CN103408610B - The method of arbutin is extracted from leaf of pear tree - Google Patents

Abstract

The method for extracting arbutin from pear leaves comprises extracting arbutin-containing leaf juice from pear leaves, and obtaining arbutin through concentration, purification and recrystallization. Step 1, after drying and crushing the pear leaves, impregnating with methanol, filtering, and concentrating the filtrate into an extract; Step 2, taking the resin and packing it into a column, dissolving the extract obtained in Step 1 with water, filtering, and the content of arbutin in the filtrate 2mg/mL, the filtrate was purified on the column to obtain the crude arbutin extract; in step 3, the ENV packing was used to pack the column, the crude arbutin extract obtained in step 2 was dissolved and then purified on the column to obtain the crude arbutin; Step 4, crystallizing the crude arbutin obtained in step 3 to obtain arbutin. Step 5, recrystallizing the arbutin obtained in step 4. The raw materials used in the present invention are waste materials after harvesting of economical fruit trees, and the raw materials are rich in sources, easy to obtain, and low in cost. The extraction method of the invention has simple process and convenient operation, and the obtained arbutin has high purity.

Description

Method for extracting arbutin from pear leaves

technical field

The invention belongs to the technical field of arbutin extraction methods, and relates to a method for extracting arbutin from pear leaves.

Background technique

Arbutin is a natural active substance that can effectively inhibit the biological tyrosinase activity in the skin, block the formation of melanin, accelerate the decomposition and excretion of melanin, thereby reducing skin pigmentation, removing spots and Freckles are the main active substances in whitening cosmetics at home and abroad. In recent years, with the development of the domestic cosmetics industry, in order to comply with the trend of "returning to nature" in skin care cosmetics, the "green whitening" of natural active substances has become increasingly popular, and arbutin, as a non-toxic and harmless natural active substance with obvious whitening effect Material, the market demand is expanding day by day.

At present, the raw materials for extracting arbutin are mainly fruit trees, such as blueberry fruit. The process route is complicated, and the cost of extracting arbutin is high due to limited fruit sources.

The concentration of the reagents involved in this paper is the volume concentration, and the other percentages involved are all percentages by weight.

Contents of the invention

The purpose of the present invention is to provide a method for extracting arbutin from pear leaves, which solves the problems of complex process and high cost in the prior art.

The technical proposal of the present invention is a method for extracting arbutin from pear tree leaves, extracting arbutin-containing leaf juice from pear tree leaves, and obtaining arbutin through concentration, purification and recrystallization.

The present invention is also characterized in that it specifically comprises the following steps:

Step 1, drying and pulverizing the pear leaves, impregnating them with methanol, filtering, and concentrating the filtrate into an extract;

Step 2, take the resin and pack it into a column, dissolve the extract obtained in step 1 with water, filter, the content of arbutin in the filtrate is 2 mg/mL, put the filtrate on the column for purification, and obtain the crude arbutin extract;

Step 3, take the ENV filler and pack it into a column, dissolve the crude arbutin extract obtained in step 2, put it on the column and then purify it, and obtain the crude arbutin;

Step 4, crystallizing the crude arbutin obtained in step 3 to obtain arbutin.

Step 5, recrystallizing the arbutin obtained in step 4.

In step 1, the yield of the extract is 7% to 10%, and the content of arbutin in the extract is about 6% to 10%.

The resin in step 2 is LSA-900B resin; the filtrate is purified on the column, rinsed with different concentrations of methanol, and the flow rate is kept at 0.4 to 0.5 times the column volume/hour to obtain a purified solution. After the purified solution is concentrated, bearberry in a solid state is obtained Glycoside crude extract, of which arbutin content is 30% to 34%.

In step 3, after the filtrate is purified on the column, the effluent is collected and rinsed with water of 2 times the column volume. Volume of 10% methanol was eluted, and the eluate of 1 times the column volume was collected each time, and the flow rate was maintained at 2-3mL/min throughout the process; the arbutin content in the eluate obtained from the first three elutions was the highest, respectively 3.0mg/min. mL, 4.8mg/mL, 1.6mg/mL, collect the eluate from the first three elutions and concentrate to obtain the crude arbutin in solid state, the arbutin content is greater than 82%.

In step 4, add ethyl acetate to the crude arbutin, heat to reflux for 0.5-1 h, filter while it is hot, and let it stand overnight, a white powdery solid is precipitated, filtered, and dried to obtain a white powdery solid, the powdery solid contains The fruit glycoside content is greater than 95%.

In step 5, recrystallization can be repeated many times, and the purity of arbutin can reach more than 99%.

The present invention has following beneficial effects:

1. The raw materials used in the present invention are waste materials after harvesting of economical fruit trees. The raw materials are rich in sources, easy to obtain, and low in cost.

2. The extraction method of the present invention has simple process and convenient operation, and the obtained arbutin has high purity.

Description of drawings

Fig. 1 is the infrared spectrogram of the arbutin prepared by the method for extracting arbutin from pear leaves of the present invention.

detailed description

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

The method for extracting arbutin from pear leaves comprises extracting arbutin-containing leaf juice from pear leaves, and obtaining arbutin through concentration, purification and recrystallization. Specifically include the following steps:

Step 1: After drying and pulverizing the leaves of the pear tree, impregnating them with methanol, filtering, and concentrating the filtrate into an extract; the yield of the extract is 7%-10%, and the content of arbutin in the extract is about 6%-10%. The extract yield is the percentage of the extract in the mass of pear leaves used.

Step 2, take the resin and pack it into a column, dissolve the extract obtained in step 1 with water, filter, the arbutin content in the filtrate is 2 mg/mL, put the filtrate on the column for purification, and obtain the crude arbutin extract; the resin is LSA-900B resin; The filtrate is purified on the column, rinsed with different concentrations of methanol, and the flow rate is maintained at 0.4 to 0.5 times the column volume/hour to obtain the purified liquid. After the purified liquid is concentrated, the crude arbutin extract in a solid state is obtained, and the arbutin content is 30% %~34%.

Step 3, take the ENV filler and pack it into a column, dissolve the crude arbutin extract obtained in step 2, put it on the column and then purify it, and obtain the crude arbutin; after the filtrate is put on the column and purified, collect the effluent, and rinse with 2 times the column volume of water Wash, the content of arbutin in the sample effluent is lower than 0.005mg/mL, discard the effluent, and then elute with 10% methanol of 10 times the column volume, collect 1 times the column volume of the eluate each time, the whole process The flow rate was maintained at 2-3mL/min; the arbutin content in the eluate obtained from the first three elutions was the highest, which were 3.0mg/mL, 4.8mg/mL, and 1.6mg/mL respectively. Collect the eluate from the first three elutions, Concentrate to get crude arbutin in solid state, the arbutin content is greater than 82%.

Step 4, crystallizing the crude arbutin obtained in step 3 to obtain arbutin. Specifically, the crude arbutin is added to ethyl acetate, heated to reflux for 0.5-1h, filtered while it is hot, and left to stand overnight, and a white powdery solid is precipitated, filtered, and dried to obtain a white powdery solid. The arbutin in the powdery solid The content is greater than 95%.

Step 5, recrystallizing the arbutin obtained in step 4. Recrystallization can be repeated many times, and the purity of arbutin can reach more than 99%.

Example 1

Step 1, extract the extract containing arbutin from pear tree leaves, and its specific steps are:

Step 1a: pick pear leaf samples, dry them in an oven at 40°C, and crush them.

Step 1b: Weigh 400g of the crushed pear leaf sample, add 4L of pure methanol, soak for 3 days at room temperature, filter, rotate the filtrate, concentrate to remove methanol, and obtain an extract containing arbutin, with a yield of 7 %, the content of arbutin in the extract is about 6%.

Step 2, prepare arbutin crude extract with LSA-900B resin:

Step 2a: Screening of the resin:

Static adsorption test was used to study the adsorption effect of 4 different types of resins. The 4 kinds of resins selected were LSA-900B, LSA-900C, LX-200 and LX-400. Accurately weighed 1g of each type of resin, and prepared according to the requirements. After treatment, put it into a stoppered Erlenmeyer flask, take 0.1g of pear leaf extract, add 40mL of water to dissolve, add 10mL of extract aqueous solution to each resin, and statically adsorb for 1h at room temperature, take the supernatant of each resin, and use Determination of arbutin content by HPLC (determination method see literature: Zhao Jie, He Qiang, Yao Binghua, et al. Confirmation and HPLC detection of the active ingredient arbutin in pear leaves, China Modern Applied Pharmacy, 2011), and the initial solution Arbutin content comparison, calculate the static adsorption rate of various resins to arbutin, the result is shown in Table 1, as seen from Table 1, the static adsorption rate of LSA-900B type resin is the highest, so select LSA-900B type resin to carry out Initial purification.

Table 1 Static adsorption rate of arbutin by different types of resins

Resin model LSA-900B LSA-900C LX-200 LX-400 Adsorption rate(%) 62.8 9.4 20.8 8.5

Step 2b: Use LSA-900B resin to separate and obtain the crude arbutin extract:

Take 300g of LSA-900B resin and pack it into a column (column volume is about 450mL), activate as required, take 8g of pear leaf extract extract, dissolve it in 240mL of water, filter, the content of arbutin in the filtrate is 2mg/mL, and put the filtrate on the column for purification , keep the flow rate at 0.4 times the column volume/hour, collect the sample effluent (No. 0), and then use 1 times the column volume of distilled water (No. 1), 1 times the column volume of 10% methanol (No. 2), 1 times the column volume 20% methanol by volume (Code 3), 30% methanol by 1 column volume (Code 4), pure methanol by 1 column volume (Code 5), pure methanol by 1 column volume (Code 6), and collect the elution at each stage Washing liquid, detect the content of arbutin in the eluting liquid, the results are shown in Table 2.

Table 2 Arbutin content in different eluents

It can be seen from Table 2 that eluent No. 3 (20% methanol) began to elute more arbutin, and eluent No. 5 (pure methanol) basically eluted the arbutin adsorbed on the resin Therefore, according to the experimental results in Table 2, it is determined that after loading the sample, rinse with 1 times the column volume of water, then rinse with 1 times the column volume of 10% methanol, discard the eluent, and wash the eluent through Subsequent optimization, 1.4 times the column volume of pure methanol can basically elute the arbutin adsorbed on the resin completely. Concentrate the methanol eluent to dryness to obtain about 1.2 g of arbutin crude extract, of which the arbutin content is about 30%.

Step 3, purifying the crude arbutin extract with ENV polymer filler.

After a lot of pre-experiments, ENV adsorption packing was selected to further purify the crude arbutin extract. ENV filler is a polystyrene-divinylbenzene copolymer material, which has a good adsorption effect on arbutin in aqueous solution, but basically has no adsorption on large polar substances such as sugars, and the adsorption on ENV Arbutin is easily eluted by 10% methanol solution, and other impurities adsorbed on the ENV filler require a higher concentration of methanol to be eluted, so as to achieve a good purification effect.

Specific experimental steps: Take 20g of ENV filler and pack it into a column (column volume is about 56mL), activate the column with 1 times the column volume of methanol and 1 times the column volume of water, and take 1.2g of arbutin crudely extracted after preliminary purification by LSA-900B Dissolve with 50mL water, filter, filter the filtrate through the column, collect the effluent, rinse with 2 times the column volume of water, the content of arbutin in the loading effluent is lower than 0.005mg/mL, discard the effluent, Then use 10 times the column volume of 10% methanol to elute, collect 1 times the column volume of the eluate (numbered 1 to 10) each time, and keep the flow rate at 2mL/min throughout the process. The content of arbutin was the highest, which were 3.0mg/mL, 4.8mg/mL, and 1.6mg/mL respectively. The content of arbutin in the eluate from the fourth elution was already low, only 0.06mg/mL. From the second eluent, the eluent is mainly composed of other components. Therefore, according to the detection situation, the eluate obtained from the first three times was collected and concentrated to obtain about 0.3g of arbutin crude product with high purity (in a solid state). After testing, the arbutin content was about 82%.

Step 4, recrystallization to obtain arbutin monomer

Take about 0.3g of relatively pure crude arbutin, add 10mL of ethyl acetate, heat to reflux for 0.5h, filter while it is hot, let it stand overnight, and precipitate a white powdery solid, filter, and dry to obtain about 0.2g of a white powdery solid, The content of arbutin in the powdery solid is about 95%. If it is necessary to prepare arbutin with higher purity, recrystallization can be repeated for 3 times, and the purity of arbutin can reach more than 99%.

Step 5. Confirmation of arbutin

The arbutin obtained by separation was confirmed by high performance liquid chromatography, mass spectrometry, infrared spectrum and nuclear magnetic resonance H spectrum and C spectrum. The standard infrared spectrum of arbutin is consistent.

Shaanxi Province is a large province of fruit production, in which pear trees are planted in an area of nearly one million mu, and pear leaves are a by-product of pear tree planting, which has a very rich source and low cost.

Example 2

Step 1, extract the extract containing arbutin from pear tree leaves, and its specific steps are:

Step 1a: pick pear leaf samples, dry them in an oven at 50°C, and crush them.

Step 1b: Weigh 450g of the crushed pear leaf sample, add 4.5L of pure methanol, soak for 4 days at room temperature, filter, rotate the filtrate, concentrate to remove methanol, and obtain an extract containing arbutin. The yield of the extract is 8%, and the content of arbutin in the extract is about 7%.

Step 2, prepare arbutin crude extract with LSA-900B resin:

Step 2a: Screening of the resin:

Static adsorption test was used to study the adsorption effect of 4 different types of resins. The 4 kinds of resins selected were LSA-900B, LSA-900C, LX-200 and LX-400. Accurately weighed 3g of each type of resin, and prepared according to the requirements. After treatment, put it into a stoppered Erlenmeyer flask, take 0.3g of pear leaf extract, add 120mL of water to dissolve, add 30mL of extract aqueous solution to each resin, and statically adsorb for 1h at room temperature, take the supernatant of each resin, and use Determination of arbutin content by HPLC (determination method see literature: Zhao Jie, He Qiang, Yao Binghua, et al. Confirmation and HPLC detection of the active ingredient arbutin in pear leaves, China Modern Applied Pharmacy, 2011), and the initial solution Arbutin content comparison, calculate the static adsorption rate of various resins to arbutin, the results are shown in table 3, as can be seen from table 3, the static adsorption rate of LSA-900B type resin is the highest, so choose LSA-900B type resin to carry out Initial purification.

Table 3 Static adsorption rate of arbutin by different types of resins

Resin model LSA-900B LSA-900C LX-200 LX-400 Adsorption rate(%) 60.6 8.3 18.1 7.4

Step 2b: Use LSA-900B resin to separate and obtain the crude arbutin extract:

Take 350g of LSA-900B resin and pack it into a column (column volume is about 530mL), activate as required, take 9g of pear leaf extract, dissolve it in 320mL of water, filter, the content of arbutin in the filtrate is 2mg/mL, and put the filtrate on the column for purification , keep the flow rate at 0.4 times the column volume/hour, collect the sample effluent (No. 0), and then use 1 times the column volume of distilled water (No. 1), 1 times the column volume of 10% methanol (No. 2), 1 times the column volume 20% methanol by volume (Code 3), 30% methanol by 1 column volume (Code 4), pure methanol by 1 column volume (Code 5), pure methanol by 1 column volume (Code 6), and collect the elution at each stage Washing liquid, detect the content of arbutin in the eluting liquid, the results are shown in Table 4.

Arbutin content in different eluents in table 4

As can be seen from Table 4, eluent No. 3 (20% methanol) began to elute more arbutin, and eluent No. 5 (pure methanol) basically eluted the arbutin adsorbed on the resin Therefore, according to the experimental results in Table 2, it is determined that after loading the sample, rinse with 1 times the column volume of water, then rinse with 10% to 15% methanol of 1 times the column volume, discard the eluent, wash After subsequent optimization of dehydration, 1.4 to 1.5 times the column volume of pure methanol can basically elute the arbutin adsorbed on the resin completely. Concentrate the methanol eluent to dryness to obtain about 2.1 g of arbutin crude extract, of which the arbutin content is about 30%.

Step 3, purifying the crude arbutin extract with ENV polymer filler.

After a lot of pre-experiments, ENV adsorption packing was selected to further purify the crude arbutin extract. ENV filler is a polystyrene-divinylbenzene copolymer material, which has a good adsorption effect on arbutin in aqueous solution, but basically has no adsorption on large polar substances such as sugars, and the adsorption on ENV Arbutin is easily eluted by 10% methanol solution, and other impurities adsorbed on the ENV filler require a higher concentration of methanol to be eluted, so as to achieve a good purification effect.

Specific experimental steps: Take 22g of ENV filler and pack it into a column (column volume is about 60mL), activate the column with methanol of 1 to 1.5 times the column volume and water of 1 to 2 times the column volume in sequence, and take 2.1g of bear that has been preliminarily purified by LSA-900B The crude extract of fructoside was dissolved in 55mL of water, filtered, the filtrate was purified through the column, the effluent was collected, rinsed with 2 times the column volume of water, the content of arbutin in the sample effluent was lower than 0.005mg/mL, discarded Remove the effluent, then elute with 10 times the column volume of 10% methanol, collect 1 times the column volume of the eluent (numbered 1 to 10) each time, and keep the flow rate at 3mL/min throughout the process. The content of arbutin in the eluate was the highest, which were 2.8mg/mL, 4.5mg/mL, and 1.7mg/mL respectively. The content of arbutin in the 4th eluate was already low, only 0.05mg/mL. From the second eluate obtained, the eluate is mainly composed of other components. Therefore, according to the detection situation, the eluate from the first three elutions was collected and concentrated to obtain about 0.44g of arbutin crude product with high purity (in a solid state). After testing, the arbutin content was about 85%.

Step 4, recrystallization to obtain arbutin monomer

Take about 0.44g of relatively pure arbutin crude product, add 30mL of ethyl acetate, heat and reflux for 1h, filter while it is hot, and let it stand overnight, a white powdery solid is precipitated, filtered, and dried to obtain about 0.3g of a white powdery solid. The content of arbutin in the powdery solid is greater than 95%. If you need to prepare arbutin with higher purity, you can repeat the recrystallization and recrystallize 3 times, and the purity of arbutin can reach more than 99%.

Step 5. Confirmation of arbutin

The isolated arbutin was confirmed by high performance liquid chromatography, mass spectrometry, infrared spectrum and nuclear magnetic resonance H spectrum and C spectrum, all of which can correspond to the standard library.

Shaanxi Province is a large province of fruit production, in which pear trees are planted in an area of nearly one million mu, and pear leaves are a by-product of pear tree planting, which has a very rich source and low cost.

Example 3

Step 1, extract the extract containing arbutin from pear tree leaves, and its specific steps are:

Step 1a: pick pear leaf samples, dry them in an oven at 60°C, and crush them.

Step 1b: Weigh 500g of the pulverized pear leaf sample, add 5L of pure methanol, soak at room temperature for 5 days, filter, rotate the filtrate, concentrate and remove methanol, and obtain an extract containing arbutin. The yield of the extract is 10 %, the content of arbutin in the extract is about 10%.

Step 2, prepare arbutin crude extract with LSA-900B resin:

Step 2a: Screening of the resin:

Static adsorption test was used to study the adsorption effect of 4 different types of resins. The 4 kinds of resins selected were LSA-900B, LSA-900C, LX-200 and LX-400. Accurately weighed 5g of each type of resin, and pre-prepared according to the requirements. After treatment, put it into a stoppered Erlenmeyer flask, take 0.5g pear leaf extract extract, add 200mL water to dissolve, add 50mL extract aqueous solution to each resin, and statically adsorb for 1h at room temperature, take the supernatant of each resin, and use Determination of arbutin content by HPLC (determination method see literature: Zhao Jie, He Qiang, Yao Binghua, et al. Confirmation and HPLC detection of the active ingredient arbutin in pear leaves, China Modern Applied Pharmacy, 2011), and the initial solution Arbutin content comparison, calculate the static adsorption rate of various resins to arbutin, the result is shown in Table 5, as can be seen from Table 5, the static adsorption rate of LSA-900B type resin is the highest, so choose LSA-900B type resin to carry out Initial purification.

Table 5 Static adsorption rate of arbutin by different types of resins

Resin model LSA-900B LSA-900C LX-200 LX-400 Adsorption rate(%) 69.7 10.2 21.1 9.3

Step 2b: Use LSA-900B resin to separate and obtain the crude arbutin extract:

Take 400g of LSA-900B resin and pack it into a column (column volume is about 600mL), activate as required, take 10g of pear leaf extract, dissolve it in 500mL of water, filter, the content of arbutin in the filtrate is 2mg/mL, and put the filtrate on the column for purification , keep the flow rate at 0.4 times the column volume/hour, collect the sample effluent (No. 0), and then use 1 times the column volume of distilled water (No. 1), 1 times the column volume of 10% methanol (No. 2), 1 times the column volume 20% methanol by volume (Code 3), 30% methanol by 1 column volume (Code 4), pure methanol by 1 column volume (Code 5), pure methanol by 1 column volume (Code 6), and collect the elution at each stage Washing liquid, detect the content of arbutin in the eluting liquid, the results are shown in Table 6.

Arbutin content in different eluents of table 6

It can be seen from Table 2 that eluent No. 3 (20% methanol) began to elute more arbutin, and eluent No. 5 (pure methanol) basically eluted the arbutin adsorbed on the resin Therefore, according to the experimental results in Table 2, it is determined that after loading the sample, rinse with 1 times the column volume of water, then rinse with 10% to 15% methanol of 1 times the column volume, discard the eluent, wash After subsequent optimization of dehydration, 1.4 to 1.5 times the column volume of pure methanol can basically elute the arbutin adsorbed on the resin completely. Concentrate the methanol eluent to dryness to obtain about 3.0 g of arbutin crude extract, of which the arbutin content is about 34%.

Step 3, purifying the crude arbutin extract with ENV polymer filler.

After a lot of pre-experiments, ENV adsorption packing was selected to further purify the crude arbutin extract. ENV filler is a polystyrene-divinylbenzene copolymer material, which has a good adsorption effect on arbutin in aqueous solution, but basically has no adsorption on large polar substances such as sugars, and the adsorption on ENV Arbutin is easily eluted by 10% methanol solution, and other impurities adsorbed on the ENV filler require a higher concentration of methanol to be eluted, so as to achieve a good purification effect.

Specific experimental steps: take 24g of ENV filler and pack it into a column (column volume is about 64mL), activate the column with methanol of 1 to 1.5 times the column volume and water of 1 to 2 times the column volume in sequence, and take 3.0g of bear that has been preliminarily purified by LSA-900B The crude extract of fructoside was dissolved in 60mL of water, filtered, the filtrate was purified through the column, the effluent was collected, rinsed with 2 times the column volume of water, the content of arbutin in the sample effluent was lower than 0.005mg/mL, discarded Remove the effluent, then elute with 10 times the column volume of 10% methanol, collect 1 times the column volume of the eluate (numbered 1-10) each time, and keep the flow rate at 2mL/min throughout the process, and the eluent obtained from the first three elutions The content of arbutin in the eluate is the highest, which are 2.9mg/mL, 4.9mg/mL, and 1.8mg/mL respectively. The content of arbutin in the eluate from the fourth elution is already low, only 0.05mg /mL, starting from the eluate obtained from the fifth time, the eluate is mainly composed of other components. Therefore, according to the detection situation, the eluate obtained from the first three times was collected and concentrated to obtain about 0.84g of arbutin crude product with high purity (in a solid state). After testing, the arbutin content was about 85%.

Step 4, recrystallization to obtain arbutin monomer

Take about 0.84g of relatively pure arbutin crude product, add 50mL of ethyl acetate, heat and reflux for 1h, filter while it is hot, and let it stand overnight, a white powdery solid is precipitated, filtered, and dried to obtain about 0.4g of a white powdery solid. The content of arbutin in the powdery solid is greater than 95%. If you need to prepare arbutin with higher purity, you can repeat the recrystallization and recrystallize 3 times, and the purity of arbutin can reach more than 99%.

Step 5. Confirmation of arbutin

The isolated arbutin was confirmed by high performance liquid chromatography, mass spectrometry, infrared spectrum and nuclear magnetic resonance H spectrum and C spectrum, all of which can correspond to the standard library.

Shaanxi Province is a large province of fruit production, in which pear trees are planted in an area of nearly one million mu, and pear leaves are a by-product of pear tree planting, which has a very rich source and low cost.

Claims (3)

1. from leaf of pear tree, extract the method for arbutin, it is characterised in that, from leaf of pear tree, extract the leaf juice containing arbutin, obtain arbutin through concentrated, purification and recrystallization, specifically comprise the following steps:

Step 1, after leaf of pear tree oven dry, pulverizing, with methyl alcohol dipping, filters, by filtrate simmer down to medicinal extract;

Step 2, get LSA-900B resin dress post, by step 1 gained medicinal extract water dissolution, filtering, in filtrate, arbutin content is 2mg/mL, column purification on filtrate, with different concns methyl alcohol drip washing, maintenance flow velocity 0.4��0.5 times of column volume/hour, obtain scavenging solution, concentrate to obtain arbutin crude extract, wherein arbutin content 30%��34%;

Step 3, gets ENV filler dress post, is purified by post on step 2 gained arbutin crude extract again, and with the water wash of 2 times of column volumes, in loading effluent liquid, arbutin content is all lower than 0.005mg/mL, abandons effluent liquid; Again by 10% methanol-eluted fractions of 10 times of column volumes, collecting the elutriant of 1 times of column volume, whole process flow velocity keeps 2��3mL/min every time; In first three wash-out gained elutriant, arbutin content is the highest, is respectively 3.0mg/mL, 4.8mg/mL, 1.6mg/mL, collects the elutriant of first three wash-out gained, concentrated, obtains solid state arbutin crude product, and its arbutin content is greater than 82%;

Step 4, step 3 gained arbutin crude product is carried out crystallization, and arbutin crude product adds ethyl acetate, reflux 0.5��1h, filtered while hot, hold over night, precipitates out white powder solid, filters, dry, obtaining white powder solid, be arbutin, in this pulverulent solids, arbutin content is greater than 95%.

2. from leaf of pear tree, extract the method for arbutin as claimed in claim 1, it is characterised in that: also comprising step 5, step 5 is for carry out recrystallization to step 4 gained arbutin.

3. from leaf of pear tree, extract the method for arbutin as claimed in claim 1 or 2, it is characterised in that, in step 1, yield of extract 7%��10%; Arbutin content 6%��10% in medicinal extract.