WO2014094405A1

WO2014094405A1 - Method for extraction and preparation of avermectin b2a

Info

Publication number: WO2014094405A1
Application number: PCT/CN2013/075035
Authority: WO
Inventors: 张海航; 王琳慧; 暴连群; 侯东伟; 刘现伟
Original assignee: 石家庄市兴柏生物工程有限公司
Priority date: 2012-12-17
Filing date: 2013-04-30
Publication date: 2014-06-26
Also published as: CN102977168A; CN102977168B

Abstract

Disclosed is a method for extraction and preparation of avermectin B2a. The method comprises: an avermectin fermentation solution is prepared into a dry mycelium and leached; a leach liquor is concentrated, and extraction agents such as toluene are added for extraction; extract liquor I is crystallized; a mother liquor acquired is concentrated into a paste; toluene is added into the paste to acquire extract liquor II; a filter aid is added into extract liquor II, same is stirred, cooled, and crystallized, then subjected to crystal growth and filtration; an filter cake acquired is dissolved by adding toluene, a filtrate is cooled again, devitrified, and then subjected to crystal growth and filtration; an avermectin B2a crystal crude product is acquired; the avermecting B2a crystal crude product is re-crystallized to acquire an avermectin B2a crystal refined product. The method of the present invention allows for effective isolation of avermectin B2a from the avermectin fermentation solution and provides a high yield and a great purification effect.

Description

Method for extracting and preparing avermectin B2a

Technical field

The invention relates to a method for extracting and preparing an antibiotic, in particular to a method for extracting and preparing avermectin B2a.

Background technique

Avermectin is a new type of antibiotic pesticide developed in China in the past 20 years. It belongs to microbial fermentation products and is the most ideal pesticide product to replace organophosphate and highly toxic pesticides. Avermectin is Streptomyces from Streptomyces A group of similar 16-membered macrolide antibiotics isolated from the fermentation product of avermitilis, consisting of a group of 8 homologues with similar structures. B1 and B2 are the two major components of this homologue. The avermectin B component has extremely high biocidal activity against nematodes, insects, and mites, but there are significant differences in insecticidal abilities B1a and B2a for different targets. The toxic activity of B1 component on livestock digestive nematodes was the highest, while the toxic activity of B2 on non-digestive nematodes was twice that of B1. The virulence activity against corn root worm (B) was B1a. 3 times. At present, the preparation method of avermectin B1 is a relatively mature technology, and generally includes the following steps: drying the mycelium from the avermectin fermentation broth, concentrating after leaching, extracting with extractant, and extracting Adding ethanol to the solution, heating to about 70 ° C, cooling to 35-25 ° C, crystallization, and then suction filtration, to obtain crude avermectin B1 crystals, and then extract, you can obtain a purity of more than 95% Avermectin B1. In the production process of avermectin B1, The mother liquor obtained by suction filtration is usually concentrated into an ointment for disposal as waste. Although avermectin B2a has been found to have a different toxicological activity than avermectin B1, it has not been industrially applied due to its inconvenient separation and purification. The content of different avermectin homologues in the avermectin fermentation broth was traced. The content of the two components of B1a and B2a was basically the same, reaching 40-45%, that is, the content of avermectin B accounted for More than 90% of the total avermectin. However, according to the existing extraction method, only high-purity avermectin B1 can be obtained from the fermentation broth. It can be seen that a large amount of avermectin B2a is wasted in the process of extracting and separating avermectin B1. On how to solve the problem of extracting and isolating avermectin B2, CN201010192026.2 proposes a method for separating and extracting different components of avermectin from residual avermectin. The method uses column chromatography to achieve the purpose of recovering B2a, B1b, B1a, A1a, A2a in the avermectin crystal mother liquor. Although the method can effectively recover the components of the avermectin crystal mother liquor, it is not only costly, but also has a limited recycling scale and is not suitable for industrial production.

Summary of the invention

The object of the invention is to provide an extraction preparation method of avermectin B2a with low production cost, good extraction effect and easy industrial production.

The object of the invention is achieved in this way:

The method for extracting and preparing avermectin B2a provided by the invention has the following two schemes under the framework of a general inventive concept:

The first method includes the following steps:

a. The avermectin fermentation liquid is made into a dried mycelium, extracted with ethanol, and filtered to obtain an extract;

(The leaching in the present invention means that the mycelium is soaked by ethanol, and the avermectin in the mycelium is dissolved in ethanol so that the active ingredient is dissolved in the ethanol solution).

b. After concentrating the extract, extracting with any one of toluene, DMF, or ethyl acetate to obtain an extract I;

The amount of the extractant to be added can be referred to the amount of the existing avermectin active ingredient extraction method. Generally it can be 5-6 times the mass of the extracted material.

c. After extracting the extract I, removing the extractant, adding ethanol, heating to 68-72 ° C, cooling to 35-25 ° C, crystallization, and then suction filtration, to obtain a cake I is a crude avermectin B1 crystal, The filtrate obtained is a mother liquor;

d. The mother liquor obtained in step c is concentrated into an ointment;

e. Extracting ointment with toluene extractant to obtain extract II;

f. Adding a filter aid to the extract II (the amount of the filter aid added is not particularly limited, so that the assist effect can be achieved), and after stirring uniformly, the temperature is lowered to 10 to 0 ° C, and after a large amount of crystals are precipitated, the crystal is raised and pumped. Filtering; obtaining filter cake II, adding toluene in filter cake II, heating to 80-100 ° C, filtering, removing the filter aid, the filtrate is again cooled to 10 ~ 0 ° C, after precipitation of a large number of crystals, crystal growth, suction filtration; The filter cake is rinsed with 0 to 10 ° C toluene to obtain a crude avermectin B2a crystal;

g. The crude avermectin B2a crystals were recrystallized, suction filtered, and dried to obtain a fine crystal of avermectin B2a.

In the method, the filter aid described in the f process may be selected from diatomaceous earth, vitrified microbeads and perlite, wherein

Perlite is preferred because of its high safety, wide range of sources, and good filtration aid. The amount added is more preferably from 1 to 2% based on the total mass of the extract II.

In the method, after the stirring in the step f is uniform, the temperature lowering condition is preferably 10 to 0 ° C, and under this condition, the extracted and isolated avermectin B2a has a higher purity.

In the method, the crude avermectin B2a crystal is recrystallized according to the step g, and the crude avermectin B2a crystal obtained in step f is added to 5-7 times of mass of toluene and the activated carbon is 0.5-2% by mass. After stirring, the temperature is raised to 80-100 ° C, the crude product of avermectin B2a crystals is melted, filtered, the filter aid and activated carbon in the solution are removed, the filtrate is recovered to the crystallization tank, stirred, and simultaneously cooled to 10 to 0 ° C, to be crystallized After a large amount of precipitation, keep warm for 20-30 minutes and filter. This results in a more pure and better avermectin B2a crystal.

The method for extracting and preparing a second avermectin B2a provided by the invention comprises the following steps:

b. After concentrating the extract, extracting with a toluene extractant to obtain an extract I;

c. Adding filter aid to the extract I, stirring evenly, cooling to 10 ~ 0 ° C, a large amount of crystals are precipitated, suction filtration; filter cake II is obtained, adding toluene in filter cake II, heating to 80 ~ 100 ° C, filtering , the filter aid is removed, the filtrate is again cooled to 10 ~ 0 ° C, a large amount of crystals are precipitated, crystallized, suction filtration; the obtained filter cake is rinsed with 0 ~ 10 ° C toluene, to obtain crude avermectin B2a crystal;

d. The crude avermectin B2a crystals are recrystallized and dried to obtain a fine crystal of avermectin B2a.

As described above, the filter aid described in the step c in the method is preferably a perlite filter aid, and the amount thereof is 1-2% by mass of the total liquid of the extract II.

In the method, after the stirring described in the step c is uniform, the temperature lowering condition is preferably 10 to 0 °C.

In the method, the crude avermectin B2a crystals described in the step d are recrystallized, and it is preferred to add the crude avermectin B2a crystals in step c to 5-7 times the mass of toluene and 0.5-2% by mass of activated carbon, and stir. After heating to 80-100 ° C, the crude avermectin B2a crystals are melted, filtered, and the filtrate is recovered to the crystallization tank, stirred, and simultaneously cooled to 10 ~ 0 ° C, after the crystal is largely precipitated, kept for 20-30 minutes, suction filtration .

The method of the invention can effectively separate avermectin B2a from the avermectin fermentation broth, and has high extraction rate and good extraction effect, and provides technical guarantee for the industrial application of avermectin B2a.

The method of the invention has simple process, easy control of process and low production cost, in particular, it can also fully utilize waste in the production process of avermectin B1, thereby further improving the overall utilization level of avermectin fermentation broth, greatly Reduced production costs and increased profitability.

DRAWINGS

Figure 1 is a flow chart of the present invention.

Figure 2 is a liquid chromatogram of the avermectin B2a component prepared by the method of the present invention.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

detailed description

Example 1

Referring to Flowchart 1, the specific steps are:

a, using avermectin fermentation broth as the starting material, pumped into the plate frame for filtration. In order to increase the filtration rate, an appropriate amount of the filter aid may be added to the avermectin fermentation broth, and the fermentation broth may be heated to 80 ° C to 90 ° C. The mycelium is obtained after filtration, and then dried to obtain a dried mycelium. The dried mycelium is placed in a reaction tank and extracted by ethanol soaking (abbreviated as leaching). The amount of ethanol added is preferably such that the mycelium can be completely immersed, and the concentration of ethanol can be selected in accordance with the range shown by the conventional leaching method, and the present invention is preferably 75 to 95%. After the dried mycelium is soaked in ethanol for 2-5 hours, the extract is collected and used; the filter residue can be repeatedly leached 2-3 times with ethanol, and the extract is collected and combined for use;

b. The extract is pumped into an evaporation can, and the extract is concentrated by heating with a sandwich vapor, and then the content of avermectin B1 in the extract concentrate is measured, and toluene having 5 times the mass of avermectin B1 is added. And 1 time of avermectin B1 weight of water, stirred for 30 min to 40 min, allowed to stand, the bottom aqueous solution was discharged, and the organic solution was collected to obtain an extract I.

c. After extracting the toluene from the extract I, adding 2-5 times of mass of ethanol, stirring for 30 min to 40 min, transferring to a crystallization tank, heating to about 70 ° C, and then cooling to 28-25 ° C, Crystallization was carried out, followed by suction filtration to obtain a cake I was a crude avermectin B1 crystal. The crude avermectin B1 crystal can be recrystallized according to the existing method for preparing avermectin B1, thereby obtaining avermectin B1 with a purity of 95% or more; the filtrate obtained by suction filtration is a mother liquor;

d. The ethanol in the mother liquor obtained in step c is recovered and concentrated to form an ointment.

The effective component extracted from the above part is avermectin B1, and the obtained ointment contains a large amount of avermectin B2.

e, adding an appropriate amount of toluene to the ointment (which can be dissolved), and extracting to obtain an extract II;

f. Add 2% perlite filter aid (100 kg of extract II total solution, add 2 kg of perlite) to the extract II, stir evenly, then cool down to 10 ~ 0 ° C, after a large amount of crystals are precipitated, After standing for 20-30 minutes (greening), vacuum filtration to obtain a filter cake II (containing a filter aid). The filter cake II is further added with toluene, heated to 80-100 ° C, and all melted, filtered, filtered to remove the filter aid, and the filtrate is recovered, and the filtrate is again cooled to 10 to 0 ° C. After a large amount of crystals are precipitated, the crystal is raised, and the vacuum is maintained. After suction filtration, the obtained filter cake was rinsed with toluene at 0-10 ° C until the color became whitish, and dried, and the obtained white crystalline powder was detected as crude avermectin B2a.

g, avermectin B2a crude can be added toluene, warmed to 80-100 ° C, so that it dissolves (this can also be added activated carbon, color removal treatment), filtered, the filtrate is recovered, the filtrate is cooled again to 10 ~ 0 ° C After a large amount of crystals are precipitated, the crystals are crystallized and vacuum filtered, and the obtained filter cake is rinsed with 0-10 ° C toluene until the color is whitish, and dried to obtain recrystallized avermectin B2a. The recrystallization was repeated three times in this way to obtain an avermectin B2a product having a purity of 89.7%. The yield was 95%. The test parameters are shown in Table 1, and the test results are shown in Figure 2 and Table 2.

Table 1

Sample Name: Sample Name:	B2a 图谱 B2a map	Injection Volume: Injection Volume:	20.0 20.0
Vial Number: Vial Number:	7 7	Channel: Channel:	UV_VIS_1 UV_VIS_1
Sample Type: Sample Type:	unknown Unknown	Wavelength: Wavelength:	245 245
Control Program: Control Program:		Bandwidth: Bandwidth:	n.a. N.a.
Quantif. Method: Quantif. Method:	方法 method	Dilution Factor: Dilution Factor:	1.0000 1.0000
Recording Time: Recording Time:	2012-7-16 16:19 2012-7-16 16:19	Sample Weight: Sample Weight:	0.0344 0.0344
Run Time (min): Run Time (min):	30.00 30.00	Sample Amount: Sample Amount:	1.0000 1.0000

Table 2

No. No.	Ret.Time Ret.Time	Peak Name Peak Name	Height Height	Area Area	Rel.Area Rel.Area	Amount Amount	Type Type
	min Min		mAU mAU	*mAUmin mAUmin*	% %
1 1	1.83 1.83	n.a. N.a.	2.087 2.087	0.319 0.319	0.17 0.17	n.a. N.a.	BMb BMb
2 2	1.98 1.98	n.a. N.a.	0.785 0.785	0.075 0.075	0.04 0.04	n.a. N.a.	bMB bMB
3 3	2.55 2.55	n.a. N.a.	1.432 1.432	0.190 0.190	0.10 0.10	n.a. N.a.	BMB BMB
4 4	3.30 3.30	n.a. N.a.	2.000 2.000	0.317 0.317	0.17 0.17	n.a. N.a.	BMB BMB
5 5	3.79 3.79	n.a. N.a.	3.037 3.037	0.402 0.402	0.21 0.21	n.a. N.a.	BMb BMb
6 6	4.55 4.55	n.a. N.a.	0.845 0.845	0.294 0.294	0.16 0.16	n.a. N.a.	bMB bMB
7 7	5.15 5.15	n.a. N.a.	0.577 0.577	0.105 0.105	0.06 0.06	n.a. N.a.	BMb BMb
8 8	5.51 5.51	n.a. N.a.	9.360 9.360	1.886 1.886	1.01 1.01	n.a. N.a.	bMB bMB
9 9	6.51 6.51	n.a. N.a.	23.159 23.159	6.446 6.446	3.45 3.45	n.a. N.a.	BMB BMB
10 10	6.95 6.95	n.a. N.a.	0.798 0.798	0.106 0.106	0.06 0.06	n.a. N.a.	BMb BMb
11 11	7.19 7.19	n.a. N.a.	2.509 2.509	0.490 0.490	0.26 0.26	n.a. N.a.	bMB bMB
12 12	8.01 8.01	B2a B2a	624.958 624.958	167.784 167.784	89.70 89.70	n.a. N.a.	BMB BMB
13 13	9.71 9.71	n.a. N.a.	2.851 2.851	0.681 0.681	0.36 0.36	n.a. N.a.	BMb BMb
14 14	9.98 9.98	n.a. N.a.	3.669 3.669	0.983 0.983	0.53 0.53	n.a. N.a.	bMB bMB
15 15	10.75 10.75	n.a. N.a.	3.911 3.911	1.189 1.189	0.64 0.64	n.a. N.a.	BMb BMb
16 16	11.42 11.42	n.a. N.a.	1.509 1.509	0.465 0.465	0.25 0.25	n.a. N.a.	bMB bMB
17 17	12.87 12.87	n.a. N.a.	2.662 2.662	0.973 0.973	0.52 0.52	n.a. N.a.	BMB BMB
18 18	17.14 17.14	n.a. N.a.	8.355 8.355	4.198 4.198	2.24 2.24	n.a. N.a.	BMB BMB
19 19	22.69 22.69	n.a. N.a.	0.271 0.271	0.152 0.152	0.08 0.08	n.a. N.a.	BMB BMB
Total: Total:			694.774 694.774	187.053 187.053	100.00 100.00	0.000 0.000

Example 2

Referring to Flowchart 1, the specific steps are:

a, using avermectin fermentation broth as the starting material, pumped into the plate frame for filtration. The mycelium is obtained after filtration, and then dried to obtain dried hyphae. The mycelium was placed in a reaction tank and extracted with ethanol at a concentration of 85%. The amount of ethanol added is preferably such that the mycelium can be completely immersed. After the mycelium is soaked in ethanol for 3 hours, the extract is collected and used;

b. The leachate is pumped into the evaporation tank, and the extract is concentrated to contain no ethanol, and then a certain amount of toluene and water are added, the temperature is raised to 80-100 ° C, stirred for 30 min to 40 min, and allowed to stand, and the bottom is discharged. The aqueous solution is collected and the organic solution is collected to obtain an extract I.

c, the extract I is added to the perlite filter aid, stirred for 30min ~ 40min, after stirring evenly, the temperature is reduced to 10 ~ 0 ° C, crystallization, precipitation of a large number of crystals, after standing for 45 minutes (nurturing), suction filtration; Cake II, filter cake II was added to toluene to dissolve, filtered, and the filter aid was removed. The filtrate was again cooled to 10 to 0 ° C. After a large amount of crystals were precipitated, the crystals were crystallized and suction filtered; the obtained cake was made with 0 to 10 ° C toluene. Rinsing to obtain crude avermectin B2a crystals;

d. The crude avermectin B2 crystals were recrystallized four times as described in Example 1, filtered by suction, and dried to obtain a crystal of avermectin B2a having a purity of 90%. The yield was 98%.

Example 3

a, using avermectin fermentation broth as the starting material, pumped into the plate frame for filtration. The mycelium is obtained after filtration, and then dried to obtain dried hyphae. The mycelium was placed in a reaction tank and extracted with a concentration of 60% ethanol. The amount of ethanol added is preferably such that the mycelium can be completely immersed. After the mycelium is soaked in ethanol for 5-6 hours, the extract is collected and used;

b. The extract is pumped into the evaporation tank, and the extract is concentrated to ethanol-free, then the same amount of DMF is stirred, stirred for 20 min to 30 min, allowed to stand, the bottom aqueous solution is discharged, and the organic solution is collected to obtain an extract I. .

c. After extracting DMF from extract I, the obtained material solution is added with 1% diatomaceous earth filter aid, stirred for 20 min to 30 min, stirred uniformly, cooled to 5-0 ° C, crystallized, and a large amount of crystals are precipitated, and then allowed to stand. Hour (greening), suction filtration; filter cake II is obtained, filter cake II is added to DMF to dissolve, filtered, and the filter aid is removed, the filtrate is cooled again to 5 to 0 ° C, and a large amount of crystals are precipitated, crystallized, and filtered; The obtained filter cake is rinsed with 0-5° CDMF to obtain a crude avermectin B2a crystal;

d. The crude avermectin B2a crystals were recrystallized as described in Example 1, filtered by suction, and dried to obtain a crystal of avermectin B2a having a purity of 70%. The yield was 95%.

Example 4

Referring to Flowchart 1, the specific steps are:

a, using avermectin fermentation broth as the starting material, pumped into the plate frame for filtration. The mycelium is obtained after filtration, and then dried to obtain dried hyphae. The mycelium was placed in a reaction tank and 85% ethanol was added. After the mycelium is soaked in ethanol for 12 hours, the extract is collected and used; the residue can be repeatedly extracted with ethanol for 3 times, and the extract is collected and combined for use;

b. The extract is pumped into an evaporation tank, and the extract is concentrated by heating with a sandwich vapor, and then the content of avermectin B1 in the extract concentrate is measured, and toluene having 3 times the mass of avermectin B1 is added. After stirring for 30 min to 40 min, the mixture was allowed to stand, and the aqueous solution at the bottom was discharged, and the organic solution was collected to obtain an extract I.

c. After extracting the toluene from the extract I, adding 3 times of mass of ethanol, stirring for 30 min to 40 min, transferring to a crystallizing tank, heating to about 70 ° C, then cooling to 28-25 ° C for crystallization Then, by suction filtration, the filter cake I was obtained as a crude avermectin B1 crystal. The crude avermectin B1 crystal can be recrystallized according to the existing method for preparing avermectin B1, thereby obtaining avermectin B1 with a purity of 95% or more; the filtrate obtained by suction filtration is a mother liquor;

f. Add 1% perlite filter aid (100 kg of extract II total solution, add 1 kg of perlite) to the extract II, stir evenly, then cool to 10-8 ° C, after a large amount of crystals are precipitated, Place for 40-60 minutes (greening), vacuum filtration, to obtain filter cake II (containing filter aid), the filter cake II is added to warm toluene (25-32 ° C) to dissolve, and then heated to 90-100 ° C After it has been completely melted, it is filtered, the filter aid is filtered off, the filtrate is recovered, and the filtrate is cooled again to 10 to 5 ° C. After a large amount of crystals are precipitated, the crystals are crystallized and vacuum filtered, and the obtained filter cake is toluene at 0-5 ° C. After rinsing until the color is whitish, it is dried, and the obtained white crystalline powder is detected as crude avermectin B2a.

g, avermectin B2a crystals were added with 5 times the mass of toluene and 0.5% of activated carbon, and the mixture was heated to 80-100 ° C after stirring. After the crude avermectin B2a crystals were melted, filtered, and the filtrate was removed toluene. Transfer to the crystallization tank, stir, add at the same time, toluene at 80-90 ° C, after the crystal is precipitated in a large amount, keep warm for 20-30 minutes, suction filtration, and the obtained filter cake is rinsed with 0-5 ° C toluene until the color is whitish. Drying, the obtained recrystallized avermectin B2a. This was repeated three times to obtain a avermectin B2a product with a purity of 90%. The yield was 97%.

Claims

A method for extracting and preparing avermectin B2a, characterized in that it comprises the following steps:

a. The avermectin fermentation liquid is made into a dried mycelium, extracted with ethanol, and filtered to obtain an extract;

b. After concentrating the extract, extracting with any one of toluene, DMF or ethyl acetate to obtain an extract I;

c. After removing the extractant from the extract I, adding ethanol, heating to 68-72 ° C, cooling to 35-25 ° C, crystallization, and then suction filtration to obtain a crude cake of avermectin B1 crystals. The filtrate is a mother liquor;

d. The mother liquor obtained in step c is concentrated into an ointment;

e. Toluene is added to the ointment to obtain an extract II;

f. Add filter aid to the extract II, stir evenly, then cool down to 10 ~ 0 ° C, precipitate a large amount of crystal II, crystallize, suction filtration; get filter cake II, filter cake II added toluene dissolved, warmed to 80 ~ 100 ° C, filtration, remove the filter aid, the filtrate is cooled again to 10 ~ 0 ° C, a large amount of crystals are precipitated, crystallized, suction filtration; the obtained filter cake is rinsed with 0 ~ 10 ° C toluene, to obtain crude avermectin B2a crystals ;

g. The crude avermectin B2 crystals were recrystallized, suction filtered, and dried to obtain a fine crystal of avermectin B2a.
The method for extracting and preparing avermectin B2a according to claim 1, wherein the filter aid in the step f is a perlite filter aid, and the amount of the filter aid is 1 according to the mass of the total liquid of the extract II. ~2%.
The method for extracting and preparing avermectin B2a according to claim 1, wherein the stirring in the step f is uniform, and then the temperature is lowered to 10 to 0 °C.
The method for extracting and preparing avermectin B2a according to claim 1, wherein in the step g, the crude avermectin B2a crystal is recrystallized, and the crude avermectin B2a crystal obtained in step f is added to 5 -7 times the mass of toluene and 0.5~2% of activated carbon, after stirring, the temperature is raised to 80-100 ° C, the crude avermectin B2a crystals are melted, filtered, and the filtrate is recovered to the crystallization tank; then, the temperature is lowered to 10~ 0 ° C, after a large amount of crystal precipitation, heat for 20 to 30 minutes, suction filtration.
A method for extracting and preparing avermectin B2a, characterized in that it comprises the following steps:

a. The avermectin fermentation liquid is made into a dried mycelium, extracted with ethanol, and filtered to obtain an extract;

b. After concentrating the extract, adding any one of toluene, DMF or ethyl acetate to obtain an extract I;

c. Extract I, add filter aid, stir evenly, cool down to 10 ~ 0 ° C, precipitate a large amount of crystal II, crystallize, suction filtration; to filter cake II, filter cake II added toluene dissolved, warmed to 80 ~ 100 °C, filtration, remove the filter aid, the filtrate is cooled again to 10 ~ 0 ° C, a large amount of crystals are precipitated, crystallized, suction filtration; the obtained filter cake is rinsed with 0 ~ 10 ° C toluene, to obtain crude avermectin B2a crystal;

d. The crude avermectin B2a crystals were recrystallized, suction filtered, and dried to obtain a fine crystal of avermectin B2a.
The method for extracting and preparing avermectin B2a according to claim 5, wherein the filter aid in the step c is a perlite filter aid, and the amount of the filter aid is 1 according to the mass of the total liquid of the extract II. ~2%.
The method for extracting and preparing avermectin B2a according to claim 1, wherein the crude avermectin B2a crystal in the step g is recrystallized, and the crude avermectin B2a crystal obtained in step c is added to 5- 7 times the mass of toluene and 0.5~2% of activated carbon with mass molecules, and after heating, the temperature is raised to 80-100 ° C. After the crude avermectin B2a crystals are melted, filtered, the filtrate is recovered to the crystallization tank, and then the temperature is lowered to 10~0. °C, after a large amount of crystals are precipitated, keep warm for 20 to 30 minutes, and filter by suction.