Method for decomposing flavonoid glycosides and method for producing flavonoids

Abstract

A method for decomposing flavonoid glycosides, comprising heating a raw material containing flavonoid glycosides in a sealed container in the presence of alcohol at a temperature exceeding the boiling point of the alcohol at normal pressure, thereby decomposing the flavonoid glycosides into flavonoids.

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 differ in characteristics and actions depending on the type, many of them have a strong antioxidant action. For example, polymethoxyflavone, a flavonoid contained in citrus fruits, is known to have antioxidant action, cancer-suppressing action, antibacterial action, antiviral action, anti-allergic action, melanin production inhibitory action, blood glucose level inhibitory action, 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 demanded.

[0006] For example, the peel of citrus fruits contains not only flavonoids but also a larger amount of flavonoid glycosides. If these can be recovered as flavonoids, the yield of flavonoids can be improved. One method for decomposing flavonoid glycosides into flavonoids is to react them with an acid such as hydrochloric acid. However, this method has problems such as the risk of residual acid contaminating the product and the formation of by-reaction products between the acid and flavonoids. One method for removing impurities such as acid and by-products is to separate and purify the flavonoids in the decomposition products by liquid chromatography, but this method is costly and has poor production efficiency. Therefore, there is a need for a new method for decomposing flavonoid glycosides that does not use acid.

[0007] This invention has been made in view of the problems of the above-mentioned prior art, and aims to provide a method for decomposing flavonoid glycosides that can efficiently decompose flavonoid glycosides into flavonoids without using acid, and a method for producing flavonoids that can improve the yield of flavonoids. [Means for solving the problem]

[0008] To achieve the above objective, the present invention provides a method for decomposing flavonoid glycosides, which involves heating a raw material containing flavonoid glycosides in the presence of alcohol in a sealed container at a temperature exceeding the boiling point of the alcohol at atmospheric pressure, thereby decomposing the flavonoid glycosides into flavonoids.

[0009] According to the above method, flavonoid glycosides can be efficiently broken down into flavonoids without the use of acid. While flavonoid glycosides are typically broken down by hydrolysis, and therefore usually by hydrothermal treatment using water, the inventors have discovered that, for reasons that are not entirely clear, using alcohol instead of water accelerates the breakdown of flavonoid glycosides, yielding a high concentration of flavonoids. Therefore, by using the above method, it becomes possible to produce flavonoids efficiently and at low cost.

[0010] In the above method, the flavonoid glycoside may contain sudachitin glycoside and / or demethoxysudachitin glycoside. According to the above method, sudachitin glycoside and demethoxysudachitin glycoside can be decomposed particularly efficiently.

[0011] In the above method, the heat treatment temperature may be within the range of 110 to 300°C. A temperature within this range can further promote the decomposition of flavonoid glycosides.

[0012] The present invention also provides a method for producing flavonoids, comprising a degradation step of degrading flavonoid glycosides by the method of the present invention described above, and an extraction step of extracting flavonoids from the degradation products obtained in the degradation step. According to this production method, flavonoids can be produced in high yield, at low cost, and efficiently. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a method for decomposing flavonoid glycosides that can efficiently decompose flavonoid glycosides into flavonoids without using acid, and a method for producing flavonoids that can improve the yield of flavonoids. [Modes for carrying out the invention]

[0014] The present invention will be described in detail below with reference to its preferred embodiments. However, the present invention is not limited to the following embodiments.

[0015] In this specification, numerical ranges indicated using "~" represent a range that includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit of a numerical range in one step can be arbitrarily combined with the upper or lower limit of a numerical range in another step. In numerical ranges described in this specification, the upper or lower limit of that numerical range may be replaced with the values ​​shown in the examples. "A or B" means that either A or B is included, or both are included. Unless otherwise specified, the materials exemplified in this specification can be used individually or in combination of two or more.

[0016] (Methods for breaking down flavonoid glycosides) The method for decomposing flavonoid glycosides according to this embodiment involves heating a raw material containing flavonoid glycosides in the presence of alcohol in a sealed container at a temperature exceeding the boiling point of the alcohol at atmospheric pressure, thereby decomposing the flavonoid glycosides into flavonoids. In this embodiment, atmospheric pressure refers to 0.1 MPa (atmospheric pressure).

[0017] Flavonoid glycosides are hydrophilic compounds having a structure in which a flavonoid and a sugar are linked by a glycosidic bond. The flavonoids (aglycones) from which flavonoid glycosides are derived are aromatic compounds with a phenylchroman skeleton as their basic structure, and include flavones, flavonols, flavanones, flavanonols, isoflavones, anthocyanins, chalcones, and aurones. Among these, the flavonoid may also be polymethoxyflavone, which is a type of flavone.

[0018] Examples of polymethoxyflavones include sudachitin, demethoxysudachitin, nobiletin, tangeretin, pentamethoxyflavone, tetramethoxyflavone, and heptamethoxyflavone. Among these, the polymethoxyflavone may be sudachitin or demethoxysudachitin.

[0019] Furthermore, the flavonoids may also include quercetin, hesperetin, or anthocyanidins.

[0020] The sugars that serve as the basis for flavonoid glycosides are not particularly limited, and include known sugars that can form glycosides by bonding with the aforementioned flavonoids via glycosidic bonds.

[0021] The raw materials subjected to heat treatment may contain other components besides flavonoid glycosides. Examples of other components include flavonoids, water-soluble dietary fiber, sparingly soluble dietary fiber, sugars, etc. The flavonoid glycoside content in the raw materials is preferably 0.1% by mass or more, more preferably 0.25 to 30% by mass, even more preferably 0.3 to 15% by mass, and particularly preferably 0.5 to 5% by mass, based on the total solid content of the raw materials. If the raw materials further contain flavonoids, the flavonoid glycoside content 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 1 part by mass of flavonoid content.

[0022] Specifically, the raw materials can include flowers, leaves, roots, stems, fruits, and seeds of plants and seaweed. In particular, the peel contains a large amount of polymethoxyflavones and their glycosides, so the juice residue of citrus fruits can be suitably used. The raw material may also be a dried powder obtained from citrus fruits, or a dried powder obtained from the peel of citrus fruits. Examples of citrus fruits include sudachi, Satsuma mandarin, ponkan, and shikwasa. The citrus fruit may also be sudachi, which contains a large amount of polymethoxyflavones such as sudachitin and demethoxysudachitin, and their glycosides.

[0023] The heat treatment can be carried out by enclosing the raw material together with a solvent containing alcohol in a pressure-resistant sealed container and heating it at a temperature exceeding the normal boiling point of the alcohol while keeping it sealed. By heating the reaction solution containing the raw material and the solvent in the sealed container, the inside of the sealed container becomes a heating and pressurizing environment, and a decomposition reaction of the flavonoid glycoside occurs. The heat treatment may be carried out while stirring the reaction solution. The pressure-resistant sealed container is not particularly limited. For example, a known container that can be used for hydrothermal treatment using water as a solvent can be used. As the pressure-resistant sealed container, for example, an autoclave can be used.

[0024] The solvent may be alcohol alone or a mixed solvent of alcohol and other solvents. Examples of alcohol include methanol, ethanol, propanol, glycerin, etc. Among these, methanol and ethanol are preferred because they can further promote the decomposition of flavonoid glycosides. Examples of other solvents include water, ethyl acetate, hexane, acetone, etc.

[0025] The solvent may be a mixed solvent of water and alcohol. When using a mixed solvent of water and alcohol, the mass ratio of water to alcohol (water / alcohol) can be 1 / 99 to 99 / 1 and is appropriately selected according to the solubility of the glycoside to be decomposed. By selecting a mixing ratio with a high solubility, the reaction can be carried out efficiently at once. The mass ratio of water to alcohol in the solvent (water / alcohol) may be 1 / 99 to 50 / 50, 1 / 99 to 20 / 80, 1 / 99 to 10 / 90, 2 / 98 to 6 / 94, or 3 / 97 to 5 / 95. When the mass ratio of water to alcohol is within the above range, the decomposition of flavonoid glycosides can be further promoted.

[0026] The alcohol content in the solvent may be 50% or more by mass, 80% or more by mass, 90% or more by mass, 94% or more by mass, or 95% or more by mass, based on the total amount of solvent, and may also be less than 100% by mass, 99% or less by mass, 98% or less by mass, or 97% or less by mass. If the alcohol content in the solvent is above the above lower limit, the decomposition of flavonoid glycosides can be further promoted.

[0027] The water content in the solvent may be greater than 0% by mass, 1% or more by mass, 2% or more by mass, or 3% or more by mass, based on the total amount of solvent, and may also be 50% or less by mass, 20% or less by mass, 10% or less by mass, 6% or less by mass, or 5% or less by mass. If the water content in the solvent is above the lower limit, the solubility and dispersibility of flavonoid glycosides in the solvent can be improved, and the decomposition of flavonoid glycosides can be further promoted. On the other hand, if the water content exceeds the upper limit, the alcohol content in the solvent tends to decrease relatively, and the effect of promoting the decomposition of flavonoid glycosides tends to decrease, so it is preferable that the water content be below the upper limit.

[0028] The amount of solvent is not particularly limited, as long as it is sufficient for the heat treatment. However, the solid content of the raw material may be 1 part by mass or more, 2 parts by mass or more, 4 parts by mass or more, or 5 parts by mass or more per 100 parts by mass of solvent, or it may be 100 parts by mass or less, 33 parts by mass or less, 25 parts by mass or less, 18 parts by mass or less, or 11 parts by mass or less. Furthermore, the solid content of the raw material in the reaction solution (raw material concentration) may be 1.0% by mass or more, 2.0% by mass or more, 3.8% by mass or more, or 4.8% by mass or more, based on the total amount of the reaction solution, or it may be 50% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 10% by mass or less. When the amount of solvent or the raw material concentration is within the above range, the decomposition of flavonoid glycosides can be carried out efficiently. In addition, when the ratio of solid content of the raw material to the solvent or the raw material concentration is below the above upper limit, the yield of flavonoids tends to improve when flavonoids are extracted from the decomposition products obtained by the decomposition method of this embodiment.

[0029] The reaction solution preferably does not contain acid. In particular, it is preferable that the reaction solution does not contain inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid. If the reaction solution contains inorganic acids, it is undesirable because highly toxic organochlorine compounds, organonitrogen compounds, and organosulfur compounds are easily generated by heating in a sealed container. Furthermore, if the reaction solution contains inorganic acids, there is a risk of residual inorganic acids remaining in the product, and a process to thoroughly remove the inorganic acids to prevent residual inorganic acids in the product is required, which is costly. The inorganic acid content in the reaction solution is preferably 1% by mass or less, 0.1% by mass or less, or 0.01% by mass or less based on the total amount of the reaction solution. The content of organic acids of biological origin such as citric acid, acetic acid, aspartic acid, amino acids, and nucleic acids is not particularly limited. In this specification, the total amount of the reaction solution means the total amount of the reaction solution before heating (before heating and pressurizing in a sealed container).

[0030] The content of flavonoid glycosides in the reaction solution may be 0.005% by mass or more, 0.01% by mass or more, 0.02% by mass or more, or 0.03% by mass or more, based on the total amount of the reaction solution, and may also be 10% by mass or less, 5% by mass or less, 3% by mass or less, 1% by mass or less, 0.9% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.1% by mass or less. When the above content is above the lower limit, the efficiency of flavonoid production tends to improve. On the other hand, when the above content is below the upper limit, when flavonoids are extracted from the decomposition products obtained by the decomposition method of this embodiment, the yield of flavonoids tends to improve. This is thought to be because when the concentration of flavonoid glycosides in the reaction solution is high, polymerization of sugars separated from flavonoid glycosides (caramelization reaction) and, if amino acids are present in the reaction solution, polymerization of sugars and amino acids (Maillard reaction) are more likely to occur. Sugar polymers (caramelization reaction products and Maillard reaction products) are poorly soluble in both water and alcohol. Furthermore, it is presumed that these sugar polymers incorporate decomposed flavonoids, thereby hindering flavonoid extraction and reducing the flavonoid yield.

[0031] The reaction conditions for the heat treatment are not particularly limited, but for example, they can be 110 to 300°C for 0.5 to 20 hours. The reaction temperature is preferably 120 to 190°C, and more preferably 140 to 185°C. When the reaction temperature is 110°C or higher, the reaction tends to proceed more smoothly, and when it is 300°C or lower, the carbonization of the raw materials and flavonoids does not proceed easily, and the yield tends to improve. 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 more, the reaction tends to proceed more easily, and when it is 20 hours or less, it tends to be easier to balance the progress of the reaction with the cost.

[0032] When using a mixed solvent during heat treatment, the reaction temperature should be higher than the temperature at which the alcohols in the mixed solvent evaporate at room temperature (i.e., the boiling point considering boiling point elevation, etc.). If the solvent contains multiple types of alcohols, the reaction temperature can be set based on the alcohol with the lowest boiling point. Furthermore, from the viewpoint of efficiently decomposing flavonoid glycosides, it is preferable that the reaction temperature be higher than the temperature at which the solvent with the highest boiling point evaporates at room temperature in a solvent consisting of multiple types of alcohols, or in a mixed solvent of alcohol and other solvents.

[0033] From the viewpoint of improving the yield of flavonoids, it is preferable to perform the heat treatment under low temperature (e.g., below 200°C) and long duration (e.g., 1 hour or more). If the reaction temperature is high, bumping of the reaction solution is likely to occur during cooling after the reaction. When bumping occurs, the reaction solution splashes out of the container holding it, which tends to reduce the yield. In addition, if cooling is performed in a way that prevents the aforementioned bumping, a long cooling time is required, which reduces work efficiency. This problem of long cooling time is a particular disadvantage when mass-producing flavonoids. From the viewpoint of improving these problems, it is preferable to perform the heat treatment under low temperature and long duration conditions. Even when the heat treatment is performed at a low temperature, the flavonoid glycoside can be sufficiently broken down into flavonoids by extending the reaction time. Furthermore, performing the heat treatment under low temperature and long duration conditions can shorten the overall process time, including the cooling time after the heat treatment, compared to performing the heat treatment under high temperature and short duration conditions.

[0034] The pressure inside the container during the heat treatment should be the saturated vapor pressure of the alcohol or a mixed solvent of alcohol and another solvent corresponding to the above reaction temperature or higher, but from the viewpoint of the pressure resistance of the apparatus, the saturated vapor pressure is preferable. The pressure inside the sealed container during the heat treatment can be, for example, 0.2 to 1.6 MPa.

[0035] By performing heat treatment under the above conditions, flavonoid glycosides can be efficiently broken down into flavonoids (more specifically, into flavonoids and sugars).

[0036] (Method for producing flavonoids) The method for producing flavonoids according to this embodiment includes a decomposition step of decomposing a flavonoid glycoside and an extraction step of extracting flavonoids from the decomposition product obtained in the decomposition step. The decomposition step is a step of decomposing a flavonoid glycoside using the flavonoid glycoside decomposition method according to this embodiment described above.

[0037] In the extraction process, flavonoids are extracted from the decomposition products obtained in the decomposition process. These decomposition products include flavonoids, sugars, flavonoid glycosides remaining undecomposed, water-soluble and sparingly soluble cellulose, and their decomposition products. Here, flavonoids are hydrophobic, while sugars, flavonoid glycosides, water-soluble cellulose, and their decomposition products are hydrophilic. Therefore, after heat treatment, the water-insoluble components contain a high concentration of flavonoids, and by separating the aqueous solution from the water-insoluble components after heat treatment, the flavonoids can be concentrated. Furthermore, the water-insoluble components can be dissolved in a solvent that dissolves flavonoids, such as ethanol, ethyl acetate, hexane, toluene, or a mixture thereof, and the insoluble matter can be removed by filtration, thereby further extracting and purifying the flavonoids. Afterward, the filtrate can be dried to obtain a high concentration of flavonoids.

[0038] The above method allows for the efficient production of flavonoids in high yield. The flavonoids produced by the production method of this embodiment may be polymethoxyflavones, sudachitin, and / or demethoxysudachitin. The production method of this embodiment is suitable for the production of polymethoxyflavones, particularly sudachitin and demethoxysudachitin, and can significantly improve the yield. [Examples]

[0039] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0040] (Example 1) 2g of sudachi peel extract powder (manufactured by Ikeda Yakusou Co., Ltd.), containing 1000 ppm by mass of sudachitin, 1500 ppm by mass of demethoxysudachitin, 8000 ppm by mass of glycoside-derived sudachitin, and 3000 ppm by mass of glycoside-derived demethoxysudachitin, was dissolved / dispersed in 50g of ethanol (special grade, 99.5% purity, manufactured by Wako Pure Chemical Industries, Ltd.) as a solvent. This mixture was sealed in a 100ml Teflon® container, and the Teflon® container was then placed inside a stainless steel pressure-resistant container, which was then sealed. Inside the sealed pressure-resistant container, the solution in the Teflon® container was heated with a heater while stirring at 600 rpm using a magnetic stirrer until the solution reached 180°C. After reaching 180°C, the mixture was heated at 180°C for 60 minutes while continuing to stir. Subsequently, heating and stirring were stopped, and the mixture was allowed to cool naturally to room temperature (25°C). The highest temperature reached during the heat treatment was 181°C. After cooling, the solution and solids in the Teflon® container were transferred to a beaker and vacuum-dried using a diaphragm pump under heating at 60°C to obtain 1.9 g of powdered glycoside decomposition sample 1.

[0041] (Example 2) Except for changing the solvent to 50 g of methanol (special grade, 99.5% purity, manufactured by Wako Pure Chemical Industries, Ltd.), the same procedure as in Example 1 was followed to obtain 1.8 g of powdered glycoside decomposition sample 2.

[0042] (Example 3) Except for changing the solvent to 50 g of glycerin (manufactured by Wako Pure Chemical Industries, Ltd.), the procedure was the same as in Example 1, and the mixture was heated at 180°C for 60 minutes. After that, heating and stirring were stopped, and the mixture was allowed to cool naturally to room temperature (25°C). After cooling, 1 L of water was added to the solution, and it was stirred to precipitate glycoside decomposition products containing sudachitin and demethoxysudachitin. This solution was subjected to vacuum filtration using a diaphragm pump through a 0.2 μm PTFE mesh, and the precipitated solid was separated to obtain powdered glycoside decomposition sample 3.

[0043] (Example 4) Except for changing the solvent to a water / ethanol mixed solvent (mass ratio 5 / 95), 1.85 g of powdered glycoside decomposition sample 4 was obtained in the same manner as in Example 1.

[0044] (Example 5) Except for changing the solvent to a water / ethanol mixed solvent (mass ratio 20 / 80), 1.85 g of powdered glycoside decomposition sample 5 was obtained in the same manner as in Example 1.

[0045] (Example 6) Except for changing the solvent to a water / ethanol mixed solvent (mass ratio 50 / 50), 1.7 g of powdered glycoside decomposition sample 6 was obtained in the same manner as in Example 1.

[0046] (Example 7) Except for changing the solvent to a water / ethanol mixed solvent (mass ratio 80 / 20), 1.85 g of powdered glycoside decomposition sample 7 was obtained in the same manner as in Example 1.

[0047] (Example 8) Except for changing the solvent to a water / ethanol mixed solvent (mass ratio 95 / 5), 1.85 g of powdered glycoside decomposition sample 8 was obtained in the same manner as in Example 1.

[0048] (Examples 9-11) Powdered glycoside decomposition samples 9 (1.9g), 10 (1.85g), and 11 (1.8g) were obtained in the same manner as in Example 1, except that the water temperature during the heat treatment was 160°C (Example 9), 140°C (Example 10), and 120°C (Example 11).

[0049] (Examples 12-15) Except for setting the heat treatment reaction time to 600 minutes (10 hours) and the temperature during treatment to 120°C (Example 12), 140°C (Example 13), 160°C (Example 14), and 180°C (Example 15), the procedure was the same as in Example 1 to obtain powdered glycoside decomposition samples 12 (1.75g), 13 (1.8g), 14 (1.8g), and 15 (1.8g).

[0050] (Comparative Example 1) 2g of the same sudachi peel extract powder (manufactured by Ikeda Yakusou Co., Ltd.) used in Example 1 was used as the sample for Comparative Example 1.

[0051] (Comparative Example 2) 2g of the same sudachi peel extract powder (manufactured by Ikeda Yakusou Co., Ltd.) used in Example 1 was placed in a heat-resistant container, covered with aluminum foil with holes of approximately φ3mm to prevent the powder from scattering due to the hot air, and heated in an oven at 180°C for 1 hour to obtain a heat-treated sample of sudachi peel extract powder, totaling 1.65g.

[0052] (Reference example 1) Two g of the same sudachi peel extract powder (manufactured by Ikeda Yakusou Co., Ltd.) used in Example 1 was dissolved and dispersed in 50 g of 1 N hydrochloric acid. The mixture was heated at 80°C for 1 hour while stirring with a magnetic stirrer at 600 rpm, after which heating and stirring were stopped and the mixture was allowed to cool naturally to room temperature (25°C). The cooled reaction solution was neutralized with a 1 N sodium hydroxide aqueous solution and vacuum-dried using a diaphragm pump under heating at 60°C to obtain 1.8 g of a powdered glycoside hydrochloric acid decomposition sample.

[0053] <Measurement of sudachitin and demethoxysudachitin concentrations> The sudachitin and demethoxysudachitin concentrations of the samples obtained in each example, comparative example, and reference example were measured by the following method. First, 0.1 g of the sample 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 analyzed for its components by high-performance liquid chromatography (HPLC). Calibration curves were created using commercially available purified sudachitin and demethoxysudachitin standard samples as standard substances, and the sudachitin and demethoxysudachitin concentrations in the samples were estimated using these curves. A Hitachi High-Tech "ChromMaster" HPLC system was used. The results are summarized in Table 1.

[0054] [Table 1]

[0055] As shown in Table 1, in all of Examples 1 to 15, the sudachitin and demethoxysudachitin concentrations were increased compared to Comparative Examples 1 and 2. This indicates that the decomposition of sudachitin glycosides and demethoxysudachitin glycosides newly generates sudachitin and demethoxysudachitin, which are polymethoxyflavones, thus improving the yield of sudachitin and demethoxysudachitin. Furthermore, in Examples 1 to 15, it was found that the sudachitin and demethoxysudachitin concentrations could be improved without using hydrochloric acid, as in Reference Example 1, and under certain conditions, the concentrations could be improved even more than when hydrochloric acid was used.

Claims

1. A method for decomposing flavonoid glycosides, comprising heating a raw material containing flavonoid glycosides in the presence of alcohol in a sealed container at a temperature exceeding the boiling point of the alcohol at atmospheric pressure, thereby decomposing the flavonoid glycosides into flavonoids, The flavonoid glycoside comprises a sudachitin glycoside and / or a demethoxysudachitin glycoside. A decomposition method in which the heat treatment temperature is within the range of 110 to 300°C.

2. The decomposition method according to claim 1, wherein the heat treatment is performed by heating the reaction solution containing the raw materials and the alcohol in the sealed container.

3. The decomposition method according to claim 2, wherein the amount of inorganic acid in the reaction solution is 1% by mass or less based on the total amount of the reaction solution.

4. A method for decomposing a flavonoid glycoside, comprising heating a raw material containing a flavonoid glycoside in the presence of alcohol in a sealed container at a temperature exceeding the boiling point of the alcohol at atmospheric pressure, thereby decomposing the flavonoid glycoside into a flavonoid, The flavonoid glycoside comprises a sudachitin glycoside and / or a demethoxysudachitin glycoside. The heat treatment is carried out by heating the reaction solution containing the raw materials and the alcohol in the sealed container. A decomposition method wherein the amount of inorganic acid in the reaction solution is 1% by mass or less based on the total amount of the reaction solution.

5. The decomposition method according to any one of claims 2 to 4, wherein the content of the flavonoid glycoside in the reaction solution is 0.01 to 3% by mass based on the total amount of the reaction solution.

6. The decomposition method according to any one of claims 1 to 5, wherein the heat treatment is carried out in the presence of a solvent containing the alcohol and water.

7. The decomposition method according to claim 6, wherein the alcohol content in the solvent is 90% by mass or more based on the total amount of the solvent.

8. A method for decomposing a flavonoid glycoside, comprising heating a raw material containing a flavonoid glycoside in the presence of alcohol in a sealed container at a temperature exceeding the boiling point of the alcohol at atmospheric pressure, thereby decomposing the flavonoid glycoside into a flavonoid, The flavonoid glycoside comprises a sudachitin glycoside and / or a demethoxysudachitin glycoside. The aforementioned heat treatment is carried out in the presence of a solvent containing the alcohol and water. A decomposition method wherein the alcohol content in the solvent is 90% by mass or more based on the total amount of the solvent.

9. The decomposition method according to any one of claims 6 to 8, wherein the water content in the solvent is 10% by mass or less based on the total amount of the solvent.

10. A method for decomposing a flavonoid glycoside, comprising heating a raw material containing a flavonoid glycoside in the presence of alcohol in a sealed container at a temperature exceeding the boiling point of the alcohol at atmospheric pressure, thereby decomposing the flavonoid glycoside into a flavonoid, The flavonoid glycoside comprises a sudachitin glycoside and / or a demethoxysudachitin glycoside. The aforementioned heat treatment is carried out in the presence of a solvent containing the alcohol and water. A decomposition method wherein the water content in the solvent is 10% by mass or less based on the total amount of the solvent.

11. The decomposition method according to any one of claims 1 to 10, wherein the raw material is a dried powder obtained from citrus fruits or the peel of citrus fruits.

12. A method for decomposing a flavonoid glycoside, comprising heating a raw material containing a flavonoid glycoside in the presence of alcohol in a sealed container at a temperature exceeding the boiling point of the alcohol at atmospheric pressure, thereby decomposing the flavonoid glycoside into a flavonoid, The flavonoid glycoside comprises a sudachitin glycoside and / or a demethoxysudachitin glycoside. A decomposition method wherein the raw material is a dried powder obtained from citrus fruits or the peel of citrus fruits.

13. The decomposition method according to any one of claims 1 to 12, wherein the raw material further comprises a flavonoid.

14. The decomposition method according to any one of claims 1 to 13, wherein the heat treatment is performed at a temperature of 110 to 190°C for 0.5 to 10 hours.

15. A degradation step of degrading a flavonoid glycoside by the method described in any one of claims 1 to 14, An extraction step for extracting flavonoids from the decomposition products obtained in the aforementioned decomposition step, A method for producing flavonoids, including

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