Ginkgo biloba extract for improving microcirculation and its preparation method and application

Abstract

This invention belongs to the field of plant extraction, specifically relating to a ginkgo leaf extract for improving microcirculation, its preparation method, and its application. The preparation method of the ginkgo leaf extract includes the following steps: (1) crushing and grinding ginkgo leaves, irradiating them with an electron beam to obtain ginkgo leaf powder; (2) mixing the ginkgo leaf powder with solution A, sonicating, and filtering to obtain ginkgo leaf extract; (3) ultrafiltration of the ginkgo extract through a ceramic membrane, concentrating it to obtain a clear extract; (4) adsorbing and eluting the clear extract through a macroporous adsorption resin, then adsorbing and eluting it through a dextran gel column, concentrating, and drying to obtain the ginkgo leaf extract. In step (2), solution A is a mixed solution of ethanol, L-cysteine, dodecyl hydroxypropyl sulfobetaine, and water. This invention, through a specific preparation method, can effectively increase the yield of the active ingredients in the extract, which can significantly improve microcirculation on the body surface.

Description

Technical Field

[0001] This invention belongs to the field of plant extraction, specifically relating to a ginkgo leaf extract for improving microcirculation, its preparation method, and its application. Background Technology

[0002] Microcirculation refers to the blood circulation between arterioles and venules. The basic function of microcirculation is the exchange of substances between blood and tissue fluid. Under normal circumstances, the blood flow in microcirculation is adapted to the metabolic level of tissues and organs, ensuring adequate blood perfusion to each organ and regulating the amount of blood returning to the heart.

[0003] Microcirculatory disorders refer to the morphological and functional disturbances at the microcirculatory level. Under the influence of pathogenic factors, the systemic or local microcirculatory perfusion becomes incompatible with the needs of the tissue, the perfusion rate is significantly reduced, tissue ischemia and hypoxia occur, tissue metabolic disorders occur, and further a series of changes such as tissue degeneration and necrosis and functional failure occur.

[0004] Chinese invention patent application CN110090211A discloses the use of chlorophyll derivatives to improve microcirculation disorders. Chlorophyll derivatives, such as chlorophyll extract and silkworm excrement extract, have good therapeutic effects on improving microcirculation disorders in various parts of the body and overall microcirculation. These chlorophyll derivatives can also comprehensively prevent and improve microcirculation disorders in the whole body and specific parts of the body through their effects at multiple stages. Chinese invention patent application CN101485740A discloses a drug for improving microcirculation and its preparation method. It involves weighing out Salvia miltiorrhiza, Paeonia lactiflora, Astragalus membranaceus, Hirudo medicinalis, Pheretima aspergillum, and Leonurus japonicus, adding an appropriate amount of water, decocting them into a mixture, and then cooling it to obtain the finished product, which is then bottled and sealed for later use. After concentration and further processing, it can be made into pills, granules, powders, tablets, and capsules for convenient patient administration. Chinese invention patent application CN113116797A discloses a composition for improving microcirculation and its preparation method. This composition comprises the following raw materials in parts by weight: 10-20 parts of Saposhnikovia divaricata, 5-10 parts of Ligusticum chuanxiong, 3-8 parts of Prunus persica, 10-15 parts of Salvia miltiorrhiza, 5-10 parts of Paeonia lactiflora, 1-5 parts of Corydalis yanhusuo, 1-2 parts of Dictamnus dasycarpus, 1-2 parts of Cibotium barbarum, and 1-2 parts of Zingiber officinale (dried ginger). It has the effect of improving microcirculation; however, due to the complexity and diversity of its components and the significant interactions between them, its efficacy needs further improvement.

[0005] Ginkgo leaves are neutral in nature, with a sweet, bitter, and astringent taste. They enter the heart and lung meridians and have the effects of astringing the lungs, relieving asthma, promoting blood circulation, removing blood stasis, and relieving pain. Ginkgo leaves contain complex chemical components, with the main bioactive components including flavonoids, ginkgolides, and organic acids. Among them, the main aglycones of flavonoids are quercetin, kaempferol, and isorhamnetin, which have good antioxidant activity. Terpenoids mainly include ginkgolide A, ginkgolide B, ginkgolide C, and ginkgolide, which are natural platelet-activating factor (PAF) receptor antagonists, thus exhibiting good anticoagulant effects. Furthermore, ginkgo leaf extract can dilate coronary arteries, increase cerebral blood flow, and antagonize platelet-activating factor, potentially treating various diseases caused by vascular aging and insufficient cerebral blood supply. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a ginkgo leaf extract for improving microcirculation, its preparation method, and its application.

[0007] To achieve the above-mentioned objectives of this invention, the specific technical solution adopted by this invention is as follows:

[0008] A method for preparing a ginkgo leaf extract that improves microcirculation includes the following steps:

[0009] (1) Ginkgo leaves were crushed, ground, and irradiated with an electron beam to obtain ginkgo leaf powder;

[0010] (2) Ginkgo leaf powder is mixed with solution A, sonicated, and filtered to obtain ginkgo leaf extract;

[0011] (3) The ginkgo extract was ultrafiltered through a ceramic membrane and concentrated to obtain a clear extract;

[0012] (4) The extract was adsorbed and eluted by macroporous adsorption resin, then adsorbed and eluted by dextran gel column, concentrated and dried to obtain ginkgo leaf extract.

[0013] In step (2), solution A is a mixed solution of ethanol, L-cysteine, dodecyl hydroxypropyl sulfobetaine and water.

[0014] Preferably, the intensity of the electron beam irradiation in step (1) is 8-12 kGy, and the irradiation time is 3-5 min.

[0015] Preferably, solution A in step (2) is composed of 50%-60% ethanol, 1.0%-2.5% L-cysteine, 0.2%-0.5% dodecyl hydroxypropyl sulfobetaine and the balance water, by mass percentage.

[0016] Preferably, in step (2), the mass ratio of ginkgo leaf powder to solution A is 1:10-20, the frequency of ultrasound is 20kHz-40kHz, and the ultrasound time is 30-50min.

[0017] Preferably, the molecular cutoff of the ceramic membrane ultrafiltration in step (3) is 8000-12000, and it is concentrated to a relative density of 1.08-1.12.

[0018] Preferably, the macroporous adsorption resin in step (4) is of type HPD100A, and the dextran gel is of type SephadexLH-60.

[0019] Preferably, after the macroporous adsorption resin adsorbs in step (4), it is first eluted with a dilute hydrochloric acid solution with a pH of 5.0-6.0, then eluted with pure water until the eluent is neutral, and then eluted with an ethanol solution with a volume fraction of 45%-55%, and the ethanol eluent is collected. The elution flow rate is 1-3 mL / min.

[0020] More preferably, in step (4), the mass ratio of the macroporous adsorption resin to the clear paste is 10-15:1, the mass ratio of the dilute hydrochloric acid to the clear paste is 5-8:1, and the mass ratio of the ethanol solution to the clear paste is 15-18:1.

[0021] Preferably, after the dextran gel column adsorption in step (4), it is eluted with an ethanol aqueous solution containing citric acid, wherein the mass fraction of ethanol in the ethanol aqueous solution is 30%-45% and the mass fraction of citric acid is 0.5%-1.5%.

[0022] More preferably, the amount of the ethanol aqueous solution containing citric acid is 2-3 BV.

[0023] The present invention also relates to a ginkgo leaf extract prepared by the above preparation method, wherein, by mass percentage, the ginkgo leaf extract contains ≥24% total flavonol glycosides, ≥8% total lactones, and less than 1 ppm total ginkgolic acid.

[0024] Preferably, the peak area ratio of quercetin, kaempferol and isorhamnetin in the total flavonol glycosides is 4-5:4.5-5:1-2.

[0025] More preferably, the peak area ratio of quercetin, kaempferol and isorhamnetin in the ginkgo leaf extract is 5:5:2.

[0026] This invention also relates to the use of the ginkgo leaf extract prepared by the above-described preparation method or the use of the above-described ginkgo leaf extract in the preparation of health products or drugs for improving microcirculation.

[0027] The present invention also relates to a health product or drug for improving microcirculation, wherein the health product or drug comprises ginkgo leaf extract prepared by the above preparation method or the above ginkgo leaf extract.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention uses a specific preparation method and a specific solution for ultrasonic extraction during the extraction process, which can effectively increase the yield of the effective components of the extract.

[0030] (2) In the preparation process of the extract, the extract of ginkgo leaves is purified and separated by a combination of macroporous resin and gel column treatment. On the one hand, it can effectively increase the separation efficiency of effective components in the extract and improve the extraction efficiency of quercetin, kaempferol and isorhamnetin. On the other hand, the efficacy of the extract is further increased and can significantly improve microcirculation. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are not intended to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0032] Example 1

[0033] A method for preparing a ginkgo leaf extract that improves microcirculation, comprising the following steps:

[0034] (1) Ginkgo leaves were crushed, ground, and irradiated with an electron beam of 10 kGy for 4 min to obtain ginkgo leaf powder.

[0035] (2) Ginkgo leaf powder with a mass ratio of 1:15 was mixed with solution A (by mass percentage, solution A consisted of 55% ethanol, 2.0% L-cysteine, 0.3% dodecyl hydroxypropyl sulfobetaine and the remainder water), sonicated for 40 min at a frequency of 30 kHz, and then filtered to obtain ginkgo leaf extract.

[0036] (3) The ginkgo extract was ultrafiltered through a ceramic membrane with a molecular weight cutoff of 10,000 and then concentrated to a relative density of 1.10 to obtain a clear extract;

[0037] (4) The extract was adsorbed onto HPD100A macroporous adsorption resin, then eluted with dilute hydrochloric acid solution at pH 5.5, followed by elution with pure water until the eluent was neutral, and then eluted with 50% ethanol solution. The ethanol eluent was collected, and the elution flow rate was 2 mL / min. The mass ratio of macroporous adsorption resin to extract was 12:1, the mass ratio of dilute hydrochloric acid to extract was 6:1, and the mass ratio of ethanol solution to extract was 16:1. The ethanol eluent was then adsorbed onto a Sephadex LH-60 dextran gel column and eluted with an ethanol-water solution containing citric acid (the ethanol-water solution contained 35% ethanol and 1.0% citric acid). The volume of the ethanol-water solution containing citric acid was 2.5 BV, and the elution flow rate was 2 mL / min. The extract was concentrated and dried to obtain the Ginkgo biloba extract.

[0038] Example 2

[0039] A method for preparing a ginkgo leaf extract that improves microcirculation, comprising the following steps:

[0040] (1) Ginkgo leaves were crushed, ground, and irradiated with an electron beam of 8 kGy for 5 min to obtain ginkgo leaf powder.

[0041] (2) Ginkgo leaf powder with a mass ratio of 1:10 was mixed with solution A (by mass percentage, solution A consisted of 50% ethanol, 2.5% L-cysteine, 0.2% dodecyl hydroxypropyl sulfobetaine and the remainder water), sonicated for 30 min at a frequency of 40 kHz, and filtered to obtain ginkgo leaf extract.

[0042] (3) The ginkgo extract was ultrafiltered through a ceramic membrane with a molecular weight cutoff of 8000 and then concentrated to a relative density of 1.08 to obtain a clear extract;

[0043] (4) The extract was adsorbed onto HPD100A macroporous adsorption resin, then eluted with dilute hydrochloric acid solution at pH 5.0, and then eluted with pure water until the eluent was neutral. Then, it was eluted with 45% ethanol solution and the ethanol eluent was collected. The elution flow rate was 1 mL / min. The mass ratio of macroporous adsorption resin to extract was 10:1, the mass ratio of dilute hydrochloric acid to extract was 5:1, and the mass ratio of ethanol solution to extract was 15:1. The ethanol eluent was then adsorbed onto a Sephadex LH-60 dextran gel column and eluted with an ethanol-water solution containing citric acid (the mass fraction of ethanol in the ethanol-water solution was 30%, and the mass fraction of citric acid was 0.5%). The volume of the ethanol-water solution containing citric acid was 2 BV, the elution flow rate was 1 mL / min, the extract was concentrated, and dried to obtain the Ginkgo biloba extract.

[0044] Example 3

[0045] A method for preparing a ginkgo leaf extract that improves microcirculation, comprising the following steps:

[0046] (1) Ginkgo leaves were crushed, ground, and irradiated with an electron beam of 12 kGy for 3 min to obtain ginkgo leaf powder.

[0047] (2) Ginkgo leaf powder at a mass ratio of 1:20 was mixed with solution A (by mass percentage, solution A consisted of 60% ethanol, 1.0% L-cysteine, 0.5% dodecyl hydroxypropyl sulfobetaine and the remainder water), sonicated for 50 min at a frequency of 20 kHz, and filtered to obtain ginkgo leaf extract.

[0048] (3) The ginkgo extract was ultrafiltered through a ceramic membrane with a molecular weight cutoff of 12,000 and then concentrated to a relative density of 1.12 to obtain a clear extract;

[0049] (4) The extract was adsorbed onto HPD100A macroporous adsorption resin, then eluted with dilute hydrochloric acid solution at pH 6.0, and then eluted with pure water until the eluent was neutral. Then, it was eluted with 55% ethanol solution and the ethanol eluent was collected. The elution flow rate was 3 mL / min. The mass ratio of macroporous adsorption resin to extract was 15:1, the mass ratio of dilute hydrochloric acid to extract was 8:1, and the mass ratio of ethanol solution to extract was 18:1. The ethanol eluent was then adsorbed onto a Sephadex LH-60 dextran gel column and eluted with an ethanol-water solution containing citric acid (the mass fraction of ethanol in the ethanol-water solution was 45%, and the mass fraction of citric acid was 1.5%). The volume of the ethanol-water solution containing citric acid was 3 BV, the elution flow rate was 3 mL / min, the extract was concentrated, and dried to obtain the Ginkgo biloba extract.

[0050] Comparative Example 1

[0051] A method for preparing a ginkgo leaf extract that improves microcirculation differs from Example 1 only in that, by mass percentage, solution A in step (2) consists of 55% ethanol, 2.3% L-cysteine, and the remainder water.

[0052] Comparative Example 2

[0053] A method for preparing a ginkgo leaf extract that improves microcirculation differs from Example 1 only in that, by mass percentage, solution A in step (2) consists of 55% ethanol, 2.3% dodecyl hydroxypropyl sulfobetaine and the remainder water.

[0054] Comparative Example 3

[0055] A method for preparing a ginkgo leaf extract that improves microcirculation differs from Example 1 only in that the HPD100A macroporous adsorption resin in step (4) is replaced with the D101 macroporous adsorption resin.

[0056] Comparative Example 4

[0057] A method for preparing a ginkgo leaf extract that improves microcirculation differs from Example 1 only in that, in step (4), the extract is adsorbed onto a Sephadex LH-60 dextran gel column and eluted with a 35% ethanol aqueous solution.

[0058] Comparative Example 5

[0059] A method for preparing a ginkgo leaf extract that improves microcirculation differs from Example 1 only in that, in step (1), the ginkgo leaves are pulverized and ground, and then irradiated with an electron beam of 5 kGy for 10 min.

[0060] Content determination

[0061] The contents of total flavonol glycosides, ginkgolides and ginkgolic acid were determined according to the determination method of Ginkgo biloba extract in the 2020 edition of the Chinese Pharmacopoeia. The peak area ratios of quercetin, kaempferol and isorhamnetin in the total flavonol glycosides were further determined. The results are shown in Table 1 below.

[0062] Table 1 Measurement Results

[0063]

[0064]

[0065] Long-term toxicity tests in animals

[0066] Rats were fed the Ginkgo biloba extract powder product from Example 1 of this invention. Three experimental groups were fed to rats at doses of 140 mg / kg, 65 mg / kg, and 30 mg / kg, respectively. The results were compared with a blank control group (no drug administration) for 60 days, and the following results were obtained:

[0067] In terms of weight, blood routine, liver function, and kidney function, there were no significant differences between the three experimental groups and the blank control group, and no obvious pathological morphological damage was found in any of them. This indicates that the Ginkgo biloba extract of the present invention has few toxic side effects and can be used for long-term treatment of cardiovascular and cerebrovascular diseases.

[0068] Efficacy trials for improving microcirculation

[0069] Test Example 1

[0070] 1. Laboratory animals

[0071] 120 clean-grade Wistar rats (55 in total, half male and half female) were selected, with a weight of 220±20g.

[0072] 2. Grouping and administration

[0073] Grouping: normal control group, model group, positive drug group, Examples 1-4 and Comparative Examples 1-5;

[0074] Dosage: The positive control group was given XueShuanXinMaiNing tablets (provided by Jilin Huakang Pharmaceutical Co., Ltd., dosage 700mg / kg BW); Examples 1-4 and Comparative Examples 1-5 were given Ginkgo biloba extract (dosage 50mg / kg BW) corresponding to each example and comparative example; the model group and the normal control group were given an equal volume of physiological saline.

[0075] 3. Modeling methods

[0076] Rats were administered the drug via gavage for 5 consecutive days. On the evening of the 4th day, food was withheld but water was allowed. On the 5th day, half an hour after gavage, rats were anesthetized with an intraperitoneal injection of sodium pentobarbital. The rats were fixed in a dorsal position, and a 2-3 cm incision was made along the midline of the abdomen. A section of the small intestine mesentery was gently pulled back to the cecal region. The rats were placed in a constant-temperature water bath filled with 37°C tabletop solution, and laid flat on a convex observation platform in the center of the bath. A fixation plate was placed on top. Video images were captured under a microscope using a camera on a constant-temperature color microcirculation microscope. The images were input into a computer via a video acquisition card, and the microcirculation observation system analyzed the captured images in real time. A fixed field of view was used to observe microvascular diameter, microvascular flow velocity, and erythrocyte flow patterns in the selected area. After these parameters stabilized, each group was injected intravenously with 10% high molecular weight dextran (HMWD) (2 ml / kg) to induce microcirculatory disturbance in the rats.

[0077] 4. Data Processing

[0078] Data processing was performed using GraphPad Prism 5.0 statistical software. Experimental data are expressed as x±s, and t-tests were used for statistical analysis to compare the two groups.

[0079] 5. Measure the changes in microvenous and microarterial diameters after HMWD administration in each drug group.

[0080] The changes in the above indicators were observed at 0 min, 5 min, 15 min, 30 min, 45 min, and 60 min, and the microcirculation diameter after drug administration was calculated. The results are shown in Tables 2 and 3.

[0081] Table 2. Changes in microvenous diameter (μm / s)

[0082] normal control group 22.50±2.37 <![CDATA[22.48±2.79 a ]]> <![CDATA[22.49±3.22 a ]]> <![CDATA[22.50±3.45 a ]]> <![CDATA[22.49±2.87 a ]]> <![CDATA[22.52±2.18 a ]]> Model group 22.76±3.26 <![CDATA[19.51±3.20 b ]]> <![CDATA[17.70±3.18 b ]]> <![CDATA[17.51±3.42 b ]]> <![CDATA[17.01±3.62 b ]]> <![CDATA[16.98±3.27 b ]]> Positive drug group 22.79±2.66 <![CDATA[20.15±2.04 c ]]> <![CDATA[20.05±2.53 c ]]> <![CDATA[19.98±2.31 c ]]> <![CDATA[19.76±2.30 c ]]> <![CDATA[19.58±2.21 c ]]> Example 1 22.46±2.31 <![CDATA[21.37±2.75 d ]]> <![CDATA[21.22±2.67 d ]]> <![CDATA[21.35±2.35 d ]]> <![CDATA[21.49±2.48 d ]]> <![CDATA[21.45±2.36 d ]]> Example 2 22.44±2.63 <![CDATA[21.40±2.20 d ]]> <![CDATA[21.12±2.03 d ]]> <![CDATA[21.06±2.44 d ]]> <![CDATA[20.96±2.09 d ]]> <![CDATA[21.01±2.71 d ]]> Example 3 22.61±2.72 <![CDATA[21.31±3.54 d ]]> <![CDATA[21.10±2.19 d ]]> <![CDATA[21.02±2.49 d ]]> <![CDATA[20.88±2.50 d ]]> <![CDATA[20.95±2.52 d ]]> Comparative Example 1 22.49±1.98 <![CDATA[20.06±2.65 c ]]> <![CDATA[19.95±2.14 c ]]> <![CDATA[19.86±3.21 c ]]> <![CDATA[19.74±2.70 c ]]> <![CDATA[19.76±2.61 c ]]> Comparative Example 2 22.60±2.05 <![CDATA[20.82±2.99 c ]]> <![CDATA[20.65±3.02 c ]]> <![CDATA[20.54±2.80 c ]]> <![CDATA[19.59±2.33 c ]]> <![CDATA[19.60±2.18 c ]]> Comparative Example 3 22.71±3.06 <![CDATA[20.08±2.17 c ]]> <![CDATA[19.87±2.75 c ]]> <![CDATA[19.72±1.96 c ]]> <![CDATA[19.61±2.90 c ]]> <![CDATA[19.65±2.14 c ]]> Comparative Example 4 22.57±2.55 <![CDATA[20.24±2.44 c ]]> <![CDATA[19.85±2.51 c ]]> <![CDATA[19.69±2.25 c ]]> <![CDATA[19.60±2.34 c ]]> <![CDATA[19.61±2.77 c ]]> Comparative Example 5 22.65±1.96 <![CDATA[20.45±2.13 c ]]> <![CDATA[19.78±2.43 c ]]> <![CDATA[19.70±2.88 c ]]> <![CDATA[19.62±2.24 c ]]> <![CDATA[19.60±2.35 c ]]>

[0083] Note: There are significant differences between different letters in the same list, P < 0.05.

[0084] Table 3. Changes in arterial diameter (μm / s)

[0085]

[0086]

[0087] Note: There are significant differences between different letters in the same list, P < 0.05.

[0088] Test Example 2

[0089] Experimental mice: 50 male essential hypertensive rats (SHR) and 5 male SD rats, all 7-8 weeks old and weighing 180-190g (from Spiford (Beijing) Biotechnology Co., Ltd.).

[0090] SHR rats were divided into 9 groups of 5 rats each: model group, positive drug group, Example 1, and comparative groups 1-5. Male SD rats served as the normal control group. Drug intervention was administered for 5 weeks.

[0091] The positive control group received XueShuanXinMaiNing tablets (provided by Jilin Huakang Pharmaceutical Co., Ltd., at a dose of 700 mg / kg BW); the Example 1 and Comparative Examples 1-5 groups received the corresponding products of Example 1 and Comparative Examples 1-5 (at a dose of 50 mg / kg BW); the model group and the control group received an equal volume (50 mg / kg BW) of physiological saline.

[0092] After the drug intervention trial, the surface blood perfusion rate of the microcirculation in the rat's ear was measured using the Moor VMS dual-channel laser Doppler flow (LDF) detection system; the results are shown in the table below:

[0093] Table 4. Microcirculation surface blood perfusion rate in the ear of rats

[0094] normal control group <![CDATA[237.5±16.3 a ]]> <![CDATA[238.9±19.2 a ]]> Model group <![CDATA[113.7±21.3 b ]]> <![CDATA[115.2±18.5 b ]]> Positive drug group <![CDATA[199.6±21.6 c ]]> <![CDATA[201.5±19.8 c ]]> Example 1 <![CDATA[278.3±23.7 d ]]> <![CDATA[280.1±22.3 d ]]> Comparative Example 1 <![CDATA[221.4±21.7 e ]]> <![CDATA[228.7±24.0 a ]]> Comparative Example 2 <![CDATA[219.6±19.0 e ]]> <![CDATA[221.2±14.6 e ]]> Comparative Example 3 <![CDATA[226.1±22.5 e ]]> <![CDATA[229.5±21.8 e ]]> Comparative Example 4 <![CDATA[230.8±11.6 e ]]> <![CDATA[231.4±17.4 e ]]> Comparative Example 5 <![CDATA[231.7±25.4 a ]]> <![CDATA[234.0±19.2 a ]]>

[0095] Note: There are significant differences between different letters in the same column, P<0.05.

[0096] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included in the technical scope of the present invention.

Claims

1. A method for preparing a ginkgo leaf extract that improves microcirculation, characterized in that, Includes the following steps: (1) Ginkgo leaves are crushed, ground, and irradiated with an electron beam to obtain ginkgo leaf powder; (2) Ginkgo leaf powder is mixed with solution A, sonicated, and filtered to obtain ginkgo leaf extract; (3) The ginkgo extract was ultrafiltered through a ceramic membrane and concentrated to obtain a clear extract; (4) The extract was adsorbed and eluted by macroporous adsorption resin, then adsorbed and eluted by dextran gel column, concentrated and dried to obtain ginkgo leaf extract. In step (1), the intensity of the electron beam irradiation is 8-12 kGy and the irradiation time is 3-5 min. In step (2), solution A is a mixed solution of ethanol, L-cysteine, dodecyl hydroxypropyl sulfobetaine and water; The macroporous adsorption resin mentioned in step (4) is of type HPD100A, and the dextran gel is of type SephadexLH-60. After adsorption by the macroporous adsorption resin in step (4), the resin is first eluted with a dilute hydrochloric acid solution with a pH of 5.0-6.0, then eluted with pure water until the eluent is neutral, and then eluted with an ethanol solution with a volume fraction of 45%-55%. The ethanol eluent is collected. The elution flow rate is 1-3 mL / min. After adsorption by the dextran gel column, the resin is eluted with an ethanol aqueous solution containing citric acid. The ethanol aqueous solution contains 30%-45% ethanol and 0.5%-1.5% citric acid.

2. The preparation method according to claim 1, characterized in that, In step (2), solution A is composed of 50%-60% ethanol, 1.0%-2.5% L-cysteine, 0.2%-0.5% dodecyl hydroxypropyl sulfobetaine and the remainder water. The mass ratio of the ginkgo leaf powder to solution A is 1:10-20. The frequency of the ultrasound is 20kHz-40kHz and the duration of the ultrasound is 30-50min.

3. The preparation method according to claim 1, characterized in that, The molecular cutoff of the ceramic membrane ultrafiltration in step (3) is 8000-12000, and it is concentrated to a relative density of 1.08-1.

12.

4. A ginkgo leaf extract prepared by the method according to any one of claims 1-3, characterized in that, The ginkgo leaf extract comprises, by weight percentage: ≥24% total flavonol glycosides, ≥8% total lactones, and less than 1 ppm total ginkgolic acid.

5. The ginkgo leaf extract according to claim 4, characterized in that, The peak area ratio of quercetin, kaempferol and isorhamnetin in the total flavonol glycosides is 4-5:4.5-5:1-2.

6. A drug for improving microcirculation, characterized in that, The drug comprises the ginkgo leaf extract prepared by the preparation method according to any one of claims 1-3 or the ginkgo leaf extract according to any one of claims 4-5.

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