Method for producing ginkgo leaf extract

Abstract

To provide a novel method for producing a ginkgo leaf extract with a reduced ginkgolic acid content in the ginkgo leaf extract.SOLUTION: The present invention provides a method for producing a ginkgo leaf extract with a reduced ginkgolic acid content, including the steps of: (a) alkalizing a ginkgo leaf extract to precipitate a ginkgolic acid in the ginkgo leaf extract; and (b) separating the ginkgo leaf extract with a reduced ginkgolic acid content.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing a ginkgo leaf extract. [Background technology]

[0002] Ginkgo is a deciduous tree of one family, one genus, and one species, and is a dioecious plant cultivated in Asia, Europe, and North America. It has been reported that the extract of its leaves has an improving effect on dizziness, tinnitus, headache, memory loss, anxiety, etc., and the components involved in these physiological activities include flavonoids and terpenoids. On the other hand, ginkgolic acid is an allergen, so the content of ginkgo leaf extract in foods is standardized to be 5 ppm or less. Summary of the Invention [Problem to be solved by the invention]

[0003] An object of the present invention is to provide a novel method for producing ginkgo leaf extract in which the content of ginkgolic acid in the ginkgo leaf extract is reduced. [Means for solving the problem]

[0004] The present inventors have found that ginkgolic acid in a ginkgo leaf extract is precipitated by alkalizing the ginkgo leaf extract. The present invention has been completed through further investigation based on this finding, and includes the following aspects.

[0005] Section 1. (a) precipitating ginkgolic acid in a ginkgo leaf extract by alkalizing the ginkgo leaf extract; and (b) isolating the ginkgo leaf extract having a reduced content of ginkgolic acids A method for producing a ginkgo leaf extract having a reduced content of ginkgolic acid, comprising: Section 2. Item 2. The method according to item 1, wherein the alkalizing the ginkgo leaf extract in the step (a) comprises adjusting the ginkgo leaf extract to a pH of 8 to 12. Section 3. Item 3. The method according to item 1 or 2, wherein the ginkgo leaf extract having a pH of 2 to 6 is alkalized in the step (a). Section 4. Item 4. The method according to any one of Items 1 to 3, wherein the ginkgo leaf extract having a reduced ginkgolic acid content has a ginkgolic acid concentration of 15 ppm or less. Section 5. Item 5. The method according to any one of items 1 to 4, wherein the ginkgo leaf extract having a reduced content of ginkgolic acid has a flavonoid concentration of 30 ppm or more. Section 6. Item 6. The method according to any one of Items 1 to 5, wherein the ginkgo leaf extract having a reduced content of ginkgolic acid has a terpenoid concentration of 0.5 ppm or more. Section 7. (c) obtaining a ginkgo leaf extract from ginkgo leaves by solvent extraction at a temperature of 0 to 90°C; The method includes the steps (c), (a) and (b) in this order. Item 7. The method for producing according to any one of items 1 to 6. Section 8. Item 8. The method according to item 7, wherein the solvent extraction is extraction with a liquid containing water. Section 9. (d) A step of precipitating ginkgolic acid in the ginkgo leaf extract by cooling the ginkgo leaf extract. wherein said step (d) further comprises: conducted between step (c) and step (a); between step (a) and step (b); or carried out simultaneously with the step (a); Item 7. The method for producing the method according to item 7 or 8. Section 10. Item 10. A ginkgo leaf extract produced by the method according to any one of items 1 to 9. Effect of the Invention

[0006] According to the present invention, a novel method for producing ginkgo leaf extract having a reduced content of ginkgolic acid in the ginkgo leaf extract can be provided. [Brief description of the drawings]

[0007] [Figure 1] This figure shows the results of measuring the concentration of ginkgolic acid in the supernatant and precipitate when ginkgo leaf extract was alkalized (adjusted to pH 4, pH 5, pH 6, pH 7, pH 8, or pH 9) and then centrifuged. The "Original" column in the figure shows the concentration of ginkgolic acid in the ginkgo leaf extract before alkalization. [Diagram 2] This figure shows the results of measuring the concentration of ginkgolic acid in the supernatant when ginkgo leaf extract was alkalized (adjusted to pH 5, pH 7, pH 8, pH 9, or pH 11) and then centrifuged. The "Original" column in the figure shows the concentration of ginkgolic acid in the ginkgo leaf extract before alkalization. [Diagram 3] This figure shows the results of measuring the flavonoid and terpenoid concentrations in the supernatant and precipitate when ginkgo leaf extract was alkalized (adjusted to pH 4, pH 5, pH 6, pH 7, pH 8, or pH 9) and then centrifuged. The "Original" column in the figure shows the flavonoid or terpenoid concentration of the ginkgo leaf extract before alkalization. [Figure 4] This figure shows the results of measuring the concentration of ginkgolic acid in the supernatant when ginkgo leaf extract was alkalized (adjusted to pH 9) and then the supernatant was separated by filtration or centrifugation. The "Original" column in the figure shows the concentration of ginkgolic acid in the ginkgo leaf extract before alkalization. [Diagram 5] Water was added to ginkgo leaves and extraction was carried out at room temperature for 24 hours (24 hours of water extraction), at 90°C for 10 minutes (10 minutes in a hot water bath), or at 100°C for 1 hour (1 hour over direct flame), and the concentrations of ginkgolic acid, flavonoids, and terpenoids in the resulting ginkgo leaf extract were measured. This shows the results. [Figure 6]This figure shows the results of measuring the concentration of ginkgolic acids in the supernatant when ginkgo leaf extract was stirred at 2° C., stirred at room temperature or left to stand at 60° C., and then filtered or centrifuged: (A) when a ginkgo leaf extract obtained using crushed ginkgo leaves and extraction conditions at 90° C. for 10 minutes was used, (B) when a ginkgo leaf extract obtained using crushed ginkgo leaves and extraction conditions at 90-95° C. for 1 hour was used, and (C) when a ginkgo leaf extract obtained using uncrushed ginkgo leaves and extraction conditions at 90° C. for 10 minutes was used. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 1. Method for producing the ginkgo leaf extract of the present invention The method for producing the ginkgo leaf extract of the present invention comprises the steps of: (a) precipitating ginkgolic acid in a ginkgo leaf extract by alkalizing the ginkgo leaf extract; and (b) isolating the ginkgo leaf extract having a reduced content of ginkgolic acids The present invention relates to a method for producing a ginkgo leaf extract having a reduced content of ginkgolic acid, comprising:

[0009] In the method for producing ginkgo leaf extract of the present invention, alkalizing the ginkgo leaf extract in step (a) preferably involves adjusting the ginkgo leaf extract to a pH of 8 to 12, more preferably adjusting the ginkgo leaf extract to a pH of 8 to 11, and even more preferably adjusting the ginkgo leaf extract to a pH of 8 to 10.

[0010] The method of alkalizing the ginkgo leaf extract is not particularly limited, and for example, a pH adjuster can be used. As the pH adjuster, various alkaline compounds can be used, and examples of the alkaline compounds include alkali metal compounds. Examples of the alkali metal compounds include sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium carbonate (Na2CO3), and disodium hydrogen phosphate (Na2HPO4).

[0011] From the viewpoint of reducing the ginkgolic acid content in the ginkgo leaf extract, in step (a), it is preferable to alkalize the ginkgo leaf extract having a pH of 2 to 6, it is more preferable to alkalize the ginkgo leaf extract having a pH of 2 to 5, and it is even more preferable to alkalize the ginkgo leaf extract having a pH of 2 to 4.

[0012] In step (a), the ginkgo leaf extract to be alkalized preferably contains a certain amount or more of ginkgolic acid. Specifically, the concentration of ginkgolic acid in the ginkgo leaf extract to be alkalized is, for example, preferably 5 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more.

[0013] In step (a), the ginkgo leaf extract to be alkalized preferably does not contain staghorn fern and / or humus (humus mud).

[0014] In step (b), the method for separating the ginkgo leaf extract with reduced ginkgolic acid content is not particularly limited, and examples thereof include filtration, centrifugation, etc. Among them, from the viewpoint of improving the efficiency of reducing the ginkgolic acid content in the ginkgo leaf extract, the method for separating the ginkgo leaf extract with reduced ginkgolic acid content is preferably centrifugation. On the other hand, from the viewpoint of the simplicity of the operation for reducing the ginkgolic acid content in the ginkgo leaf extract, the method for separating the ginkgo leaf extract with reduced ginkgolic acid content is preferably filtration.

[0015] In step (b), when the ginkgo leaf extract with a reduced ginkgolic acid content is separated by filtration, the filtration device can be made of cotton, filter paper, membrane filter, etc. Among them, from the viewpoint of improving the efficiency of reducing the ginkgolic acid content in the ginkgo leaf extract, it is preferable to use filter paper or membrane filter with a pore size of less than 5 μm.

[0016] In the method for producing ginkgo leaf extract of the present invention, the ginkgo leaf extract having a reduced ginkgolic acid content has a ginkgolic acid concentration of preferably 15 ppm or less, more preferably 10 ppm or less, and even more preferably 5 ppm or less.

[0017] In the method for producing ginkgo leaf extract of the present invention, the flavonoid concentration of the ginkgo leaf extract with reduced ginkgolic acid content is preferably 30 ppm or more, more preferably 35 ppm or more, and even more preferably 40 ppm or more.

[0018] In the method for producing ginkgo leaf extract of the present invention, the terpenoid concentration of the ginkgo leaf extract having a reduced ginkgolic acid content is preferably 0.5 ppm or more, more preferably 1 ppm or more, and even more preferably 1.5 ppm or more.

[0019] The method for producing the ginkgo leaf extract of the present invention comprises the steps of: It is preferable to further include a step (c) of obtaining a ginkgo leaf extract from ginkgo leaves by solvent extraction at a temperature of 0 to 90°C. When the step (c) is included, it is preferable to include the steps (c), (a) and (b) in this order.

[0020] Step (c) may include separating the ginkgo leaf extract that does not contain ginkgo leaves, and step (c) preferably includes separating the ginkgo leaf extract that does not contain ginkgo leaves. Here, the ginkgo leaf extract that does not contain ginkgo leaves means the ginkgo leaf extract that does not substantially contain ginkgo leaves, and the term "substantially not containing ginkgo leaves" means that ginkgo leaves are inevitably included.

[0021] From the viewpoint of improving the efficiency of reducing the ginkgolic acid content in the ginkgo leaf extract, the extraction temperature in step (c) is preferably 0°C or higher and 90°C or lower, more preferably 15°C or higher and lower than 90°C, and even more preferably 30°C or higher and 85°C or lower.

[0022] The solvent extraction in step (c) is not particularly limited as long as it is an extraction using a solvent that can extract active ingredients such as flavonoids and terpenoids contained in ginkgo leaves, and for example, extraction with a liquid containing water can be mentioned. The content ratio of water to the entire liquid is not particularly limited, but is preferably 90% by volume or more, more preferably 93% by volume or more, and even more preferably 95% by volume or more. The water is not particularly limited, and natural water, tap water, distilled water, sterilized water, ion-exchanged water, etc. can be used.

[0023] The extraction pH in step (c) is preferably pH 2-6, more preferably pH 2-5, and even more preferably pH 2-4, from the viewpoint of improving the efficiency of reducing the ginkgolic acid content in the ginkgo leaf extract.

[0024] The method for producing the ginkgo leaf extract of the present invention comprises the steps of: (d) A step of precipitating ginkgolic acid in the ginkgo leaf extract by cooling the ginkgo leaf extract. and when step (d) is included, step (d) is preferably carried out: between step (c) and step (a); between step (a) and step (b); or simultaneously with step (a).

[0025] In the method for producing ginkgo leaf extract of the present invention, when step (d) is performed between step (c) and step (a), the method may further include a step (e) of separating ginkgo leaf extract having a reduced content of ginkgolic acid between step (d) and step (a).

[0026] In the method for producing ginkgo leaf extract of the present invention, when step (d) is carried out between steps (a) and (b), the method may further include a step (e) of isolating ginkgo leaf extract having a reduced content of ginkgolic acid between steps (a) and (d).

[0027] In step (e), the method for separating the ginkgo leaf extract with reduced ginkgolic acid content is not particularly limited, and examples thereof include filtration, centrifugation, etc. Among them, from the viewpoint of improving the efficiency of reducing the ginkgolic acid content in the ginkgo leaf extract, the method for separating the ginkgo leaf extract with reduced ginkgolic acid content is preferably centrifugation. On the other hand, from the viewpoint of the ease of the operation for reducing the ginkgolic acid content in the ginkgo leaf extract, the method for separating the ginkgo leaf extract with reduced ginkgolic acid content is preferably filtration.

[0028] In step (d), the cooling temperature of the ginkgo leaf extract is preferably 0 to 70°C, more preferably 0 to 65°C, and even more preferably 0 to 60°C, from the viewpoint of improving the efficiency of reducing the ginkgolic acid content in the ginkgo leaf extract.

[0029] In step (d), the ginkgo leaf extract can be cooled by either stirring or standing still, and from the viewpoint of increasing the cooling efficiency, it is preferable to cool the ginkgo leaf extract by stirring.

[0030] The method for producing a ginkgo leaf extract of the present invention may include other steps in addition to the steps described above. Examples of other steps include a step of concentrating the ginkgo leaf extract.

[0031] 2. Ginkgo leaf extract of the present invention The ginkgo leaf extract of the present invention is a ginkgo leaf extract produced by the above-mentioned method for producing a ginkgo leaf extract.

[0032] The ginkgolic acid concentration in the ginkgo leaf extract of the present invention is preferably 15 ppm or less, more preferably 10 ppm or less, and even more preferably 5 ppm or less.

[0033] The flavonoid concentration in the ginkgo leaf extract of the present invention is preferably 30 ppm or more, more preferably 35 ppm or more, and even more preferably 40 ppm or more.

[0034] The terpenoid concentration in the ginkgo leaf extract of the present invention is preferably 0.5 ppm or more, more preferably 1 ppm or more, and even more preferably 1.5 ppm or more.

[0035] The ginkgo leaf extract of the present invention has a reduced content of ginkgolic acid, which is an allergen, and can therefore be widely used in foods, and can be preferably used, for example, in the production of ginkgo tea. EXAMPLES

[0036] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these.

[0037] Example 1 Alkalization of ginkgo leaf extract in the production of ginkgo leaf extract > 100 ml of water was added to 5 g of crushed ginkgo leaves, and the mixture was left to stand at 90°C for 10 minutes. The ginkgo leaves were removed by filtration using filter paper (ADVANTEC (registered trademark) qualitative filter paper No. 2, manufactured by Advantec Toyo Co., Ltd.) to obtain a ginkgo leaf extract. 1M NaOH was added to 10 ml of the obtained ginkgo leaf extract (pH 3.8) to adjust the pH of the ginkgo leaf extract to 4, 5, 6, 7, 8, or 9. The ginkgo leaf extract after pH adjustment was centrifuged at 2000 rpm and 4°C for 10 minutes to separate the supernatant and precipitate (alkalinization experiment 1).

[0038] The concentration of ginkgolic acid in the supernatant and precipitate was measured. The results are shown in Figure 1. In Figure 1 and the following figures, the concentration of ginkgolic acid is calculated from the total content of five types of ginkgolic acid with different chemical structural formulas (ginkgolic acid 13:0, ginkgolic acid 15:1, ginkgolic acid 17:2, ginkgolic acid 15:0, and ginkgolic acid 17:1) in the ginkgo leaf extract. The concentration of ginkgolic acid detected in the precipitate of the ginkgo leaf extract adjusted to pH 8 and 9 was increased compared to the concentration of ginkgolic acid detected in the precipitate of the ginkgo leaf extract adjusted to pH 4, 5, 6, and 7. This result shows that the amount of ginkgolic acid precipitate increases by adjusting the ginkgo leaf extract to pH 8 to 9.

[0039] To verify whether a similar tendency was observed at more strongly alkaline conditions, ginkgo leaf extract obtained in the same manner as above using unpulverized ginkgo leaves was adjusted to pH 5, 7, 8, 9, or 11 in the same manner as above, and then centrifuged in the same manner as above to measure the ginkgolic acid concentration in the supernatant (alkalinization experiment 2). The results are shown in Figure 2. The ginkgolic acid concentration in the supernatant of ginkgo leaf extract adjusted to pH 11 was similar to that of the supernatant of ginkgo leaf extract adjusted to pH 8 and 9, and was reduced compared to the ginkgolic acid concentration in the supernatant of ginkgo leaf extract adjusted to pH 5 and 7. This result showed that the tendency for the amount of ginkgolic acid precipitation to increase was maintained even at more strongly alkaline conditions.

[0040] The above results show that adjusting the ginkgo leaf extract to an alkaline state (alkalinization) increases the amount of ginkgolic acid precipitated in the ginkgo leaf extract.

[0041] In addition, the flavonoid and terpenoid concentrations in the supernatant and precipitate of the ginkgo leaf extract (pH 4, 5, 6, 7, 8, or 9) after pH adjustment in alkalization experiment 1 were measured. The results are shown in Figure 3. In Figure 3, the flavonoid concentration is calculated from the total content of quercetin, kaempferol, and isorhamnetin in the ginkgo leaf extract. The terpenoid concentration is calculated from the total content of bilobalide, ginkgolide C, ginkgolide A, and ginkgolide B. In all cases of pH 4, 5, 6, 7, 8, and 9, no flavonoids or terpenoids were detected in the precipitate. This result indicates that flavonoids and terpenoids are not precipitated by alkalization of the ginkgo leaf extract.

[0042] Furthermore, from the pH-adjusted ginkgo leaf extract (pH 9) of alkalization experiment 1, the supernatant was separated by filtration using filter paper (ADVANTEC (registered trademark) qualitative filter paper No. 2, manufactured by Advantec Toyo Co., Ltd.) instead of the above-mentioned centrifugation, and the ginkgolic acid concentration of the supernatant was measured. The results are shown in Figure 4. The ginkgolic acid concentration of the supernatant when separated by filtration was higher than that when separated by centrifugation, but was lower than the ginkgolic acid concentration of the ginkgo leaf extract before alkalization (hereinafter, in this specification and drawings, this may be referred to as the "original ginkgolic acid concentration"). These results show that either centrifugation or filtration can be used to separate ginkgo leaf extract with a reduced ginkgolic acid content.

[0043] <Example 2. Adjustment of extraction conditions in the production of ginkgo leaf extract > 100 ml of water was added to 5 g of unpulverized ginkgo leaves, and extraction was performed under three conditions: (1) 24 hours at room temperature, (2) 10 minutes at 90°C, or (3) 1 hour at 100°C. Hereinafter, in the present specification and drawings, the above conditions (1) to (3) may be referred to as "water extraction for 24 hours," "water bath for 10 minutes," and "direct flame for 1 hour," respectively. After extraction, ginkgo leaves were removed from each sample by filtration using filter paper, and ginkgo leaf extract was obtained.

[0044] The concentrations of ginkgolic acid, flavonoids, and terpenoids in the obtained ginkgo leaf extract were measured, and the results are shown in Figure 5.

[0045] In the ginkgo leaf extract obtained, the ginkgolic acid concentration was significantly low under the conditions of (1) 24 hours at room temperature and (2) 10 minutes at 90°C, whereas it was significantly high (about 50 ppm) under the conditions of (3) 1 hour at 100°C. The ginkgolic acid concentration of the ginkgo leaf extract obtained under the conditions of (1) 24 hours at room temperature and (2) 10 minutes at 90°C was significantly lower than that of the ginkgo leaf extract obtained by the general production method (extraction conditions: 1 hour at 90-95°C). In addition, the ginkgolic acid concentration of the ginkgo leaf extract obtained under the conditions of (3) 1 hour at 100°C was about 470 times that of the ginkgo leaf extract obtained under the conditions of (1) 24 hours at room temperature. This result indicated that the ginkgo leaf extract obtained under harsh extraction conditions (1 hour at 90°C or higher) contains a large amount of ginkgolic acid.

[0046] In addition, the flavonoid concentration of the ginkgo leaf extract obtained under the conditions of (1) 24 hours at room temperature and (2) 10 minutes at 90°C was comparable to that of the ginkgo leaf extract obtained by the general production method (extraction conditions: 1 hour at 90-95°C). On the other hand, the flavonoid concentration of the ginkgo leaf extract obtained under the conditions of (3) 1 hour at 100°C was about 2.4 times that of the ginkgo leaf extract obtained under the conditions of (1) 24 hours at room temperature. This result shows that the flavonoid concentration in the ginkgo leaf extract is not affected as much by the extraction conditions such as the extraction temperature and extraction time as compared to the ginkgolic acid concentration in the ginkgo leaf extract.

[0047] Furthermore, the terpenoid concentrations of the ginkgo leaf extracts obtained under the conditions of (1) 24 hours at room temperature, (2) 10 minutes at 90°C, (3) 1 hour at 100°C, and the general production method (extraction conditions: 90-95°C for 1 hour) were similar. (3) The terpenoid concentration of the ginkgo leaf extract obtained under the condition of 100°C for 1 hour was about 1.3 times that of the ginkgo leaf extract obtained under the condition of (1) 24 hours at room temperature. This result indicates that the terpenoid concentration in the ginkgo leaf extract is hardly affected by the extraction conditions such as the extraction temperature and extraction time.

[0048] <Example 3. Cooling of ginkgo leaf extract in the production of ginkgo leaf extract > In the manufacturing method of ginkgo leaf extract in Example 2, except that the raw material uncrushed ginkgo leaves were replaced with crushed ginkgo leaves, the ginkgo leaf extract obtained under the condition of (2) 90°C for 10 minutes was (i) stirred at 2°C, (ii) stirred at room temperature, or (iii) left to stand at 60°C, and then filtered using filter paper to obtain a ginkgo leaf extract. Hereinafter, in the present specification and drawings, the cooling treatment conditions (i) to (iii) above may be expressed as "stirring at 2°C", "stirring at room temperature", and "standing at 60°C", respectively.

[0049] The concentration of ginkgolic acid in the obtained ginkgo leaf extract was measured. The results are shown in Figure 6A. The amount of ginkgolic acid in the ginkgo leaf extract obtained after (i) stirring at 2°C, (ii) stirring at room temperature, and (iii) standing at 60°C was reduced by 73%, 58%, and 45%, respectively, compared to the ginkgolic acid concentration in the ginkgo leaf extract not subjected to the cooling and subsequent filtration treatments (i) to (iii) above (hereinafter, in this specification and drawings, this may be referred to as "without cooling and filtration treatment"). This result shows that the lower the temperature of the ginkgo leaf extract, the more ginkgolic acid precipitates.

[0050] Next, we verified whether a similar tendency was observed in the ginkgo leaf extract obtained by a general manufacturing method (extraction conditions: 90-95 ° C for 1 hour). The results are shown in Figure 6B. The ginkgo leaf extract obtained by a general manufacturing method (extraction conditions: 90-95 ° C for 1 hour) was (i) stirred at 2 ° C, (ii) stirred at room temperature, or (iii) left to stand at 60 ° C, and then filtered using filter paper to obtain a ginkgo leaf extract. The concentration of ginkgolic acid in the obtained ginkgo leaf extract did not decrease compared to the concentration of ginkgolic acid in the ginkgo leaf extract obtained by filtration using filter paper or centrifugation without performing the above treatments (i) to (iii). From this result, it was found that ginkgolic acid does not precipitate in the ginkgo leaf extract obtained by a general manufacturing method (extraction conditions: 90-95 ° C for 1 hour) even if the temperature of the ginkgo leaf extract is lowered. This is thought to be due to the fact that the ginkgo leaf extract obtained by general manufacturing methods (extraction conditions: 1 hour at 90-95°C) is in a state where the ginkgolic acid in the ginkgo leaf extract cannot crystallize, for example due to denaturation of proteins in the ginkgo leaf extract caused by prolonged heating.

[0051] Furthermore, when uncrushed ginkgo leaves were used, the amount of ginkgolic acid in the ginkgo leaf extract did not decrease even when the above (i) filtration using stirring paper at 2 ° C was performed (Figure 6C). This result suggests that when uncrushed ginkgo leaves are used, the precipitation phenomenon of ginkgolic acid due to a decrease in temperature of the ginkgo leaf extract is less likely to occur. Considering that it is generally known that the amount of ginkgolic acid in the ginkgo leaf extract is greater when crushed ginkgo leaves are used than when uncrushed ginkgo leaves are used, it is considered that the precipitation phenomenon of ginkgolic acid due to a decrease in temperature of the ginkgo leaf extract depends on the amount of ginkgolic acid contained in the ginkgo leaf extract, that is, the more ginkgolic acid contained in the ginkgo leaf extract, the more likely it is that the precipitation phenomenon of ginkgolic acid due to a decrease in temperature of the ginkgo leaf extract will occur.

[0052] <Example 4. Determination of ginkgolic acid concentration in ginkgo leaf extract > 100 ml of water was added to 5 g of crushed ginkgo leaves, and (2) extraction was performed under the conditions of 90°C for 10 minutes, and the ginkgo leaves were removed by filtration using filter paper. 1M NaOH was added to 10 ml of the obtained ginkgo leaf extract (pH 3.8) to adjust the pH of the ginkgo leaf extract to 5, 7, 8, 9, or 11. The ginkgo leaf extract after pH adjustment was centrifuged at 2000 rpm and 4°C for 10 minutes to obtain a ginkgo leaf extract. The ginkgo leaf extract before pH adjustment and the ginkgo leaf extract obtained after pH adjustment and centrifugation were measured for ginkgolic acid concentration. The results are shown in Table 1 below.

[0053] [Table 1]

[0054] To summarize the above results, in the production of ginkgo leaf extract, alkalizing ginkgo leaf extract is an effective method for reducing the ginkgolic acid content in ginkgo leaf extract. In addition, in the production of ginkgo leaf extract, the ginkgolic acid content in ginkgo leaf extract can be reduced by adjusting the extraction conditions and / or cooling the ginkgo leaf extract. Furthermore, by using these methods in combination with the alkalizing of ginkgo leaf extract, the effect of reducing the ginkgolic acid content in ginkgo leaf extract can be further enhanced.

Claims

1. (a) precipitating ginkgolic acid in a ginkgo leaf extract by alkalizing the ginkgo leaf extract; and (b) isolating the ginkgo leaf extract having a reduced content of ginkgolic acids A method for producing a ginkgo leaf extract having a reduced content of ginkgolic acid, comprising:

2. The method according to claim 1, wherein the alkalizing the ginkgo leaf extract in the step (a) comprises adjusting the ginkgo leaf extract to a pH of 8 to 12.

3. The method according to claim 1 or 2, wherein the ginkgo leaf extract having a pH of 2 to 6 is alkalized in the step (a).

4. The method according to claim 1 or 2, wherein the ginkgo leaf extract having a reduced ginkgolic acid content has a ginkgolic acid concentration of 15 ppm or less.

5. The method according to claim 1 or 2, wherein the ginkgo leaf extract having a reduced content of ginkgolic acid has a flavonoid concentration of 30 ppm or more.

6. The method according to claim 1 or 2, wherein the ginkgo leaf extract having a reduced content of ginkgolic acid has a terpenoid concentration of 0.5 ppm or more.

7. (c) obtaining a ginkgo leaf extract from ginkgo leaves by solvent extraction at a temperature of 0 to 90° C.; The method includes the steps (c), (a) and (b) in this order. The method according to claim 1 or 2.

8. The method according to claim 7, wherein the solvent extraction is extraction with a liquid containing water.

9. (d) cooling the ginkgo leaf extract to precipitate ginkgolic acid in the ginkgo leaf extract; wherein said step (d) further comprises: carried out between step (c) and step (a); between step (a) and step (b); or The step (a) is carried out simultaneously with the step (a), The method of claim 7.

10. A ginkgo leaf extract produced by the method according to claim 1 or 2.

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