High-efficiency extraction and conversion method of oligomeric proanthocyanidins and its application

Abstract

The invention relates to the technical field of plant chemistry, and in particular to an efficient extraction and conversion method for oligomeric proanthocyanidins and an application thereof. The method comprises mixing a proanthocyanidin polymer and a low eutectic solvent, eluting the mixed solution through resin adsorption, and drying the eluate to obtain the oligomeric proanthocyanidins. Compared with the prior art, the conversion method of the invention is novel, simple and fast, and realizes one-pot conversion. The obtained proanthocyanidin extraction rate is higher than that of most traditional ethanol and methanol proanthocyanidins. The obtained proanthocyanidins have an average polymerization degree of 3.19, which is oligomeric proanthocyanidins and is lower than the polymerization degree of most traditional ethanol and methanol proanthocyanidins. The obtained oligomeric proanthocyanidins have important significance for product development in other fields such as the medical field, the cosmetic field, and the food industry field.

Description

Technical Field

[0001] The invention relates to the technical field of plant chemistry, and in particular to a method for efficiently extracting and converting oligomeric proanthocyanidins and an application thereof. Background Art

[0002] Proanthocyanidins are polyphenolic compounds polymerized from flavan-3-ol monomers, whose dimers to tetramers are oligomers, and pentamers and above are polymers. Proanthocyanidins have multiple biological activities such as antioxidant, anti-tumor, antihypertensive, and hypolipidemic. The bioavailability and biological activity of proanthocyanidins in the body are closely related to their structure and degree of polymerization. Oligomeric proanthocyanidins have strong biological activity and can be quickly absorbed by the body, and their bioavailability can reach more than 90%. However, most proanthocyanidins in nature exist in the form of polymers. Due to their large molecules, polymers are difficult to penetrate biological membranes and enter cells, and their bioavailability and antioxidant activity are low, which limits their application in the fields of medicine and food. Therefore, it is of great practical significance to develop an effective method to convert proanthocyanidin polymers into oligomers to improve their bioavailability and application value. Summary of the invention

[0003] In order to solve the problem of conversion of proanthocyanidin polymers to oligomers, the present invention provides an efficient extraction and conversion method for oligomeric proanthocyanidins and its application, which significantly improves the bioavailability of proanthocyanidins without destroying the active ingredients of proanthocyanidins by utilizing a low eutectic solvent.

[0004] The invention discloses an efficient extraction and conversion method of oligomeric proanthocyanidins, comprising a conversion process of proanthocyanidin polymers and a post-treatment process of an oligomeric proanthocyanidin mixed solution, wherein the conversion process of the proanthocyanidin polymers is to mix the proanthocyanidin polymers with a low eutectic solvent to obtain an oligomeric proanthocyanidin mixed solution;

[0005] The proanthocyanidin polymer is a high-polymer proanthocyanidin or a plant powder containing a high-polymer proanthocyanidin;

[0006] The solid-liquid ratio of the proanthocyanidin polymer to the low eutectic solvent is 1:5 to 1:100;

[0007] The deep eutectic solvent comprises a hydrogen bond acceptor and a hydrogen bond donor;

[0008] The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor in the deep eutectic solvent is 1:1 to 1:10;

[0009] Wherein, the hydrogen bond acceptor is choline chloride or betaine; the hydrogen bond donor is lactic acid, urea, malic acid, triethanolamine, ethylene glycol, glycerol, propylene glycol, butanediol, hexanediol, levulinic acid, xylitol or tartaric acid.

[0010] Furthermore, the plant powder containing high-polymer proanthocyanidins is obtained by grinding and sieving the plant powder containing high-polymer proanthocyanidins, washing it and then drying it.

[0011] Among them, the plants containing high-polymer proanthocyanidins include any one of grape vines, grape seeds, grape skins, blueberries, blueberry leaves, black wolfberries, pine barks, pine needles, hawthorn leaves, sour jujube leaves, blueberries, pomegranate peels, litchi peels, white thorn fruits, oil tea shells, black fruit rowan, chestnut shells, peanut skins, and the bark of the coastal pine plant of the Pinus genus of the Pinaceae family; the plant powder is ground and sieved into 20-100 meshes.

[0012] Furthermore, the plant powder is dried by any one of oven drying, air drying, shade drying, reduced pressure drying, and microwave drying, the drying temperature is 40° C.-90° C., and the drying time is 12-48 hours.

[0013] Further, the deep eutectic solvent includes any one of choline chloride / lactic acid, choline chloride / urea, choline chloride / malic acid, choline chloride / triethanolamine, choline chloride / ethylene glycol, choline chloride / glycerol, choline chloride / propylene glycol, choline chloride / butylene glycol, choline chloride / hexanediol, choline chloride / levulinic acid, choline chloride / xylitol, choline chloride / tartaric acid, betaine / lactic acid, betaine / urea, betaine / malic acid, betaine / triethanolamine, betaine / ethylene glycol, betaine / glycerol, betaine / propylene glycol, betaine / butylene glycol, betaine / hexanediol, betaine / levulinic acid, betaine / xylitol and betaine / tartaric acid.

[0014] Furthermore, the mixing method in step 1 is any one of stirring mixing, ultrasonic mixing, microwave mixing and high-pressure mixing.

[0015] Preferably, the stirring and mixing is carried out in a stirrer at a stirring rate of 50-200 r / min, a stirring temperature of 30-90° C., and a stirring time of 1-8 h; more preferably, the temperature is 50-80° C. and the time is 2-5 h.

[0016] Preferably, the ultrasonic mixing is carried out in an ultrasonic generator with an ultrasonic power of 100-5000 W, a time of 0.5-10 h, and a temperature of 20-80°C.

[0017] Preferably, the microwave frequency of the microwave mixing is 1000-3000Mhz, the microwave power is 500-1000W, and the time is 5-30min.

[0018] Preferably, the pressure range of the high-pressure mixing is 50-200 MPa, the temperature range is 25-80° C., and the time range is 5-60 min.

[0019] Furthermore, the post-treatment process of the oligomeric proanthocyanidins mixed solution is to subject the oligomeric proanthocyanidins mixed solution to a resin adsorption→solution elution→drying treatment process to obtain the oligomeric proanthocyanidins.

[0020] Furthermore, the resin in the resin adsorption is a macroporous resin, including any one of ADS-17, AB-8, ISA-10, HPD-100, HPD-400, and D-101 resins.

[0021] Furthermore, the eluent in the solution elution is 10%-90% ethanol.

[0022] Furthermore, the drying treatment method includes any one of freeze drying, vacuum drying, oven drying, supercritical drying, and spray drying.

[0023] Preferably, the freeze drying is carried out in a freeze drying box, with a drying time of 36-48 hours, a vacuum degree of -0.06MPa, and a temperature of -10 to -30°C.

[0024] Preferably, the vacuum drying is carried out in a vacuum drying oven, with a drying time of 48-96 hours, a vacuum degree of -0.08 MPa, and a temperature of 30-90°C.

[0025] Preferably, the oven drying is carried out in a normal pressure drying oven, with a drying time of 48-96 hours and a temperature of 30-90°C.

[0026] Preferably, the supercritical drying is to place the wet sample in a supercritical fluid with a pressure of 100-400 bar, a temperature of 40-100°C, a collector temperature of -50-0°C, a CO2 flow rate of 1-5 L / min, and a drying time of 1-6h.

[0027] Preferably, the inlet air temperature of the spray drying is 120°C-200°C, the outlet air temperature is 60°C-90°C, the feed flow rate is 10 ml / min-50 ml / min, the atomization air pressure is 1.5 bar-3 bar, and the drying air flow rate is 300 m³ / h-600 m³ / h.

[0028] Based on the above-mentioned efficient extraction and conversion method of oligomeric proanthocyanidins, the present invention prepares oligomeric proanthocyanidins.

[0029] Furthermore, the oligomeric proanthocyanidins are used in the fields of medicine, cosmetics or food industry.

[0030] The advantages of the present invention are:

[0031] 1. The present invention provides an efficient extraction and conversion method for oligomeric proanthocyanidins. The proanthocyanidin extraction rate obtained by the preparation method is 5.30 mg / g, which is higher than most traditional ethanol and methanol proanthocyanidin extraction rates.

[0032] 2. The present invention provides an efficient extraction and conversion method for oligomeric proanthocyanidins. The proanthocyanidins prepared by the preparation method have an average degree of polymerization of 3.19, which is lower than the degree of polymerization of most traditional ethanol and methanol proanthocyanidins.

[0033] 3. The present invention provides a highly efficient extraction and conversion method for oligomeric proanthocyanidins. The preparation method is novel, has few steps, is simple and quick, and realizes one-pot conversion.

[0034] 4. The present invention develops a one-pot DES method for efficiently extracting and converting oligomeric proanthocyanidins, which is of great significance for the product development of oligomeric proanthocyanidins in other fields such as the pharmaceutical field, the cosmetic field, and the food industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The extraction rate and degree of polymerization of proanthocyanidins corresponding to different deep eutectic solvents;

[0036] Figure 2 It is the total ion peak spectrum of the compound determined by HPLC-ESI-MS / MS;

[0037] Figure 3 This is the primary mass spectrum of catechins in the compound determined by HPLC-ESI-MS / MS;

[0038] Figure 4 It is the primary mass spectrum of proanthocyanidin B3 in the compound determined by HPLC-ESI-MS / MS;

[0039] Figure 5 It is the primary mass spectrum of proanthocyanidin C1 in the compound determined by HPLC-ESI-MS / MS;

[0040] Figure 6 It is the primary mass spectrum of B-type proanthocyanidin tetramer 1 in the compound determined by HPLC-ESI-MS / MS;

[0041] Figure 7 It is the primary mass spectrum of cyano-3-O-rutinoside in the compound determined by HPLC-ESI-MS / MS. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the invention to clearly and completely describe the technical solutions in the embodiments of the invention. Obviously, the described embodiments are only part of the embodiments of the invention, not all of them. Based on the embodiments in the invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the invention.

[0043] It should be noted that the various technical terms mentioned in the invention are all technical terms that have long been clearly known in the relevant technical field, so no further explanation will be given, and it will not affect the accurate understanding of the technical solution by those skilled in the art.

[0044] Example 1 This example 1 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, specifically using plant powder containing high-polymer proanthocyanidins for conversion during the extraction process, comprising the following steps:

[0045] (1) grinding the grape vines into powder, passing through a 40-mesh sieve, washing, and drying at 90° C. for 12 h to obtain grape vine powder;

[0046] (2) accurately weighing 10 g of the sieved grape vine powder obtained in step (1) and 50 g of a choline chloride / lactic acid (1:2) low eutectic solvent into a stirrer, stirring at a speed of 50 r / min and a temperature of 80° C. for 2 h to fully mix the low eutectic solvent and the grape vine powder to obtain a mixed solution of oligomeric proanthocyanidins;

[0047] (3) The oligomeric proanthocyanidin mixed solution obtained in step (2) was passed through HPD-400 resin (diameter-to-height ratio of 1:6.5): after wet column loading, it was washed with water, and the oligomeric proanthocyanidin mixed solution was loaded. After loading, 4 BV of water was washed (1 BV of elution was 35 mL);

[0048] (4) The oligomeric proanthocyanidins mixed solution adsorbed on the resin in step (3) was eluted with 4 BV of 40% ethanol, and the eluate was rotary evaporated to remove the alcohol, and further dried in a freeze drying oven at a vacuum degree of -0.06 MPa and a temperature of -30°C to obtain oligomeric proanthocyanidins after drying for 36 hours.

[0049] The extraction rate of oligomeric proanthocyanidins in this example is 4.07 mg / g, and the degree of polymerization is 3.39.

[0050] Example 2 This example 2 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, specifically using plant powder containing high-polymer proanthocyanidins for conversion during the extraction process, comprising the following steps:

[0051] (1) grinding the grape vines into powder, passing through a 40-mesh sieve, washing, and drying at 90° C. for 12 h to obtain grape vine powder;

[0052] (2) accurately weighing 10 g of the grape vine powder obtained in step (1) and 100 g of a choline chloride / urea (1:2) low eutectic solvent, placing them in a stirrer, stirring at a speed of 50 r / min and a temperature of 80° C. for 2 h to fully mix the low eutectic solvent and the grape vine powder to obtain an oligomeric proanthocyanidin mixed solution;

[0053] (3) The oligomeric proanthocyanidin mixed solution obtained in step (2) was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): after wet column loading, it was washed with water, and the oligomeric proanthocyanidin mixed solution was loaded. After the loading was completed, it was washed with water for 4 BV (1 BV of elution was 35 mL);

[0054] (4) The oligomeric proanthocyanidins mixed solution adsorbed on the resin in step (3) was eluted with 4 BV of 60% ethanol, and the eluate was rotary evaporated to remove the alcohol, and further dried in a freeze drying oven at a vacuum degree of -0.06 MPa and a temperature of -10°C to obtain oligomeric proanthocyanidins after drying for 48 hours.

[0055] The extraction rate of oligomeric proanthocyanidins in this example is 1.85 mg / g, and the degree of polymerization is 3.96.

[0056] Example 3 This example 3 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, specifically using plant powder containing high-polymer proanthocyanidins for conversion during the extraction process, comprising the following steps:

[0057] (1) Grinding blueberries, passing through a 40-mesh sieve, washing, and drying at 90° C. for 12 h to obtain blueberry powder;

[0058] (2) Accurately weighing 10 g of the blueberry powder obtained in step (1) and 100 g of a choline chloride / malic acid (1:1) low eutectic solvent were placed in a stirrer, and stirred at a speed of 50 r / min and a temperature of 60° C. for 6 h to fully mix the low eutectic solvent and the blueberry powder to obtain an oligomeric proanthocyanidin mixed solution;

[0059] (3) The oligomeric proanthocyanidin mixed solution obtained in step (2) was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): After wet column loading, it was washed with water until there was no alcohol smell, and the oligomeric proanthocyanidin mixed solution was loaded. After the loading was completed, it was washed with water for 2 BV (1 BV of elution was 35 mL);

[0060] (4) The oligomeric proanthocyanidins mixed solution adsorbed on the resin in step (3) was eluted with 6 BV of 60% ethanol, and the eluate was rotary evaporated to remove the alcohol, and further dried in a freeze drying oven at a vacuum degree of -0.06 MPa and a temperature of -10°C to obtain oligomeric proanthocyanidins after drying for 48 hours.

[0061] The extraction rate of oligomeric proanthocyanidins in this example is 3.80 mg / g, and the degree of polymerization is 3.57.

[0062] Example 4 This example 4 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, specifically using plant powder containing high-polymer proanthocyanidins for conversion during the extraction process, comprising the following steps:

[0063] (1) Grinding pine bark into powder, passing through a 40-mesh sieve, washing, and drying at 90° C. for 12 h to obtain blueberry powder;

[0064] (2) Accurately weighing 10 g of the pine bark powder obtained in step (1) and 100 g of a betaine / lactic acid (1:2) low eutectic solvent were placed in a stirrer, and stirred at 50 r / min and 60° C. for 6 h to fully mix the low eutectic solvent and the blueberry powder to obtain an oligomeric proanthocyanidin mixed solution;

[0065] (3) The oligomeric proanthocyanidin mixed solution obtained in step (2) was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): After wet column loading, it was washed with water until there was no alcohol smell, and the oligomeric proanthocyanidin mixed solution was loaded. After the loading was completed, it was washed with water for 2 BV (1 BV of elution was 35 mL);

[0066] (4) The oligomeric proanthocyanidins mixed solution adsorbed on the resin in step (3) was eluted with 6 BV of 60% ethanol, and the eluate was rotary evaporated to remove the alcohol, and further dried in a freeze drying oven at a vacuum degree of -0.06 MPa and a temperature of -10°C to obtain oligomeric proanthocyanidins after drying for 48 hours.

[0067] The extraction rate of oligomeric proanthocyanidins in this example is 3.20 mg / g, and the degree of polymerization is 5.96.

[0068] Example 5 This example 5 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, specifically using plant powder containing high-polymer proanthocyanidins for conversion during the extraction process, comprising the following steps:

[0069] (1) grinding grape vines into powder, passing through a 40-mesh sieve, washing, and drying at 90° C. for 12 h to obtain blueberry powder;

[0070] (2) accurately weighing 10 g of the grapevine powder obtained in step (1) and 100 g of a choline chloride / triethanolamine (1:4) low eutectic solvent in a stirrer, stirring at 50 r / min and 60° C. for 6 h to fully mix the low eutectic solvent and the blueberry powder to obtain an oligomeric proanthocyanidin mixed solution;

[0071] (3) The oligomeric proanthocyanidin mixed solution obtained in step (2) was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): After wet column loading, it was washed with water until there was no alcohol smell, and the oligomeric proanthocyanidin mixed solution was loaded. After the loading was completed, it was washed with water for 2 BV (1 BV of elution was 35 mL);

[0072] (4) The oligomeric proanthocyanidins mixed solution adsorbed on the resin in step (3) was eluted with 6 BV of 60% ethanol, and the eluate was rotary evaporated to remove the alcohol, and further dried in a freeze drying oven at a vacuum degree of -0.06 MPa and a temperature of -10°C to obtain oligomeric proanthocyanidins after drying for 48 hours.

[0073] The extraction rate of oligomeric proanthocyanidins in this example is 1.39 mg / g, and the degree of polymerization is 4.79.

[0074] Example 6 This Example 6 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, specifically using plant powder containing high-polymer proanthocyanidins for conversion during the extraction process, comprising the following steps:

[0075] (1) grinding grape vines into powder, passing through a 40-mesh sieve, washing, and drying at 90° C. for 12 h to obtain blueberry powder;

[0076] (2) accurately weighing 10 g of the grapevine powder obtained in step (1) and 100 g of a choline chloride / lactic acid (1:4) low eutectic solvent and placing them in a stirrer, stirring at a speed of 50 r / min and a temperature of 60° C. for 6 h to fully mix the low eutectic solvent and the blueberry powder to obtain an oligomeric proanthocyanidin mixed solution;

[0077] (3) The oligomeric proanthocyanidin mixed solution obtained in step (2) was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): After wet column loading, it was washed with water until there was no alcohol smell, and the oligomeric proanthocyanidin mixed solution was loaded. After the loading was completed, it was washed with water for 2 BV (1 BV of elution was 35 mL);

[0078] (4) The oligomeric proanthocyanidins mixed solution adsorbed on the resin in step (3) was eluted with 6 BV of 60% ethanol, and the eluate was rotary evaporated to remove the alcohol, and further dried in a freeze drying oven at a vacuum degree of -0.06 MPa and a temperature of -10°C to obtain oligomeric proanthocyanidins after drying for 48 hours.

[0079] The extraction rate of oligomeric proanthocyanidins in this example is 4.93 mg / g, and the degree of polymerization is 3.19.

[0080] Analysis of deep eutectic solvents: First, the compositions of different deep eutectic solvents in Examples 1-6 (corresponding to DES1-6) were analyzed, and the results of viscosity, pH, molar ratio and relative polarity were obtained as shown in Table 1. The extraction rate and degree of polymerization of proanthocyanidins corresponding to different deep eutectic solvents are shown in Table 1. Figure 1 As shown, it can be seen that the extraction rate of plant proanthocyanidins extracted by choline chloride / lactic acid is the highest and the degree of polymerization is the lowest, and it is the best low eutectic solvent.

[0081] The optimal deep eutectic solvent was used to further conduct experiments on the conversion of high-polymer proanthocyanidins into low-polymer proanthocyanidins:

[0082] Example 7 This example 7 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, and the preparation method comprises the following steps:

[0083] (1) Taking 1 g of proanthocyanidin polymers in black wolfberry extract and 10 g of choline chloride-lactic acid (1:4) low eutectic solvent at a solid-liquid ratio of 1:10, stirring at 50 r / min and 37°C for 4 h to obtain a proanthocyanidin oligomer mixed solution;

[0084] (2) The obtained oligomeric proanthocyanidin mixed solution was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): wet column packing was used to wash the resin with water, and the oligomeric proanthocyanidin mixed solution was loaded. After loading, 4 BV of water was used to wash (1 BV of elution is 35 mL).

[0085] (3) The oligomeric proanthocyanidins adsorbed on the resin were eluted with 4 BV of 40% ethanol, and the eluate was rotary evaporated and then placed in a freeze drying oven at a vacuum degree of -0.06 MPa and -10°C for 36 hours to obtain oligomeric proanthocyanidins with a degree of polymerization of 2.84.

[0086] Example 8 This example 8 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, and the preparation method comprises the following steps:

[0087] (1) According to the solid-liquid ratio of 1:100, 1 g of proanthocyanidin polymer in hawthorn leaf extract and 100 g of choline chloride-lactic acid (1:4) low eutectic solvent were mixed at a speed of 25 r / min and a temperature of 60 °C for 4 h to obtain a proanthocyanidin oligomer mixed solution;

[0088] (2) The obtained oligomeric proanthocyanidin mixed solution was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): wet column loading was used to wash the resin with water until there was no alcohol smell, and the oligomeric proanthocyanidin mixed solution was loaded. After loading, 4 BV of water was washed (1 BV of elution was 35 mL);

[0089] (3) The oligomeric proanthocyanidins adsorbed on the resin were eluted with 4 BV of 40% ethanol, and the eluate was rotary evaporated and placed in a freeze drying oven at a vacuum degree of -0.06 MPa and -30°C for 36 hours to obtain oligomeric proanthocyanidins with a degree of polymerization of 3.31.

[0090] Example 9 This Example 9 provides an efficient extraction and conversion method for oligomeric proanthocyanidins, specifically using plant powder containing high-polymer proanthocyanidins for conversion during the extraction process, comprising the following steps:

[0091] (1) grinding pine bark into powder, passing through a 40-mesh sieve, washing, and drying at 40° C. for 48 hours to obtain grape vine powder;

[0092] (2) Accurately weighing 10 g of the grape vine powder obtained in step (1) and 100 g of a choline chloride / lactic acid (1:10) low eutectic solvent were placed in a stirrer, and stirred at 50 r / min and 70° C. for 4 h to fully mix the low eutectic solvent and the grape vine powder to obtain an oligomeric proanthocyanidin mixed solution;

[0093] (3) The oligomeric proanthocyanidin mixed solution obtained in step (2) was passed through AB-8 resin (diameter-to-height ratio of 1:6.5): wet column loading was used, the resin was washed with water, the oligomeric proanthocyanidin mixed solution was loaded, and after loading was completed, 4 BV of water was washed (1 BV of elution was 35 mL);

[0094] (4) The oligomeric proanthocyanidins mixed solution adsorbed on the resin in step (3) was eluted with 4 BV of 40% ethanol, and the eluate was rotary evaporated to remove the alcohol, and further dried in a freeze drying oven at a vacuum degree of -0.06 MPa and a temperature of -10°C to obtain oligomeric proanthocyanidins after drying for 48 hours.

[0095] The extraction rate of oligomeric proanthocyanidins in this example is 5.35 mg / g, and the degree of polymerization is 3.19.

[0096] Table 1 Composition, viscosity, pH, molar ratio and relative polarity of deep eutectic solvents

[0097]

[0098] The components of the oligomeric proanthocyanidins obtained using the low eutectic solvent choline chloride-lactic acid were subjected to HPLC-ESI-MS / MS liquid mass analysis, and the main component parameters are shown in Table 2. Among them, the main compounds in the oligomeric proanthocyanidins obtained in Example 9 are as follows: Figure 2 As shown, from Figure 2 The mass spectrum of oligomeric proanthocyanidins B1 / B2 / B3 and oligomeric proanthocyanidin monomer C1 can be found, and B-type proanthocyanidin tetramer 1 is also identified. At the same time, cyano-3-O-rutinoside, the precursor of proanthocyanidins, is also identified. Cyano-3-O-rutinoside is one of the main components of anthocyanidin color change, which further shows that the low eutectic solvent DES will also extract glycosides.

[0099] Table 2 Parameters of main components in oligomeric proanthocyanidins determined by HPLC-ESI-MS / MS

[0100]

[0101] For those skilled in the art, the invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the invention; therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the invention is defined by the appended claims rather than the above description, so it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions and improvements made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the technical solution of the present invention.

Claims

1. An efficient extraction and conversion method for oligomeric proanthocyanidins, characterized in that: The method comprises a conversion process of proanthocyanidin polymers and a post-treatment process of an oligomeric proanthocyanidin mixed solution, wherein the conversion process of the proanthocyanidin polymers is to mix the proanthocyanidin polymers with a low eutectic solvent to obtain an oligomeric proanthocyanidin mixed solution; The solid-liquid ratio of the proanthocyanidin polymer to the low eutectic solvent is 1:5 to 1:100; The deep eutectic solvent is a low eutectic mixture formed by a hydrogen bond acceptor and a hydrogen bond donor; The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor in the deep eutectic solvent is 1:1 to 1:10; Wherein, the hydrogen bond acceptor is choline chloride or betaine; the hydrogen bond donor is lactic acid, urea, malic acid, triethanolamine, ethylene glycol, glycerol, propylene glycol, butylene glycol, hexylene glycol, levulinic acid, xylitol or tartaric acid.

2. The efficient extraction and conversion method of oligomeric proanthocyanidins according to claim 1, characterized in that: The source of the proanthocyanidin polymer is high-polymer proanthocyanidin or plant powder containing high-polymer proanthocyanidin; the plant powder containing high-polymer proanthocyanidin is obtained by grinding and sieving the plant containing high-polymer proanthocyanidin, washing and drying; Among them, the plant containing high-polymer proanthocyanidins is any one of grape vines, grape seeds, grape skins, blueberries, blueberry leaves, black wolfberries, pine barks, pine needles, hawthorn leaves, sour jujube leaves, blueberries, pomegranate peels, litchi peels, white thorn fruits, oil tea shells, black fruit rowan, chestnut shells, peanut skins, and the bark of the coastal pine plant of the Pinus genus of the Pinaceae family; the plant powder is ground and sieved into 20-100 meshes.

3. The efficient extraction and conversion method of oligomeric proanthocyanidins according to claim 2, characterized in that: The plant powder is dried in any one of oven drying, air drying, shade drying, reduced pressure drying, and microwave drying. The drying temperature is 40° C.-90° C., and the drying time is 12-48 hours.

4. The efficient extraction and conversion method of oligomeric proanthocyanidins according to claim 1 or 2, characterized in that: The mixing method is any one of stirring mixing, ultrasonic mixing, microwave mixing or high-pressure mixing.

5. The efficient extraction and conversion method of oligomeric proanthocyanidins according to claim 1 or 2, characterized in that: The post-treatment process of the oligomeric proanthocyanidin mixed solution is to subject the oligomeric proanthocyanidin mixed solution to resin adsorption→solution elution→drying treatment to obtain the oligomeric proanthocyanidin.

6. The method for efficiently extracting and converting oligomeric proanthocyanidins according to claim 5, characterized in that: The resin in the resin adsorption is a macroporous resin, which is any one of ADS-17, AB-8, ISA-10, HPD-100, HPD-400, and D-101 resins; and the eluent in the solution elution is 10%-90% ethanol.

7. The method for efficiently extracting and converting oligomeric proanthocyanidins according to claim 5, characterized in that: The drying method is any one of freeze drying, vacuum drying, oven drying, supercritical drying and spray drying.

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