WO2019105649A1

WO2019105649A1 - Antimicrobial mixture containing 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one and an essential oil, and cosmetic composition containing same

Info

Publication number: WO2019105649A1
Application number: PCT/EP2018/078564
Authority: WO
Inventors: Géraldine Lerebour; Catherine Marion; Sylvie Cupferman
Original assignee: L'oreal
Priority date: 2017-12-01
Filing date: 2018-10-18
Publication date: 2019-06-06
Also published as: FR3074404A1; FR3074404B1

Abstract

The invention relates to an antimicrobial mixture containing 4-(3-ethoxy-4-hydroxy- phenyl)butan-2-one and an essential oil chosen from rosemary, eucalyptus, Greek oregano, geranium, clove or lemongrass essential oils, and also a cosmetic composition containing such a mixture. Application to caring for, making up and cleansing keratin materials.

Description

Antimicrobial mixture containing 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one and an essential oil, and cosmetic composition containing same

The present invention relates to an antimicrobial mixture containing 4-(3-ethoxy-4-hydroxy- phenyl)butan-2-one and a particular essential oil, and also to a cosmetic composition con- taining such a mixture.

4-(3-Ethoxy-4-hydroxyphenyl)butan-2-one (ketone compound) is a beneficial substance as a preserving agent for cosmetic compositions, for protecting the compositions against mi- crobial contamination, as described in the application WO 201 1/039445.

However, it is desirable to be able to incorporate said ketone compound in reduced con- centration in compositions, especially cosmetic or dermatological compositions, while at the same time maintaining good antimicrobial preservation performance. Combinations of the ketone compound with other compounds that have antimicrobial efficacy are thus sought for this purpose.

The inventors have discovered, unexpectedly, that the combination of 4-(3-ethoxy-4-hy- droxyphenyl)butan-2-one with an essential oil chosen from rosemary, eucalyptus, Greek oregano, geranium, clove or lemongrass essential oils makes it possible to obtain an anti- microbial mixture having synergistic antimicrobial activity, in particular on moulds, especially on Aspergillus niger, and on yeasts, in particular on Candida albicans. The results of Ex- ample 1 described below show the synergistic antimicrobial activity obtained with the mini- mum inhibitory concentration (MIC) measurements taken with several mixtures. The anti- microbial activity is considered as being synergistic when the antimicrobial mixture makes it possible to obtain a percentage of strain growth of less than or equal to 20%.

Application FR-A-2962328 describes a cosmetic composition for treating body odour asso- ciated with human perspiration, comprising a 2-alkoxy-4-alkyl ketone phenol compound and an essential oil.

Application FR-A-2962333 describes a cosmetic composition for treating oily skin, compris- ing a 2-alkoxy-4-alkyl ketone phenol compound and an essential oil.

These documents do not specifically describe an antimicrobial mixture constituted by the combination of 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one with an essential oil chosen from those mentioned above, nor do they suggest that such a mixture has synergistic antimicro- bial activity on moulds, especially on Aspergillus niger, and on yeasts, in particular on Can dida albicans. More precisely, a subject of the invention is an antimicrobial mixture comprising, or consti- tuted by (or consisting of), 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one and an essential oil chosen from rosemary, eucalyptus, Greek oregano, geranium, clove or lemongrass essen- tial oils.

A subject of the invention is also a composition, especially a cosmetic composition, corn- prising, in a physiologically acceptable medium, said mixture described previously.

A further subject of the invention is a process for the non-therapeutic cosmetic treatment of keratin materials, comprising the application to the keratin materials of a composition as described previously. The process may be a cosmetic process for caring for or making up or cleansing keratin materials.

4-(3-Ethoxy-4-hydroxyphenyl)butan-2-one is a compound of formula:

The essential oil present in the antimicrobial mixture according to the invention is chosen from rosemary, eucalyptus, Greek oregano, geranium, clove and lemongrass essential oils.

Essential oils differ from plant oils by the fact that they cannot be decomposed by saponifi- cation into glycerol and fatty acid soap. Moreover, they are volatile.

According to the definition given in international standard ISO 9235 and adopted by the Commission of the European Pharmacopoeia, an essential oil is a product generally of complex composition, obtained from a botanically defined plant raw material, either by steam entrainment, or by dry distillation, or by extraction using liquid or gaseous solvents, or via an appropriate mechanical process without heating (cold pressing). The essential oil is usually separated from the aqueous phase via a physical process that does not result in any significant change in the composition. These essential oils may also be prepared by synthesis.

The essential oil used according to the invention may be obtained from any plant material derived from the whole plant or from any part of said plant, for instance the leaves, stems, flowers, petals, seeds, fruits, buds, roots, plant branches and/or whole plants. The essential oil used according to the invention may be prepared according to the tech- niques mentioned above and will preferably be obtained according to the standard tech- nique of steam entrainment.

Steam entrainment corresponds to vaporization, in the presence of steam, of a sparingly water-miscible substance. The raw material is placed in contact with boiling water or steam in a stillpot. The steam entrains the essential oil vapour, which is condensed in the conden- ser and recovered as a liquid phase in a Florentine vase (or essence jar), where the essen- tial oil is separated from the water by settling. The aqueous distillate that remains after the steam entrainment, once the separation of the essential oil has been performed, is known as the“aromatic water” or“hydrolate” or“distilled floral water”.

In the following description, the contents indicated for the components of the essential oils are given relative to the total weight of the essential oil in question.

An essential oil of rosemary ( Rosmarinum officinalis cineole chemotype or Rosmarinum officinalis‘ pyramidalis that is suitable for the invention may be obtained by extraction by steam distillation of the leaves.

Rosemary essential oil especially has the INCI name: ROSMARINUS OFFICINALIS LEAF OIL.

According to a preferred embodiment, the rosemary essential oil according to the in vention may be an essential oil of rosemary cineole chemotype of north African type. The rosemary essential oil comprises, as main components, para-cymene, 1 ,8-cineole, a- pinene, camphor, b-pinene.

An essential oil of rosemary cineole chemotype of north African type advantageously comprises a mixture of:

para-cymene, especially in an amount of 0.5 to 2.5%,

1 ,8-cineole, especially in an amount of 35 to 55%,

a-pinene, especially in an amount of 9 to 14%,

camphor, especially in an amount of 5 to 15%,

b-pinene, especially in an amount of 4 to 9%,

camphene, especially in an amount of 2.5 to 6%,

d-limonene, especially in an amount of 1.5 to 4%,

b-caryophyllene, especially in an amount of 1 to 6%,

borneol, especially in an amount of 1 to 5%,

a-terpineol, especially in an amount of 1 to 2.5%,

myrcene, especially in an amount of 1 to 2%,

bornyl acetate, especially in an amount of 0.1 to 1.6%. Use may be made, for example, of the rosemary essential oil sold under the name HE ROMARIN A CINEOLE BIO by Elixens. An essential oil of eucalyptus ( Eucalyptus radiata Sieb.) that is suitable for the invention may be obtained by extraction by steam distillation from the leaves.

Eucalyptus essential oil especially has the INCI name: EUCALYPTUS RADIATA LEAF OIL.

The eucalyptus essential oil comprises, as main components, 1 ,8-cineole and a-terpineol. In particular, a eucalyptus essential oil advantageously comprises a mixture of:

1 ,8-cineole, especially in an amount of 60 to 75%,

a-terpineol, especially in an amount of 4 to 1 1 %,

limonene, especially in an amount of 2.5 to 8%. Use may be made, for example, of the eucalyptus essential oil sold under the name HE EUCALYPTUS RADIATA BIO by Elixens.

An essential oil of Greek oregano ( Origanum Heracleoticum) that is suitable for the in vention may be obtained by extraction of the flowers by complete distillation by steam entrainment.

Greek oregano essential oil especially has the INCI name: ORIGANUM HERACLEOTICUM FLOWER OIL.

Greek oregano essential oil comprises, as main components, carvacrol, para-cymene, gamma-terpinene and thymol.

In particular, a Greek oregano essential oil advantageously comprises a mixture of: carvacrol, especially in an amount of 45 to 65%,

para-cymene, especially in an amount of 6 to 25%,

gamma-terpinene, especially in an amount of 7 to 18%,

thymol, especially in an amount of 0.001 to 10%,

myrcene, especially in an amount of 1 to 4%,

alpha-terpinene, especially in an amount of 0.1 to 3%,

alpha-pinene, especially in an amount of 0.3 to 2%,

alpha-thujene, especially in an amount of 0.5 to 3%,

b-caryophyllene, especially in an amount of 0 to 4%,

linalool, especially in an amount of 0 to 2%,

terpinen-4-ol, especially in an amount of 0 to 2%. Use may be made, for example, of the Greek oregano essential oil sold under the name HE ORIGAN VERT BIO SICA by Elixens. The essential oil of geranium ( Pelargonium roseum asperum CV North Africa - Egypt) that is suitable for the invention may be obtained by extraction from the leaves, stems and flowers by complete distillation by steam entrainment.

Geranium essential oil especially has the INCI name: PELARGONIUM GRAVEOLENS FLOWER OIL.

Geranium essential oil comprises, as main components, citronellol, geraniol, citronellyl for- mate, linalool, geranyl formate, eudesmol and isomenthone.

In particular, a geranium essential oil advantageously comprises a mixture of:

citronellol, especially in an amount of 25 to 36%,

geraniol, especially in an amount of 10 to 18%,

linalool, especially in an amount of 4 to 8.5%,

citronellyl formate, especially in an amount of 5 to 8%,

isomenthone, especially in an amount of 4 to 8%,

gamma-10 epi-eudesmol (or eudesmol), especially in an amount of 3 to 6%, geranyl formate, especially in an amount of 2 to 7%,

geranyl tiglate, especially in an amount of 0.9 to 2%,

cis-rose oxide, especially in an amount of 0.7 to 1.5%,

geranyl butyrate, especially in an amount of 0.7 to 2%,

phenylethyl tiglate, especially in an amount of 0.5 to 1.2%,

trans-rose oxide, especially in an amount of 0.3 to 0.6%,

alpha-terpineol, especially in an amount of 0.3 to 0.6%.

An example of a geranium essential oil according to the present invention that may be men- tioned is that sold by Elixens under the name HE GERANIUM EGYPTE BIO.

An essential oil of clove ( Eugenia caryophyllus) that is suitable for the invention may be obtained by extraction by steam distillation of the clove (floral bud).

Clove essential oil especially has the INCI name: EUGENIA CARYOPHYLLUS FLOWER OIL.

Clove essential oil comprises, as main components, eugenol, eugenyl acetate and b-cary- ophyllene.

In particular, a clove essential oil may comprise: eugenol, especially in an amount of 75-87%,

eugenyl acetate, especially in an amount of 8-15%,

b-caryophyllene, especially in an amount of 2-8%.

Use may be made, for example, of the clove essential oil sold under the name HE GIROFLE CLOU BIO by Elixens.

An essential oil of lemongrass ( Cymbopogon flexuosus or Cymbopogon citratus) that is suitable for the invention may be obtained by extraction by steam distillation of the leaves, preferentially harvested from November to May.

Lemongrass essential oil especially has the INCI name: CYMBOPOGON SCHOENANTHUS OIL.

The lemongrass essential oil comprises, as main components, geranial and neral.

In particular, an essential oil of lemongrass ( Cymbopogon flexuosus) advantageously comprises a mixture of:

geranial, especially in an amount of 35 to 47%,

neral, especially in an amount of 25 to 35%,

geraniol, especially in an amount of 1 .5 to 8%,

limonene, especially in an amount of 0.5 to 3.5%,

geranyl acetate, especially in an amount of 0.5 to 6%,

b-caryophyllene, especially in an amount of 0.2 to 3.5%,

methyl heptenone, especially in an amount of 0.1 to 2%.

Use may be made, for example, of the lemongrass essential oil sold under the name HE LEMONGRASS BIO by Elixens.

According to a first embodiment of the invention, rosemary essential oil (referred to as rose- mary EO) is used.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/rosemary EO weight ratio ranging from 0.35 to 1 .5, preferably ranging from 0.7 to 1.3. Such a mix- ture has synergistic antimicrobial activity on yeasts, especially on Candida albicans.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/rosemary EO weight ratio ranging from 0.1 to 0.4, preferably ranging from 0.2 to 0.3. Such a mixture has good synergistic antimicrobial activity on moulds, especially on Aspergillus niger. According to a second embodiment of the invention, eucalyptus essential oil (referred to as eucalyptus EO) is used.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/eucalyp- tus EO weight ratio ranging from 0.15 to 3, preferably ranging from 0.15 to 1 .5. Such a mixture has good synergistic antimicrobial activity on yeasts, especially on Candida albi cans.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/eucalyp- tus EO weight ratio ranging from 0.1 to 0.8, preferably ranging from 0.15 to 0.4 and prefer- entially ranging from 0.18 to 0.35. Such a mixture has good synergistic antimicrobial activ- ity on moulds, especially on Aspergillus niger.

According to a third embodiment of the invention, Greek oregano essential oil (referred to as Greek oregano EO) is used.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/Greek oregano EO weight ratio ranging from 3 to 15, preferably ranging from 3 to 8 and prefer- entially ranging from 4 to 6. Such a mixture has good synergistic antimicrobial activity on moulds, especially on Aspergillus niger.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/Greek oregano EO weight ratio ranging from 3 to 8, preferably ranging from 4 to 6. Such a mix- ture has good synergistic antimicrobial activity on yeasts, especially on Candida albicans.

According to a fourth embodiment of the invention, geranium essential oil (referred to as geranium EO) is used.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/geranium EO weight ratio ranging from 3 to 15, preferably ranging from 7 to 13. Such a mixture has good synergistic antimicrobial activity on yeasts, especially on Candida albicans.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/geranium EO weight ratio ranging from 1.5 to 4, preferably ranging from 2 to 3. Such a mixture has good synergistic antimicrobial activity on moulds, especially on Aspergillus niger.

According to a fifth embodiment of the invention, clove essential oil (referred to as clove EO) is used. The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/clove EO weight ratio ranging from 0.5 to 4, preferably ranging from 1 to 3 and preferentially ranging from 1.5 to 3. Such a mixture has good synergistic antimicrobial activity on yeasts, espe- dally on Candida albicans.

The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/clove EO weight ratio ranging from 2.4 to 4, preferably ranging from 2.45 to 3.5 and preferentially ranging from 2.45 to 3. Such a mixture has good synergistic antimicrobial activity on moulds, especially on Aspergillus niger.

According to a sixth embodiment of the invention, lemongrass essential oil (referred to as lemongrass EO) is used. The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2- one/lemongrass EO weight ratio ranging from 4 to 10, preferably ranging from 5 to 8.

Such a mixture has good synergistic antimicrobial activity on yeasts, especially on Can dida albicans. The antimicrobial mixture may have a 4-(3-ethoxy-4-hydroxyphenyl)butan-2- one/lemongrass EO weight ratio ranging from 30 to 150, preferably ranging from 30 to 70 and preferentially ranging from 40 to 60. Such a mixture has good synergistic antimicro- bial activity on moulds, especially on Aspergillus niger. The compound 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one may be present in the composi- tion according to the invention in an amount ranging from 0.01 % to 5% by weight relative to the total weight of the composition, preferably ranging from 0.01 % to 3% by weight, prefer- entially ranging from 0.01% to 2.5% by weight and more preferentially ranging from 0.01% to 2% by weight.

A subject of the invention is also a composition comprising, in a physiologically acceptable medium, the antimicrobial mixture described previously.

The term "physiologically acceptable medium" is intended to mean a medium that is com- patible with human keratin materials such as the skin, the scalp, the hair and the nails. Said medium may comprise one or more additional ingredients other than the ketone compound and said essential oil. The composition may comprise at least one additional ingredient chosen from water, oils, polyols having from 2 to 10 carbon atoms, gelling agents, surfactants, film-forming poly- mers, colorants, fragrances, fillers, UV-screening agents, plant extracts, cosmetic and der- matological active agents, and salts.

The composition according to the invention may comprise an aqueous phase.

The composition may comprise water, which may be present in an amount ranging from 5% to 90% by weight relative to the total weight of the composition, and preferably ranging from 35% to 75% by weight.

The composition may also comprise a polyol that is water-miscible at room temperature (25°C), especially chosen from polyols especially having from 2 to 10 carbon atoms, pref- erably having from 2 to 6 carbon atoms, such as glycerol, propylene glycol, 1 ,3-propanediol, butylene glycol, pentylene glycol, hexylene glycol, dipropylene glycol, diethylene glycol or diglycerol.

The compositions according to the invention may be in the form of oil-in-water (O/W) emul- sions, water-in-oil (W/O) emulsions or multiple emulsions (triple: W/O/W or O/W/O), oily solutions, oily gels, aqueous solutions, aqueous gels, or solid compositions. These compo- sitions are prepared according to the usual methods.

The compositions according to the invention may be more or less fluid and may have the appearance of a white or coloured cream, an ointment, a milk, a lotion, a serum, a paste or a foam. They may be optionally applied to the skin in aerosol form. They may also be in solid form, for example in the form of a stick or a compact powder.

The composition according to the invention may especially be in the form of:

- a makeup product, especially for making up the skin of the face, the body, or the lips or the eyelashes;

- an aftershave gel or lotion; a shaving product;

- a deodorant (stick, roll-on or aerosol);

- a hair-removing cream;

- a body hygiene composition such as a shower gel or a shampoo;

- a pharmaceutical composition;

- a solid composition such as a soap or a cleansing bar;

- an aerosol composition also comprising a pressurized propellant;

- a hair-setting lotion, a hair-styling cream or gel, a dyeing composition, a permanent-waving composition, a lotion or a gel for combatting hair loss, or a hair conditioner;

- a composition for caring for or cleansing the skin.

A subject of the invention is also a process for preparing a composition, especially a cosmetic or dermatological composition, comprising a step of mixing 4-(3-ethoxy-4- hydroxyphenyl)butan-2-one, the essential oil and one or more additional ingredients, especially cosmetic or dermatological ingredients, such as those described previously.

The invention is illustrated in greater detail in the example that follows. The amounts of the ingredients are expressed as weight percentages.

Example 1 : determination of the synergistic antimicrobial activity as MIC

The demonstration of a synergistic antimicrobial activity effect with a mixture of 4-(3-ethoxy- 4-hydroxyphenyl)butan-2-one (referred to as substance A) and essential oil (referred to as substance B) is performed by calculating the synergy index (or FIC index) according to the following formula:

FIC Index = (MICa with B/MICa) + (MICb with A/MICb) with:

MICa with B: minimum concentration of product A in the combination A + B which makes it possible to obtain an inhibitory effect.

MICb with A: minimum concentration of product B in the combination A + B which makes it possible to obtain the inhibitory effect.

MICa: minimum inhibitory concentration of product A alone.

MICb: minimum inhibitory concentration of product B alone.

This formula was described for the first time in the article by F.C. Kull, P.C. Eisman, H.D. Sylwestrowka, and R.L. Mayer, Applied Microbiology 9:538-541 , 1961.

For each compound tested alone, the MIC is considered as the first concentration which makes it possible to obtain a microbial growth percentage of less than or equal to 20%.

As regards the combinations tested, MICa with b and MICb with a are the respective con- centrations of A and of B in the combinations which make it possible to obtain a microbial growth percentage of less than or equal to 20%.

Interpretation of the FIC Index: When the FIC index value is less than or equal to 1 , it is considered that the combination of test compounds has a synergistic effect.

The summary of the results obtained is presented in the following tables.

The combinations of compounds A and B were tested on the following strains: Aspergillus niger and Candida albicans.

The microbial strain Aspergillus niger ATCC 6275, and a double-concentration Sabouraud broth liquid culture medium supplemented with polyoxyethylenated (20 EO) sorbitan mono- palmitate (Tween 40 from Croda) and Phytagel© BioReagent were used.

The microbial strain Candida albicans ATCC 10231 and a double-concentration Sabouraud broth liquid culture medium were used. (i.e. a mixture of 5 g of Phytagel + 0.6 g of Tween 40 + 60 g of Sabouraud broth).

A 96-well microplate and an incubation temperature of 32.5°C are used.

The incubation time of the microplate is:

- from 24 hours to 48 hours aerobically for Aspergillus niger,

- from 18 hours to 24 hours aerobically for Candida albicans.

Tests

For each compound:

A = 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one compound

B = essential oil with:

B1 = rosemary essential oil sold under the name HE ROMARIN A CINEOLE BIO by Elixens B2 = eucalyptus essential oil sold under the name HE EUCALYPTUS RADIATA BIO by Elixens

B3 = Greek oregano essential oil sold under the name HE ORIGAN VERT BIO SICA by Elixens

B4 = geranium essential oil sold under the name HE GERANIUM EGYPTE BIO by Elixens B5 = clove essential oil sold under the name HE GIROFLE CLOU BIO by Elixens B6 = lemongrass essential oil sold under the name HE LEMONGRASS BIO by Elixens

A 10% (weight/volume) stock solution was prepared by mixing 1 g of compound in 9 ml of aqueous 1 %o agar solution. Successive dilutions were carried out with the 1 %o agar solu- tion.

• Tests of compounds A and B alone

50 mI of each of the daughter solutions obtained containing compound A or B are added to the microplate wells. 100 mI of Sabouraud liquid nutrient broth inoculated with the strain Aspergillus niger and 50 mI of aqueous 1 %o agar solution are also added thereto.

• Tests of compounds A and B as a mixture 50 mI of each of the daughter solutions obtained containing compound A and 50 mI of each of the daughter solutions obtained containing compound B are added to the microplate wells. 100 mI of Sabouraud liquid nutrient broth inoculated at double concentration with the strain Aspergillus niger are also added thereto.

Microbial growth control

A positive microbial growth control was also prepared. The positive microbial growth control corresponds to a mixture of 100 mI_ of aqueous 1 %o agar solution with 100 mI_ of Sabouraud liquid nutrient broth inoculated at double concentration with the strain Aspergillus niger in the absence of compounds A and B.

Absorbance control for compounds A and B alone

An absorbance control was performed in parallel on compounds A and B alone. This control corresponds to 100 mI of double-concentration sterile Sabouraud liquid nutrient broth + 100 mI of double-concentration compound A or B.

In the three cases (absorbance control, growth control and test), the final volume present in each of the microplate wells is 200 mI.

In the two cases (test and control), the inoculum represents the concentration of the Asper gillus niger strain present in the final volume of the wells (200 mI) and is between 2 and 6x10⁵ cfu/ml of Aspergillus niger.

The minimum inhibitory concentration (MIC) of each compound A and B alone and in com- bination was determined in a known manner by means of optical density measurements at a wavelength of 620 nm.

The test as described above (tests, absorbance control and growth control) was performed again to test the combinations A and B on the Candida albicans strain.

The results obtained described below for the compound A tested alone may vary depending on the preparation strain collection (containing the microbial strain) used and for which the resistance to the compounds added may vary according to the normal variations of the test method used.

The following results were obtained: (mass percentage of active material)

A) Mixtures with the compound B1 : Cineole rosemary essential oil

Candida albicans

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0625% of A and 0.125% of B1 , i.e. A/B1 ratio = 0.5

ii) 0.125% of A and 0.125% of B1 , i.e. A/B1 ratio = 1

Aspergillus niger

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0313% of A and 0.25% of B1 , i.e. A/B1 ratio = 0.125

ii) 0.0625% of A and 0.25% of B1 , i.e. A/B1 ratio = 0.25

B) Mixtures with the compound B2 : Eucalyptus essential oil

Candida albicans

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0313% of A and 0.125% of B2, i.e. A/B2 ratio = 0.25

ii) 0.0625% of A and 0.125% of B2, i.e. A/B2 ratio = 0.5

iii) 0.125% of A and 0.125% of B2, i.e. A/B2 ratio = 1

iv) 0.125% of A and 0.0625% of B2, i.e. A/B2 ratio = 2 Aspergillus niger

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0313% of A and 0.25% of B2, i.e. A/B2 ratio = 0.125

ii) 0.0625% of A and 0.25% of B2, i.e. A/B2 ratio = 0.25

iii) 0.0625% of A and 0.125% of B2, i.e. A/B2 ratio = 0.5

C) Mixtures with the compound B3: Greek oregano essential oil

Candida albicans

The results obtained show synergistic inhibitory activity for the mixture: 0.0625% of A and 0.0125% of B3, i.e. ratio A/B3 = 5 Aspergillus niger

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0625% of A and 0.0125% of B3, i.e. A/B3 ratio = 5

ii) 0.0625% of A and 0.00625% of B3, i.e. A/B3 ratio = 10

D) Mixtures with the compound B4: Geranium essential oil

Candida albicans

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0625% of A and 0.0125% of B4, i.e. A/B4 ratio = 5

ii) 0.125% of A and 0.0125% of B4, i.e. A/B4 ratio = 10

Aspergillus niger

The results obtained show synergistic inhibitory activity for the mixture: 0.0625% of A and 0.025% of B4, i.e. ratio A/B4 = 2.5

E) Mixtures with the compound B5: Clove essential oil

Candida albicans

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0313% of A and 0.125% of B5, i.e. A/B5 ratio = 0.25

ii) 0.0625% of A and 0.125% of B5, i.e. A/B5 ratio = 0.5

iii) 0.125% of A and 0.125% of B5, i.e. A/B5 ratio = 1

iv) 0.125% of A and 0.0625% of B5, i.e. A/B5 ratio = 2

Aspergillus niger

The results obtained show synergistic inhibitory activity for the mixture: 0.0625% of A and 0.025% of B5, i.e. ratio A/B5 = 2.5 F) Mixtures with the compound B6: Lemongrass essential oil

Candida albicans

The results obtained show synergistic inhibitory activity for the mixture: 0.0625% of A and 0.01 % of B6, i.e. A/B6 ratio = 6.25

Aspergillus niger

The results obtained show synergistic inhibitory activity for the mixtures: i) 0.0625% of A and 0.0125% of B6, i.e. A/B6 ratio = 5

ii) 0.0625% of A and 0.00625% of B6, i.e. A/B6 ratio = 10

Claims

1 . Antimicrobial mixture comprising 4-(3-ethoxy-4-hydroxyphenyl)butan-2-one and an es- sential oil chosen from rosemary, eucalyptus, Greek oregano, geranium, clove or lemongrass essential oils.

2. Mixture according to the preceding claim, characterized in that it has antimicrobial activity on moulds, especially on Aspergillus niger, and/or on yeasts, in particular on Candida albi cans.

3. Mixture according to one of the preceding claims, characterized in that it comprises rose- mary essential oil.

4. Mixture according to the preceding claim, characterized in that it has a 4-(3-ethoxy-4- hydroxyphenyl)butan-2-one/rosemary essential oil weight ratio ranging from 0.35 to 1.5, preferably ranging from 0.7 to 1.3; or ranging from 0.1 to 0.4, preferably ranging from 0.2 to 0.3.

5. Mixture according to Claim 1 or 2, characterized in that it comprises a eucalyptus essential oil.

6. Mixture according to the preceding claim, characterized in that it has a 4-(3-ethoxy-4- hydroxyphenyl)butan-2-one/eucalyptus essential oil weight ratio ranging from 0.15 to 3, preferably ranging from 0.15 to 1.5; or ranging from 0.1. to 0.8, preferably ranging from 0.15 to 0.4 and preferentially ranging from 0.18 to 0.35.

7. Mixture according to Claim 1 or 2, characterized in that it comprises a Greek oregano essential oil.

8. Mixture according to the preceding claim, characterized in that it has a 4-(3-ethoxy-4- hydroxyphenyl)butan-2-one/Greek oregano essential oil weight ratio ranging from 3 to 15, preferably ranging from 3 to 8 and preferentially ranging from 4 to 6.

9. Mixture according to Claim 1 or 2, characterized in that it comprises a geranium essential oil.

10. Mixture according to the preceding claim, characterized in that it has a 4-(3-ethoxy-4- hydroxyphenyl)butan-2-one/geranium essential oil weight ratio ranging from 3 to 15, pref- erably ranging from 7 to 13; or ranging from 1 .5 to 4, preferably ranging from 2 to 3.

1 1. Mixture according to Claim 1 or 2, characterized in that it comprises a clove essential oil.

12. Mixture according to the preceding claim, characterized in that it has a 4-(3-ethoxy-4- hydroxyphenyl)butan-2-one/clove essential oil weight ratio ranging from 0.5 to 4, prefera- bly ranging from 1 to 3, preferentially ranging from 1.5 to 3; or ranging from 2.4 to 4, pref- erably ranging from 2.45 to 3.5 and preferentially ranging from 2.45 to 3.

13. Mixture according to Claim 1 or 2, characterized in that it comprises a lemongrass es- sential oil.

14. Mixture according to the preceding claim, characterized in that it has a

4-(3-ethoxy-4-hydroxyphenyl)butan-2-one/lemongrass essential oil weight ratio ranging from 4 to 10, preferably ranging from 5 to 8; or ranging from 3 to 17, preferably ranging from 3 to 7, preferentially ranging from 4 to 6.

15. Composition comprising, in a physiologically acceptable medium, an antimicrobial mixture according to one of Claims 1 to 14.

16. Composition according to the preceding claim, characterized in that it comprises at least one additional ingredient chosen from water, oils, polyols having from 2 to 10 carbon atoms, gelling agents, surfactants, film-forming polymers, colorants, fragrances, fillers, UV- screening agents, plant extracts, cosmetic and dermatological active agents, and salts.

17. Composition according to either of Claims 15 and 16, characterized in that the 4-(3- ethoxy-4-hydroxyphenyl)butan-2-one is present in an amount ranging from 0.01 % to 5% by weight relative to the total weight of the composition, preferably ranging from 0.01 % to 3% by weight, and preferentially ranging from 0.01 % to 2.5% by weight.

18. Non-therapeutic cosmetic treatment process for caring for and/or making up and/or cleansing keratin materials, comprising the application to said keratin materials of a corn- position according to any one of Claims 15 to 17.