Rhododendron molle essential oil as well as preparation method and application thereof

Abstract

The invention discloses Rhododendron molle essential oil and a preparation method and application thereof, and the Rhododendron molle essential oil is prepared by selecting leaves, buds and / or annual branches of Rhododendron molle as raw materials through a subcritical extraction-molecular distillation refining method. The content of calamus alcohol in the essential oil is greater than or equal to 25%; the total content of the alcohol compounds is greater than or equal to 64%, the physicochemical properties of the essential oil are as follows: the refractive index is 1.5, the specific gravity is stable, the peroxide value is low, the saponification value is 15-10mg / g, the iodine value is 145-141 g / 100g, and the essential oil can be applied to the fields of skin care products, cosmetics and fragrances. The content of calamus alcohol in the essential oil is obviously higher than that of other Rhododendron molle essential oil extraction methods in the prior art; the total content of the alcohol compounds is greater than or equal to 64%, so that the chemical composition of the essential oil is enriched, and the biological activity of the essential oil is remarkably improved; the essential oil has good optical stability; the stable specific gravity shows that the components of the essential oil are not easy to change remarkably in the storage and use processes.

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 acoranol extracted from Rhododendron dawuense H.P.Yang, an extraction method thereof, and its applications in the fields of skin care products, cosmetics and fragrances. Background Art

[0002] Rhododendron dawuense is a rare plant growing in high-altitude areas, mainly distributed in areas with an altitude of 3,800 to 4,500 meters. Due to its unique growth environment and biological characteristics, this plant contains rich chemical components and has various potential biological activities. In recent years, with the continuous in-depth research on natural plant resources, Rhododendron dawuense has gradually attracted attention, especially in the fields of essence and skin care products.

[0003] Rhododendron dawuense contains various volatile components, including alkenes, alcohols, ketones, aldehydes, etc. These components not only endow Rhododendron dawuense with a unique aroma, but also have potential biological activities. For example, certain components have anti-inflammatory, antioxidant and moisturizing effects. Research shows that the chemical components of Rhododendron dawuense vary significantly with different altitudes. The main components and contents of the essential oil and hydrosol of Rhododendron dawuense at an altitude of 3,800 meters and 4,000 meters are basically the same, while there are obvious differences in the types and contents of components in the essential oil and hydrosol of Rhododendron dawuense at an altitude of 4,200 meters.

[0004] At present, the extraction methods of plant essential oils mainly include steam distillation method, cold pressing method, supercritical fluid extraction method, etc. However, these methods have some limitations in extracting the essential oil of Rhododendron dawuense. For example, although the steam distillation method is simple to operate, the extraction time is long and it may cause the loss of some volatile components. Although the supercritical fluid extraction method has high extraction efficiency, the equipment cost is high and the operation is complex. The Rhododendron dawuense extract is obtained through processes such as vacuum freeze-drying → pulverization → heating and condensation → ultrasonic-assisted ethanol extraction → petroleum ether extraction → ethyl acetate extraction → macroporous adsorption resin separation → purification by C18 column and Sephadex LH20 gel chromatography column; the process is complex and the equipment operation requirements are high, which is not suitable for industrial production. In addition, existing methods often have difficulty in taking into account both 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 activities, the essential oil of Rhododendron dawuense has extensive application potential. In the field of fragrances and flavors, the essential oil of Rhododendron dawuense can be used to formulate high-end perfume and cosmetic fragrances, providing a unique aroma experience. In the skincare field, the anti-inflammatory, antioxidant, and moisturizing effects of the essential oil of Rhododendron dawuense make it an important raw material for developing new skincare products. For example, certain components can promote skin moisture absorption and transportation, improve the skin's moisturizing ability, while reducing skin inflammation and soothing skin discomfort. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an essential oil of Rhododendron dawuense with a high content of acorenol and its preparation method. By optimizing raw material screening and the combined process of subcritical extraction - molecular distillation, the essential oil yield, the content of active ingredients, and stability are significantly improved, and its applications in the fields of cosmetics, skincare products, etc. are expanded.

[0007] The technical solution provided by the present invention for solving the above technical problems through the long-term exploration and attempts by the inventors, as well as multiple experiments and efforts, and continuous reform and innovation, is to provide an essential oil of Rhododendron dawuense, which is prepared by selecting the leaves, buds, and / or one-year-old branches of Rhododendron dawuense as raw materials; the content of acorenol 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 0.03 mmol / kg - 0.12 mmol / kg, saponification value 15 mg / g - 10 mg / g, iodine value 145 g / 100 g - 141 g / 100 g.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0009] The content of acorenol in the essential oil is ≥25%, which is significantly higher than other extraction methods of the essential oil of Rhododendron dawuense in the prior art; the total content of alcohol compounds is ≥64%, which not only enriches the chemical composition of the essential oil but also significantly improves its biological activity; the refractive index of 1.4908 - 1.5004 indicates that the essential oil has good optical stability within this range; the stable specific gravity indicates that the components of the essential oil are 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, having a longer shelf life and good stability, reducing the quality decline caused by oxidation; the saponification value reflects its good emulsifying and stabilizing properties in the application of cosmetics; the iodine value reflects the content of unsaturated bonds in the essential oil, and the higher iodine value indicates that the essential oil contains more unsaturated fatty acids, and these components have good antioxidant and moisturizing properties, which can effectively delay skin aging.

[0010] The physicochemical properties of this essential oil are stable, enabling it to maintain its chemical composition and biological activity under different storage conditions, reducing the quality degradation caused by improper storage. Its stable physicochemical properties endow it with a longer shelf life and better usage effects in the applications in the fields of skin care products and cosmetics, reducing the production cost and storage difficulty.

[0011] High contents of acorenol and rich alcohol compounds endow this essential oil with remarkable biological activities, such as antioxidant, anti-inflammatory, antibacterial, etc. At the same time, verified by skin patch tests, this essential oil is non-irritating to the skin, has good safety, and is suitable for the care and treatment of sensitive skin.

[0012] Based on the above technical solutions, the present invention can also be improved as follows:

[0013] Further: The essential oil contains the following components and their mass percentages:

[0014] Acorenol: 24.23% - 26.78%,

[0015] Elemol: 9.38% - 10.36%,

[0016] Ginsenol: 5.87% - 6.49%,

[0017] Guaiol: 5.57% - 6.15%,

[0018] Isoguaiol: 5.30% - 5.86%,

[0019] α-Pinene: 4.33% - 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-Selinene: 2.82% - 3.12%,

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

[0025] β-Elemene: 2.77% - 3.07%,

[0026] Isowendiol: 2.59% - 2.87%,

[0027] Bicyclo[5.2.0]nonane, 2-methylene-4,8,8-trimethyl-4-vinyl: 2.42% - 2.68%,

[0028] Elemolonone: 2.20% - 2.44%,

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

[0030] Bicyclosesquiphellandrene: 1.79% - 1.97%,

[0031] Phytol: 1.41% - 1.55%,

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

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

[0034] 10ALPHA-hydroxyholost-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 contains the following components and their mass percentages:

[0039] Acoranol: 25.5%,

[0040] Elemol: 9.87%,

[0041] Ginsenol: 6.18%,

[0042] Guaiol: 5.86%,

[0043] Isoguaiol: 5.58%,

[0044] alpha-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-Selinene: 2.97%,

[0049] Ethyl acetate: 2.93%,

[0050] β-Elemene: 2.92%,

[0051] Isocolumbianadin: 2.73%,

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

[0053] Elemene ketone: 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-Hydroxyholost-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 solutions are:

[0064] This essential oil is rich in various bioactive components. Among them, the content of acoronal is as high as 25.5%, significantly enhancing its antioxidant, anti-inflammatory, and antibacterial effects. At the same time, the total content of alcohol compounds reaches 64%, including elemol, guaiol, etc. These components endow the essential oil with excellent moisturizing, soothing, and anti-aging properties. In addition, the essential oil also contains various terpenes, esters, and ketones, such as α-pinene, ethyl acetate, and isoasarone diol, etc. These components not only enrich the aroma of the essential oil but also enhance its application effects 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. Verified by skin patch tests, 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 the aforementioned Rhododendron dawuense essential oil, comprising the following steps:

[0066] (1) Raw material pretreatment: Collect the leaves, buds, or / and one-year-old branches of Rhododendron dawuense, and crush them to a particle size of ≤2 mm;

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

[0068] (3) Molecular distillation: Distill the extract under the conditions of a vacuum degree of 0.059 - 0.060 mbar and a rotation speed of 193 - 194 r / min, and collect the light components as the aforementioned essential oil.

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

[0070] Preferably, the Rhododendron dawuense is selected from the growth area at an altitude of about 4100 meters.

[0071] Compared with the prior art, the beneficial effects of the present invention are:

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

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

[0074] Furthermore: The process parameters of the subcritical extraction are optimized by the response surface method, and its regression model is:

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

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

[0078] This optimization method not only significantly increases the yield of Rhododendron dawuense essential oil (≥2.93%), but also ensures the efficient extraction and retention of active components in the essential oil. Compared with the traditional process, this technical solution greatly improves the production efficiency, reduces energy consumption and production costs, and at the same time ensures the high quality and stability of the essential oil, providing a scientific, efficient and economically feasible technical route for the large-scale industrial production of Rhododendron dawuense essential oil.

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

[0080] Furthermore, the control accuracy of the vacuum degree of the molecular distillation is ±0.001 mbar, the rotational 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 solutions are as follows:

[0082] The high-precision process control not only effectively retains the high content of acorenol and other active ingredients in the essential oil of Rhododendron dawuense, but also significantly reduces the mixing of impurities and low-boiling components, thereby improving the quality and stability of the essential oil. Compared with the traditional method, this technical solution greatly improves the extraction efficiency and product quality of the essential oil, reduces the energy consumption and cost in the production process, and provides a more efficient and economical technical guarantee for the large-scale production and wide application of the essential oil of Rhododendron dawuense.

[0083] The present invention also provides an application of the essential oil of Rhododendron dawuense in the preparation of antibacterial cosmetics:

[0084] The cosmetics are used to inhibit Staphylococcus aureus or Pseudomonas aeruginosa, the diameter of the inhibition zone is ≥10 mm, and the addition amount of the essential oil is 1.0% - 10.0%.

[0085] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0086] This essential oil can effectively inhibit important pathogenic bacteria such as Staphylococcus aureus and Pseudomonas aeruginosa, and the diameter of its inhibition zone is ≥10 mm, indicating strong antibacterial activity. Adding 1.0% - 10.0% of the essential oil to the cosmetics can achieve significant antibacterial effects, which not only reduces the usage amount of traditional antibiotics but also reduces the risk of generating drug resistance. In addition, the essential oil of Rhododendron dawuense is derived from natural plants, has low toxicity and side effects, and has higher safety. Therefore, the application 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 for combating the increasingly serious problem of drug resistance.

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

[0088] After being stored at room temperature for 3 - 6 months, the aroma retention rate of the fragrance product is ≥90%, and the essential oil content is 3% - 15%.

[0089] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0090] After being stored at room temperature for 6 months, the aroma retention rate can still reach ≥90%, which is much higher than that of traditional fragrance raw materials. This indicates that the essential oil of Rhododendron dawuense has excellent antioxidant ability and aroma persistence. In addition, a significant aroma effect can be achieved when the essential oil content is in the range of 3% - 15%, reducing the dependence on other fragrances and lowering the production cost. Its natural source and high safety make it have broad application prospects in the fragrance field, providing consumers with a more lasting and natural fragrance experience, and also offering new solutions for the innovation and upgrading of fragrance products.

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

[0092] The synergistic effect of the fatty acids of the essential oil in the matrix enables the physicochemical property change rate to be ≤5% after being stored at 25°C in the dark for 12 months.

[0093] Compared with the prior art, the beneficial effects of the present invention are:

[0094] The application of this essential oil in a cosmetic matrix, due to the synergistic effect of its fatty acids, can control the physicochemical property change rate to be ≤5% after being stored at 25°C in the dark for 12 months. This excellent stability performance is far better than traditional cosmetic raw materials, significantly extending the product shelf life and reducing the quality decline problem caused by ingredient deterioration. In addition, the essential oil of Rhododendron dawuense is rich in various bioactive components, such as acoranol, guaiol, etc. These components not only endow the cosmetics with good moisturizing, antioxidant and anti-inflammatory effects, but also can improve the overall performance and user experience of the product. Its natural source and high safety make its application in the cosmetic field more advantageous, providing new solutions for the development of high-quality and long-term stable cosmetics, and promoting the green innovation and development of the cosmetic 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 will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, so they should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0096] Figure 1 is the yield of the essential oil of Rhododendron dawuense from different parts.

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

[0098] Figure 3 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 rotation speed.

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

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

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

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

[0108] Figure 13 It is the result of the skin patch test. Specific implementation mode

[0109] In order to effectively develop and utilize the plant resource of Rhododendron dawuense, it is particularly crucial to accurately screen out the raw material parts of Rhododendron dawuense with high volatile component content. During the R & D process of this invention, it was confirmed that there are significant differences in the essential oil components of Rhododendron dawuense obtained by different extraction processes.

[0110] In the preliminary experiment, the steam distillation method was used to extract essential oils from different parts of Rhododendron dawuense, such as flowers, leaves, buds, one-year-old branches, and perennial branches.

[0111] Raw materials: Fresh Rhododendron dawuense plants, collected from plants growing normally at an altitude of 4100 m in Daofu County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province, and their flower, leaf, bud, one-year-old branch, and perennial branch parts were collected respectively.

[0112] Reagents: Anhydrous ether and anhydrous sodium sulfate, from Dongguan Xunye Chemical Reagent Co., Ltd., both are of analytical grade.

[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] The different parts of the freshly collected Daofu Rhododendron were crushed separately, and 10.0000g of the crushed samples of each part were accurately weighed using an electronic balance. The weighed samples were placed in a volatile oil extractor, and several glass beads were added. Distilled water was added according to the material-liquid mass ratio of 1:6. The distillation device was connected and distillation was started. The distillation time was set to 6h. After the distillation was completed, the yield of essential oils from each part was recorded. The essential oils obtained by distillation were collected, dissolved with an appropriate amount of anhydrous ether, and then an appropriate amount of anhydrous sodium sulfate was added for water absorption. The treated essential oils were stored in a -20℃ refrigerator overnight.

[0115] The yield of essential oil from each part of Rhododendron daofuensis 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 It can be seen that the essential oil yields of different parts of Daofu Rhododendron show obvious differences. The buds have the highest essential oil yield, reaching 2.33%, which is probably because the buds are in the active stage of plant growth, with vigorous cell division and metabolic activities, and can accumulate a large amount of volatile components. The essential oil yields of leaves and annual branches are also relatively high, at 1.89% and 2.17%, respectively, indicating that they are high-quality raw material parts for extracting essential oils. The essential oil yield of flowers is relatively low, at 0.45%. The yield of perennial branches is the lowest, at 0.21%. The differences in the essential oil yields of different parts are closely related to their respective physiological functions, cell structures, and the distribution of chemical components. In practical applications, parts with high oil content 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, and the yield was 2.11%, which was not much different from the 2.05% by steam distillation. The chemical composition of the extracted essential oil sample S3 was analyzed, see Figure 2 The three components with higher mass fractions are: Δ-cadinene (17.03%), calendulin (13.68%), and sabinene (12.27%). The odor of S3 is quite different from that of the original plant of Daofu Rhododendron, and the aroma does not show pleasant characteristics. Therefore, further research on ultrasonic-assisted steam distillation was abandoned.

[0118] To make the objectives, 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 conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to 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 claimed present invention, but merely represents the selected embodiments of the present invention.

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

[0120] In this embodiment, the raw material: Rhododendron dawuense, is collected from plants growing normally at an altitude of 4,100 m in Daofu County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province. Select its leaves, buds, and one-year-old branches for standby. The mass ratio of the fresh samples is leaves: buds: one-year-old branches = 1:3:10.

[0121] Reagents: anhydrous ether, anhydrous sodium sulfate, absolute 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 of which are of analytical purity; butane, (purity > 99%), Puyang Hongtaiyang Materials Co., Ltd.

[0122] Instrumentation: WoXin JJ-2 type tissue homogenizer, Wuxi WoXin Instrument Manufacturing Co., Ltd.; AB-L analytical balance (accuracy 0.0001 g), Mettler-Toledo Instruments (Shanghai) Co., Ltd.; V-CBE-5L subcritical fluid extraction laboratory complete set of devices, Henan Subcritical Biotechnology Co., Ltd.; Agilent 8890-7000D triple quadrupole gas chromatography-mass spectrometry, Agilent Technologies, Inc., USA; BCD-215TD GA refrigerator, Qingdao Haier Co., Ltd.; VTAVKL 70-5 molecular distillation equipment, German Rida Co., Ltd.; vacuum drying oven DZF-6020, Shanghai Hengke Instruments Co., Ltd.; Abbe refractometer WYA-2D type 2WA-J number, Shanghai Xiaoguang Instruments Co., Ltd.; relative density bottle 250.0 mL, Beijing Tianlian Hexie Instruments Factory.

[0123] Example 1

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

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

[0126] Experimental method

[0127] Process flow: Raw material preparation → Place into the subcritical extraction device → Add butane as the extraction agent at a material-liquid mass ratio of 1:3 → Adjust the extraction pressure to 0.5 Mpa → The extraction temperature is 30 - 55 °C → The extraction time is 20 - 45 min → Extract 3 times in a cycle → Obtain Rhododendron dawoense extract (extract rate 5.33%) → Transfer to the molecular distillation device → Set the vacuum degree to 0.01 - 0.1 mbar → Set the rotation speed to 150 - 250 r / min → Obtain Rhododendron dawoense oil.

[0128] Response surface experimental design: According to the results of the previous single-factor experiments, with the yield of Rhododendron dawoense oil as the response value, four factors that have a greater impact on the yield of Rhododendron dawoense oil were selected as experimental factors, namely: A - extraction temperature (°C), B - extraction time (min), C - vacuum degree (mbar), D - rotation speed (r / min). The Box-Behnken experimental design method was used to conduct a three-level experimental design for the four factors. The level coding and actual values of each factor are shown in Table 1:

[0129] Table 1 Factor level table

[0130]

[0131]

[0132] Calculation formula for oil yield

[0133] The yield of Rhododendron dawoense oil (yield) = mass of Rhododendron dawoense oil / mass of raw material × 100%

[0134] Results of response surface experiment

[0135] Through the Box-Behnken model design experiment with four factors and three levels, the software designed a total of 27 groups of experiments, calculated various regression coefficients, and established a mathematical regression model of the essential oil yield of Rhododendron dawoense with four factors: extraction temperature, extraction time, vacuum degree, and rotation speed using these regression coefficients. Multiple regression analysis was performed on the experimental data, and a quadratic polynomial regression model with the essential oil yield (%) as the dependent variable and the coded values of each factor as the independent variables was established. 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. By analyzing the function, A = 45.0755, B = 35.2775, C = 0.0597, and D = 193.981 were obtained. At this time, the essential oil yield of Rhododendron dawoense was the largest, with a maximum value of 2.91%, that is, the optimal preparation process conditions were an extraction temperature of 45.0755 °C, an extraction time of 35.2775 min, a vacuum degree of 0.0597 mbar, and a rotation speed of 193.981 r / min. After experimental verification, the essential oil of Rhododendron dawoense prepared under these conditions was 2.93%, which was close to the theoretical value.

[0136] Analysis of variance was performed on the regression models respectively. The results showed that the models were all extremely significant (P < 0.01), and the lack-of-fit term was not significant (P > 0.05), indicating that the models could fit the experimental data well and could be used for the prediction and analysis of the response values. By comparing the F values of the extraction temperature, extraction time, vacuum degree, and rotation speed, it can also be seen that the influence of the rotation speed was the greatest, followed by the vacuum degree, extraction time, and extraction temperature.

[0137] By drawing response surface plots and contour plots, the interactive effects of various factors on the essential oil yield were visually analyzed. It can be seen from the response surface plots and contour plots that the interactive effects of these factors had a greater impact on the essential oil yield of Rhododendron dawoense. Figure 3 are the response surface and contour plot of the interactive effect of extraction temperature and extraction time, Figure 4 are the response surface and contour plot of the interactive effect of extraction temperature and vacuum degree, Figure 5 are the response surface and contour plot of the interactive effect of extraction temperature and rotation speed, Figure 6 are the response surface and contour plot of the interactive effect of extraction time and vacuum degree, Figure 7 are the response surface and contour plot of the interactive effect of extraction time and rotation speed, Figure 8 are the response surface and contour plot of the interactive effect of vacuum degree and rotation speed. It can be seen from Figures 3 - 8 that their effects are all 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 Rhododendron dawoense oil using the optimized method described in the examples. To further illustrate the technical effects of the present invention, this example also compares the effects of extracting Rhododendron dawoense oil by the traditional steam distillation method and the subcritical extraction-molecular distillation refining method of the present invention.

[0140] Process flow

[0141] Steam distillation method: Raw material preparation → Place into a steam distiller → Add water at a material-liquid mass ratio of 1:6 → Heat to about 100 °C and start distillation → Distill for 6 h → Collect the distillation product → Add anhydrous sodium sulfate for drying → Obtain Rhododendron dawoense oil S1.

[0142] Subcritical extraction-molecular distillation refining method: Raw material preparation → Place into a subcritical extraction device → Add butane as an extraction agent at a material-liquid mass ratio of 1:3 → Adjust the extraction pressure to 0.5 Mpa → Extraction temperature is 45 °C → Extraction time is 35 min → Extract cyclically 3 times → Obtain Rhododendron dawoense extract (extract yield 5.33%) → Transfer to a molecular distillation device → Set the vacuum degree to 0.06 mbar → Set the rotation speed to 193 r / min → Obtain Rhododendron dawoense 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 injection; Control mode: Constant flow rate of 1 mL / min; Septum purge flow rate: 3 mL / min; Ion source temperature: 230 °C; Interface temperature: 280 °C; Acquisition mode: SCAN mass scan range m / z: 20 - 480 amu. Qualitative analysis of each volatile component is carried out using the NIST17 standard spectral library. All samples are detected under the same conditions, and the test solution is injected in parallel 3 times, and information such as the total ion chromatogram of the sample's GC-MS is recorded.

[0145] Yield of Rhododendron dawoense oil

[0146] The yield of Rhododendron dawoense oil by the steam distillation method is 2.05% ± 0.03%, and the yield by the subcritical extraction-molecular distillation refining method is 2.93% ± 0.05%. The yield of Rhododendron dawoense oil prepared by the subcritical extraction-molecular distillation refining method is 42.9% higher than that of the steam distillation method.

[0147] The essential oils of Rhododendron dawuense S1 prepared by steam distillation and Rhododendron dawuense S2 refined by subcritical extraction-molecular distillation were analyzed by GC-MS method respectively, and their total ion chromatograms are as Figure 9 , Figure 10 shown.

[0148] When retrieving the common peak standard spectral library, components with a matching degree > 85% and a content ≥ 1% were selected, and then the relative mass fraction of the components was calculated by the peak area normalization method. NIST spectral library retrieval plus manual parsing were used, and the component analysis results are shown in Table 2 and Table 3.

[0149] As can be seen from Table 2 and Table 3, a total of 44 components were detected in the essential oils of Rhododendron dawuense prepared by 2 different methods. Among them, 25 components were detected in the essential oil (S1) obtained by steam distillation as shown in Table 2, and 24 components were detected in the essential oil (S2) refined by subcritical extraction-molecular distillation as shown in Table 3. There are 5 common components in S1 and S2. The top 3 components with higher relative mass fractions in S1 are: 3-carene (23.21%), sabinene (22.82%), and calamenene (5.00%); the top 3 components with higher mass fractions in S2 are: calamenene (25.5%), elemol (9.87%), and Ginsenol (6.18%). The content of calamenene in S2 is more than 5 times that in S1.

[0150] Table 2 Component analysis table of essential oil S1 obtained by steam distillation method

[0151]

[0152]

[0153] Table 3 Component analysis table of essential oil S2 obtained by subcritical extraction-molecular distillation refining method

[0154]

[0155]

[0156] The component stacking diagrams of each sample are shown in Figure 11 : The essential oils of Rhododendron dawuense obtained by 2 methods are all composed of components such as alkenes, esters, alcohols, ketones, alkanes, etc., but the component contents of the 2 essential oils are different. S1 is the essential oil prepared by steam distillation method, in which the alkene content is the highest (62.82%). S2 is the essential oil prepared by subcritical extraction-molecular distillation refining method, in which the alcohol content is much higher than that of S1 (64.94%). The whole process temperature of the subcritical extraction-molecular distillation refining method is lower, and the essential oil of high-boiling components is better retained.

[0157] The essential oils of Rhododendron dawuense extracted by two methods differ significantly in yield and chemical composition. The yield of the essential oil obtained by the subcritical extraction-molecular distillation refining method is 2.93% ± 0.05%, which is significantly higher than 2.05% ± 0.03% of the steam distillation method. The alcohol content in the essential oil (S2) extracted by the subcritical extraction-molecular distillation refining method is much higher than that in the essential oil (S1) extracted by the steam distillation method. The former alcohol content reaches 64.94%, more than 3 times that of S1, and the content of acoranol is more than 5 times that of S1. The essential oil of high-boiling components mainly contains sesquiterpenoids, such as sesquiterpene, sesquiterpenol, etc. At present, it is considered that these molecules often have pharmacological effects in aspects such as antibacterial and antioxidant.

[0158] Detection of multiple indicators of the essential oils S1 and S2 of Rhododendron dawuense at 0 day and 90 days

[0159] Determination of refractive index

[0160] Drop the essential oil onto the surface of the refraction prism, cover the light inlet prism and lock the handwheel. Open the light-shielding plate and adjust the eyepiece. When a clear crosshair appears, rotate the handwheel so that the bright-dark dividing line has no color. Then continue to finely adjust the handwheel to make the dividing line coincide with the center of the crosshair, and then adjust the condenser. At this time, the indicated value read is the refractive index of the essential oil at this oil temperature. If the measurement temperature is not 20 °C, it should be converted to the refractive index at 20 °C according to the formula n 20 = n t +(t - 20)×0.00035 (where n 20 is the refractive index of the essential oil at 20 °C; n t is the refractive index of the essential oil at the oil temperature of t °C; t is the oil temperature during measurement, in °C; 0.00035 is the correction coefficient when the oil temperature is 20 °C).

[0161] S1 increased from 1.4633 at 0 day to 1.5257 at 90 days, and S2 changed from 1.4908 to 1.5004. The change range of S1 is large, indicating that its components changed significantly during storage, and S2 is more stable.

[0162] Identification of odor

[0163] It was identified by 5 sensory evaluation personnel respectively. Take an appropriate amount of the essential oil sample in a 50 mL beaker, heat it to 50 °C, stir and smell the odor. If it has the inherent odor of the essential oil and no peculiar smell, it is qualified, and the peculiar smell situation is noted for the unqualified ones.

[0164] The initial odor of S1 is quite different from that of the original plant, the odor is unpleasant, and it has a strong sour taste at 90 days; S2 is close to the aroma of the original plant at both 0 day and 90 days. It shows that S2 is much better than S1 in maintaining the odor.

[0165] Determination of specific gravity

[0166] Measure the masses of equal volumes of the essential oil sample and distilled water at 20 °C using the same relative density bottle. The ratio of the two masses is the specific gravity of the sample at this temperature.

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

[0168] Determination of acid value

[0169] Accurately weigh 1.0000 - 5.000 g of the sample into a 100 mL Erlenmeyer flask, and conduct a blank test simultaneously. Add 50 mL of ethanol - ether mixed solution (1:1) to each of the two Erlenmeyer flasks containing the sample and the 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, which is the titration end point. Record the volume of 0.1 mol / L potassium hydroxide used.

[0170] The acid value calculation formula is: AV = c × (V 1 - V 0 ) × 56.1 / m.

[0171] Where:

[0172] AV represents the acid value of the oil;

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

[0174] V 0 is the volume of the potassium hydroxide standard solution consumed in the blank test, mL;

[0175] V 1 is the volume of the 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, resulting in an increase in acidic substances. 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 - 3.0000 g of the sample and place it in a 250 mL iodine flask. Add 30 mL of a mixed solution of chloroform and glacial acetic acid (1:1) to the iodine flask to dissolve the sample. After adding 1 mL of saturated potassium iodide solution, tightly close the flask stopper, gently shake for 30 seconds, and then place it in the dark for 3 minutes. Take out the iodine flask, add 100 mL of water and shake well. Immediately titrate with a standard sodium thiosulfate solution. When the solution turns yellow, add 1 mL of starch indicator and continue titrating until the blue color disappears, which is the titration end point. Record the volume of the standard sodium thiosulfate solution consumed, and at the same time, conduct a blank test.

[0181] Peroxide value: For S1, it rises from 0.08 mmol / kg to 0.25 mmol / kg, and for S2, it rises from 0.03 mmol / kg to 0.12 mmol / kg, both indicating that an oxidation reaction has occurred, and the degree of oxidation of S1 is more severe.

[0182] Calculation formula for the peroxide value of oil and fat: P = c×(V 1 -V 0 )×1000 / 2m.

[0183] In the formula:

[0184] P is the peroxide value of the oil and fat;

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

[0186] V 0 is the volume of the standard sodium thiosulfate solution consumed in the blank test, mL;

[0187] V 1 is the volume of the standard sodium thiosulfate solution consumed by the sample, mL;

[0188] m is the sample mass, g.

[0189] Determination of saponification value (calculated as KOH)

[0190] GB / T5534 - 2008

[0191] Saponification value: For S1, it is 0, and for S2, it drops from 15 mg / g to 10 mg / g, indicating a decrease in saponifiable components in S2, and components such as esters may have changed. It is indicated that S1 does not contain fatty acids.

[0192] Determination of iodine value

[0193] GB / T5532 - 2022

[0194] Iodine value: For S1, it is 0, indicating that it contains no or extremely low levels of unsaturated fatty acids. For S2, it drops from 145 g / 100 g to 141 g / 100 g, indicating that unsaturated bonds may have reacted during storage.

[0195] Determination of fatty acids

[0196] GB 5009.168 - 2016 (Third method)

[0197] In terms of fatty acid composition, S1 contains no fatty acids. S2 has various fatty acid data at both 0 day and 90 days, and the contents of most fatty acids change little, but individual fatty acids such as stearic acid C18:0 and palmitoleic acid C16:1 show obvious changes. This indicates that the fatty acid composition of S2 is relatively stable during storage.

[0198] During the storage process, the stability of the subcritical extraction - molecular distillation refined Rhododendron tatsienense oil (S2) in terms of physical properties, chemical properties, and fatty acid composition is overall better than that of the oil (S1) prepared by steam distillation. This may be because different preparation methods lead to differences in the components and structures of the essential oils, affecting their stability during storage. It may also be that fatty acids play a certain stabilizing role or act synergistically with other components, making the stability of S2 better than that of S1. The fact that S1 has no fatty acids may make its application scenarios different from those of S2. In some applications with specific requirements or restrictions on fatty acids, S1 may have unique uses; while S2, due to containing various fatty acids and with the content of unsaturated fatty acids being over 70%, may have more advantages in fields such as skin care that require fatty acids. The smell of S2 has the fresh characteristics unique to Rhododendron tatsienense, which can stimulate a pleasant olfactory response and create a pleasant home atmosphere, and can play an important role in fragrances and home care.

[0199] The above characteristics of Rhododendron tatsienense essential oil indicate that it can be applied in antioxidant skin care products, antibacterial cosmetics, fragrance products, and stable cosmetic matrices.

[0200] Example 3

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

[0202] The addition amount of the essential oil in the skin care product is 2%.

[0203] One of the main inducements of skin aging is the invasion of reactive oxygen species. Excessive reactive oxygen species will not only damage the cell tissues of the human body, but also combine with proteins and lipids in the skin to generate oxides, ultimately leading to skin aging. Substances with antioxidant activity can react with DPPH free radicals, making their single electrons pair and lose activity, resulting in the fading of the solution color and the decrease of absorbance. The higher the DPPH scavenging rate, the stronger the antioxidant ability of the substance, and it can more effectively reduce or eliminate DPPH free radicals.

[0204] The reference standard for the antioxidant experiment method is 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, keep it away from light at room temperature for 30 min, measure the absorbance at a wavelength of 517 nm, and record the absorbance value as A1. The absorbance value of adding only 3 mL of anhydrous ethanol solution and 1 mL of the test sample solution in the cuvette is recorded as A2, and the absorbance value of adding 3 mL of DPPH-anhydrous ethanol solution and 1 mL of anhydrous ethanol solution in the cuvette is recorded as A3.

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

[0206] The experimental results are shown in Table 4. The DPPH radicals of S2 in the table are significantly higher than those of S1, indicating that S2 has stronger antioxidant activity.

[0207] Table 4 DPPH radical scavenging rates of two kinds of Rhododendron dawuense essential oil samples

[0208]

[0209]

[0210] Example 4

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

[0212] The cosmetic is used to inhibit Staphylococcus aureus or Pseudomonas aeruginosa, and the addition amount of the essential oil is 5%.

[0213] In this example,

[0214] Microbial test materials: strains such as Staphylococcus aureus, Escherichia coli, Candida albicans, Pseudomonas aeruginosa, etc., all from the China General Microbiological Culture Collection Center. Nutrient agar medium, nutrient broth medium, Sabouraud dextrose liquid medium, Sabouraud dextrose agar medium, blank drug sensitivity test paper, all purchased from Changde Bickman Biotechnology Co., Ltd.

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

[0216] Proliferation culture of strains: Use an inoculation loop to pick up the strains on the slant medium, inoculate them into the liquid medium, and then place them in a constant temperature shaker for culture. Bacteria are cultured at 37°C for 24 hours, and fungi are cultured at 28°C for 48 hours.

[0217] Antibacterial experiment by filter paper diffusion method: Soak the drug sensitivity test paper in the diluted essential oil; pipette 100 μL of the bacterial solution and spread it evenly on the solid medium. Then use forceps to pick up the drug sensitivity test paper and gently place it on the solid medium. Three parallel groups are placed in each medium, and a drug sensitivity test paper containing only normal saline is placed as a control; finally, place it in a constant temperature incubator for culture. Bacteria are cultured at 37°C for 24 hours, and fungi (Candida albicans) are cultured at 28°C for 48 hours.

[0218] The experimental results are as Figure 12 shown. Figure 12 In the figure, a is the antibacterial experimental result of S1 against Staphylococcus aureus, b is the antibacterial experimental result of S1 against Escherichia coli, c is the antibacterial experimental result of S1 against Pseudomonas aeruginosa, d is the antibacterial experimental result of S1 against Candida albicans; e is the antibacterial experimental result of S2 against Staphylococcus aureus, f is the antibacterial experimental result of S2 against Escherichia coli, g is the antibacterial experimental result of S2 against Pseudomonas aeruginosa, h is the antibacterial experimental result of S2 against Candida albicans. In the figure, the test papers at positions 1, 2, and 3 are three parallel test groups soaked in the essential oil, and position 4 is the drug sensitivity test paper containing only normal saline as a control. As Figure 12 can be seen, in terms of antibacterial performance, S1 and S2 have different characteristics. S1 has an obvious inhibitory effect on the Gram-positive bacterium Staphylococcus aureus and also has 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 has 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 their antibacterial spectra may be due to different components. The main component of S1 is terpene compounds, and the main component of S2 is sesquiterpene alcohol. Adding Rhododendron dawoense essential oil to cosmetics can improve the antibacterial performance of the product and reduce the need for additional preservatives.

[0220] Safety test:

[0221] Randomly select 9 volunteers for a patch test. The test method refers to the human skin patch test in the "2015 Cosmetics Safety and Technology Specifications". Cut the cotton pad into a size of 1.00 cm × 1.00 cm, soak it in Rhododendron dawoense essential oil. After the cotton pad fully absorbs the essential oil, apply it to the inner side of the volunteer's arm for 30 minutes. Continuously observe whether there are obvious redness, allergies and other phenomena on the volunteer's skin before and after the application.

[0222] The results of the skin patch test are shown in Figure 13 : After applying the two kinds of Rhododendron dawoense essential oils to the inner sides of the arms of 9 volunteers for 30 minutes respectively, slight redness and swelling occurred at the skin sites of 2 volunteers (No. 1 and No. 6) where S1 was applied, and no redness and swelling occurred at the skin sites of all volunteers where S2 was applied. This indicates that S1 has strong skin irritation, while S2 has no skin irritation and good safety.

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

[0224] In the description of the present invention, it should be understood that "-" and "~" represent the range between two numerical values, and this range includes the endpoints. For example, "A - B" represents the range greater than or equal to A and less than or equal to B. "A ~ B" represents the 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" herein is merely a correlative relationship describing the related objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone.

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

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

[0228] The above are only the preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limitations on the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. For those of ordinary skill in the art in this technical field, without departing from the spirit and scope of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as within the protection scope 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 smilax glabra alcohol 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.

2. The Daofu Rhododendron essential oil according to claim 1, characterized in that The essential oil comprises the following components and their mass percentages: Acorus alcohol: 24.23%~26.78%, Elemiol: 9.38%~10.36%, Ginsenol: 5.87% ~ 6.49%, Guaiol: 5.57% to 6.15%, Isoguaiacol: 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-serinene: 2.82% ~ 3.12%, Ethyl acetate: 2.78% to 3.08%, β-elemene: 2.77% to 3.07%, Isocalamusdiol: 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% to 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, characterized in that The essential oil comprises the following components and their mass percentages: Acorus alcohol: 25.5%, Elemiol: 9.87%, Ginsenol: 6.18%, Guaiol: 5.86%, Isoguaiacol: 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-serinene: 2.97%, Ethyl acetate: 2.93%, β-elemene: 2.92%, Isocalamdiol: 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-4-terpenoid: 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 dafuensis and crush them into particles ≤ 2 mm; (2) Subcritical extraction: The crushed raw material was mixed with butane at a feed-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, wherein A is temperature (35-55°C), B is time (25-45min), C is vacuum degree (0.01-0.1mbar), and D is rotation speed (150-250r / min).

6. The method according to claim 4, characterized in that The vacuum degree 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. The 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 added amount of the essential oil in 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. The use of the Daofu azalea 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. The use of the Daofu Rhododendron essential oil according to any one of claims 1 to 3 in the preparation of 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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