CN116239558A - Preparation method of eriodictyol - Google Patents

Abstract

The invention discloses a preparation method of eriodictyol, which comprises the following steps: the hesperetin reacts with an oxidant in a reaction solvent to obtain a reaction intermediate solution, and a reducing agent is added into the reaction intermediate solution to obtain the eriodictyol. The preparation method disclosed by the invention has the advantages of wide raw material sources, low cost, easiness in obtaining, no operation danger and stable property, the reaction condition is mild, the one-pot product is realized by one-pot oxidation reduction, no intermediate step treatment and purification are needed, the whole post-treatment operation after the reaction is finished is very simple and easy, and the subsequent production scale is conveniently amplified.

Description

Preparation method of eriodictyol

Technical Field

The invention belongs to the technical field of synthesis of organic medical intermediates, and particularly relates to a preparation method of eriodictyol.

Background

Eriodictyol is a flavonoid compound isolated from herbs and has antioxidant, antiinflammatory, analgesic, and diabetes and diabetic complications improving effects. The synthesis methods reported in the current literature mainly comprise two methods; the first method is to obtain eriodictyol by taking luteolin as a raw material and methanol as a solvent, reducing double bonds by palladium-carbon hydrogenation, and performing post-treatment through silica gel column purification, wherein the reaction formula is as follows:

the second is to take hesperetin as a raw material, pyridine as a solvent, add anhydrous aluminum chloride and heat at 70 ℃, and then treat with hydrochloric acid to obtain eriodictyol, wherein the reaction formula is as follows:

in the first method, a metallic palladium catalyst is required to be used for reduction, a product with a non-absolute configuration is obtained, and further chiral resolution is required to be carried out to obtain the product with the absolute configuration, so that the method is inconvenient in terms of experimental steps and purification difficulty; in the second method, anhydrous aluminum chloride which is extremely easy to absorb moisture and has strong corrosiveness is required to be used for demethylation, the use of a large amount of aluminum trichloride can lead to quite complex post-treatment, intense heat release is required during water quenching, great care is required, the generated aluminum salt can lead to serious emulsification phenomenon, great trouble is caused to the subsequent extraction step, and a large amount of corrosive waste liquid is generated. Therefore, the method has great limitation in terms of economy, environmental protection and large-scale synthesis.

Therefore, it is necessary to research and develop an eriodictyol preparation method which has the advantages of wide raw material sources, low cost, easy availability, no operation danger, stable property, simple and easy post-treatment and convenient subsequent scale-up.

Disclosure of Invention

The preparation method provided by the invention has the advantages of wide raw material sources, low cost, easiness in obtaining, no operation danger and stable property, the reaction condition is mild, the one-pot product is realized by one-pot oxidation reduction, the treatment of intermediate steps is not needed, the purification is not needed, the whole post-treatment operation after the reaction is finished is very simple and easy, and the subsequent production scale is conveniently amplified.

The invention provides a preparation method of eriodictyol, which comprises the following steps: the hesperetin reacts with an oxidant in a reaction solvent to obtain a reaction intermediate solution, and a reducing agent is added into the reaction intermediate solution to obtain the eriodictyol.

The synthetic route of the preparation method of eriodictyol in the invention is as follows:

the synthetic reaction mechanism of eriodictyol in the present invention is as follows:

in one embodiment of the invention, the intermediate solution is obtained by the following steps: and adding the raw material hesperetin into a reaction solvent, adding an oxidant at one time, protecting a reaction system by using inert gas, and reacting for 24 hours at room temperature to complete the conversion of a reaction intermediate state, thereby obtaining a reaction intermediate state solution.

Preferably, the oxidizing agent is 2-iodoxybenzoic acid.

Preferably, the reaction solvent is at least one of tetrahydrofuran, dioxane or N, N-dimethylformamide.

Preferably, the ratio of the reaction solvent to the raw material hesperetin is 30mL/g.

In one embodiment of the present invention, the step of adding a reducing agent to the intermediate solution for reaction to obtain eriodictyol comprises the steps of: ice bath for 0.5h, preparing aqueous solution of reducing agent, adding aqueous solution of reducing agent into the intermediate solution, continuously ice bath for 0.5h, removing ice bath, reacting for 3h at room temperature, distilling to remove reaction solvent, adding saturated ammonium chloride solution into the rest water phase, extracting with ethyl acetate, mixing organic phases, washing saturated sodium bicarbonate solution, washing saturated saline solution, drying with anhydrous sodium sulfate, distilling to remove solvent to obtain yellow solid, adding the solid into mixed solvent of methanol and ethyl acetate, repeatedly pulping for 2-3 times to obtain eriodictyol.

Preferably, the reducing agent is at least one of sodium dithionite, sodium bisulphite or sodium thiosulfate.

Preferably, the aqueous solution concentration of the reducing agent is 0.2g/mL.

Preferably, in the mixed solvent of methanol and ethyl acetate, the volume ratio of the methanol to the ethyl acetate is 1:10.

compared with the prior art, the invention has the following beneficial effects:

1. all raw materials in the preparation method of the invention have wide sources, low cost and easy availability, and all raw materials have no operation danger and stable properties.

2. The preparation method has mild reaction conditions and simple subsequent purification treatment.

3. The preparation method of the invention realizes one-pot product discharge through one-pot oxidation reduction, does not need intermediate steps for treatment and purification, and has the advantages of very simple and easy operation of the whole post-treatment operation after the reaction is finished, and convenient amplification of the subsequent production scale.

Of course, it is not necessary for any one product to practice the invention to achieve all of the advantages set forth above at the same time.

Drawings

FIG. 1 is a nuclear magnetic resonance spectrum of eriodictyol prepared in example 1;

FIG. 2 is a high performance liquid chromatography purity chart of eriodictyol obtained in example 1.

Detailed Description

In this document, a range from "one value to another value" is a shorthand way of referring individually to all the values in the range, which are avoided in the specification. Thus, recitation of a particular numerical range includes any numerical value within that range, as well as the smaller numerical range bounded by any numerical value within that range, as if the any numerical value and the smaller numerical range were written in the specification in the clear.

The raw materials and reagents used in the examples of the present invention are commercially available, and in the present invention, "under room temperature" means a temperature range of 20℃to 30℃and "under ice bath" means a temperature range of 5℃to 10 ℃.

The synthetic method of eriodictyol comprises the following reaction equation:

the preparation method of the invention realizes one-pot product discharge through one-pot oxidation reduction, does not need intermediate steps for treatment and purification, and has the advantages of very simple and easy operation of the whole post-treatment operation after the reaction is finished, and convenient amplification of the subsequent production scale.

The invention will be further illustrated with reference to specific examples. It should be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. The range of parameters that can be implemented by the present invention is not limited by the specific examples given in the following examples. Modifications and adaptations of the invention will occur to those skilled in the art and are intended to be within the scope of the invention in practice.

Example 1

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and tetrahydrofuran (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium dithionite (17.3 g,99.36 mmol) is dissolved in water (86.5 mL) and poured into the reaction for a small amount for many times, and the mixture is stirred for 0.5h continuously and then naturally heated to room temperature for stirring for 3h, thus obtaining yellow clarified liquid;

step 4: removing most of tetrahydrofuran by rotary evaporation;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain crude yellow solid 4.1g;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: the solid obtained by pulping at last is filtered out, and the solid is collected and dried to obtain white solid (1.75 g,36.6% yield) with the purity reaching 100%.

LC-MS(UV 214):289.00(M+H) ⁺ (100％purity)； ¹ H NMR(400MHz,dmso-d6)δ12.12(s,1H),10.75(s,1H),9.02(d,J＝17.2Hz,2H),6.79(d,J＝51.9Hz,3H),5.86(s,2H),5.36(d,J＝10.1Hz,1H),3.17(dd,J＝17.1,12.6Hz,1H),2.66(d,J＝14.6Hz,1H)。

Example 2

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and dioxane (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium dithionite (17.3 g,99.36 mmol) is dissolved in water (86.5 mL) and poured into the reaction for a small amount for many times, and the mixture is stirred for 0.5h continuously and then naturally heated to room temperature for stirring for 3h, thus obtaining yellow clarified liquid;

step 4: removing most of dioxane by using rotary steaming;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain crude yellow solid 4.0g;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: the solid obtained by pulping at last is filtered out, and the collected solid is dried to obtain white solid (1.67 g, product yield 35.1%) with purity up to 97%. LC-MS (UV 214): 289.0 (M+H) ⁺ ；RT＝1.604min；97％purity。

Example 3

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and ethylene glycol dimethyl ether (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium dithionite (17.3 g,99.36 mmol) is dissolved in water (86.5 mL) and poured into the reaction for a small amount for many times, and the mixture is stirred for 0.5h continuously and then naturally heated to room temperature for stirring for 3h, thus obtaining yellow clarified liquid;

step 4: removing most of ethylene glycol dimethyl ether by rotary evaporation;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain 3.8g of crude yellow solid;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: the solid obtained by pulping at last is filtered out, and the solid is collected and dried to obtain white solid (1.6 g, product yield 33.7%), the purity of which reaches 98.92%. LC-MS (UV 214): 289.0 (M+H) ⁺ ；RT＝1.613min；98.92％purity。

Example 4

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and tetrahydrofuran (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium thiosulfate (15.7 g,99.36 mmol) is dissolved in water (86.5 mL), and a small amount of sodium thiosulfate is poured into the reaction for many times, and is stirred for 0.5h continuously under ice bath condition, and then naturally warmed to room temperature and stirred for 3h, thus obtaining yellow clarified liquid; the mole ratio of the raw material hesperetin to the reducing agent is 1:6, preparing a base material;

step 4: removing most of tetrahydrofuran by rotary evaporation;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain 3.5g of crude yellow solid;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: the solid obtained by pulping at last is filtered out, and the solid is collected and dried to obtain white solid (1.34 g, product yield 28.1%), and LC-MS purity reaches 98.35%. LC-MS (UV 214): 289.0 (M+H) ⁺ ；RT＝1.617min；98.35％purity。

Example 5

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and tetrahydrofuran (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium bisulphite (10.33 g,99.36 mmol) is dissolved in water (86.5 mL), and a small amount of sodium bisulphite is poured into the reaction for many times, and the mixture is stirred for 0.5h continuously under ice bath condition and then naturally heated to room temperature for stirring for 3h, thus obtaining yellow clarified liquid;

step 4: removing most of tetrahydrofuran by rotary evaporation;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain crude yellow solid 2.5g;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: the solid obtained by the last pulping is filtered off, and the solid is collected and dried to obtain a white solid (0.96 g, product yield 20.1%, LC-MS purity up to 100%). LC-MS (UV 214): 289.0 (M+H) ⁺ ；RT＝1.678min；100％purity。

The mole ratio of the raw material hesperetin to the reducing agent is 1:6.

example 6

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and tetrahydrofuran (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium dithionite (8.65 g,49.68 mmol) is dissolved in water (43 mL), and a small amount of sodium dithionite is poured into the reaction for many times, and the mixture is stirred for 0.5h under ice bath condition, then naturally warmed to room temperature and stirred for 3h, thus obtaining yellow clarified liquid;

step 4: removing most of tetrahydrofuran by rotary evaporation;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain crude yellow solid 4.1g;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: the solid obtained by the last pulping is filtered off, and the solid is collected and dried to obtain a white solid (0.82 g, 17.1% yield of product, 100% purity of LC-MS). LC-MS (UV 214): 289.10 (M+H) ⁺ ；RT＝1.644min；100％purity。

The mole ratio of the raw material hesperetin to the reducing agent is 1:3.

example 7

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and tetrahydrofuran (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium dithionite (14.4 g,82.8 mmol) is dissolved in water (72 mL), and a small amount of sodium dithionite is poured into the reaction for many times, and the mixture is stirred for 0.5h continuously under ice bath condition and then naturally heated to room temperature for stirring for 3h, thus obtaining yellow clarified liquid;

step 4: removing most of tetrahydrofuran by rotary evaporation;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain 3.6g of crude yellow solid;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: filtering out the solid obtained by pulping, and collecting the solidOven drying gave a white solid (1.45 g, 30.4% yield of product, 99.6% purity LC-MS). LC-MS (UV 214): 289.20 (M+H) ⁺ ；RT＝1.636min；99.6％purity。

The mole ratio of the raw material hesperetin to the reducing agent is 1:5.

example 8

The embodiment provides a synthetic method of eriodictyol, comprising the following steps:

step 1: hesperetin (5.0 g,16.56 mmol) and tetrahydrofuran (150 mL) were mixed and dissolved at room temperature;

step 2: 2-iodate acyl benzoic acid (10.2 g,36.43 mmol) was added at a time, and the mixture was stirred for 24 hours under nitrogen protection to give a dark red viscous suspension (intermediate reaction solution);

step 3: the dark red thick suspension is kept for 0.5h under ice bath condition, sodium dithionite (20.1 g,115.9 mmol) is dissolved in water (100 mL), and a small amount of sodium dithionite is poured into the reaction for many times, and the mixture is stirred for 0.5h continuously under ice bath condition and then naturally heated to room temperature for stirring for 3h, thus obtaining yellow clarified liquid;

step 4: removing most of tetrahydrofuran by rotary evaporation;

step 5: pouring saturated ammonium chloride solution (30 mL), extracting with ethyl acetate (60 mL x 3), washing the combined organic phases with saturated sodium bicarbonate solution (30 mL x 3), washing with saturated saline (20 mL x 1), drying over anhydrous sodium sulfate, filtering, and removing the solvent by rotary evaporation to obtain crude yellow solid 4.0g;

step 6: adding the crude product into a solvent with the mixing ratio of methanol to ethyl acetate of 1:10, and pulping repeatedly for three times, wherein the mass ratio of the solvent to the crude product is 6-8 mL/g;

step 7: the solid obtained by the last pulping was filtered off, the solid was collected and dried to give a white solid (1.7 g, product yield 35.5%, LC-MS purity 99.9%). LC-MS (UV 214): 289.0 (M+H) ⁺ ；RT＝1.681min；99.9％purity。

The mole ratio of the raw material hesperetin to the reducing agent is 1:7.

the present invention has been made by the above-described studies of examples 1 to 8, and the detailed results of the study on the reaction solvent, the kind of reducing agent and the amount of reducing agent used in the reaction in the present invention are shown below:

1. influence of the reaction solvent on the yield of the product

Examples 1 to 3 differ only in the reaction solvent, tetrahydrofuran was used as the reaction solvent in example 1, dioxane was used as the reaction solvent in example 2, and ethylene glycol dimethyl ether was used as the reaction solvent in example 3.

TABLE 1 influence of reaction solvent on product yield

As is clear from Table 1, the different solvents have less influence on the reaction, and tetrahydrofuran is preferable as the reaction solvent in the present invention because tetrahydrofuran can be easily removed by rotary evaporation in view of its low boiling point and can be easily worked up.

2. Influence of the kind and amount of the reducing agent on the yield of the product

Examples 1 and 4-5 differ in the specific choice of reducing agent, sodium dithionite in example 1, sodium thiosulfate in example 4 and sodium bisulfite in example 5. Examples 1 and 6-8 differ in the molar ratio of the starting material hesperetin to the reducing agent.

TABLE 2 influence of the type and amount of reducing agent on the yield of the product

As can be seen from the above table, sodium dithionite is used as the reducing agent for the reaction, the yield is highest, and sodium dithionite is economical and practical, so sodium dithionite is preferred in the present invention as the reducing agent; from the aspect of reducing agent consumption, when sodium dithionite is used as the reducing agent, the reaction yield is gradually increased along with the increase of the consumption; however, since the reaction yield does not significantly increase after the amount of the reducing agent is 6 equivalents, the amount of the reducing agent is preferably 6 equivalents in view of the problems of the reaction yield and the cost.

The foregoing describes specific embodiments of the present invention. It is to be understood that the invention is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the invention. The embodiments of the present application and features in the embodiments may be combined with each other arbitrarily without conflict.

Claims (9)

1. A method for preparing eriodictyol, comprising the steps of: the hesperetin reacts with an oxidant in a reaction solvent to obtain a reaction intermediate solution, and a reducing agent is added into the reaction intermediate solution to obtain the eriodictyol.

2. The process for producing eriodictyol according to claim 1, wherein the reaction intermediate solution is obtained by specifically: and adding the raw material hesperetin into a reaction solvent, adding an oxidant at one time, protecting a reaction system by using inert gas, and reacting for 24 hours at room temperature to complete the conversion of a reaction intermediate state, thereby obtaining a reaction intermediate state solution.

3. The process for producing eriodictyol according to claim 2, wherein the oxidizing agent is 2-iodoxybenzoic acid.

4. The process for producing eriodictyol according to claim 3, wherein the reaction solvent is at least one of tetrahydrofuran, dioxane or N, N-dimethylformamide.

5. The process for producing eriodictyol according to claim 3, wherein the ratio of the reaction solvent to the raw hesperetin is 30mL/g.

6. The process for producing eriodictyol according to any one of claims 1 to 5, wherein the step of adding a reducing agent to the intermediate solution for reaction to give eriodictyol comprises the steps of: ice bath for 0.5h, preparing aqueous solution of reducing agent, adding aqueous solution of reducing agent into the intermediate solution, continuously ice bath for 0.5h, removing ice bath, reacting for 3h at room temperature, distilling to remove reaction solvent, adding saturated ammonium chloride solution into the rest water phase, extracting with ethyl acetate, mixing organic phases, washing saturated sodium bicarbonate solution, washing saturated saline solution, drying with anhydrous sodium sulfate, distilling to remove solvent to obtain yellow solid, adding the solid into mixed solvent of methanol and ethyl acetate, repeatedly pulping for 2-3 times to obtain eriodictyol.

7. The method for producing eriodictyol according to claim 6, wherein the reducing agent is at least one of sodium dithionite, sodium hydrogen sulfite or sodium thiosulfate.

8. The process for producing eriodictyol according to claim 6, wherein the aqueous solution of the reducing agent has a concentration of 0.2g/mL.

9. The process for producing eriodictyol according to claim 6, wherein the volume ratio of methanol to ethyl acetate in the mixed solvent of methanol and ethyl acetate is 1:10.

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