Method for synchronous preparation of bamboo leaf terpenoids and essential oil

Abstract

The application discloses a method for synchronously preparing terpenes and essential oil of Indocalamus leaves, which simultaneously obtains crude terpenes and crude essential oil of Indocalamus leaves by adopting supercritical carbon dioxide extraction and adsorption column adsorption. The Indocalamus leaves are used as raw materials, and the raw materials are washed, dried, and crushed. The crushed raw materials are added into a supercritical carbon dioxide extraction kettle, and cyclic extraction is carried out under the conditions of an extraction pressure of 30 MPa, a temperature of 40 DEG C, and a separation pressure of 8 MPa for 4.5 hours. After the extraction is completed, the pressure of the separation kettle is reduced to 2 MPa, a buffer tank is connected to the outlet of the separation kettle, liquid samples are collected in the buffer tank, crude terpenes of Indocalamus leaves are obtained, and gaseous samples flow through an adsorption column after passing through the buffer tank, and essential oil components are collected. The adsorption column is eluted with anhydrous ethanol, and an essential oil alcohol solution of Indocalamus leaves is obtained. Alternatively, the essential oil of Indocalamus leaves is collected in a liquid nitrogen cold trap by using a temperature-programmed desorption condensation method, and is desorbed at a rate of 10 DEG C / s to 280 DEG C.

Description

Technical Field

[0001] This invention relates to a method for supercritical carbon dioxide extraction of terpenoids and plant essential oils from bamboo leaves. Background Technology

[0002] *Inula japonica*, a species of bamboo belonging to the genus *Inula* of the Poaceae family, is a scattered bamboo species with large, oval leaves. These leaves are commonly used as packaging material for zongzi (sticky rice dumplings) or other foods, as well as as a raw material for tea and wine, animal feed, and as linings for hats and boat awnings. Its use in China dates back over 2000 years. Besides being edible, *Inula japonica* leaves are also a traditional Chinese medicine with properties of clearing heat, stopping bleeding, detoxifying, and reducing swelling. Modern research shows that *Inula japonica* leaves contain various active ingredients, including polyphenols, coketones, and essential oils, which possess immune-enhancing, anti-aging, and anti-tumor activities. Terpenoids, composed of two or more isoprene units, are also important active ingredients in *Inula japonica* leaves and have antioxidant, antibacterial, anti-inflammatory, and neuroprotective functions, and are widely used in food and cosmetics.

[0003] Supercritical carbon dioxide extraction is a commonly used green extraction technology that has been widely applied in the food, pharmaceutical, and petroleum industries, especially in the extraction of high-value-added active ingredients. While supercritical carbon dioxide extraction is highly efficient for extracting low-polarity active ingredients, it is less efficient for extracting polar, small-molecule essential oils. During the supercritical carbon dioxide preparation process, volatile essential oils often escape into the air with the carbon dioxide during the separation stage, making them difficult to collect. Therefore, the use of supercritical carbon dioxide for preparing volatile essential oils is relatively rare in practical applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned shortcomings of the existing technology and provide a method for the simultaneous preparation of terpenoids and essential oils from *Imperata cylindrica* leaves. The method employs supercritical carbon dioxide extraction and adsorption column adsorption to simultaneously obtain crude extracts of terpenoids and essential oils from *Imperata cylindrica* leaves, representing a green and energy-saving production technology.

[0005] The technical solution adopted by this invention to solve the above problems is: a method for simultaneously preparing terpenoids and essential oils from bamboo leaves, characterized by comprising the following steps:

[0006] (1) Using bamboo leaves as raw material, wash and dry the raw material, and grind it into 10-20 mesh;

[0007] (2) The pulverized raw material was added to the supercritical carbon dioxide extraction vessel and extracted for 4.5 hours under the conditions of extraction pressure of 30 MPa, temperature of 40℃ and separation pressure of 8 MPa.

[0008] (3) After extraction, the pressure of the separation vessel is reduced to 2 MPa. The outlet of the separation vessel is connected to a buffer tank. The liquid sample is collected in the buffer tank to obtain crude extract of terpenoids from bamboo leaves. The gas sample flows through the buffer tank and then through the adsorption column to collect essential oil components.

[0009] (4) Elute the adsorption column in step (3) with 3 column volumes of anhydrous ethanol to obtain a bamboo leaf essential oil alcohol solution; or, desorb the adsorption column in step (3) by heating to 280°C at a rate of 10°C / second and collect the bamboo leaf essential oil in a liquid nitrogen cold trap.

[0010] Furthermore, in step (1), the raw material is freshly picked bamboo leaves with a moisture content of about 60%.

[0011] Furthermore, in step (3), the packing material of the adsorption column is a 2-3 mm particle adsorbent.

[0012] Furthermore, in step (3), the adsorption column packing material is a synthetic material composed of ionic liquid and covalent organic framework (IL@COF), and the synthesis steps are as follows:

[0013] 1) Weigh 60-200g of ionic liquid and 80-100g of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTA), add 2.0L of 1,4-dioxane and 2.0L of mesitylene, sonicate for 10min, then slowly add 1.0L of 3M acetic acid and sonicate for 10min.

[0014] 2) Disperse 100-120g of 1,3,5-tris(4-aminophenyl)benzene (TAPB) in 2.0L of 1,4-dioxane and 2.0L of mesitylene, then add the solution prepared in step 1), and shake at room temperature for 20 minutes.

[0015] 3) The solution obtained in step 2) was allowed to stand and filtered, and the yellow-brown precipitate was collected. It was washed three times with anhydrous methanol to remove impurities and made into 2-3 mm particles. The particles were placed in a vacuum drying oven at 60°C and a vacuum degree below -94 kPa for 12 hours to obtain the packing material.

[0016] Further, in step 1), the ionic liquid is 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium acetate, or 1-octyl-3-methylimidazolium bromide; preferably 1-ethyl-3-methylimidazolium hydrogen sulfate.

[0017] Preferably, in step 1), the amount of ionic liquid used is 90g; the amount of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde used is 93g.

[0018] Preferably, in step 2), the amount of 1,3,5-tris(4-aminophenyl)benzene used is 112g.

[0019] Compared with the prior art, the present invention has the following advantages and effects:

[0020] 1. It can simultaneously obtain terpenoid components and essential oil components from bamboo leaves, thus avoiding waste of resources.

[0021] 2. The adsorbent can be reused. After elution, the adsorbent can be vacuum dried at 60°C and reused. Alternatively, it can be reused directly by heating desorption.

[0022] 3. The filler material used is synthesized at room temperature, which is safe, effective, and has high adsorption efficiency.

[0023] 4. The essential oil has a high degree of reduction, avoiding the drawbacks of high-temperature or solvent extraction methods such as water extraction. Attached Figure Description

[0024] Figure 1 This is a comparison chart of the effects of the adsorbent of this invention with other adsorbents.

[0025] Figure 2 and Figure 3 This is an electron microscope image of the adsorbent of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The following embodiments are explanations of the present invention, but the present invention is not limited to the following embodiments.

[0027] Example 1.

[0028] In this embodiment, a method for simultaneously preparing terpenoids and essential oils from bamboo leaves includes the following steps:

[0029] (1) Using bamboo leaves as raw material, wash and dry the raw material, and grind it to 10 mesh;

[0030] (2) The pulverized raw material was added to the supercritical carbon dioxide extraction vessel and extracted for 4.5 hours under the conditions of extraction pressure of 30 MPa, temperature of 40℃ and separation pressure of 8 MPa.

[0031] (3) After extraction, the pressure of the separation vessel is reduced to 2 MPa. The outlet of the separation vessel is connected to a buffer tank. The liquid sample is collected in the buffer tank to obtain crude extract of terpenoids from bamboo leaves. The gas sample flows through the buffer tank and then through the adsorption column to collect essential oil components.

[0032] (4) Elute the adsorption column in step (3) with 3 column volumes of anhydrous ethanol to obtain a bamboo leaf essential oil alcohol solution; or, desorb the adsorption column in step (3) by heating to 280°C at a rate of 10°C / second and collect the bamboo leaf essential oil in a liquid nitrogen cold trap.

[0033] Specifically, in step (1), the raw material is freshly picked bamboo leaves with a moisture content of about 60%. In step (3), the adsorption column packing material is a 2-3 mm particle adsorbent, and the adsorption column packing material is a synthetic material composed of ionic liquid and covalent organic framework (IL@COF). The synthesis steps are as follows:

[0034] 1) Weigh 60g of ionic liquid and 80g of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTA), add 2.0L of 1,4-dioxane and 2.0L of mesitylene, sonicate for 10min, then slowly add 1.0L of 3M acetic acid and sonicate for 10min.

[0035] 2) Disperse 100g of 1,3,5-tris(4-aminophenyl)benzene (TAPB) in 2.0L of 1,4-dioxane and 2.0L of mesitylene, then add the solution prepared in step 1), and shake at room temperature for 20 minutes;

[0036] 3) The solution obtained in step 2) was allowed to stand and filtered, and the yellow-brown precipitate was collected. It was washed three times with anhydrous methanol to remove impurities and made into 2-3 mm particles. The particles were placed in a vacuum drying oven at 60°C and a vacuum degree below -94 kPa for 12 hours to obtain the packing material.

[0037] Specifically, in step 1), the ionic liquid is 1-octyl-3-methylimidazole bromide.

[0038] Example 2.

[0039] In this embodiment, a method for simultaneously preparing terpenoids and essential oils from bamboo leaves includes the following steps:

[0040] (1) Using bamboo leaves as raw material, wash and dry the raw material, and grind it to 20 mesh;

[0041] (2) The pulverized raw material was added to the supercritical carbon dioxide extraction vessel and extracted for 4.5 hours under the conditions of extraction pressure of 30 MPa, temperature of 40℃ and separation pressure of 8 MPa.

[0042] (3) After extraction, the pressure of the separation vessel is reduced to 2 MPa. The outlet of the separation vessel is connected to a buffer tank. The liquid sample is collected in the buffer tank to obtain crude extract of terpenoids from bamboo leaves. The gas sample flows through the buffer tank and then through the adsorption column to collect essential oil components.

[0043] (4) Elute the adsorption column in step (3) with 3 column volumes of anhydrous ethanol to obtain a bamboo leaf essential oil alcohol solution; or, desorb the adsorption column in step (3) by heating to 280°C at a rate of 10°C / second and collect the bamboo leaf essential oil in a liquid nitrogen cold trap.

[0044] Specifically, in step (1), the raw material is freshly picked bamboo leaves. In step (3), the adsorption column packing material is a 2-3 mm particle adsorbent, and the adsorption column packing material is a synthetic material composed of ionic liquid and covalent organic framework (IL@COF). The synthesis steps are as follows:

[0045] 1) Weigh 200g of ionic liquid and 100g of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTA), add 2.0L of 1,4-dioxane and 2.0L of mesitylene, sonicate for 10min, then slowly add 1.0L of 3M acetic acid, and sonicate for 10min.

[0046] 2) Disperse 120g of 1,3,5-tris(4-aminophenyl)benzene (TAPB) in 2.0L of 1,4-dioxane and 2.0L of mesitylene, then add the solution prepared in step 1), and react with shaking at room temperature for 20 minutes;

[0047] 3) The solution obtained in step 2) was allowed to stand and filtered, and the yellow-brown precipitate was collected. It was washed three times with anhydrous methanol to remove impurities and made into 2-3 mm particles. The particles were placed in a vacuum drying oven at 60°C and a vacuum degree below -94 kPa for 12 hours to obtain the packing material.

[0048] Specifically, in step 1), the ionic liquid is 1-ethyl-3-methylimidazolium acetate.

[0049] Example 3.

[0050] In this embodiment, a method for simultaneously preparing terpenoids and essential oils from bamboo leaves includes the following steps:

[0051] (1) Using bamboo leaves as raw material, wash and dry the raw material, and grind it to 15 mesh;

[0052] (2) The pulverized raw material was added to the supercritical carbon dioxide extraction vessel and extracted for 4.5 hours under the conditions of extraction pressure of 30 MPa, temperature of 40℃ and separation pressure of 8 MPa.

[0053] (3) After extraction, the pressure of the separation vessel is reduced to 2 MPa. The outlet of the separation vessel is connected to a buffer tank. The liquid sample is collected in the buffer tank to obtain crude extract of terpenoids from bamboo leaves. The gas sample flows through the buffer tank and then through the adsorption column to collect essential oil components.

[0054] (4) Elute the adsorption column in step (3) with 3 column volumes of anhydrous ethanol to obtain a bamboo leaf essential oil alcohol solution; or, desorb the adsorption column in step (3) by heating to 280°C at a rate of 10°C / second and collect the bamboo leaf essential oil in a liquid nitrogen cold trap.

[0055] Specifically, in step (1), the raw material is freshly picked bamboo leaves with a moisture content of about 60%. In step (3), the adsorption column packing material is a 2-3 mm particle adsorbent, and the adsorption column packing material is a synthetic material composed of ionic liquid and covalent organic framework (IL@COF). The synthesis steps are as follows:

[0056] 1) Weigh 90g of ionic liquid and 93g of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde (DMTA), add 2.0L of 1,4-dioxane and 2.0L of mesitylene, sonicate for 10min, then slowly add 1.0L of 3M acetic acid, and sonicate for 10min.

[0057] 2) Disperse 112g of 1,3,5-tris(4-aminophenyl)benzene (TAPB) in 2.0L of 1,4-dioxane and 2.0L of mesitylene, then add the solution prepared in step 1), and shake at room temperature for 20 minutes;

[0058] 3) The solution obtained in step 2) was allowed to stand and filtered, and the yellow-brown precipitate was collected. It was washed three times with anhydrous methanol to remove impurities and made into 2-3 mm particles. The particles were placed in a vacuum drying oven at 60°C and a vacuum degree below -94 kPa for 12 hours to obtain the packing material.

[0059] Specifically, in step 1), the ionic liquid is 1-ethyl-3-methylimidazolium hydrogen sulfate.

[0060] A pressure-resistant buffer tank is connected to the outlet of the supercritical fluid extraction vessel. Liquid or semi-solid samples are retained in the tank, which is the crude terpene extract. Carbon dioxide gas flows through the buffer tank back to the adsorption column, where essential oil components are adsorbed and retained, while carbon dioxide flows out. The adsorption column is eluted with ethanol to obtain an alcoholic solution of the essential oil for further applications. For applications that do not require ethanol, the essential oil can be obtained by heating and desorption followed by condensation in a cold trap.

[0061] Ionic liquids (ILs) and covalent organic frameworks (COFs) are often used as composite catalytic materials, as their porous structures facilitate sufficient contact between the catalyst and reactants. Some ionic liquid-COF composites (IL@COFs) can be used as selective adsorbents due to their excellent three-dimensional porous structure and superior thermal stability.

[0062] Differences in the material composition of liquid and gas phase adsorbates in supercritical fluid extraction:

[0063] The liquid phase obtained by supercritical fluid extraction was a crude terpene extract, with over 60 components identified, including 12 components with a content exceeding 1%, as shown in the table below. These are mostly terpenoids, with phytol, neophytadiene, β-amyrinone, squalene, trefoil ketone, and β-sitosterol being the six most abundant. The gas phase (concentrated essential oil) obtained by supercritical fluid extraction identified over 30 components, including six components with a content exceeding 1%. The most abundant were 2-hexenal, leaf alcohol, and trans-2-hexen-1-ol, similar to the volatile components of *Imperata cylindrica* leaves.

[0064] Table of main liquid phase components in supercritical carbon dioxide extraction (>1%)

[0065] Serial Number English name of compound compound Chinese name content% 1 Phytol Phytophthol 36.52 2 Campesterol campesterol 1.01 3 β-Sitosterol β-sitosterol 8.77 4 (Z,Z)-9,12-Octadecadienoic acid Ethyl linoleate 1.85 5 β-Amyrone β-amyrinone 5.82 6 Friedelin Cork ketone 5.06 7 Hexadecanoic acid, methyl ester Methyl palmitate 1.07 8 2-Palmitoylglycerol 2-Monopalmitoylglycerol 1.89 9 1,2,3-Trielaidoyl Glycerol Tritrans-oleic acid glyceride 1.74 10 Squalene Squalene 3.24 11 Neophytadiene Neophytadiene 2.81 12 Vitamin E Vitamin E 1.32

[0066] Table of main gas phase (concentrated essential oil) components from supercritical carbon dioxide extraction (>1%)

[0067] Serial Number English name Chinese name content% 1 3-Hexenal 3-Hexenal 3.3415 2 1-Penten-3-ol 1-Penten-3-ol 1.2051 3 2-Hexenal 2-Hexenal 54.5947 4 3-Hexen-1-ol 3-Hexen-1-ol (Leaf Alcohol) 9.668 5 2-Hexen-1-ol,(E)- trans-2-hexen-1-ol 4.5664 6 1,6-Octadien-3-ol,3,7-dimethyl-; Linalool 3,7-Dimethyl-1,6-octadien-3-ol (Linalyl alcohol) 1.12

[0068] Comparison of different adsorbents:

[0069] GCMS analysis under the same conditions was performed using 3-hexen-1-ol standards at different concentrations. The fitting equation for peak area versus injection volume was obtained, yielding the linear fitting equation: y = 8.4667E8x + 8.24561E8, with R0... 2 =0.97, where x is the injection amount of 3-hexen-1-ol and y is the peak area. The content of 3-hexen-1-ol in the sample was calculated using the fitted equation, and the total adsorption and extraction amount was then estimated based on the percentage content of 3-hexen-1-ol.

[0070] Experiments were conducted using 1 kg of raw material and 100 g of adsorbent, respectively, to compare the preferred adsorbent of this invention, activated carbon, polydimethylsiloxane, polyvinylbenzene, polyvinyl alcohol, and other different adsorbents. The results are as follows: Figure 1 Among them, the adsorbent of the present invention has obvious advantages and is significantly different from other materials, with an adsorption efficiency 2.49 times that of the worst activated carbon.

[0071] Any content not described in detail in this specification is prior art known to those skilled in the art.

[0072] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the scope of protection of the present invention. Any modifications and refinements made by those skilled in the art without departing from the concept and scope of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for simultaneously preparing terpenoids and essential oils from bamboo leaves, characterized in that, Includes the following steps: (1) Using bamboo leaves as raw material, wash and dry the raw material, and grind it into 10-20 mesh; (2) The pulverized raw material was added to the supercritical carbon dioxide extraction vessel and extracted for 4.5 hours under the conditions of extraction pressure of 30 MPa, temperature of 40℃ and separation pressure of 8 MPa. (3) After extraction, the pressure of the separation vessel is reduced to 2 MPa. The outlet of the separation vessel is connected to a buffer tank. The liquid sample is collected in the buffer tank to obtain crude extract of terpenoids from bamboo leaves. The gas sample flows through the buffer tank and then through the adsorption column to collect essential oil components. (4) Elute the adsorption column in step (3) with 3 column volumes of anhydrous ethanol to obtain a bamboo leaf essential oil alcohol solution; or, desorb the adsorption column in step (3) by heating to 280°C at a rate of 10°C / second and collect the bamboo leaf essential oil in a liquid nitrogen cold trap.

2. The method for simultaneous preparation of terpenoids and essential oils from bamboo leaves according to claim 1, characterized in that, In step (1), the raw material is freshly picked bamboo leaves with a moisture content of 60%.

3. The method for simultaneous preparation of terpenoids and essential oils from bamboo leaves according to claim 1, characterized in that, In step (3), the packing material of the adsorption column is 2-3 mm particle adsorbent.

4. The method for simultaneous preparation of terpenoids and essential oils from bamboo leaves according to claim 1, characterized in that, In step (3), the adsorption column packing material is a synthetic material composed of ionic liquid and covalent organic framework. The synthesis steps are as follows: 1) Weigh 60-200g of ionic liquid and 80-100g of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde, add 2.0L of 1,4-dioxane and 2.0L of mesitylene, sonicate for 10min, then slowly add 1.0L of 3M acetic acid and sonicate for 10min. 2) Disperse 100-120g of 1,3,5-tris(4-aminophenyl)benzene in 2.0L of 1,4-dioxane and 2.0L of mesitylene, then add the solution prepared in step 1), and shake at room temperature for 20 minutes; 3) The solution obtained in step 2) was allowed to stand and filtered, and the yellow-brown precipitate was collected. It was washed three times with anhydrous methanol to remove impurities and made into 2-3 mm particles. The particles were placed in a vacuum drying oven at 60°C and a vacuum degree below -94 kPa for 12 hours to obtain the packing material.

5. The method for simultaneous preparation of terpenoids and essential oils from bamboo leaves according to claim 4, characterized in that, In step 1), the ionic liquid is 1-ethyl-3-methylimidazolium hydrogen sulfate, 1-ethyl-3-methylimidazolium acetate, or 1-octyl-3-methylimidazolium bromide.

6. The method for simultaneous preparation of terpenoids and essential oils from bamboo leaves according to claim 4, characterized in that, In step 1), the amount of ionic liquid used is 90g; the amount of 2,5-dimethoxybenzene-1,4-dicarboxaldehyde used is 93g.

7. The method for simultaneous preparation of terpenoids and essential oils from bamboo leaves according to claim 4, characterized in that, In step 2), the amount of 1,3,5-tris(4-aminophenyl)benzene used is 112g.

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