moisture while also reducing inflammation and soothing skin discomfort. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a Daofu Rhododendron essential oil with a high content of white alcohol and a preparation method thereof. By optimizing raw material screening and the subcritical extraction-molecular distillation combined process, the essential oil yield, active ingredient content and stability are significantly improved, and its application in cosmetics, skin care products and other fields is expanded.

[0007] The inventors have continuously innovated and reformed through long-term exploration and attempts, as well as multiple experiments and efforts, to solve the above technical problems. The technical solution provided by the present invention is to provide a Daofu Rhododendron essential oil, which is prepared by selecting leaves, buds and / or annual branches of Daofu Rhododendron as raw materials; the content of scutellaria baicalensis in the essential oil is ≥25%; the total content of alcohol compounds is ≥64%, and the physicochemical properties of the essential oil are: refractive index 1.4908-1.5004, specific gravity 0.9633-0.9666, peroxide value 0.03mmol / kg-0.12mmol / kg, saponification value 15mg / g-10mg / g, and iodine value 145g / 100g-141g / 100g.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] The content of scutellaria baicalensis in the essential oil is ≥25%, which is significantly higher than other Daofu Rhododendron essential oil extraction methods in the existing technology; the total content of alcohol compounds is ≥64%, which not only enriches the chemical composition of the essential oil, but also significantly enhances its biological activity; the refractive index is 1.4908~1.5004, and the refractive index within this range indicates that the essential oil has good optical stability; the stable specific gravity indicates that the composition of the essential oil is not prone to significant changes during storage and use, ensuring the quality and stability of the product; the lower peroxide value indicates that the degree of oxidation of the essential oil is low, it has a longer shelf life and good stability, and reduces the quality degradation caused by oxidation; the saponification value reflects its good emulsification and stabilization properties in its application in cosmetics; the iodine value reflects the content of unsaturated bonds in the essential oil, and a higher iodine value indicates that the essential oil contains more unsaturated fatty acids, which have good antioxidant and moisturizing properties and can effectively delay skin aging.

[0010] The essential oil's stable physical and chemical properties allow it to maintain its chemical composition and biological activity under varying storage conditions, reducing quality degradation due to improper storage. Its stable physical and chemical properties ensure a longer shelf life and improved performance in skincare and cosmetics applications, reducing production costs and storage difficulties.

[0011] The high content of iris alcohol and the rich alcohol compounds give this essential oil significant biological activities, such as antioxidant, anti-inflammatory, and antibacterial properties. Furthermore, skin patch tests have shown that this essential oil is non-irritating to the skin and has good safety, making it suitable for the care and treatment of sensitive skin.

[0012] On the basis of the above technical solution, the present invention can also be improved as follows:

[0013] Furthermore: the essential oil contains the following ingredients and their mass percentages:

[0014] Acorus alcohol: 24.23%~26.78%,

[0015] Elemiol: 9.38% to 10.36%,

[0016] Ginsenol: 5.87% ~ 6.49%,

[0017] Guaiol: 5.57% to 6.15%,

[0018] Isoguaiacol: 5.30% to 5.86%,

[0019] α-pinene: 4.33% to 4.79%,

[0020] Kauran-16-ol: 3.74%~4.14%,

[0021] Eucalyptol: 2.83%~3.13%,

[0022] (2E,4S,7E)-4-Isopropyl-1,7-dimethylcyclodeca-2,7-dienol: 2.83%~3.13%,

[0023] β-Thurene: 2.82% to 3.12%,

[0024] Ethyl acetate: 2.78% to 3.08%,

[0025] β-elemene: 2.77% to 3.07%,

[0026] Isocalamusdiol: 2.59%~2.87%,

[0027] Bicyclo[5.2.0]nonane,2methylene4,8,8trimethyl4vinyl: 2.42%~2.68%,

[0028] Elemene: 2.20%~2.44%,

[0029] benzyl 2,6-dihydroxybenzoate: 1.99%~2.19%,

[0030] Bicyclosesquiphellandrene: 1.79%~1.97%,

[0031] Phytol: 1.41% to 1.55%,

[0032] Bornyl acetate: 1.40% to 1.54%,

[0033] beta-copaene: 1.33% ~ 1.47%,

[0034] 10ALPHA-hydroxy Japanese sea cucumber terpene-4-one: 1.18%~1.30%,

[0035] (3R,3aR,3bR,4S,7R,7aR)-4-Isopropyl-3,7-dimethyloctahydro-1H-cyclopenta[1,3]cyclopropa[1,2]benzen-3-ol: 1.04%~1.14%,

[0036] Santalene: 0.97%~1.07%,

[0037] Juniper naphthalene: 0.19%~0.21%.

[0038] Preferably, the essential oil comprises the following components and their mass percentages:

[0039] Acorus alcohol: 25.5%,

[0040] Elemiol: 9.87%,

[0041] Ginsenol: 6.18%,

[0042] Guaiol: 5.86%,

[0043] Isogaiol: 5.58%,

[0044] α-pinene: 4.56%,

[0045] Kauran-16-ol: 3.94%,

[0046] Eucalyptol: 2.98%,

[0047] (2E,4S,7E)-4-Isopropyl-1,7-dimethylcyclodeca-2,7-dienol: 2.98%,

[0048] β-Thurene: 2.97%,

[0049] Ethyl acetate: 2.93%,

[0050] β-elemene: 2.92%,

[0051] Isocalamdiol: 2.73%,

[0052] Bicyclo[5.2.0]nonane,2methylene4,8,8trimethyl4vinyl: 2.55%,

[0053] Elemene: 2.32%,

[0054] benzyl 2,6-dihydroxybenzoate: 2.09%,

[0055] Bicyclosesquiphellandrene: 1.88%,

[0056] Phytol: 1.48%,

[0057] Bornyl acetate: 1.47%,

[0058] beta-copaene: 1.4%,

[0059] 10ALPHA-hydroxy Japanese sea cucumber terpene-4-one: 1.24%,

[0060] (3R,3aR,3bR,4S,7R,7aR)-4-Isopropyl-3,7-dimethyloctahydro-1H-cyclopenta[1,3]cyclopropa[1,2]benzen-3-ol: 1.09%,

[0061] Santalene: 1.02%,

[0062] Juniper naphthalene: 0.2%.

[0063] Compared with the prior art, the beneficial effects of adopting the above further technical solution are:

[0064] This essential oil is rich in a variety of bioactive ingredients, among which the content of calendula alcohol is as high as 25.5%, which significantly enhances its antioxidant, anti-inflammatory and antibacterial effects. At the same time, the total content of alcohol compounds reaches 64%, including elemenol, guaiacol, etc. These ingredients give the essential oil excellent moisturizing, soothing and anti-aging properties. In addition, the essential oil also contains a variety of olefins, esters and ketones, such as α-pinene, ethyl acetate and isocalamdiol. These ingredients not only enrich the aroma of the essential oil, but also enhance its application effect in skin care products and cosmetics. Its stable physical and chemical properties (such as refractive index, specific gravity, saponification value, etc.) and low peroxide value ensure the stability of the essential oil during storage and use, extending its shelf life. Skin patch tests have verified that this essential oil is non-irritating to the skin and has good safety, making it suitable for the care of sensitive skin.

[0065] The present invention also provides a method for producing the aforementioned Daofu Rhododendron essential oil, comprising the following steps:

[0066] (1) Raw material pretreatment: Collect leaves, buds and / or annual branches of Rhododendron dafuense and crush them to a particle size of ≤2 mm;

[0067] (2) Subcritical extraction: The crushed raw material was mixed with butane at a material-liquid mass ratio of 1:3, and the extraction was repeated three times under the conditions of extraction pressure of 0.5 MPa, temperature of 45.0-45.2°C, and time of 35.2-35.3 min to obtain an extract;

[0068] (3) Molecular distillation: distill the extract under vacuum conditions of 0.059-0.060 mbar and a rotation speed of 193-194 r / min, and collect the light component, which is the essential oil.

[0069] Preferably, in the raw material pretreatment step, the weight ratio of leaves, buds and annual branches is 1:3:10.

[0070] Preferably, the Daofu rhododendron is selected from a growing area at an altitude of about 4,100 meters.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] This method achieves efficient and high-purity essential oil extraction through three carefully designed steps: raw material pretreatment, subcritical extraction, and molecular distillation. First, the leaves, buds, and annual branches of Daofu Rhododendron are selected as raw materials. These parts are rich in volatile components, and crushing them to a particle size of ≤2mm can significantly improve the subsequent extraction efficiency. Secondly, the subcritical extraction process is carried out under mild conditions to avoid the destruction of volatile components by high temperature. At the same time, through optimized process parameters (extraction pressure, temperature, time), the high content of white calendula and other active ingredients is ensured to be fully extracted. Finally, molecular distillation is carried out under high vacuum and precisely controlled rotation speed to effectively separate light components, further improving the purity and quality of the essential oil. This method not only significantly improves the yield of essential oil (≥2.93%), but also retains rich bioactive ingredients, while reducing production costs and energy consumption, providing efficient and stable technical support for the large-scale industrial production of Daofu Rhododendron essential oil.

[0073] On the basis of the above technical solution, the present invention can also be improved as follows:

[0074] Furthermore, the process parameters of the subcritical extraction were optimized by response surface methodology, and the regression model was:

[0075] Yield = 2.90 + 0.0083A + 0.0158B + 0.0367C - 0.0442D - 0.0025AB + 0.0075AC + 0.0300AD + 0.0250BD + 0.0675CD - 0.3663A 2 -0.1362B 2 -0.1362C 2 -0.1500D 2 ,

[0076] Among them, A is temperature (35-55°C), B is time (25-45 min), C is vacuum degree (0.01-0.1 mbar), and D is speed (150-250 r / min).

[0077] Compared with the prior art, the beneficial effects of adopting the above further technical solution are:

[0078] This optimized method not only significantly increases the yield of Daofu Rhododendron essential oil (≥2.93%) but also ensures the efficient extraction and retention of the active ingredients in the essential oil. Compared to traditional processes, this technical solution significantly improves production efficiency, reduces energy consumption and production costs, while ensuring the high quality and stability of the essential oil. This provides a scientific, efficient, and economically viable technical route for the large-scale industrial production of Daofu Rhododendron essential oil.

[0079] On the basis of the above technical solution, the present invention can also be improved as follows:

[0080] Furthermore, the vacuum control accuracy of the molecular distillation is ±0.001 mbar, the rotation speed deviation is ≤1 r / min, and the final essential oil yield is ≥2.93%.

[0081] Compared with the prior art, the beneficial effects of adopting the above further technical solution are:

[0082] High-precision process control not only effectively preserves the high content of scutellaria baicalensis and other active ingredients in Daofu Rhododendron essential oil, but also significantly reduces the influx of impurities and low-boiling-point components, thereby improving the quality and stability of the essential oil. Compared with traditional methods, this technical solution significantly improves essential oil extraction efficiency and product quality, reduces energy consumption and costs during the production process, and provides more efficient and economical technical support for the large-scale production and widespread application of Daofu Rhododendron essential oil.

[0083] The present invention also provides a use of the Daofu Rhododendron essential oil in the preparation of antibacterial cosmetics:

[0084] The cosmetic is used for inhibiting Staphylococcus aureus or Pseudomonas aeruginosa, the diameter of the inhibition zone is ≥10 mm, and the amount of essential oil added is 1.0% to 10.0%.

[0085] Compared with the prior art, the present invention has the following beneficial effects:

[0086] This essential oil can effectively inhibit important pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa, with an inhibition zone diameter of ≥10mm, indicating strong antibacterial activity. Adding 1.0% to 10.0% of essential oil to cosmetics can achieve a significant antibacterial effect, which not only reduces the use of traditional antibiotics but also reduces the risk of drug resistance. In addition, Daofu Rhododendron essential oil is derived from natural plants, has lower toxicity and side effects, and is safer. Therefore, the use of this essential oil in antibacterial cosmetics provides a new option for traditional antibacterial treatment, helps to develop safer and more effective antibacterial products, and is of great significance in combating the increasingly serious problem of drug resistance.

[0087] The present invention also provides an application of the Daofu azalea essential oil in fragrance products:

[0088] After the fragrance product is stored at room temperature for 3 to 6 months, the fragrance retention rate is greater than or equal to 90%, and the essential oil content is 3% to 15%.

[0089] Compared with the prior art, the present invention has the following beneficial effects:

[0090] After six months of storage at room temperature, the aroma retention rate remains at ≥90%, significantly higher than that of traditional fragrance ingredients. This demonstrates the exceptional antioxidant capacity and long-lasting aroma of Daofu Rhododendron essential oil. Furthermore, a significant aroma effect can be achieved with an essential oil content ranging from 3% to 15%, reducing reliance on other fragrances and lowering production costs. Its natural origin and high safety profile give it broad application prospects in the fragrance industry, offering consumers a longer-lasting, more natural fragrance experience while also providing new solutions for the innovation and upgrading of fragrance products.

[0091] The present invention also provides a use of the Daofu Rhododendron essential oil in preparing a stable cosmetic matrix:

[0092] The fatty acids of the essential oil in the matrix act synergistically so that after being stored at 25° C. in the dark for 12 months, the change rate of the physical and chemical properties is less than or equal to 5%.

[0093] Compared with the prior art, the present invention has the following beneficial effects:

[0094] The use of this essential oil in cosmetic matrices, thanks to the synergistic effect of its fatty acids, can keep the rate of change in physical and chemical properties within 5% or less after 12 months of storage at 25°C in the dark. This outstanding stability performance far exceeds that of traditional cosmetic raw materials, significantly extending the shelf life of the product and reducing quality degradation caused by ingredient deterioration. In addition, Daofu Rhododendron Essential Oil is rich in a variety of bioactive ingredients, such as daphne alcohol and guaiacol. These ingredients not only provide cosmetics with excellent moisturizing, antioxidant, and anti-inflammatory effects, but also enhance the overall performance and user experience of the product. Its natural origin and high safety make its application in the cosmetics field more advantageous, providing new solutions for the development of high-quality, long-lasting and stable cosmetics, and promoting green innovation and development in the cosmetics industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0096] Figure 1 It is the yield of Daofu Rhododendron essential oil in different parts.

[0097] Figure 2 This is the total ion current of sample S3.

[0098] Figure 3 It is the response surface and contour line of the interaction between extraction temperature and extraction time.

[0099] Figure 4 It is the response surface and contour line of the interaction between extraction temperature and vacuum degree.

[0100] Figure 5 It is the response surface and contour line of the interaction between extraction temperature and rotation speed.

[0101] Figure 6 It is the response surface and contour line of the interaction between extraction time and vacuum degree.

[0102] Figure 7 It is the response surface and contour line of the interaction between extraction time and rotation speed.

[0103] Figure 8 It is the response surface and contour line of the interaction between vacuum degree and speed.

[0104] Figure 9 This is the total ion current of sample S1.

[0105] Figure 10 This is the total ion current of sample S2.

[0106] Figure 11 It is a component stacking diagram.

[0107] Figure 12 This is the result of antibacterial experiment.

[0108] Figure 13 This is the result of skin patch test. DETAILED DESCRIPTION

[0109] In order to effectively develop and utilize the plant resource of Daofu Rhododendron, it is particularly important to accurately screen the raw material parts of Daofu Rhododendron with high volatile components. During the research and development process of the present invention, it was confirmed that the essential oil components of Daofu Rhododendron obtained by different extraction processes have significant differences.

[0110] In the preliminary experiment, steam distillation was used to extract essential oils from different parts of Daofu Rhododendron, including flowers, leaves, buds, annual branches and perennial branches.

[0111] Raw materials: Fresh Daofu Rhododendron plants were collected from plants that were growing normally at an altitude of 4100m in Daofu County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province. The flowers, leaves, buds, annual branches and perennial branches were collected separately.

[0112] Reagents: anhydrous ether and anhydrous sodium sulfate, all of analytical grade, were purchased from Dongguan Xunye Chemical Reagent Co., Ltd.

[0113] Instruments and equipment: 1L volatile oil extractor, Suixian Yongyang Glass Instrument Co., Ltd.; Woxin JJ-2 tissue crusher, Wuxi Woxin Instrument Manufacturing Co., Ltd.; AB-L analytical balance (accuracy 0.0001g), Mettler-Toledo Instrument (Shanghai) Co., Ltd.; BCD-215TD GA refrigerator, Qingdao Haier Co., Ltd.

[0114] Freshly collected Rhododendron daofuensis parts were minced separately. Using an electronic balance, 10.0000 g of each part was accurately weighed. The weighed samples were placed in a volatile oil extractor, and several glass beads were added. Distilled water was added at a material-to-liquid ratio of 1:6. The distillation apparatus was connected and distillation began for 6 hours. After distillation, the yield of essential oil from each part was recorded. The resulting essential oil was collected and dissolved in an appropriate amount of anhydrous ether. An appropriate amount of anhydrous sodium sulfate was then added to absorb the water. The treated essential oil was stored in a -20°C refrigerator overnight.

[0115] The yield of essential oil from each part of Daofu Rhododendron is as follows Figure 1 shown.

[0116] Figure 1 The results clearly show the yield of essential oil from different parts of Rhododendron daofuensis. Figure 1 As can be seen, the essential oil yields of different parts of the Daofu Rhododendron show significant differences. The buds have the highest yield, reaching 2.33%. This is likely because buds are in an active stage of plant growth, with vigorous cell division and metabolic activity, allowing them to accumulate large amounts of volatile compounds. The leaves and annual branches also have relatively high yields, at 1.89% and 2.17%, respectively, indicating that they are high-quality raw materials for essential oil extraction. The flowers have a relatively low yield of 0.45%. The perennial branches have the lowest yield, at 0.21%. The differences in essential oil yields among different parts are closely related to their respective physiological functions, cellular structures, and chemical composition distribution. In practical applications, high-oil-content parts can reduce costs, improve efficiency, and enhance the market competitiveness of products in industrial production.

[0117] During the research and development process, the inventors also tried to extract Daofu Rhododendron essential oil by ultrasonic-assisted steam distillation, with a yield of 2.11%, which is not much different from the 2.05% obtained by steam distillation. The chemical composition of the extracted essential oil sample S3 was analyzed, see Figure 2 The three components with the highest mass fractions were Δ-cadinene (17.03%), candiol (13.68%), and sabinene (12.27%). The odor of S3 differed significantly from that of the original Daofu Rhododendron plant, and the aroma lacked a pleasant character. Therefore, further research using ultrasonic-assisted steam distillation was abandoned.

[0118] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0119] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0120] In this example, the raw material, Daofu Rhododendron, was collected from a plant growing normally at an altitude of 4100 m in Daofu County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province. Leaves, buds, and annual branches were selected for use. The mass ratio of fresh samples was leaves: buds: annual branches = 1:3:10.

[0121] Reagents: anhydrous ether, anhydrous sodium sulfate, anhydrous ethanol, potassium hydroxide, potassium iodide, chloroform, glacial acetic acid, sodium thiosulfate, soluble starch, cyclohexane, iodine trichloride, concentrated hydrochloric acid, Dongguan Xunye Chemical Reagent Co., Ltd., all analytical grade; butane (purity > 99%), Puyang Hongtai Yang Material Co., Ltd.

[0122] Instruments and equipment: Woxin JJ-2 tissue crusher, Wuxi Woxin Instrument Manufacturing Co., Ltd.; AB-L analytical balance (precision 0.0001 g), Mettler-Toledo Instrument (Shanghai) Co., Ltd.; V-CBE-5L subcritical fluid extraction laboratory set, Henan Subcritical Biotechnology Co., Ltd.; Agilent 8890-7000D triple quadrupole gas chromatography-mass spectrometry, Agilent Technologies, USA; BCD-215TD GA refrigerator, Qingdao Haier Co., Ltd.; VTAVKL 70-5 molecular distillation equipment, Ruida Co., Ltd., Germany; DZF-6020 vacuum drying oven, Shanghai Hengke Instrument Co., Ltd.; Abbe refractometer WYA-2D 2WA-J, Shanghai Xiaoguang Instrument Co., Ltd.; relative density flask 250.0 mL, Beijing Tianlian Harmony Instrument Factory.

[0123] Example 1

[0124] This embodiment is an embodiment of the method for preparing Daofu Rhododendron essential oil of the present invention.

[0125] In order to improve the yield of Daofu rhododendron essential oil and reduce the production cost, this study used subcritical extraction-molecular distillation refining method and response surface methodology to study the key parameters of the preparation process, aiming to determine the optimal combination of process parameters and achieve efficient and high-quality preparation of Daofu rhododendron essential oil.

[0126] Test methods

[0127] Process flow: prepare raw materials → place in subcritical extraction device → add butane as extraction agent with a material-liquid mass ratio of 1:3 → adjust extraction pressure to 0.5Mpa → extraction temperature to 30-55℃ → extraction time to 20-45min → cycle extraction 3 times → obtain Daofu rhododendron extract (extract rate 5.33%) → transfer to molecular distillation device → set vacuum degree to 0.01-0.1mbar → set rotation speed to 150-250r / min → obtain Daofu rhododendron essential oil.

[0128] Response surface design: Based on the results of the previous single-factor experiment, with the yield of Daofu azalea essential oil as the response value, four factors with the greatest impact on the yield of Daofu azalea essential oil were selected as experimental factors: A - extraction temperature (°C), B - extraction time (min), C - vacuum degree (mbar), and D - rotation speed (r / min). A three-level experimental design was conducted using the Box-Behnken experimental design method for the four factors. The level codes and actual values of each factor are shown in Table 1:

[0129] Table 1 Factor level table

[0130]

[0131]

[0132] Essential oil yield calculation formula

[0133] Yield of Daofu Rhododendron Essential Oil = Mass of Daofu Rhododendron Essential Oil / Mass of Raw Materials × 100%

[0134] Response surface experiment results

[0135] The experiment was designed using the Box-Behnken model with four factors and three levels. A total of 27 groups of experiments were designed using the software, and the regression coefficients of each item were calculated. A mathematical regression model of the four factors, namely, the yield of Daofu Rhododendron essential oil and extraction temperature, extraction time, vacuum degree, and rotation speed, was established based on these regression coefficients. Multiple regression analysis was performed on the experimental data, and a quadratic polynomial regression model was established with the essential oil yield (%) as the dependent variable and the coding values of each factor as the independent variables. The obtained regression equation is: yield=2.90+0.0083A+0.0158B+0.0367C-0.0442D-0.0025AB+0.0075AC+0.0300AD+0.0250BD++0.0675CD-0.3663A2-0.1362B2-0.1362C2-0.1500D2. The function is analyzed and A=45.0755, B=35.2775, C=0.0597, and D=193.981 are obtained. At this time, the yield of Daofu Rhododendron essential oil is the largest, with a maximum value of 2.91%. That is, the optimal preparation process conditions are extraction temperature of 45.0755°C, extraction time of 35.2775min, vacuum degree of 0.0597mbar, and rotation speed of 193.981r / min. Experimental verification shows that the concentration of Daofu Rhododendron essential oil prepared under this condition is 2.93%, which is close to the theoretical value.

[0136] A variance analysis was performed on the regression models. The results showed that the models were highly significant (P < 0.01), and the lack-of-fit term was not significant (P > 0.05), indicating that the models fit the experimental data well and can be used to predict and analyze response values. A comparison of the F values of extraction temperature, extraction time, vacuum degree, and rotation speed also shows that rotation speed has the greatest impact, followed by vacuum degree, extraction time, and extraction temperature.

[0137] By drawing response surface diagrams and contour plots, the effects of the interactions between various factors on the yield of essential oil were analyzed intuitively. From the response surface diagrams and contour plots, it can be seen that the interactions between these factors have a great influence on the yield of Daofu Rhododendron essential oil. Figure 3 is the response surface and contour line of the interaction between extraction temperature and extraction time, Figure 4 is the response surface and contour line of the interaction between extraction temperature and vacuum degree, Figure 5 is the response surface and contour line of the interaction between extraction temperature and rotation speed, Figure 6 is the response surface and contour line of the interaction between extraction time and vacuum degree, Figure 7 is the response surface and contour line of the interaction between extraction time and rotation speed, Figure 8 is the response surface and contour line of the interaction between vacuum degree and speed. Figures 3 to 8 It can be seen that their functions are all upward convex surfaces, and the highest points all fall within the selected area, indicating that the area selected in this experiment is more appropriate.

[0138] Example 2

[0139] This example describes the preparation of Daofu Rhododendron essential oil using the optimized method described in the example. To further illustrate the technical effects of the present invention, this example also compares the effects of extracting Daofu Rhododendron essential oil using the traditional steam distillation method and the subcritical extraction-molecular distillation refining method of the present invention.

[0140] Process

[0141] Steam distillation method: prepare raw materials → place in steam distiller → add water at a material-liquid mass ratio of 1:6 → heat to about 100°C and start distillation → distill for 6 hours → collect distillation product → add anhydrous sodium sulfate for drying → obtain Daofu Rhododendron essential oil S1.

[0142] Subcritical extraction-molecular distillation refining method: raw material preparation → placing into subcritical extraction device → adding butane as extractant at a material-liquid mass ratio of 1:3 → adjusting the extraction pressure to 0.5 MPa → extraction temperature to 45°C → extraction time to 35 min → cyclic extraction 3 times → obtaining Daofu rhododendron extract (extract rate 5.33%) → transferring to molecular distillation device → vacuum degree set to 0.06 mbar → speed set to 193 r / min → obtaining Daofu rhododendron essential oil S2.

[0143] Gas chromatography-mass spectrometry conditions

[0144] Chromatographic column: HP-5MS (30 m × 0.25 mm × 0.25 μm); column temperature program: 50°C (2 min) - 5°C / min - 180°C (5 min) - 10°C / min - 300°C (10 min); injection port temperature: 250°C; injection mode: splitless; control mode: constant flow rate 1 mL / min; septum purge flow rate: 3 mL / min; ion source temperature: 230°C; interface temperature: 280°C; acquisition mode: SCAN; mass scanning range: m / z 20-480 amu. Qualitative analysis of volatile components was performed using the NIST17 standard library. All samples were tested under identical conditions, with three replicate injections. GC-MS total ion chromatograms and other information were recorded.

[0145] Daofu Rhododendron Essential Oil Yield

[0146] The yield of Daofu Rhododendron essential oil by steam distillation was 2.05% ± 0.03%, while the yield by subcritical extraction-molecular distillation refining was 2.93% ± 0.05%. The yield of Daofu Rhododendron essential oil prepared by subcritical extraction-molecular distillation refining was 42.9% higher than that by steam distillation.

[0147] The GC-MS method was used to analyze the Daofu azalea essential oil S1 prepared by steam distillation and the Daofu azalea essential oil S2 prepared by subcritical extraction-molecular distillation. The total ion current chromatograms are shown in Figure 2. Figure 9 、 Figure 10 shown.

[0148] When searching the standard spectral library for common peaks, components with a matching degree of >85% and a content of ≥1% were selected. The relative mass fractions of the components were calculated using the peak area normalization method. The NIST spectral library search and manual analysis were used, and the component analysis results are shown in Tables 2 and 3.

[0149] As shown in Tables 2 and 3, a total of 44 components were detected in the Daofu Rhododendron essential oils prepared by the two different methods. Of these, 25 components were detected in the steam distillation essential oil (S1) shown in Table 2, and 24 components were detected in the subcritical extraction-molecular distillation refining essential oil (S2) shown in Table 3. S1 and S2 share five components. The three components with the highest relative mass fractions in S1, from highest to lowest, are 3-carene (23.21%), sabinene (22.82%), and cane alcohol (5.00%). The three components with the highest mass fractions in S2 are cane alcohol (25.5%), elemenol (9.87%), and ginsenol (6.18%). The cane alcohol content in S2 is over five times that of S1.

[0150] Table 2 Composition analysis of essential oil S1 obtained by steam distillation

[0151]

[0152]

[0153] Table 3 Composition analysis of essential oil S2 obtained by subcritical extraction-molecular distillation purification method

[0154]

[0155]

[0156] The accumulation diagram of each sample component is shown in Figure 11 The Daofu Rhododendron essential oils obtained by the two methods are both composed of components such as alkenes, esters, alcohols, ketones, and alkanes, but the component contents of the two essential oils are different. S1 is the essential oil prepared by steam distillation, in which the olefin content is the highest (62.82%). S2 is the essential oil prepared by subcritical extraction-molecular distillation refining, in which the alcohol content is much higher than S1 (64.94%). The subcritical extraction-molecular distillation refining method has a lower temperature throughout the process, which better retains the high-boiling point component essential oil.

[0157] The yield and chemical composition of the Daofu Rhododendron essential oil extracted by the two methods differed significantly. The yield of the essential oil obtained by subcritical extraction-molecular distillation refining was 2.93% ± 0.05%. This was significantly higher than the 2.05% ± 0.03% obtained by steam distillation. The alcohol content in the essential oil extracted by subcritical extraction-molecular distillation refining (S2) was much higher than that of the essential oil extracted by steam distillation (S1). The alcohol content of the former reached 64.94%, more than three times that of S1, and the content of schisandra alcohol was more than five times that of S1. The high-boiling point component essential oil mainly contains sesquiterpenes, such as sesquiterpenes and sesquiterpenoid alcohols. It is currently believed that these molecules often have pharmacological effects such as antibacterial and antioxidant effects.

[0158] Multiple index tests of Daofu Rhododendron essential oil S1 and S2 at 0 days and 90 days

[0159] Determination of refractive index

[0160] Add essential oil to the surface of the refracting prism, cover the light-entering prism and lock the handwheel. Open the light shield, adjust the eyepiece, and when a clear crosshair appears, rotate the handwheel so that the light-dark dividing line has no color. Then continue to fine-tune the handwheel until the dividing line and the center of the crosshair coincide, and then adjust the condenser. The value read at this time is the refractive index at the oil temperature. If the measuring temperature is not 20℃, the formula n should be used. 20 =n t +(t-20)×0.00035 is converted to the refractive index at 20°C (where n 20 is the refractive index of essential oil at 20℃; n t is the refractive index of the essential oil at an oil temperature of t°C; t is the oil temperature during measurement, in °C; 0.00035 is the correction factor when the oil temperature is 20°C).

[0161] S1 rose from 1.4633 on the 0-day chart to 1.5257 on the 90-day chart, while S2 changed from 1.4908 to 1.5004. The large change in S1 suggests that its composition changes significantly during storage, while S2 is more stable.

[0162] Identification of odors

[0163] Five sensory evaluators will conduct the evaluation separately. An appropriate amount of essential oil sample is placed in a 50mL beaker, heated to 50°C, stirred, and smelled. If the sample has the inherent odor of the essential oil and no foreign odor, it is considered acceptable. If it fails, the foreign odor should be noted.

[0164] S1 initially had a very different and unpleasant odor from the original plant, and a strong sour taste after 90 days. S2 had a similar aroma to the original plant at both 0 and 90 days, indicating that S2 retained its odor much better than S1.

[0165] Determination of specific gravity

[0166] At 20°C, use the same relative density bottle to measure the masses of equal volumes of essential oil sample and distilled water. The ratio of the two masses is the specific gravity of the sample at that temperature.

[0167] S1 decreased from 0.9521 to 0.9242, and S2 changed from 0.9633 to 0.9666. The decrease of S1 was significant, indicating that its composition changed more than S2 during storage.

[0168] Determination of acid value

[0169] Accurately weigh 1.0000–5.000 g of sample into a 100 mL Erlenmeyer flask. Simultaneously conduct a blank test. Add 50 mL of a 1:1 ethanol-ether mixture to each of the two Erlenmeyer flasks containing the sample and blank, and shake to dissolve. Add 1–2 drops of phenolphthalein indicator and titrate with 0.1 mol / L potassium hydroxide standard solution until the solution turns pink and does not fade within 1 minute. This is the endpoint. Record the amount of 0.1 mol / L potassium hydroxide used.

[0170] The acid value calculation formula is: AV = c × (V1-V0) × 56.1 / m.

[0171] Where:

[0172] AV represents the acid value of oil;

[0173] c is the exact concentration of potassium hydroxide standard solution, mol / L;

[0174] V0 is the volume of potassium hydroxide standard solution consumed in the blank test, mL;

[0175] V1 is the volume of potassium hydroxide standard solution consumed by the sample, mL;

[0176] m is the sample mass, g;

[0177] 56.1 is the molar mass of potassium hydroxide, g / mol.

[0178] Acid value: S1 increased from 4.0 mg / g to 11.7 mg / g, and S2 increased from 4.2 mg / g to 12.7 mg / g. Both increased, indicating that oxidation or hydrolysis reactions occurred during storage and the acidic substances increased. The initial and final acid values of S2 were slightly higher than those of S1.

[0179] Determination of peroxide value

[0180] Accurately weigh 2.0000-3.0000g of sample and place it in a 250mL iodine volumetric flask. Add 30mL of a 1:1 mixture of chloroform and glacial acetic acid to the flask to dissolve the sample. Add 1mL of saturated potassium iodide solution, tightly cap the flask, gently shake for 30 seconds, and then place in the dark for 3 minutes. Remove the iodine volumetric flask, add 100mL of water, and shake well. Immediately titrate with sodium thiosulfate standard solution. When the solution turns yellow, add 1mL of starch indicator and continue titrating until the blue color disappears, which is the titration endpoint. Record the volume of sodium thiosulfate standard solution consumed and perform a blank test at the same time.

[0181] Peroxide value: S1 increased from 0.08mmol / kg to 0.25mmol / kg, and S2 increased from 0.03mmol / kg to 0.12mmol / kg, both indicating that oxidation reactions occurred, and the degree of oxidation of S1 was more serious.

[0182] The calculation formula for the peroxide value of oil and fat: P = c × (V1-V0) × 1000 / 2m.

[0183] Where:

[0184] P is the peroxide value of oil;

[0185] c is the exact concentration of sodium thiosulfate standard solution, mol / L;

[0186] V0 is the volume of sodium thiosulfate standard solution consumed in the blank test, mL;

[0187] V1 is the volume of sodium thiosulfate standard solution consumed by the sample, mL;

[0188] m is the sample mass, g.

[0189] Determination of saponification value (in KOH)

[0190] GB / T5534-2008

[0191] Saponification value: S1 is 0, while S2 decreases from 15 mg / g to 10 mg / g, indicating that the saponifiable components in S2 are reduced and components such as esters may change. This suggests that S1 does not contain fatty acids.

[0192] Determination of iodine value

[0193] GB / T5532-2022

[0194] Iodine value: S1 is 0, indicating that there is no or very low content of unsaturated fatty acids, and S2 drops from 145g / 100g to 141g / 100g, indicating that unsaturated bonds may react during storage.

[0195] Determination of fatty acids

[0196] GB 5009.168-2016 (Third Law)

[0197] In terms of fatty acid composition, S1 contained no fatty acids, while S2 had a variety of fatty acid data at both 0 and 90 days. The content of most fatty acids did not change much, but some fatty acids, such as stearic acid C18:0 and palmitoleic acid C16:1, showed significant changes. This indicates that the fatty acid composition of S2 was relatively stable during storage.

[0198] During storage, the physical, chemical, and fatty acid composition stability of Daofu azalea essential oil (S2), refined through subcritical extraction and molecular distillation, is generally superior to that of the essential oil prepared by steam distillation (S1). This may be due to differences in the composition and structure of the essential oils, resulting in differences in storage stability. It is also possible that the fatty acids play a stabilizing role, or act synergistically with other ingredients, resulting in S2's superior stability to S1. The absence of fatty acids in S1 may lead to differences in its application scenarios compared to S2. S1 may have unique uses in applications with specific requirements or restrictions on fatty acids. However, S2, with its diverse fatty acid content, including over 70% unsaturated fatty acids, may offer advantages in areas requiring fatty acids, such as skincare. S2 possesses the distinctive freshness of Daofu azalea, stimulating a pleasant olfactory response and creating a pleasant home atmosphere, making it a valuable addition to fragrance and home care products.

[0199] The above characteristics of Daofu Rhododendron Essential Oil indicate that it can be used in antioxidant skin care products, antibacterial cosmetics, fragrance products, and stable cosmetic matrices.

[0200] Example 3

[0201] This embodiment is an application example of the Daofu Rhododendron essential oil of the present invention in the preparation of antioxidant skin care products.

[0202] The amount of essential oil added in skin care products is 2%.

[0203] One of the main causes of skin aging is the intrusion of reactive oxygen species. Excessive reactive oxygen species not only damage human cellular tissues but also combine with proteins and lipids in the skin to form oxidants, ultimately contributing to skin aging. Substances with antioxidant activity can react with DPPH free radicals, causing them to pair with one electron and lose their activity, resulting in a lighter solution color and decreased absorbance. A higher DPPH scavenging rate indicates a stronger antioxidant capacity and a more effective reduction or elimination of DPPH free radicals.

[0204] The antioxidant test method refers to the standard TSHR006-2018. The specific operation is as follows: take 3 mL of DPPH-anhydrous ethanol solution with a concentration of 0.2 mmol / L in a cuvette, then add 1 mL of the test sample, mix well, and keep in the dark at room temperature for 30 minutes. The absorbance is measured at a wavelength of 517 nm, and the absorbance value is recorded as A1. The absorbance value when only 3 mL of anhydrous ethanol solution and 1 mL of test sample solution are added to the cuvette is recorded as A2, and the absorbance value when 3 mL of DPPH-anhydrous ethanol solution and 1 mL of anhydrous ethanol solution are added to the cuvette is recorded as A3.

[0205] DPPH free radical scavenging rate (%) = [1-(A1-A2) / A3] × 100%, taking the average value of three measurements.

[0206] The experimental results are shown in Table 4. In the table, the DPPH free radical of S2 is significantly higher than that of S1, indicating that S2 has greater antioxidant activity.

[0207] Table 4 DPPH radical scavenging rate of two Daofu rhododendron essential oil samples

[0208]

[0209]

[0210] Example 4

[0211] This example is an application example of the Daofu Rhododendron essential oil of the present invention in the preparation of antibacterial cosmetics, and compares the antibacterial effects of the two essential oils prepared in Example 2.

[0212] The cosmetic is used for inhibiting Staphylococcus aureus or Pseudomonas aeruginosa, and the added amount of essential oil is 5%.

[0213] In this embodiment,

[0214] Microbial test materials: Staphylococcus aureus, Escherichia coli, Candida albicans, Pseudomonas aeruginosa, and other strains were obtained from the China Center for the Collection of General Microbiological Cultures. Nutrient agar, nutrient broth, Sabouraud dextrose liquid medium, Sabouraud dextrose agar, and blank drug susceptibility strips were purchased from Changde Beekman Biotechnology Co., Ltd.

[0215] Activation of frozen bacterial strains: First, wipe the surface of the freeze-dried tube of the ampoule with an alcohol cotton cloth, then heat the ampoule on an alcohol lamp for 30 seconds, wipe the surface of the ampoule with wet cotton, and repeat the operation until cracks appear on the surface of the ampoule; then use tweezers to knock the top of the ampoule until the fracture breaks; draw 0.4mL of liquid culture medium into the ampoule, gently blow and pipette several times until the freeze-dried powder is completely dissolved, and transfer the dissolved bacterial suspension to the slant culture medium of the test tube.

[0216] Proliferation of bacterial strains: Use an inoculating loop to pick bacteria from the slant medium and inoculate into liquid culture medium. Then, culture in a constant temperature shaker. Incubate bacteria at 37°C for 24 hours and fungi at 28°C for 48 hours.

[0217] Filter paper diffusion assay: Soak a drug-sensitive paper disc in diluted essential oil. Draw up 100 μL of bacterial solution and evenly spread it onto a solid culture medium. Then, use tweezers to gently place the drug-sensitive paper disc on the solid culture medium. Place three parallel groups of cells in each culture medium, along with a drug-sensitive paper disc containing only saline as a control. Finally, place the cells in a constant temperature incubator for incubation. Bacteria are incubated at 37°C for 24 hours, while fungi (Candida albicans) are incubated at 28°C for 48 hours.

[0218] The experimental results are as follows Figure 12 shown. Figure 12 In the figure, a is the antibacterial test result of S1 against Staphylococcus aureus, b is the antibacterial test result of S1 against Escherichia coli, c is the antibacterial test result of S1 against Pseudomonas aeruginosa, d is the antibacterial test result of S1 against Candida albicans; e is the antibacterial test result of S2 against Staphylococcus aureus, f is the antibacterial test result of S2 against Escherichia coli, g is the antibacterial test result of S2 against Pseudomonas aeruginosa, h is the antibacterial test result of S2 against Candida albicans. In the figure, the paper pieces at positions 1, 2, and 3 are three parallel test groups soaked in essential oils, and position 4 is a drug-sensitive paper piece containing only physiological saline as a control. Figure 12 As can be seen, S1 and S2 have different antibacterial properties. S1 has a significant inhibitory effect on the Gram-positive bacteria Staphylococcus aureus and a certain inhibitory effect on the fungus Candida albicans, but has no inhibitory effect on the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. S2 also has a good inhibitory effect on Staphylococcus aureus and a certain inhibitory effect on the growth of Pseudomonas aeruginosa, but has no inhibitory effect on Escherichia coli and Candida albicans.

[0219] The difference in the antimicrobial spectrum between the two products may be due to their different ingredients. S1 is primarily composed of terpenes, while S2 is primarily composed of sesquiterpenoids. Adding Dawford Rhododendron essential oil to cosmetics can enhance the product's antimicrobial properties and reduce the need for additional preservatives.

[0220] Safety testing:

[0221] Nine volunteers were randomly selected for a patch test, following the human skin patch test method outlined in the 2015 Cosmetic Safety Technical Specifications. Cotton pads were cut into 1.00 cm x 1.00 cm pieces and soaked in Daofu Rhododendron essential oil. After the cotton pads were fully absorbed, they were applied to the inside of the volunteers' arms for 30 minutes. The volunteers were observed before and after the application for any noticeable redness, swelling, or irritation.

[0222] The results of the skin patch test are shown in Figure 13 After applying two types of Daofu rhododendron essential oils to the inner arms of nine volunteers for 30 minutes, two volunteers (No. 1 and No. 6) experienced slight redness and swelling on the skin where S1 was applied, while none of the volunteers who applied S2 experienced any redness or swelling. This suggests that S1 is more irritating to the skin, while S2 is non-irritating and has a good safety profile.

[0223] The antibacterial spectra of S1 and S2 are different. S2 is superior to S1 in antioxidant activity and safety, and is more suitable for use in cosmetics.

[0224] In the description of the present invention, it should be understood that "-" and "~" represent a range between two values, and the range includes the endpoints. For example, "AB" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0225] In the description of the present invention, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0226] In the description of the invention, the numerical values of time, temperature, ratio and mass involved may be based on actual measurements, standard parameters of equipment, simplified rounding results, or within an acceptable error range, ensuring the practicality and repeatability of the invention.

[0227] In the description of the present invention, the terms "about", "approximately" and "around" are used to express approximate values of numerical values or intervals, allowing a certain error to ensure the flexibility and practicality of the description while remaining within an acceptable error range, with the maximum error range not exceeding 10% of the corresponding numerical value or numerical range.

[0228] The above are merely preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims. Persons skilled in the art will appreciate that improvements and modifications may be made without departing from the spirit and scope of the present invention, and such improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A Daofu Rhododendron essential oil, characterized in that The essential oil is prepared by selecting leaves, buds and / or annual branches of Daofu Rhododendron as raw materials; the content of scutellaria baicalensis in the essential oil is 25%-26.78%; the total content of alcohol compounds is ≥64%, and the physicochemical properties of the essential oil are: refractive index 1.4908-1.5004, specific gravity 0.9633-0.9666, peroxide value 0.03mmol / kg-0.12mmol / kg, saponification value 10mg / g-15mg / g, and iodine value 141g / 100g-145g / 100g.

2. The Daofu Rhododendron essential oil according to claim 1, wherein The essential oil comprises the following ingredients and their mass percentages: Acorus alcohol: 25%~26.78%, Elemiol: 9.38%~10.36%, Ginsenol: 5.87%~6.49%, Guaiol: 5.57%~6.15%, Isogaicol: 5.30%~5.86%, α-pinene: 4.33%~4.79%, Kauran-16-ol: 3.74%~4.14%, Eucalyptol: 2.83%~3.13%, (2E,4S,7E)-4-Isopropyl-1,7-dimethylcyclodeca-2,7-dienol: 2.83%~3.13%, β-Serene: 2.82%~3.12%, Ethyl acetate: 2.78%~3.08%, β-elemene: 2.77%~3.07%, Isocalamdiol: 2.59%~2.87%, Bicyclo[5.2.0]nonane, 2methylene4,8,8trimethyl4vinyl: 2.42%~2.68%, Elemene: 2.20%~2.44%, benzyl 2,6-dihydroxybenzoate: 1.99%~2.19%, Bicyclosesquiphellandrene: 1.79%~1.97%, Phytol: 1.41%~1.55%, Bornyl acetate: 1.40%~1.54%, beta-copaene: 1.33%~1.47%, 10ALPHA-hydroxy Japanese sea cucumber terpene-4-one: 1.18%~1.30%, (3R,3aR,3bR,4S,7R,7aR)-4-Isopropyl-3,7-dimethyloctahydro-1H-cyclopenta[1,3]cyclopropa[1,2]benzen-3-ol: 1.04%~1.14%, Santalene: 0.97%~1.07%, Juniper naphthalene: 0.19%~0.21%.

3. The Daofu Rhododendron essential oil according to claim 1, wherein The essential oil comprises the following ingredients and their mass percentages: Acorus alcohol: 25.5%, Elemiol: 9.87%, Ginsenol: 6.18%, Guaiol: 5.86%, Isogaiol: 5.58%, α-pinene: 4.56%, Kauran-16-ol: 3.94%, Eucalyptol: 2.98%, (2E,4S,7E)-4-Isopropyl-1,7-dimethylcyclodeca-2,7-dienol: 2.98%, β-Thurene: 2.97%, Ethyl acetate: 2.93%, β-elemene: 2.92%, Isocalamusdiol: 2.73%, Bicyclo[5.2.0]nonane, 2methylene4,8,8trimethyl4vinyl: 2.55%, Elemene: 2.32%, benzyl 2,6-dihydroxybenzoate: 2.09%, Bicyclosesquiphellandrene: 1.88%, Phytol: 1.48%, Bornyl acetate: 1.47%, beta-copaene: 1.4%, 10ALPHA-hydroxy Japanese sea cucumber terpene-4-one: 1.24%, (3R,3aR,3bR,4S,7R,7aR)-4-Isopropyl-3,7-dimethyloctahydro-1H-cyclopenta[1,3]cyclopropa[1,2]benzen-3-ol: 1.09%, Santalene: 1.02%, Juniper naphthalene: 0.2%.

4. A method for preparing the Daofu Rhododendron essential oil according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) Raw material pretreatment: Collect leaves, buds and / or annual branches of Rhododendron daofuensis and crush them to a particle size of ≤2 mm; (2) Subcritical extraction: The crushed raw material was mixed with butane at a material-liquid mass ratio of 1:3, and the extraction was repeated three times under the conditions of extraction pressure of 0.5 MPa, temperature of 45.0-45.2°C, and time of 35.2-35.3 min to obtain an extract; (3) Molecular distillation: distill the extract under vacuum conditions of 0.059-0.060 mbar and a rotation speed of 193-194 r / min, and collect the light component, which is the essential oil.

5. The method according to claim 4, characterized in that The process parameters of the subcritical extraction were optimized by response surface methodology, and the regression model was: Yield = 2.90 + 0.0083A + 0.0158B + 0.0367C - 0.0442D - 0.0025AB + 0.0075AC + 0.0300AD + 0.0250BD + 0.0675CD - 0.3663A² - 0.1362B² - 0.1362C² - 0.1500D², Among them, A is temperature, B is time, C is vacuum degree, and D is speed.

6. The method according to claim 4, characterized in that The vacuum control accuracy of the molecular distillation is ±0.001 mbar, the rotation speed deviation is ≤1 r / min, and the final essential oil yield is ≥2.93%.

7. Use of the Daofu Rhododendron essential oil according to any one of claims 1 to 3 in the preparation of antioxidant skin care products, characterized in that: The amount of essential oil added to the skin care product is 0.5%-5.0%, and the DPPH free radical scavenging rate of the essential oil is ≥81.33%.

8. The use of the Daofu Rhododendron essential oil according to any one of claims 1 to 3 in the preparation of antibacterial cosmetics, characterized in that: The cosmetic is used for inhibiting Staphylococcus aureus or Pseudomonas aeruginosa, the diameter of the inhibition zone is ≥10 mm, and the amount of essential oil added is 1.0%-10.0%.

9. Use of the Daofu Rhododendron essential oil according to any one of claims 1 to 3 in a fragrance product, characterized in that: After the fragrance product is stored at room temperature for 3 to 6 months, the fragrance retention rate is ≥90%, and the essential oil content is 3%-15%.

10. Use of the Daofu Rhododendron essential oil according to any one of claims 1 to 3 in preparing a stable cosmetic matrix, characterized in that: The fatty acids of the essential oil in the matrix act synergistically so that after being stored at 25° C. in the dark for 12 months, the change rate of the physical and chemical properties is ≤5%.

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