Preparation of a dry biomass extract rich in polyphenols

Abstract

The present invention concerns a method for preparing a dry plant biomass extract, in particular from parts of grape canes, that are rich in polyphenols, the extract obtained and the use of same for antifungal applications, in particular for the prevention and treatment of fungal infections on fruits and vegetables after harvesting, but also for applications linked to the antibacterial and antioxidant properties of same.

Description

[0001] PREPARATION OF A DRY BIOMASS EXTRACT RICH IN POLYPHENOLS

[0002] FIELD OF INVENTION

[0003] The present invention relates to a process for preparing an extract of dry plant biomass, in particular parts of grapevine, rich in polyphenols, the extract obtained and its use for antifungal applications, in particular for the prevention and treatment of fungal infections on fruits and vegetables after harvest, but also for applications related to its antibacterial and antioxidant properties.

[0004] STATE OF THE ART

[0005] Plant biomass extracts rich in polyphenols are well known to those skilled in the art. Numerous studies have focused on the extraction of biomass to obtain a polyphenol-rich extract, all of which present several drawbacks regarding the economic viability of the processes, such as low yields or very long extraction times, or limitations on their post-extraction use, particularly the use of toxic organic solvents (Goupil et al. 2012, Alexa et al. 2012, Sanchez et al. 2008, Pezet et al. 2004).

[0006] Various polyphenol extraction techniques and their uses are described in particular in patents and patent applications US 2012 / 0021080, US 5,989,557, US 2012 / 0142105, JP 2016 102192, CN 205 759 861, CN 103 875 842, or in articles by Osorio et al (2010), Luque-Rodriguez et al. (2006) or Favaron & Lucchetta (2009).

[0007] Studies have shown that it is possible to improve biomass extraction processes through microwave, ultrasonic, or high-temperature treatments (Quan et al. 2006, CN 104 177 463, CN 104 435 135, CN 102 757 512, CN 104 256 432, CN 104 256 641, CN 103 783 506, CN 102 757 509, CN 101 816 349), for example, in the production of biodiesel (CN 19 35 947). Some advocate high-temperature treatment under high pressure (Casazza et al. 2010).

[0008] However, such high-temperature treatments can alter the properties of the extracts obtained and will not be suitable for the implementation of an industrial process on large volumes of raw material and solvents.

[0009] There is a need for an efficient process for extracting biomass to prepare a polyphenol-rich extract that is efficient, more economical and respectful of the properties of the biomass with regard to its polyphenols.

[0010] DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a process for preparing a dry plant biomass extract, in particular a Vitis sp. extract, rich in polyphenols, comprising (a) a step of extracting the dry biomass by contacting it with an aqueous solvent and (b) a step of recovering the polyphenol-enriched aqueous phase, characterized in that in the extraction step (a), the plant biomass / aqueous solvent mixture is treated simultaneously or sequentially by the combination

[0012] (i) electromagnetic waves with frequencies ranging from 915 MHz to 28 GHz, and

[0013] (ii) stirring of the mixture, and / or

[0014] (iii) a pressure of 50 to 950 mbars (5,000 to 95,000 Pa).

[0015] The invention also relates to the extract that can be obtained by this process and its use for antifungal applications, in particular for the prevention and treatment of fungal infections on fruits and vegetables after harvest.

[0016] DETAILED DESCRIPTION OF THE INVENTION

[0017] The invention relates to the preparation of a polyphenol-rich extract by extraction from a dry biomass with an aqueous solvent.

[0018] According to the invention, an aqueous solvent is understood to mean water or an aliphatic alcohol / water mixture, in particular ethanol / water. In this case, the alcohol / water mixture, in particular ethanol / water, comprises 10 to 70% by volume of ethanol. According to a preferred embodiment of the invention, the aqueous solvent is an ethanol / water mixture comprising 15 to 40% ethanol.

[0019] The plant biomass according to the invention is biomass known to contain polyphenols, in particular trans-resveratrol, trans-e-viniferin, trans-piceatannol, and trans-vitisin. Those skilled in the art are familiar with this biomass derived from plants known to contain these polyphenols, used alone or in mixtures, generally dicotyledonous plants such as grapevines, tea plants, or Japanese knotweed, and more specifically, grapevines. The biomass according to the invention may consist of whole plants or parts of plants, more particularly aerial parts such as fruits, flowers, leaves, stems, branches, or trunk fragments (vines), and mixtures thereof. Where appropriate, the biomass may also include or consist of plant roots.

[0020] The biomass is dry, that is, obtained by drying the aforementioned plants or plant parts. Drying can be carried out by any method known to those skilled in the art. Advantageously, drying is achieved by leaving the plants or their parts to dry in the open air. According to a preferred embodiment of the invention, the plants or their separated parts are left to dry in the open air for a period ranging from one month to four years, preferably one to two years.

[0021] Preferably, the dry biomass consists of dry parts of plants of the genus Vitis, in particular Vitis vinifera, Vitis labrusca, Vitis riparia, Vitis rupestris, Vitis berlandieri, Vitis amurensis, Vitis coignetiae, Vitis vulpina, Vitis acerifolia, Vitis aestivalis, Vitis rotundifolia, and more particularly Vitis vinifera. According to an advantageous embodiment of the invention, the dry biomass comprises or is made up of vine shoots.

[0022] Advantageously, this dried biomass consists of plant fragments, particularly plant pulp or plant parts. Preferably, the fragments have a particle size of less than 1 cm, more preferably less than or equal to 5 mm, and more preferably ranging from 1 to 5 mm. This particle size of the dry matter fragments / pulps is measured according to standard methods well known to those skilled in the art.

[0023] The fragmentation of the dry plants will be carried out according to the usual methods known to those skilled in the art. According to a particular embodiment of the invention, these fragments are obtained first by shredding the dry material to obtain fragments of 1 to 20 cm which are then ground to obtain fragments preferably of 1 to 5 mm, which correspond to a preferred particle size for extraction.

[0024] A person skilled in the art will be able to determine the quantities of extraction solvent to use in relation to the quantity of biomass. Advantageously, the ratio by mass of dry plant biomass to aqueous solvent ranges from 1 / 5 to 1 / 30, preferably from 1 / 10 to 1 / 20.

[0025] The process according to the invention is characterized by the combination of at least two constraints applied simultaneously or successively to the extraction mixture (biomass / solvent):

[0026] (i) electromagnetic waves with frequencies ranging from 915 MHz to 28 GHz, and

[0027] (ii) of brewing, and / or

[0028] (iii) a pressure of 50 to 950 mbars.

[0029] Simultaneous or sequential mixing, according to the invention, means that microwave treatment and at least mixing and / or pressure of 950 mbar or less are carried out at the same time, or one after the other, in particular according to sequences (i) + (ii), or (i) + (iii), or (i) + (ii) + (iii), or [(i), (ii)] + (iii), or [(ii), (iii)] + (i), in any order chosen. In the case of sequential treatment, a person skilled in the art may choose to repeat each sequence several times, or even to combine different sequences according to a predetermined program, possibly combined with one or more simultaneous treatment sequences.

[0030] According to a preferred embodiment of the invention, the three treatments are carried out simultaneously [(i), (ii), (iii)].

[0031] Step a) may also include ultrasound treatment (iv). This treatment may be applied sequentially or simultaneously with treatments (i), (ii) and / or (iii) defined previously.

[0032] Electromagnetic waves with frequencies ranging from 915 MHz to 28 GHz correspond to microwave waves. A person skilled in the art will be able to choose the most suitable frequency for implementing the process, particularly depending on the biomass, to optimize the extraction process. Advantageously, the frequency of electromagnetic waves ranges from 915 MHz to 2.45 GHz. The frequency of electromagnetic waves will be advantageously chosen based on known industrial devices for generating electromagnetic waves on an industrial scale, in particular wave generators with frequencies below 1500 MHz, and more advantageously around 915 MHz.

[0033] A skilled professional will also know how to choose the most suitable wave power for the biomass and the extracts obtained. The power of the electromagnetic waves advantageously ranges from 300 W to 100 kW, and more advantageously from 1 to 75 kW.

[0034] This power will be chosen in particular according to the volume to be treated and the time required for extraction. According to a preferred embodiment of the invention, the power of the electromagnetic waves is chosen according to the following ratio: for 1 kg of material to be extracted, the power of the electromagnetic waves is 1 to 10 kW, ideally 2 to 6 kW.

[0035] Advantageously, the extraction time will be at least 20 min, or even at least 30 min and preferably less than 125 min, it being understood that too short a time may be associated with excessively high power conditions likely to alter the biomass, while too long a time may lead to degradation of the extracted products, and therefore in both cases a risk of loss of polyphenols.

[0036] The process according to the invention is suitable for use with various volumes of biomass / solvent mixtures, particularly those of at least 1 L, preferably at least 5 L. The process according to the invention is especially suited to the industrial extraction of dried biomass. Advantageously, the process can be used with biomass / solvent mixture volumes of at least 30 L, potentially exceeding 50 L, or even exceeding 100 L. Depending on the extraction reactors available to those skilled in the art, the process according to the invention can be used with volumes exceeding 200 L.

[0037] The biomass / solvent mixture is subjected to mixing (ii), said mixing (ii) being preferably carried out simultaneously with the electromagnetic wave treatment (i). This mixing is important to allow the electromagnetic waves to reach the entire mixture; otherwise, only the surface of the mixture would be subjected to the action of these waves.

[0038] A person skilled in the art is familiar with the appropriate methods for implementing mixing based on the volume of the mixture to be treated. These methods include rotating the mixture itself, generally using blades rotating within the mixture, or rotating the reactor containing the mixture. A person skilled in the art may also consider other mixing methods, such as agitating the mixture with air or inert gas. Preferably, mixing is achieved by rotating the mixture at a speed ranging from 3 to 20 revolutions per minute, most preferably using blades rotating within the mixture.

[0039] A person skilled in the art will know how to choose the most suitable means of rotation for implementation in an environment subjected to treatment by electromagnetic waves, which may generate electric arcs.

[0040] The process also includes depressurizing (iii) the mixture, preferably during treatment with electromagnetic waves (i) and mixing (ii).

[0041] A person skilled in the art is well-versed in the methods required to create a negative pressure (or partial vacuum) in a container holding a mixture to be treated. These industrial methods allow for pressures ranging from 50 to 950 mbar (5,000 to 95,000 Pa). They will be able to select an appropriate pressure based on the volumes to be treated. In particular, for industrial volumes such as those described above, it will be advantageous to treat the mixture at a pressure of 50 to 950 mbar (5,000 to 95,000 Pa), preferably 50 to 500 mbar (5,000 to 50,000 Pa).

[0042] Since the process also includes ultrasonic treatment, the operator will be able to select both the frequency and the power of the ultrasound. Advantageously, the ultrasound frequency ranges from 25 kHz to 1 MHz. According to a preferred embodiment of the invention, the ultrasound power ranges from 200 to 4000 W.

[0043] The invention also relates to a process as defined above and in the examples, which includes an additional step (c) of concentrating polyphenols by partial or total evaporation of the aqueous solvent.

[0044] According to a preferred embodiment of the invention, this concentration (c) is achieved by lyophilization of the recovered aqueous phase.

[0045] According to a particular embodiment of the invention, the dried biomass is subjected, prior to step a) of extraction, to leaching with a suitable solvent to remove the sugars. Those skilled in the art will be able to determine the conditions for this leaching based on the dried biomass and its sugar content.

[0046] The removal of sugars, depending on the biomass being processed, will be important for obtaining a polyphenol-rich extract with antifungal properties. Indeed, it has been observed that the presence of sugars can have an antagonistic effect on the antifungal activity of polyphenols by promoting fungal growth. The invention also relates to a polyphenol-rich biomass extract obtainable by the process according to the invention. These extracts advantageously contain four molecules of interest, which are polyphenols of the stilbene family. These four molecules are trans-piceatannol, trans-resveratrol, trans-e-viniferin, and trans-vitisin. Preferably, the extract contains at least twice as much trans-e-viniferin (or even at least 2.5 times more) and at least three times as much trans-vitisin (or even at least six times more) as a conventional ethanolic extract.

[0047] The invention also relates to a polyphenol-rich biomass extract obtainable by the process according to the invention from biomass consisting of dry parts of plants of the genus Vitis, in particular Vitis vinifera, Vitis labrusca, Vitis riparia, Vitis rupestris, Vitis berlandieri, Vitis amurensis, Vitis coignetiae, Vitis vulpina, Vitis acerifolia, Vitis aestivalis, Vitis rotundifolia, and more particularly Vitis vinifera. According to a preferred embodiment of the invention, the polyphenol-rich extract is an extract of grapevine shoots, more particularly of Vitis vinifera shoots.

[0048] The extracts according to the invention have fungicidal, bactericidal and antioxidant properties, as shown by the examples for an extract of Vitis vinifera shoots.

[0049] The extracts according to the invention, in particular the vine shoot extracts, are active as fungicides to control (prevent) the development of harmful fungi in food and agriculture, such as contaminants of canned fruit (Byssochlamys nivea), or diseases of fruit trees, vegetables, and plants, such as apple canker (Nectria galligena), brown rot of fruit trees (Monilinia fructicola, Monilinia fructigena, and Monillinia laxa), carrot blight (Alternaria daucil), potato silver scab (Helminthosporium solani), maize fusarium wilt (Gibberella zeae), wheat fusarium wilt (Fusarium culmorum), wheat septoria leaf blotch (Mycosphaerella graminicola), or various rots (including Penicillium digitatum, Penicillium italicum, and Phytophthora). syringae or Rhizopus stolonifer).

[0050] The invention also relates to a fungicidal treatment method for plants to prevent or control the development of pathogenic fungi on said plants, said method comprising the application to said plants of an effective quantity of extract according to the invention, in particular of vine shoot extract as defined above and in the examples.

[0051] The plants that can be treated with the extracts according to the invention are advantageously plants cultivated for human consumption, such as vegetable crops, potato crops, field crops like cereal crops, particularly barley, wheat and maize, soybean crops or oilseed crops such as rapeseed, sunflower, flax, hemp, or cotton. The treatment can also be applied to fruit trees, particularly apple, pear, apricot, and peach trees, or to grapevines.

[0052] The product is applied to plants as needed, either preventively, when climatic conditions are favorable to fungal growth, or curatively after diseases have appeared. Application is generally carried out using standard spraying methods. Those skilled in the art will be able to determine when and how to treat plants with an extract according to the invention, used alone or in a mixture with other products known for their fungicidal properties, such as copper sulfate, Bordeaux mixture, or other plant protection products from the agrochemical industry. Advantageously, the treatment is carried out without using plant protection products from the agrochemical industry, for organic or biodynamic agriculture.

[0053] The invention also relates to a method for preventing and / or treating the deterioration of fruits and vegetables after harvest, in particular the development of fungal rot, said method comprising applying to said fruits and vegetables an appropriate amount of extract that can be obtained by the method according to the invention as defined above and in the examples.

[0054] Due to these antioxidant properties, the extracts according to the invention, in particular the extracts of vine shoots, can also be used for the preservation of food compositions or cosmetic compositions.

[0055] By its ability to delay fruit oxidation after harvest, the extract according to the invention, particularly the vine extract, can be used to prevent and / or treat oxidative stress in plants by application to these plants or to parts of plants, especially on fruits sensitive to oxidation such as bananas or exotic or tropical fruits such as mangoes, passion fruit, etc., which are susceptible to oxidative stress when stored at low temperatures, lower than those encountered in their natural environment. The invention also relates to the use of the extract according to the invention, particularly the vine shoot extract, or a composition containing it, for the prevention and / or treatment of oxidative stress in plants.

[0056] The extract according to the invention, in particular the vine shoot extract, can also be used for its antioxidant properties for the prevention and treatment of oxidative stress in humans and animals.

[0057] They also possess antibacterial activity, particularly against pathogenic Gram-positive bacteria, while preserving commensal bacteria in humans. They are especially active against bacteria of the genera Staphylococcus, Listeria, Streptococcus, and Propionibacterium, particularly Propionibacterium acnes, the pathogen responsible for acne. The extracts according to the invention, especially the vine shoot extracts, have broad-spectrum antimicrobial activity, with a more pronounced efficacy against skin pathogens.

[0058] The invention therefore relates to an extract according to the invention, particularly a vine shoot extract, for its use in therapy, in particular for the treatment and prophylaxis of bacterial infections, more particularly for the treatment and prophylaxis of cutaneous bacterial infections, even more particularly for the treatment and prophylaxis of acne.

[0059] The invention also relates to a composition comprising an extract that can be obtained by the process according to the invention as defined above and in the examples and a suitable vehicle for its use.

[0060] This could be an antifungal composition intended for application to plants before or after harvest, or a pharmaceutical composition. Such compositions are known, and a person skilled in the art will be able to determine the appropriate vehicle for this use.

[0061] The present invention relates in particular to a plant protection product composition comprising at least the extract as described above and at least one compatible formulation agent. This plant protection product composition may be in dry form, for example as a powder or granules, or in liquid form, for example as a suspension, a concentrated or non-concentrated dispersion, a gel, an emulsion, etc.

[0062] The formulation agent is a natural agent or one derived from synthetic chemistry, and is classically used in phytopharmaceutical compositions.

[0063] The formulation agent can be a dispersant, a stabilizer, a surfactant, a preservative, a wetting agent, an adhesion agent, a buffer, a pH regulator, a photoprotector... They can be used alone or in mixtures.

[0064] The extract that can be obtained by the process according to the invention, as well as the compositions containing it, are particularly suitable for use in the prevention and treatment of fungal infections on fruits and vegetables after harvest.

[0065] The process according to the invention comprises the implementation of several combined techniques on the same extraction medium. Each technique (electromagnetic waves, ultrasound, vacuum) and the means for its implementation are well known (WO

[0066] 2012 / 045923, EP 2 530 059, FR 2 976 062). A person skilled in the art will be able to adapt existing hydro-alcoholic extraction devices for dried biomass to apply these associated treatments.

[0067] DESCRIPTION OF THE FIGURES

[0068] Figure 1 compares the relative amounts of trans-piceatannol, trans-resveratrol, trans-e-viniferin, and trans-vitisin in an extract obtained by the process according to the invention and in an extract obtained by a conventional process. The values ​​shown represent the relative concentrations (in arbitrary units) of each of the four molecules, calculated from the areas under the curve of the HPLC peaks.

[0069] Figure 2 compares the antifungal activity of an extract obtained by the process according to the invention (round symbols) and an extract obtained by a conventional process (square symbols). The values ​​shown are the averages, under three identical conditions, of the efficacy (0% = normal fungal growth; 100% = no fungal growth) 4 days post-inoculation, as a function of the extract concentration.

[0070] EXAMPLES

[0071] Example 1, preparation of an eco-extract from Vitis vinifera vine shoots:

[0072] The starting plant material is Vitis vinifera vine shoots (lignified branches). The shoots are dried (either in the open air or in a drying oven). Once dry, the shoots are first shredded into fragments of 2 to 10 cm and then finely ground to a particle size of 1 to 5 mm. The resulting Vitis vinifera vine shoot powder is extracted in a 30% aqueous or ethanolic solution. The extraction time is between 30 minutes and 1 hour 30 minutes, preferably 45 to 60 minutes. The extraction techniques used are simultaneous microwave, ultrasound, vacuum, and brazing. The resulting extract is vacuum-filtered at 20 microns. The extract is then evaporated under vacuum and subsequently dried by spray drying or freeze-drying. The resulting dry extract is then stored at room temperature, protected from light.

[0073] Example 2, chemical characterization of the Vitis vinifera vine shoot extract prepared according to example 1:

[0074] 5 mg of the freeze-dried, dried Vitis vinifera vine shoot eco-extract obtained according to Example 1 were dissolved in 1 ml of 50% ethanol. The solution was solubilized and then centrifuged for 10 min at 12,000 rpm before being injected into an HPLC-MS (high-performance liquid chromatography-mass spectrometry) system under the following conditions. The injected extract volume was 25 μL. The migration solvents were ultrapure water (0.1% formic acid) and acetonitrile (0.1% formic acid). Separation was carried out in 55 min at 1 ml / min according to the following solvent gradient:

[0075]

[0076] The column used contains a stationary phase grafted with C18 functional groups. UV detection is performed between 200 and 800 nm. Mass detection is performed in ESI, in negative mode. Four major compounds are obtained, and their retention times, absorbances, and molecular masses are shown in the table below.

[0077]

[0078] The comparison of the content of these 4 compounds with a conventional ethanolic extract is shown in Figure 1.

[0079] Example 3, antifungal action against Botrytis cinerea:

[0080] Botrytis cinerea spores are deposited at the bottom of wells in 96 transparent plates, into which agar nutrient medium has been previously poured.

[0081] The freeze-dried dry Vitis vinifera vine shoot eco-extract obtained according to example 1, dissolved at different concentrations (0g / l, 2.5g / l, 5g / l, 10g / l, 20g / l and 30g / l) in 8% ethanol, is then deposited in the wells.

[0082] After different incubation times at 21°C and protected from light, the relative density of the mycelium in each well is measured via an absorbance measurement at 800nm. The antifungal efficacy is then calculated from these absorbance values.

[0083] The antifungal efficacy, observed at 4 days of incubation, of an extract obtained with the process according to the invention and of an extract obtained with a conventional process is shown in Figure 2. The results are similar to those shown in Figure 2 up to at least 15 days of incubation.

[0084] Example 4, antifungal action

[0085] The MICs (Minimum Inhibitory Concentrations) for 100% efficacy for up to 240 hours were measured with the extract according to example 2 on different fungal strains. The results are detailed in the table below.

[0086] Mushroom MIC g / L

[0087] Byssochlamys nivea 28

[0088] Nectria galligena 13

[0089] Monillinia laxa 8

[0090] Alternaria daucil 7

[0091] Helminthosporium solani 2

[0092] Gibberella zeae 9 Fusarium culmorum 9

[0093] Mycosphaerella graminicola 1

[0094] Example 5, antibacterial action

[0095] The MICs of the extract from Example 2 were determined for different bacterial species. Tests were performed on 27 bacterial strains listed in the table below. The study was conducted in nutrient-rich media, with a calibrated colony concentration of 5 x 10⁻¹³. 5 -10 6 CFU / mL.

[0096] Bacteria MIC mg / ML

[0097] Bacillaries

[0098] Bacillus cereus 0.234

[0099] Bacillus subtilis 0.938

[0100] Staphylococcus aureus 0.469

[0101] S. aureus MR (MRSA) 0.469

[0102] Staphylococcus epidermidis 0.234

[0103] Listeria monocytogenes 0.469

[0104] Lactobacilla

[0105] Enterococcus hirae 0.469

[0106] Lactobacillus acidophilus 7.5

[0107] Lactobacillus casei 7.5

[0108] Lactobacillus plantarum > 7.5

[0109] Streptococcus mutans 3.75

[0110] Streptococcus pyogenes 0.234

[0111] Streptococcus suis 0.469

[0112] Selenomonadaceae

[0113] Veillonella dispar 0.938

[0114] Clostridiales

[0115] Clostridium difficile 0.938

[0116] Enterobacteriaceae

[0117] Salmonella enterica typhimurium 1,875

[0118] Escherichia coli 7.5

[0119] Yersinia enterocolitica 3.75

[0120] Vibrionales

[0121] Vibrio cholerae 0.938

[0122] Vibrio eel > 7.5

[0123] Campylobacteraceae

[0124] Campylobacter jejuni 1,875 Bacteroides

[0125] Bacteroides fragilis 3.75

[0126] Bifidobacteria

[0127] Bifidobacterium brev 1 ,875

[0128] Bifidobacterium lactis 1 ,875

[0129] Bifidobacterium long um long um 0.938

[0130] Actinomycetales

[0131] Actinomyces naeslundii 3.75

[0132] Propionibacterium acnes 0.1 17

[0133] The extract from Example 2 shows inhibitory activity against all tested strains except Lactobacillus plantarum and Vibrio anguillarum. The most sensitive strain tested is P. acnes, a pathogen responsible for acne. Finally, bacteria of the order Bacillales, Enterococcus sp., and certain Streptococcus sp. are the most sensitive to the extract shown in Example 2. In contrast, the other tested strains are less sensitive, notably the beneficial bacteria Bifidobacterium sp. and Lactobacillus sp., as well as Gram-negative bacteria.

[0134] The extract from example 2 is a broad-spectrum antimicrobial, with a more pronounced efficacy against skin pathogens.

[0135] Example 6, antioxidant activity

[0136] We study the antioxidant activity of the extract from example 2 by comparing the condition of banana peels kept in the open air with or without application of the extract from example 2 at 7 days and 9 days after application.

[0137] Without application of extract from example 2, at 7 days banana peels are observed to be covered with brown spots characteristic of their oxidation, while the treated banana peels are little affected (1 characteristic spot).

[0138] At 9 days, the oxidation of the peel of untreated bananas continues with entire areas blackened from the constellation observed at 7 days, while the peel of treated bananas changes little compared to the observation at 7 days.

[0139] This antioxidant activity observed in bananas demonstrates the potential of the extract according to the invention for treating oxidative stress in plants, particularly exotic or tropical fruits. REFERENCES

[0140] Alexa, E., Poiana, M. A. & Sumalan, R. M. Mycoflora and ochratoxin a control in wheat grain using natural extracts obtained from wine industry by-products. Int. J. Mol. Sci. 13, 4949-4967 (2012).

[0141] - Casazza, A. a., Aliakbarian, B., Mantegna, S., Cravotto, G. & Perego, P. Extraction of phenolics from Vitis vinifera wastes using non-conventional techniques. J. Food Eng. 100, 50-55 (2010).

[0142] Favaron & Lucchetta, Role of grape polyphenols on trans-resveratrol activity against Botrytis Cinerea and of fungal Laçasse on the solubility of putatibe grapepr proteins J. of Plant Pathology vol 91 , n° 3, 579-588 (2009)

[0143] Goupil, P. et al. Grape marc extract acts as elicitor of plant defence responses.

[0144] Ecotoxicology 21 , 1541-1549 (2012).

[0145] Luque-Rodriguez & al. Extraction of polyphenols from Vine shoots of Vitis vinifera by Superheated Ethanol-Water Mixtures J. of Agriculture and Food Chemistry vol 54, n° 23, 8775-8781 (2006)

[0146] Osorio & al Biological efficiency of polyphenolic extracts from pecan nuts shell (Carya lllinoensis), pomegranate husk (Punica granatum) and créosote bush leaves (Larrea tridentate Cov.) against plant pathogen fungi Industrial Crops and Products, col 31 , n° 1 , 153-157 (2010),

[0147] - Pezet, R., Gindro, K., Viret, O. & Spring, J. L. Glycosylation and oxidative dimerization of resveratrol are respectively associated to sensitivity and résistance of grapevine cultivars to downy mildew. Physiol. Mol. Plant Pathol. 65, 297-303 (2004).

[0148] Quan, P. T., Hang, T. Van, Ha, N. H., De, N. X. & Tuyen, T. N. Microwave-assisted extraction of polyphenols from fresh tea shoot. Sci. Technol. Dev. 9, 69-75 (2006). - Sanchez, J. B. J., Orea, J. M., Gonzalvez, A. G. & Urena, A. G. On the Use of the Own Plant's Defence Compounds to Maintain the Post-Harvest Fruit Quality. Open Agric. J. 43-48 (2008).

[0149] - CN 104 177 463, CN 104 435 135, CN 102 757 512, CN 104 256 432, CN 104 256 641 , CN 103 783 506, CN 102 757 509, CN 101 816 349, CN 19 35 947, CN 205 759 861 , CN 103 875 842

[0150] - EP 2 530 059

[0151] - FR 2 976 062

[0152] - JP 2016 102192

[0153] - WO 2012 / 045923,

[0154] - US 5,989,557, US 2012 / 0142105

Claims

DEMANDS 1. A process for preparing a polyphenol-rich extract of dry plant biomass comprising (a) a step of extracting the dry biomass by contacting it with an aqueous solvent and (b) a step of recovering the polyphenol-enriched aqueous phase, characterized in that in the extraction step (a), the plant biomass / aqueous solvent mixture is treated simultaneously or sequentially by (i) electromagnetic waves with frequencies ranging from 915 MHz to 28 GHz, and (ii) stirring of the mixture, and / or (iii) a pressure of 5,000 to 95,000 Pa (50 to 950 mbars).

2. A process according to claim 1, characterized in that the aqueous solvent is water or an ethanol / water mixture comprising 10 to 70% by volume of ethanol.

3. A process according to claim 2, characterized in that the aqueous solvent is an ethanol / water mixture comprising 30 to 50% ethanol.

4. A process according to any one of claims 1 to 3, characterized in that the ratio by mass of dry plant biomass / aqueous solvent ranges from 1 / 5 to 1 / 30.

5. A process according to claim 4, characterized in that the ratio by mass of dry plant biomass / aqueous solvent ranges from 1 / 10 to 1 / 20.

6. A method according to any one of claims 1 to 3, characterized in that the frequency of the electromagnetic waves ranges from 915 MHz to 2.45 GHz.

7. A method according to any one of claims 1 to 6, characterized in that the power of the electromagnetic waves ranges from 300 W to 100 kW.

8. Method according to claim 7, characterized in that the power of the electromagnetic waves ranges from 1 to 75 kW.

9. A method according to any one of claims 1 to 8, characterized in that the extraction step (a) further comprises a treatment (iv) by ultrasound having a frequency of 25 kHz to 1 MHz.

10. Method according to claim 9, characterized in that the power of the ultrasound goes from 200 to 4000 W. 1 1. A process according to any one of claims 1 to 10, characterized in that the plant biomass consists of vine shoots of Vitis sp.

12. A process according to any one of claims 1 to 11, characterized in that it comprises a step (c) of concentrating polyphenols by partial or total evaporation of the aqueous solvent.

13. A process according to claim 12, characterized in that the concentration (c) is done by freeze-drying the recovered aqueous phase.

14. Polyphenol-rich extract obtainable by the process according to any one of claims 1 to 13.

15. Composition characterized in that it comprises an extract according to claim 14 and a vehicle suitable for its use.

16. Use of an extract according to claim 14 or of a composition according to claim 15 for the prevention and treatment of fungal infections on plants.

17. Use of an extract according to claim 14 or of a composition according to claim 15 for the prevention and treatment of fungal infections on fruits and vegetables after harvest.

18. Use of an extract according to claim 14 or of a composition according to claim 15, for the prevention and / or treatment of oxidative stress in plants.

19. Use of an extract according to claim 14 or of a composition according to claim 15 as an antioxidant agent in a cosmetic or food composition.

20. Extract according to claim 14 or composition according to claim 15, for their use in therapy.

21. Extract according to claim 14 or composition according to claim 15, for their use in the treatment of skin infections.

22. Extract according to claim 14 or composition according to claim 15, for their use according to claim 21, characterized in that the skin infection is acne.

23. Extract according to claim 14 or composition according to claim 15, for their use in the treatment of oxidative stress in humans or animals.

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