EP3233076A1

EP3233076A1 - Process for obtaining a composition enriched with dihydroquercetin or with tannins

Info

Publication number: EP3233076A1
Application number: EP15808644.7A
Authority: EP
Inventors: Chahinez AOUF; Claire MAYER; Abdellatif BARAKAT; Hélène HOH
Original assignee: Institut National de la Recherche Agronomique INRA
Current assignee: Institut National de la Recherche Agronomique INRA
Priority date: 2014-12-15
Filing date: 2015-12-15
Publication date: 2017-10-25
Also published as: FR3029917A1; US20170326189A1; WO2016096781A1; FR3029917B1

Abstract

The invention relates to a process for obtaining a conifer bark-base composition enriched with dihydroquercetin or with tannins, comprising the following steps: a) grinding dried shavings of bark from a conifer so as to obtain a ground conifer bark particle material, and b) selecting, from the ground particle material obtained in step a), the fraction of particles:- of smallest size representing at most 40% by weight, relative to the total weight of the ground particle material obtained in step a), this fraction being enriched with tannins; or - of largest size representing at most 50% by weight, relative to the total weight of the ground particle material obtained in step a), this fraction being enriched with dihydroquercetin.

Description

PROCESS FOR OBTAINING A COMPOSITION ENRICHED WITH DIHYDROQUERCETIN OR TANNINS FIELD OF THE INVENTION

The present invention relates to the field of obtaining compositions enriched in certain polyphenols, respectively dihydroquercetin or tannins.

PRIOR ART

Polyphenols, or phenolic compounds, are organic molecules, products of the secondary metabolism of plants. They are chemically characterized by the presence of several phenolic groups.

Polyphenols have been shown to have beneficial effects on human health. Indeed, their properties as natural antioxidants could play a role in the prevention and treatment of cancer, inflammatory, cardiovascular and neurodegenerative diseases. These chemical compounds are also used as additives in the food, pharmaceutical and cosmetic industries.

Among the polyphenols, the flavonoid family comprises over 6000 compounds, grouped into four main groups: flavones, flavonones and dihydrofiavonones (flavanonols), flavanols and anthocyanins.

This broad family includes both monomeric and polymeric compounds.

Tannins are polymeric compounds. There are mainly two categories of tannins: catechin tannins also called condensed tannins or procyanidins, and hydrolyzable tannins mainly comprising gallotanins and ellagitannins. On the chemical level, they consist either of oligomers or polymers of flavanols (condensed tannins), or polyols to which are attached galloyles units or their derivatives (hydrolysable tannins).

Tannins are naturally present in many plants, including grapes. They have been used for centuries in skin tanning because they have the natural property of precipitating proteins. They are also interesting for their ability to chelate metal ions and especially heavy cations. In oenology, tannins are used for fining wines because they have a strong ability to combine with proteins. The application of tannins extends to many other areas such as those of agribusiness, pharmacy, cosmetics, ceramics, and textiles.

Dihydroquercetin, also called taxifolin, is a monomeric organic compound of the flavanonol family. Flavanonols (3-hydroxyflavanone or 2,3-dihydroflavonol) are a class of flavonoids derived from 3-hydroxy-2,3-dihydro-2-phenylchromen-4-one.

Taxifolin is naturally present in acai (Euterpe oleracea), Siberian larch (Latrix sibiricd) and silymarin extracted from milk thistle seeds. Taxifolin is mainly produced by extraction in Russia.

Taxifolin has many properties potentially beneficial to health. In particular, it has been shown in vitro that taxifolin protects cell membranes, improves capillary activity and micro-circulation. It has also been shown that taxifolin possesses anti-inflammatory, anti-allergy or hepatoprotective activities. It is also known that the antioxidant properties of taxifolin are greater than those of other flavonoids or those of vitamin E. In addition, taxifolin has no mutagenic effect and has very low toxicity properties. In particular, taxifolin is even less toxic than the quercetin compound which is related to it.

Because of its many beneficial properties for health, taxifolin is widely used in the pharmaceutical field, in the food industry and in the cosmetics field.

In the pharmaceutical field, taxifolin may be prescribed in particular in complex treatments for vitamin deficiency, cardiovascular diseases, ischemic heart disease and atherosclerosis. Some studies encourage the use of taxifolin for the treatment of cancers. As regards the medical properties of taxifolin, those skilled in the art can advantageously refer to the Weidmann article (2012, European Journal of Pharmacology, Vol 684: 19-26).

In the food industry, taxifolin is used as an antioxidant, particularly in the manufacture of food products containing fat. Taxifolin is particularly used in the preparation of meat or fish products, dairy products, or confectionery. There is thus a growing demand from industry for the availability of large quantities of taxifolin. However, current production of taxifolin is insufficient to meet the needs of the market. As a result, taxifolin is marketed at very high prices.

Almost all the methods for obtaining taxifolin consist of high temperature hydro-alcoholic extraction methods, the actual extraction steps being followed by one or more purification steps of the taxifolin contained in the extracts. The purification of taxifolin extracts is mainly carried out by chromatography or by re-crystallization.

The extraction of the tannins is also carried out by the use of one or more solvents, such as acetone and ethyl acetate. It can be followed by a depolymerization step, a routine analytical method that relies on the acid-catalyzed failure of intermonomeric bonds.

An example of these known methods for extracting polyphenols by solvent, here at the laboratory scale, is illustrated by the article by Bocalandro et al. (2012, Industrial Crops and Products, Vol 38: 21-26). Bocalandro et al. disclose a process in which bark chips of Pinus radiata are subjected to a hydroalcoholic extraction step at 120 ° C. The resulting extract was then subjected to an evaporation step to remove residual ethanol. The resulting aqueous extract is filtered to separate the water-soluble polyphenolic fraction and the water-insoluble polyphenolic fraction. The water-soluble polyphenolic fraction is then lyophylized and then stored in sealed containers. Within the polyphenols that have been extracted, taxifolin is present at a rate of about 17 mg per gram of extract. Tannins are present at about 330 to 340 mg per gram of extract.

An example of obtaining taxifolin implementing a hydroalcoholic extraction step is described in European Patent Application No. EP 2 639 232. After removal of the trunk tissues, Siberian larch wood is fragmented and dried at room temperature. a temperature of 40-50 ° C until a residual moisture of 15-25% is obtained. The dried wood is then milled and the resulting sawdust is subjected to a hydroalcoholic extraction step at 40-50 ° C. The hydroalcoholic extractant is then distilled and the sawdust is mechanically pressed to recover the residual alcohol. Then the aqueous portion of the extract is cooled to remove resinous impurities. The aqueous portion of the extract free of resinous impurity is subjected to a chromatography step and the taxifolin is recovered in one or more fractions of the eluate, according to the desired degree of purity of taxifolin. Then, after evaporation of the residual ethanol, the elution product is crystallized.

Another method for obtaining taxifolin by solvent extraction is described in PCT Application No. WO 2013/137844. According to yet another method, described by Wang et al. (201 1, Food Chemistry, Vol 126: 1178-1185), the step of extracting the polyphenols is carried out, from sawdust, with an aqueous solution containing a combination of enzymes, respectively a cellulase, a pectinase and a beta-glucosidase. However, the method of Wang et al. is analytical and does not include a step of preparative separation of taxifolin from other polyphenols contained in the enzyme extract.

These methods of extraction from crushed conifer bark do not include a selection of bark particles based on their size, and no fractions enriched in dihydroquercetin and / or tannins have been identified.

It follows from the foregoing that the known methods for obtaining taxifolin and tannins comprise a plurality of pressing and intense washing steps with water or organic solvents. The implementation of these methods of obtaining taxifolin and tannins is expensive, in particular because of the large volumes of solvents required and the energy cost. In addition, the implementation of repeated extraction and separation steps may contribute to the degradation of phenolic compounds, including taxifolin, since this compound is rapidly oxidized in contact with air.

The known methods of extraction of taxifolin have, because of the aforementioned technical disadvantages, a low yield.

Similarly, there are no methods of extraction of so-called "dry" tannins, based on the pre-selection of a tannin-enriched bark fraction. There is a need in the state of the art. for the availability of methods for obtaining taxifolin and tannins, alternative or improved compared to known methods.

SUMMARY OF THE INVENTION The invention relates to a process for obtaining a composition based on coniferous bark enriched with dihydroquercetin and / or tannins, comprising the following steps:

a) crushing dried bark chips from a conifer to obtain a crushed coniferous bark particle, and

b) selecting, from the crushed particles obtained in step a), the fraction of bark particles:

- Of larger size representing at most 50% by weight, relative to the total weight of the ground material obtained in step a), this fraction being enriched in dihydroquercetin; or

- Of smaller size representing at most 40% by weight, relative to the total weight of the ground material obtained in step a), this fraction being enriched in tannins.

According to a first aspect, the present invention relates to a process for obtaining a tannin-enriched composition comprising tannin enrichment steps which are carried out dry, without requiring the use of solvent.

The present invention thus relates to a process for obtaining a tannin enriched coniferous bark composition comprising the following steps:

b) selecting, from the grind of particles obtained in step a), the fraction of particles of smaller size representing at most 40% by weight, relative to the total weight of the grind of particles obtained in step a ).

According to a variant of the process above, said method comprises the following steps:

a) crushing dried bark chips from a conifer to obtain a crushed coniferous bark particle,

bl) separating, according to their size, the bark particles contained in the ground material obtained in step a) into a plurality of fractions comprising particles of a distinct size, and b2) selecting a fraction of tannin-enriched bark particles, said fraction consisting of bark particles having a size less than 0.30 mm, and preferably bark particles having a size less than 0.16 mm.

In some embodiments of the above method, said conifer is a maritime pine.

The invention also relates to a fraction of tannin-enriched bark particles obtainable by the above process.

The invention also relates to a composition enriched in tannins that can be obtained by the above process.

According to a second aspect, the present invention relates to a process for obtaining a composition enriched in taxifolin comprising taxifoline enrichment steps which are carried out by the dry route, without requiring the use of solvent.

The present invention thus relates to a process for obtaining a composition based on coniferous bark enriched in dihydroquercetin, comprising the following steps:

b) selecting, from the grind of particles obtained in step a), the fraction of particles of larger size representing at most 50% by weight, relative to the total weight of the grind of particles obtained in step a ).

bl) separating, according to their size, the bark particles contained in the ground material obtained in step a) into a plurality of fractions comprising particles of a distinct size, and

b2) selecting a fraction of bark particles enriched in dihydroquercetin, said fraction consisting of bark particles having a size greater than 0.6 mm, and preferably bark particles having a size greater than 1 mm. In some embodiments of the above methods, the dried chips used in step a) have a size of the order of a few cm.

In some embodiments of the above methods, the grinding step a) is performed according to a method selected from (1) grinding in a knife milling device, (2) milling in a ball milling device, and (3) milling in a knife milling device followed by milling in an air jet mill.

However, as is explained later in the description, when an air jet mill device is used in step a), it is preferable to carry out in step a) a pre-grinding of the chips to the using a knife milling device and then subjecting the coarse ground material thus obtained to fine grinding with the aid of an air jet mill.

In some embodiments of the above methods, these further include a step (c) of solvent extraction of the tannins or dihydroquercetin contained in the particles of the tannin or dihydroquercetin-enriched fraction. obtained in step b) or b2).

In some embodiments of the above method, said conifer is a Douglas fir.

The invention also relates to a fraction of bark particles enriched in dihydroquercetin obtainable by the above method.

The invention also relates to a composition enriched in dihydroquercetin obtainable by the above method.

DESCRIPTION OF THE FIGURES

Figure 1: Percentage mass of each fraction of Fl bark particles (particle size greater than 1 mm), F2 (particle size less than 1 mm and greater than 0.56 mm), F3 (particle size less than 0 , 56 mm and greater than 0.16 mm) and F4 (particle size less than 0.16 mm). On the ordinate: percentage relative to the total mass of the sample of starting bark particles (fraction F0).

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an improved process for obtaining a composition enriched in certain polyphenols, and more particularly a composition enriched in dihydroquercetin and a composition enriched in tannins. It is shown according to the invention that, unexpectedly, a composition enriched in dihydroquercetin can be obtained from a particular fraction of the tissues forming the bark of a conifer. The inventors have in particular shown that certain constituent tissues of the bark of a conifer, in particular Douglas-fir, are particularly rich in dihydroquercetin. The inventors have also shown that all of these coniferous bark tissues with a high content of dihydroquercetin contain a large part of the total amount of dihydroquercetin contained in the bark of these trees.

In addition, the inventors have also shown that other constituent tissues of the bark of a conifer are particularly rich in other polyphenols, such as tannins.

The Applicant has developed a method specifically adapted for obtaining bark tissue fractions which have been identified as having a high content of certain polyphenols, and in particular respectively the high bark tissue fraction of the bark tissue. dihydroquercetin or the bark tissue fraction having a high tannin content.

Surprisingly, the Applicant has shown that the bark tissue fractions of interest can be separated from the other bark tissue fractions by grinding and then separation, according to their size, of the bark particles contained in the resulting ground material. .

The inventors have thus shown that the dihydroquercetin present in the coniferous bark is mainly located in some of the constituent tissues of this bark. It follows from the results obtained by the inventors that a composition enriched with dihydroquercetin can be obtained from coniferous bark by means of a process which would make it possible to obtain a product enriched in the tissue (s) in which which one (s) is mainly located dihydroquercetin.

Such a method, adapted for obtaining a composition based on coniferous bark, enriched with dihydroquercetin is provided according to the invention.

The inventors have also shown that the tannins present in the coniferous bark are mainly located in some of the constituent tissues of this bark. It follows from the results obtained by the inventors that a composition enriched in tannins can be obtained from coniferous bark, by means of a process which would obtain a product enriched in the fabric (s) in which (s) are mainly localized tannins.

According to a first aspect, the present invention relates to a process for obtaining a tannin-enriched coniferous bark composition comprising the following steps:

b) selecting, from the grind of particles obtained in step a), the fraction of bark particles of smaller size representing at most 40% by weight, relative to the total weight of the particle grind obtained at 1 step a).

b2) selecting a fraction of tannin-enriched bark particles, said fraction consisting of bark particles having a size less than 0.30 mm, and preferably bark particles having a size less than 0.16 mm.

According to a second aspect, the present invention relates to a process for obtaining a composition based on coniferous bark enriched in dihydroquercetin, comprising the following steps:

In these two processes, step a) of grinding can be carried out by any technique known to those skilled in the art. It may be carried out in particular, according to known techniques, using a grinding device selected from (1) a knife mill device, (2) a ball mill device, and (3) an air jet mill device. In In some embodiments of grinding step a), a combination of several of these devices is used.

Step b) of selecting the fraction of particles:

- Or smaller size representing at most 40% by weight, relative to the total weight of the ground material obtained in step a);

- or larger size representing at most 50% by weight, relative to the total weight of the ground material obtained in step a),

can be performed according to any known technique of separation of particles according to their size.

As an illustration, step b) can be carried out by sieving, using a series of successive sieves of increasingly smaller mesh size.

In this embodiment, (i) the weight of the particle grind obtained in step a) is determined, and then (ii) the sieving operation is carried out, which results in the separation of the particles of said ground material into a plurality fractions of particles of different size ranges, the weight of each fraction of particles being also determined, and then (iii) selecting the fraction or fractions comprising the smaller and / or larger particles, provided that the the weight of the selected fraction of particles, or the weight of the plurality of selected fractions, represents at most 40% or 50% of the total weight of the particulate melt obtained in step a).

As shown in the examples, the particles of the ground material obtained in step a) which are the most enriched in tannins are those which are smaller in size. As a result, the fraction of particles is selected in step b) according to, in particular, the degree of tannin enrichment of the final composition that is desired. When moderate enrichment in tannins for the final composition is desired, it is possible to select in step b) the fraction of particles of smaller size which represents at most 40% of the total weight of the ground material obtained in step at). In other situations, in which a higher degree of tannin enrichment is desired for the final composition, it is possible to select in step b) the fraction of particles of smaller size which represents at most 30% or 20% the total weight of the particle grind obtained in step a).

As shown in the examples, the particles of the ground material obtained in step a) which are the most enriched in dihydroquercetin are those which are moreover big size. As a result, the fraction of particles is selected in step b) according to, inter alia, the degree of dihydroquercetin enrichment of the final composition that is desired. When a moderate enrichment in dihydroquercetin for the final composition is desired, it is possible to select in step b) the fraction of particles of larger size which represents at most 50% of the total weight of the ground material obtained in step a ). In other situations, in which a higher degree of enrichment of dihydroquercetin is sought for the final composition, it is possible to select in step b) the fraction of particles of larger size which represents at most 40%, 30% or 20% of the total weight of the grind of particles obtained in step a).

For the purposes of the present description, a fraction of particles representing at most 40% by weight, relative to the total weight of the ground material obtained in step a), comprises a fraction of particles representing at most 39%), 38% ), 37%, 36%, 35%, 34% o, 33%, 32%, 31%, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22% , 21%, 20%, 19%, 18%), 17%), 16%) and 15% by weight, relative to the total weight of the ground material obtained in step a).

For the purpose of the present description, a fraction of particles representing at most 50% by weight, relative to the total weight of the ground material obtained in step a), comprises a fraction of particles representing at most 49% o, 48%, 47%, 46%, 45%, 44%, 43%, 42%), 41%, 40%, 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31% %, 30%, 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, and 20% by weight, based on the total weight of the particulate grind obtained from step a).

Without wishing to be bound by any theory, the applicant thinks that the selection of a fraction of particles representing more than 50% by weight, relative to the total weight of the ground material obtained in step a), leads to obtaining a final composition which is insufficiently enriched in dihydroquercetin for industrial use.

Also, the applicant is of the opinion that the selection of a fraction of particles representing less than 20% by weight, relative to the total weight of the ground material obtained in step a), results in obtaining a final composition which is substantially enriched in dihydroquercetin, but too much of the dihydroquercetin initially contained in the starting material is therefore not used. By way of illustration, for the two processes according to the invention, step a) of grinding can be carried out using a knife milling device, for example using a knife milling device equipped with a 6mm outlet grille.

According to a preferred aspect, in step b), sieving is selected either:

- A fraction of tannin-enriched bark particles, consisting of bark particles having a size less than 0.30 mm, preferably less than 0.16 mm; is

a fraction of particles having a particle size greater than 1 mm. In the embodiment of the process which is illustrated in the examples, the fraction of particles having a size of less than 0.16 mm represents approximately 16% by weight, relative to the total weight of the ground material obtained in step a) .

In the embodiment of the process which is illustrated in the examples, the fraction of particles having a particle size greater than 1 mm represents approximately 26% by weight, relative to the total weight of the ground material obtained in step a) .

The process according to the invention makes it possible to obtain compositions enriched in polyphenols, in particular in tannins or in dihydroquercetin, by means of physical enrichment steps, carried out at room temperature without the use of a solvent, thus avoiding degradation of the polyphenols of interest, specifically taxifolin. The polyphenol enrichment steps, specifically in tannins or taxifolin, of the above process, because they do not require heating or solvent, are less expensive than the known solvent extraction steps, which are performed at high temperature.

In some embodiments of the process for obtaining a dihydroquercetin enriched conifer bark composition, said method comprises the following steps:

b2) selecting a fraction of bark particles enriched in dihydroquercetin, said fraction consisting of bark particles having a size greater than 0.6 mm, and preferably bark particles having a size greater than 1 mm.

Thus, in the above variant of the method according to the invention, step b) itself comprises the steps b1) and b2) specified.

"Bark chips" means bark fragments regardless of size or shape. In general, the bark chips have, in their greatest length, a size that can vary from a few centimeters to several tens of centimeters, for example from 5 cm to 30 cm. The thickness of the chips generally varies from a few millimeters to a few centimeters, for example from 1 mm to 5 cm, and often from 1 mm to 3 cm.

By "tannins" is meant condensed tannins, such as flavonoid polymers, and hydrolyzable tannins, such as esters of gallic acid or ellagic acid.

Preferentially, the term tannins refers to flavonoid polymers.

By "composition enriched in tannins" is meant according to the invention a composition obtained from a starting material and having a tannin content substantially greater than the tannin content of said starting material, in particular having a tannin content. which is at least double the tannin content of the starting material. For purposes of this disclosure, a tannin-enriched composition includes those compositions resulting from the process having a tannin content of at least 20% greater than the tannin content of the starting material, namely dried conifer bark chips. It is pointed out that, for purposes of the present description, two tannin content values are compared after taking into account the moisture content of the respective compared materials.

By "dihydroquercetin" is meant the compound (2R, 3R) -2- (3,4-dihydroxyphenyl) 3,5,7-trihydroxy-2-3-dihydrochromen-4-one, which is also commonly referred to as "taxifolin" , and whose CAS reference is CAS 480-18-2.

According to the invention, the term "composition enriched with dihydroquercetin" means a composition obtained from a starting material and having a dihydroquercetin content substantially greater than the dihydroquercetin content of said starting material, in particular having a dihydroquercetin content. which is at least double the dihydroquercetin content of the starting material. For the purpose of this description, a composition enriched in dihydroquercetin includes the compositions resulting from the process whose dihydroquercetin content is at least 20% higher than the dihydroquercetin content of the starting material, namely the dried chips of conifer bark. It is pointed out that, for purposes of this disclosure, two dihydroquercetin content values are compared after taking into account the moisture content of the respective compared materials.

For the purposes of the present description, the particle size is preferably determined by a sieving method, for which a succession of mesh sieves of increasingly reduced mesh size is used. By way of illustration, it is possible to use a series of sieves whose mesh size is respectively 10.0 mm, 6.0 mm, 4.0 mm, 3.0 mm, 2.0 mm and 1.0 mm. , 50 mm, 0.40 mm, 0.30 mm, 0.25 mm, 0.20 mm, 0.15 mm, and 0.10 mm.

Step a) Grinding

In step a), dried chips of conifer bark are milled to obtain a set of small bark particles, able to undergo a second grinding step.

Preferably, the ground material obtained at the end of step a) comprises a set of particles having grain size characteristics such that these particles have a particle size greater than 1 μηι.

Preferably, the ground material obtained at the end of step a) comprises particles having a size equal to or less than 10 mm, and very preferably a size equal to or less than 6 mm.

Advantageously, the particle size profile of the particles contained in the ground material may be of the unimodal or multi-modal type, with a particle size of up to 6 mm.

Bark particles from grinding step a) are collected for further processing.

As previously indicated, step a) is carried out with dried chips. The inventors have shown that the use of very wet chips, that is to say of chips whose moisture content is greater than 50%, in step a) caused clogging of the grinding device. The clogging of the grinder device is illustrated in particular by a clogging of the selection grid, which prevents the particles from leaving the mill and being collected for the rest of the process. In particular, the particles remain in the tank of the milling device in an undesired manner, which results, at the end of step a), in a mill which is difficult to collect and is therefore unfit for the continuation of the process.

Advantageously, prior to step a), the chips are subjected to a drying step at a temperature ranging from 30 ° C to 40 ° C for a period ranging from 6 hours to 36 hours, better from 10 hours to 30 hours, advantageously about 24 hours. The person skilled in the art knows how to adapt the temperature and the duration of the process according to the degree of humidity of the starting chips.

A drying temperature below 30 ° C is ineffective. A drying temperature above 40 ° C should be avoided in order not to damage the polyphenols contained in the bark, and in particular not to deteriorate the taxifolin or the tannins contained in the bark.

Advantageously, the dried chips used in step a) have a residual moisture equal to or less than 40%, preferably a residual moisture equal to or less than 15%.

For the purposes of this description, the residual moisture content is determined by the gravimetric method as follows: residual moisture is removed from the test product by heating. The residual moisture content of the tested product is calculated based on the weight loss of the product during the drying cycle. The residual moisture content is calculated according to the conventional technique of (i) performing a first weighing of a set of bark chips, (ii) drying said set of bark chips, for example by passing through an oven at 120 ° C, for example for 24 hours, for example at reduced pressure, (iii) performing a second weighing of said set of bark chips after drying, and (iv) calculating the initial water content (residual moisture) said set of bark chips) from the calculation of the amount of water evaporated.

For the implementation of the two processes described, step a) can be carried out using any type of grinding device making it possible to obtain, from bark chips, obtaining bark particles having the size of particle specified in this specification. In particular, those skilled in the art can use a grinding device chosen from (1) grinding in a knife milling device, (2) grinding in a ball mill device, and (3) grinding in an air jet mill device and, where appropriate, a combination of several of these devices, i.e., at least two such devices. Thus, the grinding step a) can be carried out according to a method chosen from (1) a grinding in a knife milling device, (2) a grinding in a ball mill device, and (3) a grinding in a device air mill, or a combination of at least two of these methods.

In some embodiments, step a) is performed using a knife milling device of a known type. Those skilled in the art can for example use a Retsch SM100 type knife mill marketed by Retsch.

Advantageously, the grinding step a) is carried out at a rotor speed of about 1500 revolutions per minute. It is specified that, when a knife milling is used in step a), grinding is preferably carried out continuously. Thus, the grind of particles is generated continuously in step a) before separation of the constitutive particles of the grind, in step b). With this type of grinder, the duration of the grinding step is not critical , since the maximum size of the particles contained in the ground material is determined by the mesh size of the selection gate at the outlet of the mill. By way of illustration, the mill is equipped with an outlet grid of 6 mm if the maximum desired size of the particles constituting the ground material obtained at the end of step a) is 6 mm.

In other embodiments, step a) is performed using a ball mill device, also known as a ball mill, of a known type. The skilled person may for example use a ball mill marketed by the company Faure (France). By way of illustration, a ball mill may be used in which balls of different diameters, or balls of diameters of 1, 2 cm, 1, 6 cm and 2.6 cm, have been introduced. For example, the balls of 1, 2 cm, 1, 6 cm and 2.6 cm in the proportions of 1/3, 1/3 and 1/3 can be introduced into the crusher bowl.

Alternatively, in these embodiments, step a) comprises two grinding steps, respectively the following steps:

a) a first step comprising grinding dried chips of conifer bark using a knife milling device to obtain a chip mill, and a2) a second step comprising grinding the chip mill obtained in step a1) using a ball milling device to obtain a crushed chip of coniferous bark particles.

With a ball mill, the grinding step a) is preferably carried out at 70% of the critical speed. It is specified that the critical speed is defined as the speed from which the balls are located on the walls of the tank due to the centrifugal force. It is understood that the critical speed depends in particular on the size and density of the balls used as well as the diameter of the tank of the grinding device.

By way of illustration, when step a) is carried out with a ball mill, step a) can be carried out for a duration that may vary from 10 minutes to 120 hours, for example by applying a rotational speed of the reaction vessel. about 120 rpm.

In yet other embodiments, step a) is performed using an air jet mill device of a known type. Those skilled in the art may for example use an air jet mill marketed by Hosokawa-Alpine. As an illustration, an air jet mill can be used at a pressure of 4.5 bars and a rotation speed of the selection turbine of about 2,000 rpm.

According to a first alternative, in these embodiments, step a) comprises two grinding steps, respectively the following steps:

a) a first step comprising grinding dried chips of conifer bark using a knife milling device to obtain a chip mill, and

a2) a second step comprising grinding the chip mill obtained in step a1) using an air jet milling device to obtain a crushed chip of coniferous bark particles.

According to a second alternative, in these embodiments, step a) comprises two grinding steps, respectively the following steps:

a) a first step comprising grinding dried chips of conifer bark using a knife milling device equipped with a 6mm selection grid, to obtain a first chip mill, a2) a second step comprising grinding the dried chip mill obtained in step a1) using a knife milling device equipped with a selection grid of 1 mm, in order to obtain a second chip mill,

a3) a third step comprising grinding the second chip mill obtained in step a2) using an air jet milling device to obtain a crushed chip of coniferous bark particles.

Step b) selection or steps bl) and bl) separation and selection. Step b), or step b1) in some embodiments of the method, comprises separating the bark particles obtained in step a) to obtain a plurality of fractions comprising particles of different sizes. .

In some embodiments of the method, the operating conditions of step b), or b1), are adapted to obtain a plurality of bark particle fractions, respectively at least:

(i) a fraction of bark particles having a particle size equal to or greater than 0.60 mm, for example a particle size equal to or greater than 1.00 mm, and

(ii) a fraction of bark particles having a particle size of less than 1.00 mm, for example a particle size of less than 0.60 mm.

(ii) a fraction of bark particles having a particle size equal to or less than 0.30 mm, for example a particle size equal to or less than 0.16 mm.

For purposes of the present disclosure, a particle size greater than 0.60 mm includes a particle size greater than 0.65 mm, 0.70 mm, 0.75 mm, 0.80 mm 0.90 mm, 0, 95 mm, 1.00 mm, 1.05 mm and 1.10 mm, 1.15 mm, 1.20 mm, 1.25 mm and 1.30 mm, For purposes of this disclosure, a particle size of less than 1.00 mm includes a particle size of less than 0.90 mm, 0.80 mm, 0.70 mm, and 0.65 mm.

For purposes of this disclosure, a particle size of 0.30 mm or less includes a particle size of less than 0.25 mm, 0.20 mm and 0.16 mm.

In some embodiments of step b) of separation, or of step b1) in certain variants of the process, other fractions of bark particles, additional to fractions (i) and (ii) are obtained. above, for example fractions whose particle size is intermediate between fractions (i) and (ii) above, as illustrated in the examples.

In some embodiments, step b), or bl), of separating the bark particles is carried out by sieving. As an illustration, the bark particles obtained in step a) are separated in step b) successively using:

a first sieve whose mesh size may vary from 0.60 mm to 1.30 mm, for example a sieve with a mesh size of 1.00 mm, for the purpose of obtaining the fraction (i) of particles bark above which is retained by the sieve, and

a second sieve whose mesh size may vary from 0.10 mm to 0.30 mm, for example a sieve whose mesh size is 0.16 mm, for the purpose of obtaining the fraction (ii) of particles bark above, which is not retained by the sieve.

In other embodiments, in step b) additional sieves are used whose mesh size is intermediate between the respective mesh sizes of the first and second sieves described above, as illustrated in the examples. .

Continuation of step b) or completion of selection step b2)

In step b), or in step b2) in certain process variants, the fraction or fractions of coniferous bark particles which are enriched in tannins or in dihydroquercetin, that is to say of which the tannin or dihydroquercetin content is substantially greater than the tannin or dihydroquercetin content of the conifer bark chips used as the starting material.

Preferably, in step b), or in step b2), the fraction comprising bark particles having a particle size equal to or greater than a particle size ranging from 0.6 mm to 1.00 is selected. mm, and preferably bark particles having a size greater than 1.00 mm. As shown in the examples, it is a fraction of coniferous particles that has a high dihydroquercetin content. This fraction of bark particles contains, on average, at least 50% by weight of all of the dihydroquercetin contained in the starting bark material.

Furthermore, as will be explained later in the description, the inventors have also shown that the fraction (ii) of coniferous bark particles having a particle size equal to or less than a particle size of 0.10 mm at 0.30 mm, for example a particle size equal to or smaller than 0.16 mm, was enriched with other polyphenols, and specifically with tannins.

In the same manner, in the process for obtaining a tannin-enriched composition, in step b) or b2) the fraction or fractions of coniferous bark particles which are enriched in tannins are selected, that is to say that is, the tannin content is substantially higher than the tannin content of the conifer bark chips used as the starting material.

Additional steps of the process

The fraction of tannin-enriched bark particles obtained in step b) or b2) of the process can then be used to obtain purified tannin compositions.

For example, a purified composition of tannins is obtained by using known methods of extraction and purification using as starting material the tannin-enriched fraction from step b) or b2) of the process described above. .

Thus, according to some embodiments, the method described above comprises an additional step c) of obtaining a purified composition of tannins by extraction of the tannins contained in the particles of the tannin-enriched fraction obtained in step b) or b2).

In particular, it is possible to use a solvent extraction method for the tannins, using an aqueous-alcoholic solution or else using a water / acetone mixture. For methods using a water / acetone solvent, the extraction step may be followed by a distillation step to remove the acetone and then a step of removing the pigments and lipids by solvent, for example using the hexane solvent.

By way of illustration, for obtaining a purified composition of tannins from the fraction of coniferous bark particles selected in step b) of the process, those skilled in the art can implement the extraction method which is described in PCT Application No. WO 91/01989.

Similarly, the fraction of dihydroquercetin enriched bark particles obtained in step b) of the process, or in step b2) in certain process variants can then be used to obtain purified compositions of dihydroquercetin .

For example, a purified composition of dihydroquercetin is obtained by using known methods of extraction and purification using as starting material the enriched dihydroquercetin fraction from step b), or b2), of the process described herein. -above.

Thus, according to certain embodiments, the method described above comprises an additional step c) of obtaining a purified composition of dihydroquercetin by extraction of the dihydroquercetin contained in the particles of the dihydroquercetin-enriched action obtained at the same time. step b), or b2).

For example, one skilled in the art can implement in step c) a method for obtaining dihydroquercetin such as the method described in European Patent Application No. EP 2 639 232 or the method described by Wang et al. (2011, Food Chemistry, Vol 126: 1178-1185).

In advantageous embodiments, step c) comprises the following steps:

cl) solvent extraction of the polyphenols contained in the fraction of coniferous bark particles enriched in dihydroquercetin selected in step c) of the process, to obtain an extract of polyphenols, and

c2) purifying dihydroquercetin from the polyphenol extract obtained in step d1).

Step c1) can be carried out according to any known method.

In some embodiments, step c1) may comprise an extraction of the polyphenols with the aid of a hydro-alcoholic solvent, for example with a solvent having an ethanol / water weight ratio of 25/75, for example a temperature of 40 ° C, as described for example in the European Patent Application No. EP 2,639,232.

According to other embodiments, step c1) comprises an extraction of the polyphenols with the aid of an aqueous solvent comprising an enzyme or a plurality enzymes such as cellulase, pectinase and / or beta-glucosidase, as described in the article by Wang et al. (2002, cited above).

According to still further embodiments, step c1) comprises extracting the polyphenols with water at elevated temperature, as described in US Patent 3,189,596. However, the latter method is not preferred because a high temperature is likely to deteriorate part of the dihydroquercetin contained in coniferous bark particles.

To carry out step c1), the person skilled in the art can of course use any other known method, such as the method described in PCT · Application No. WO 2013/172693 or the method described by Ma et al. (2012, Int J Sci Mol, Vol 13 (7): 8789-8804).

Step c2) can be performed by any method known to those skilled in the art. Step d2) is advantageously a purification step by chromatography; as described for example in European Patent Application No. EP 2 639 232 or in the article by Wang et al. (2002, cited above).

Any type of suitable chromatographic support may be used, such as reverse phase chromatography supports (eg HIQ sil type supports marketed by Chromatek, diol phase chromatographic supports marketed for example by YMC Europe or the type Cl 8 supports marketed by Kinetex). Cl 8 type supports are preferred, especially the supports of this type marketed by Kinetex

Other characteristics of the process

Depending on the types of trees, the anatomical and physiological characteristics of the bark tissues can vary considerably. It appears that the conifers have a bark of specific structure and constitution, which has allowed the development of the enrichment process of polyphenols, particularly tannins and dihydroquercetin, which is defined in the present description.

As shown in the examples, the constituent tissues of Douglas pine bark have a structure and a constitution such that:

the tannins are concentrated in a particular fabric, ground into very fine particles, this fraction being designated 'F4' in the examples; and - Dihydroquercetin is found in high content in a particular tissue located in the heart of the bark, tissue which has been designated "T2" in the examples.

Advantageously, the process according to the invention is carried out using bark chips of a conifer selected from cedar, cypress, pine, fir, juniper, agathis, larch, maritime pine (pinus pinaster), Douglas fir and redwood.

Douglas fir chips (Pseudotsuga) are preferably used for the process for obtaining a composition enriched with dihydroquercetin, and chips for maritime pine (pinus pinaster) for the process for obtaining a composition enriched in tannins.

The present invention also relates to a fraction of tannin-enriched bark particles that can be obtained by the process defined in the present description.

The invention also relates to a composition enriched in tannins that can be obtained by the process defined in the present description.

The present invention also relates to a fraction of bark particles enriched in dihydroquercetin obtainable by the process defined in the present description.

The invention also relates to a composition enriched in dihydroquercetin obtainable by the process defined in the present description.

The compositions enriched in tannins or in dihydroquercetin may be used in particular for the preparation of cosmetic compositions or pharmaceutical compositions.

It is known in the state of the art that dihydroquercetin has protective properties against free radicals (antioxidant effect), antibacterial and anti-fungal properties, anti-inflammatory properties, properties of inhibition of the deleterious effects caused. by an excess of certain cytokines such as interferon-gamma, effects of increase of the amount of lipids in the skin, or even cicatrizing effects.

It is also known that dihydroquercetin in particular has protective and strengthening properties of the capillary vascular network. Dihydroquercetin is particularly useful in the treatment of vitamin deficiency, cardiac ischemia, atherosclerosis, diabetes mellitus, diseases of the liver, prostate, kidney, gastrointestinal tract, urinary tract, cardiovascular diseases or some cancers.

The composition enriched with dihydroquercetin may be used for the preparation of cosmetic compositions.

The tannins are mainly used to tan hides and skins, and also to color some fabrics. Regarding their use in health and cosmetics, it is known that the tannins have anti-oxidant properties that make them the compounds of choice for the protection against the oxidative action of free radicals.

Process for obtaining compositions enriched with dihydroquercetin or tannins

As has been specified previously in the present description, step b), or b1), of the process for obtaining a composition based on coniferous bark enriched with dihydroquercetin makes it possible to simultaneously obtain at least a fraction of coniferous bark particles enriched in dihydroquercetin and at least a fraction of coniferous bark particles enriched in tannins.

The inventors have shown that the fraction (ii) of coniferous bark particles having a particle size equal to or less than a particle size ranging from 0.10 mm to 0.30 mm, for example an equal particle size or less than 0.16 mm, which fraction is obtained in step b) of the process, was enriched in other polyphenols, and specifically was enriched in tannins.

Thus, in some embodiments of the process, step b), or b2) comprises selecting a fraction of tannin-enriched bark particles, said fraction being bark particles having a smaller size. at 0.30 mm, and preferably bark particles having a size less than 0.16 mm.

According to an alternative of these particular embodiments of the process, said process further comprises a step d) of obtaining a purified composition of tannins by extracting the tannins contained in the particles of the tannin-enriched fraction obtained in step b), or b2). The invention also relates to a process for obtaining a dihydroquercetin enriched conifer bark composition and a tannin enriched coniferous bark composition comprising the steps of:

b2) selection:

on the one hand, a fraction of bark particles enriched in dihydroquercetin, said fraction being constituted by bark particles having a size greater than 0.6 mm, and preferably bark particles having a size greater than 1 mm, and

- On the other hand, a fraction of bark particles enriched in tannins, said fraction consisting of bark particles having a size less than 0.30 mm, and preferably bark particles having a size smaller than 0.16 mm.

Purified dihydroquercetin compositions can be obtained from the dihydroquercetin enriched particle fraction obtained in step 3) according to known methods which are referred to elsewhere in this specification.

Thus, in some embodiments of the above process, said method further comprises a step 4) of obtaining a purified tannin composition by extracting the tannins contained in the particles of the tannin-enriched fraction obtained from the step 3).

It is also possible to obtain purified tannin compositions from the fraction of tannin-enriched particles obtained in step 3), according to methods known to those skilled in the art, and in particular according to the same type of methods which comprise at least a step of extraction of the polyphenols by solvent and a purification step, preferably by chromatography. In particular, it is possible to use a method for solvent extraction of the tannins using an aqueous-alcoholic solution or else using a water / acetone mixture.

For methods using a water / acetone solvent, the extraction step may be followed by a distillation step to remove the acetone and then a step removal of pigments and lipids by solvent, for example using hexane solvent.

By way of illustration, in order to obtain a purified composition of tannins from the fraction of coniferous bark particles selected in step 3) of the process, the person skilled in the art can implement the process of extraction which is described in PCX Application No. WO 91/01989.

The dry fractionation method which is defined in the present description has many advantages, especially for its implementation in industry. The process for obtaining compositions enriched in dihydroquercetin or tannins can be effectively inserted into industrial biomass biorefinery processes and in particular forest, agricultural and industrial waste, and be compatible with an industrial economy aiming at sustainable development. Indeed, the process according to the invention comprises enrichment steps in polyphenols of interest, respectively dihydroquercetin and tannins, which is carried out by the dry route, and which therefore does not require water consumption nor, therefore, , of necessity the drying of effluents.

The present invention is further illustrated, but not limited to, by the following examples.

EXAMPLES

Example 1 Process for obtaining a composition enriched in dihydroquercetin and a composition enriched in tannins

A. Identification of the constituent tissues of the bark before a high content of dihydroquercetin or tannins

On a piece of Douglas-fir bark, a first visual examination distinguishes three different tissues, respectively a light brown Tl tissue, a light beige T2 tissue and a beige T3 tissue darker than the T2 tissue .

Manual dissection of the bark was performed and the flavonoid composition of each tissue was determined by UPLC-MS analysis.

The UPLC-MS analysis results shown in FIG. 1 show that taxifolin is exclusively localized in the T2 tissue, whereas the tannins are located in the T1 tissue. These results justify the interest of designing a process for selectively obtaining (i) at least one fraction from bark enriched in taxifolin and (ii) at least one fraction from bark enriched in tannins. B. Description of the process

Douglas Fir bark chips from a Douglas Fir harvest were used in April 2013.

The bark chips were oven dried for 24 hours at a temperature of 30 ° C to 40 ° C (this drying step is necessary to prevent clogging at the time of grinding) and then crushed and separated by sieving.

The grinding was carried out in a Retsch SM 100 knife mill on a 6 mm grid. The mechanical stresses generated within a knife mill are mainly cutting and shearing.

The sample is conveyed by a hopper to the grinding chamber in which a rotor (intermediate rotation speed: 1500 rpm) equipped with knives ensures the movement of the sample and its grinding between his own knives and counter-knives located in the chamber casing.

When the particles reach a size less than or equal to that of the mesh of the selection grid, they leave the grinding chamber and are discharged to the collecting container. The fraction collected was called F0. The residence time in the grinding chamber is relatively short, of the order of a few seconds.

The sieving operation consists in dividing or separating the ground particles by passing them through a succession of sieves whose meshes of the grids are becoming finer. On each sieve the particles whose size is greater than the mesh are retained. Each fraction recovered corresponds to the diameter of the sieve which retained it. Sieving was carried out on a ROTEX station for 20 minutes. The sieving was carried out in a sieving column provided with several cylindrical trays of mesh 1 mm, 0.56 mm and 0.16 mm respectively and a cover preventing the loss of particles. The column is agitated by a vibration device whose speed can be controlled. Four fractions were obtained after this sieving, designated fractions F1 to F4. C. Quantification method for taxifolin present in the different fractions by UPLC-MS

• Depolymerization of the tannins contained in the fractions F0-F4

Suspension A: Fractions F0 to F4 (200 mg) were suspended in 2 ml of methanol.

Solution B: The depolymerization solution is prepared by adding 400 μL of thioglycolic acid in 4.96 mL of methanol containing 0.2 mol / L hydrochloric acid.

In test tubes, 2 mL of suspension A and 2 mL of solution B are mixed. The tube is sealed and the reaction mixture is heated at 90 ° C for 6 min.

• UPLC-ESI / MS analyzes

The liquid chromatography system is an UPLC Acquity (Waters, Milford, MA) equipped with a diode array detector. The column (HSS 100x2 T3, 1 mm, 1.8 mm) is a Nucleosil 120-3 endcapped C18 (Macherey-Nagel, Sweden). The flow rate is 0.55 mL.min -1, and the gradient conditions are as follows: solvent A (H ₂ O / HCOOH, 99/1, v / v); solvent B (CH ₃ CN / H ₂ O / HCOOH, 80/19/1, v / v / v); initial conditions 0.1% of B; 0-5 min, 40% linear B; 5-7min, 99% linear B; 7-8min, 99% B and 8-9min, 0.1% linear B.

The MS analyzes were performed on an AmaZon X ESI Trap mass spectrometer (Bruker Daltonics, Bremen, Germany). In the source, the nebulizer pressure was 44 psi, the dry gas temperature was set at 200 ° C with a flow rate of 12 L.min-1 and the capillary voltage was set at 4.5kV. Mass spectra were acquired over a mass range of 70-2000 Da in the positive ionization mode. The acquisition speed of the mass spectrum was set at 8.1 m / z.min-1.

D. Tannin quantification method present in the different fractions The analysis and quantification of the tannins are carried out after a depolymerization step.

The depolymerization reaction of tannins is a routine analytical method. The principle of this method is based on the acid-catalyzed rupture of inter-monomer bonds. The breakdown of these bonds is heterolytic so that the extension units are released as carbocations, trapped extemporaneously by the nucleophile (in this work the methyl ester of thioglycolic acid) present in large excess in the medium. Therefore, the distinction between extension units (which are detected as thioethers derivatives) and terminal units (which are released as such, without modification) allows to estimate the average degree of polymerization of the polymers present in the fraction. This depolymerization reaction can be done on tannins, previously extracted from the plant or a processed product from the plant as it can be done on the plant material directly, in this case the bark.

Of the five fractions F0, F1, F2, F3 and F4 studied, the depolymerization reaction was carried out directly on the powder. It was performed in sealed tubes, with acidified methanol (0.2N with HCl) and heated to 90 ° C in the presence of thioglycolic acid (which is converted to the methyl ester in the preparation of the reagent solution) as nucleophilic agent. E. Results of analysis of bark particle fractions obtained by the process

At the end of the dry fractionation operations, four fractions, designated F1 to F4, were collected:

- Fraction Fl: particles retained on the sieve of 1 mm

- Fraction F2: particles retained on the sieve of 0.56 mm

- Fraction F3: particles retained on the sieve of 0.16 mm

- Fraction F4: particles passing through the 3 screens

The fraction designated F0 is the fraction recovered after grinding and before sieving.

The fractions harvested were weighed and the mass percentage of each fraction is shown in FIG.

All analyzes were performed in triplicate to estimate the uncertainty interval of the measurement. The results of analysis and quantification by UPLC-MS are summarized in Table 1 below. Table 1: Tannin and taxifoline content in fractions FO to F4.

The results in Table 1 show that Douglas fir bark contains 2.6% taxifolin. In addition, the implementation of the method according to the invention has made it possible to isolate most (about 50%) of the total amount of taxifolin contained in the bark, which is contained in the fraction F1.

The results in Table 1 also show that the condensed tannins are located in the F4 fraction. Thus, the process according to the invention can also be the means for extracting condensed tannins that can be used, in particular, as precursors for epoxy resins based on a natural material.

All these results show that the process according to the invention makes it possible to simultaneously obtain (i) a fraction of particles of coniferous bark, specifically Douglas-pine, enriched in dihydroquercetin and (ii) a fraction of particles of conifer bark, specifically Douglas pine, enriched with tannins.

The observations made with the naked eye on the different fractions, have shown that the different fractions (Fl to F4) consist of particles of barks of different colors and constitutions suggesting a different histological origin. The fraction F1 consists in particular of three particle populations:

- Fia, fibrous, light-colored,

- Solid flb, brown color,

- Fi e solid, lighter color.

UPLC-MS analysis, after depolymerization, of these three sub-fractions reveals that the Fie subfraction is the richest in taxifolin (Table 2). Table 2: Tannin content and taxifolin in fractions Fia to Fi e.

Example 2: Reproducibility of the process for obtaining a composition enriched in dihydroquercetin and a composition enriched in tannins.

The method described in Example 1 was reproduced on Douglas pine bark.

The pine bark was milled on a knife mill and then sieved through the series of sieves previously selected (sieve 1 mm, 0.56 mm, 0.16 mm). The results obtained are shown in Table 3.

Table 3: Comparison of the yields and tannin and taxifolin content obtained during the tests carried out in Example 1 and in the present example 2.

The results of Table 3 show quite significant differences in yield on the two series of tests, this difference being explained by differences in certain operating conditions that are distinct from the main characteristics of the process of the invention, in particular the conditions of supply of the grinder device. This technical problem has been solved by setting up an automatic regulated system for feeding the grinding device.

Example 3: Implementation of the process with a grinding step carried out with a ball mill device

The samples from the knife milling on the 6 mm grid, F0 fraction, were subjected to a second grinding step in a Faure-type ball mill, in a jar weighing 5 L. 1 kg of dried chips of pine bark was introduced with 2 kg of balls (1/3 of balls of diameter 1,2 cm, 1/3 of balls of diameter 1, 6 cm and 1/3 of balls of diameter 2,6 cm) with a rotation speed of 120 rpm.

Samples were taken after 75 min and 12 h of grinding and were sieved on the 1 mm, 0.56 mm and 0.16 mm grids.

The contents of taxifolin and tannins were determined in the fraction of particles larger than 1 mm and in the fraction of particles smaller than 0.16 mm, showing the highest levels respectively in taxifolin and tannins (Table 4). .

Table 4: Yield and content of taxifolin obtained during purification by ball milling and sieving.

The results of these tests show a very high concentration of taxifolin in the fraction of particles larger than 1 mm, which allowed to isolate more than 80% of taxifolin total phenols in the case of 12 h grinding. This result shows that it is possible, by an easy to implement and inexpensive method, to obtain end products of very high purity in taxifolin or tannins.

Example 4: Process for obtaining a composition enriched in tannins.

The method described in Example 1 was reproduced on commercial maritime pine bark.

The grinding step led to the FO-M fraction, the sieving of which gave rise to 4 fractions: Fl-M, F 2 -M, F 3 -M and F 4 -M.

As indicated in FIG. 1, the fractions F1 to F4 are characterized by the following particle sizes:

- Fl: particle size greater than 1 mm

- F2: particle size less than 1 mm and greater than 0.56 mm

- F3: particle size less than 0.56 mm and greater than 0.16 mm

- F4: particle size less than 0.16 mm.

The tannin and taxifolin contents of the fractions mentioned above are shown in Table 5.

Table 5: Phenolic composition of fractions generated after grinding and sieving of maritime pine bark.

yield

tannins +

of each tannin taxifoline%

%%

Taxifolin fraction mg / g

fractions mg / g tannin +

bark taxifoline tannins

mg / g of bark taxifolin

%

FO-M 100% 38.70669 38.46849 0.23819 3.87 3.85 0.02

Fl-M 40.4% 30.24864 29.96348 0.28515 3.02 3.00 0.02

F2-M 27.1% 28.50223 28.24776 0.25447 2.85 2.82 0.03

F3-M 20.8% 41, 04847 40.72690 0.32156 4.10 4.07 0.03

F4-M 1 1, 7% 80.91985 80.57130 0.34854 8.09 8.05 0.04 Maritime pine is less rich in phenolic compounds than Douglas-fir. In addition, unlike Douglas-fir, the amount of taxifolin in the maritime pine is smaller.

On the other hand, the fraction F4-M which contains the finest particles (<0.16 μηι) is substantially enriched in tannins (yield = 11, 7%).

Claims

A process for obtaining a tannin enriched coniferous bark composition comprising the steps of:

2. Method according to claim 1, step b) comprising the following steps:

A process for obtaining a coniferous bark composition enriched in dihydroquercetin, comprising the steps of:

4. Method according to claim 3, wherein step b) comprises the following steps:

5. Method according to one of claims 3 and 4, step b), or b2), further comprising the selection of a fraction of tannin-enriched bark particles, said fraction being composed of bark particles. having a size less than 0.30 mm, and preferably bark particles having a size less than 0.16 mm.

6. Method according to one of claims 1 to 5, the chips, used in step a) having previously been subjected to a drying step in order to obtain dried chips having a residual moisture equal to or less than 40%, and preferably a residual moisture equal to or less than 15%.

7. Method according to one of claims 1 to 6, the grinding step a) being carried out according to a method selected from (1) a grinding in a knife mill device, (2) a grinding in a ball mill device and (3) grinding in an air jet mill device, or a combination of at least two of these methods.

8. Method according to one of claims 1 to 7, wherein step b), or bl) _} separation of the particles into fractions being carried out by sieving.

9. Method according to one of claims 1, 2, 6, 7 or 8, further comprising a step c) for obtaining a purified composition of tannins by extracting the tannins contained in the particles of the tannin-enriched fraction. obtained in step b) or b2).

10. Method according to one of claims 3 to 8, further comprising a step c) for obtaining a purified composition of dihydroquercetin by extraction of the dihydroquercetin contained in the particles of the dihydroquercetin enriched fraction obtained in step b), or b2).

1. Method according to one of claims 5 to 8, further comprising a step d) of obtaining a purified tannin composition by extracting the tannins contained in the particles of the tannin-enriched fraction obtained in step b), or b2).

12. Method according to one of claims 1 to 11, said conifer being selected from cedar, cypress, pine, fir, juniper, agathis, larch, maritime pine, Douglas pine and sequoia. .

13. Method according to one of claims 1 or 2, said conifer being a maritime pine.

14. Method according to one of claims 3 or 4, said conifer being a pine

Douglas.

15. Fraction of tannin-enriched bark particles obtainable by the method according to one of claims 1, 2, 6, 7, 8, 9, 12 or 13.

16. A tannin-enriched composition obtainable by the process according to one of claims 1, 2, 6, 7, 8, 9, 11, 12 or 13.

17. A fraction of bark particles enriched in dihydroquercetin obtainable by the method according to one of claims 3 to 8 or 12 or 14.

18. A composition enriched in dihydroquercetin obtainable by the method according to one of claims 3 to 8 or 10, 12 or 14.