A method for preparing hypoallergenic agarwood essential oil and its application

Abstract

This invention belongs to the field of essential oil preparation technology, specifically relating to a method for preparing hypoallergenic agarwood essential oil and its application. The method involves desensitizing the raw agarwood essential oil obtained by supercritical carbon dioxide extraction. The desensitization process involves heating at low temperature followed by dissolution with water to remove the sensitizing components. The agarwood essential oil prepared by this method can reduce skin sensitization and irritation while retaining the main active ingredients of the agarwood essential oil.

Description

[0001] Priority application

[0002] This application claims priority to Chinese Invention Patent Application No. [2025114069886], filed on September 28, 2025, entitled "A Method for Processing Agarwood Essential Oil", which is incorporated herein by reference in its entirety. Technical Field

[0003] This invention belongs to the field of essential oil preparation technology, specifically relating to a method for preparing hypoallergenic agarwood essential oil and its application. Background Technology

[0004] Agarwood essential oil is derived from plants of the genus Aquilaria (Aquilaria). Aquilaria Agarwood (spp.) is a natural plant essential oil extracted from resinous woods, possessing a unique aroma and rich bioactive components. Due to its calming, antibacterial, and anti-inflammatory properties, it helps relieve stress and regulate mood, and is widely used in high-end perfumes, cosmetics, aromatherapy, and traditional medicine. Furthermore, the rich and layered aroma of agarwood essential oil often makes it suitable for use as a fragrance or massage oil, offering a soothing effect on the mind and body. There are many methods for extracting agarwood essential oil, with the most common being traditional steam distillation and supercritical carbon dioxide fluid extraction.

[0005] Steam distillation is the most traditional and commonly used essential oil extraction technique. It is a mature process, simple to operate, and relatively inexpensive. The extracted essential oil typically has low skin irritation and allergenicity. However, this method requires high temperatures, which can easily damage the heat-sensitive aromatic components in agarwood, leading to aroma loss. Furthermore, the extraction rate using steam distillation is usually only 0.1% to 0.3%, which is low, and the process is time-consuming, limiting the utilization efficiency of agarwood resources and making it difficult to meet the needs of large-scale production.

[0006] In contrast, supercritical carbon dioxide fluid extraction, as a modern green extraction technology, can extract agarwood essential oil at lower temperatures, better preserving the heat-sensitive components and volatile aromatic substances in agarwood. The extraction rate is typically 1% to 3%, far exceeding that of steam distillation, resulting in an essential oil with a richer and more layered aroma. However, despite its high extraction rate and rich aroma, this method also extracts more impurities and increases the concentration of essential oil. This high concentration of essential oil mixed with other substances can cause significant skin irritation for some individuals, even leading to allergic reactions such as rashes and itching. Therefore, it poses a potential risk when used in high-end cosmetics and skincare products.

[0007] In conclusion, there is an urgent need to develop a new extraction method that can retain the high extraction rate and rich aroma of essential oils obtained by supercritical carbon dioxide fluid extraction, while effectively reducing their skin irritation. Furthermore, the extracted essential oil products should achieve a level of safety comparable to or similar to those extracted by steam distillation, thus meeting the market demand for high-quality, highly safe agarwood essential oil products. Summary of the Invention

[0008] The purpose of this invention is to overcome the drawbacks of existing supercritical carbon dioxide fluid extraction methods for agarwood essential oil, which result in strong irritation, and to provide a novel, efficient, and reliable method for purifying the essential oil. This method aims to remove or reduce irritating components in agarwood essential oil that cause skin discomfort, while maximizing the preservation of its original characteristic aroma components and bioactivity. This makes the processed essential oil comparable in safety to products obtained through steam distillation, thereby broadening its application areas. Specifically, the purpose of this invention is to provide a method for extracting and processing low-sensitivity, high-concentration agarwood essential oil, and the application of this low-sensitivity, high-concentration essential oil. The invention specifically adopts the following technical solution.

[0009] A method for preparing hypoallergenic agarwood essential oil involves desensitizing the raw agarwood essential oil by heating it at low temperature followed by dissolving and removing the allergens in water. The method specifically includes the following steps:

[0010] S01: Agarwood medicinal material was treated by supercritical carbon dioxide extraction to obtain the first agarwood essential oil sample;

[0011] S02: The first agarwood essential oil sample is placed in a sealed container and heated under low temperature conditions for no less than 24 hours; the low temperature conditions are set to no less than 50°C and no more than 100°C. After the heating treatment is completed, the second agarwood essential oil sample is obtained.

[0012] S03: Add water to the second agarwood essential oil sample and mix evenly. Then stir the mixture at low speed to dissolve (partial) components of the essential oil in the aqueous solution.

[0013] The volume ratio of essential oil to water is usually 1:5-10. Water, as a solvent, can help extract and remove some of the irritating components in essential oils.

[0014] S04: Allow the mixture to stand until it naturally separates into an oil phase and an aqueous phase; separate and collect the oil phase and dry it to obtain the desensitized agarwood essential oil.

[0015] Specifically, liquid-liquid separation is performed, utilizing the polarity difference between water and essential oils to effectively separate irritating components from the essential oils. After processing, the liquid is allowed to stand for a certain period of time to allow the essential oil phase and the aqueous phase to separate into layers. Then, the upper layer of agarwood essential oil is collected using a separatory funnel.

[0016] Furthermore, the low temperature condition is set to 50℃~70℃; the heating treatment time is set to 24-48h.

[0017] As a preferred embodiment, the low temperature condition is set to 60°C; and the heating treatment time is set to 48 hours.

[0018] Furthermore, the low-speed stirring speed is set to 200-300 rpm; the stirring time is set to 10-60 minutes.

[0019] The specified stirring speed ensures uniform mixing without causing damage to the agarwood essential oil due to over-stirring, while also facilitating effective contact between water and the essential oil.

[0020] As a preferred embodiment, the low-speed stirring speed is set to 300 rpm; the stirring time is set to 30 minutes.

[0021] Furthermore, the extraction temperature of the supercritical carbon dioxide extraction method is set to 50℃~60℃.

[0022] Furthermore, the standing time for the mixture should be no less than 100 minutes.

[0023] Furthermore, the method for drying and dehydrating the oil phase includes adding anhydrous sodium carbonate to the oil phase.

[0024] To remove residual water from the essential oil, the collected agarwood essential oil can be dehydrated by adding anhydrous sodium carbonate. This step ensures minimal water residue in the essential oil while preserving its purity and aroma. Through this series of steps, the final agarwood essential oil is highly pure with significantly reduced irritating components, making it suitable for use in cosmetics and skincare products.

[0025] This refined purification process effectively removes impurities and irritating components from agarwood essential oil while preserving its unique aroma and active ingredients, providing the high-end market with safer and higher-quality agarwood essential oil products.

[0026] The hypoallergenic agarwood essential oil prepared by the above method.

[0027] Application of hypoallergenic agarwood essential oil in the preparation of cosmetics, perfumes or topical skin preparations.

[0028] Beneficial technical effects:

[0029] This invention provides a method for preparing and extracting low-sensitivity, high-concentration agarwood essential oil. First, high-concentration raw agarwood essential oil is obtained by supercritical carbon dioxide fluid extraction. Then, desensitization treatment is performed to reduce its skin sensitization and irritation, while retaining the main active ingredients of agarwood essential oil.

[0030] (1) Significantly reduced irritation: Through heat treatment and water adsorption separation steps, this method can effectively remove irritating components from supercritical agarwood essential oil, reduce skin allergic reactions and irritation, and ensure the safety of the essential oil when in direct contact with the skin. The irritation of the treated essential oil is significantly reduced, making it suitable for high-end markets such as cosmetics and skin care products. Nude mouse skin irritation experiments have shown that its irritation rating can be reduced from "highly irritating" to "none or very slight irritation", reaching a safety level comparable to products produced by steam distillation.

[0031] (2) Preservation of active ingredients and aroma: The heating and water extraction steps in this method effectively preserve the main aroma components and bioactive components of agarwood essential oil through gentle treatment. After this purification process, the aroma of the essential oil is rich and long-lasting, and the main active ingredients are well preserved, ensuring the core quality and therapeutic effects of agarwood essential oil.

[0032] (3) Green and environmentally friendly, with no chemical additives: This purification method does not rely on harmful chemical reagents at all, and the water used is a green and environmentally friendly solvent, which meets the requirements of modern cosmetics and health products for natural and harmless raw materials. In addition, the gentle heating and low-speed stirring treatment during the purification process avoids extreme conditions such as excessive heating or the use of high pressure, further reducing the damage to essential oils.

[0033] (4) Efficient solvent extraction and separation: By using water and liquid-liquid partitioning technology, some components in the essential oil that may be irritating to the skin are effectively removed. Compared with traditional purification processes, this method is simple to operate, takes less time, and can be carried out at a lower temperature, avoiding the waste of resources in high-temperature steam or other high-energy extraction processes.

[0034] (5) Enhancing the market competitiveness of products: Purified agarwood essential oil has lower irritation and higher safety, and can be widely used in skin care, cosmetics, perfumes and other products, meeting the modern consumer demand for natural, safe and effective high-end products. This method helps to enhance the market competitiveness of agarwood essential oil and broaden its application areas. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0036] Figure 1 This is a comparison of GC-MS spectra of agarwood essential oil before and after treatment in one embodiment of the present invention (showing that the main peaks are consistent).

[0037] Figure 2 This is a comparative diagram of a nude mouse skin irritation experiment in one embodiment of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0039] In this document, "and / or" includes any and all combinations of one or more of the listed related items.

[0040] In this article, "multiple" means two or more, that is, it includes two, three, four, five, etc.

[0041] As used in this specification, the term "about" typically means + / -5% of the value, more typically + / -4% of the value, more typically + / -3% of the value, more typically + / -2% of the value, even more typically + / -1% of the value, and even more typically + / -0.5% of the value.

[0042] In this specification, certain embodiments may be disclosed in a range-bound format. It should be understood that this "range-bound" description is merely for convenience and brevity and should not be construed as a rigid limitation on the disclosed range. Therefore, the description of a range should be considered as having specifically disclosed all possible subranges and the individual numerical values ​​within those ranges. For example, a description of the range 1-6 should be considered as having specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and the individual numbers within those ranges, such as 1, 2, 3, 4, 5, and 6. This rule applies regardless of the breadth of the range.

[0043] Example 1

[0044] The same batch of agarwood raw materials were selected and divided into two batches. Agarwood essential oil was extracted using the conventional supercritical carbon dioxide fluid extraction method. The extraction temperature was set at 50℃. After separating the aqueous phase and the oil phase, sample 1 (referred to as supercritical 1) was obtained by supercritical extraction. The extraction temperature was set at 60℃. After separating the aqueous phase and the oil phase, sample 2 (referred to as supercritical 2) was obtained by supercritical extraction.

[0045] Two different batches of agarwood raw materials were selected and extracted using the conventional water distillation method: 1 kg of agarwood raw material was added to 10 kg of water at a material-to-liquid ratio of 1:10, and then heated to 100°C in a heating instrument. A reflux cooling device was connected, and the mixture was refluxed for 12 hours. Based on the different batches of agarwood raw materials, agarwood essential oil sample 1 (referred to as water distillation 1) and agarwood essential oil sample 2 (referred to as water distillation 2) extracted by water distillation were obtained for later use.

[0046] Example 2

[0047] Supercritical carbon dioxide fluid extraction (100 mL) obtained in Example 1 was transferred to a sealed container. The heating temperature was set to 50°C, and the mixture was heated for 24 hours under this constant temperature environment to remove irritating components from the agarwood essential oil. After heating, the agarwood essential oil was mixed with water at a volume ratio of 1:5-10. The mixture was shaken or agitated to ensure thorough mixing. The mixture was placed in a stirrer and stirred at low speed to promote uniform dispersion of the irritating components. After stirring for 10-20 minutes, the liquid was allowed to stand for 120 minutes to allow for natural separation into oil and water phases. The upper oil phase was separated using a separatory funnel, and the desensitized agarwood essential oil was collected. Anhydrous sodium carbonate was added to the collected desensitized agarwood essential oil to remove residual moisture. Desensitized agarwood essential oil A1 (abbreviated as Agarwood Essential Oil A1) was obtained.

[0048] Example 3

[0049] Supercritical carbon dioxide fluid extraction (100 mL) obtained in Example 1 was transferred to a sealed container. The heating temperature was set to 60°C, and the mixture was heated for 24 hours under this constant temperature environment to remove irritating components from the agarwood essential oil. After heating, the agarwood essential oil was mixed with water at a volume ratio of 1:5-10. The mixture was shaken or agitated to ensure thorough mixing. The mixture was then placed in a stirrer and stirred at low speed to promote uniform dispersion of the irritating components. After stirring for 10-20 minutes, the liquid was allowed to stand for 120 minutes to allow for natural separation into oil and water phases. The upper oil phase was separated using a separatory funnel, and the desensitized agarwood essential oil was collected. Anhydrous sodium carbonate was added to the collected desensitized agarwood essential oil to remove residual moisture. Desensitized agarwood essential oil A2 (abbreviated as Agarwood Essential Oil A2) was obtained.

[0050] Example 4

[0051] Supercritical carbon dioxide fluid extraction (100 mL) obtained in Example 1 was transferred to a sealed container. The heating temperature was set to 70°C, and the mixture was heated for 24 hours under this constant temperature environment to remove irritating components from the agarwood essential oil. After heating, the agarwood essential oil was mixed with water at a volume ratio of 1:5-10. The mixture was shaken or agitated to ensure thorough mixing. The mixture was placed in a stirrer and stirred at low speed to promote uniform dispersion of the irritating components. After stirring for 10-20 minutes, the liquid was allowed to stand for 120 minutes to allow for natural separation into oil and water phases. The upper oil phase was separated using a separatory funnel, and the desensitized agarwood essential oil was collected. Anhydrous sodium carbonate was added to the collected desensitized agarwood essential oil to remove residual moisture. Desensitized agarwood essential oil A3 (abbreviated as Agarwood Essential Oil A3) was obtained.

[0052] Example 5

[0053] Supercritical carbon dioxide fluid extraction (100 mL) obtained in Example 1 was transferred to a sealed container. The heating temperature was set to 60°C, and the mixture was heated for 48 hours under this constant temperature environment to remove irritating components from the agarwood essential oil. After heating, the agarwood essential oil was mixed with water at a volume ratio of 1:5-10. The mixture was shaken or agitated to ensure thorough mixing. The mixture was placed in a stirrer and stirred at low speed to promote uniform dispersion of the irritating components. After stirring for 10-20 minutes, the liquid was allowed to stand for 120 minutes to allow for natural separation into oil and water phases. The upper oil phase was separated using a separatory funnel, and the desensitized agarwood essential oil was collected. Anhydrous sodium carbonate was added to the collected desensitized agarwood essential oil to remove residual moisture. Desensitized agarwood essential oil A4 (abbreviated as Agarwood Essential Oil A4) was obtained.

[0054] Example 6

[0055] Testing and effect verification.

[0056] (1) GC-MS analysis: GC-MS analysis was performed on the essential oils before and after treatment. Figure 1 The results showed that the characteristic chromatographic peaks of agarwood essential oil (A1-A4) after desensitization treatment were highly consistent with those of agarwood essential oil extracted by supercritical carbon dioxide fluid extraction alone, proving that the desensitization process proposed in this invention preserved the effective components of the essential oil.

[0057] (2) Skin irritation test: The acute skin irritation test method in the Cosmetic Safety Technical Specification was used to test adult nude mice. Figure 2The results showed that the supercritical fluid extraction group exhibited significant erythema and edema, indicating that the essential oils extracted by supercritical fluid extraction had a higher concentration. In contrast, the essential oils extracted by steam distillation had a lower concentration and were less likely to irritate the skin of nude mice. The desensitized essential oil group showed similar effects to the steam-distilled essential oil group, with no visible erythema or edema observed, demonstrating that the safety of the essential oils was significantly improved after desensitization.

[0058] (3) The four treated essential oils (A1-A4) were compared with those from supercritical 1. After removing the dissolving solvent and instrument interference, a total of 143 volatile components were identified. Among them, 79 volatile components showed a trend of relative decrease in content in all four treated essential oils. Due to the low original content of the components and the instrument detection limit, a total of 24 substances were not detected after treatment, including alpha-Guaiene, Humulene, Valerena-4,7(11)-diene, etc. In the supercritical agarwood essential oil crude oil, due to the high concentration of a large number of substances, some experimental animals experienced skin allergies. The concentration of the treated essential oil was diluted. The analysis revealed that A4 essential oils retained more volatile components compared to A1, A2, and A3. A4 contains 20 volatile components, including Kessane, trans-Chrysanthenol, Longifolene, and Supraene, with their relative percentage content showing an increasing trend. In all processed agarwood essential oils, several unique agarwood substances were retained. Agarospirol accounted for 0.25%, 0.18%, 0.20%, and 0.22% of the agarwood essential oils in the A1 to A4 treatments, respectively; 2-(2-phenylethyl)chromone accounted for 41.22%, 37.42%, 34.54%, and 31.39%; 2-(2'-Methoxyphenethyl)chromone accounted for 0.50%, 0.73%, 0.51%, and 0.91%; and 2-(4-Methoxyphenethyl)-4H-chromen-4-one accounted for 15.97%, 19.10%, 18.17%, and 19.17%. The results are shown in Table 1.

[0059] Linalool and eugenol in supercritical agarwood essential oil are prone to causing skin allergies. The mechanism by which linalool causes skin allergies is mainly related to its oxidation reaction on the skin. Eugenol causes skin allergies because it is easily oxidized and activated on the skin surface by air and skin peroxidases, generating highly electrophilic intermediates. These reactive metabolites can covalently bind to the thiol amino groups of skin proteins such as keratin, be taken up and presented by dendritic cells, thereby initiating a specific T-cell response and inducing allergic contact dermatitis. At the same time, air oxidation and free radical processes also produce secondary products such as peroxides, further enhancing the sensitizing potential. Based on a large amount of clinical and mechanistic evidence, the European Union has recognized eugenol as a fragrance allergen and included it in the allergen labeling list in Annex III of the Cosmetic Regulations.

[0060] This invention utilizes prolonged, low-to-medium temperature heating under sealed conditions to transform linalool in a relatively gentle manner, while preserving the aromatic substances and active ingredients of agarwood essential oil. Linalool may initially oxidize, leading to a gradual decrease in its concentration and the formation of small amounts of peroxides, aldehydes, and ketones, which are soluble in subsequently added water and removed. Simultaneously, with prolonged heating, linalool may also undergo dehydration and skeletal rearrangement, generating non-irritating or mildly irritating cyclic compounds such as α-terpineol, and enriching the aroma of the essential oil.

[0061] Table 1-1 Comparison of volatile components of agarwood essential oil before and after treatment

[0062]

[0063] Table 1-2 Comparison of volatile components of agarwood essential oil before and after treatment

[0064]

[0065] Table 1-3 Comparison of volatile components of agarwood essential oil before and after treatment

[0066]

[0067] Table 1-4 Comparison of volatile components of agarwood essential oil before and after treatment

[0068]

[0069] Table 1-5 Comparison of volatile components of agarwood essential oil before and after treatment

[0070]

[0071] Table 1-6 Comparison of volatile components of agarwood essential oil before and after treatment

[0072]

[0073] Table 1-7 Comparison of volatile components of agarwood essential oil before and after treatment

[0074]

[0075] Table 1-8 Comparison of volatile components of agarwood essential oil before and after treatment

[0076]

[0077] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method of preparing a hypoallergenic linaloe oil, characterized by, The raw agarwood essential oil is desensitized by heating at low temperature followed by dissolving and removing it with water. The specific steps include: S01: Agarwood medicinal material was treated by supercritical carbon dioxide extraction, and the extraction temperature of the supercritical carbon dioxide extraction method was set to 50℃~60℃ to obtain the first agarwood essential oil sample. S02: The first agarwood essential oil sample is placed in a sealed container and heated under low temperature conditions for 24-48 hours; the low temperature conditions are set to 50℃~70℃, and the second agarwood essential oil sample is obtained after the heating treatment is completed. S03: Add water to the second agarwood essential oil sample and mix evenly. Then stir the mixture at low speed to dissolve the components in the essential oil in the aqueous solution. S04: Allow the mixture to stand until it naturally separates into an oil phase and an aqueous phase; the time for standing the mixture is not less than 100 minutes; separate and collect the oil phase and dry it to remove water. The method for drying and dehydrating the oil phase is to add anhydrous sodium carbonate to the oil phase to obtain the hypoallergenic agarwood essential oil.

2. The method of claim 1, wherein, The low temperature condition was set to 60°C; the heating treatment time was set to 48 hours.

3. The method of claim 1, wherein, The low-speed stirring speed is set to 200-300 rpm; the stirring time is set to 10-60 minutes.

4. The method of claim 3, wherein, The low-speed stirring speed is set to 300 rpm; the stirring time is set to 30 minutes.

5. The hypoallergenic agarwood essential oil prepared by the method according to any one of claims 1-4.

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