EP2167022A1

EP2167022A1 - Improved cosmetic composition for skin lightening

Info

Publication number: EP2167022A1
Application number: EP08761408A
Authority: EP
Inventors: Jayashree Anand; Lalitagauri Rajwade; Vibhav Ramrao Sanzgiri; Simone Dosu Sethna
Original assignee: Unilever PLC; Unilever NV
Current assignee: Unilever PLC; Unilever NV
Priority date: 2007-07-05
Filing date: 2008-07-01
Publication date: 2010-03-31
Also published as: MX2010000271A; CN101686913A; WO2009003996A1

Abstract

A cosmetic skin lightening composition is described that includes 0.1-10% by weight of a skin lightening agent, 0.1-5% by weight of titanium dioxide having a primary particle size greater than 300 up to 1000 nm and a cosmetically acceptable vehicle.

Description

IMPROVED COSMETIC COMPOSITION FOR SKIN LIGHTENING

Technical Field

The present invention relates to cosmetic skin lightening composition and in particular to a skin lightening composition that delivers immediate improvements in skin appearance by providing enhanced instant brightness/glow along with the effects of lightening the skin.

Background and Related Art

It is known that ultra-violet radiation from the sun can cause acute adverse effects such as aging of skin and skin burns.

A tan is essentially the skins' way of increasing its defence against the onslaught of damaging ultra-violet. Tanning protects against sun damage principally by increasing the melanin content of the epidermis. Although more skin pigmentation improves sun protection, intentional UV induced tanning does not necessarily achieve an increase in protective pigmentation as an ultra-violet protective strategy.

It is well known that light radiation of wavelengths of from 280 nm to 400 nm promotes tanning of the human epidermis, and that irradiation of wavelengths of from 280 to 320 nm, i.e., UV-B, causes erythema and burning of the skin.

Melanin which is basically responsible for skin pigmentation is synthesised by melanocytes, a cell type present at dermis-epidermis junction, from an amino acid tyrosine. Tyrosine is acted upon by an enzyme tyrosinase which is the key enzyme in melanogenesis.

The conventional skin lightening compositions are based on sunscreens which maintain skin colour against the ultra-violet light. They have been based on materials which absorb/block incident ultra-violet light of the wavelength which produces the tanning of the skin. Other approaches have been to use niacin/niacinamide or other skin lightening agents which are believed to control dispersion of melanosomes or inhibit tyrosinase. Sunscreens alone cannot lighten the skin significantly and their action on the skin is only to reduce the ingress of incident ultra-violet into the skin and is therefore effective only during the day.

GB 1 533 1 19 discloses a combination of niacinamide and a suitable mixture of UV absorbers which absorb in the UV range of 290 nm to 360 nm. IN 169917 discloses the use of a silicone compound to synergistically enhance skin lightening benefits obtained from the combination of niacinamide and sunscreens.

Certain inorganic substances have also been proposed for use as sunscreens which physically block exposure of the skin to ultra-violet rays. Important among these is titanium dioxide having a very small particle size. This grade of titanium dioxide, designated as ultrafine TiO₂, affords a good degree of sun blocking potential without causing any biological skin lightening effect.

IN 172889 discloses the use of titanium dioxide at levels from 3% along with octyl methoxy cinnamate to provide protection from excessive exposure to ultra-violet rays over a broad range of wavelengths in the UV-A and UV-B regions.

US 5 997 887 and US 5 997 890 disclose topical compositions comprising pigmentary grade particulate material such as titanium dioxide, with a particle size greater than 100nm to about 300nm along with an active vitamin B₃ useful for imparting an essentially immediate visual improvement in skin appearance.

Accordingly, an object of the present invention is to provide a cosmetic skin lightening composition that delivers immediate improvements in skin appearance by providing enhanced instant glow along with enhanced effects of lightening the skin.

It is another object of the present invention to provide a synergistic skin lightening composition using titanium dioxide with a particle size that is not a sunscreen, does not penetrate the skin and is not a known skin lightening agent. Summary of the Invention

Now we have found a composition including titanium dioxide with a primary particle size in the range greater than 300 nm and up to 1000 nm that synergistically enhances skin lightening efficacy of skin lightening agents while delivering immediate improvements in skin appearance by providing an enhanced instant glow. The effects obtained on skin lightening is particularly surprising as titanium dioxide with a primary particle size range of greater than 300 nm and up to 1000 nm is not a sunscreen, does not penetrate the skin and is not a known skin lightening agent.

Accordingly, the present invention relates to a cosmetic skin lightening composition including 0.1% to 10% by weight of one or more of skin lightening agent or a precursor thereof and 0.1 to 5% titanium dioxide with a primary particle size greater than 300 up to 1000 nm in a cosmetically acceptable vehicle.

The particle size mentioned for the purposes of the present invention is as measured by the Mac-View particle size distribution (electron microscopy) method (Mountech Co. Ltd.)

According to a preferred aspect, the present invention relates to a cosmetic skin lightening composition comprising 0.1 % to 10% by weight of skin lightening agents selected from vitamins B₃, B₆, B₁₂, C, E, A, D, K, or mixtures thereof, and 0.1 to 5% titanium dioxide with a primary particle size greater than 300 up to 1000 nm in a cosmetically acceptable vehicle. The term "vitamins" as detailed above and in the claims includes their precursors, salts and esters.

According to a more preferred aspect of the invention there is provided a cosmetic skin lightening composition as set forth hereinabove comprising 0.1 to 10 % by weight of at least one organic sunscreen.

It is particularly preferred that the invention composition additionally comprises 0.05% to 5% by weight ultra fine titanium dioxide with a particle size in the range 1 -100 nm.

Detailed Description of the Invention

The skin lightening caused by the composition of the invention is reversible and without any side effects. The composition according to the invention is active both during - A -

the day and the night unlike sunscreens which can act only during the day and on both the photoexposed and non-photoexposed part of the skin.

Skin lightening agents: It is preferred that the skin lightening agent according to the invention is vitamin B₃ or a derivative thereof and is selected from the group consisting of niacinamide, nicotinic acid esters, non-vasodilating esters of nicotinic acid, nicotinyl amino acids, nicotinyl alcohol esters of carboxylic acids, nicotinic acid N-oxide, niacinamide N-oxide and mixtures thereof.

Other skin lightening vitamins like vitamin B₆, vitamin B₁₂, vitamin C, vitamin E, vitamin A, vitamin D, vitamin K, or their precursors/salts/esters/derivatives can be advantageously included in the composition to provide for synergistic skin lightening effects. Still other skin lightening agents useful to be incorporated in the composition are polyamino acid sequences with pi in the range 2 to 5.5, and the amino acid forming the polyamino acid sequence can be naturally occurring or synthetic, dextro or levo form, straight chain or cyclised with a molecular weight of 200-20000, hydroquinone and derivatives (eg. arbutin), kojic acid, dicarboxylic acids represented by the formula HOOC-(CxHy)-COOH where x=4 to 20 and y=6 to 40, such as azelaic acid, sebacic acid, oxalic acid, succinic acid, fumaric acid, octadecenedioic acid or their salts or a mixture thereof, hydroxy acids (e.g. lactic acid, glycolic acid, malic acid, tartaric acid) or their salts or a mixture thereof, a phenolic acid which is ferulic acid, salicylic acid, kojic acid or their salts or a mixture thereof, retinol and derivatives. Any of the other known skin lightening agents such as those obtained from plant or mushroom etc. may also be employed.

The skin lightening agent is employed at a concentration in the range from 0.1 % to 10%, preferably from 0.1 to 5%, more preferably from 0.2 to 1.5%, optimally from 0.3 to 1% by weight of the composition.

Organic sunscreens:

The organic sunscreens used in the composition according to the invention may be selected from 4-tertiary butyl-4'-methoxy dibenzoylmethane, octyl methoxy cinnamate, benzophenone-3, benzophenone-4, benzophenone-8, diethanolamine methoxy cinnamate, ethyl dihydroxypropyl para amino benzoic acid, glyceryl PABA, homosalate, methyl anthranilate, salicylate, ethylhexyl 2-phenyl-benzimidazole-5-sulphonic acid and others known in the art or any other suitable mixtures thereof.

The preferred organic sunscreens used in the composition according to the invention may be selected from 4-tertiary butyl-4'-methoxy dibenzoylmethane, octyl methoxy cinnamate or suitable mixtures thereof.

It is preferred to use the organic sunscreens at a concentration in the range from 0.1 to 10 %, preferably from 0.5 to 8%, more preferably from 1 to 5% by weight of the composition.

Titanium dioxide:

The titanium dioxide may be selected from surface untreated, surface treated, hydrophilically or hydrophobically, powder form or predispersed or a mixture thereof. The preferred primary particle size of titanium dioxide used according to the invention is greater than 300 up to 1000 nm. It is preferred that the primary particle size is in the range 310-750 nm. The particle size mentioned for the purposes of the present invention is as measured by the Mac-View particle size distribution (electron microscopy) method.

It is particularly preferred that the composition additionally comprises 0.1 to 5% (preferably 0.2 to 0.8%) by weight of the composition of ultra fine or micronised titanium dioxide with a particle size in the range 1-100nm, preferably 1-50nm and more preferably 5-25nm. The micronised titanium dioxide is especially preferred. This has been found to give additional skin lightening benefits.

Cosmetically Acceptable Vehicle:

The vehicle which forms part of the cosmetic composition is one or more substances which are cosmetically acceptable in that they will not harm the skin. Cosmetic compositions to deliver different benefit agents are prepared using different emulsifying systems and vehicles. The vehicles that can be used in the compositions according to the invention can include powder absorbents, binders and carriers, and liquids such as emollients, emulsifiers, propellants, solvents, humectants (e.g polyols, glycerol), thickeners (e.g. Carbopol 934), cetyl alcohol, esters, ethoxylated castor oil, paraffin oils, lanolin and its derivatives, fragrances, colourants and mixtures thereof. The compositions according to the invention for topical application to the skin can be in the form of conventional products such as lotions, powders, creams, ointments, sticks, aerosol and cleansing products.

It is preferred that the vehicle is a vanishing cream base which comprises 5-25%, preferably 8-22%, more preferably 10-20%, and optimally 12-20% by weight Ci₂-C₂₀ fatty acids and 0.1-10%, preferably 1-5% and optimally 1.5-4% by weight Ci₂-C₂₀ fatty acid soap. Vanishing cream base is one of the preferred forms of such a cosmetically acceptable vehicle and gives a desirable matt feel to the skin.

The cosmetic skin lightening composition in the form of a cream is prepared using the conventional process used for making oil-in-water emulsions. The titanium dioxide with a particle size greater than 300 up to 1000 nm according to the invention is preferably added during the emulsion process and more preferably is added mid way through the emulsion process.

The invention will now be illustrated by way of examples. The examples are for illustration only and do not in any way restrict the scope of the invention.

Examples: i. Effect on skin lightening:

A human volunteer study was conducted by testing various compositions on 50 volunteers of Type IV to V skin (Fitzpatrick scale) who were screened and selected to have a similar kind of skin pigmentation. In all studies conducted, the compositions had niacinamide purchased from Veer Chemie Ltd., Hyderabad, India as the skin lightening agent, the inorganic sunscreen used was titanium dioxide with an average particle size of 15 nm sold by Tayca Corporation under the trade name MT100Z. The titanium dioxide with an average particle size of 400 nm sold by Tayca Corporation under the trade name MP40 was used in the experiments to test the efficacy of the formulations in accordance with the invention.

The various compositions according to the invention and the respective controls were prepared in a vanishing cream base and the composition details are presented in table 1. The process used to manufacture the cream was a standard process used for oil-in-water emulsions where the water phase containing the polyol and preservatives was heated and alkali was added to it. The molten oil phase containing the fatty acid, fatty alcohol, etc. was then charged into the water phase in 2 parts - the first led to the formation of the soap and the second part formed the actual emulsion.

To achieve a proper emulsion, the batch was repeatedly passed through a homogenizer until a smooth emulsion was formed. Titanium dioxide with an average particle size of 15 nm and the titanium dioxide with an average particle size of 400 nm were added during the emulsion process. Once the emulsion was formed, it was slowly cooled and niacinamide was added at around 40-50⁰C followed by other heat-labile ingredients including other actives. All the ingredients were gently mixed under vacuum and the batch was de-aerated prior to perfume addition.

The sample cream was applied at a concentration of 2 mg/cm² to areas marked on the volar forearm of the individual volunteers and corresponding untreated areas were maintained for comparison. The volar forearm is chosen to minimise the effect of the sun and study the effect of the biological skin lightening. Cream was applied twice per day. The marked out areas were assessed over a period of 4 weeks without the presence of the cream to assess the biological skin lightening and the data presented is at the end of the period. The assessment was done by an expert panel on a colour scale considering the difference between the treated and untreated area of the forearms, and is presented as the extent of skin lightening in the table 1 that follows.

Table 1

The skin lightening scores presented in table 1 show that increasing the concentration of 15 nm titanium dioxide alone does not significantly improve the skin lightening scores and even a combination of enhanced levels of niacinamide, the skin lightening agent, and the 15nm titanium dioxide gives a marginal improvement in skin lightening benefit.

However, addition of 400nm titanium dioxide significantly improved the skin lightening benefit as compared to the lower levels of the combination of niacinamide and 15nm titanium dioxide as well as three times the level of these ingredients. Given the fact that titanium dioxide uncoated and with a particle size of 400 nm is not a sunscreen, that material with a particle size of 400 nm does not penetrate the skin and it is not a known skin lightening agent, the data shows that 400nm titanium dioxide has a unique synergistic effect on the skin lightening benefits provided by niacinamide.

i: Effect on Skin Brightness and Glow:

The sample cream according to example 1 that did not contain any titanium dioxide with a particle size of 400 nm and example 3 that contained 0.3% titanium dioxide with a particle size of 400 nm as described in table 1 was applied at a concentration of 2 mg/cm² to areas marked on the volar forearm of the individual volunteers. Volunteers and the expert panel members were asked to score the brightness of the skin and glow on the skin immediately after application of the cream and also after the composition had completely dried on the skin. Percentage members who stated that composition of example 3, "makes my skin bright" was 93% and "makes my skin glow" was 91%.

ii. Correlation between Consumer Data and Instrumental Analysis: The compositions presented in table 2 below, were attested by a human volunteer study as described above and the assessment done by an expert panel on a colour scale considering the difference between the treated and untreated as the extent of skin lightening was recorded and the same was also measured using a Minolta chromometer. These devices are based on the measurement of chromophore content like melanin, haemoglobin and deposited pigments etc. which contribute to skin colour. According to the Commission Internationale de I'Eclairage (CIE) the colour space is represented by L^* = black to white and indicate the degree of skin lightening. The data is presented in table 3. For scores provided by the panel more negative will show lighter skin and for the L^* value measured using the Minolta chromometer the data is positive and higher value will indicate lighter skin colour.

Table 2

Table 3

All values after accounting for untreated control.

The data presented in table 3 show that at both 4 weeks and 8 weeks there is significant benefit in skin lightening as indicated by the panel score and instrument scores. Moreover as both visual assessment and instrumental evaluation were done on clean skin without any product applied, it shows that the lightening effect seen on the skin is not due to a cosmetic cover-up but rather the effect is biological in nature and is seen even without any product application.

iii. Effect of particle size:

Compositions using 1.25% niacinamide along with MP40 titanium dioxide with a particle size in the range 400 nm and another set with 3.5% niacinamide and 100 - 300 nm particle size titanium dioxide were assessed in a human volunteer study as described above and the data are presented in table 4.

Table 4

aAvailable from the Proctor and Gamble Company. Contains 3.5% w/w niacinamide and 1.4% w/w TiO₂ of particle size 100-300nm.

The data presented in table 4 shows that incorporation of titanium dioxide of 400 nm particle size gave significantly superior benefit over use of prior art composition with titanium dioxide of 100-300 nm particle size. It is significant to note that this superior benefit was obtained even when the level of skin lightening agent and the titanium dioxide level was significantly lower in the composition according to the invention as compared to the prior art formulation.

Claims

1. A cosmetic skin lightening composition comprising: i. 0.1 % to 10% by weight of a skin lightening agent; ii. 0.1 % to 5% by weight of titanium dioxide having a primary particle size greater than 300 nm up to 1000 nm; and iii. a cosmetically acceptable vehicle.

2. A cosmetic skin lightening composition as claimed in claim 1 wherein said particle size is from 310 nm to 750 nm.

3. A cosmetic skin lightening composition as claimed in claim 1 or claim 2 wherein said skin lightening agent is selected from the group consisting of vitamins B₃, B₆, B₁₂, C, E, A, D, K, and mixtures thereof.

4. A cosmetic skin lightening composition as claimed in claim 3 wherein the skin lightening agent is vitamin B₃.

5. A cosmetic skin lightening composition as claimed in any one of the preceding claims wherein the composition comprises 0.1 to 10 % by weight of at least one organic sunscreen.

6. A cosmetic skin lightening composition as claimed in claim 5 wherein the organic sunscreen is selected from the group consisting of 4-tertiary butyl-4'-methoxy dibenzoylmethane, octyl methoxy cinnamate, ethylhexyl salicylate and mixtures thereof.

7. A cosmetic skin lightening composition as claimed in any one of the preceding claims additionally comprising titanium dioxide with a particle size in the range 1- 100 nm.

8. A cosmetic skin lightening composition as claimed in claim 7 wherein the titanium dioxide is micronised.

9. A cosmetic skin lightening composition as claimed in any one of the preceding claims wherein the cosmetically acceptable vehicle comprises 5-25% by weight C- 12-C20 fatty acids.

10. A cosmetic skin lightening composition as claimed in claim 9 wherein said vehicle comprises 12-20% by weight Ci₂-C₂O fatty acids and 0.1-10% by weight Ci₂-C₂₀ fatty acid soap.