JP7687341B2 - Method for decomposing flavonoid glycosides and method for producing flavonoids - Google Patents

Description

The present invention relates to a method for decomposing flavonoid glycosides and a method for producing flavonoids.

Flavonoids are a group of naturally occurring organic compounds found in the flowers, leaves, roots, stems, fruits, seeds, etc. of various plants, including citrus fruits and beans. Flavonoids have different characteristics and effects depending on the type, but many of them have strong antioxidant properties. For example, polymethoxyflavones, a flavonoid found in citrus fruits, are known to have antioxidant, anti-carcinogenic, antibacterial, antiviral, anti-allergic, melanin production inhibitory, and blood sugar level inhibitory effects, and are expected to be used in a variety of applications such as medicines, health foods, and cosmetics.

Known methods for producing flavonoids from citrus fruits include extracting flavonoids from citrus peels, etc., with an aqueous ethanol solution and recovering the extracted flavonoids from the solution (see, for example, Patent Document 1).

JP 2005-145824 A

However, conventional methods for producing flavonoids have the problem of low flavonoid yields. Therefore, there is a demand for the development of a production method that can improve the yield of flavonoids.

For example, the peel of citrus fruits contains a larger amount of flavonoid glycosides than flavonoids. If these can be recovered as flavonoids, it is possible to improve the yield of flavonoids. One method for decomposing flavonoid glycosides into flavonoids is to react the flavonoid glycosides with an acid such as hydrochloric acid. However, this method has problems in that the acid used may remain and be mixed into the product, and side reaction products between the acid and the flavonoids may be generated. One method for removing impurities such as acids and by-products is to separate and purify the flavonoids in the decomposition products by liquid chromatography, but this method is expensive and has problems in terms of production efficiency. Therefore, a new method for decomposing flavonoid glycosides without using acids is required.

The present invention has been made in consideration of the problems associated with the above-mentioned conventional techniques, and aims to provide a method for decomposing flavonoid glycosides, which can efficiently decompose flavonoid glycosides into flavonoids without using acid, and can improve the yield of flavonoids, and a method for producing flavonoids.

In order to achieve the above object, the present invention provides a method for decomposing flavonoid glycosides, which comprises a hydrothermal treatment step of placing a raw material container containing a raw material liquid containing flavonoid glycosides in an autoclave and hydrothermally treating the raw material liquid to decompose the flavonoid glycosides into flavonoids, and the surface of the raw material container that comes into contact with the raw material liquid has a contact angle with water of less than 35° at a measurement temperature of 25°C.

According to the above method, flavonoid glycosides can be efficiently decomposed into flavonoids by hydrothermal treatment without using acid. Furthermore, by using this method, it is possible to efficiently produce flavonoids at low cost.

The inventors have also found that in a method for decomposing flavonoid glycosides by hydrothermal treatment, glycoside decomposition products precipitate after hydrothermal treatment and adhere to the contact surface of the raw material container with the raw material liquid. The glycoside decomposition products include flavonoids decomposed by glycoside decomposition and caramel reaction products of the generated sugars. When a stainless steel container or a container made of polytetrafluoroethylene resin, which are common raw material containers, is used as is, the precipitates adhere strongly to the contact surface of the raw material container with the raw material liquid, and in order to remove them, it is necessary to strongly rub the contact surface with a medicine spoon or the like for a long time, and it takes a long time to remove the glycoside decomposition products. In addition, since the contact surface of the raw material container with the raw material liquid is strongly rubbed with a medicine spoon or the like, the contact surface or the medicine spoon may be scraped, and there is a risk of contamination with foreign matter. In order to solve these problems, the present inventors have conducted extensive research and found that, by making the contact surface of the raw material container with the raw material liquid a surface having a contact angle with water of less than 35° at a measurement temperature of 25°C, adhesion of glycoside degradation products to the contact surface can be suppressed, and the yield of flavonoids can be improved even when the time for removing the glycoside degradation products is short. The present inventors speculate that, by making the contact surface of the raw material container with the raw material liquid a surface having a contact angle with water of less than 35° at a measurement temperature of 25°C, adhesion of glycoside degradation products to the contact surface can be suppressed as follows. That is, glycoside degradation products are hydrophobic. In contrast, the contact surface of the raw material container with the raw material liquid has a contact angle with water of less than 35° at a measurement temperature of 25°C and is hydrophilic. Therefore, the hydrophobic glycoside degradation products and the hydrophilic contact surface with the raw material liquid repel each other. As a result, the precipitated glycoside degradation products are less likely to adhere to the contact surface of the raw material container.

In the above decomposition method, the contact surface may be an enameled surface. By using an enameled surface as the contact surface, the contact angle of the contact surface with water at a measurement temperature of 25°C can be further reduced, making it even more difficult for the precipitated glycoside decomposition products to adhere to the raw material container.

In the above decomposition method, the contact surface may be a surface treated with a polysilazane compound. By treating the contact surface with a polysilazane compound, the contact angle of the contact surface with water at a measurement temperature of 25°C can be further reduced, making it even more difficult for the precipitated glycoside decomposition products to adhere to the raw material container.

The polysilazane compound may be perhydropolysilazane. By using perhydropolysilazane as the polysilazane compound, the contact angle of the contact surface with water at a measurement temperature of 25°C can be further reduced, making it even more difficult for the precipitated glycoside decomposition products to adhere to the raw material container.

In the above decomposition method, the hydrothermal treatment may be performed by supplying water vapor from the outside into the autoclave. By supplying water vapor from the outside, the temperature and pressure inside the autoclave can be raised in a short period of time, and a hydrothermal treatment environment can be easily formed and maintained.

In the hydrothermal treatment step of the decomposition method, the pressure inside the autoclave may be 0.2 to 1.6 MPa and the temperature may be 120 to 200° C. By carrying out hydrothermal treatment within the above pressure and temperature ranges, flavonoid glycosides can be decomposed into flavonoids more efficiently, and the yield of flavonoids can be further improved.

In the above-mentioned decomposition method, the above-mentioned flavonoid glycoside may include sudachitin glycoside and/or demethoxysudachitin glycoside. According to the above-mentioned decomposition method, sudachitin glycoside and demethoxysudachitin glycoside can be decomposed particularly efficiently.

The present invention also provides a method for producing a flavonoid, comprising a decomposition step of decomposing a flavonoid glycoside by the decomposition method of the present invention, and an extraction step of extracting a flavonoid from the decomposition product obtained in the decomposition step. According to this production method, a flavonoid can be produced efficiently at a high yield and at low cost.

According to the present invention, a method for decomposing flavonoid glycosides and a method for producing flavonoids can be provided that can efficiently decompose flavonoid glycosides into flavonoids without using acid and improve the yield of flavonoids.

FIG. 2 is a schematic cross-sectional view showing an example of an autoclave used in the method for decomposing a flavonoid glycoside of the present embodiment.

Below, a preferred embodiment of the present invention will be described in detail, with reference to the drawings where necessary. However, the present invention is not limited to the following embodiment. Furthermore, the dimensional ratios of the drawings are not limited to the ratios shown in the drawings.

In this specification, a numerical range indicated using "~" indicates a range including the numerical values before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in stages in this specification, the upper limit or lower limit of a numerical range of a certain stage can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage. In the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with a value shown in the examples. "A or B" may include either A or B, or may include both. Unless otherwise specified, the materials exemplified in this specification may be used alone or in combination of two or more types.

(Method of Decomposing Flavonoid Glycosides)
The method for decomposing a flavonoid glycoside according to this embodiment includes a hydrothermal treatment step in which a raw material container containing a raw material liquid containing a flavonoid glycoside is placed in an autoclave and the raw material liquid is subjected to hydrothermal treatment to decompose the flavonoid glycoside into a flavonoid, and the surface of the raw material container that comes into contact with the raw material liquid has a contact angle with water of less than 35° at a measurement temperature of 25°C.

Flavonoid glycosides are hydrophilic compounds that have a structure in which a flavonoid and a sugar are bound by a glycosidic bond. The flavonoids that are the source of flavonoid glycosides are aromatic compounds that have a phenylchroman skeleton as a basic structure, and examples of such compounds include flavones, flavonols, flavanones, flavanonols, isoflavones, anthocyanins, flavanols, chalcones, and aurones. Among these, the flavonoid may be a polymethoxyflavone, which is a flavone.

Examples of polymethoxyflavones include sudachitin, demethoxysudachitin, nobiletin, tangeretin, pentamethoxyflavone, tetramethoxyflavone, heptamethoxyflavone, etc. Among these, the polymethoxyflavone may be sudachitin or demethoxysudachitin.

The sugars that serve as the basis for flavonoid glycosides are not particularly limited, and include known sugars that can be linked to the above-mentioned flavonoids via a glycosidic bond to form glycosides.

The raw material liquid to be subjected to hydrothermal treatment is a solution or dispersion of a raw material containing flavonoid glycosides in water. The raw material may contain other components in addition to flavonoid glycosides. Examples of other components include flavonoids, water-soluble dietary fiber, sparingly soluble dietary fiber, sugars, etc.

The content of flavonoid glycoside in the raw material is preferably 0.1% by mass or more, more preferably 0.25 to 30% by mass, and even more preferably 0.5 to 5% by mass, based on the total solid content of the raw material. When the raw material further contains a flavonoid, the content of flavonoid glycoside is preferably 0.25 parts by mass or more, more preferably 0.5 to 100 parts by mass, and even more preferably 5 to 50 parts by mass, per part by mass of the flavonoid content.

The concentration of the raw material in the raw material solution is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 10% by mass, based on the total amount of the raw material solution. If the concentration of the raw material is 1% by mass or more, the yield of the decomposition product increases, and therefore the amount of flavonoid obtained in one decomposition process tends to increase, while if it is 30% by mass or less, the decomposition of flavonoid glycosides tends to be more reliable and efficient.

Specific examples of the raw material that can be used include flowers, leaves, roots, stems, fruits, seeds, etc. of plants and seaweed. In particular, the peel contains a large amount of polymethoxyflavones and their glycosides, so the squeezed residue of citrus fruits can be suitably used. The raw material may be a dried powder obtained from citrus fruits, or a dried powder obtained from citrus peels. Examples of citrus fruits include sudachi, unshu mandarin oranges, ponkan, and shikuwasa. The citrus fruit may be sudachi, which contains a large amount of polymethoxyflavones such as sudachitin and demethoxysudachitin, and their glycosides.

The hydrothermal treatment can be carried out by placing a raw material container containing the raw material liquid in an autoclave and heating the autoclave at a temperature exceeding 100°C while keeping the autoclave sealed. By heating the raw material liquid in the autoclave, the inside of the autoclave becomes a heated and pressurized environment, and the hydrothermal treatment (hydrothermal synthesis) is carried out. The hydrothermal treatment may be carried out while stirring the raw material liquid.

Hydrothermal treatment may also be performed by supplying water vapor from the outside into the autoclave. For example, by supplying high-temperature, high-pressure saturated water vapor into the autoclave, the inside of the autoclave becomes a heated and pressurized environment, and hydrothermal treatment (hydrothermal synthesis) is performed. There are no particular limitations on the autoclave, and it may be either vertical or horizontal. When using a vertical autoclave, a raw material container containing the raw material liquid may be placed on a stand. When using a vertical autoclave, water may be placed in the autoclave tank separately from the raw material liquid. On the other hand, when using a horizontal autoclave, hydrothermal treatment can be performed, for example, by the following method.

Figure 1 is a schematic cross-sectional view showing an example of an autoclave (horizontal circulation autoclave) used in the above-mentioned decomposition method. In the autoclave 100 shown in Figure 1, a cylindrical muffle furnace 3 with both ends open is placed in a cylindrical pressure vessel (tank) 2 with a sealable door (sealing door) 1 at one end, and an air passage 4 is formed between the inner wall of the pressure vessel 2 and the outer wall of the muffle furnace 3. In addition, one end of the muffle furnace 3 is connected to a circulation fan 8 via a cooler 6, a heater 5, and an air passage 9. The circulation fan 8 is attached to the rotating shaft of a motor 7 placed outside the end of the pressure vessel 2 opposite the sealing door 1.

A movable table 12 is placed inside the muffle furnace 3, and a raw material container 11 containing raw material liquid 10 is placed on the movable table 12. A boiler 13 for supplying steam is connected to the pressure vessel 2 via a pipe equipped with a valve 14. In addition, a pipe equipped with a pressure gauge 15 and a pressure valve 16 for adjusting the internal pressure is connected to the pressure vessel 2.

In the hydrothermal treatment process, the steam supplied from the boiler 13 to the pressure vessel 2 circulates in the autoclave 100 along the arrows in FIG. 1. That is, the steam is sent to the air passage 4 by the circulation fan 8 and heads toward the airtight door 1, then flows into the muffle furnace 3, flows around the raw material container 11, passes through the cooler 6, the heater 5, and the air passage 9, is sucked into the circulation fan 8, and is sent out again to the air passage 4. The amount of steam supplied is adjusted by operating the valve 14 so that the temperature and pressure inside the autoclave 100 are set to a predetermined value. The temperature inside the autoclave 100 may be adjusted by the heater 5 and the cooler 6. The pressure inside the autoclave 100 may be adjusted by opening and closing the pressure valve 16. By the above operation, the inside of the autoclave 100 becomes a heated and pressurized environment, and hydrothermal treatment (hydrothermal synthesis) is performed.

The raw material container 11 has a contact surface 20 with the raw material liquid 10. The contact surface 20 is the surface of the inner surface of the raw material container 11 that comes into contact with the raw material liquid 10. The contact surface 20 is a surface that has a contact angle with water of less than 35° at a measurement temperature of 25°C. The entire inner surface of the raw material container 11 may be a surface that has a contact angle with water of less than 35° at a measurement temperature of 25°C. The contact angle of the outer surface of the raw material container 11 with water at a measurement temperature of 25°C is not particularly limited.

The contact angle of the contact surface 20 with water at a measurement temperature of 25°C is less than 35°, which further suppresses adhesion of glycoside decomposition products to the contact surface 20 and further improves the yield of flavonoids even when the time required to remove the glycoside decomposition products is short, and is therefore preferably less than 15°, and more preferably less than 5°. The contact angle of the contact surface 20 with water at a measurement temperature of 25°C may be 0.01° or more.

The contact angle with water at a measurement temperature of 25°C refers to a value measured as follows. That is, it is measured using a contact angle meter in an environment at a temperature of 25°C. The contact angle is measured five times using water on the contact surface with the raw material liquid 10 in the raw material container 11, and the average value is taken as the contact angle. For example, ultrapure water can be used as the water.

The material of the raw material container 11 is not particularly limited as long as it can withstand the temperature and pressure during hydrothermal treatment and causes minimal impurities to be mixed into the raw material liquid 10. For example, metals such as stainless steel, titanium and its alloys, or chemically stable and heat-resistant resins such as polytetrafluoroethylene, polyimide and polyamideimide can be used.

The shape of the raw material container 11 is not particularly limited, but may be, for example, tank-shaped, bottle-shaped, cup-shaped, tray-shaped, or drum-shaped.

The surface of the raw material container 11 that comes into contact with the raw material liquid 10 is preferably a surface that has been hydrophilized. Examples of hydrophilization treatments include enamel treatment, treatment with a polysilazane compound, treatment with an alkoxysilane compound, and plasma treatment with oxygen, nitrogen, etc. The hydrophilization treatment is preferably enamel treatment or treatment with a polysilazane compound, since this further suppresses adhesion of glycoside decomposition products to the contact surface 20 and further improves the yield of flavonoids even when the time required to remove the glycoside decomposition products is short.

Examples of polysilazane compounds include perhydropolysilazane. The polysilazane compound is preferably perhydropolysilazane, since this further suppresses adhesion of the glycoside decomposition products to the contact surface 20 and further improves the yield of flavonoids even when the time required to remove the glycoside decomposition products is short.

The reaction conditions for the hydrothermal treatment are not particularly limited, but can be, for example, 110 to 300°C and 0.5 to 20 hours. The reaction temperature is preferably 120 to 200°C, more preferably 120 to 190°C, and even more preferably 140 to 185°C. If the reaction temperature is 110°C or higher, the hydrothermal reaction tends to occur more easily, and if it is 300°C or lower, carbonization of the raw materials and flavonoids tends not to progress, and the yield tends to be improved. The reaction time is preferably 0.5 to 20 hours, and more preferably 1 to 10 hours. If the reaction time is 0.5 hours or more, the reaction tends to proceed more easily, and if it is 20 hours or less, it tends to be easier to balance the progress of the reaction and the cost.

The pressure inside the autoclave during hydrothermal treatment may be equal to or higher than the saturated vapor pressure corresponding to the above-mentioned reaction temperature, but from the viewpoint of the pressure resistance of the device, it is preferable that it be saturated vapor pressure. When supplying steam from a boiler into the autoclave, it is preferable to supply saturated steam at the above-mentioned reaction temperature. The pressure inside the autoclave during hydrothermal treatment can be, for example, 0.2 to 1.6 MPa.

By performing hydrothermal treatment under the above conditions, flavonoid glycosides can be efficiently decomposed into flavonoids (more specifically, into flavonoids and sugars).

Next, after carrying out the hydrothermal treatment process by the above-mentioned method, a decompression process may be carried out to reduce the pressure inside the autoclave. The pressure inside the autoclave may be reduced by opening the pressure valve and discharging the water vapor inside the autoclave. The decompression speed during decompression may be adjusted by the pressure valve. It is preferable to carry out the decompression while checking the pressure inside the autoclave with a pressure gauge. The decompression speed in the decompression process is not particularly limited, but may be, for example, 140 kPa/min or less. The decompression speed in the decompression process is not particularly limited, but may be, for example, 5 kPa/min or more. Note that in the decompression process, the decompression speed does not need to be constant at all times, and may be varied.

After the pressure inside the autoclave is reduced to atmospheric pressure (0.1 MPa) by the above-mentioned decompression process, the raw material liquid can be cooled to room temperature by natural cooling. This allows the decomposition products of flavonoid glycosides (glycoside decomposition products) to be obtained.

(Method of producing flavonoids)
The method for producing a flavonoid according to the present embodiment includes a decomposition step of decomposing a flavonoid glycoside and an extraction step of extracting a flavonoid from the decomposition product obtained in the decomposition step. The decomposition step is a step of decomposing a flavonoid glycoside by the above-mentioned method for decomposing a flavonoid glycoside according to the present embodiment.

In the extraction step, flavonoids are extracted from the decomposition products obtained in the decomposition step. In addition to flavonoids, the decomposition products contain sugars, flavonoid glycosides that remain undecomposed, water-soluble and poorly soluble cellulose, and decomposition products thereof. Here, flavonoids are hydrophobic, whereas sugars, flavonoid glycosides, water-soluble cellulose, and decomposition products thereof are hydrophilic. Therefore, the components that are insoluble in the aqueous solution after the hydrothermal treatment contain flavonoids at high concentrations, and the flavonoids can be concentrated by separating the aqueous solution and the insoluble matter after the hydrothermal treatment. In addition, the water-insoluble matter can be further dissolved in a solvent that dissolves flavonoids, such as ethanol, ethyl acetate, hexane, toluene, etc., and a mixed solvent thereof, and the insoluble matter can be removed by filtration or the like, thereby further extracting and purifying the flavonoids. Thereafter, the filtrate is dried to obtain a high concentration of flavonoids.

The above method allows flavonoids to be produced efficiently with a high yield. The flavonoid produced by the production method of this embodiment may be polymethoxyflavones, or may be sudachitin and/or demethoxysudachitin. The production method of this embodiment is suitable for producing polymethoxyflavones, particularly sudachitin and demethoxysudachitin, and can greatly improve the yield.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment. For example, the autoclave 100 shown in FIG. 1 is equipped with one circulation fan 8, but an autoclave equipped with multiple circulation fans may be used. For example, when circulation fans are installed at multiple locations in the muffle furnace 3, it is easy to make the temperature in the muffle furnace 3 uniform. Therefore, even if multiple raw material containers containing raw material liquids are placed in the autoclave, the temperature of each raw material liquid is likely to be uniform. In addition, the autoclave 100 shown in FIG. 1 is equipped with a cooler 6 and a heater 5, but one or both of them may not be equipped.

The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
Sudachi peel extract powder (manufactured by Ikeda Yakuso Co., Ltd.) with a sudachitin content of 1000 ppm by mass and a glycoside-derived sudachitin content of 9000 ppm by mass was dissolved/dispersed in ultrapure water to a concentration of 5% by mass to prepare a sudachi peel extract aqueous dispersion. 12 L of this aqueous dispersion was placed in a container. As the container, an 18.5 L enamel tank (manufactured by Noda Enamel) was used. The enamel tank is an iron tank whose entire inner surface is enameled. Next, the sudachi peel extract aqueous dispersion was placed in a hot air circulation autoclave (manufactured by Ashida Manufacturing Co., Ltd.) with a tank volume of 2 ^m3 , and subjected to glycoside decomposition treatment at 180°C for 1 hour. The decomposition treatment was performed by supplying saturated steam at 180°C from a boiler into the autoclave tank (pressure vessel), and adjusting the amount of steam supplied and the pressure valve so that the pressure inside the tank was 1 MPa, which is the saturated steam pressure of water at 180°C. The pressure in the tank after the decomposition treatment was 0.9 MPa, and the temperature in the tank was 180 ° C. The autoclave was naturally cooled for 10 minutes until the pressure in the tank was 0.7 MPa and the temperature in the tank was 165 ° C. After natural cooling, the valve was opened, and compressed air at a pressure of 1 MPa was sent into the tank using a compressor attached to the device. Since the pressure in the tank immediately after sending in the compressed air exceeded 1 MPa, compressed air was introduced into the tank while maintaining a pressure not lower than 0.75 MPa by manually opening and closing the exhaust valve, and cooling with compressed air was started. During cooling, cooling was performed while appropriately lowering the pressure in the tank so as not to fall below the saturated water vapor pressure at that time. Two hours after the start of cooling with compressed air, the temperature of the aqueous dispersion fell below 100 ° C. (the saturated water vapor pressure of the aqueous dispersion fell below normal pressure (0.1 MPa)), so the lid of the tank was opened, the container was removed, and the tank was naturally cooled to normal temperature (25 ° C.). After cooling, the glycoside decomposition products that had precipitated and adhered to the inner surface of the container were removed using a medicine spoon for 5 minutes. The yield of the removed glycoside decomposition products is shown in Table 1.

Next, the solution and solids in the container were filtered under reduced pressure using a hydrophilic PTFE membrane filter with 0.2 μm openings (Omnipore 0.2 μm JG (Merck Millipore, product name)) with a diaphragm pump. The separated solution contained dissolved sugars derived from the decomposed glycosides, and the solids contained a high concentration of decomposed sudachitin. The solids were placed in a 200 cc glass beaker and dried in an oven at 120°C for 5 hours to obtain a powdered glycoside decomposition product. The glycoside decomposition product was then adjusted to a 5% dispersion in ethanol and treated under reflux at 60°C for 1 hour to extract sudachitin into ethanol, which was then filtered under reduced pressure using a hydrophilic PTFE membrane filter with 0.2 μm openings (Omnipore 0.2 μm JG (Merck Millipore, product name)) with a diaphragm pump to obtain a sudachitin solution. The obtained sudachitin solution was dried in vacuum using a diaphragm pump while heating at 60° C. to obtain a powdered sudachitin concentrate.

Example 2
A powdered sudachitin concentrated powder was obtained in the same manner as in Example 1, except that a hydrophilically treated stainless steel tank was used as a container instead of a 18.5 L enamel tank. The hydrophilically treated stainless steel tank was obtained by spraying 2% solids of perhydropolysilazane onto the entire inner surface of a 15 L stainless steel tank (manufactured by Nitto Metal Industries Co., Ltd., container depth: 27 cm) and then baking the same at 140° C. for 1 hour.

(Comparative Example 1)
A powdered sudachitin concentrate was obtained in the same manner as in Example 1, except that a 15 L stainless steel tank (manufactured by Nitto Metal Industries Co., Ltd., container depth: 27 cm) was used instead of the 18.5 L enamel tank as the container.

<Evaluation method>
(Measurement of Sudachitin concentration in Sudachitin concentrated powder)
The sudachitin concentration of the sudachitin concentrated powder obtained in each Example and Comparative Example was measured by the following method. First, 0.1 g of sudachitin concentrated powder was dissolved/dispersed in ethanol to a dilution ratio of 500, and filtered through a PTFE filter with a pore size of 0.1 μm to obtain an ethanol solution. This ethanol solution was subjected to component analysis by high performance liquid chromatography (HPLC). A calibration curve was created using a commercially available sudachitin standard purified sample as the standard substance, and the sudachitin concentration in the sudachitin concentrated powder was estimated using this. The HPLC device used was a "Chrome Master" manufactured by Hitachi High-Tech. The results are shown in Table 1.

(Calculation of Sudachitin Yield)
The yield of sudachitin was calculated from the mass and concentration of the concentrated sudachitin powder. The yield indicates the ratio of the mass of sudachitin contained in the concentrated sudachitin powder to the total mass of sudachitin and glycoside-derived sudachitin contained in the aqueous dispersion placed in the raw material container.

<Contact angle measurement>
The contact angle with water at a measurement temperature of 25°C was measured in an environment with a humidity of 40% RH using a contact angle meter DM-501 manufactured by Kyowa Interface Science Co., Ltd. The contact angle was measured five times for each surface of the raw material container in contact with the raw material liquid, and the average value was obtained as the contact angle. The amount of water dropped was 1 μl, and the contact angle was read after leaving it to stand for 3 seconds. As the water, ultrapure water (electrical resistivity: 18 MΩ cm or more) taken from an ultrapure water production apparatus (PRO-0500 (model number), manufactured by Organo Corporation) was used. The results are shown in Table 1.

The sudachitin concentration in the sudachitin concentrated powder obtained in the examples and comparative examples all exceeded 9% by mass, confirming that the glycoside decomposition process was performed properly. In examples 1 and 2, in which the contact angle of the surface of the raw material container that comes into contact with the raw material liquid is less than 35°, the yield exceeded 80% by mass, and glycoside decomposition products were efficiently recovered.

According to the method for decomposing flavonoid glycosides of the present invention, flavonoid glycosides can be efficiently decomposed into flavonoids without using acid, thereby improving the yield of flavonoids.

1...sealing door, 2...pressure vessel, 3...muffle furnace, 4...air duct, 5...heater, 6...cooler, 7...motor, 8...circulating fan, 9...air duct, 10...raw material liquid, 11...raw material vessel, 12...movable platform, 13...boiler, 14...valve, 15...pressure gauge, 16...pressure valve, 20...contact surface.

Claims (9)

a hydrothermal treatment step of disposing a raw material container containing a raw material solution containing a raw material containing a flavonoid glycoside in an autoclave, and hydrothermally treating the raw material solution to decompose the flavonoid glycoside into a flavonoid,
a concentration of the raw material in the raw material liquid is 1 to 30 mass % based on the total amount of the raw material liquid;
A method for decomposing a flavonoid glycoside, wherein the surface of the raw material container that comes into contact with the raw material liquid has a contact angle with water of less than 35° at a measurement temperature of 25°C. The disassembly method according to claim 1, wherein the contact surface is an enameled surface. The decomposition method according to claim 1, wherein the contact surface is a surface that has been treated with a polysilazane compound. The decomposition method according to claim 3, wherein the polysilazane compound is perhydropolysilazane. The decomposition method according to any one of claims 1 to 4, further comprising a decompression step of reducing the pressure inside the autoclave after the hydrothermal treatment step. The decomposition method according to any one of claims 1 to 5, wherein the hydrothermal treatment is carried out by supplying water vapor from outside into the autoclave. The decomposition method according to any one of claims 1 to 6, wherein in the hydrothermal treatment step, the pressure inside the autoclave is 0.2 to 1.6 MPa and the temperature is 120 to 200°C. The method according to any one of claims 1 to 7, wherein the flavonoid glycoside comprises sudachitin glycoside and/or demethoxysudachitin glycoside. A decomposition step of decomposing a flavonoid glycoside by the method according to any one of claims 1 to 8;
An extraction step of extracting flavonoids from the decomposition product obtained in the decomposition step;
A method for producing a flavonoid, comprising:

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