WO2001070190A2

WO2001070190A2 - Cosmetic compositions

Info

Publication number: WO2001070190A2
Application number: PCT/EP2001/002736
Authority: WO
Inventors: Govindarajan Raman; Pushker Sona; Ramesh Surianarayanan; Sushama Shripad Wagh
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2000-03-23
Filing date: 2001-03-09
Publication date: 2001-09-27
Also published as: WO2001070190A3; AU2001256202A1; AR027981A1

Abstract

Cosmetic compositions are described which comprise a skin lightening agent (such as niacinamide) or a precursor thereof and titanium dioxide particles having a particle size of less than 100 nm. The compositions are useful in lightening the colour of skin and in inhibiting or preventing the tanning of skin.

Description

COSMETIC COMPOSITIONS

The present invention relates to cosmetic compositions for lightening skin colour. In particular, the compositions of the invention are directed for topical application to human skin to provide lightening of skin colour .

Melanin is synthesised by melanocytes, a cell type present at dermis-epidermis junction, from an ammo acid tyrosine. Tyrosine is acted upon by an enzyme tyrosmase which is the key enzyme in melanogenesis . There have been several reports wherein inhibitors of tyrosmase such as hydroquinone and its derivatives, mercaptoammes, alpha hydroxy acids and others have been used in cosmetic compositions to regulate the skin pigmentation. However only some of these are reversible and non-toxic.

The conventional skin lightening compositions are based on sunscreens which maintain skin colour against ultra violet (u.v.) light and have been based on materials which absorb incident ultra violet light of the wavelength which produces the tanning of the skin. Other approaches have been to use niac /niacmamide or other skin lightening agents which are believed to control dispersion of melanosomes or inhibit tyrosmase. Sunscreens alone can not lighten the skin beyond the natural skin colour, and their action on the skin is only to reduce the ingress of incident u.v. into the skin, and are therefore effective only during the day. Some of the compounds used as skin lightening agents are also known to be toxic. GB 1533119, discloses the 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 silicone compound to synergistically enhance the skin lightening benefit 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 very small particle size. This grade of titanium dioxide designated as ultrafine Tι0 , affords a good degree of sun blocking potential without causing any skin lightening effect.

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

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

The applicants have found that a synergistic composition comprising titanium dioxide with a particle size less than 100 nm enhances the anti-tanning benefit of the composition and skin lightening efficacy of niacinamide. It was found that for obtaining the synergy in skin lightening it is essential to use titanium dioxide with a particle size less than lOOnm.

Accordingly, in a first aspect the present invention relates to a cosmetic skin lightening composition comprising a skin lightening agent or a precursor thereof (preferably m an amount of from 0.1% to 10% by weight) and titanium dioxide with a particle size less than lOOnm (preferably in an amount of from 0.1 to 5% by weight) .

In another aspect, the invention provides the use of a composition according to the invention in a cosmetic method for lightening the colour of skin.

In a further aspect, the invention provides a cosmetic method of treating skin which comprises applying to the skin a composition according to the invention.

A yet further aspect of the invention is the use of a composition according to the invention in the manufacture of a sunscreen.

Also provided by the invention is a method of reducing or preventing the tanning of skin which comprises applying to the skin a composition according to the invention .

The composition of the invention comprises a skin lightening agent or a precursor thereof and titanium dioxide with a particle size less than 100 nm. Preferably, the composition further comprises from 0.1 to 10% by weight of at least one organic sunscreen.

The preferred skm lightening agent is niacinamide or a precursor thereof.

Therefore, a preferred aspect of the present invention relates to a cosmetic skm lightening composition comprising 0.1% to 10% by weight of niacinamide or a precursor thereof and 0.1 to 5% by weight titanium dioxide with a particle size less than 100 nm.

A more preferred aspect of the invention is a cosmetic skm lightening composition comprising 0.1% to 10% by weight of niacinamide or a precursor thereof; 0.1 to 5% by weight titanium dioxide with particle size less than 100 nm; and 0.1 to 10 % by weight of at least one organic sunscreen.

The skm lightening caused by the composition of the invention is reversible and without any side effects. The composition according to the invention would be active both during the day and the night unlike sunscreens, which can act only during the day.

The skm lightening agent may be chosen from niacinamide or a precursor thereof, polyammo acid sequences with pi in the range 2 to 5.5, extracts of placenta, hydroqumone and derivatives (eg. arbutm) , kojic acid, dicarboxylic acids (eg, azelaic acid, sebacic acid) represented by the formula HOOC-(C_xH_y)- COOH where C_xH_y is alkylene, alkenylene or alkynylene, optionally substituted, x=4 to 20 and y=6 to 40, ascorbic acid and derivatives thereof, hydroxy acids (eg, lactic acid, glycolic acid, malic acid, tartaric acid etc), ferulic acid, retinol and derivatives. The amino acids forming the polyamino acid sequence can be naturally occurring or synthetic, dextro or levo form, and the polyamino acid sequence can be straight chain or cyclised with a molecular weight of 200-20000. Any of the other known skin lightening agents such as those obtained from plants or fungi etc. may also be employed.

The organic sunscreens used in the composition according to the invention may, for example, 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, 2-phenyl-benzimidazole-5-sulphonic acid and others known in the art or any other suitable mixtures thereof.

The titanium dioxide may be selected from micronised, surface treated, hydrophilically or hydrophobically, powder form or predispersed. It is preferred that the average particle size of the titanium dioxide used according to the invention is less than 100 nm and, preferably, more than 50% of the particles (more preferably more than 75%) have an average particle size less than 100 nm. The composition according to the invention can include cosmetically compatible carriers, preservatives, emulsifiers, thickeners, perfume and colour. Skin benefit materials such as moisturisers, emollients and anti-ageing compounds can also be used.

The vehicle which forms part of the cosmetic composition comprises one or more substances which are cosmetically acceptable in that they will not harm the skin. 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, propellants, solvents, humectants and thickeners, for example polyols, glycerol, cetyl alcohol, esters, carbopol 934, ethoxylated castor oil, paraffin oils, lanolin and its derivatives, etc.

Silicone compounds such as silicone surfactants and/or silicone based emollients can be used optionally in the composition.

The compositions according to the invention can be prepared for topical application to the skin in the form of conventional products such as lotions, powders, creams, ointments, sticks, aerosol and cleansing products .

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 : Example 1 The compositions tested for anti-tanning and skin lightening are presented in Table 1. Table 1 includes a composition comprising conventional actives but without titanium dioxide (Comparative Example 1) and a composition with micronised titanium dioxide (Example 1) -

Table 1

In vivo studies on anti tanning:

Fifteen subjects with non-hairy forearms and even skin color tone were selected. The test samples (Comparative Example and Example 1) were applied on the forearm and marked out clearly. The sample application was repeated on three consecutive days (Day 1, 2 &3) followed by sun exposure on the treated sites along with an untreated control site. Tanned spots are visually evaluated on the scale of 0 to 8 on the 5th and 10th day.

A ratio of Tan protection Index was calculated using a formula :

Tan Protection Index = { [ (Mean tan score at the unprotected site ) - ( Mean tan score at the treated site) ] / (mean tan score at the unprotected site ) } . Tan protection Index (TPI) of a formulation gives its efficacy compared to an untreated exposed site and a formulation that has a TPI of one is expected to give 100% protection against tan. The data taken on day 5 and 10 are presented in Table 2.

Table 2

The data presented shows that the anti-tanning effect obtained by the use of micronised titanium dioxide along with niacinamide is significantly superior even when the total level of the sunscreen in the composition was reduced. This shows that titanium dioxide acts synergistically in improving the antitanning effect.

Mean tan score is evaluated on the following scale NO DIFFERENCE 0

VISIBLE CHANGE IN THE AREA (FUZZY) 0.25

SLIGHTLY TANNED 0.5 SLIGHTLY TANNED WITH BOUNDARY 1.0

MODERATELY TANNED (Copper tan) 1.5

SLIGHTLY DARK 2.0

DARK 3.0

MORE DARK 4.0 EXTREMELY DARK 5.0 EXTREMELY DARK WITH REDDENING (burn / irritation) 6.0

EXTREMELY DARK WITH WRINKLED TEXTURE 7.0

EXTREMELY DARK ASSOCIATED WITH PEELING 8.0

In vivo skin lightening studies:

A panel of members with a skin colour range between subjective scores of 6.5 and 7.5 were selected for the study. They were divided into 2 groups and were given cream compositions according to the Comparative Example or Example 1. The volunteers applied the assigned cream (0.75 g) on one of their forearms leaving the other forearm untreated. This was done twice daily for 8 weeks. This was a blind study and the extent of reduction in skin colour was visually evaluated by an expert at the end of 8 weeks and data is presented in Table 3.

Table 3 Table 3

The data shows that the extent of skin lightening produced by Example 2 is significantly superior as compared to Example 1 although the level of the skin lightening agent (niacinamide) is the same in both the samples. This shows that the titanium dioxide has a significant role in enhancing the skin lightening benefit of niacinamide.

Claims

1. Cosmetic composition comprising a skin lightening agent or a precursor thereof and titanium dioxide particles having a particle size of less than 100 nm.

2. Composition as claimed in Claim 1, wherein the skin lightening agent is present in an amount of from 0.1 to 10% by weight.

3. Composition as claimed in Claim 1 or Claim 2, wherein the titanium dioxide is present in an amount of from 0.1 to 5% by weight.

4. Composition as claimed in any one of Claims 1 to 3, further comprising from 0.1 to 10% by weight of at least one organic sunscreen.

5. Composition as claimed in Claim 4, wherein the organic sunscreen is selected from 4- ertiary-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, 2-phenyl-benzimidazole-5-sulphonic acid and mixtures thereof.

6. Composition as claimed in any one of Claims 1 to 5, wherein the skin lightening agent is selected from niacinamide or a precursor thereof, polyamino acid sequences with pi in the range 2 to 5.5, extracts of placenta, hydroquinone and derivatives (eg. arbutin) , kojic acid, dicarboxylic acids (eg, azelaic acid, sebacic acid) represented by the formula HOOC- (C_xH_y) -

COOH where C_xH_y is alkylene, alkenylene or alkynylene, optionally substituted and x=4 to 20 and y=6 to 40, ascorbic acid and derivatives thereof, hydroxy acids, ferulic acid, retinol and its derivatives, and mixtures thereof.

7. Composition as claimed in Claim 6, wherein the skin lightening agent is niacinamide or a precursor thereof.

8. Composition as claimed in any one of Claims 1 to 7 which is in a form suitable for topical application to human skin.

9. Use of a composition according to any one of Claims 1 to 8 in a cosmetic method for lightening the colour of skin.

10. Use as claimed in Claim 9, wherein the skin is living human skin.

11. A cosmetic method of treating skin which comprises applying to the skin a composition according to any one of Claims 1 to 8.

12. Use of a composition according to any one of Claims 1 to 8 in the manufacture of a sunscreen.

13. A method of reducing or preventing the tanning of skin which comprises applying to the skin a composition according to any one of Claims 1 to 8.