Method for decomposing flavonoid glycoside and method for producing flavonoid

Abstract

This method for breaking down flavonoid glycoside includes a hydrothermal treatment step for placing a starting material container that contains a starting material liquid including a flavonoid glycoside in an autoclave, and hydrothermally treating the starting material liquid to break down the flavonoid glycoside into flavonoids. The water contact angle of the surface of the starting material container that comes into contact with the starting material liquid is less than 35° when the measuring temperature is 25°C.

Description

Technical Field

[0001] The present invention relates to a method for decomposing flavonoid glycosides and a method for producing flavonoids.

Background Art

[0002] Flavonoids are a group of naturally occurring organic compounds and are contained in various parts of plants such as flowers, leaves, roots, stems, fruits, and seeds of various plants including citrus fruits and beans. Although flavonoids have different characteristics and effects depending on their types, many of them have a strong antioxidant effect. For example, polymethoxyflavone, a flavonoid contained in citrus fruits, is known to have antioxidant, carcinogenesis inhibitory, antibacterial, antiviral, anti-allergic, melanin production inhibitory, blood glucose level inhibitory effects, etc., and is expected to be applied to various uses such as pharmaceuticals, health foods, and cosmetics.

[0003] As a method for producing flavonoids from citrus fruits, for example, a method of extracting flavonoids from citrus fruit peels or the like with an aqueous ethanol solution and recovering the extracted flavonoids from the solution is known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventional methods for producing flavonoids have a problem that the yield of flavonoids is low. Therefore, development of a production method capable of improving the yield of flavonoids is required.

[0006] For example, in addition to flavonoids, citrus peels contain a larger amount of flavonoid glycosides. If these can be recovered as flavonoids, it is possible to improve the yield of flavonoids. As a method for decomposing flavonoid glycosides into flavonoids, a method of reacting flavonoid glycosides with an acid such as hydrochloric acid can be mentioned. However, in this method, there is a problem that the acid used may remain and mix into the product, and there is also a risk of generating side reaction products between the acid and the flavonoid. As a method for removing impurities such as acids and by-products, a method of separating and purifying the flavonoids in the decomposition product by liquid chromatography can be mentioned, but there are problems of high cost and poor production efficiency. Therefore, a new method for decomposing flavonoid glycosides without using an acid is required.

[0007] The present invention has been made in view of the problems of the above prior art, and an object thereof is to provide a method for decomposing flavonoid glycosides that can efficiently decompose flavonoid glycosides into flavonoids without using an acid and can improve the yield of flavonoids, and a method for producing flavonoids.

Means for Solving the Problems

[0008] In order to achieve the above object, the present invention has a hydrothermal treatment step of disposing a raw material container containing a raw material liquid containing flavonoid glycosides in an autoclave and subjecting the raw material liquid to hydrothermal treatment to decompose the flavonoid glycosides into flavonoids, and the contact surface of the raw material container with the raw material liquid is a surface having a contact angle with water at a measurement temperature of 25 °C of less than 35 °C, and provides a method for decomposing flavonoid glycosides.

[0009] According to the above method, flavonoid glycosides can be efficiently decomposed into flavonoids by hydrothermal treatment without using an acid. Further, by using this method, it becomes possible to produce flavonoids efficiently at low cost.

[0010] Further, the present inventors have found that in a method for decomposing flavonoid glycosides by hydrothermal treatment, a phenomenon occurs in which glycoside decomposition products precipitate after hydrothermal treatment and the glycoside decomposition products adhere to the contact surface with the raw material liquid in the raw material container. The glycoside decomposition products include flavonoids obtained by decomposing glycosides, caramel reaction products of the generated sugars, and the like. When a stainless steel container or a container made of polytetrafluoroethylene resin, which is common as a raw material container, is used as it is, deposits strongly adhere to the contact surface with the raw material liquid in the raw material container. Therefore, in order to take out these deposits, it is necessary to strongly rub the contact surface with a spoon or the like for a long time, which takes a long time to take out the glycoside decomposition products. Further, in order to strongly rub the contact surface with the raw material liquid in the raw material container with a spoon or the like, the contact surface or the spoon or the like may be worn out, and there is a risk of contamination with foreign substances. As a result of intensive studies to solve these problems, the present inventors have found that when the contact surface with the raw material liquid in the raw material container is a surface having a contact angle with respect to water at a measurement temperature of 25 °C of less than 35°, the adhesion of the glycoside decomposition products to the contact surface can be suppressed, and even when the extraction time of the glycoside decomposition products is short, the yield of flavonoids can be improved. The present inventors speculate as follows about the fact that the adhesion of the glycoside decomposition products to the contact surface can be suppressed when the contact surface with the raw material liquid in the raw material container is a surface having a contact angle with respect to water at a measurement temperature of 25 °C of less than 35°. That is, the glycoside decomposition products are hydrophobic. On the other hand, the contact surface with the raw material liquid in the raw material container has a contact angle with respect to water at a measurement temperature of 25 °C of less than 35° and is hydrophilic. Therefore, the hydrophobic glycoside decomposition products and the contact surface with respect to the hydrophilic raw material liquid repel each other. As a result, the precipitated glycoside decomposition products are less likely to adhere to the contact surface in the raw material container.

[0011] In the above decomposition method, the contact surface may be a surface subjected to honing treatment. By making the contact surface a surface subjected to honing treatment, the contact angle with respect to water at a measurement temperature of 25 °C of the contact surface can be further reduced, and the deposited glycoside decomposition products are less likely to adhere to the raw material container.

[0012] In the above decomposition method, the contact surface may be a surface treated with a polysilazane compound. By the contact surface being a surface treated with a polysilazane compound, the contact angle with respect to water at the measurement temperature of 25°C of the contact surface can be further reduced, and the deposited glycoside decomposition product becomes less likely to adhere to the raw material container.

[0013] The above polysilazane compound may be perhydropolysilazane. By the polysilazane compound being perhydropolysilazane, the contact angle with respect to water at the measurement temperature of 25°C of the contact surface can be further reduced, and the deposited glycoside decomposition product becomes less likely to adhere to the raw material container.

[0014] 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 increased in a short time, and the hydrothermal treatment environment can be easily formed and maintained.

[0015] In the hydrothermal treatment step of the above 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 performing hydrothermal treatment within the above pressure and temperature ranges, flavonoid glycosides can be more efficiently decomposed into flavonoids, and the yield of flavonoids can be further improved.

[0016] In the above decomposition method, the flavonoid glycoside may contain sudachitin glycoside and / or demethoxysudachitin glycoside. According to the above decomposition method, sudachitin glycoside and demethoxysudachitin glycoside can be decomposed particularly efficiently.

[0017] The present invention also provides a method for producing a flavonoid, including a decomposition step of decomposing a flavonoid glycoside by the above decomposition method of the present invention, and an extraction step of extracting a flavonoid from the decomposition product obtained in the above decomposition step. According to such a production method, a flavonoid can be produced at a high yield, at low cost and efficiently.

Advantages of the Invention

[0018] According to the present invention, it is possible to provide a method for decomposing a flavonoid glycoside into a flavonoid efficiently without using an acid, and to improve the yield of the flavonoid, and a method for producing a flavonoid.

Brief Description of the Drawings

[0019]

Figure 1

Embodiments for Carrying Out the Invention

[0020] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments. Also, the dimensional ratios in the drawings are not limited to the ratios shown.

[0021] In this specification, a numerical range indicated using “~” indicates a range including the numerical values described before and after “~” as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in this specification, the upper limit value or the lower limit value of a numerical range at a certain step can be arbitrarily combined with the upper limit value or the lower limit value of a numerical range at another step. In the numerical ranges described in this specification, the upper limit value or the lower limit value of the numerical range may be replaced with the values shown in the examples. “A or B” means that either one of A and B may be included, or both may be included. The materials exemplified in this specification can be used alone or in combination of two or more without particular notice.

[0022] (Method for Decomposing Flavonoid Glycoside) The method for decomposing flavonoid glycosides according to this embodiment has a hydrothermal treatment step of placing a raw material container containing a raw material liquid containing flavonoid glycosides in an autoclave and subjecting the raw material liquid to hydrothermal treatment to decompose the flavonoid glycosides into flavonoids. The contact surface of the raw material container with the raw material liquid is a surface with a contact angle with respect to water of less than 35° at a measurement temperature of 25°C.

[0023] Flavonoid glycosides are hydrophilic compounds having a structure in which a flavonoid and a sugar are bonded by a glycosidic bond. The flavonoid that is the source of the flavonoid glycoside is an aromatic compound having a phenylchroman skeleton as a basic structure, and examples include flavones, flavonols, flavanones, flavanonols, isoflavones, anthocyanins, flavanols, chalcones, aurones, etc. Among these, the flavonoid may be polymethoxyflavone which is a flavone.

[0024] Examples of polymethoxyflavones include sudachitin, demethoxysudachitin, nobilitin, tangeretin, pentamethoxyflavone, tetramethoxyflavone, heptamethoxyflavone, etc. Among these, the polymethoxyflavone may be sudachitin or demethoxysudachitin.

[0025] The sugar that is the source of the flavonoid glycoside is not particularly limited, and examples include known sugars that can be bonded to the above-mentioned flavonoid by a glycosidic bond to form a glycoside.

[0026] The raw material liquid to be subjected to hydrothermal treatment is obtained by dissolving or dispersing a raw material containing flavonoid glycosides in water. The raw material may contain other components other than flavonoid glycosides. Examples of other components include flavonoids, water-soluble dietary fiber, insoluble dietary fiber, saccharides, etc.

[0027] The content of flavonoid glycosides in the raw material is preferably 0.1% by mass or more, more preferably 0.25 - 30% by mass, and still more preferably 0.5 - 5% by mass, based on the total solid content of the raw material. When the raw material further contains flavonoids, the content of flavonoid glycosides is preferably 0.25 parts by mass or more, more preferably 0.5 - 100 parts by mass, and still more preferably 5 - 50 parts by mass, per 1 part by mass of the flavonoid content.

[0028] The concentration of the raw material in the raw material liquid is preferably 1 - 30% by mass, more preferably 3 - 20% by mass, and still more preferably 5 - 10% by mass, based on the total amount of the raw material liquid. When the concentration of the raw material is 1% by mass or more, the yield of decomposition products increases, so the amount of flavonoids obtained by one decomposition treatment tends to increase. When it is 30% by mass or less, the decomposition of flavonoid glycosides can tend to be carried out more reliably and efficiently.

[0029] Specifically, as the raw material, flowers, leaves, roots, stems, fruits, seeds, etc. of plants and seaweeds can be used. In particular, since the pericarp contains a large amount of polymethoxyflavones and their glycosides, the juice extraction residue of citrus fruits can be preferably used. Also, the raw material may be a dry powder obtained from citrus fruits, or a dry powder obtained from the pericarp of citrus fruits. Examples of citrus fruits include sudachi, satsuma mandarin, ponkan, and calamansi. The citrus fruit may be sudachi, which contains a large amount of polymethoxyflavones such as sudachitin and demethoxysudachitin, and their glycosides.

[0030] The hydrothermal treatment can be carried out by placing a raw material container containing the raw material liquid in an autoclave and heating it at a temperature exceeding 100°C while keeping the autoclave sealed. When the above raw material liquid is heated in the autoclave, the inside of the autoclave becomes a heating and pressurizing environment, and the hydrothermal treatment (hydrothermal synthesis) is carried out. The hydrothermal treatment may be carried out while stirring the raw material liquid.

[0031] Alternatively, the hydrothermal treatment may be performed by supplying water vapor from the outside into the autoclave. For example, by supplying high-temperature and high-pressure saturated water vapor into the autoclave, the inside of the autoclave becomes a heating and pressurizing environment, and the hydrothermal treatment (hydrothermal synthesis) is carried out. The autoclave is not particularly limited, and it may be either vertical or horizontal. When using a vertical autoclave, the raw material container containing the raw material liquid may be placed on a table. When using a vertical autoclave, water may be put into the tank of the autoclave separately from the raw material liquid. On the other hand, when using a horizontal autoclave, the hydrothermal treatment can be carried out, for example, by the following method.

[0032] Figure 1 is a schematic cross-sectional view showing an example of the autoclave (horizontal circulation type autoclave) used in the above decomposition method. In the autoclave 100 shown in Figure 1, a cylindrical muffler furnace 3 with both ends open is arranged inside a cylindrical pressure vessel (tank) 2 having a door (sealing door) 1 that can be sealed 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 muffler furnace 3. One end of the muffler 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 arranged outside the end of the pressure vessel 2 opposite to the sealing door 1.

[0033] A movable table 12 is arranged inside the muffler furnace 3, and a raw material container 11 containing the raw material liquid 10 is placed on the movable table 12. A boiler 13 for supplying water vapor is connected to the pressure vessel 2 via a pipe provided with a valve 14. In addition, a pipe equipped with a pressure gauge 15 and a pressure valve 16 is connected to the pressure vessel 2 to adjust the internal pressure.

[0034] In the hydrothermal treatment process, the steam supplied from the boiler 13 into the pressure vessel 2 circulates inside the autoclave 100 along the arrow in Fig. 1. That is, the steam is sent out by the circulation fan 8 into the air duct 4 and heads towards the sealed door 1, then flows into the muffle furnace 3, flows around the raw material container 11, is sucked by the circulation fan 8 through the cooler 6, the heater 5 and the air duct 9, and is sent out into the air duct 4 again. The supply amount of the steam is adjusted by operating the valve 14 so that the inside of the autoclave 100 reaches a predetermined temperature and pressure. Note that the temperature inside the autoclave 100 may be adjustable by the heater 5 and the cooler 6. Also, the pressure inside the autoclave 100 may be adjusted by opening and closing the pressure valve 16. Through the above operations, the inside of the autoclave 100 becomes a heating and pressurizing environment, and hydrothermal treatment (hydrothermal synthesis) is performed.

[0035] The raw material container 11 is provided with 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 contacts the raw material liquid 10. The contact surface 20 is a surface with a contact angle with respect to water at a measured temperature of 25°C of less than 35°. The entire inner surface of the raw material container 11 may be a surface with a contact angle with respect to water at a measured temperature of 25°C of less than 35°. The contact angle of the outer surface of the raw material container 11 with respect to water at a measured temperature of 25°C is not particularly limited.

[0036] The contact angle of the contact surface 20 with respect to water at a measured temperature of 25°C is less than 35°, further suppressing the adhesion of the glycoside decomposition product to the contact surface 20, and even when the extraction time of the glycoside decomposition product is short, the yield of flavonoid can be further improved. Therefore, it is preferably less than 15°, and more preferably less than 5°. The contact angle of the contact surface 20 with respect to water at a measured temperature of 25°C may be 0.01° or more.

[0037] The contact angle with respect to water at a measured temperature of 25°C refers to the value measured as follows. That is, in an environment at a temperature of 25°C, it is measured using a contact angle meter. For the contact surface of the raw material container 11 with the raw material liquid 10, the contact angle is measured 5 times with water, and the average value is taken as the contact angle. As the water, for example, ultrapure water can be used.

[0038] The material of the raw material container 11 is not particularly limited as long as it can withstand the temperature and pressure during the hydrothermal treatment and has little impurity mixing into the raw material liquid 10. For example, metals such as stainless steel, titanium, and their alloys, or chemically stable and highly heat-resistant resins such as polytetrafluoroethylene, polyimide, and polyamideimide can be used.

[0039] The shape of the raw material container 11 is not particularly limited, and for example, it may be tank-shaped, bottle-shaped, cup-shaped, tray-shaped, or drum-shaped, etc.

[0040] The contact surface of the raw material container 11 with the raw material liquid 10 is preferably a surface that has been hydrophilized. Examples of the hydrophilization treatment include corona treatment, treatment with a polysilazane compound, treatment with an alkoxysilane compound, plasma treatment with oxygen, nitrogen, etc. Since the adhesion of the glycoside decomposition product to the contact surface 20 can be further suppressed and the yield of flavonoids can be further improved even when the extraction time of the glycoside decomposition product is short, the hydrophilization treatment is preferably corona treatment or treatment with a polysilazane compound.

[0041] Examples of the polysilazane compound include perhydropolysilazane. Since the adhesion of the glycoside decomposition product to the contact surface 20 can be further suppressed and the yield of flavonoids can be further improved even when the extraction time of the glycoside decomposition product is short, the polysilazane compound is preferably perhydropolysilazane.

[0042] The reaction conditions for the hydrothermal treatment are not particularly limited. For example, the temperature can be 110 to 300 °C and the time can be 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. When the reaction temperature is 110 °C or higher, the hydrothermal reaction tends to occur more favorably. When it is 300 °C or lower, the carbonization of the raw material and flavonoid is less likely to proceed, and the yield tends to be further improved. The reaction time is preferably 0.5 to 20 hours, and more preferably 1 to 10 hours. When the reaction time is 0.5 hours or longer, the reaction tends to proceed more easily. When it is 20 hours or shorter, the balance between the progress of the reaction and the cost tends to be easier to achieve.

[0043] The pressure inside the autoclave during the hydrothermal treatment may be the saturated vapor pressure corresponding to the above reaction temperature or higher, but from the perspective of the pressure resistance of the apparatus, it is preferably the saturated vapor pressure. When supplying steam from the boiler into the autoclave, it is preferable to supply the saturated steam at the above-mentioned reaction temperature. The pressure inside the autoclave during the hydrothermal treatment can be, for example, 0.2 to 1.6 MPa.

[0044] By performing the hydrothermal treatment under the above conditions, flavonoid glycosides can be efficiently decomposed into flavonoids (more specifically, flavonoids and sugars).

[0045] Next, after performing the hydrothermal treatment step by the above-described method, a depressurization step of depressurizing the pressure inside the autoclave may be performed. The depressurization inside the autoclave can be performed by opening the pressure valve to discharge the steam inside the autoclave. The depressurization rate during depressurization can be adjusted with the pressure valve. Depressurization is preferably performed while confirming the pressure inside the autoclave with a pressure gauge. The depressurization rate in the depressurization step is not particularly limited, but can be, for example, 140 kPa / min or less. The depressurization rate in the depressurization step is not particularly limited, but can be, for example, 5 kPa / min or more. Note that in the depressurization step, the depressurization rate does not necessarily have to be constant all the time, and the depressurization rate may be varied.

[0046] After the autoclave is depressurized to atmospheric pressure (0.1 MPa) in the above-described depressurization step, the raw material solution can be cooled to room temperature by natural cooling. Thereby, decomposition products (glycoside decomposition products) of flavonoid glycosides can be obtained.

[0047] (Method for producing flavonoid) 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 products obtained in the decomposition step. The decomposition step is a step of decomposing a flavonoid glycoside by the method for decomposing a flavonoid glycoside according to the present embodiment described above.

[0048] In the extraction step, a flavonoid is extracted from the decomposition products obtained in the decomposition step. The decomposition products contain, in addition to the flavonoid, sugar, flavonoid glycosides remaining undecomposed, water-soluble and water-insoluble cellulose, and decomposition products thereof. Here, while the flavonoid is hydrophobic, the sugar, flavonoid glycoside, water-soluble cellulose, and its decomposition product are hydrophilic. Therefore, the component insoluble in the aqueous solution after the hydrothermal treatment contains a high concentration of flavonoid, and the flavonoid can be concentrated by separating the aqueous solution and the insoluble component after the hydrothermal treatment. Further, the water-insoluble component is dissolved in a solvent that dissolves the flavonoid, such as ethanol, ethyl acetate, hexane, toluene, etc., and a mixed solvent thereof, and the insoluble matter is removed by filtration or the like, whereby the flavonoid can be further extracted and purified. Thereafter, a high-concentration flavonoid can be obtained by drying the filtrate.

[0049] By the above method, a flavonoid can be efficiently produced in a high yield. The flavonoid produced by the production method of the present embodiment may be polymethoxyflavone, or may be sudachitin and / or demethoxysudachitin. The production method of the present embodiment is suitable for the production of polymethoxyflavone, particularly sudachitin and demethoxysudachitin, and can greatly improve the yield thereof.

[0050] 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, the temperature in the muffle furnace 3 is easily made uniform. Therefore, even when multiple raw material containers containing raw material liquids are placed in the autoclave, the temperature of each raw material liquid is easily made 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. EXAMPLES

[0051] 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.

[0052] Example 1 Sudachi peel extract powder (manufactured by Ikeda Yakuso Co., Ltd.), which contains 1000 ppm by mass of sudachitin and 9000 ppm by mass of glycoside-derived sudachitin, was dissolved / dispersed in ultrapure water to a concentration of 5% by mass to prepare an aqueous dispersion of sudachi peel extract. 12 L of this aqueous dispersion was placed in a container. An 18.5 L enamel tank (manufactured by Noda Horo) was used as the container. The enamel tank is an iron tank whose entire inner surface has been enameled. Next, a tank with an internal volume of 2 m was filled with water. 3It was placed in a hot air circulation type autoclave (manufactured by Ashida Seisakusho Co., Ltd.), and the glycoside decomposition treatment was performed on the sudachi peel extract aqueous dispersion at 180°C for 1 hour. For the decomposition treatment, saturated steam at 180°C was supplied from a boiler into the autoclave tank (pressure vessel), and the steam supply amount and pressure valve were adjusted while maintaining the tank pressure at 1 MPa, which is the saturated steam pressure of water at 180°C. After the decomposition treatment, the pressure inside the tank was 0.9 MPa and the temperature inside the tank was 180°C. The autoclave was naturally cooled for 10 minutes until the pressure inside the tank reached 0.7 MPa and the temperature inside the tank reached 165°C. After natural cooling, the valve was opened, and compressed air at a pressure of 1 MPa was sent into the tank using the compressor attached to the device. Since the pressure inside the tank immediately after sending in the compressed air exceeded 1 MPa, the 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, the cooling was carried out while appropriately reducing the tank pressure so as not to fall below the saturated steam pressure at that time. Two hours after the start of cooling with compressed air, since the temperature of the aqueous dispersion fell below 100°C (the saturated steam pressure of the aqueous dispersion fell below normal pressure (0.1 MPa)), the lid of the tank was opened, the container was taken out, and it was naturally cooled to room temperature (25°C). After cooling, the glycoside decomposition product deposited and adhered to the inner surface of the container was taken out using a medicine spoon with a take-out time of 5 minutes. The yield of the taken-out glycoside decomposition product is shown in Table 1.

[0053] Next, the solution and solids in the container were filtered under reduced pressure using a hydrophilic PTFE membrane filter with an opening of 0.2 μm (Omnipore 0.2 μm JG (Merck Millipore, product name)) with a diaphragm pump. The separated solution contained dissolved sugar derived from the decomposed glycoside, and the solid contained a high concentration of decomposed sudachitin. The obtained solid was 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. Next, the glycoside decomposition product was adjusted to a 5% dispersion with ethanol, treated under reflux at 60 ° C for 1 hour, sudachitin was extracted into ethanol, and the mixture was filtered under reduced pressure using a hydrophilic PTFE membrane filter with an opening of 0.2 μm (Omnipore 0.2 μm JG (Merck Millipore, product name)) with a diaphragm pump to obtain a sudachitin solution. The obtained sudachitin solution was vacuum-dried using a diaphragm pump while heating at 60° C. to obtain a powdered sudachitin concentrate.

[0054] Example 2 A powdered sudachitin concentrated powder was obtained in the same manner as in Example 1, except that a stainless steel tank that had been hydrophilized was used as a container instead of a 18.5 L enamel tank. The stainless steel tank that had been hydrophilized 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 resulting mixture at 140°C for 1 hour.

[0055] Comparative Example 1 A powdered sudachitin concentrate powder 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 as the container instead of the 18.5 L enamel tank.

[0056] <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 the 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. Component analysis of this ethanol solution was performed by high performance liquid chromatography (HPLC). A calibration curve was created using a commercially available sudachitin standard purified sample as the standard substance, and it was used to estimate the sudachitin concentration in the sudachitin concentrated powder. The "Chromaster" manufactured by Hitachi High-Tech was used as the HPLC apparatus. The results are shown in Table 1.

[0057] (Calculation of the yield of sudachitin) The yield of sudachitin was determined from the mass and sudachitin concentration of the sudachitin concentrated powder. The yield indicates the ratio of the mass of sudachitin contained in the obtained sudachitin concentrated powder to the total mass of sudachitin and glycoside-derived sudachitin contained in the aqueous dispersion charged into the raw material container.

[0058] (Measurement of contact angle) The contact angle with respect to water at a measurement temperature of 25°C was measured using a contact angle meter DM-501 type manufactured by Kyowa Interface Science Co., Ltd. in an environment with a humidity of 40% RH. The contact angle was measured 5 times using ultrapure water with respect to the contact surface with the raw material liquid in the raw material container, and the average value was obtained as the contact angle. The droplet volume of water was set to 1 μl, and the contact angle after standing for 3 seconds was read. As the water, ultrapure water (electrical resistivity: 18 MΩ·cm or more) collected from an ultrapure water production apparatus (PRO-0500 (model number), manufactured by Organo Corporation) was used. The results are shown in Table 1.

[0059]

Table 1

[0060] The sudachitin concentrations in the sudachitin concentrated powders obtained in the examples and comparative examples all exceeded 9% by mass, confirming that the glycoside decomposition treatment was properly performed. In Examples 1 and 2 where the contact angle of the surface in contact with the raw material liquid in the raw material container was less than 35°, the yield exceeded 80% by mass, indicating that the glycoside decomposition products were efficiently recovered.

Industrial Applicability

[0061] According to the method for decomposing flavonoid glycosides of the present invention, flavonoid glycosides can be efficiently decomposed into flavonoids without using an acid, and the yield of flavonoids can be improved.

Explanation of Symbols

[0062] 1... Sealed door, 2... Pressure vessel, 3... Muffle furnace, 4... Air duct, 5... Heater, 6... Cooler, 7... Motor, 8... Circulation fan, 9... Air duct, 10... Raw material liquid, 11... Raw material container, 12... Movable table, 13... Boiler, 14... Valve, 15... Pressure gauge, 16... Pressure valve, 20... Contact surface.

Claims

1. A raw material container containing a raw material liquid containing a flavonoid glycoside is placed in an autoclave, and a hydrothermal treatment step of decomposing the flavonoid glycoside into a flavonoid by subjecting the raw material liquid to hydrothermal treatment is provided. The concentration of the raw material in the raw material liquid is 1 to 30% by mass based on the total amount of the raw material liquid. A method for decomposing a flavonoid glycoside, wherein the contact surface of the raw material container with the raw material liquid is a surface having a contact angle with water of less than 35° at a measurement temperature of 25°C.

2. The decomposition method according to claim 1, wherein the contact surface is a surface subjected to honing treatment.

3. The decomposition method according to claim 1, wherein the contact surface is a surface treated with a polysilazane compound.

4. The decomposition method according to claim 3, wherein the polysilazane compound is perhydropolysilazane.

5. The decomposition method according to any one of claims 1 to 4, further comprising a pressure reduction step of reducing the pressure in the autoclave after the hydrothermal treatment step.

6. The decomposition method according to any one of claims 1 to 5, wherein the hydrothermal treatment is performed by supplying water vapor from the outside into the autoclave.

7. The decomposition method according to any one of claims 1 to 6, wherein in the hydrothermal treatment step, the pressure in the autoclave is 0.2 to 1.6 MPa and the temperature is 120 to 200°C.

8. The decomposition method according to any one of claims 1 to 7, wherein the flavonoid glycoside contains sudachitin glycoside and / or demethoxysudachitin glycoside.

9. A decomposition step of decomposing a flavonoid glycoside by the method according to any one of claims 1 to 8, and An extraction step of extracting a flavonoid from the decomposition product obtained in the decomposition step. A method for producing a flavonoid, comprising:

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