Solvent-free microwave-assisted extraction process of ledum palustre volatile oil by negative pressure method

Abstract

The invention discloses a negative pressure method solvent-free microwave-assisted extraction process of ledum palustre volatile oil, which comprises the following steps: cutting branches of ledum palustre into sections, and removing impurities; soaking the ledum palustre branch sections in water for pretreatment; putting the pretreated ledum palustre branch sections into a round-bottom flask, and transferring the round-bottom flask into a microwave device; vacuumizing treatment is carried out, after certain negative pressure is achieved, the microwave power and the heating time are adjusted, and essential oil extraction is carried out; after extraction is completed, volatile oil components are collected, petroleum ether is added for cleaning, the washed petroleum ether is combined, the concentrated petroleum ether is combined with collected oily substances, and the ledum palustre essential oil is obtained. According to the method, the boiling point of the system is reduced under the negative pressure condition, heat-sensitive components in the volatile oil are effectively protected, cell walls are damaged by microwaves for extraction, and the dissolution rate of the volatile oil in ledum palustre cells is increased by controlling the microwave power and the extraction time, so that the ledum palustre volatile oil with more chemical components is obtained; the ledum palustre volatile oil is simply and efficiently extracted.

Description

Technical Field

[0001] The present invention relates to the technical field of volatile oil extraction, and particularly relates to an extraction process of Ledum palustre volatile oil by negative pressure solvent-free microwave assistance. Background Art

[0002] Ledum palustre L. is an evergreen shrub belonging to the genus Ledum of the Ericaceae family. It is an important aromatic plant, rich in volatile oil components. Ledum palustre has a strong aromatic smell and can be used medicinally and for extracting essential oils. Ledum palustre essential oil has functions such as relieving cough, reducing phlegm, sterilizing, killing mites, expelling worms, and promoting transdermal absorption, and has antibacterial effects and inhibits the growth of various fungi and bacteria.

[0003] At present, the main extraction methods of Ledum palustre essential oil include steam distillation method, compound solvent extraction method, supercritical CO 2 extraction method, microwave distillation method, etc. The steam distillation method for extracting volatile oil is a commonly used method by domestic and foreign manufacturers at present because of its simple equipment and low cost. In the microwave-assisted solvent-free method, the cell wall destruction caused by microwave irradiation can break the plant cell wall more efficiently and thoroughly, increasing the extraction efficiency of volatile oil. The solvent-free microwave extraction method uses the water in the plant itself to absorb microwaves and heat the extraction system, which can shorten the extraction time, reduce energy consumption, have a higher oil extraction rate, be green and environmentally friendly, do not require the addition of any organic solvents, can focus on extracting a certain component in the volatile oil by changing the power, and can well protect the natural active components in the volatile oil from being damaged. However, the extraction temperature of the microwave-assisted method is too high, and some of the active components therein are denatured by heat, which is not conducive to the protection of heat-sensitive substances. Therefore, negative pressure is further introduced into the system. Negative pressure can lower the boiling point of the solvent, and the extraction can be carried out in a relatively mild environment, which is conducive to protecting the heat-sensitive components in the volatile oil and improving the extraction yield of volatile oil. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an extraction process of Ledum palustre volatile oil by negative pressure solvent-free microwave assistance. By means of negative pressure conditions, the boiling point of the system is lowered, that is, the extraction temperature is reduced, so as to effectively protect the heat-sensitive components in the volatile oil. Then, microwave extraction is used, and the essential oil is extracted without solvent through the water in the cells themselves. The microwave further destroys the cell wall. By controlling the microwave power and extraction time, the dissolution rate of the volatile oil in Ledum palustre cells is increased, and more chemical components of Ledum palustre volatile oil can be obtained, realizing the simple and efficient extraction of Ledum palustre volatile oil.

[0005] The technical problem to be solved by the present invention is realized through the following technical solutions:

[0006] An extraction process of Ledum palustre volatile oil by negative pressure solvent-free microwave assistance, comprising the following steps:

[0007] (1) Inspect the Ledum palustre branches, cut them into Ledum palustre branch segments, and remove impurities;

[0008] (2) Immerse the Ledum palustre branch segments obtained in step (1) in water for pretreatment;

[0009] (3) Put the Ledum palustre branch segments pretreated in step (2) into a round-bottom flask, move the round-bottom flask into a microwave device, and assemble and set up the extraction device;

[0010] (4) Conduct a vacuum treatment on the extraction device, use a pump to extract pressure to make the pressure reach 10 - 90 Kpa;

[0011] (5) After reaching the negative pressure in step (4), adjust the microwave power to 126 W - 700 W and the heating time to 30 min - 60 min for essential oil extraction;

[0012] (6) After the extraction is completed, collect the volatile oil components in the extraction device, add petroleum ether to clean the extraction device, combine the washed petroleum ether, concentrate it and combine it with the collected oily substances, which is the Ledum palustre essential oil.

[0013] Preferably, in the above technical solution, in step (1), the length of the Ledum palustre branch segments is 1 cm.

[0014] Preferably, in the above technical solution, in step (3), the extraction device includes: a vacuum tube elbow joint (1), the upper end of which is connected to a vacuum oil-free diaphragm pump (8) through a pipeline, a negative pressure valve (6) and a tee joint (7) are arranged on the pipeline, the lower end of the vacuum tube elbow joint (1) is connected to the upper end of a serpentine condenser (2), the lower end of the serpentine condenser (2) is connected to the upper end of a light oil extractor (3), the lower end of the light oil extractor (3) is connected to a round-bottom flask (9) through a vacuum joint (4), and the round-bottom flask (9) is placed in a microwave oven (5).

[0015] Preferably, in the above technical solution, in step (4), the pressure is 80 Kpa.

[0016] Preferably, in the above technical solution, in step (5), the power of the microwave device is 252 W and the heating time is 60 min.

[0017] Preferably, in the above technical solution, step (6) is specifically: after the extraction is completed, collect the volatile oil components in the upper half of the light oil extractor of the extraction device, add petroleum ether to clean the light oil extractor 3 times, combine the washed petroleum ether, concentrate it and combine it with the oily substances above the light oil extractor collected, which is the Ledum palustre essential oil.

[0018] An extraction device for the extraction process of Ledum palustre volatile oil by negative pressure solvent-free microwave-assisted method. The extraction device includes: a vacuum tube elbow joint, the upper end of which is connected to a vacuum oil-free diaphragm pump through a pipeline. A negative pressure valve and a three-way joint are arranged on the pipeline. The lower end of the vacuum tube elbow joint is connected to the upper end of a serpentine condenser. The lower end of the serpentine condenser is connected to the upper end of a light oil extractor. The lower end of the light oil extractor is connected to a round-bottom flask through a vacuum joint. The round-bottom flask is placed in a microwave oven.

[0019] Preferably, in the above technical solution, the three-way joint is arranged between the vacuum oil-free diaphragm pump and the negative pressure valve, and one end of the negative pressure valve far away from the three-way joint is connected to the vacuum tube elbow joint.

[0020] Preferably, in the above technical solution, the outer wall of the serpentine condenser is fixedly connected to a test tube rack, and the extraction device is supported by the test tube rack.

[0021] Preferably, in the above technical solution, the light oil extractor is a U-shaped structure with an opening facing downwards. One end of it is connected to the vacuum joint, and a regulating valve is arranged at the bottom of the other end.

[0022] The above technical solution of the present invention has the following beneficial effects:

[0023] (1) The present invention uses the solvent-free microwave extraction method to extract Ledum palustre volatile oil. Microwave irradiation severely damages the cell structure of Ledum palustre, and microwave heats the water in the Ledum palustre cells, bringing out the Ledum palustre volatile oil, improving the dissolution rate of the volatile oil in Ledum palustre cells, and greatly shortening the extraction time, from 3 hours to 1 hour, greatly improving the extraction efficiency. The extraction rate of Ledum palustre volatile oil can reach up to 0.0472%. Compared with the steam distillation method with an extraction rate of 0.0408% and the solvent-free microwave method with an extraction rate of 0.031%, the negative pressure solvent-free microwave method of the present application has a higher volatile oil extraction rate, is simple to operate, and is green and efficient.

[0024] (2) The present invention reduces the boiling point of the system under negative pressure conditions, that is, reduces the extraction temperature, thereby effectively protecting the thermosensitive components in the volatile oil and improving the extraction efficiency. Through GC-MS analysis and identification, many chemical components are identified and the components are rich.

[0025] (3) The preparation method of the present invention has low cost, is simple to prepare, easy to operate, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present invention and, together with the description, are used to explain the principles of the present invention.

[0027] Figure 1It is the total ion current chromatogram of GC-MS of Ledum palustre volatile oil extracted by the negative pressure solvent-free microwave method of the present invention;

[0028] Figure 2 It is the total ion current chromatogram of GC-MS of Ledum palustre volatile oil extracted by steam distillation in the comparative example of the present invention;

[0029] Figure 3 It is the total ion current chromatogram of GC-MS of Ledum palustre volatile oil extracted by solvent-free microwave extraction in the comparative example of the present invention;

[0030] Figure 4 It is the structural schematic diagram of the experimental invention device of the present invention.

[0031] Among them: 1. Vacuum tube elbow joint; 2. Serpentine condenser; 3. Light oil extractor; 4. Vacuum joint; 5. Microwave oven; 6. Negative pressure valve; 7. Three-way joint; 8. Vacuum oil-free diaphragm pump; 9. Round bottom flask. Detailed implementation mode

[0032] Now, various exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that: Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention.

[0033] Example 1

[0034] A pre-experiment for extracting Ledum palustre essential oil was carried out, and the method is as follows:

[0035] The Ledum palustre branches were cut into small sections of 1 cm, 30 g was weighed, and it was pretreated by soaking in sterile water for a period of time.

[0036] The pretreated Ledum palustre was placed in a 1000 mL round bottom flask, the device was set up and connected to an air pump. The microwave power in the microwave oven was adjusted to 252 W, the extraction time was 60 min, and the pressure was 80 Kpa. The oily substance above the light oil extractor was collected, and the light oil extractor was washed 3 times with petroleum ether. The washed petroleum ether was combined, concentrated and then combined with the oily substance collected above the light oil extractor, which is the Ledum palustre essential oil.

[0037] The following formula was used: Ledum palustre essential oil extraction rate = mass of Ledum palustre essential oil / mass of Ledum palustre dry powder to calculate the Ledum palustre essential oil extraction rate.

[0038] The chemical components of Ledum palustre volatile oil were analyzed. The total ion current of Ledum palustre volatile oil GC-MS is as Figure 1 shown, and the specific chemical components are shown in Table 1.

[0039] Table 1 Analysis results of chemical components of Ledum palustre volatile oil extracted by negative pressure solvent-free microwave-assisted extraction

[0040]

[0041]

[0042] The extraction device of the present invention mainly consists of the following components: vacuum tube elbow joint 1, serpentine condenser 2, light oil extractor 3, vacuum joint 4, microwave oven 5, negative pressure valve 6, tee 7, vacuum oil-free diaphragm pump 8, and round-bottom flask 9. The specific connection relationship is as follows:

[0043] The vacuum oil-free diaphragm pump 8 is connected to the vacuum tube elbow joint 1 through a pipeline, and the negative pressure valve 6 and tee 7 are provided on this pipeline. The vacuum oil-free diaphragm pump 8 is used to provide a negative pressure environment; the negative pressure valve 6 is used to control the opening and closing of the negative pressure and adjust the negative pressure conditions; the tee 7 is used to connect different pipelines to ensure the smoothness of the gas path; the vacuum tube elbow joint 1 is used to connect the vacuum pump and the extraction system to ensure the stable transmission of the negative pressure.

[0044] The upper end of the serpentine condenser 2 is connected to the lower end of the vacuum tube elbow joint 1, the lower end of the serpentine condenser 2 is connected to the upper end of the light oil extractor 3, the lower end of the light oil extractor 3 is connected to the round-bottom flask 9 through the vacuum joint 4, and the round-bottom flask 9 is placed in the microwave oven 5. The serpentine condenser 2 is used to condense the volatile oil and improve the extraction efficiency. The light oil extractor 3 is used to collect the volatile oil components for subsequent separation and extraction. The vacuum joint 4 is used to connect the vacuum pipeline to ensure the sealing performance. The microwave oven 5 is used to provide microwave energy to break the cell wall of Ledum palustre and promote the dissolution of the volatile oil. The round-bottom flask 9 serves as a reaction vessel for loading Ledum palustre branches and water.

[0045] Example 2

[0046] A single-factor experiment on the extraction of Ledum palustre essential oil was carried out as follows:

[0047] (1) Pressure factor

[0048] The Ledum palustre branches were cut into 1-cm small sections, 30 g was weighed, and it was pretreated by soaking in sterile water for a period of time.

[0049] The pretreated Ledum palustre was placed in a 1000-mL round-bottom flask, the device was set up and connected to the air pump. The microwave power in the microwave oven was adjusted to 252 W, the extraction time was 60 min, and the pressure was 10 - 90 Kpa. The oily substance above the light oil extractor was collected, and the light oil extractor was washed 3 times with petroleum ether. The washed petroleum ether was combined, concentrated, and then combined with the oily substance above the light oil extractor to obtain Ledum palustre essential oil.

[0050] The following formula was used: extraction rate of Ledum palustre essential oil = mass of Ledum palustre essential oil / mass of Ledum palustre dry powder to calculate the extraction rate of Ledum palustre essential oil.

[0051] (2) Microwave power

[0052] The Ledum palustre L. twigs were cut into small sections of 1 cm, 30 g was weighed, and it was pretreated by soaking in sterile water for a period of time.

[0053] The pretreated Ledum palustre L. was placed in a 1000 mL round-bottom flask, the device was set up and connected to an air pump. The microwave power in the microwave oven was adjusted to 126 - 700 W, the extraction time was 60 min, and the pressure was 80 Kpa. The oily substance above the light oil extractor was collected, and the light oil extractor was washed 3 times with petroleum ether. The washed petroleum ether was combined, concentrated and then combined with the oily substance above the light oil extractor, which was the Ledum palustre L. essential oil.

[0054] The following formula was used: extraction rate of Ledum palustre L. essential oil = mass of Ledum palustre L. essential oil / mass of Ledum palustre L. dry powder to calculate the extraction rate of Ledum palustre L. essential oil.

[0055] (3) Factor of extraction time

[0056] The Ledum palustre L. twigs were cut into small sections of 1 cm, 30 g was weighed, and it was pretreated by soaking in sterile water for a period of time.

[0057] The pretreated Ledum palustre L. was placed in a 1000 mL round-bottom flask, the device was set up and connected to an air pump. The microwave power in the microwave oven was adjusted to 567 W, the extraction time was 30 - 90 min, and the pressure was 80 Kpa. The oily substance above the light oil extractor was collected, and the light oil extractor was washed 3 times with petroleum ether. The washed petroleum ether was combined, concentrated and then combined with the oily substance above the light oil extractor, which was the Ledum palustre L. essential oil.

[0058] The following formula was used: extraction rate of Ledum palustre L. essential oil = mass of Ledum palustre L. essential oil / mass of Ledum palustre L. dry powder to calculate the extraction rate of Ledum palustre L. essential oil.

[0059] Control example

[0060] The Ledum palustre L. essential oil was extracted by the currently common method as follows:

[0061] (1) Extracting the volatile oil of Ledum palustre L. by steam distillation

[0062] The Ledum palustre L. twigs were cut into small sections of 1 cm, 80 g was weighed, and it was pretreated by soaking in sterile water for a period of time.

[0063] The pretreated Ledum palustre L. was placed in a 3000 mL round-bottom flask, and 1200 mL of water was added to the round-bottom flask at a ratio of Ledum palustre L. twigs to water (mass ratio) of 1:15. Steam distillation was carried out for 3 h. The oily substance above the light oil extractor was collected, and the light oil extractor was washed 3 times with petroleum ether. The washed petroleum ether was combined, concentrated and then combined with the oily substance above the light oil extractor, which was the Ledum palustre L. essential oil. The extraction rate was 0.0408%.

[0064] The chemical components of Ledum palustre essential oil were analyzed. The total ion current of Ledum palustre essential oil by GC-MS is as Figure 2 shown, and the specific chemical components are shown in Table 2.

[0065] Table 2 Analysis results of chemical components of Ledum palustre essential oil extracted by steam distillation

[0066]

[0067]

[0068]

[0069] (2) Solvent-free microwave extraction of Ledum palustre essential oil

[0070] The branches and stems of Ledum palustre were cut into small sections of 1 cm, 30 g was weighed, and it was pretreated by soaking in sterile water for a period of time.

[0071] The pretreated Ledum palustre was placed in a 1000 mL round-bottom flask, and the microwave power was adjusted to 567 W in the microwave oven, and the extraction time was 60 min. The oily substances above the light oil extractor were collected, and the light oil extractor was washed 3 times with petroleum ether. The washed petroleum ether was combined, concentrated and combined with the oily substances above the light oil extractor, which was Ledum palustre essential oil. The extraction rate was 0.031%.

[0072] The chemical components of Ledum palustre essential oil were analyzed. The total ion current of Ledum palustre essential oil by GC-MS is as Figure 3 shown, and the specific chemical components are shown in Table 3.

[0073] Table 3 Analysis results of chemical components of Ledum palustre essential oil extracted by solvent-free microwave extraction

[0074]

[0075]

[0076] By comparing with the above two extraction methods of Ledum palustre essential oil, the extraction rate of solvent-free microwave extraction of Ledum palustre essential oil with negative pressure treatment is the highest.

[0077] The Ledum palustre essential oil obtained from the application example was detected by GC-MS. The gas chromatography conditions were as follows: capillary quartz chromatographic column (0.25 mm×0.25 μm, 30 m in length), the carrier gas was high-purity helium, the flow rate was 1 L / min, the split ratio was 1:20, the inlet temperature was 250 °C, and the programmed temperature rise: the initial temperature was 50 °C, held for 2 min, raised to 160 °C at 4 °C / min, held for 2 min: raised to 270 °C at 4 °C / min, and held for 5 min.

[0078] Mass spectrometry conditions: Electron impact (EI) ion source; electron energy is 70 eV; scanning range is 15 - 500 amu.

[0079] There are certain differences in the types of compounds contained in the volatile oils of Ledum palustre L. obtained by three extraction methods identified by GC - MS, but the main components are roughly the same. The proportion of oxygen - containing compounds in the volatile oils extracted by solvent - free microwave method and negative - pressure solvent - free microwave method is relatively high. This may be because oxygen - containing compounds have a larger dipole moment, so under the irradiation of microwave, their interaction is more intense than that of sesquiterpene hydrocarbons with low dipole moment. Therefore, they can be extracted more completely from plant materials. At the same time, oxygen - containing compounds have a significant fragrance, so they are more valuable than sesquiterpene hydrocarbons.

[0080] Therefore, the present invention adopts the above - mentioned extraction process of negative - pressure solvent - free microwave - assisted extraction of Ledum palustre L. volatile oil. By means of negative - pressure conditions, the boiling point of the system is reduced, that is, the extraction temperature is lowered, thus effectively protecting the thermosensitive components in the volatile oil. Then, microwave extraction is used. Microwave further destroys the cell wall. By controlling the microwave power, extraction time and negative - pressure conditions, the dissolution rate of volatile oil in Ledum palustre L. cells is increased, and more volatile oil with chemical components can be obtained, realizing the simple and efficient extraction of Ledum palustre L. volatile oil.

[0081] Although the present invention has been disclosed as above with embodiments, it is not used to limit the present invention. Any person skilled in the art can make various different selections and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is defined by the claims and their equivalent forms.

Claims

1. A solvent-free microwave-assisted extraction process of Ledum palustris volatile oil by negative pressure method, characterized in that: The following steps are involved: (1) Check the Ledum branches and cut them into Ledum branch segments to remove impurities; (2) soaking the Ledum palustris branch segments obtained in step (1) in water for pretreatment; (3) placing the Ledum palustris branch segments pretreated in step (2) into a round-bottom flask, moving the round-bottom flask into a microwave device, and assembling and building an extraction device; (4) evacuate the extraction device and use a pump to extract the pressure to reach 10 to 90 KPa; (5) After reaching the negative pressure of step (4), adjusting the microwave power to 126W-700W and the heating time to 30min-60min to extract the essential oil; (6) After the extraction is completed, the volatile oil components in the extraction device are collected, and petroleum ether is added to clean the extraction device. The petroleum ether after washing is combined, concentrated and combined with the collected oily substance to obtain Ledum palustris essential oil.

2. The solvent-free microwave-assisted extraction process of Ledum palustris volatile oil by negative pressure method according to claim 1, characterized in that: In step (1), the length of the Ledum palustris branch segment is 1 cm.

3. The solvent-free microwave-assisted extraction process of Ledum palustris volatile oil by negative pressure method according to claim 1, characterized in that: In step (3), the extraction device comprises: a vacuum tube elbow (1), the upper end of which is connected to a vacuum oil-free diaphragm pump (8) through a pipeline, the pipeline is provided with a negative pressure valve (6) and a tee (7), the lower end of the vacuum tube elbow (1) is connected to the upper end of a serpentine condenser (2), the lower end of the serpentine condenser (2) is connected to the upper end of a light oil extractor (3), the lower end of the light oil extractor (3) is connected to a round-bottom flask (9) through a vacuum joint (4), and the round-bottom flask (9) is placed in a microwave oven (5).

4. The solvent-free microwave-assisted extraction process of Ledum palustris volatile oil by negative pressure method according to claim 1, characterized in that: In step (4), the pressure is 80 KPa.

5. The solvent-free microwave-assisted extraction process of Ledum palustris volatile oil by negative pressure method according to claim 1, characterized in that: In step (5), the power of the microwave device is 252 W and the heating time is 60 min.

6. The solvent-free microwave-assisted extraction process of Ledum palustris volatile oil by negative pressure method according to claim 1, characterized in that: Step (6) specifically comprises: after the extraction is completed, collecting the volatile oil components in the upper part of the light oil extractor of the extraction device, adding petroleum ether to wash the light oil extractor three times, combining the washed petroleum ether, concentrating and combining with the collected oily substance above the light oil extractor, thus obtaining Ledum essential oil.

7. An extraction device for solvent-free microwave-assisted extraction of Ledum palustris volatile oil by negative pressure method, characterized in that: The extraction device comprises: a vacuum pipe elbow (1), the upper end of which is connected to a vacuum oil-free diaphragm pump (8) through a pipeline, the pipeline is provided with a negative pressure valve (6) and a tee (7), the lower end of the vacuum pipe elbow (1) is connected to the upper end of a serpentine condenser (2), the lower end of the serpentine condenser (2) is connected to the upper end of a light oil extractor (3), the lower end of the light oil extractor (3) is connected to a round-bottom flask (9) through a vacuum joint (4), and the round-bottom flask (9) is placed in a microwave oven (5).

8. The extraction device according to claim 7, characterized in that The tee (7) is arranged between the vacuum oil-free diaphragm pump (8) and the negative pressure valve (6), and one end of the negative pressure valve (6) away from the tee (7) is connected to the vacuum pipe elbow (1).

9. The extraction device according to claim 7, characterized in that: The outer wall of the serpentine condenser tube (2) is connected and fixed to a test tube rack, and the extraction device is supported by the test tube rack.

10. The extraction device according to claim 7, characterized in that: The light oil extractor (3) is a U-shaped structure with its opening facing downward, one end of which is connected to the vacuum joint (4), and a regulating valve is provided at the bottom of the other end.

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