Preparation method of gallic acid

Abstract

The invention discloses a preparation method of gallic acid, and belongs to the technical field of extraction, separation and purification of traditional Chinese medicine components. The preparation method of gallic acid provided by the invention comprises the following steps: dispersing Chinese coriaria leaf powder in 0.25-1mol / L of aqueous alkali, reacting at 70-100 DEG C for 0.5-2 hours, and separating to obtain an alkali extraction stock solution and extracted leaf residues; continuously reacting the alkali extraction stock solution at 70-100 DEG C for 1-3 hours to obtain an alkali extraction solution; adding the extracted leaf residues into a 0.5-2 mol / L acid solution, reacting for 0.5-2 hours at the temperature of 80-110 DEG C, and separating to obtain an acid extraction stock solution; continuously reacting the acid extraction stock solution at 80-110 DEG C for 1-3 hours to obtain an acid extraction solution; and neutralizing the alkali extracting solution and the acid extracting solution to obtain a gallic acid extracting solution, and purifying the gallic acid extracting solution through macroporous adsorption resin to obtain a byproduct and gallic acid. Through a two-step hydrolysis method of low-concentration alkaline hydrolysis and acid hydrolysis, extraction of gallic acid and recovery of by-products are realized at the same time, so that simple, efficient, green, environment-friendly and low-cost preparation of gallic acid is realized.

Description

Technical Field

[0001] The present application belongs to the technical field of extraction, separation and purification of traditional Chinese medicine components, and in particular relates to a method for preparing gallic acid. Background Art

[0002] Gallic acid (GA), chemical name 3,4,5-trihydroxybenzoic acid, molecular formula C7H6O5, also known as gallic acid, gallic acid, is an organic acid. The unique structure of gallic acid determines its diverse functional activities, and it has significant antioxidant, antibacterial, antiviral, and lipid-lowering effects, making gallic acid and its derivatives widely used in food, medicine, chemical and other industries. At present, industrial production of gallic acid is mostly prepared by hydrolysis using substances rich in hydrolyzable tannins as raw materials. The most commonly used method is to prepare gallic acid by hydrolysis using a single acid or base as a catalyst. However, the traditional preparation process requires a high concentration of acid or base, and the reaction solution needs to be further neutralized, which has significant problems such as strong equipment corrosion, high environmental risks, and high production costs. Therefore, it is necessary to further improve the production process of gallic acid so that the production process of gallic acid is clean and efficient.

[0003] The prior art with application publication number CN 108929220 A discloses a method for preparing gallic acid, which comprises adding an alkaline solution to the waste liquid generated in the process of producing tea polyphenols and related catechin monomers, adding an acid after the reaction is complete, adjusting the pH to 4-6, and then purifying with a resin column and performing recrystallization technology to obtain high-purity gallic acid.

[0004] However, the above process for preparing gallic acid has the following problems: first, the raw materials used are waste liquids from the production process and cannot be obtained continuously; second, it is obtained only through high-concentration alkaline hydrolysis, which has the problems of strong equipment corrosion, great environmental risks and high production costs; third, the preparation process is complicated and not conducive to large-scale production. Summary of the invention

[0005] The present application discloses a method for preparing gallic acid, aiming to solve the technical problems of the existing gallic acid preparation process, such as the difficulty in obtaining raw materials, high production cost, high environmental risk, high safety risk and complicated preparation process.

[0006] In order to achieve the above purpose, the technical solution of this application is:

[0007] The first aspect of the present application provides a method for preparing gallic acid, the method comprising:

[0008] Dispersing Coriaria leaf powder in 0.25-1 mol / L alkaline solution, reacting at 70-100°C for 0.5-2h, and obtaining alkaline extraction stock solution and extraction leaf residue after separation;

[0009] The alkali extraction solution is reacted at 70-100° C. for 1-3 hours to obtain an alkali extraction solution;

[0010] Add the extracted leaf residue into a 0.5-2 mol / L acid solution, react at 80-110° C. for 0.5-2 h, and obtain an acid extraction stock solution after separation;

[0011] The acid extraction stock solution is reacted at 80-110° C. for 1-3 hours to obtain an acid extraction solution;

[0012] After neutralizing the alkaline extract and the acid extract, a gallic acid extract is obtained, which is purified by a macroporous adsorption resin to obtain gallic acid and by-products.

[0013] In combination with the first aspect, preferably, the alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide.

[0014] In combination with the first aspect, preferably, the concentration of the alkaline solution is 0.25-0.75 mol / L.

[0015] In combination with the first aspect, preferably, the concentration of the alkaline solution is 0.5-0.75 mol / L.

[0016] In combination with the first aspect, preferably, the acid solution is an aqueous solution of hydrochloric acid or sulfuric acid.

[0017] In combination with the first aspect, preferably, the concentration of the acid solution is 0.75-1.5 mol / L.

[0018] In combination with the first aspect, preferably, the concentration of the acid solution is 1-1.5 mol / L.

[0019] In combination with the first aspect, preferably, the macroporous adsorption resin is one of AB-8, D101, HPD100, X-5, and HP-20.

[0020] In combination with the first aspect, preferably, the step of performing macroporous adsorption resin purification comprises:

[0021] The gallic acid extract is configured into a sample solution of 1-3 mg / mL, and 2-4 BV of the sample solution is taken and added to a macroporous adsorption resin column at a flow rate of 1-4 BV / h for adsorption; 2-4 BV of distilled water is added for elution, and the eluate is concentrated and recrystallized to obtain a by-product, i.e., an inorganic salt; 3-6 BV of an ethanol solution with a concentration of 40%-80% is continuously added for elution, and the eluate is concentrated and recrystallized to obtain gallic acid and a by-product.

[0022] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present application include at least:

[0023] The preparation method of gallic acid provided in the present application uses Coriaria leaves as raw materials, and realizes the extraction of high-purity gallic acid and the recovery of inorganic salts by a two-step hydrolysis method of low-concentration alkaline hydrolysis + acid hydrolysis. First, low-concentration alkaline hydrolysis is adopted, which can not only destroy the fiber tissue structure in Coriaria leaves, but also hydrolyze and dissolve some effective ingredients in the raw materials while realizing the penetration of the hydrolyzate; secondly, low-concentration acid hydrolysis is adopted, which can not only further hydrolyze the effective ingredients that cannot be completely hydrolyzed in the raw materials, but also neutralize with alkaline solution to avoid adding additional neutralizing agents in post-treatment; finally, the extract is purified by macroporous adsorption resin purification technology, and by-products and gallic acid are recovered, thereby realizing the simple, efficient, green, environmentally friendly and low-cost extraction of gallic acid. In addition, the inorganic salts recovered from the by-products will have great application value in biomedicine, agricultural fertilizers and food additives.

[0024] At the same time, the present application uses Coriaria leaves as raw materials for the preparation of gallic acid. Coriaria leaves are leaves of the shrub Coriaria, which have a wide source, grow rapidly, have strong sustainability, and have low development and application costs, thus having significant raw material advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 This is a process flow chart for preparing gallic acid in an embodiment of the present application;

[0027] Figure 2 Preparation of A1-Gallic Acid for the Examples of the Application 1 H NMR spectra;

[0028] Figure 3 Preparation of A1-Gallic Acid for the Examples of the Application 13 C NMR spectra;

[0029] Figure 4 Liquid chromatogram of A1-gallic acid prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] In the following description of this embodiment, the term "and / or" is used to describe the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist at the same time. A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0032] In the following description of this embodiment, the term "at least one" refers to one or more, and "plurality" refers to two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0033] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0034] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0035] It should be noted that all raw materials and reagents in the examples of the present application were purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0036] In a first aspect, the present invention provides a method for preparing gallic acid, the method comprising:

[0037] Dispersing Coriaria leaf powder in 0.25-1 mol / L alkaline solution, reacting at 70-100°C for 0.5-2h, and obtaining alkaline extraction stock solution and extraction leaf residue after separation;

[0038] The alkali extraction solution is reacted at 70-100° C. for 1-3 hours to obtain an alkali extraction solution;

[0039] Add the extracted leaf residue into a 0.5-2 mol / L acid solution, react at 80-110° C. for 0.5-2 h, and obtain an acid extraction stock solution after separation;

[0040] The acid extraction stock solution is reacted at 80-110° C. for 1-3 hours to obtain an acid extraction solution;

[0041] After neutralizing the alkaline extract and the acid extract, a gallic acid extract is obtained, which is purified by a macroporous adsorption resin to obtain gallic acid and by-products.

[0042] Among them, firstly, the use of low-concentration alkaline hydrolysis can not only destroy the fiber tissue structure in the Coriaria leaves, but also hydrolyze and dissolve some of the effective ingredients in the raw materials while achieving the penetration of the hydrolyzate; secondly, the use of low-concentration acid hydrolysis can not only further hydrolyze the effective ingredients that have not been completely hydrolyzed in the raw materials, but also neutralize them with the alkaline solution to avoid adding additional neutralizing agents in post-processing; finally, the extract is purified by macroporous adsorption resin purification technology, and high-purity gallic acid extraction and inorganic salt recovery are achieved at the same time, thereby achieving simple, efficient, green, environmentally friendly and low-cost extraction of gallic acid. In addition, the inorganic salts recovered from the by-products will have great application value in biomedicine, agricultural fertilizers and food additives.

[0043] At the same time, the present application uses Coriaria leaves as raw materials for the preparation of gallic acid. Coriaria leaves are leaves of the shrub Coriaria, which have a wide source, grow rapidly, have strong sustainability, and have low development and application costs, thereby achieving maximum development of plant resources and creating greater market value.

[0044] It should be noted that the present application can only use a low concentration of alkaline solution for hydrolysis first, and then use a low concentration of acid for hydrolysis. The low concentration of alkaline solution can destroy the fiber tissue structure in the mulberry leaves, and the low concentration of acid can further hydrolyze to achieve effective decomposition of tannin components.

[0045] In the embodiment of the present application, the alkaline solution is preferably an aqueous solution of sodium hydroxide or potassium hydroxide. Among them, these alkaline solutions can not only further hydrolyze the effective components in the raw materials that cannot be completely hydrolyzed by low-concentration alkaline solutions, but also neutralize with the alkaline solution, avoiding the addition of additional neutralizing agents in post-treatment, and can hydrolyze the gallic acid groups in the gallic acid group-containing compounds to generate gallic acid, which can effectively increase the amount of gallic acid in the gallic acid extract.

[0046] In the embodiment of the present application, the concentration of the alkaline solution is preferably 0.25-0.75 mol / L, more preferably 0.5-0.75 mol / L, for example 0.25, 0.5, 0.75 or any concentration within the range. Among them, by controlling the alkaline solution within a lower concentration range, not only can the requirements of alkaline solution hydrolysis be met, but also the production cost can be controlled, the risk of corrosion of high-concentration alkaline solution to equipment is reduced, and it is safer and more efficient.

[0047] In the embodiment of the present application, the acid solution is preferably an aqueous solution of hydrochloric acid or sulfuric acid. By using these acid solutions, not only can the effective components that cannot be completely hydrolyzed by low-concentration alkali solution in the raw material be further hydrolyzed, but also the alkali solution can be neutralized, avoiding the addition of additional neutralizing agents in post-treatment, reducing the environmental risks of acid-base waste liquid, and being cleaner and more environmentally friendly.

[0048] In the embodiment of the present application, the concentration of the acid solution is preferably 0.75-1.5 mol / L, more preferably 1-1.5 mol / L, for example 0.75, 1, 1.5 or any concentration within the range. Among them, by controlling the acid solution within a lower concentration range, not only can the requirements of acid hydrolysis be met, but also the production cost can be controlled, the risk of corrosion of the equipment by the high concentration acid solution is reduced, and it is safer and more efficient.

[0049] In the embodiment of the present application, the macroporous adsorption resin is preferably one of AB-8, D101, HPD100, X-5, and HP-20. Among them, through the selection of these macroporous adsorption resins, the gallic acid can be further purified and the purity of the product can be further improved.

[0050] In the embodiment of the present application, the step of purifying with a macroporous adsorption resin includes: configuring the gallic acid extract into a sample solution of 1-3 mg / mL, taking a sample solution of 2-4 BV in volume, and adding it to a macroporous adsorption resin column at a flow rate of 1-4 BV / h for adsorption; adding 2-4 BV of distilled water for elution, concentrating the eluate, and obtaining a by-product, namely an inorganic salt, after recrystallization; continuing to add 3-6 BV of an ethanol solution with a concentration of 40%-80% for elution, concentrating the eluate, and obtaining gallic acid after recrystallization. Among them, the inorganic salt component can be obtained by means of recrystallization, which can be recycled and reused, and the process is green and environmentally friendly. Further, adsorption purification is carried out in a macroporous adsorption resin column to purify gallic acid, which can achieve the removal of a large number of small molecular impurities in Coriolus leaves, thereby significantly improving the purity of the extract gallic acid. In addition, the purification process of the macroporous adsorption resin is simple to operate, the purification cycle is short, the efficiency is high, and it is easier to implement and promote industrialization.

[0051] It should be noted that the gallic acid product prepared in this application has high analytical purity and high total yield. After testing, the analytical purity of gallic acid is as high as 95%, and the yield is 18%.

[0052] The technical solution of the present application will be further described below in conjunction with specific embodiments.

[0053] Example 1

[0054] This embodiment provides a method for preparing A1-gallic acid, according to Figure 1 The preparation process shown specifically includes:

[0055] S101: 1 g of Coriaria leaf powder was placed in a reaction kettle, 60 mL of a 0.75 mol / L sodium hydroxide solution was added, and the mixture was reacted at 100° C. for 1 h. After centrifugal filtration, an alkali extraction stock solution and an extraction leaf residue were obtained;

[0056] S102: heating the alkali extraction solution at 100° C. for 2 h to obtain an alkali extraction solution;

[0057] S103: adding 30 mL of a 1.5 mol / L hydrochloric acid solution to the extracted leaf residue, heating at 100° C. for 1 h, and centrifuging and filtering to obtain an acid extraction stock solution;

[0058] S104: heating the acid extraction solution at 100° C. for 2 h to obtain an acid extraction solution;

[0059] S105: The alkaline extract and the acid extract are mixed and neutralized to obtain a gallic acid extract, which is purified using AB-8 macroporous adsorption resin. The gallic acid extract is configured into a 2 mg / mL sample solution, and 2BV of the sample solution is added to a macroporous adsorption resin column at a flow rate of 1BV / h for adsorption. 3BV of distilled water is added for elution, and the eluate is concentrated and recrystallized to obtain a byproduct of sodium chloride. 4BV of 70% ethanol solution is added for elution, and the eluate is concentrated and recrystallized to obtain 0.18 g of A1-gallic acid.

[0060] Example 2

[0061] This embodiment provides a method for preparing A2-gallic acid. The component ratio, preparation operation and process parameters are basically the same as those in Example 1, except that in this embodiment, 0.5 mol / L sodium hydroxide solution is used for alkaline hydrolysis and 1.5 mol / L hydrochloric acid solution is used for acid hydrolysis to obtain 0.11 g of A2-gallic acid.

[0062] Example 3

[0063] This embodiment provides a method for preparing A3-gallic acid. The component ratio, preparation operation and process parameters are basically the same as those in Example 1, except that in this embodiment, 0.25 mol / L sodium hydroxide solution is used for alkaline hydrolysis and 1.5 mol / L hydrochloric acid solution is used for acid hydrolysis to obtain 0.07 g of A3-gallic acid.

[0064] Example 4

[0065] This example provides a method for preparing A4-gallic acid. The component ratio, preparation operation and process parameters are basically the same as those in Example 1, except that in this example, 0.75 mol / L sodium hydroxide solution is used for alkaline hydrolysis and 0.75 mol / L hydrochloric acid solution is used for acid hydrolysis to obtain 0.1 g of A4-gallic acid.

[0066] Example 5

[0067] This example provides a method for preparing A5-gallic acid. The component ratio, preparation operation and process parameters are basically the same as those in Example 1, except that in this example, 0.75 mol / L sodium hydroxide solution is used for alkaline hydrolysis and 1 mol / L hydrochloric acid solution is used for acid hydrolysis to obtain 0.15 g of A5-gallic acid.

[0068] At the same time, in order to verify the comprehensive performance of the gallic acid prepared in the above examples, the present application provides the following comparative examples for detailed description.

[0069] Comparative Example 1

[0070] The component ratio, preparation operation and process parameters of B1-gallic acid prepared in the comparative example of the present application are basically the same as those in Example 1, except that in this example, only 0.75 mol / L sodium hydroxide solution is used for alkaline hydrolysis to prepare B1-gallic acid, and 0.07 g of B1-gallic acid is obtained.

[0071] Comparative Example 2

[0072] The component ratio, preparation operation and process parameters of B2-gallic acid prepared in the comparative example of the present application are basically the same as those in Example 1, except that in this example, only 1.5 mol / L hydrochloric acid solution is used for acid hydrolysis to prepare B2-gallic acid, and 0.03 g of B1-gallic acid is obtained.

[0073] The difference between Comparative Example 1 of the present application and Example 1 is that only alkaline hydrolysis is used, and the yield of gallic acid prepared is extremely low; the difference between Comparative Example 2 of the present application and Example 1 is that only acid hydrolysis is used, and the yield of gallic acid prepared is extremely low.

[0074] Comparative Example 3

[0075] The comparative example of the present application provides a preparation method for B3-gallic acid, and the component ratio, preparation operation and process parameters are basically the same as those in Example 1, except that in this embodiment, 0.25 mol / L sodium hydroxide solution is used for alkaline hydrolysis and 0.5 mol / L hydrochloric acid solution is used for acid hydrolysis to obtain 0.06 g of B3-gallic acid.

[0076] Comparative Example 4

[0077] The comparative example of the present application provides a preparation method for B4-gallic acid, and the component ratio, preparation operation and process parameters are basically the same as those in Example 1, except that in this embodiment, 1 mol / L sodium hydroxide solution is used for alkaline hydrolysis and 2 mol / L hydrochloric acid solution is used for acid hydrolysis to obtain 0.20 g of B4-gallic acid.

[0078] The difference between Comparative Example 3 of the present application and Example 1 is that the alkaline hydrolysis concentration and the acid hydrolysis concentration are both lower than the designed range values, and the yield of gallic acid prepared is low; the difference between Comparative Example 4 of the present application and Example 1 is that the alkaline hydrolysis concentration and the acid hydrolysis concentration are both higher than the designed range values, and the yield of gallic acid prepared is high, but the purity is reduced.

[0079] Comparative Example 5

[0080] This embodiment provides a method for preparing B5-gallic acid, which specifically comprises:

[0081] S301: 1 g of Coriaria leaf powder was placed in a reaction kettle, 30 mL of a 1.5 mol / L hydrochloric acid solution was added, and the mixture was heated at 100° C. for 1 h. After centrifugal filtration, an acid extraction stock solution was obtained;

[0082] S302: heating the acid extraction solution at 100° C. for 2 h to obtain an alkaline extraction solution;

[0083] S303: adding 60 mL of a sodium hydroxide solution with a concentration of 0.75 mol / L to the extracted leaf residue, reacting at 100° C. for 1 hour, and centrifugally filtering to obtain an alkali extraction stock solution and extracted leaf residue;

[0084] S304: heating the alkali extraction solution at 100° C. for 2 h to obtain an alkali extraction solution;

[0085] S305: The acid extract and the alkali extract are mixed and neutralized to obtain a gallic acid extract, which is purified using AB-8 macroporous adsorption resin. The gallic acid extract is configured into a 2 mg / mL sample solution, and 2BV of the sample solution is added to a macroporous adsorption resin column at a flow rate of 1BV / h for adsorption. 3BV of distilled water is added for elution, and the eluate is concentrated and recrystallized to obtain a byproduct of sodium chloride. 4BV of 70% ethanol solution is added for elution, and the eluate is concentrated and recrystallized to obtain 0.08 g of B5-gallic acid.

[0086] The difference between Comparative Example 5 of the present application and Example 1 is that acid hydrolysis is firstly adopted and then alkaline hydrolysis is carried out, and the yield of gallic acid prepared is lower.

[0087] The yield and purity of gallic acid extracted in the examples and comparative examples were tested. The purity of the prepared gallic acid product was determined by high performance liquid chromatography using a standard curve method, and the grams of gallic acid prepared per gram of raw material was taken as the extraction yield. The results are shown in Table 1:

[0088] Table 1 Yield and purity of gallic acid

[0089]

[0090]

[0091] Compared with Example 1, the acid and alkali concentrations of Comparative Example 3 are lower, and the other extraction and purification conditions are the same. Due to the low acid and alkali concentration, the effective ingredients in the raw materials cannot be fully hydrolyzed, so the yield of preparing gallic acid is low, and the purity of the product has certain advantages.

[0092] Compared with Example 1, the acid-base concentration of Comparative Example 4 is higher, and the other extraction and purification conditions are the same. In the preparation process, although too high an acid-base concentration can fully hydrolyze the active ingredients in the raw materials to obtain a relatively high product yield. However, due to the complex and diverse ingredients in the raw materials, too high an acid-base concentration will cause more side reactions to occur, thereby generating too many impurities in the preparation process, resulting in a low purity of the product.

[0093] In order to verify the structure of the gallic acid prepared in the examples of the present application, the A1-gallic acid prepared in the examples was characterized, and the results were as follows: Figures 2 to 4 As shown; among them, Figure 2 A1-Gallic acid 1 HNMR spectra; Figure 3 A1-Gallic acid 13 C NMR spectra; Figure 4 This is the liquid chromatogram of A1-gallic acid.

[0094] according to Figure 2 and Figure 3 As known, 10 mg of A1-gallic acid sample was taken, dissolved in 0.6 mL of deuterated dimethyl sulfoxide (DMSO-d6) reagent, and measured by nuclear magnetic resonance spectrometer to obtain: 1 HNMR (400MHz, DMSO) δ: 12.22 (s, 1H), 9.17 (s, 2H), 8.82 (s, 1H), 6.89 (s, 2H); 13 C NMR (101MHz, DMSO) δ: 167.60, 145.93, 138.01, 120.92, 108.80.

[0095] according to Figure 4 As known, the conditions for high performance liquid chromatography (HPLC) determination are: instrument: Shimadzu high performance liquid chromatograph LC-10A; chromatographic column: GS-120-5-C18, 250mm×4.6mm, 5um; wavelength: 273nm; flow rate: 1.0mL / min; injection volume: 20uL; column temperature: 30°C. Under these conditions, the retention time of gallic acid is 2.098min. Further, the chromatographic peak area corresponding to gallic acid is brought into the standard curve, and the sample purity is calculated to be 95%.

[0096] Therefore, the preparation method of gallic acid provided in the present application uses Coriaria leaves as raw materials, and uses a two-step hydrolysis method of low-concentration alkaline hydrolysis + acid hydrolysis, while extracting high-purity gallic acid and recovering inorganic salts. First, low-concentration alkaline hydrolysis is used, which can not only destroy the fiber tissue structure in Coriaria leaves, but also hydrolyze and dissolve some tannin components in the raw materials while realizing the penetration of the hydrolyzate; secondly, low-concentration acid hydrolysis is used, which can not only further hydrolyze the effective ingredients in the raw materials that are not completely hydrolyzed by low-concentration alkali solution, but also neutralize with the alkaline solution to avoid adding additional neutralizing agents in post-treatment; finally, the extract is purified by macroporous adsorption resin purification technology, and by-products and gallic acid are recovered, thereby realizing the simple, efficient, green, environmentally friendly and low-cost extraction of gallic acid. In addition, the inorganic salts recovered from the by-products will have great application value in biomedicine, agricultural fertilizers and food additives.

[0097] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0098] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions recorded in the aforementioned embodiments may still be modified, or some or all of the technical features therein may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A method for preparing gallic acid, characterized in that: The method comprises: Dispersing Coriaria leaf powder in 0.25-1 mol / L alkaline solution, reacting at 70-100°C for 0.5-2h, and obtaining alkaline extraction stock solution and extraction leaf residue after separation; The alkali extraction solution is reacted at 70-100° C. for 1-3 hours to obtain an alkali extraction solution; Add the extracted leaf residue into a 0.5-2 mol / L acid solution, react at 80-110° C. for 0.5-2 h, and obtain an acid extraction stock solution after separation; The acid extraction stock solution is reacted at 80-110° C. for 1-3 hours to obtain an acid extraction solution; The alkaline extract and the acid extract are neutralized to obtain a gallic acid extract, which is purified by a macroporous adsorption resin to obtain gallic acid and by-products.

2. The method for preparing gallic acid according to claim 1, characterized in that The alkaline solution is an aqueous solution of sodium hydroxide or potassium hydroxide.

3. The method for preparing gallic acid according to claim 1, characterized in that: The concentration of the alkaline solution is 0.25-0.75 mol / L.

4. The method for preparing gallic acid according to claim 3, characterized in that: The concentration of the alkaline solution is 0.5-0.75 mol / L.

5. The method for preparing gallic acid according to claim 1, characterized in that: The acid solution is an aqueous solution of hydrochloric acid or sulfuric acid.

6. The method for preparing gallic acid according to claim 1, characterized in that: The concentration of the acid solution is 0.75-1.5 mol / L.

7. The method for preparing gallic acid according to claim 6, characterized in that: The concentration of the acid solution is 1-1.5 mol / L.

8. The method for preparing gallic acid according to claim 1, characterized in that: The macroporous adsorption resin is one of AB-8, D101, HPD100, X-5 and HP-20.

9. The method for preparing gallic acid according to claim 1, characterized in that: The step of purifying by macroporous adsorption resin comprises: The gallic acid extract is configured into a sample solution of 1-3 mg / mL, and 2-4 BV of the sample solution is taken and added to a macroporous adsorption resin column at a flow rate of 1-4 BV / h for adsorption; 2-4 BV of distilled water is added for elution, and the eluate is concentrated and recrystallized to obtain a by-product, i.e., an inorganic salt; 3-6 BV of an ethanol solution with a concentration of 40%-80% is continuously added for elution, and the eluate is concentrated and recrystallized to obtain gallic acid and a by-product.

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