FR2734572A1 - NOVEL ANTHOCYANIC COLORANTS, PROCESSES FOR PREPARING THEM AND COLORED COMPOSITIONS CONTAINING SAME - Google Patents

Abstract

Novel anthocyanin colouring agents of formula (I), wherein R1, R2, R3, R4 and R5 are selected from the groups usually found on the flavylium ring of anthocyanins, and R and R', which are the same or different, are a hydrogen atom, a functional grouping such as a carboxylic acid, an aldehyde, an alcohol, an amine, an amide, a thiol, a straight, branched or cyclic, saturated or unsaturated alkyl group with one or more carbon atoms, an aromatic or heterocyclic grouping, said alkyl group and aromatic or heterocyclic grouping being optionally substituted by functional groupings, for example alcohol, carboxylic acid, amine, amide, aldehyde or ketone functionalities, or R and R', together with the carbon atoms to which they are attached, form a ring structure with several optionally saturated, optionally substituted bonds which may contain a heteroatom; methods for preparing said novel anthocyanin colouring agents, and coloured compositions containing them.

Description

NEW ANTHOCYANIC COLORANTS, THEIR
PREPARATION METHODS AND COLORED COMPOSITIONS
CONTAINER.

 The present invention relates to new dyes of the anthocyanin group, the compositions the containers and their methods of preparation.

 Many natural molecules have coloring properties. Among these, anthocyanins are compounds widely used in nature that are responsible for the orange, red or blue coloring of many plants and in particular most fruits. Anthocyanins are perfectly safe and may even have interesting nutritional properties (8). Anthocyanins are therefore good candidates for the development of dyes in the fields of nutrition and cosmetology.

 Indeed, the increasing mistrust of consumers vis-à-vis artificial food additives, considered useless sometimes even toxic, leads some to wish the removal of dyes. However, color often reflects the quality of food products and determines their acceptability by consumers. Thus, natural dyes tend to replace synthetic dyes (5, 9); but the natural colors of foods, mainly fruits and vegetables, are very often degraded during processing operations (action of enzymes during grinding or pressing, thermal degradation, oxidation) which limits their use except to associate them with stabilizers.

Consumer demand for colorful, non-toxic attractants therefore requires the availability of natural dyes such as anthocyanins.

 Very many sources of anthocyanins have been proposed such as grape marc, red cabbage, elderberry, blackcurrant, etc. and are used industrially for the preparation of dyes; but they are generally relatively crude extracts containing, in addition to the free anthocyanins, in the glycosilated form, other molecules capable of stabilizing them and / or of modifying their color, or by copigmentation phenomena, it is a question of then of covalent associations between an anthocyanin molecule and a copigment, such as a phenol acid, a flavonoid or metal ions, or by phenomena of complexation and it is then about covalent bonds; such complexes formed by covalent reaction between anthocyanins and tannins would be at the origin of the color of old wines.

 In aqueous solution, the anthocyanin molecules exist in four equilibrium forms (4).

The red form, corresponding to the flavylium cation, predominant in acidic medium and much more stable than the other forms, becomes a minority, or even absent, when the pH increases. In addition to this behavior with respect to the pH which forbids the use of the anthocyanin dyes known today in dairy and meat products of pH higher than 4, the preparations proposed from these molecules generally prove very unstable during the storage.

These natural anthocyanin molecules, whose flavylium nucleus is represented below, have a very wide variety of structures.

 They comprise about twenty differently hydroxylated or methoxylated aglycones and glycosylated forms that can be acylated. These various substitutions give them different coloring properties and stabilities. In addition, the copigmentation phenomena and the formation of covalent bonds, in particular with tannins or ethanal, also affect these characteristics. A range of colors from orange to purple can be obtained. However, many factors, including pH, temperature, the presence of oxygen but also that of bleaching agents or antioxidants such as sulphites and ascorbic acid, contribute under certain conditions to degrade these molecules, modifying thus their coloring properties.

 It has therefore been proposed in the prior art to associate with the anthocyanin dyes photoprotective agents for stabilizing the colors.

 Monoglucoside anthocyanins are markedly more stable to discoloration than the corresponding aglycones (7). Similarly, the diglucosides, having an additional 5-substitution, are much more stable than the corresponding 3-monoglucosides. However, they are more sensitive to browning, probably because of the sugar at position 5 which participates in Maillard type reactions (Francis, 1989). Substitutions at the 4-position, for example with a methyl or phenyl group, also confer increased stability on the chromophore, especially with regard to discoloration by an additive commonly used in the food industry, sulphite (Timberlake and Bridle, 1967).

 The purpose of the present invention is to propose new red dyes of natural origin, having in solution a greater stability than that of anthocyanins, especially in a wider pH range, allowing to broaden their field of application traditionally limited to the beverage industry. In addition, the relative lipophilicity and hydrophobicity of these pigments allows their use in lipid or emulsion-type media which constitute the bulk of these potential new markets (dairy products, sauces derived from mayonnaises, cosmetics, etc.).

 These new pigments, red to orange, were initially obtained from wine, in the form of pure chemical species perfectly defined, then they were analyzed, characterized and synthesized in the laboratory by the inventors, according to methods also being the subject of the present invention.

 This series of new anthocyanin derivatives have the structural characteristics conducive to color stabilization (substitution in both the 5-position by a non-osidic group and in the 4-position in the flavylium ring). In addition, they meet the desired objectives for applications in the food or cosmetology field, in particular improved heating resistance, increased stability over a wider pH range and color retention in the presence of sulfite.

The anthocyanin dyes according to the invention more particularly correspond to the general formula I

in which
the radicals R 1, R 2, R 3, R 4 and R 5 are chosen from the groups usually encountered on the flavylium nucleus of anthocyanins or equivalent groups, some of which are specified in the description which follows,
the radical R represents a substantially electron-donated, preferably aliphatic, alicyclic, aromatic or saturated or unsaturated, optionally substituted carbon donor electron group, and
the radical R 'represents an essentially carbon-containing electron-attracting group advantageously chosen from a hydrogen atom, an -OH group, a -COOH group, a -COH group, a -CH 2 OH group or a -COOR "group;"represents a branched or unbranched alkyl group of 2 to 5 carbons optionally substituted with one or more -OH, -COOH, -COH groups.

 More particularly, the invention relates to the anthocyanin dyes of formula (I) in which the radical R is chosen from a phenyl radical substituted by one or more -OH group, -OCH 3, alkyl or heteroalkyl, -SH, -NO, - SO3H, -NH2, -OR "'where R"' represents an optionally mono- or multi-acylated monosaccharide, the acylating group of which is itself optionally substituted by an ose; among these, the dyes of formula (I) in which the radical R is a mono, di or triphenol group optionally substituted with one or more -OCH 3 groups are preferred.

With regard to the radicals R1, R2, R3,
R4 and R5, the invention relates more particularly to those selected from a hydrogen atom, an -OH group, a -OCH3 group, a -OR "'group where R"' represents an optionally mono or multi-acylated ose of which the acylating group is itself optionally substituted with an ose.

Advantageously, it is preferred in formula (I)
the radicals R1 and R3 chosen from a hydrogen atom, a -OH group, a -OCH3 group, a -OR "'group, where R"' represents an optionally mono- or pluriacylated dyose whose acylating group is itself possibly substituted by an ose,
the radicals R2 and R5 representing an -OH group,
the radicals R4 chosen from an -OH group, a -OCH3 group, a -OR "'group, where R""represents an optionally mono- or multi-acylated monosaccharide, the acylating group of which is itself optionally substituted by an ose.

 Among the groups -OR "', there may be mentioned for example those in which R"' is a saccharide chosen from glucose, galactose, arabinose, rutinose, xylose, optionally acylated by acetic acid, coumaric, caffeic, malic, preferentially in position 6.

The invention specifically relates to the anthocyanin dyes of formula (I) which are monoglucosides, and in particular the dyes corresponding to the following formula

<tb><SEP> R1
<tb><SEP> OH <SEP> + R3
<tb> 0 <SEP> + <SEP> I
<tb><SEP> o
<tb><SEP> N <SEP> R3
<tb><SEP> 0-Gkicosis
<tb><SEP> o
<tb><SEP> (He)
<tb><SEP> R7 <SEP><SEP> X <SEP> R6
<tb><SEP> OH
<Tb>
in which the radicals R1, R3, R6 and R7, which are identical or different, represent a hydrogen atom, an -OH group or a -OCH3 group.

 Two of the dyes of the invention of formula (I) have been demonstrated by the inventors for the first time during the liquid chromatography (HPLC) analysis of a wine. The singularity of their Visible Absorption Spectrum, obtained with a diode array detector, prompted us to go further in the characterization of one of these products. After isolation and purification by HPLC, the compound was analyzed by NMR spectroscopy and mass spectrometry. The results of these analyzes allowed us to establish a structure that derives from malvidol 3- (6-pcoumaroyl) -glucoside, a pigment found in grapes and wine. The alkaline hydrolysis of the characterized compound produced the second pigment initially detected and coumaric acid, suggesting that it is probably the same derivative, formed this time from 3glucoside malvidol, major anthocyanin grapes and wine; The mechanism that the inventors have envisaged to explain the formation of the two compounds presupposes a cyclization (at 6 centers) between 4-vinylphenol and anthocyanin. Vinylphenol in wine can be derived from the decarboxylation of p-coumaric acid by yeasts.

To confirm this reaction process,
Inventors have carried out the synthesis of the vinylphenol derivative of malvidol 3-glucoside. Anthocyanin (7.9 mg), isolated from grape berry skins and purified by
HPLC, was solubilized in 2 ml of a hydrochloric acid solution (10 -3 M expex). To this solution (7.5 mM), was added 0.05 ml of a solution of vinylphenol (10% in propylene glycol), which corresponds to a molar ratio of 2.9 moles of vinylphenol per 1 mole of anthocyanin. The reaction mixture was placed in a bath thermostated at 300C and kept stirring for the duration of the reaction.

The evolution of the medium was followed by HPLC. After 4 hours of reaction, anthocyanin was quantitatively converted to its vinylphenol derivative. Its retention time and its W-visible absorption spectrum recorded in a diode array are identical to those of the product detected in the wine. The synthesized product was thus purified by HPLC and analyzed by NMR spectroscopy and mass spectrometry. The results confirm the first structure, namely that it is the product formed by cyclization between the vinyl double bond of phenol, the hydroxyl at position 5 and the carbocation in position 4 of anthocyanin whose molecular mass is 609.

The invention therefore particularly relates to the anthocyanin dye derived from malvidol 3glucoside corresponding to the following formula

<tb><SEP> OCH3
<tb><SEP> OH
<tb> OH <SEP> O + N <SEP> oeH3
<tb><SEP><<SEP> O <SEP> - <SEP> GhoBe
<tb><SEP> O
<tb><SEP> (IV)
<tb><SEP> OH
<Tb>
Figure 1 shows the UV visible spectra of malvidol 3-glucoside in (A) and its vinylphenol adduct in (B). It is observed that in comparison with the 3-glucoside spectrum of malvidol, the ratio of the absorbance maxima between the visible and the W has substantially increased for the vinylphenol derivative.

This result can be explained by the increase in chromophore size of this new anthocyanin dye. In addition, it is interesting to note, as shown in FIG. 2, that one of its resonance forms is another anthocyanin of the pelargonidol type
This form seems moreover the most stable, if one refers to the maximum of absorbance of the visible band, for which one observes a slip towards the shortest wavelengths (k = 504 nm, characteristic of pelargonidol with place of k = 531 nm for malvidol).

 This explains the more orange coloring of the vinylphenol derivative of formula (II). Given these results, it is possible, by the play of substituents both in the pigment and vinylphenol, to obtain a range of colors from purple to orange.

 Moreover, by simultaneously blocking the positions 4 and 5 of the anthocyanin, the cyclization confers a greater stability to the new compound.

 These results therefore open the way to obtaining the series of new anthocyanin dyes of formula (I).

 The invention also relates to the processes for the preparation of the preceding anthocyanic dyes.

A first method for preparing an anthocyanin dye or a mixture of anthocyanin dyes according to the invention is characterized in that one or more anthocyanin molecules or a global extract of various anthocyanins are reacted in acidic medium. in one or more plants or in one or more by-products of transformation of said plants, with an excess of one or more compounds corresponding to formula (III) below, or a crude plant extract containing said compounds

 wherein R and R 'have the same meaning as in formula I, then collecting reaction medium and optionally purifying said anthocyanin dye by any suitable means.

 In the above process, it is preferred to use compounds of formula (III) in which the radical R represents a mono-, di- or triphenol group optionally substituted with one or more -OCH 3 groups, and those where R 'represents a hydrogen atom or a -COOH group, and in the latter case, the compound of formula (III) is advantageously a hydroxycinnamic acid such as para-coumaric acid or vinylphenol, or a derivative thereof bearing at least one substituent on the phenol group as indicated above in the corresponding dyes of formula (I).

A second process for preparing an anthocyanin dye or a mixture of anthocyanin dyes of the invention is characterized in that
a hydroxycinnamic acid such as para-coumaric acid and its derivatives whose phenol group carries at least one substituent, or a plant extract containing said acids, is subjected to the action of a preparation or a micro an organism comprising a decarboxylase activity, under conditions allowing the formation of vinylphenol and / or one or more vinylphenol derivatives whose phenol group carries at least one substituent, and
in that one or more anthocyanin molecules or a global extract of various anthocyanins contained in one or more plants or in one or more transformation by-products of said plants are added to the preceding fermentation medium, so as to make reacting said vinylphenol and / or its derivative (s) as and when they are formed with the anthocyanins and obtaining in the reaction medium said anthocyanin dye or said mixture of anthocyanin dyes.

Advantageously, the foregoing processes are carried out with one or more anthocyanin molecules or a global extract of various anthocyanins contained in one or more plants or in one or more transformation by-products of said plants, corresponding to the following formula

in which the radicals R1, R2, R3, R4 and
R5 have the same meaning as in formula (I).

 Particularly preferred in the above process is a global anthocyanin extract contained in grapes or wine or grape pomace.

 Another property of these pigments is their more hydrophobic character than the original anthocyanins, allowing their use in emulsions or purely lipidic media. All of the properties and advantages of anthocyanin dyes of the invention make it possible to envisage their use for coloring cosmetic, pharmaceutical and food compositions.

 The invention therefore also relates to colored cosmetic or pharmacological compositions containing at least one preceding anthocyanin dye, or an anthocyanin dye or a mixture of anthocyanin dyes prepared by one of the above processes.

 The invention also relates to colored food compositions comprising at least one staple food and at least one preceding anthocyanin dye, or an anthocyanin dye or a mixture of anthocyanin dyes prepared by one of the preceding methods.

 The invention finally relates to the use of a preceding anthocyanin dye or a mixture of anthocyanin dyes, or an anthocyanin dye or a mixture of anthocyanin dyes prepared by one of the preceding processes, for coloring an cosmetic composition, a pharmaceutical composition or a food composition.

 Other advantages and features of the invention will appear in the description which follows and which refers to the figures in the appendix and mainly relates to the coloring properties of the new anthocyanin dyes of the invention.

 I - Materials and methods.

 A solution of an anthocyanic grape extract at 0.97 g / l (ie a molar concentration of approximately 1.83 mM, calculated from the molar mass of malvidol 3-glucoside, the predominant anthocyanin of the extract) was prepared in citrate phosphate pH 3 buffer.

 The solutions containing the anthocyanins and the vinylphenol derivatives were diluted on the one hand (drinks model) by the solutions with pH3 (HCl 10-3 M and citrate-phosphate buffer), on the other hand (model other products) by citrate-phosphate buffer at pH 5. In the latter case, the pH was adjusted by addition of sodium hydroxide (F1 10 in 1.5 ml of sample). The values of the tristimulus coordinates and the absorbances were measured on these solutions.

 Two additional samples were prepared by dilution to one-fifth of the pH3 dye preparations in a commercial plain yoghurt to test the behavior (color, stability, appearance of the resulting solution, solubility in the medium) of both types of pigments in an emulsion type model. We checked that the pH of the yogurt (4.25) was not modified by the addition of the pigment solutions.

 The thermal stability tests were carried out on the aqueous solutions in a 550C water bath on tubes kept in the light or in the dark.

 Additional samples were prepared to test the stability of the dye preparations with respect to the sulphites, by adding 20 Al of a solution of sodium metabisulphite at 250 μl -1 to 1.5 ml of each solution. The final concentration of sulfur dioxide thus obtained is 2.5 g / l.

 The color of the solutions and its evolution during the various stability tests performed was evaluated by measuring the tristimulus coordinates carried out using a colorimeter marketed by Minolta under the reference CR 200. The absorbance at 518 nm (maximum Absorbance of the anthocyanic solution) and 594 nm (maximum absorbance of the vinylphenol derivative solution) was also measured on each of the aqueous solutions.

The composition of the solutions was analyzed by reverse phase HPLC using a system of the type
Waters including a U6K manual injector, a gradient programmer, two M690 pumps and a M990 diode array detector. The column is a column of the Company
Lichrospher RP-18 (5Rm) (250x4mm) protected by a filled precolumn of the same phase (Merck Company, Darmstadt,
Germany).

Anthocyanins and their vinylphenol adducts were eluted under the following conditions - solvent A: formic acid / water (2/98, v); solvent B: acetonitrile, water, formic acid (80/18/2, v); flow rate: 1 ml per minute; temperature of the column 300C; - gradient described in Table 1 below
Table 1

<tb> Time <SEP> (minutes) <SEP>% <SEP> A <SEP>% <SEP> B
<tb><SEP> 0 <SEP> 95 <SEP> 5
<tb><SEP> 40 <SEP> 70 <SEP> 30
<tb><SEP> 60 <SEP> 50 <SEP> 50
<tb><SEP> 70 <SEP> 80 <SEP> 20
<Tb>
II - Study of the coloring properties of the anthocyanin dye of formula (IV)

 The study of the coloring properties and the stability was carried out on a mixture of vinylphenol derivatives obtained by synthesis from a global extract of anthocyanins monoglucosides grapes and vinylphenol, under the same conditions as those described above.

This material is an easily accessible source at the industrial level.

The composition of the anthocyanin extract, containing exclusively the monoglucoside forms, is given in Table 2 below.
Table 2

<tb> Anthoc <SEP> ane <SEP> Concentration <SEP> relative <SEP> (%)
<tb><SEP> Y
<tb> 3-glucoside <SEP> of <SEP> delphinidol <SEP> 24.4
<tb> 3- <SEP> lucoside <SEP> of <SEP> c <SEP> anidol <SEP> 5.7
<tb><SEP> g <SEP> v
<tb> 3-glucoside <SEP> of <SEP> petudinol <SEP> 16.5
<tb> 3-glucoside <SEP> of <SEP> peonidol <SEP> 12,9
<tb> 3-glucoside <SEP> of <SEP> mavidol <SEP> 40.1
<Tb>
All anthocyanins were converted to vinyl phenol adducts by incubation of this extract in the presence of 5 mM vinyl phenol. The chromatograms of the anthocyanin extract and the solution containing the vinylphenol derivatives are given in Figure 3. The residual vinyl phenol was then removed by entrainment with argon in order to avoid any copigmentation reactions between the pigments and the vinylphenol. , likely to change the color.

 FIG. 3 represents the chromatographic profiles in (A) of the anthocyanin extract and in (B) the solution of new pigments at 510 nm. Peaks 1, 2, 3, 4 and 5 represent delphinidol 3-glucoside, cyanidol 3-glucoside, petudinol 3-glucoside, peonidol 3-glucoside and mavidol 3-glucoside, respectively. peaks 1 ', 2', 3 ', 4' and 5 'respectively represent the corresponding vinylphenol adducts.

 1) Evaluation of the color and comparison with that of anthocvanes in aqueous solutions at DH 3 and DH 5.

 The color can be evaluated by measuring the tristimular coordinates L * a * b *, officially defined (2). . These coordinates are obtained by measuring the reflectance of an opaque sample or transmittance through a transparent sample using a colorimeter.

The L * (luminance) coordinate is denoted from 0 to 100 from dark to light. the coordinates a * and b *, representing respectively the red (green for the negative values) and yellow (blue for the negative values) components of the color, can be used directly or converted to a hue angle, denoted theta (0 = arctg b * / a *) (6). The saturation measurement that accounts for the intensity of the coloration is calculated according to the formula (a2 +) 12.

 The color of the solution of vinylphenol derivatives which is presented as an orange dye was compared with that of an anthocyanin solution.

The tristimulus coordinates measured for each of the solutions at pH 3 and pH 5 are shown in Figure 4, as well as the values calculated for the hue angle (6). At pH 3 (beverage model), the anthocyanin and vinylphenol derivative solutions have similar tristimulus coordinates, with the exception of the upper b * value in the solution of the derivatives, which indicates a more orange hue ( the anthocyanin solution is 420 to 280. When the pH is adjusted to 5 (model dairy, meat), the anthocyanin solution becomes lighter (increased
L *). The a * and b * values decrease in both solutions, which indicates a deterioration of the red or orange color. Note that this degradation is much more pronounced in the anthocyanin solution, which evolves to a more purplish shade, as evidenced by the value of the hue angle, close to zero. This staining is that of the quinone base form of anthocyanins, which becomes predominant when the pH increases (4).

 FIG. 4 represents the tristimulus coordinates L * a * b * and tint angle (6) of the solutions of anthocyanins and vinylphenol adducts in aqueous solutions at pH 3 and pH 5.

 2) Resistance to fading by sulphites.

 The addition of sulphites leads to an instant discoloration of the anthocyanin solutions at pH 3 and pH 5 (saturation close to 0) while the solutions of vinylphenol derivatives remain colored despite this treatment (saturation 60). The saturation values measured after sulphiting change little over time.

 FIG. 5 represents the evolution of the coloring intensity (saturation) of the anthocyanin solutions (An) and of their vinylphenol derivatives (Vi) after sulphiting.

 This maintenance of the coloring intensity is all the more appreciable that it is achieved without changing the shade of the solution as shown in Figure 6 which shows the influence of sulfiting on the color (tint angle) of the solutions. This phenomenon is certainly due to the protection of the 4-position of the flavylium ring by the addition of the vinylphenol group in the new compounds described.

This is all the more interesting as sulphite treatments are a common process in the fruit industry, the use of natural dyes resistant to this treatment would retain the color.

 3) Thermal stability in acute solution.

 The thermal stability was tested in parallel on the anthocyanin solutions and the pigment solutions formed by reaction with vinylphenol, at pH 3 and pH 5. The incubations were carried out at 550 ° C. in the presence of air and light. known conditions to promote the degradation of anthocyanins.

 a) A sH 3 (drink model).

 The thermal degradation of the solutions at pH 3 was studied in parallel in 10-3 M hydrochloric acid and in a citrate buffer, known to improve the stability of the anthocyanin dyes (1).

 The determination of each component by HPLC confirms the better stability of all vinylphenol adducts relative to the corresponding anthocyanins. After 7 days of incubation, the anthocyanin solution contains only 2% of the initial malvidol glucoside concentration while the solution of the vinylphenol derivatives still contains 72% of the vinylphenol derivative of malvidol glucoside (39% in the buffer). citrate) initially present as shown in Figure 7, which represents the kinetics of degradation of 3-glucoside of malvidol and its vinylphenol adduct in solutions at pH 3 maintained at 55 ° C. The vinylphenol derivative of delphinidol, although much more brittle, is also more stable than its precursor (47% of the initial concentration after 7 days at 550C against only 0.3% for delphinidol glucoside in hydrochloric acid.) Losses vinylphenol slightly higher in the citrate buffer are attributable to their progressive insolubilization in this medium.

 The evolution of the absorbance in the visible of each of the solutions at pH 3 shown in Figure 8 below confirms the stability of vinylphenol adducts much higher than that of anthocyanins. Indeed, after seven days of incubation in 10-3M hydrochloric acid, the solution of the new pigments retains nearly 50% of its initial absorbance at k max of the sample while the anthocyanin solution has lost 97% of its absorbance in the visible. The color of each of the solutions is more intense in the citrate buffer which exerts a protective effect on the color, although the molecules are strongly degraded.

 Figure 8 shows the evolution of the absorbance of anthocyanin solutions (518 nm) and vinylphenol derivatives (494 nm) maintained at 550C.

 The differences in the shades between the anthocyanin solution and that of vinylphenol derivatives at pH 3 are conserved over time as shown in FIG. 9, which represents the evolution of the tint angle of the anthocyanin and vinylphenol derivative solutions. maintained at 550C.

 The values of the tint angles obtained show that the solution of anthocyanins undergoes discoloration in the red, thus tending towards a color of which the yellow component becomes preponderant. The vinylphenol derivative solution retains, on the contrary, an orange tint identical to that observed before heating, thus confirming that these compounds are stable both in buffered medium and in non-buffered acid medium.

 b) A DH 5 (model other products).

 The assays of the compounds by HPLC in the solutions at pH 5 placed at 550C shown in FIG. 10 show that the anthocyanin solution is strongly degraded (2% remaining as of the second day) while the solution of vinylphenol derivatives is clearly more stable. . The loss of the compounds observed on the second day is attributable to their precipitation in an aqueous medium pH 5. This phenomenon reduces the difference in stability between the two solutions examined and tends to reduce the intensity of the coloration.

 Figure 10 shows the degradation kinetics of 3-glucoside of malvidol and its vinylphenol adduct in solutions at pH 5 maintained at 550C.

 Over time, the shade of the anthocyanin solution is strongly modified with an increase of the yellow component and a decrease of the red component over time, while the vinylphenol derivatives have a shade similar to that observed initially as shown in FIG. Figure 11, which shows the evolution of the tint angle of anthocyanins solutions and vinylphenol derivatives maintained at 550C.

 4) Solubility in the middle of your emulsion (vaourt).

 Precipitation phenomena observed in aqueous media and more particularly at pH 5, are non-existent in mixed media comprising a "lipid fraction"; this observation makes it possible to envisage their use in various food and cosmetic or pharmaceutical products having this composition, for example dairy products.

 The yoghurt-type milk media used in the experiment have a pH of approximately 4.25 corresponding to the pH of the majority of products available on the market. The addition of anthocyanins (dilution identical to that used for aqueous media) to yogurt leads to a coloration whose shade has a blue-pink trend whereas, as expected, the vinylphenol derivatives produce an orange coloring as shown in FIG. represents the evolution of the tint angle of yogurt + anthocyanins and yoghurt + vinylphenol derivatives. The color intensities shown in FIG. 13 are totally different, demonstrating the markedly higher coloring power of the vinylphenol solution. Moreover, this coloration is maintained over time, a decrease being observed for anthocyanins despite the preservation of 40C samples (regulatory conditions for the preservation of these products).

 Figure 13 shows the change in staining intensity of yogurts + anthocyanins (An) and yoghurts + derivatives vinylphenol (Vi).

References
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Tachini M., Nicolas J., 1992: Report of the Days
International Studies Group Polyphenols, 16 (2), 5255.

 2) Bakker J., Bridle P. and Timberlake C. F., 1986: Tristimulus measurements (CIELAB 76) of port wine color. Vitis, 25, 68.

 3) Fog R., 1982: Chemical structures of anthocyanins as food colors.

4) Fog D., Dubois JE 1977
Mechanism of structural transformations of anthocyanins in acidic media. J. Med. Chem. Soc. 99 (5) 1359-1364.

 5) Francis F.J., 1989: Food colorants anthocyanins, Crit. Rev. Food Sci. Nutr. 28 (4), 273.

 6) Francis F.J., 1975: The origin of tan-b / a, J. Food Sci.40, 412.

 7) Iacobucci G.A. and Sweeney J.G., 1983: The chemistry of anthocyanins, anthocyanins and related salts.

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Prospective Food Colors. Current Sci. 64 (8), 575.

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Claims (18)

1) Anthocyanin dye of formula

 the radical R 'represents an essentially electron-withdrawing electron-attracting group advantageously chosen from a hydrogen atom, a -OH group, a -COOH group, a -COH group, a -CH 2 OH group or a -COOR "-group where R" represents a branched or unsubstituted alkyl group of 2 to 5 carbons optionally substituted with one or more -OH, -COOH, -COH groups.  the radical R represents a substantially electron-donated, preferably aliphatic, alicyclic, aromatic or saturated or unsaturated, optionally substituted carbon donor electron group, and  the radicals R 1, R 2, R 3, R 4 and R 5 are chosen from the groups usually encountered on the flavylium ring of anthocyanins or equivalent groups,  in which  2) anthocyanin dye according to claim 1, characterized in that in formula I, the radical R represents a phenyl radical substituted with one or more -OH group, -OCH3, alkyl or heteroalkyl, -SH, -NO, -SO3 H , -NH2, -OR "'where R"' represents an optionally mono- or multi-acylated monosaccharide, the acylating group of which is itself optionally substituted by an ose.  3) anthocyanin dye according to claim 2, characterized in that in formula I, the radical R is a mono, di or triphenol group optionally substituted with one or more -OCH3 groups.  4) anthocyanin dye according to any one of claims 1 to 3, characterized in that in formula (I), the radicals R1, R2, R3, R4 and R5 are chosen from a hydrogen atom, a group -OH , a group -OCH3, a group -OR "'where R"' represents an optionally mono- or multi-acylated monosaccharide, the acylating group of which is itself optionally substituted by an ose.  5) anthocyanin dye according to claim 4, characterized in that in formula I,  the radicals R1 and R3 are chosen from a hydrogen atom, a -OH group, a -OCH3 group, a -OR "'group where R"' represents an optionally mono- or pluriacylated dyose whose acylating group is itself possibly substituted by an ose,  the radicals R2 and R5 represent an -OH group,  the radical R4 is chosen from a group -OH, a group -OCH3, a group -OR "'where R"' represents an optionally mono- or multi-acylated monosaccharide whose acylating group is itself optionally substituted by an ose.  6) anthocyanin dye according to any one of claims 4 and 5, characterized in that in the group -OR "', R"' is an ose selected from glucose, galactose, arabinose, rutinose, xylose optionally acylated with acetic acid, p-coumaric acid, caffeic acid, malic acid, preferentially in position 6.  7) An anthocyanin dye of formula I which is a monoglucoside.  8) anthocyanin dye corresponding to the following formula

 in which R1, R3, R6 and R7, which are identical or different, represent a hydrogen atom, an -OH group or a -OCH3 group. <Tb> <tb> <SEP> OH <tb> <SEP> R7 <SEP> <SEP> R6 <tb> <SEP> R7 <SEP> R6 <tb> <SEP> (He) <tb> <SEP> O <tb> <SEP> O-Glucose <tb> OH <SEP> <<SEP> <SEP> R3 <tb> <SEP> OH <tb> <SEP> R1  9) Process for the preparation of an anthocyanin dye or a mixture of anthocyanin dyes, characterized in that one or more anthocyanin molecules or a global extract of various anthocyanins contained in one or more plants or in one or more by-products of transformation of said plants, with an excess of one or more compounds corresponding to formula (III) below

 in which the radicals R and R 'have the same meaning as in formula (I), then that the reaction medium is collected and optionally purifies said anthocyanin dye by any appropriate means.  10) Process according to claim 9, characterized in that in formula (III), the radical R represents a mono, di or triphenol group optionally substituted with one or more -OCH3 groups.  11) Process according to any one of claims 9 and 10, characterized in that in the compound of formula (III), the radical R 'represents a hydrogen atom or a -COOH group.  12) Process according to any one of claims 9 to 11, characterized in that the compound of formula (III) is a hydroxycinnamic acid such as para-coumaric acid or vinylphenol, or a derivative thereof at minus one substituent on the phenol group.  13) A method for preparing an anthocyanin dye or a mixture of anthocyanin dyes, characterized in that one or more hydroxycinnamic acids such as para-coumaric acid and its derivatives bearing at least one substituent on the phenol group, or a plant extract containing said acids, in the action of a preparation or a microorganism having a decarboxylase activity, under conditions permitting the formation of vinylphenol and / or one or more vinylphenol derivatives wherein the phenol group carries at least one substituent, and that one or more anthocyanin molecules or a global extract of various anthocyanins contained in one or more plants or in one or more sub-bases is added to the preceding fermentation medium. transformation products of said plants, so as to react said vinylphenol and / or its derivative (s) as and when formed with anthocyanins and o recovering said anthocyanin dye or said mixture of anthocyanin dyes in the reaction medium.  14) Process according to any one of Claims 9 to 13, characterized in that one or more anthocyanin molecules corresponding to the following formula (V) are used.

R5 have the same meaning as in formula (I).  in which the radicals R1, R2, R3, R4 and  15) Process according to any one of claims 9 to 14, characterized in that one uses a global anthocyanin extract contained in reason, wine or grape marc.  16) A colored cosmetic or pharmaceutical composition characterized in that it contains at least one anthocyanin dye according to any one of claims 1 to 8, or an anthocyanin dye or a mixture of anthocyanin dyes prepared by a process according to any one of Claims 9 to 15.  17) A colored food composition characterized in that it comprises at least one staple food and at least one anthocyanin dye according to any one of claims 1 to 8, or an anthocyanin dye or a mixture of anthocyanin dyes prepared by a process according to any one of claims 9 to 15.  18) Use of an anthocyanin dye or a mixture of anthocyanin dyes as claimed in any one of claims 1 to 8, or an anthocyanin dye or a mixture of anthocyanin dyes prepared by a process according to any one of claims 9 to 15, for coloring a cosmetic composition, a pharmaceutical composition or a food composition.