A method for extracting forsythiaside B from forsythia leaves

Abstract

The present invention provides a method for extracting forsythiaside B from forsythia leaves. The present invention utilizes byproducts in the process of obtaining forsythiaside and forsythiaside A by using macroporous resin, namely, a water elution part and a low-concentration ethanol elution part to extract forsythiaside B, and then further purifies the target component and the impurity component by using two reverse phase chromatography systems of methanol-water and acetonitrile-water, so as to obtain high-purity forsythiaside B. The present invention utilizes byproducts in the process of obtaining forsythiaside and forsythiaside A by using macroporous resin to extract forsythiaside B, and fully utilizes forsythia leaf resources; and the reverse phase silica gel filler and solvent used can be reused, so as to provide an economical and feasible method for preparing high-purity forsythiaside B in large quantities.

Description

Technical Field

[0001] The invention belongs to the technical field of plant chemical separation and relates to a method for extracting forsythiaside B from forsythia leaves. Background Art

[0002] Forsythia suspensa (Thunb.) Vahl is a plant of the genus Forsythia in the family Oleaceae. The pharmacopoeia stipulates that the medicinal part is its dried fruit, which is a commonly used heat-clearing and detoxifying medicine in traditional Chinese medicine.

[0003] Studies have shown that in addition to a large amount of active ingredients such as forsythiaside and forsythiaside A, Forsythia leaves also contain forsythiaside B (CAS 81525-13-5), which belongs to the phenylethanol glycoside class. Its structural formula is shown below. Pharmacological studies have shown that it has multiple pharmacological effects such as anti-inflammatory, antibacterial, antiviral and antioxidant effects, and can treat or prevent cardiovascular diseases, and has broad application prospects.

[0004]

[0005] Traditionally, the source plant of forsythiaside B is the Chinese medicinal material Callicarpa kwuang-tungensis Chun, which is also one of the index components of Callicarpa kwuang-tungensis Chun stipulated in the Chinese Pharmacopoeia. In recent years, there are also reports and patents on the preparation of forsythiaside B from Lamiophlomis rotata (Benth.) Kudo, such as Chinese patents 200910016543.1 and 201310305644.7.

[0006] Due to the particularity of the composition and content ratio of the chemical components of traditional Chinese medicine, the aforementioned method of extracting forsythiaside B from Callicarpa elata and Du Yiwei is not applicable to the raw material of Forsythia leaf. This is because the content of Forsythiaside B in Forsythia leaf is relatively low, and the impurity components are relatively more, making separation and purification more difficult. It is difficult to obtain Forsythiaside B monomer with high purity by a single reverse phase filler adsorption and methanol-water system elution purification method.

[0007] There are relevant literature and patent reports on methods for extracting natural products such as forsythiaside, forsythiaside, forsythiaside A from Forsythia leaves, such as Chinese patents 201910048775.9, 201310052192.6, and 201110209731.3, but none of the above reports include methods for extracting forsythiaside B from Forsythia leaves. This is partly because Forsythia leaves contain forsythiaside and forsythiaside A as the main components, and the content of forsythiaside B is relatively low. Moreover, due to its high polarity, it mainly exists in the eluent of the impurity removal process of water and low-concentration organic solvents, and is not easily noticed and utilized. In addition, since the components of the above-mentioned elution part are complex and difficult to separate and purify, the purification methods in the aforementioned related patents are not suitable for the separation and purification of forsythiaside B in Forsythia leaves. Summary of the invention

[0008] In order to solve the above problems of the prior art, the present invention provides a method for extracting forsythiaside B from Forsythia suspensa leaves, which can obtain high-purity forsythiaside B.

[0009] The present invention is achieved through the following technical solutions:

[0010] A method for extracting forsythiaside B from Forsythia suspensa leaves comprises the following steps:

[0011] (1) Preparation of Forsythia suspensa leaf extract

[0012] The forsythia leaf is crushed, extracted with a methanol solution under hot reflux, concentrated to remove the methanol, diluted with water, and then separated to obtain a forsythia leaf extract;

[0013] (2) Isolation of Forsythiaside B

[0014] Primary separation: the obtained Forsythia suspensa leaf extract is subjected to adsorption separation by using a macroporous resin, firstly eluted with water, collecting the water eluate containing forsythiaside B, then eluted with 10%-20% ethanol, collecting the ethanol eluate containing forsythiaside B, combining the water eluate containing forsythiaside B and the ethanol eluate, removing the ethanol, and obtaining a primary separation solution containing forsythiaside B;

[0015] Secondary separation: the primary separation solution containing forsythiaside B is separated by adsorption with a macroporous resin, first eluted with water, then eluted with 50% to 75% ethanol, the ethanol eluate containing forsythiaside B is collected, and the ethanol is removed to obtain a crude product of forsythiaside B;

[0016] (3) Purification of Forsythiaside B

[0017] Primary purification: dissolving the crude product of Forsythiaside B in a methanol-water solution and adding activated carbon for decolorization, separating the activated carbon after decolorization, separating the obtained liquid by reverse phase silica gel column chromatography, eluting with methanol-water, collecting the eluate with a purity of 60%-90% and the eluate with a purity of more than 90% forsythiaside B, removing methanol and water from the eluate with a purity of more than 90%, and obtaining Forsythiaside B;

[0018] Secondary purification: The eluate with a purity of 60%-90% of Forsythiaside B is separated by reverse phase silica gel column chromatography, eluted with acetonitrile-acetic acid aqueous solution, and the eluate with a purity of more than 90% of Forsythiaside B is collected. The acetonitrile and water are removed from the obtained eluate to obtain Forsythiaside B.

[0019] Preferably, in step (2), during the secondary separation process, collecting the ethanol eluate specifically comprises: starting from when the purity of forsythiaside B in the ethanol eluate is greater than or equal to 30%, and stopping collecting when the mass concentration ratio of forsythiaside B to forsythiaside A in the ethanol eluate is 2-1.

[0020] Preferably, in step (2), the macroporous resin is D101 macroporous resin.

[0021] Preferably, in the secondary purification process of step (3), acetonitrile and water are removed from the obtained eluate to obtain forsythiaside B. The specific method is: the obtained eluate is vacuum concentrated to remove acetonitrile, then dehydrated and deacidified using a macroporous resin, eluted with ethanol, the ethanol eluate is collected, and ethanol is removed to obtain forsythiaside B.

[0022] Preferably, in step (3), the acetonitrile-acetic acid aqueous solution is specifically 15% acetonitrile-0.05% acetic acid aqueous solution.

[0023] Preferably, in step (3), the methanol-water used is 30% methanol-water.

[0024] Preferably, in steps (2) and (3), HPLC is used for detection during elution.

[0025] Preferably, the chromatographic conditions for HPLC detection are: octadecylsilane bonded silica gel as filler; acetonitrile-0.1% phosphoric acid aqueous solution as mobile phase; detection wavelength of 330 nm; volume flow rate of 1 mL / min; column temperature of 35° C.; injection volume of 10 μL.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The inventors of the present invention found in experimental studies on extracting forsythiaside and other components from Forsythia leaves that although the content of forsythiaside B in Forsythia leaves is low, the enrichment effect of macroporous resins showed that both the water-washed impurity-removing elution fraction and the low-concentration ethanol elution fraction contained a large amount of forsythiaside B. Therefore, considering the economical use of resins, the method of the present invention mainly utilizes the byproducts in the process of obtaining forsythiaside and forsythiaside A using macroporous resins, namely, the water-washed fraction and the low-concentration ethanol elution fraction, to extract forsythiaside B. For Forsythiaside B, when a large sample load or saturated sample load is used, more Forsythiaside B will appear in the water wash, that is, this phenomenon mainly exists in the primary separation process, because the sample load of the primary separation also contains a large amount of Forsythiaside A and Forsythiaside and other components that have competitive adsorption with Forsythiaside B, Forsythiaside A and Forsythiaside are more easily adsorbed on the resin, so that Forsythiaside B is eluted by water. Therefore, in the primary separation, the water eluate and ethanol eluate containing Forsythiaside B are collected; in the secondary separation process, the sample load mainly contains Forsythiaside B, the ratio of sample to resin is small, and the adsorption and analysis of the resin are more suitable for general resin separation principles and methods, that is, in the secondary separation process, Forsythiaside B does not exist in the water eluate, but mainly exists in the ethanol eluate, so only the ethanol eluate containing Forsythiaside B is collected in the secondary separation process. The obtained eluent has removed most of the fat-soluble and water-soluble impurities (fat-soluble impurities including a large amount of pigments, oily components, forsythiaside, forsythiaside A, etc. are retained in the resin column during the primary separation and require high-concentration ethanol to be eluted, while water-soluble impurities will flow out with water during the loading process). After the obtained eluent is concentrated, it is further purified by using two reverse phase chromatography systems of methanol-water and acetonitrile-water to separate target components and impurity components at different degrees of separation. Methanol-water elution can remove most of the impurities, and acetonitrile-water can remove impurities such as forsythiaside A, thereby obtaining high-purity forsythiaside B. The present invention utilizes the byproducts in the process of obtaining forsythiaside and forsythiaside A by using macroporous resin to extract forsythiaside B, making full use of the resources of Forsythia leaf; and the reverse phase silica gel filler and solvent used can be reused, providing an economical and feasible method for preparing high-purity forsythiaside B in large quantities.

[0028] Furthermore, the present invention collects more than 30% of forsythiaside B in the two separation processes to obtain an ethanol solution with a mass concentration ratio of forsythiaside B to forsythiaside A of 2 to 1, which can not only fully improve the yield of forsythiaside B, but also help to ensure the yield of other components such as forsythiaside A.

[0029] Furthermore, the purified forsythiaside B eluate is dehydrated and deacidified using a macroporous resin, which can effectively avoid the degradation of the target component and improve the purity of the final product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the HPLC chart of the first separation solution of Forsythiaside B in Example 1;

[0031] Figure 2 This is the HPLC chart of the crude product of Forsythiaside B obtained by secondary separation in Example 1;

[0032] Figure 3 This is the HPLC chart of Forsythiaside B purified by reverse phase chromatography (methanol-water system) in Example 1;

[0033] Figure 4 HPLC chart of forsythiaside B purified by reverse phase chromatography (acetonitrile-acetic acid water system) in Example 1

[0034] Figure 5 Forsythiaside B obtained by two purifications in Example 1 1 HNMR spectrum; DETAILED DESCRIPTION

[0035] In order to further understand the present invention, the present invention is described below in conjunction with embodiments. These descriptions are only to further explain the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0036] The present invention discloses a method for extracting forsythiaside B from forsythia leaves, which comprises the following steps:

[0037] (1) Primary separation

[0038] The forsythia leaf is crushed into coarse powder, extracted with 75% methanol under hot reflux, concentrated to remove methanol, diluted with water, stirred evenly, and then allowed to stand, centrifuged to obtain a forsythia leaf extract, and the obtained forsythia leaf extract is subjected to adsorption separation using D101 C macroporous resin, first eluted with water, and the elution process is monitored by HPLC, the water eluate containing forsythiaside B is collected, and then eluted with 10%-20% ethanol 1-3BV, preferably 15% ethanol 2BV, the ethanol eluate containing forsythiaside B is collected, the eluate containing forsythiaside B is combined, and the organic solvent ethanol is recovered and removed to obtain a primary separation liquid containing forsythiaside B. In the primary separation liquid, the mass concentration ratio of forsythiaside B to forsythiaside A is 0.8-1.

[0039] (2) Secondary separation

[0040] The primary separation liquid containing forsythiaside B is adsorbed on an activated macroporous resin containing water for secondary separation, preferably D101 macroporous resin; 2-3 BV of water and 2-3 BV of 50%-75% (this step is equivalent to dehydration and concentration) ethanol are used for elution, preferably, 2 BV of water is used for elution and impurity removal, and then 50% ethanol is used for elution, and the elution process is monitored by HPLC method, and the ethanol eluate is collected, and the collection starts when the purity of forsythiaside B in the eluate is greater than or equal to 30%, and the collection is stopped when the mass concentration ratio of forsythiaside B to forsythiaside A in the eluate is 2-1, to obtain the secondary separation liquid containing forsythiaside B, and the solvent ethanol is removed by vacuum concentration to obtain a crude forsythiaside B with a content of 30%-50%.

[0041] (3) Purification of Forsythiaside B

[0042] Primary purification: The crude product of forsythiaside B was dissolved in 20% methanol solution and activated carbon was added for decolorization. The activated carbon preferably used was 100-200 mesh. After filtration, the mixture was purified by C 18 Reverse phase silica gel column chromatography separation, methanol-water elution (preferably 30% methanol-water), while monitoring the elution process by HPLC, collecting the eluate with a purity of 60%-90% and the eluate with a purity of more than 90%, removing the solvent from the eluate with a purity of more than 90%, and obtaining Forsythiaside B with a purity of more than 96%;

[0043] Secondary purification: The eluate with a purity of 60%-90% of forsythiaside B during the primary purification process was collected and subjected to secondary purification using the C 18 The product is purified by reverse phase silica gel column for secondary purification, using acetonitrile-acetic acid aqueous solution (preferably 15% acetonitrile-0.05% acetic acid aqueous solution) as the eluent, and the elution process is monitored by HPLC. The eluate with a purity of more than 90% of Forsythiaside B is collected, and the solvents acetonitrile and water are removed to obtain Forsythiaside B with a purity of more than 96%.

[0044] Preferably, the eluate collected from the secondary purification is vacuum concentrated to remove acetonitrile, then dehydrated and deacidified using a macroporous resin, then eluted with ethanol, 1 to 2 BV of the ethanol eluate is collected, and the solvent ethanol is removed to obtain Forsythiaside B.

[0045] The HPLC detection conditions in the above process of extracting forsythiaside B from Forsythia suspensa leaves are as follows:

[0046] The HPLC chromatograph was a Shimadzu LC-20AT high performance liquid chromatograph equipped with LC-20AT dual pumps, SPD-M20A diode array detector, SIL-20A automatic sampler, LabSolution workstation, etc.;

[0047] Chromatographic conditions: octadecylsilane bonded silica gel as filler; mobile phase acetonitrile-0.1% phosphoric acid aqueous solution (10:90); detection wavelength 330nm; volume flow rate 1mL / min; column temperature 35°C; injection volume 10μL.

[0048] Example 1

[0049] Primary separation: 100 kg of Forsythia leaves (Long County, Shaanxi Province) were crushed into coarse powder, extracted with 10 times the amount (V / W) of 75% methanol under hot reflux, concentrated to remove methanol, diluted with water to about 100 L, stirred thoroughly and allowed to stand, centrifuged to obtain a Forsythia leaf loading solution, adsorbed on a stainless steel chromatography column (25 cm*180 cm) filled with D101 macroporous resin, first washed with 150 L of water, then eluted with 150 L of 15% ethanol, and the elution process was monitored by HPLC, and a total of about 100 L of water eluate and ethanol eluate containing forsythiaside B were collected (at this time, forsythiaside and forsythiaside A were retained in the resin column, and the corresponding components could be eluted with ethanol-water systems of different proportions), and vacuum concentrated to remove ethanol to obtain 20 L of a primary separation solution of forsythiaside B (tested, the mass concentrations of forsythiaside B and forsythiaside A in the primary separation solution were 8.5 mg / mL and 10.5 mg / mL, respectively).

[0050] Secondary separation: 10 L of the primary separation liquid was taken and adsorbed on an activated D101 macroporous resin glass chromatography column (10 cm*150 cm) for secondary separation. First, eluted with 15 L of water (the water eluate was discarded); then eluted with 50% ethanol, and the elution process was monitored by HPLC. Collection began when the purity of forsythiaside B in the eluate was equal to 30%, and the collection was stopped when the mass concentration ratio of forsythiaside B to forsythiaside A in the eluate was 1. A total of 10 L of eluate containing forsythiaside B was collected, and after concentrating and removing the solvent, a crude forsythiaside B was obtained (the contents of forsythiaside B and forsythiaside A measured by HPLC were 35% and 30%, respectively).

[0051] Primary purification: Dissolve the crude product of forsythiaside B in 20% methanol, add appropriate amount of activated carbon for decolorization and impurity removal, filter, and load C 18 The DAC-HB 80 dynamic axial compression column purification system of the reversed phase silica gel column was used for primary purification. The purification conditions were as follows: the mobile phase was 30% methanol-water, dual wavelength detection was adopted at 254nm and 330nm, the fractions were collected and detected, the fractions with purity above 90% were combined, and after vacuum concentration, 4.2g of forsythiaside B with purity of 96.5% was obtained.

[0052] Secondary purification: Combine the 60% to 90% purity fractions, concentrate and load C 18The DAC-HB 80 dynamic axial compression column purification system of the reversed-phase silica gel column was used for secondary purification. The purification conditions were as follows: the mobile phase was 15% acetonitrile-0.05% acetic acid water, the fractions were collected and detected, the fractions with a purity of more than 90% were combined, the acetonitrile was removed by vacuum concentration, and then the fractions were dehydrated and deacidified using a macroporous resin, and then eluted with ethanol, the ethanol eluate was collected, and the solvent ethanol was removed to obtain 98.2% of forsythiaside B, a total of 15.3 g.

[0053] The typical HPLC chromatogram obtained is attached. Figure 1 , Figure 2 , Figure 3 , Figure 4 and Figure 5 , where the peak with a retention time of 10.9 min is the chromatographic peak of forsythiaside B, and the peak with a retention time of 12.5 min is the chromatographic peak of forsythiaside A;

[0054] Figure 5 Forsythiaside B obtained after two rounds of reverse phase chromatography purification 1 HNMR spectrum.

[0055] Example 2

[0056] Primary separation: 150 kg of Forsythia leaves (Long County, Shaanxi Province) were crushed into coarse powder, extracted with 10 times the amount (V / W) of 75% methanol under hot reflux, concentrated to remove methanol, and then diluted with water to about 120 L. After fully stirring, the mixture was allowed to stand and centrifuged to obtain a Forsythia leaf sample solution. The sample solution was adsorbed on a stainless steel chromatography column (35 cm*200 cm) filled with D101C macroporous resin, first washed with 200 L of water, and then eluted with 250 L of 10% ethanol. The elution process was monitored by HPLC. A total of about 150 L of water eluate and ethanol eluate containing Forsythiaside B were collected, and the ethanol was removed by vacuum concentration to obtain 30 L of Forsythiaside B primary separation solution.

[0057] Secondary separation: 10 L of the primary separation liquid was taken and adsorbed on an activated D101C macroporous resin glass chromatography column (10 cm*150 cm) for secondary separation. First, eluted with 15 L of water (the water eluate was discarded); then eluted with 60% ethanol, and the elution process was monitored by HPLC. Collection began when the purity of forsythiaside B in the eluate was equal to 30%, and collection was stopped when the mass concentration ratio of forsythiaside B to forsythiaside A in the eluate was 2. A total of 12 L of eluate containing forsythiaside B was collected, and after concentrating and removing the solvent, a crude product of forsythiaside B was obtained.

[0058] Primary purification: Dissolve the crude product of forsythiaside B in 20% methanol, add appropriate amount of activated carbon for decolorization and impurity removal, filter, and load C 18The DAC-HB 80 dynamic axial compression column purification system of the reversed-phase silica gel column was used for primary purification. The purification conditions were as follows: the mobile phase was 30% methanol-water, dual wavelength detection was adopted at 254nm and 330nm, the fractions were collected and detected, the fractions with purity above 90% were combined, and after vacuum concentration, 8.3g of forsythiaside B with purity of 96.7% was obtained.

[0059] Secondary purification: Combine the 60% to 90% purity fractions, concentrate and load C 18 The DAC-HB 80 dynamic axial compression column purification system of the reversed-phase silica gel column was used for secondary purification. The purification conditions were as follows: the mobile phase was 15% acetonitrile-0.05% acetic acid water, the fractions were collected and detected, the fractions with a purity of more than 90% were combined, the acetonitrile was removed by vacuum concentration, and the fractions were dehydrated and deacidified by using a macroporous resin, and then eluted with ethanol, the ethanol eluate was collected, and the solvent ethanol was removed to obtain 98.5% of forsythiaside B, a total of 25.2 g.

[0060] Example 3

[0061] Primary separation: 100 kg of Forsythia leaves (Long County, Shaanxi Province) were crushed into coarse powder, extracted with 10 times the amount (V / W) of 75% methanol under hot reflux, concentrated to remove methanol, and then diluted with water to about 100 L. After fully stirring, the mixture was allowed to stand and centrifuged to obtain a Forsythia leaf loading solution. The loading solution was adsorbed on a stainless steel chromatography column (25 cm*180 cm) filled with D101C macroporous resin, first washed with 150 L of water, and then eluted with 150 L of 20% ethanol. The elution process was monitored by HPLC. A total of about 90 L of water eluate and ethanol eluate containing Forsythiaside B were collected, and the ethanol was removed by vacuum concentration to obtain 18 L of a primary separation solution of Forsythiaside B.

[0062] Secondary separation: 10 L of the primary separation liquid was taken and adsorbed on an activated D101C macroporous resin glass chromatography column (10 cm*150 cm) for secondary separation. First, eluted with 15 L of water (the water eluent was discarded); then eluted with 70% ethanol, and the elution process was monitored by HPLC. Collection began when the purity of forsythiaside B in the eluent was equal to 30%, and collection was stopped when the mass concentration ratio of forsythiaside B to forsythiaside A in the eluent was 1. A total of 8 L of eluent containing forsythiaside B was collected, and after concentrating and removing the solvent, a crude product of forsythiaside B was obtained.

[0063] Primary purification: Dissolve the crude product of forsythiaside B in 20% methanol, add appropriate amount of activated carbon for decolorization and impurity removal, filter, and load C 18 The DAC-HB 80 dynamic axial compression column purification system of the reversed-phase silica gel column was used for primary purification. The purification conditions were as follows: the mobile phase was 30% methanol-water, dual wavelength detection was adopted at 254nm and 330nm, fractions were collected and detected, the fractions with purity above 90% were combined, and after vacuum concentration, 4.0 g of forsythiaside B with purity of 96.9% was obtained.

[0064] Secondary purification: Combine the 60% to 90% purity fractions, concentrate and load C 18 The DAC-HB 80 dynamic axial compression column purification system of the reversed-phase silica gel column was used for secondary purification. The purification conditions were as follows: the mobile phase was 15% acetonitrile-0.05% acetic acid water, the fractions were collected and detected, the fractions with a purity of more than 90% were combined, the acetonitrile was removed by vacuum concentration, and the fractions were dehydrated and deacidified by using a macroporous resin, and then eluted with ethanol, the ethanol eluate was collected, and the solvent ethanol was removed to obtain 98.7% of forsythiaside B, a total of 20.5 g.

[0065] The method of the present invention utilizes the existing process of using macroporous resin to separate forsythiaside and forsythiaside A from Forsythia leaves, collects the impurity-removing parts such as water washing, and then uses macroporous resin for separation, recovers the solvent to obtain a crude product of forsythiaside B with a purity of more than 30%, and then uses reversed-phase silica gel column chromatography for further purification to obtain forsythiaside B with a purity of more than 96%. On the basis of the existing extraction of natural products such as forsythiaside and forsythiaside A from Forsythia leaves, the present invention fully utilizes the elution part abandoned in the production process, uses reusable macroporous resin, reversed-phase silica gel and other fillers, obtains high-purity forsythiaside B, saves the use of Forsythia leaf resources, and is an economical and effective method for obtaining forsythiaside B.

Claims

1. A method for extracting forsythiaside B from Forsythia suspensa leaves, characterized in that: The steps include: (1) Preparation of Forsythia suspensa leaf extract The forsythia leaf is crushed, extracted with a methanol solution under hot reflux, concentrated to remove the methanol, diluted with water, and then separated to obtain a forsythia leaf extract; (2) Isolation of Forsythiaside B Primary separation: the obtained Forsythia suspensa leaf extract is subjected to adsorption separation by a macroporous resin, firstly eluted with water, collecting the water eluate containing forsythiaside B, then eluted with 10%-20% ethanol, collecting the ethanol eluate containing forsythiaside B, combining the water eluate and the ethanol eluate containing forsythiaside B, removing the ethanol, and obtaining a primary separation solution containing forsythiaside B; the macroporous resin is D101 macroporous resin; Secondary separation: the primary separation liquid containing forsythiaside B is separated by adsorption with a macroporous resin, first eluted with water, then eluted with 50%-75% ethanol, the ethanol eluate containing forsythiaside B is collected, and the ethanol is removed to obtain a crude product of forsythiaside B; the macroporous resin is D101 macroporous resin; (3) Purification of Forsythiaside B Primary purification: the crude product of forsythiaside B is dissolved in a 20% methanol-water solution and activated carbon is added for decolorization. After the decolorization is completed, the activated carbon is separated. The obtained liquid is separated by reverse phase silica gel column chromatography, eluted with 30% methanol-water, and the eluate with a purity of 60% to 90% and the eluate with a purity of more than 90% are collected. The eluate with a purity of more than 90% is free of methanol and water to obtain forsythiaside B; the reverse phase silica gel column is C 18 Reversed phase silica gel column; Secondary purification: The eluate with a purity of 60% to 90% of Forsythiaside B is separated by reverse phase silica gel column chromatography, eluted with acetonitrile-acetic acid aqueous solution, and the eluate with a purity of more than 90% of Forsythiaside B is collected. Acetonitrile and water are removed from the obtained eluate to obtain Forsythiaside B; the reverse phase silica gel column is C 18 The reverse phase silica gel column and the acetonitrile-acetic acid aqueous solution specifically used are 15% acetonitrile-0.05% acetic acid aqueous solution.

2. The method for extracting forsythiaside B from Forsythia suspensa leaves according to claim 1, characterized in that: In step (2), during the secondary separation process, the ethanol eluate is collected specifically by starting to collect when the purity of forsythiaside B in the ethanol eluate is greater than or equal to 30%, and stopping to collect when the mass concentration ratio of forsythiaside B to forsythiaside A in the ethanol eluate is 2-1.

3. The method for extracting forsythiaside B from Forsythia suspensa leaves according to claim 1, characterized in that: During the secondary purification process of step (3), acetonitrile and water are removed from the obtained eluate to obtain Forsythiaside B. The specific method is: the obtained eluate is vacuum concentrated to remove acetonitrile, then dehydrated and deacidified using a macroporous resin, eluted with ethanol, the ethanol eluate is collected, and ethanol is removed to obtain Forsythiaside B.

4. The method for extracting forsythiaside B from Forsythia suspensa leaves according to claim 1, characterized in that: In steps (2) and (3), elution is detected by HPLC.

5. The method for extracting forsythiaside B from Forsythia suspensa leaves according to claim 4, characterized in that: The chromatographic conditions for HPLC detection were as follows: octadecylsilane bonded silica gel as filler; acetonitrile-0.1% phosphoric acid aqueous solution as mobile phase; detection wavelength of 330 nm; volume flow rate of 1 mL / min; column temperature of 35 °C; injection volume of 10 µL.

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