Cosmetic skin care methods

Abstract

The invention provides a cosmetic skin care method for increasing the biosynthesis of GABA by resident skin commensal microbes on the skin of an individual, the method comprising the steps of: (i) adjusting the equilibrium of a microbial population of a region of the skin of an individual to increase the number of Cutibacterium acnes subsp. defendens (phylotype II) bacteria on the individual's skin in said region of the skin, and (ii) administering a GABA precursor comprising L-glutamic acid and / or a salt thereof to said region of the skin.

Description

[0001] COSMETIC SKIN CARE METHODS

[0002] Field of the Invention

[0003] The present invention relates to cosmetic skin care methods for increasing the biosynthesis of GABA by resident skin commensal microbes.

[0004] Background of the Invention

[0005] The stratum corneum contains layers of corneocytes embedded in a lipid matrix which is made up of a unique complex mixture of polar and nonpolar lipids that, unlike biological membranes, is almost devoid of phospholipids. Its main components are ceramides, cholesterol, and free fatty acids (predominantly long-chain and saturated) which are organized into specific lamellar structures whose integrity depends not only on the quality of the fractions present but also on their respective proportions.

[0006] Gamma-aminobutyric acid (GABA) is a biologically active four-carbon non-proteinogenic amino acid found in prokaryotes and eukaryotes. In mammals, GABA acts as the major inhibitory neurotransmitter in the central nervous system. It is also widely distributed in peripheral tissues.

[0007] Studies in the dermatological field have indicated that GABA may play multiple beneficial roles in skin, such as inter alia stimulating the synthesis of hyaluronic acid (HA), controlling the balance between the synthesis and degradation of type I collagen, accelerating skin barrier repair, and regulating skin barrier homeostasis.

[0008] Evidently it is important to be able to stimulate the synthesis of GABA to allow it to carry out the important roles for which it is responsible.

[0009] The present invention addresses this problem. of the Invention

[0010] The invention provides a cosmetic skin care method for increasing the biosynthesis of GABA by resident skin commensal microbes on the skin of an individual, the method comprising the steps of:

[0011] (i) adjusting the equilibrium of a microbial population of a region of the skin of an individual to increase the number of Cutibacterium acnes subsp. defendens (phylotype II) bacteria on the individual's skin in said region of the skin, and

[0012] (ii) administering a GABA precursor comprising L-glutamic acid and / or a salt thereof to said region of the skin.

[0013] Detailed Description of the Invention

[0014] As used herein, “cosmetic skin care” means regulating and / or improving cosmetic qualities of the skin, as opposed to curing, treating, or preventing a disease or disorder. Accordingly, such cosmetic qualities are subject to regulation and / or improvement both in healthy subjects as well as those which present diseases or disorders of the skin such as psoriasis, lichen planus, folliculitis, or atopic dermatitis.

[0015] Examples of cosmetic skin care benefits in the context of this invention include providing a smoother, more even texture; improving the elasticity or resiliency of the skin; improving the firmness of the skin; improving the hydration status or moisturization of the skin; improving skin barrier properties; and reducing the appearance of redness or skin blotches.

[0016] As used herein, “skin” is understood as the layers which comprise it, from the uppermost layer or stratum corneum to the lowermost layer or hypodermis, both inclusive. These layers are composed of different types of cells such as keratinocytes, fibroblasts, melanocytes, mastocytes, neurons, and adipocytes. The term “skin” also comprises the scalp.

[0017] As used herein, the term “resident skin commensal” denotes a microbe which can normally be found on healthy human skin, whose interactions on the skin are either neutral or beneficial, and which are permanent inhabitants on the surface of the skin, the stratum corneum and within the outer layer of the epidermis and the deeper crevices of the skin and hair follicles. Microbial colonization is differentially shaped by the physiological and topological variation of the skin, and varies systematically among different skin habitats, such as between dry, moist, and sebaceous skin. Resident skin commensal microbes are characterized in that they can grow and multiply on the skin without invading or damaging the skin tissue. Another characteristic of these microbes is that washing does not easily remove them in deeper skin regions.

[0018] The members of the species C. acnes have been classified into three major genetic lineages, (phylotypes, I, II, and III) based on serological agglutination tests, cell wall sugar analysis, fatty acid profiles, and morphology. These have been assigned to three subspecies as follows: phylotype I as C. acnes subsp. acnes, phylotype II as C. acnes subsp. defendens, and phylotype III as C. acnes subsp. elongatum. Based on 16S rRNA gene analysis, C. acnes strains have also been classified into multiple ribotypes (RTs).

[0019] Studies indicate that C. acnes subspecies acnes (phylotype I) strains (RT1 , RT3, RT4, RT5, and RT8) are more often associated with acne. By contrast, C. acnes subspecies defendens (phylotype II) strains (RT2 and RT6) are more frequently found on healthy skin, particular the RT6 subgroup which has been found to be 99% associated with healthy skin.

[0020] C. acnes subsp. defendens (phylotype II) strains associated with healthy skin display a number of strain specific characteristics at the genetic, transcriptional, and translational levels, which may account for their commensal phenotype and non-association with acne. Elements that may be used to characterise such strains include the presence of a complete set of the CRISPR / Cas genes. Also, C. acnes subsp. defendens (phylotype II) strains associated with healthy skin secrete only low levels of porphyrins and carry a deoR gene that represses porphyrin biosynthesis. There is growing evidence that the colonization of such strains on the skin is not only non-associated with acne but can actually confer benefits to the skin, for example through modulation of immune cell activity and secretion of protective substances.

[0021] According to step (i) of the method of the invention, the equilibrium of a microbial population of a region of the skin of an individual is adjusted to increase the number of Cutibacterium acnes subsp. defendens (phylotype II) bacteria on the individual's skin in said region of the skin. These strains of C. acnes represent resident skin commensal microbes which are involved in the biosynthesis of GABA.

[0022] In step (i) of the method of the invention, the microbial equilibrium may be adjusted by treating said region of the skin with a probiotic including live cultures of selected C. acnes subsp. defendens (phylotype II) strains which are associated with healthy skin. Preferably, in step (i) of the method of the invention, the microbial equilibrium is adjusted by treating said region of the skin with a prebiotic such as erythritol ((2R,3S)-butan-1 ,2,3,4-tetrol).

[0023] Studies show that erythritol can support the growth of C. acnes ribotypes (RTs) associated with healthy skin (RT2 and RT6) whilst inhibiting, or not promoting, the growth of C. acnes RTs associated with acne (RT1 , RT3, RT4, RT5, and RT8). Collectively, these microbial strains naturally compete for local resources and attachment to epithelial sites. Rather than generally reducing microbial load and diversity, the prebiotic renders an ecological change that favours the growth, metabolism and / or colonization of the desirable over the less desirable microbial strains.

[0024] A combination of the probiotic and prebiotic may also be used, either simultaneously or sequentially.

[0025] If desired, an antimicrobial may be administered to said region of the skin prior to treatment with the probiotic and / or with the prebiotic.

[0026] Suitable antimicrobials include sulfur, benzoyl peroxide, antimicrobial zinc salts (such as zinc oxide, zinc gluconate and zinc PCA), antimicrobial organic acids (such as salicylic acid, lactic acid, glycolic acid, pyruvic acid, azelaic acid, succinic acid, ferulic acid, cinnamic acid and picolinic acid), cationic antimicrobials (such as benzalkonium chloride, cetyl pyridinium chloride and cetyl trimethyl ammonium bromide), and antimicrobial essential oil actives (such as thymol, eugenol, menthol, geraniol, vertenone, eucalyptol, pinocarvone, cedrol, anethol, carvacrol, hinokitiol, berberine, methyl salicylate, terpineol and limonene).

[0027] Mixtures of any of the above-described materials may also be used.

[0028] According to step (ii) of the method of the invention, a GABA precursor comprising L-glutamic acid and / or a salt thereof is administered to said region of the skin. L-Glutamic acid (L-2-amino-pentanedioic acid) has the following structural formula (I):

[0029] Salts of L-glutamic acid may suitably correspond to the following structural formula (II): in which n is 1 or 2. Suitable counterions X include ammonium, or an alkali metal such as sodium or potassium, or an alkaline earth metal such as calcium or magnesium.

[0030] Mixtures of any of the above-described materials may also be used.

[0031] L-glutamic acid of formula (I) is preferred for use in the method of the invention.

[0032] Steps (i) and (ii) of the method of this invention may be carried out simultaneously or sequentially, in any order.

[0033] Accordingly, compositions for carrying out the method of this invention may be formulated as two-part compositions having a first part comprising the probiotic and / or prebiotic in association with a second part comprising the GABA precursor; or alternatively may be formulated as a single composition comprising the probiotic and / or prebiotic in combination with the GABA precursor.

[0034] A preferred composition for carrying out the method of this invention comprises, in a cosmetically acceptable vehicle:

[0035] (i) from 0.01 to 10%, preferably from 0.1 to 5% (by weight based on the total weight of the composition) of a GABA precursor comprising L-glutamic acid and / or a salt thereof, and

[0036] (ii) from 0.01 to 10%, preferably from 0.1 to 5% (by weight based on the total weight of the composition) of erythritol.

[0037] Preferably, at least 75%, more preferably at least 85%, and most preferably 100% of the GABA precursor in said composition is L-glutamic acid (by weight based on the total weight of the GABA precursor).

[0038] The term “cosmetically acceptable” means that the vehicle is suitable for topical application to the skin, has good aesthetic properties and will not cause any ingredient compatibility, safety, or toxicity concerns.

[0039] Suitable cosmetically acceptable vehicles may comprise an aqueous phase, an oil phase, an alcohol, a silicone phase, or a mixture thereof, and may be in the form of an emulsion.

[0040] Emulsions can have a range of consistencies including thin lotions (which may also be suitable for spray or aerosol delivery), creamy lotions, light creams, and heavy creams.

[0041] Exemplary emulsions include water-in-oil emulsions, oil-in-water emulsions, silicone-in-water emulsions, water-in-silicone emulsions, polyol-in-silicone emulsions, silicone-in-polyol emulsions, polyol-in-oil emulsions, oil-in-polyol emulsions, wax-in-water emulsions, and water- oil-water triple emulsions. Preferred emulsions include oil-in-water emulsions and water-in-oil emulsions.

[0042] Compositions in the form of an emulsion, and suitable for carrying out the method of this invention, typically have an oil phase containing one or more cosmetically acceptable fatty materials which may be liquid or solid at room temperature (25°C). Suitable cosmetically acceptable fatty materials include naturally derived oils (such as sunflower oil, borage oil, soybean oil, castor oil, olive oil and almond oil); esters of monoalcohols or of polyols with monocarboxylic or polycarboxylic acids, at least one of the alcohols and / or acids comprising at least one hydrocarbon-based chain containing at least 6 carbon atoms (such as octyl palmitate, isopropyl myristate, isopropyl palmitate, isopropyl isostearate, hexyl laurate, isohexyl laurate, isohexyl palmitate, decyl oleate, isodecyl oleate, hexadecyl stearate, decyl stearate, dihexyldecyl adipate, lauryl lactate, myristyl lactate, cetyl lactate, oleyl stearate, oleyl oleate, oleyl myristate, lauryl acetate, cetyl propionate, isononyl isononanoate, propylene glycol dicaprate, diisopropyl adipate, dibutyl adipate, and oleyl adipate); ethers (such as dicapryl ether); fatty alcohols (such as cetyl alcohol, stearyl alcohol and behenyl alcohol); isoparaffins (such as isooctane, isododecane and isohexadecane); silicone oils (such as dimethicones, cyclic silicones, and polysiloxanes); and hydrocarbon oils (such as mineral oil, petrolatum and polyisobutene); fatty acids containing from 8 to 30 carbon atoms, (such as stearic acid, lauric acid, palmitic acid and oleic acid); vegetable fats (such as cocoa butter, coconut oil, palm oil and shea butter); petroleum-based, natural and synthetic waxes (such as lanolin wax, beeswax, carnauba wax, candelilla wax, paraffin wax, lignite wax, microcrystalline waxes, ceresin, ozokerite, and polyethylene waxes); hydrogenated oils which are solid at 25° C (such as hydrogenated castor oil, hydrogenated jojoba oil, hydrogenated palm oil, hydrogenated tallow and hydrogenated coconut oi I) ; and fatty esters that are solid at 25°C (such as C20-40 alkyl stearate).

[0043] Compositions in the form of an emulsion, and suitable for carrying out the method of this invention, typically have an aqueous phase, which may also include one or more organic liquids that are miscible with water at room temperature (25°C). Exemplary water-miscible organic liquids include monohydric and polyhydric alcohols and derivatives thereof such as C2-C6 alkanols (such as ethanol and isopropanol); C2-C10 glycols and polyols (such as glycerol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, caprylyl glycol, dipropylene glycol, and diethylene glycol); C3-C16 glycol ethers (such as mono-, di-, or tripropylene glycol (C1-C4) alkyl ethers and mono-, di-, or triethylene glycol (C1-C4) alkyl ethers) and polyethylene glycol having 2 to 12 oxyethylene units.

[0044] Compositions in the form of an emulsion, and suitable for carrying out the method of this invention, generally include surface active ingredients, such as emulsifiers and solubilizers, to enable two or more immiscible components to be combined homogeneously and to help stabilize the composition. Emulsifiers that may be used to form O / W or W / O emulsions include sorbitan oleate, sorbitan sesquioleate, sorbitan isostearate, sorbitan trioleate, PEG-20 sorbitan isostearate, polyglyceryl-3-diisostearate, polyglycerol esters of oleic / isostearic acid, polyglyceryl-6 hexaricinolate, polyglyceryl-4-oleate, polyglyceryl-4 oleate / PEG-8 propylene glycol cocoate, polyglyceryl-2 dipolyhydroxystearate, PEG-30 dipolyhydroxystearate, oleamide DEA, TEA myristate, TEA stearate, magnesium stearate, sodium stearate, potassium laurate, potassium ricinoleate, sodium cocoate, sodium tallowate, potassium castorate, sodium oleate, cetyl phosphate, diethanolamine cetyl phosphate, potassium cetyl phosphate, sodium glyceryl oleate phosphate, dimethicone copolyol, cetyl dimethicone copolyol, octyldimethicone ethoxyglucoside copolyol, dimethicone copolyol crosspolymer and laurylmethicone copolyol.

[0045] Compositions for carrying out the method of this invention may also be formulated in a singlephase carrier such as a hydrophobic or hydrophilic liquid. Suitable hydrophobic liquid carriers include liquid polyorganosiloxanes, mineral oils, hydrogenated polyisobutene, polydecene, paraffins and isoparaffins of at least 10 carbon atoms, aliphatic or aromatic ester oils (such as isopropyl myristate, lauryl myristate, isopropyl palmitate, diisopropyl sebacate, diisopropyl adipate and Ci2 to C15 alkyl benzoates), polyglycol ethers (such as polyglycol butanol ethers) and mixtures thereof. Suitable hydrophilic liquid carriers include water, monohydric or polyhydric aliphatic alcohols having 2 to 8, preferably 2 or 3 carbon atoms (such as ethanol and isopropanol, oligoglycol ethers having 2 to 5 repeat units (such as dipropylene glycol) and mixtures thereof.

[0046] Liquid form compositions for carrying out the method of this invention may be thickened, for example using one or more water soluble or colloidally water-soluble polymeric thickening agents. Suitable water soluble or colloidally water-soluble polymeric thickening agents include hydroxyethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, polyquaternium-10, carrageenan, guar gum, hydroxypropyl guar gum, xanthan gum, polyvinylalcohol, acrylic acid / ethyl acrylate copolymers, carboxyvinyl polymers, cross-linked polyacrylate polymers and polyacrylamide polymers.

[0047] Solid form compositions for carrying out the method of this invention, such as gels and sticks, generally include one or more structurants, in an amount ranging from about 1% to about 35% (by weight based on the total weight of the composition), depending upon the desired product consistency. Examples of structurants include fatty acid gelling agents selected from saturated fatty acids or hydroxy acids containing from about 8 to 30 carbon atoms and their salts, esters or amides (such as sodium and potassium stearate, 12-hydroxystearic acid, esters of 12- hydroxy stearic acid and amides of 12-hydroxystearic acid); saturated, unsubstituted monohydric fatty alcohols containing from about 8 to 30 carbon atoms (such as cetyl alcohol, myristyl alcohol and stearyl alcohol); acyl amino acid derivatives such as N-lauroyl-L-glutamic acid di-n-butylamide; amide derivatives of di or tribasic carboxylic acids such as alkyl N,N' dialkylsuccinimide; inorganic particulate thickening agents selected from siliceous and alumino- siliceous materials (such as fumed silicas, bentonites, hectorites, colloidal magnesium aluminum silicates and organoclays such as stearalkonium bentonite, disteardimonium hectorite, quaternium 90-bentonite), quaternium-18 bentonite and quaternium-18 hectorite); and petroleum-based, natural and synthetic waxes (such as lanolin wax, beeswax, carnauba wax, candelilla wax, castor wax, montan wax, paraffin wax, lignite wax, microcrystalline waxes, ceresin, ozokerite, polymethylene and polyethylene waxes).

[0048] Combinations of any of the above-described materials or product forms may also be used.

[0049] Compositions for carrying out the method of this invention may include additional skin care actives for improving the physical and / or aesthetic characteristics of the skin.

[0050] Examples of additional skin care actives include vitamins, minerals and / or antioxidants, skin anti-hyperpigmentation agents, sunscreens, anti-irritants, exfoliating agents, and mixtures thereof.

[0051] Suitable vitamins, minerals and / or antioxidants include natural botanical antioxidants derived from plant materials such as fruits, vegetables, herbs and spices (such as goji berry, white tea, rosemary, green tea, grape seed and lemongrass extracts); vitamin A and its precursors or derivatives (such as beta-carotene, retinyl palmitate); vitamin B3 and its precursors or derivatives (such as niacinamide); vitamin B5 and its precursors or derivatives (such as panthenol and its precursors or derivatives); vitamin C and its precursors or derivatives (such as tetrahexyldecyl ascorbate, ascorbyl palmitate); vitamin E and its precursors or derivatives (such as d-alpha-tocopherol, tocopheryl acetate); vitamin K and its precursors or derivatives; selenium and its derivatives (such as L-selenomethionine); and alpha lipoic acid.

[0052] Suitable skin anti-hyperpigmentation agents include natural botanical agents derived from plant materials (such as Arctostaphylos patula and Arctostaphylos viscida extracts, Emblica officinalis extract, Mitracarpus scaber extract, Uva ursi (bearberry) extract, Morus bombycis (mulberry) extract, Morus alba (white mulberry) extract, Broussonetia papyrifera (paper mulberry) extract, licorice extract, acerola cherry extract, Chlorella vulgaris extract, Aloe ferrox extract and Rumex occidentalis extract); synthetic or natural sugar amines (such as glucosamine, N-acetyl glucosamine, glucosamine sulfate, mannosamine, N-acetyl mannosamine, galactosamine, N- acetyl galactosamine and their hydrochloride salts); retinoids (such as retinol, retinal, retinoic acid and C2-20 esters of retinol such as retinyl palmitate, retinyl acetate, retinyl propionate, retinyl linoleate and retinyl oleate); kojic acid and C2-20 esters thereof (such as kojic acid monobutyrate, kojic acid monocaprate, kojic acid monopalmitate, kojic acid monostearate and kojic acid monobenzoate); hydroquinone, hydroquinone monomethyl ether, hydroquinone monoethyl ether, hydroquinone monobenzyl ether, a and p-arbutin, deoxyarbutin (4- [(tetrahydro-2H-pyran-2-yl)oxy]phenol), mequinol (4-hydroxyanisole), glutathione, cysteine, N- acetyl-L-cysteine, azelaic acid, magnesium ascorbyl phosphate, sodium ascorbyl phosphate, peroxides (such as hydrogen peroxide, zinc peroxide, sodium peroxide and benzoyl peroxide); 3-aminotyrosine, glycyrrhizinic acid and 4-substituted resorcinol derivatives (such as 4-methyl resorcinol, 4-ethyl resorcinol, 4-propyl resorcinol, 4-isopropyl resorcinol, 4-butyl resorcinol, 4- pentyl resorcinol, 4-hexyl resorcinol, 4-heptyl resorcinol, 4-octyl resorcinol, 4-nonyl resorcinol, 4- decyl resorcinol, 4-undecyl resorcinol, 4-dodecyl resorcinol, 4-cyclopentyl resorcinol, 4- cyclohexyl resorcinol, 4-cycloheptyl resorcinol, and 4-cyclooctyl resorcinol).

[0053] Suitable sunscreens protect the skin from ultraviolet (UV) solar radiation falling within both the UVB region (between 290nm to 320 nm wavelengths) and the UVA region (between 320nm and 400nm wavelengths). Examples of sunscreens include methoxycinnamate derivatives (such as octyl methoxycinnamate and isoamyl methoxycinnamate); camphor derivatives (such as 4- methyl benzylidene camphor, camphor benzalkonium methosulfate, and terephthalylidene dicamphor sulfonic acid); salicylate derivatives (such as octyl salicylate and homosalate); sulfonic acid derivatives (such as phenylbenzimidazole sulfonic acid); benzone derivatives (such as dioxybenzone, sulisobenzone, and oxybenzone); benzoic acid derivatives (such as aminobenzoic acid and octyldimethyl para-amino benzoic acid); octocrylene, diethylhexyl butamido triazone, octyl triazone, butyl methoxydibenzoyl methane, drometrizole trisiloxane, menthyl anthranilate and inorganic UV-absorbing particles (such as zinc oxide and titanium dioxide).

[0054] Suitable anti-irritants include allantoin, aloe vera, a-bisabolol, caffeine, chamomile extract, Cola nitada extract, cucumber extract, dipotassium glycyrrhizinate, glycyrrhizic acid, green tea extract, lecithin or hydrogenated lecithin, licorice extract, Avena sativa (oat) meal extract, tea tree oil, salicylic acid, acetylsalicylic acid, strontium acetate, strontium chloride, strontium nitrate, fatty acids with anti-irritant properties (such as linoleic acid and linolenic acid) and aromatic aldehydes with anti-irritant properties (such as 4-methoxy benzaldehyde, 4-ethoxy benzaldehyde, 4-butoxy benzaldehyde and 4-pentoxy benzaldehyde). Suitable exfoliating agents include benzoyl peroxide, benzoic acid, 3-hydroxy benzoic acid, salicylic acid, acetic acid, trichloroacetic acid, 1-pyrrolidone-5-carboxylic acid, a-hydroxy acids (such as glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid); p-hydroxy acids (such as p-hydroxybutyric acid); a-keto acids (such as pyruvic acid, 2-oxopropanoic acid, 2- oxobutanoic acid and 2-oxopentanoic acid); and oxa acids (such as 3,6,9-trioxaundecanedioic acid).

[0055] Mixtures of any of the above-described materials may also be used.

[0056] Compositions for carrying out the method of this invention may also include additional functional ingredients for improving the physical and / or aesthetic characteristics of the composition.

[0057] Examples of suitable additional functional ingredients include water soluble or colloidally water soluble polymeric thickening agents (such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, polyquaternium-10, carrageenan, guar gum, hydroxypropyl guar gum, xanthan gum, polyvinylalcohol, acrylic acid / ethyl acrylate copolymers, carboxyvinyl polymers, cross-linked polyacrylate polymers and polyacrylamide polymers); structurant clays (such as magnesium aluminum silicate, attapulgite, bentonite, montmorillonite and hectorite); inorganic pigments (such as titanium oxide, zirconium oxide, cerium oxide zinc oxide, iron oxide, chromium oxide and ferric blue); organic pigments (such as carbon black and barium, strontium, calcium, and aluminum lakes); pearlescent agents (such as mica coated with titanium oxide and / or iron oxide); dyes, preservatives (such as disodium EDTA, benzyl alcohol, methylparaben, phenoxyethanol, propylparaben, ethylparaben, butylparaben and isobutylparaben); pH adjusters and fragrances.

[0058] Mixtures of any of the above-described materials may also be used.

[0059] The composition for carrying out the method of this invention may be packaged in a suitable container to suit its viscosity and intended use by the consumer. For example, a lotion or a cream can be packaged in a bottle or a roll-ball applicator, or a propellant-driven aerosol device or a container fitted with a pump suitable for finger operation. When the composition is a cream, it can simply be stored in a non-deformable bottle or squeeze container, such as a tube or a lidded jar. Use

[0060] The cosmetic composition for carrying out the method of this invention may suitably be applied to the skin at the rate of one or two applications per day. Generally, an amount corresponding to about 1 to 2 ml of the composition per application is applied uniformly over the area of treatment twice daily for a period of at least 7 (seven) days, preferably at least 30 (thirty) days.

[0061] The invention will be further illustrated by the following, non-limiting Examples.

[0062] EXAMPLES

[0063] Step I: erythritol as selective prebiotic for C.acnes subsp. defendens (phylotype II)

[0064] Erythritol was evaluated in different concentrations (5% and 10%) for its ability to increase growth and acid production of two different strains of Cutibacterium acnes’. one associated with healthy skin<1> and the other associated with acne<2\1) Cutibacterium acnes subsp. defendens ATCC 11828 (phylotype II, ribotype RT2)

[0065] (2)Cutibacterium acnes subsp. acnes ATCC 6919 (phylotype I, ribotype RT 1 )

[0066] Test bacterial inoculums were prepared in recommended growth media for 24 hours at 37°C under anaerobic conditions. Inoculums were centrifuged and resuspended in liquid media diluted to 50% in sterile distilled water. The inoculums were adjusted to a cell density of 1.5-5 x 108CFU / ml.

[0067] To a 96-well PreSens HydroPlate®, 90 pl of erythritol test solution, 90 pl of liquid media at 50% strength and 20 pl of bacterial inoculum was added. Growth controls were included where sterile distilled water replaced the test solution, and 27.5% and 100% media were added. For the HydroPlate® pH buffer controls were included.

[0068] The HydroPlate® was read kinetically for fluorescence for 96 hours at 37°C. PreSens calibration software pHSolver_v10 was used as part of the analysis.

[0069] The following Table 1 shows the calculated acid produced by the tested bacterial species after incubation with the test erythritol, compared to the growth control.

[0070] Table 1 It can be seen from the results that the health related Cutibacterium acnes (ATCC 11828) show significantly greater acid production when supplemented with erythritol in accordance with the invention, when compared to the acne associated Cutibacterium acnes (ATCC 6919) and the counterpart control.

[0071] Step / / . Biosynthesis of GABA by health associated Cutibacterium acnes

[0072] The biosynthesis of GABA by health associated Cutibacterium acnes (ATCC 11828) and acne associated Cutibacterium acnes (ATCC 6919) when L-Glutamic acid was used as substrate was assessed using an ELISA kit.

[0073] Test bacterial inoculums were prepared in recommended growth media for up 48 hours at 37°C under anaerobic conditions. Inoculums were centrifuged and resuspended in liquid media diluted to 25% in sterile distilled water. The inoculums were adjusted to an optical density (OD) at 600nm of 1. As a substrate, 8mg / ml of L-glutamic acid solution was prepared in 25% media.

[0074] Tested conditions were prepared and incubated for 24h at 37 °C shaking. For that, 5ml of each isolate at OD 1 was added to 5ml of 8mg / ml L-glutamic acid (substrate). Controls were prepared where no substrate (only isolates in media) and substrate (only L-glutamic acid in media) were included in the assay.

[0075] After 24h incubation, an ELISA kit was used to measure the amount of GABA production (ab287792 - Human QuickDetect™ GABA ELISA Kit, from Abeam pic, Cambridge UK), by following manufacturer’s instructions.

[0076] The following Table 2 shows the amount of GABA produced by the tested bacterial species after incubation with the substrate L-Glutamic-acid, compared to the controls.

[0077] Table 2 Overall, it can be seen from the results that the health-related Cutibacterium acnes (ATCC 11828) was able to produce GABA when supplemented with L-glutamic acid, whereas the acne associated Cutibacterium acnes (ATCC 6919) and controls were not. The following Table 3 illustrates a skin care composition for carrying out the method of the present invention.

[0078] Table 3

[0079] Skin Care Lotion

Claims

Claims1. A cosmetic skin care method for increasing the biosynthesis of GABA by resident skin commensal microbes on the skin of an individual, the method comprising the sequential steps of:(i) adjusting the equilibrium of a microbial population of a region of the skin of an individual to increase the number of Cutibacterium acnes subsp. defendens (phylotype II) bacteria on the individual's skin in said region of the skin, in which the microbial equilibrium is adjusted by applying a cosmetic composition comprising erythritol ((2R,3S)-butan-1 ,2,3,4-tetrol) to said region of the skin with, and(ii) applying a cosmetic composition comprising a GABA precursor to said region of the skin, in which the GABA precursor comprises L-glutamic acid and / or a salt thereof .2.. A method according to claim 1, in which at least 75% of the GABA precursor is L- glutamic acid (by weight based on the total weight of the GABA precursor).

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