WO2003075880A1

WO2003075880A1 - Cosmetic compositions comprising citric acid triesters

Info

Publication number: WO2003075880A1
Application number: PCT/EP2003/002260
Authority: WO
Inventors: Venkitachalam Venkita Subra Mani; Pankaj Chandrakant Shah; Ramesh Surianarayanan; Sushama Shripad Wagh; Govindarajan Raman; Bhashkar MUKHERJI
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2002-03-11
Filing date: 2003-03-05
Publication date: 2003-09-18
Also published as: AU2003215632A1

Abstract

A skin care cosmetic composition comprising: (a) an amount from 0.01 to 20% by weight of one or more esters of citric acid having the structure (1): where R1 is chosen from one of tri-secondarybutyl citrate, tri-isopropyl citrate, tri lauroyl citrate or their mixtures thereof; and (b) from 10 to 99.9% by weight of an acceptable vehicle for the citric acid.

Description

COSMETIC COMPOSITIONS COMPRISING CITRIC ACID TRIESTERS

The invention relates to a composition for topical application to human skin in order to promote the repair of photo-damaged skin and/or to reduce or prevent the damaging effects of ultra-violet light on skin. The invention also relates to the use of such compositions in the repair of photo-damaged skin, and in the prevention of damage to skin due to exposure to ultra-violet light.

The treatment of human skin damaged due to exposure to ultra-violet light, i.e. photo-damage, has been subject to much research effort in recent years, particularly with the realisation that skin cancer and other skin disorders can arise where the exposure to sunlight is excessive. This problem is even more serious with the depletion of the ozone layer which is believed to permit a higher level of ultraviolet radiation to reach the earth's surface.

Chronic exposure to sunlight results in multiple adverse effects on all structural elements of the skin. The

_* clinical manifestation of these changes, collectively known as photo-ageing is lax, dry inelastic skin that is wrinkled and blotchy with a coarse, roughened texture.

Skin blotchiness or mottling (hyperpigmentation) which accompanies photo-ageing results from changes in the melanocytes within the population of epidermal cells. These pigment producing cells, which unlike the keratinocytes remain at the base of the epidermis, lose their normal regulation process with ageing and produce excess pigment. This leads to the formation of dense perinuclear clumps of melanin in slowly turning over keratinocytes within the epidermis, and areas of hyper-pigmentation or "age spots' develop .

In the therapy of such hyperpigmented skin, certain skin lightening agents such as kojic acid, hydroquinone or ascorbic acid are effective by inhibiting the formation of melanin. Vitamin A acid (retinoic acid) is beneficial in hyper-pigmentation problems by normalising the melanocyte population.

Also by increasing cell turnover, vitamin A acid prevents accumulation of pigment within the more rapidly dividing and migrating keratinocytes. Vitamin A acid also enhances the pigment reducing potential of conventional skin lightening agents .

The topical application of vitamin A acid does however have a major drawback in that it is a skin irritant, and can accordingly damage the skin. It's recommended use for example as a prescription drug in the treatment of acne involves careful control, such that excessive doses are avoided in order to restrict the side effects which can occur with skin. By the same token, the use of vitamin A acid in the treatment or prevention of photo-damaged skin is severely limited by these side effects.

IN 173513 (Hindustan Lever Limited) discloses certain esters of citric acid, especially tributyl citrate. The citrate esters are particularly effective and treat or prevent photo-damage of skin, without the aforementioned side effects .

However, citric esters in general have been found to show hydrolytic instability in certain skin formulations, and this can cause a break up of the emulsion. The breakdown products of such esters can also affect the skin cream properties, in particular perfume impact. For example the formulation may give off odours after storage for a period of time.

The invention is accordingly concerned with compositions comprising selected esters of citric acid, optionally in combination with sunscreen materials, for topical application to human skin, and the use of these esters in the treatment of photo-damaged and/or hyperpigmented skin, and in slowing down the ageing process generally, as well as moisturising and the treatment of acne. The esters of the invention are hydrolytically stable, and the compositions of the invention are stable on storage and do not alter the chemical nature of the cream components.

Accordingly, the invention provides a composition suitable for topical application to human skin for example in order to reduce the damaging effects of ultra-violet light on skin, which composition comprises:

a. an effective amount of from 0.01 to 20% by weight of one or more esters of citric acid chosen from tri secondary butyl citrate, isopropyl citrate or lauroyl citrate or their mixtures thereof, said esters having the following structure (1) :

0 II

CH2 - C - 0 - Rl

I °

I II

HO - C - C - O - Rl I O

I II

CH2 - C - 0 - Rl

wherein Rl is chosen from one of

CH3

-CH₂CHCH₃ or

-CH(CH₃)₂ or -(CH₂)nCH₃ or their mixtures thereof; and

b. an acceptable vehicle for the citric acid ester.

Preferably the isopropyl citrate is tri -isopropyl citrate; preferably the lauroyl citrate is tri-lauroyl citrate.

The invention also provides for a process to make the citric esters suitable for the invention comprising the steps of esterifying the ester with a suitable alcohol in the presence of a suitable catalyst. According to a further aspect of the inventon, there is provided a cosmetic method of treating acne comprising applying thereto a topical composition comprising an effective amount (eg. 0.01% to 10%, preferably 0.01% tO 10%, more preferably 0.01% to 5%) of a triester of citric acid having structure (II) .

0

CH₂ -C - 0 R

0

R 0 -C C - 0 - R (II)

O

CH₂ -C - 0 - R^~ wherein

1 2 3 R , R and R each independently represent a branched or unbranched alkyl, alkenyl, aryl, alkylaryl or arylalkyl group, each said group being optionally substituted and having from 1 to 18 carbon atoms,

R represents -H , or a branched or unbranched saturated or unsaturated acyl, alkyl, aryl, alkylaryl or arylalkyl group, each said group being optionally substituted and having from

1 to 18 carbon atoms; and b) a cosmetically acceptable vehicle for the citric acid ester. In yet a further aspect is provided use of a compound of • general formula II above for the manufacture of a medicament for the treatment of acne .

All parts and percentages are by weight unless otherwise indicated.

The invention concerns a composition comprising an organic ester of citric acid, together with a suitable cosmetically acceptable vehicle, which acts to retard the ageing process of the skin, when applied topically thereto. The topical composition may provide benefits in terms of moisturisation; it may also be a useful acne treatment. The composition can also optionally comprise a sunscreen, which together with the ester of citric acid can prevent skin blotchiness and mottling due to hyperpigmentation, and generally effect an overall improvement in skin texture with reduction in fine wrinkling and improved skin colour. Co-formulation with a sunscreen will also enhance synergistically the photo- stability and activity of the ester of citric acid within the formulation, and also prevent further actinic damage to all epidermal cells and dermal tissue.

In one aspect, the composition according to the invention comprises an ester of citric acid or mixtures thereof, each having the structure (1) described above.

The preferred esters of citric acid are tri-secondary butyl citric acid, tri-isopropyl citrate or tri- lauroyl citrate or mixtures thereof. The amount of the ester of citric acid having the structure (1), present in the composition accordingly to the invention is from 0.01 to 20%, preferably from 0.1 to 10% by weight of the composition and more preferably from 0.1 to 5% by weight of the composition.

The citric acid esters can be prepared by any suitable process known in the art. Citric acid can be esterified with the corresponding alcohol (e.g. 2-butanol, isopropyl alcohol, lauroyl alcohol) using a suitable catalyst chosen from p-toluene sulphonic acid, phosphotungstic acid, ferric chloride, ferric ammonium sulphate and zirconium oxide, p- Toluene sulphonic acid is especially preferred. Magnesium sulphate can be employed in the reaction as an external water scavenger. When magnesium sulphate is not employed, the alcohol is preferably taken in stoichiometric excess of the citric acid.

Alternatively, water can be removed from the reaction mixture by using compounds that form azeotrope with water, such as eg. toluene, and the azeotropic mixture can be removed by distillation.

The composition according to the invention also comprises a cosmetically acceptable vehicle to act as a dilutant, dispersant or carrier for other materials present in the composition, so as to facilitate their distribution when the composition is applied to the skin.

Vehicles other than water can include liquid or solid emollients, solvents, humectants, thickeners and powders. Examples of each of these types of vehicle, which can be used singly or as mixtures of one or more vehicles, are as follows :

Emollients, such as stearyl alcohol, glyceryl monoricinoleate, mink oil, cetyl alcohol, isopropyl isostearate, stearic acid, isobutyl palmitate, isocetyl stearate, oleyl alcohol, isopropyl laurate, hexyl laurate, decyl oleate, octadecan-2-ol, isocetyl alcohol, eicosanyl alcohol, behenyl alcohol, cetyl palmitate, silicone oils such as dimethylpolysiloxane, di-n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, polyethylene glycol, triethylene glycol, lanolin, cocoa butter, corn oil, cotton seed oil, olive oil, palm kernel oil, rapeseed oil, safflower seed oil, evening primrose oil, soybean oil, sunflower seed oil, avocado oil, sesame seed oil, coconut oil, arachis oil, castor oil, acetylated lanolin alcohols, petroleum jelly, mineral oil, butyl myristate, isostearic acid, palmitic acid, isopropyl linoleate, lauryl lactate, myristyl lactate, decyl oleate, myristyl myristate;

Propellants, such as propane, butane, isobutane, dimethyl ether, carbon dioxide, nitrous oxide;

Solvents, such as ethyl alcohol, isopropanol, acetone, ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether;

Powders, such as chalk, talc, fullers earth, kaolin, starch, gums, colloidal silica, sodium polyacrylate, tetra alkyl and/or trialkyl aryl ammonium smectites, chemically modified magnesium aluminium silicate, organically modified montmorillonite clay, hydrated aluminium silicate, fumed silica, carboxyvinyl polymer, sodium carboxymethyl cellulose, ethylene glycol monostearate .

The cosmetically acceptable vehicle will usually form from 10 to 99.9%, preferably from 50 to 99% by weight of the emulsion, and can, in the absence of other cosmetic adjuncts, form the balance of the composition.

The composition of the invention optionally can comprise an organic sunscreen further to enhance synergistically the benefit of the composition in providing protection from the harmful effects of excessive exposure to sunlight. The composition of the invention can accordingly comprise from 0.1% to 10%, preferably from 1% to 5% by weight of an organic sunscreen material .

The composition according to the invention optionally can also comprise as a sunscreen ultrafine titanium dioxide in either of two forms, namely water-dispersible titanium dioxide and oil-dispersible titanium dioxide.

Water-dispersible titanium dioxide is ultrafine titanium dioxide, the particles of which are uncoated or which are coated with a material to impart a hydrophilic surface property to the particles. Examples of such materials include aluminium oxide and aluminium silicate. Oil-dispersible titanium dioxide is ultrafine titanium dioxide, the particles of which exhibit a hydrophobic surface property, and which, for this purpose, can be coated with metal soaps such as aluminium stearate, aluminium laurate or zinc stearate, or with organosilicone compounds.

By ^λΛultrafine titanium dioxide" is meant particles of titanium dioxide^' having an average particle size of less than 100 nm, preferably from 10 to 40 nm and most preferably from 15 to 25 nm.

By topical application to the skin of a mixture of both water-dispersible ultrafine titanium dioxide and oil- dispersible ultrafine titanium dioxide, synergistically enhanced protection of the skin against the harmful effects of both UV-A and UV-B rays is achievable.

It is believed that this unexpected benefit is due to the deposition of each type of titanium dioxide on different regions of the skin surface, water-dispersible titanium dioxide being preferentially retained by hydrophillic regions of the skin's surface, while oil-dispersible titanium dioxide is retained preferentially by hydrophobic regions of the skin's surface. The combined overall effect is that more efficient physical coverage of the skin's surface is attainable, and this can be demonstrated by measurement of the Sun Protection Factor (SPF) .

In order to achieve the enhanced, synergistic benefit, as herein described, the weight ratio of water-dispersible titanium dioxide to oil-dispersible titanium dioxide should be from 1:4 to 4:1, preferably from 1:2 to 1:2 and ideally about equal weight proportions.

The total amount of titanium dioxide that can optionally can be incorporated in the composition according to the invention is from 1% to 25%, preferably from 2 to 10% and ideally from 3% to 7% by weight of the composition.

The emulsion of the invention optionally can comprise an inorganic sunscreen in addition to ultrafine titanium dioxide as herein defined.

Examples of other inorganic sunscreens include:

- Zinc oxide, having an average particle size of from 1 to 300 nm,

- Iron oxide, having an average particle size of from 1 to 300 nm,

- Silica, such as fumed silica, having an average particle size of from 1 to 100 nm.

It should be noted that silica, when used as an ingredient in the emulsion according to the invention can provide protection from infra-red radiation.

A particularly convenient form of the composition according to the invention is an emulsion, in which case an oil or oily material will normally be present, together with an emulsifier to provide either a water-in-oil emulsion or an oil-in-water emulsion, depending largely on the average hydrophilic-lyophilic balance (HLB) of the emulsifier employed.

The composition according to the invention can optionally comprise one or more oils or other materials having the properties of an oil .

Examples of suitable oils include mineral oil and vegetable oils, and oil materials, such as those already proposed herein as emollients, such as those already proposed herein as emollients. Other oils or oily materials include silicone oils, both volatile and non-volatile, such as polydimethyl siloxanes .

The oil or oily material, when present for the purposes for forming an emulsion, will normally form up to 90%, preferably from 10 to 80% by volume of the composition.

The composition according to the invention can also optionally comprise one or more emulsifiers, the choice of which will normally determine whether a water-in-oil or an oil-in-water emulsion is formed.

When a water-in-oil emulsion is required, the chosen emulsifier or emulsifiers should normally have an average

HLB value of from 1 to 6. When an oil-in-water emulsion is required, a chosen emulsifier or emulsifiers should have an average HLB value of > 6.

It is to be understood that two or more emulsifiers can be employed if desired. The amount of emulsifier or mixtures thereof that optionally can be incorporated in the composition of the invention is from 1% to 50%, preferably from 2% to 20% and most preferably from 2% to 10% by weight of the composition.

The composition of the invention can also comprise water, usually up to 80%, preferably from 5% to 80% by volume.

If used, a suitable surfactant can be chosen from anionic, cationic, zwitterionic and amphoteric surfactants or their mixtures thereof. Anionic surfactants are especially preferred, and especially preferred is a soap. By the term soap is meant neutralised total fatty matter.

The composition of the invention can also optionally comprise a high molecular weight silicone surfactant which can also act as an emulsifier, in place of or in addition to the optional emulsifier (s) already mentioned.

The silicone surfactant is a high molecular weight polymer of dimethyl polysiloxane with polyoxyethylene and/or polyoxypropylene side chains having a molecular weight of from 10,000 to 50,000. A particularly preferred silicone surfactant is cyclomethicone and dimethicone copolyol, such as DC 3225C formulation aid available from Dow Corning. Another is lauryl ethicone copolyol, such as DC Q2-5200, also available from Dow Corning. The amount of silicone surfactant, when present in the composition will normally be up to 25%, preferably from 0.5% to 15% by weight of the emulsion.

The composition according to the invention optionally can also comprise retinol (vitamin A) and/or derivative thereof, further to enhance repair of photo damage to skin following exposure to ultra-violet light.

In addition to retinol itself, examples of derivatives of retinol include:

Retinyl acetate, retinyl butyrate, retinyl propionate, retinyl octanoate, retinyl laurate, retinyl palmitate, retinyl oleate and retinyl linoleate.

The amount of retinol, or a derivative thereof, when present in the composition according to the invention is from 0.01% to 10% and preferably 0.1% to 5% by weight of the composition.

The composition according to the invention optionally can also comprise a tocopherol (vitamin E group) , as an antioxidant for retinol, or a derivative, when present in the composition, and to limit oxidative damage to skin. The vitamin E group comprises alpha-tocopherol, beta-tocopherol, gamma-tocopherol and delta-tocopherol .

The amount of a tocopherol, when present in the composition according to the invention, is from 0.0001% to 20%, preferably from 0.001% to 10% by weight of the composition. Examples of conventional adjuncts which can optionally be employed include preservatives, such as para-hydroxy benzoate esters; antioxidants, such as butyl hydroxy toluene; humectants, such as glycerol, sorbitol, 2- pyrrolidone-5-carboxylate, dibutylphthalate, gelatin, polyethylene glycol, such as PEG 200-600; buffers, such as lactic acid together with a base such as triethanolamine or sodium hydroxide, waxes, such as beeswax, ozokerite wax, paraffin wax; plant extracts, such as aloe vera, cornflower, witch hazel, elderflower, cucumber; thickeners; activity enhancers; colourants; benefit agents like water soluble vitamins e.g. niacinamide and perfumes. Cosmetic adjuncts can form the balance of the composition.

The composition according to the invention is intended primarily as a product for topical application to human skin to prevent photo-damage to skin, which can result from exposure to sunlight, and which can retard natural skin ageing. The composition can also be used to reduce skin blotchiness and mottling due to hyperpigmentation, to improve skin texture with reduction in fine wrinkling and otherwise to improve skin colour and texture, as well as to moisturise the skin, and treat acne. In general, the composition, when topically applied to skin, is useful in the prevention of actinic damage to all epidermal cells and dermal tissue.

In use, a small quantity of the composition, for example from 1 to 5 ml, is applied to exposed areas of the skin, from a suitable container or applicator and, if necessary, it is then spread over and/or rubbed into the skin using the hand or fingers or a suitable device.

The topical skin treatment composition of the invention can be formulated as any leave on product like a cream, lotion, gel etc. The esters of the invention can also be incorporated in detergent compositions, especially toilet soaps, face washes etc. The composition can be packaged in a suitable container to suit its viscosity and product form and intended use by the consumer.

The invention is now illustrated by the following examples.

EXAMPLES

Preparation of tri-secondary-butyl citrate

57 g of citric acid was esterified using 570 g 2-butanol and p-toluene sulphonic acid as a catalyst at 110-120°C. After 60 hours, 2-butanol was recovered by distillation process, and the product was dissolved in hexane and washed with water at 30°C followed by 2% sodium bicarbonate solution. The overall yield of the product was 90%. The technical tri-secondary butyl citrate was almost 99% pure by GC.

Examples 1 and 2

The skin cream compositions of Examples 1 and 2, used for the study, are as presented in Table 1. The skin creams were prepared as follows. Water containing potassium hydroxide and glycerine was heated to 75 °C in a mixing vessel . Stearic acid and cetyl alcohol were also melted and heated to 75°C. Dimethicone, Isopropyl myristate, Octyl methoxy cinnamate, Butyl Methoxy Di-Benzoyl methane and suitable preservatives were added. The mixture was then added to the aqueous phase and mixed for 30 minutes. The mixture was then cooled to 60°C. The active was then added and mixed and the mixture cooled. Niacinamide was then added and thoroughly mixed. The mixture was then cooled to 40°C and the perfume was added followed by mixing for a further 15 minutes.

Table 1 :

The formulation of Examples 2 was stored under ambient conditions for 3 months. The formulations were tested for perfume stability as well as emulsion stability.

By perfume stability is meant that the perfume notes do not substantially change on storage and there are no off notes or undesirable odours. The perfume stability at the end of the three month period was determined by an expert perfumer. Table 2

The results of Table 2 show that the composition according to the invention shows acceptable perfume with no deterioration in quality even after storage.

Skin lightening studies

The skin lightening effect of the cream was determined. A clinical study was conducted with sixty women with a skin colour in the range between 6.5 to 7.5 (subjective scores). The cream was applied on the volar forearm, the other forearm was left untreated. The application was done twice daily for 8 weeks. At the end of a four week and eight week period, the colour was graded visually by an expert. The procedure was repeated on the lateral forearm. The results of the study are presented in Table 3 :

Table 3

The data in Table 3 shows that the esters of the invention are suitable skin lightening agents. In this experiment, the more negative the number, the better the skin lightening benefit.

Thus, the compositions according to the invention comprise suitable esters that do not show deterioration in perfume impact even on extended storage and also show skin lightening benefits.

Preparation of tri isopropyl citrate

200g of citric acid was esterified using 250g of isopropanol along with 940ml toluene as water scavenger and p-toluene sulphonic acid as catalyst under reflux at 120-125°C. After 16 hours reflux, an additional amount of isopropanol (31.3gms) was added to reaction mixture. The reaction was continued for 42 hours. Thereafter, the product was washed with water at 30 °C followed by washing with 2% sodium bicarbonate solution. Toluene was recovered by distillation. Tri-isopropyl citrate was then deodorized with dry stem sparging at 120 °C using 7-lOmm vacuum. The overall yield of the product was 91%. The tri-isopropyl citrate was determined to be 99% pure by gas chromatography.

Examples 3 - 6

Perfume Stability

The base composition shown in Table 1 (ie. minus the 3 grams of either tributyl citrate or tri-secondary butyl citrate) was used as the base composition in Examples 3 to 6, to which was added 3 grams of the citric acid ester. Each composition was filled in 30 gram collapsible tubes, capped and stored in constant temperature chambers (10°C, 30 °C and 45 °C) . The samples were examined initially and after 90 days of storage for pH, cohesive value (CV) and pefume impact .

Examples 3 and 6 are within the scope of the invention.

Cohesive value measurement :

A layer of 30 grams of cream is sandwiched between a circular disc hanging from a spring balance and a platform which can be moved downward at a constant rate . As the platform moves, the pull exerted by a spring balance increases until the layer of cream breaks . The reading at this point is the cohesion value recorded in grams.

Perfume impact :

Perfume impact was assessed by an expert perfumer organoleptically. Initial Stability

Stability After 3 Months

*Three-month stability for tri-butyl citrate and tri-ethyl citrate discontined because product not acceptable by perfumer after 1.5 months .

Example 7

Evaluation of efficacy of creams for anti-acne formulations;

The study was conducted with a group of 32 panelists who have mild-acne. The panelists applied 1 gram of the formulation on their face two times a day for 12 weeks. The number of blackheads and whiteheads (refered to as comedones) on the face was counted at the beginning of the study and at the end of 12 weeks of use of the formulation. The number of panelists who showed increased in the number of pustules over the course of the 12 weeks was also monitored. The study was conducted on a double-blind basis i.e. neither the panelists or the investigators were aware of the contents of the formulations used.

The data indicate that the composition as per the invention (Example-B) gives vastly improved anti-acne efficacy both in terms of comedone and pustule formation.

Claims

1. A skin care cosmetic composition comprising:

(a) an amount from 0.01 to 20% by weight of one or more esters of citric acid having the following structure (1)

where Ri is chosen from one of tri-secondarybutylcitrate, tri-isopropyl citrate, tri-lauroyl citrate or their mixtures thereof; and

(b) from 10 to 99.9% by weight of an acceptable vehicle for the citric acid.

2. A skin care cosmetic composition according to Claim 1 wherein the composition additionally comprises a sunscreen .

3. A skin care cosmetic composition according to Claim 2 wherein the sunscreen is an organic sunscreen.

4. A skin care cosmetic composition according to Claim 3 wherein the organic sunscreen is present at a level of

0.1% to 10% by weight of the composition.

5. A skin care cosmetic composition according to any of Claims 2 to 4 wherein the sunscreen is oil dispersible or water dispersible titanium dioxide or mixtures thereof.

6. A skin care cosmetic composition according to Claim 5 wherein the titanium dioxide has a particle size of less than 100 nm.

7. A skin care cosmetic composition according to Claim 5 or Claim 6 wherein the titanium dioxide is coated with aluminium oxide or aluminium silicate.

8. A skin care cosmetic composition according to Claim 5 or Claim 6 wherein the titanium dioxide is coated with metal soaps selected from aluminium stearate, aluminium laurate, zinc stearate and organosilicone compounds.

9. A skin care cosmetic composition according to any one of Claims 5 to 8 wherein the ratio of water-dispersible titanium dioxide to oil-dispersible titanium dioxide is from 1:4 to 4:1.

10. A skin care cosmetic composition according to any one of Claims 5 to 8 wherein the ratio of water-dispersible titanium dioxide to oil-dispersible titanium dioxide is about 1:1.

11. A skin care cosmetic composition according to any one of Claims 5 to 10 wherein the total amount of titanium dioxide is from 1% to 25% by weight of the composition.

12. A skin care cosmetic composition according to Claim 11 wherein the total amount of titanium dioxide is from 3% to 7% by weight of the composition.

13. A skin care cosmetic composition according to any preceding claim wherein the ester of citric acid is present at a level of 0.1% to 10% by weight of the composition.

14. A skin care cosmetic composition according to Claim 13 wherein the ester of citric acid is present at a level of 0.1% to 5% by weight of the composition.

15. A skin care cosmetic composition according to any preceding claim wherein the acceptable vehicle is selected from liquid or solid emollients, solvents, humectants, thickeners and powders.

16. A skin care cosmetic composition according to Claim 15 wherein the acceptable vehicle is 50% to 99% by weight of the composition.

17. A skin care cosmetic composition according to any of the preceding claims wherein the composition additionally comprises skin benefit materials selected from oils or oily materials, emulsifiers, water, surfactants, silicone surfactants, retinol or retinol derivatives and tocopherol .

18. A method of manufacturing a composition according to any of claims 1 to 17, comprising esterifying citric acid with one of 2-butanol, isopropyl alcohol and lauroyl alcohol in the presence of a catalyst selected from p- toluene, sulphonic acid, phosphotungstic acid, ferric chloride, ferric ammonium sulphate and zirconium oxide.

19. A method according to claim 18, including adding magnesium sulphate to the mixture to act as a water scavenger.

20. A cosmetic method of providing at least skin care benefit selected from repairing, reducing and prevention of photodamage, skin lightening, moisturisation and treatment of acne, comprising applying to the skin a composition according to any of claims 1 to 17

21. A cosmetic of treating acne comprising applying to the skin a topical composition comprising

(a) an effective amount of a triester of citric acid having the structure (II)

O

CH₂ -C 0 R

O

R₄ 0 -C C - 0 - R² (II)

I O

¹ '

CH₂ -C - 0 - R wherein

1 2 3 R , R and R each independently represent a branched or unbranched alkyl, alkenyl, aryl, alkylaryl or arylalkyl group, each said group being optionally substituted and having from 1 to 18 carbon atoms, ₄ R represents -H , or a branched or unbranched saturated or unsaturated acyl, alkyl, aryl, alkylaryl or arylalkyl group, each said group being optionally substituted and having from 1 to 18 carbon atoms; and b) a cosmetically acceptable vehicle for the citric acid ester.

22. A cosmetic method according to claim 21 wherein the citric acid ester is tri-secondary butyl citrate, tri- isopropyl citrate or tri-lauroyl citrate, or mixtures thereof.

23. Use of a triester of citric acid having the structure

(II) .

O

II

CH₂ -C - 0 - R¹

I ° I ||

R₄ O -C C - O - R² (II)

I

I o I II CH₂ -C - 0 - R³ wherein

1 2 3 R , R and R each independently represent a branched or unbranched alkyl, alkenyl, aryl, alkylaryl or arylalkyl group, each said group being optionally substituted and having from 1 to 18 carbon atoms, ₄

R represents -H , or a branched or unbranched saturated or unsaturated acyl, alkyl, aryl, alkylaryl or arylalkyl group, each said group being optionally substituted and having from 1 to 18 carbon atoms for the manufacture of a medicament for the treatment of acne .

24. Use according to Claim 23 wherein the citric acid ester is tri-secondary butyl citrate, tri-isopropyl citrate or tri-lauroyl citrate, or mixtures thereof.