NL2029678A - Method for purifying myricetin from myrica rubra leaf - Google Patents

Abstract

The present disclosure disclose a method for purifying myricetin from myrica rubra leaf, comprising the following steps: leaching myrica rubra leaf with ethanol after pulverizing, to obtain an ethanol extract, said ethanol extract contains chlorophyll, 5 myricetin and myricetin glucoside; after adding a distilled water and chlorophyllase into the ethanol extract, conducting an enzymolysis, thereby decomposing chlorophyll; adding an acidic auxiliary into an enzymatic hydrolysate for acidification, converting myricetin glucoside to myricetin; removing ethanol from 10 extract after the acidic conversion by rotary evaporation, after adding a distilled water, standing, purifying the myricetin crude extract obtained, to obtain a myricetin. The present disclosure excludes interference of chlorophyll by enzymolysis of chlorophyllase, further combining with a separation and 15 purification by a macroporous resin, to obtain a high purity myricetin (purity295%). (+ Fig. l)

Description

P781/NLpd

METHOD FOR PURIFYING MYRICETIN FROM MYRICA RUBRA LEAF

TECHNICAL FIELD The present disclosure relates to a method for extracting and purifying myricetin from myrica rubra leaf.

BACKGROUND ART Larycitrin, also known as myricetin or myricetol, has a chem- ical name of 5,7-trihydroxy-2-{(3,4,5-trihydroxyphenyl) -4H-1- bezofuran-4-one, and a molecular formula of Cl1:H:50:, and a molecu- lar weight of 318.24. Myricetin is insoluble in water, and freely soluble in organic solvents such as methanol, ethanol, and ace- tone. Lots of Chinese domestic and foreign scientific researches show that, myricetin has multiple physiological functions such as antioxidation, decreasing blood glucose, protecting liver, anti- inflammation, and skin whitening. U.S. FDA has approved myricetin for use in the fields of cosmetics, food, health care products and medicine.

Myricetin widely exists in multiple plant leaves, but the content of myricetin in the plant leaves is low. According to lit- erature reports, its content in plant leaves such as vine tea, Am- pelopsis grossedentata, bayberry is high, and patents concerning separation and purification of myricetin have been disclosed. But because the solubility of chlorophyll and myricetin in the plant leaves are similar, chlorophyll severely impacts extraction and purification of myricetin.

Chinese patent CN200510034824 disclose a method for extract- ing myricetin from stem and leaf of Ampelopsis grossedentata, wherein conducting a twice extraction by using aqueous ethanol and a solvent with medium polarity, and conducting a purification by using polyamide and a macroporous resin, to obtain myricetin with a purity of 80%; this technology can not completely exclude inter- ference by chlorophyll, resulting in low purity of the myricetin prepared. Chinese Patent CN200610019693 disclose a method for ex- tracting and preparing myricetin from vine tea and other ampelop-

sis, wherein extracting myricetin by using a boiled water, and ex- cluding interference by chlorophyll, then undergoing concentration and crystallization, to obtain a high purity myricetin; but myri- cetin is extremely unstable at high temperature, resulting in a serious drop in yield, and solubility of myricetin in hot water is low, requiring large amounts of water and electric energy. Chinese Patent CN102040576 disclose a method for extracting myricetin from branch and leaf of bayberry, wherein conducing an enzymolysis of branch and leaf of bayberry, the enzyme used is one or more of cellulase, P-glucanase, emulsin and amylase, and extracting with a 95% aqueous ethanol, then conducting a purification by high-speed countercurrent chromatography and meanwhile removing chlorophyll, to obtain high purity myricetin; but the high-speed countercurrent chromatography purification adopted by this technology has low ef- ficiency and high cost, it is only applicable to laboratory re- search, inapplicable to large-scale mass production, and consumes organic solvent in a large amount, thereby polluting the environ- ment. Therefore, there is an urgent need to develop a new technol- ogy for excluding interference of chlorophyll on extracting and purifying myricetin from plant leaves.

There are multiple methods for decomposing chlorophyll, in- cluding light, acid, alkaline, oxygen, oxidant, etc., but solubil- ity of the decomposed products resulting from these methods are similar to that of chlorophyll, it is unable to eliminate the ad- verse impact of chlorophyll by these methods.

The technical problem to be solved by the present disclosure is providing a method for purifying myricetin from myrica rubra leaf, this method aims at the problem in which separating and pu- rifying myricetin from plant leaves (particularly myrica rubra leaf) is susceptible to chlorophyll, the method excludes chloro- phyll interference by enzymolysis of chlorophyllase, and further combines with separation and purification by a macroporous resin, thereby obtaining a myricetin with high purity (purity=95%).

To solve the above technical issue, the present disclosure provides a method for purifying myricetin from myrica rubra leaf, comprising the following steps:

1) extraction: leaching myrica rubra leaf with ethanol after pulverizing, to obtain an ethanol extract, said ethanol extract contains chlorophyll, myricetin and myricetin glucoside; 2) chlorophyll decomposition: adding a distilled water and a chlorophyllase into the ethanol extract obtained at step 1}, to for a reaction system, the content of chlorophyllase in said reac- tion system is 50-200 U/ml; enzymolyzing the reaction system at 30~60°C (preferably 40~60°C) for 1-2 hours, thereby decomposing the chlorophyll, to obtain an enzymatic hydrolysate; the chlorophyll decomposition is a complete decomposition, which obtains chlorophyllide and phytol (phytol); 3) acidic conversion: adding an acidic auxiliary into the en- zymatic hydrolysate obtained at step 2), until pH is 1~3 (prefera- bly 1~2), then acidifying at room temperature for 1~2 hours, con- verting a myricetin glucoside (complete conversion) into myrice- tin, to obtain an extract after acidic conversion; said acidic auxiliary is a volatile acid; 4) extraction and liquid separation: removing ethanol by a rotary evaporation of the extract after acidic conversion obtained at step 3), adding a distilled water with 2~5 fold weight of myri- ca rubra leaf at step 1), after mixed well, standing at room tem- perature (the standing time is about 8~12 minutes), taking the precipitate obtained by standing, drying, to obtain a myricetin crude extract; namely, let it stand such that the myricetin crude extract sinks to the bottom, phytol floats on upper part of the water layer, and chlorophyllide is dissolved in a middle water layer; after removing the phytol and the chlorophyllide via liquid sepa- ration and filtration, drying, to obtain a myricetin crude ex- tract; note: the products resulting from above step 1) ~ step 3) all pass into the next step; 5) purification: purifying the myricetin crude extract, to obtain a myricetin (purity295%). As an improvement of the method for purifying myricetin from myrica rubra leaf according to the present disclosure, the purifi-

cation at step 5) is: in accordance with a ratio of material to solvent of 2.0~5.0 mg/mL, dissolving the myricetin crude extract in a 30% aqueous ethanol, firstly filtrating (to prevent leaf re- sidue being left, and protect adsorption column), and adsorbing the filtrate obtained with an adsorption column filled with the macroporous resin, then eluting with 2 column volumes of a 40% aqueous ethanol, discarding the eluent, and continuing eluting with 2 column volumes of a 60% aqueous ethanol and collecting the eluent, removing ethanol by rotary evaporation, forming a deposit, and drying this deposit (50°C), to obtain myricetin (purity=z95%).

Namely, after removing ethanol by the rotary evaporation, be- cause the myricetin is insoluble in water, it is precipitated; filtrating, collecting the precipitate (deposit), drying, to ob- tain myricetin (purity295%).

As a further improvement of the method for purifying myrice- tin from myrica rubra leaf according to the present disclosure: said volatile acid at step 3) is hydrochloric acid, formic acid.

As a further improvement of the method for purifying myrice- tin from myrica rubra leaf according to the present dis- closure:said macroporous resin at step 5) is D101 type, AB-8 type or HPD500 type macroporous resin.

As a further improvement of the method for purifying myrice- tin from myrica rubra leaf according to the present disclosure:the filtration at step 5) is passing through a filter screen of 500 meshes.

As a further improvement of the method for purifying myrice- tin from myrica rubra leaf according to the present disclosure: said step 1) is: pulverizing the myrica rubra leaf to 50-200 mes- hes, and in accordance with a weigh ratio of 1:5~10, leaching the myrica rubra leaf by adding ethanol into it, then filtrating, the leaching temperature is room temperature, the leaching number is 2, the filter screen is 500 meshes, time of each leaching is 1 hour, combining the extracts to obtain an ethanol extract.

At step 2) of the present disclosure, the distilled water is mainly used for the solute precipitated after completely removing ethanol from the extract after the rotary evaporation and the aci- dic conversion at a subsequent step 4) will not agglomerate. In general, 0.25+0.05 kg of distilled water is used per 1 kg of myri- ca rubra leaf powder.

Chlorophyllase is an esterase existing in chloroplast, it is able to hydrolyze chlorophyll into a chlorophyllide of carboxylic 5 acid and a higher monohydric alcohol phytol. The solubility of chlorophyllide and phytol resulting from chlorophyllase decomposi- tion are greatly different from that of chlorophyll, chlorophyl- lide has a strong hydrophilicity, it can be removed via water ex- traction, and phytol has a very strong lipid solubility, insoluble in water, it is in liquid state at normal temperature, its density is lower than water, it can be removed by water-liquid separation.

Namely, at normal temperature, the physical condition of chlorophyll is different from that of phytol, chlorophyll is in solid state, and phytol is in liquid state (its density is less than water); at normal temperature myricetin is in solid state. The three are insoluble in water, if chlorophyll and myricetin are dispersed in water, after standing both sink to bottom layer; and phytoland myricetin is dispersed in water, after standing phytol floats on the water layer, and myricetin sinks to the bottom lay- er, achieving the purpose of separation.

The present disclosure decomposes chlorophyll by using chlo- rophyllase based on the above-mentioned principle, and removes chlorophyllide and phytol by a distilled water extraction and a liquid separation, then further purifies and prepares high purity myricetin by using the macroporous resin.

In the present disclosure, the chlorophyll decomposition must be conducted firstly, then the acidic conversion is conducted; if the order is changed, namely, if the acidic conversion is firstly conducted, the acidity of the ethanol extract is too low, which may inactivate the chlorophyllase, the goal of decomposing chloro- phyll will not be achieved.

Compared with the prior art, the present disclosure has the following technical advantages: Decomposing chlorophyll with chlorophyllase, and removing chlorophyll decomposition product by the distilled water extrac- tion, excluding its adverse impact on myricetin purification, the yield and purity of myricetin obtained are both high; the opera-

tion is simple, without the need of extra use of organic solvent, being green and safe.

BRIEF DESCRIPTION OF THE DRAWINGS The specific embodiments according to the present disclosure will be further illustrated in detail below in conjunction with the accompanying drawings.

FIG. 1 is a HPLC chromatogram of myricetin prepared by the present disclosure.

FIG. 2 is a HPLC chromatogram of a myricetin purchased from Sigma Company, purity of the myricetin purchased is 298.0%, and article number is 72576.

DETAILED DESCRIPTION OF THE EMBODIMENTS In order to make the technical solution of the invention more clear, the specific embodiments of the invention are further de- scribed below, but they are not intended to limit the invention.

Enzyme content of chlorophyllase is about 16 U/mg. Mass fraction of concentrated hydrochloric acid is about 37%.

Example 1. A method for purifying myricetin from myrica rubra leaf, wherein the following steps are successively conducted: (1) extraction (leaching) :myrica rubra leaf was passed through a screen with 100 meshes after pulverizing, 1.0 kg of my- rica rubra leaf powder was weighted, and 5.0 kg of ethanol was added, leached for 1 hour at room temperature then filtered with a filter screen of 500 meshes, to separately obtain an extract I and a filter residue; replacing myrica rubra leaf with the filter res- idue, the above leaching was repeated, to obtain an extract IO, the extracts resulting from 2 leaching (extract I, extract I) were combined, to obtain an ethanol extract; this ethanol extract con- tained chlorophyll, myricetin and myricetin glycoside, etc.

(2) chlorophyll decomposition: 0.25 kg of distilled water and a suitable amount (about 40 g)} of chlorophyllase were successively added to all ethanol extracts resulting from step (1), such that the emzyme content in the extract was 50 U/ ml, an enzymolysis was conducted at 40°C for 2 hours, such that chlorophyll was complete- ly decomposed, to obtain an extract in which chlorophyll was de- composed completely; (3) acidic conversion: a suitable amount of concentrated hy- drochloric acid (about 50 mL) was added into all of the enzymatic hydrolysate (an extract in which chlorophyll was decomposed com- pletely) obtained at step (2), pH of the system was adjusted to

1.4; and reacted at room temperature for 1 hour, and myricetin glycoside was converted to myricetin by an acid catalysis; to ob- tain an extract after acidic conversion; the acidic conversion at this step was used for converting the myricetin glycoside to myri- cetin, improving the yield and concentration.

(4) extraction: ethanol was completely removed from all of the extracts after the acidic conversion obtained at step (3) by a rotary evaporation at 40°C, and 5.0 kg of distilled water was ad- ded, standing for 10 minutes after being mixed well, myricetin crude extract sinked to the bottom, the phytol floated on upper part of the water layer, and chlorophyllide was dissolved in a middle water layer; after the upper liquid was separated and dis- carded, the water solution (middle water layer) was removed by centrifugation, namely, phytol and chlorophyllide were removed by liquid separation and filtration; the precipitate was dried at 50°C to a constant weight, to obtain a myricetin crude extract.

(5) purification: the myricetin crude extract was dissolved in a 3.0 mg/mL solution prepared from a 303 aquecus ethanol, after filtration with a filter screen of 500 meshes, 5 L was taken and loaded onto an adsorption column {50x6 cm) filled with macroporous resin D101 (about 900 g), then eluted with 2 column volumes (about

2.0 L) of 40% aqueous ethanol, an 40% ethanol eluent was discard- ed, then eluted with 2 column volumes (about 2.0 L) of 60% aqueous ethanol, collecting a 60% ethanol eluent.

After the 60% ethanol eluent was removed by rotary evapora- tion at 40°C, a high concentration myricetin was precipitated, the precipitate was filtered and collected, dried at 50°C to constant weight, to obtain myricetin.

1.0 kg of myrica rubra leaf corresponded to obtaining 48.4 g of myricetin, namely, the yield is 4.8%.

0.5 mg of myricetin obtained was accurately weighted, dis- solved in 10 mL ethanol, passed through a 0.22 pm filter membrane, the purity detected by HPLC was 98.4%, the HPLC chromatogram was as shown in FIG. 1.

The HPLC detection method is as follow: liquid chromatograph is Waters e2695 chromatograph, detector is Waters 2489 ultravio- let-visible light detector, detection wavelength is 360 nm, chro- matographic column is Eclipse XDB-C18 chromatographic column (250 mmx4.6 mm, 5.0 um; Agilent), column temperature is 30°C, sample size is 10 pL, elution velocity is 1.0 mL/min; mobile phase is methanol (A) and acetonitrile (B) containing 0.1% formic acid, namely, (A) consists of 0.1% formic acid and 99.9% of methanol, (B) consists of 100% acetonitrile, and % is volume%; elution gra- dient: 0-45 min, 10%-35% B; the peak area obtained is used for calculating purity of myricetin by using a curvilinear equation calibrated by myricetin standard substance (HPLC chromatogram is as shown in FIG. 2), the curvilinear equation is as follow: A = 64.82p + 140.38 (R® = 0.9994); A is peak area of myricetin {(mAU*min), p is concentration of myricetin (mg/mL).

Example 2. Macroporous resin D101 in Example 1 is changed to AB-8 type, HPD500 type macroporous resin, the remaining is same as Example 1.

A comparison of yield and purity obtained in the above- mentioned example with Example 1 is as shown in the following Ta- ble 1.

Table 1 ey Example 1 | Macroporous resin 4.8% 98.4% ri BA I Example 2 | AB-8 type macroporous 4.6% 96.9% me 1 [vr HPD500 type 4.6% 96.2% macroporous resin CT

Comparative example 1. Macroporous resin D101 in Example 1 is changed to Amberlite XAD-7 type macroporous resin, and HPD100 type macroporous resin, the remaining is same as Example 1. In case of Amberlite XAD-7 type macroporous, purity of myri- cetin is only 73.4%; In case of HPD100 type macroporous resin, purity of myricetin is only 78.5%. Example 3. Concentrated hydrochloric acid at step (3) in Ex- ample 1 is changed to formic acid, and its use amount is corre- spondingly changed, and pH of the system is about 2. The remaining is same as Example 1. Comparative example 2. Concentrated hydrochloric acid at step 3) in Example 1 is changed to sulfuric acid or nitric acid, and its use amount is correspondingly changed, to ensure pH of the system unchanged, being still 1.4. The remaining is same as Exam- ple 1. A comparison of yield and purity obtained in the above- mentioned example with Example 1 is as shown in the following Ta- ble 2. Table 2 Example 1 Concentrated hydro- 4.8% 98.4% er mm Note: Adopting a non-volatile acid such as sulfuric acid or nitric acid may also result in acidity of the extraction distilled water being too low, and converting chlorophyllide into phoeophor- bide greatly decreases its use amount, thereby increasing consump- tion of distilled water in the extraction.

Example 4-1. The use amount of chlorophyllase in Example 1 was increased; such that the enzyme content in the extract ob- tained was about 100 U/mL, an enzymolysis was conducted at 40°C for

1.5 hours; the remaining was same as Example 1. Yield of myricetin was 4.7%, and purity was 98.1%. Example 4-2. The use amount of chlorophyllase Example 1 was increased; such that the enzyme content in the extract was about 200 U/mL, an enzymolysis was conducted at 60°C for 1 hour, the re- maining is same as Example 1. Yield of myricetin was 4.6%, and purity was 98.7%. Finally, it should also be noted that, the above mentioned are only several specific examples of the present disclosure.

Ob- viously, the present disclosure is not limited to the above exam- ples, it may also have many variants.

All variants which are di- rectly educed by or occur to those of ordinary skill in the art from disclosure of the present disclosure should be regarded as the protection scope of the present disclosure.

Claims (6)

CONCLUSIONS A method for purifying myricetin from myrica rubra leaf, comprising the steps of: 1) extraction: leaching myrica rubra leaf with ethanol after pulverization, to obtain an ethanol extract, which ethanol extract contains chlorophyll, myricetin and myricetin glucoside; 2) chlorophyll decomposition: adding distilled water and chlorophyllase to the ethanol extract to form a reaction system, wherein the content of chlorophyllase in the reaction system is 50-200 U/ml; conducting enzymolysis on the reaction system at 30~60°C for 1~2 hours, degrading chlorophyll, to obtain an enzymatic hydrolyzate; 3) acid conversion: adding an acidic vehicle to all of the enzymatic hydrolyzate obtained in step 2) until the pH is 1-3, then acidifying at room temperature for 1-2 hours, converting myricetin glucoside to myricetin, to obtain an extract after acid conversion; wherein the acidic excipient is a volatile acid; 4) extraction and liquid separation: removing ethanol from all extract after acid conversion as obtained in step 3) by rotary evaporation, adding distilled water with 2~5 fold weight of myrica rubra leaf in step 1), allowing to stand at room temperature after being mixed well, taking a precipitate obtained by standing and drying, to obtain a crude myricetin extract; 5) purification: purifying the crude myricetin extract, to obtain a myricetin. The method of purifying myricetin from myrica rubra leaf according to claim 1, wherein the purification of step 5) is: according to a ratio of material to solvent of 2.0~5.0mg/ml, dissolving the crude myricetin extract in a 30% aqueous ethanol, filtering first, adsorbing the obtained filtrate through an adsorption column filled with a macroporous resin, then eluting with 2 column volumes of 40% aqueous ethanol, discarding an eluent, continuing eluting with 2 column volumes of 60% aqueous ethanol, and collecting the eluent , removing ethanol by rotary evaporation, forming a starting material, and drying this starting material, to obtain myricetin. The method for purifying myricetin from myrica rubra leaf according to claim 2, wherein the volatile acid in step 3) is hydrochloric acid, formic acid. The method for purifying myricetin from myrica rubra leaf according to claim 3, wherein the macroporous resin in step 5) is a macroporous resin of D101 type, AB-8 type or HPD500 type. The method of purifying myricetin from myrica rubra leaf according to claim 4, wherein the filtration in step 5) is passing through a 500 mesh filter screen. The method of purifying myricetin from myrica rubra leaf according to any one of claims 1 to 5, wherein: the step 1) is: pulverizing myrica rubra leaf to 50 ~ 200 mesh, according to a weight ratio of 1 : 5~10, adding ethanol to the pulverized myrica rubra leaf and leaching, then filtering, the leaching temperature is room temperature, the leaching number is 2, passing it through a 500 mesh filter screen, measuring the time duration of each leaching 1 hour, combining the extracts, to obtain an ethanol extract.