Citrate perhydrates and uses thereof

Abstract

The invention relates to citrate perhydrates and to the uses of citrate perhydrates, in particular as biocides, in particular pesticides, more particularly phytopharmaceuticals.

Claims

1. A citrate perhydrate of alkali metal being a disodium citrate perhydrate, wherein the disodium citrate perhydrate is in a powder form, the powder being physically and chemically stable without significant alteration after one year at a temperature of from 20 to 25° C., in their physical state and in their chemical composition with regard to the concentration of active oxygen.

2. The citrate perhydrate of alkali metal according to claim 1, being an anhydrous disodium citrate monoperhydrate.

3. The citrate perhydrate of alkali metal according to claim 1, having a solubility greater than or equal to 850 g/l at 25° C. in water.

4. The citrate perhydrate of alkali metal according to claim 1, having a pH in aqueous solution of 5.2.

5. The citrate perhydrate of alkali metal according to claim 1 that when subjected to a temperature ranging from 100° C. and 220° C., measured by thermogravimetric analysis under a nitrogen atmosphere and in the temperature range of between 30 and 250° C. following a temperature ramp of 10° C./min, followed by a hold at the final temperature for a period of 10 minutes such that the powder shows a mass loss of less than 1% below 140° C., and between 2 and 3% between 140 and 220° C.

6. The citrate perhydrate of alkali metal according to claim 1, in the form of a crystal formed of disodium citrate and hydrogen peroxide.

7. A composition comprising the citrate perhydrate as defined in claim 1, and urea perhydratein the form of a urea-hydrogen peroxide co-crystal.

8. An antimicrobial agent for use in humans or animals, comprising disodium citrate perhydrate according to claim 1.

9. A tooth whitening agent for a use in dental medicine comprising disodium citrate perhydrate according to claim 1.

10. A pharmaceutical composition or phytopharmaceutical composition constituted by or comprising a disodium citrate perhydrate according to claim 1.

11. A biocide composition comprising a disodium citrate perhydrate according to claim 1.

12. The biocide composition according to claim 11, wherein the disodium citrate perhydrate is in the form of a crystal formed of disodium citrate and hydrogen peroxide.

13. The biocide composition according to claim 11, further comprising water and/or at least one additional compound selected from pH regulators, anti-agglomerating agents, surfactants, wetting agents, antifoaming agents, anti-drift agents, thickeners, foaming agents, solidifying agents, fertilizers, phytopharmaceutical products, stabilisers, glycolipids and mixtures thereof.

14. A method for inhibiting or preventing the growth of a pathogen on or in a plant, wherein said disodium citrate perhydrate according to claim 1 is applied to the surface of the plant in an amount of from 25 to 1000 ng.Math.dm.sup.−2.

15. The method for inhibiting or preventing the growth of a pathogen on or in a plant according to claim 14, wherein said disodium citrate perhydrate is applied in the presence of water and/or at least one additional compound selected from pH regulators, anti-agglomerating agents, surfactants, wetting agents, antifoaming agents, anti-drift agents, thickeners, foaming agents, solidifying agents, fertilizers, phytopharmaceutical products, stabilisers, glycolipids and mixtures thereof.

16. The method for inhibiting or preventing the growth of a pathogen on or in a plant according to claim 14, wherein said disodium citrate perhydrate is applied in the presence of urea perhydrate in the form of urea-hydrogen peroxide co-crystals.

17. The method for inhibiting or preventing the growth of a pathogen on or in a plant according to claim 14, wherein the pathogen is selected from viruses, bacteria, fungi and pseudofungi, and wherein the plant is selected from fruit-bearing plants, vegetable-bearing plants, ornamental plants, turf and cereals.

18. A method for disinfecting a fluid or a surface, comprising applying disodium citrate perhydrate according to claim 1 to the fluid or to the surface.

19. The method for disinfecting a fluid or a surface according to claim 18, wherein said disodium citrate perhydrate is co-crystallised with urea perhydrate in the form of urea-hydrogen peroxide co-crystals.

20. A method for preparing a citrate perhydrate of alkali metal according to claim 1, said method comprising: (i) a step of bringing a disodium citrate into contact with hydrogen peroxide, to obtain said disodium citrate perhydrate, said step (i) optionally being preceded by a step of neutralisation of a citric acid with a hydroxide, a carbonate or a citrate of sodium, in order to obtain the disodium citrate as mentioned in step (i), or (i′) a step of bringing into contact citric acid; a hydroxide, carbonate or citrate of sodium; and hydrogen peroxide, to obtain said disodium citrate perhydrate of alkali, alkaline earth, transition or post-transition metal.

21. A method for preparing a composition according to claim 7, said method comprising a step (a) of co-crystallisation by bringing into contact a disodium citrate, urea, and hydrogen peroxide, said step (a) optionally being preceded by a step of neutralisation of a citric acid with a hydroxide, a carbonate or a citrate of sodium, in order to obtain the disodium citrate as mentioned in step (a), or (a′) a step of bringing into contact citric acid; a hydroxide, carbonate or citrate of sodium; urea; and hydrogen peroxide, to obtain said disodium citrate perhydrate.

Description

FIGURES

(1) FIG. 1 shows the distribution graph for citric acid and the salts thereof.

(2) FIG. 2 corresponds to the powder graph for the trisodium citrate monoperhydrate dihydrate of example 2 (λ=1.5418 Å).

(3) FIG. 3 shows the asymmetric unit and the schematic labelling of the trisodium citrate monoperhydrate dihydrate of example 2.

(4) FIG. 4 corresponds to the powder graph for the disodium citrate perhydrate of example 3 (λ, =1.5418 Å).

(5) FIG. 5 illustrates the diffractogram of the co-crystallisation of one mole of disodium citrate perhydrate and 3 mol of urea perhydrate (λ=1.5418 Å) according to example 4.

(6) FIG. 6 corresponds to the logarithmic concentration of the different pathogenic strains initially present, and the logarithmic decrease in the strains after treatment with formulation 3 at a hydrogen peroxide concentration C1 (=0.5%) and C2 (=3%).

(7) FIG. 7 corresponds to micrographs of the fungus Erysiphe necator.

(8) FIG. 7A: in water. FIG. 7B: in the presence of citrate perhydrate (10 mg/ml).

(9) FIG. 8 illustrates the results obtained during the field evaluation of the efficacy of formulation 3 of the invention for the treatment of powdery mildew according to example 5.5. The percentage incidence and severity of the disease is given both for leaves (FIG. 8A) and for grapes (FIG. 8B).

EXAMPLES

Example 1: Synthesis of Citrate Perhydrates

(10) A method for preparing the citrate perhydrates of the present invention consists in crystallising hydrogen peroxide with a salt of citric acid.

(11) Only citrate perhydrates which form the subject matter of the present invention can be produced using the preparation method presented below.

(12) The equipment likely to be used consists of a gravimetric feeder for the raw materials, a twin-screw extruder for the slurry crystallisation reaction, followed by a fluidised bed dryer, or a vacuum microwave dryer, and a granulator.

(13) The raw materials for the method are hydrogen peroxide, in the form of an aqueous solution concentrated from 30 to 80%, and a salt of citric acid. The citric acid salt may, inter alia, be obtained by partial or total neutralisation of the citric acid with a carbonate, a hydroxide or one of its own salts, the cations of which are selected from the alkali, alkaline earth, transition or post-transition metals suitable for the production of the desired citrate perhydrate of the present invention. The citric acid may, inter alia, be neutralised prior to the crystallisation reaction by mixing the powders or directly within the extruder by individually injecting each component.

(14) Step 1: Crystallisation Reaction

(15) The raw materials are injected into a twin-screw extruder using a gravimetric feeder. The quantity of raw materials injected observes the stoichiometry of the desired citrate perhydrate of the present invention. For example, in the case of the preparation of anhydrous disodium citrate monoperhydrate, one possible production method is the crystallisation of 2 mol of trisodium citrate and 1 mol of citric acid with 3 mol of hydrogen peroxide.

(16) The raw materials are mixed within the twin-screw extruder and begin to crystallise at controlled temperature and residence time, to produce a solid at the outlet of the extruder. For example, in the case of the production of an anhydrous disodium citrate monoperhydrate, the crystallisation temperature is 55-65° C. and the residence time is approximately 1 minute, when the solid raw materials used are anhydrous. It should be noted that the use of hydrated solid raw materials requires an extruder fitted with a degassing system, greatly reduces the exothermic nature of the reaction and can significantly prolong the residence time in the extruder.

(17) At this stage, the solid obtained at the outlet of the extruder is thixotropic and can be readily shaped, for instance into granules, without agglomerating.

(18) In order to complete the crystallisation of the desired citrate perhydrate of the present invention, the solid obtained at the outlet of the extruder is cooled down to 15-25° C. by natural convection. The discharging of excess water from the crystallisation reaction can be observed visually on the surface of the solid.

(19) Step 2: Drying and Grinding

(20) Once crystallised, the citrate perhydrate can be dried at a controlled temperature using a fluidised bed dryer or a vacuum microwave dryer, then ground to the desired particle size, since, at this final stage, the product is no longer thixotropic. For example, in the case of the production of an anhydrous disodium citrate monoperhydrate, the drying temperature is 40-60° C.

(21) Variant for Production of a Citrate Perhydrate Co-Crystallised with Urea Perhydrate.

(22) A citrate perhydrate according to the present invention can be produced by co-crystallisation with urea to form a co-crystal of citrate perhydrate and urea perhydrate.

(23) To this end, urea is also injected by gravimetric feeding into the twin-screw extruder. The molar ratios to be observed range from 1 to 5 mol of urea per mole of salt of citric acid, preferentially 3 mol of urea per mole of salt of citric acid.

(24) The amount of hydrogen peroxide should be adapted to observe the stoichiometry of the desired crystals of citrate perhydrate resulting from the present invention and of urea perhydrate. For example, in the case of producing a co-crystallisation of 1 mol of trisodium citrate monoperhydrate dihydrate and 3 mol of urea perhydrate, 4 mol of hydrogen peroxide crystallise with 1 mol of trisodium citrate and 3 mol of urea.

(25) This production method has significant advantages over independent production of urea perhydrate which is then mixed in solid form with the citrate perhydrates produced. This is because the urea perhydrate available on the European market is sold at approximately 20 €/kg while urea is sold at less than 1 €/kg. Moreover, urea perhydrate produced independently is generally stabilised by adding stabiliser which is relatively toxic, which does not make it compatible with a zero-residue biobased biocide such as the citrate perhydrates of the present invention, whereas urea perhydrate produced by co-crystallisation with a citrate perhydrate is stable without adding stabilisers. This is probably due to the presence of citrate as a natural and non-toxic stabiliser.

(26) Variant for Production of a Citrate Perhydrate from an Alcohol-Based Solution.

(27) A citrate perhydrate can be obtained by crystallisation in an alcohol-based solution.

(28) To this end, a first solution is prepared containing the salt of citric acid and hydrogen peroxide, the amounts of which observe the stoichiometry of the desired citrate perhydrate resulting from the present invention. The citric acid salt may, inter alia, be obtained by partial or total neutralisation of the citric acid with a carbonate, a hydroxide or one of its own salts, the cations of which are selected from the alkali, alkaline earth, transition or post-transition metals suitable for the production of the desired citrate perhydrate resulting from the present invention.

(29) A second solution is prepared: an alcohol-based solution, in which the alcohol contains in particular from 1 to 5 carbon atoms and which may more particularly be ethanol. This solution may also be the alcohol itself.

(30) These two solutions are subsequently mixed. The volume ratio of the alcohol-based solution is between 3.7:1 and 8:1 relative to the first aqueous solution containing the citrate and the hydrogen peroxide.

(31) The citrate perhydrates produced precipitate in the form of crystals and are recovered using liquid-solid separation techniques known to the person skilled in the art (filtration, centrifugation, etc.) and are optionally dried at 40-60° C.

Example 2: Trisodium Citrate Monoperhydrate Dihydrate

(32) The trisodium citrate monoperhydrate dihydrate was prepared as indicated in example 1.

(33) 2.1. Crystalline Structure

(34) Materials and Methods

(35) Powder X-Ray Diffraction

(36) The samples were carefully ground to a fine powder using a pestle and mortar. The powder X-ray diffraction data was collected using a PANalytical XPERT-PRO diffractometer (Bragg-Brentano geometry, Cu Kα radiation (λ=1.5418 Å), generator settings: 45 kV and 30 mA). The powder graphs were measured from 4 to 40°, 2θ, and the measurement time was from 6 to 15 minutes.

(37) Results

(38) The diffractogram obtained, given in FIG. 2, and also the characteristic lines in table 1, show an unknown crystalline structure which differs from the starting product, from trisodium citrate, and from all its hydrated forms:

(39) TABLE-US-00003 TABLE 1 Characteristic lines of trisodium citrate monoperhydrate dihydrate Relative hkl Peaks 2θ intensity index 1 9.924509 100 0 0 1 2 8.740994 5.95 0 1 0 and 0 1 -1 3 6.148828 0.87 1 0 0 4 5.519614 15.76 −1 0 1 5 5.483783 36.95 0 −1 2 6 5.372527 51.54 −1 1 0 7 4.959513 16.42 −1 −1 1 and 0 0 2 8 4.871902 5.55 0 −2 1 9 4.740059 4.39 1 1 0 10 4.413263 36.26 −1 1 1 11 4.381867 6.14 0 −2 2 12 4.364081 19.23 0 2 0 13 4.094722 2.37 −1 0 2 14 4.000887 38.77 1 −2 1 and 1 −1 2 15 3.679708 4.92 0 −1 3 16 3.660295 10.8 1 0 2 and −1 −2 1 17 3.62327 22.99 1 −2 2 18 3.514807 11.02 −1 −2 2 19 3.483591 3.3 0 −2 3 20 3.466081 14.3 0 2 1

(40) The characteristics of the crystal of trisodium citrate monoperhydrate dihydrate are given in table 2 below:

(41) TABLE-US-00004 TABLE 2 Characteristics of the crystalline structure of trisodium citrate monoperhydrate dihydrate Chemical formula C6 H11 O11 Na3 Molecular weight 328.12 g/mol Sodium citrate % by weight 78.7 molar ratio  1 Hydrogen peroxide % by weight 10.4 molar ratio  1 Water % by weight 10.9 molar ratio  2 Space group P-1 Crystal system Triclinic Length of unit cell (a)  6.2400 (4) Å Length of unit cell (b)  9.8204 (5) Å Length of unit cell (c)  11.1233 (7) Å α 115.846 (6) Å β  93.600 (5) Å γ  95.350 (5) Å Unit cell volume 606.69 (7) Å. ρ calculated  1.796 cm.sup.3

(42) The asymmetric unit contains an entirely deprotonated citrate anion, three sodium cations, two water molecules and two half molecules of hydrogen peroxide. Thus, the chemical formula given is Na.sub.3C.sub.6H.sub.11O.sub.11, as presented below and in FIG. 3.

(43) ##STR00002## Molecular structure of trisodium citrate monoperhydrate dihydrate

(44) 2.2 Water-Solubility

(45) The solubility of the compounds of the invention is determined by experiments at increasing concentrations of the compound of the invention in deionised water. The results show that trisodium citrate monoperhydrate dihydrate is entirely water soluble (>900 g/l at 20° C.).

(46) 2.3 pH of an Aqueous Solution of the Compound

(47) The pH measurements (using a pH meter) show that an aqueous solution of trisodium citrate monoperhydrate dihydrate diluted 20× is 7.6 (±0.3).

Example 3: Anhydrous Disodium Citrate Monoperhydrate

(48) The anhydrous disodium citrate monoperhydrate was prepared as indicated in example 1.

(49) 3.1. Crystalline Structure

(50) The powder X-ray diffraction data was collected using a Cu Kα diffractometer as described above and supplemented by synchrotron radiation measurements.

(51) The diffractogram obtained, presented in FIG. 4, and its characteristic lines given in table 3, show a crystalline structure unknown from databases, which differs from citric acid, from trisodium citrate and all its hydrated forms, from disodium citrate and all its hydrated forms, and also from trisodium citrate perhydrate.

(52) TABLE-US-00005 TABLE 3 Characteristic lines of anhydrous disodium citrate monoperhydrate Relative hkl Peaks 2θ intensity index 1 7.10442 2.42 0 1 1 2 6.53808 6.93 1 1 1 3 6.19763 11.5 0 2 0 4 5.03008 18.94 2 2 0 5 4.83206 0.76 1 2 1 6 4.45527 10.07 3 1 1 7 4.34762 32.9 2 2 1 8 4.29193 11.19 4 0 0 9 4.21333 17.21 3 20 10 3.97003 19.47 1 1 2 11 3.85293 13.47 4 0 1 and 2 0 2 12 3.78756 19.04 3 2 1 13 3.67804 12.75 4 1 1 14 3.53769 100 4 2 0 15 3.47303 5.61 1 2 2 16 3.42705 7.44 2 3 1 17 3.32368 6.66 3 1 2 18 3.2801 32.86 2 2 2 19 3.13095 31.11 3 3 1 20 3.09689 19.5 5 1 1

(53) The characteristics unique to the crystal of disodium citrate perhydrate are given in table 4.

(54) TABLE-US-00006 TABLE 4 Characteristics of the crystalline structure of anhydrous disodium citrate monoperhydrate Crystal Orthorhombic system #61 Pbca Length of unit cell (a)   8.6396 (25) Å Length of unit cell (b)  12.433 (4) Å Length of unit cell (c)  17.199 (5) Å Unit cell volume 1847.5 (8) Å.sup.3

(55) The measurements regarding the H bonds are given in table 5 below:

(56) TABLE-US-00007 TABLE 5 Hydrogen bonds in the crystalline structure of anhydrous disodium citrate monoperhydrate (*intramolecular) H bond D-A, Å H .Math. .Math. .Math. A, Å D .Math. .Math. .Math. A, Å D-H .Math. .Math. .Math. A, Å Overlap, e E, kcal/m O12-H21 .Math. .Math. .Math. O13 1.041 1.507  2.546 175.0 0.092 16.6 O17-H18 .Math. .Math. .Math. O22 0.976 1.852  2.770 155.7 0.041 11.1 O17-H18 .Math. .Math. .Math. O13 0.976 2.557* 3.063 112.5 0.009 5.2 O22-H24 .Math. .Math. .Math. O13 1.015 1.585  2.598 174.7 0.080 15.5 O23-H25 .Math. .Math. .Math. O13 0.994 1.605  2.596 174.8 0.064 13.8 C4-H10 .Math. .Math. .Math. O13 1.094 2.340  3.270 141.8 0.015 C2-H7 .Math. .Math. .Math. O13 1.095 2.482* 3.199 121.9 0.012

(57) The asymmetric unit corresponds to the formula Na.sub.2HC.sub.6H.sub.5O.sub.7(H.sub.2O.sub.2), and thus contains a citrate anion, two sodium cations and a molecule of hydrogen peroxide as presented below. There are no spaces in the structure to accommodate a water molecule.

(58) ##STR00003##

(59) 3.2. Water-Solubility

(60) The disodium citrate perhydrate is entirely water soluble (>800 g/l at 20° C.).

(61) 3.3. pH of an Aqueous Solution of the Compound

(62) The pH measurements (using a pH meter) show that, diluted (20×) in water, the disodium citrate perhydrate crystals obtained have a pH of 5.2 (±0.3).

(63) 3.4. Thermogravimetric Analysis (TGA)

(64) Thermogravimetric analyses of a crystalline powder of disodium citrate perhydrate according to example 1 were carried out, to assess the behaviour thereof at a temperature of from 100 to 220° C.

(65) The TGA mass loss graphs were obtained with a TA instruments (Waters) instrument under a nitrogen atmosphere and in the temperature range of between 30 and 250° C. A temperature ramp of 10° C./min was set up, followed by a hold at the final temperature (250° C. for this analysis) for a period of 10 minutes.

(66) A mass loss of less than 1% takes place below 140° C., probably corresponding to loss of water of crystallisation. The powder then lost between 2 and 3% of its mass between 140 and 220° C.

(67) These results demonstrate excellent stability at high temperatures.

Example 4: Co-Crystallisation of One Mole of Anhydrous Disodium Citrate Monoperhydrate and 3 Mol of Urea Perhydrate

(68) 4.1. Crystalline Structure

(69) The diffractogram obtained is presented in FIG. 5.

(70) The diffraction spectrum obtained shows that the powder produced is a co-crystallisation of anhydrous disodium citrate monoperhydrate and urea perhydrate, the most characteristic peaks of which are highlighted.

(71) 4.2 pH of an Aqueous Solution of the Compound

(72) The pH of an aqueous solution of the co-crystals of one mole of anhydrous disodium citrate monoperhydrate and 3 mol of urea perhydrate, diluted 20×, is 5.2 (±0.3).

Example 5: Performance

(73) 1. Formulation 1 Based on Co-Crystallised Trisodium Citrate Monoperhydrate Dihydrate and Urea Perhydrate

(74) 1.1. Preparation of the Formulation

(75) 200 g of a co-crystallisation containing 1 mol of trisodium citrate monoperhydrate dihydrate and 4 mol of urea perhydrate are mixed with 21 g of urea and 55 g of anhydrous citric acid. The mixture of powders is then dissolved in deionised water at different concentrations.

(76) 1.2. Biocidal Performance in Biotests

(77) Formulation 1 is tested in biotests on various pathogens. The results are presented in table 6.

(78) TABLE-US-00008 TABLE 6 Effective concentration [mg/ml] of formulation 1. Plasmopara viticola 24 Botiytis cinerea <5 Guignardia bidwellii 5 Helminthosporium solani 25 Collelotrichum coccodes 25 Monilia laxa strain 623 18 Monilia laxa INRA strain 50 Serpula lacrimens 18 Staphylococcus aureus 0.064 Pseudomonas aeruginosa 0.256 Erwinia amylovora 1.024 Ralstonia strain 06 0.512 Ralstonia strain R1 0.512

(79) 2. Formulation 2 Based on Anhydrous Disodium Citrate Monoperhydrate

(80) 2.1. Preparation of the Formulation

(81) The powder of example 3 is dissolved in deionised water at different concentrations.

(82) 2.2. Antifungal Performance

(83) Formulation 2 is tested in biotests on various pathogens. The results are presented in table 7.

(84) TABLE-US-00009 TABLE 7 Effective concentration [mg/ml] of formulation 2. Erysiphe necator 10 Botrytis cinerea  5-10 Monilia laxa strain 623 10-20 Monilia laxa INRA strain 34-50 Monilia fructigena 34-50

(85) 3. Formulation 3 Based on Co-Crystallised Anhydrous Disodium Citrate Monoperhydrate and Urea Perhydrate

(86) 3.1 Preparation of the Formulation

(87) The powder of example 4 is dissolved in deionised water at different concentrations.

(88) 3.2. Antifungal Performance

(89) Formulation 3 is tested in biotests on the fungi Plasmopara viticola, Erysiphe necator, Guignardia bidwellii and Monilia fructigena. The results are presented in table 8.

(90) TABLE-US-00010 TABLE 8 Effective concentration [mg/ml] of formulation 3 Plasmopara viticola 30 Erysiphe necator 10 Botrytis cinerea  1-5 Guignardia bidwellii 25-50 Monilia laxa strain 623 10-20 Monilia laxa 17-25 INRA strain Monilia fructigena 17-25

(91) 4. Formulation 4 Based on Co-Crystallised Anhydrous Disodium Citrate Monoperhydrate and Urea Perhydrate

(92) 4.1. Preparation of the Formulation

(93) 62 g of the powder described in example 4 are mixed with 10 g of anhydrous citric acid, 3 g of lactic acid, 2 g of anhydrous calcium lactate, 1.5 g of a surfactant and 1.5 g of a desiccant. The powder mixture is then dissolved in deionised water at different concentrations.

(94) 4.2. Antibacterial Performance

(95) Formulation 4 is tested in biotests on six pathogenic strains according to standard EN1040. The results are presented in FIG. 6.

(96) 5. In Vitro Tests

(97) The efficacy of formulations 2 and 3 as described above is analysed using biotests on the fungus Botritys cinerea in terms of conidia germination (table 9) and mycelium growth (table 10) compared with the reference chemical fungicide (Teldor, Bayer), as well as biotests on the fungus Venturia inaequalis in terms of conidia germination (table 11) compared with the reference chemical fungicide (Merpan, Adam France).

(98) TABLE-US-00011 TABLE 9 efficacy (%) of formulations 2 and 3 in relation to Botritys cinerea (conidia germination) formulation/ concentration (mg/ml) 2 5 10 Formulation 2 — 100 100 Formulation 3 100 100 100 Teldor (reference)  79  81  81

(99) TABLE-US-00012 TABLE 10 efficacy (%) of formulations 2 and 3 in relation to Botritys cinerea (mycelium growth) formulation/concentration (mg/ml) 5 10 15 20 30 Formulation 2 25- 50- 50- 50- 75- 49.99 74.999 74.999 74.999 100 Formulation 3 75- 75- 75- 75- 75- 100 100 100 100 100 Teldor 50- 50- 50- 50- — (reference) 74.999 74.999 74.999 74.999

(100) TABLE-US-00013 TABLE 11 efficacy (%) of formulations 2 and 3 in relation to the fungus Venturia inaequalis (conidia germination) Formulation/ concentration (mg/ml) 2 5 10 Formulation 2 100 100 100 Formulation 3 100 100 100 Merpan (reference) 100 100 100

(101) 6. Antifungal Performance: Other Field Validation

(102) The experiment is performed on a Swiss vineyard in accordance with good agricultural practices (GAP) as defined in Article R 253-1 of the French Rural Code for data relating to the biological evaluation of plant-protection products. The test aims to evaluate the growth of powdery mildew both on leaves and bunches of grapes. Seedlings are treated weekly by application of a spray mixture at 200 l/ha. The test plots are described as indicated below: An untreated plot (TNT); A plot treated with formulation 3 at 30 g/l, to which 1% SiO.sub.2 and 0.5% heptamethyltrisiloxanes (wetting agent, De Sangosse—Agridyne) have been added, corresponding to 6 kg per hectare of vines (Biogel solo); A plot treated which a customary reference chemical fungicide (customary schedule); A plot treated with a reference fungicide authorised for organic agriculture (organic schedule).

(103) The efficacy of the formulation tested is evaluated based on 2 criteria: the percentage incidence and severity of the disease, both on the leaves (FIG. 8A) and on the grapes (FIG. 8B).

Example 6: Instability of Concentrated Solutions of Citric Acid and Hydrogen Peroxide

(104) The stability of a concentrated solution of hydrogen peroxide and citric acid is studied.

(105) To this end, a solution containing 37.5% hydrogen peroxide and 25% citric acid is prepared. The concentration of hydrogen peroxide is then measured using permanganate titration three times over two months. The content of peracids is also measured based on a colorimetric test strip method.

(106) The results are presented in table 12:

(107) TABLE-US-00014 TABLE 12 Results of the change in a solution containing 37.5% hydrogen peroxide and 25% citric acid Date of wt % wt % measurements Hydrogen peroxide Peracids D 0 37.5 0 D 0 + 16 days 32.6 5 D 0 + 2 months 24.6 5

(108) These results show that the solution loses 34.4% of its concentration in hydrogen peroxide after 2 months. 5% peracids are also observed to appear in solution after 18 days. Moreover, an increase in pressure followed by gas release is observed over time.

Example 7: Comparative Performance of the Citrate Perhydrates of the Invention Compared to Aqueous Solutions of Hydrogen Peroxide, Citrates and Citric Acid

(109) 1. Action on Botrytis cinerea

(110) Tests carried out according to a standard protocol on different target fungi, including Botrytis cinerea, showed that, at equivalent concentrations, neither the citrate alone nor the hydrogen peroxide alone have a fungicidal or fungistatic effect, unlike the compounds of the invention (cf. table 13 below).

(111) This is moreover confirmed by Gil-ad et al. (FEMS Microbiology Letters 1999, 176, 455-461), indicating that Botrytis cinerea can germinate in the presence of hydrogen peroxide at concentrations up to 180 mM (6 mg/ml), and its mycelium can grow at even higher concentrations.

(112) TABLE-US-00015 TABLE 13 Comparative results of biotests on Botrytis cinerea (Agroscope 07-2019) Échantillon Formule chimique pH H.sub.2O.sub.2 (M) Citrate (M) Na/Citrate MIC Botrytis (mM) Disodium citrate sesquihydrate Na.sub.2 H C.sub.6H.sub.5O.sub.7 1 ½H.sub.2)O 4.9 0 0.2 2 non actif Disodium citrate perhydrate Na.sub.2 H C.sub.6H.sub.5O.sub.7 H.sub.2O.sub.2 4.9 0.2 0.2 2 108 Trisodium citrate perhydrate Na.sub.3 C.sub.6H.sub.5O.sub.7H.sub.2O.sub.2 2 H.sub.2O 8.2 0.2 0.2 3 72 Hydrogen peroxide H.sub.2O.sub.2 6.4 0.2 0 0 non actif Acide citrique C.sub.6H.sub.8O.sub.7 non actif [Key: échantillon = sample; Formule chimique = Chemical formula; Acide citrique-Citric acid; non actif-not active]

(113) The disodium citrate perhydrate preferably crystallises with the hydrogen peroxide, rather than with the water, and forms a reactive biocidal barrier. Indeed, when the disodium citrate perhydrate is placed in aqueous solution for spraying, i.e. when the disodium citrate and the hydrogen peroxide are sprayed onto a surface, the water evaporates and the disodium citrate perhydrate evaporates again to form a reactive biocidal barrier, whereas a solution of hydrogen peroxide simply evaporates. This enables a persistent effect for the product of the invention.

(114) 2. Action on Staphylococcus aureus

(115) Tests were carried out according to a standard protocol on Staphylococcus aureus MRSA, comparing the disodium citrate perhydrate of the invention to sodium citrate, to hydrogen peroxide and to a reference antiseptic.

(116) The results of these tests are given in table 14:

(117) TABLE-US-00016 TABLE 14 Comparative results of biotests on Staphylococcus Aureus MRSA MIC value % mM Sodium citrate 3.20 mg/ml 0.320  12.40 -> (pH 5 -> 8)  13.56 Hydrogen peroxide 0.94 mg/ml 0.094  27.58 PVP-I (Povidone-iodine) 6.25 mg/ml 0.625  17.13 Ethanol 87.5 mg/ml 8.750 1899.35 Disodium citrate 0.03 mg/ml 0.003   0.12 per hydrate of the invention

(118) Given the molecular structure of the disodium citrate perhydrate, the comparison of the efficacy of the compound of the invention compared to sodium citrate and hydrogen peroxide is easy (in equimolar amounts).

(119) It should be noted that the disodium citrate perhydrate has a growth-inhibiting efficacy (MIC) for Staphylococcus aureus MRSA which is 230 times greater than that of hydrogen peroxide alone and 103 times greater than sodium citrate.