MXPA00007102A - Skin and hair darkening composition - Google Patents

Abstract

A cosmetic skin/hair darkening composition for topical application to skin and/or hair is provided that comprises from 0.1 to 10%by weight of a peptide having an isoelectric point ranging from 6 to 11.

Description

COMPOSITION FOR DARING SKIN AND HAIR DESCRIPTION OF THE INVENTION The present invention relates to a cosmetic composition for darkening of the skin and / or hair. The invention also relates to a method for locally applying to the skin and / or hair a composition for darkening the skin / hair according to the invention. Tanning the skin by exposure to UV rays is a well-known phenomenon. However, it is also well known from the literature that such exposure to UV radiation results in accelerated skin development and increases the incidence of skin cancer. Consequently, alternative ways of tanning the skin have been developed. It is currently known in the art to use dihydr oxyacetone (DHA) as an aid for tanning not induced by UV rays. However, undesirably, the use of dihydroxy to cetane for purposes of tanning the skin rather produces an appearance of unnatural tanning. In addition, the artificial tan produced by DHA does not protect against UV radiation as a natural tan would.

Melanin is the black pigment of hair and skin and is synthesized from the amino acid tyrosine by melanosomes. Melanosomes are organelles found in melanocytes, a type of cell present at the confluence of rmi s - ep i e mi s. The enzyme thryokinase acts on tyrosine which is the main stage in melanogenesis. In melanosomes melanin is synthesized from monomers and transferred to neighboring cells called keratinocytes. The keratinocytes divide and differentiate and thus transport the melanosome to the surface of the skin. The intensity of skin color is directly related to the number, size, melanin content, speed of formation and migration / transfer of melanosomes to keratinocytes. Various specific sequences of amyloid and peptide residues are known to inhibit melanin pigmentation and have a bleaching effect on the skin (JP 6345797, JP 6321757, JP 6321755, JP 5170636, US 5,126,327). The peptides described in the prior art comprise a high proportion of basic and hydrophobic amino acids and have isoelectric point (pl) values greater than 5.5. These are mainly used to clarify the hyperpigmented areas associated with abnormal skin conditions. Applicants in their co-pending British patent application 9719195.1, describe a cosmetic composition for skin lightening comprising from 0.1 to 10% by weight of peptide with an isoelectric point of between 2 and 5.5. the isoelectric point (pl) is defined as the pH at which the net charge on a molecule is zero. Peptides that have a large number of acidic amino acids such as glutamic acid, aspartic acid, etc., have a low pl and those that have basic amino acids such as lysine, arginine, histidine, have a high pl. Applicants have found that a composition comprising peptide sequences having an isoelectric point (pl) of between 6 and 11 are capable of obscuring the skin / hair. Accordingly, the present invention relates to a cosmetic skin / hair darkening composition comprising from 0.1% to 10% by weight of a peptide with an isoelectric point (pl) ranging from 6.0 to 11.

The skin / hair darkening effected by the composition of the invention is reversible and without any side effects. The composition according to the invention is activated during the day and night. The peptide is a sequence of amino acids and is of a molecular weight ranging from 200 to 20,000 daltons (Da) with a pl ranging from 6.0 to 11.0. The peptide also optionally binds to a hydrophobic amino acid or to a target molecule or vehicle. The amino acid residues that form the peptide sequence can be presented naturally or synthetically, in the dextro or levo form, and include any derivative thereof. The peptide sequence must comprise a ratio of 1 basic amino acids such that the resulting peptide is basic in nature. The peptide sequence may be straight chain or cyclic. The molecular weight of the peptide sequence varies from 200 to 20,000 Da and preferably from 200 to 2000 Da. The pl of the peptide sequence varies from 6.0 to 11.0.

The hydrophobic amino acid can be selected from either alanine, isoleucine, leucine, methionine, phenylalanine, proline, tryptophan or valine and is preferably tryptophan. The target molecule is preferably a peptide and more preferably a hexapeptide which preferably has the primary sequence aspargine-glutamine-proline-leucine-1 eu-cyanide, and is located within the 27 amino acid residue from the carboxy terminus of the active peptide. Target vehicles such as micelle-and / or inverted micelles can also be used. According to a preferred aspect of the invention there is provided a cosmetic darkening composition for skin / hair comprising 0.5 to 5.0% by weight of the peptide. The invention further relates to a cosmetic method of darkening the skin / hair comprising the local application to the skin and / or hair of a composition according to the invention. The composition may also comprise a skin bronzing agent. This bronzing agent can be chosen from any known agent for this purpose such as dihydroxy acetone, theophylline, copper gluconate, natural active ingredients obtained from P t e r a n c t s a n t a l i n u s, and any other skin tanning agents. The composition according to the invention may also comprise a cosmetically compatible carrier. They may also comprise preservatives, emulsifiers, thickeners, perfume, color, skin benefit materials such as moisturizing emulsions, emollients and a n t i in ve j e c im e n t o. The vehicle which forms part of the cosmetic composition is one or more substances which are compatible with the sequence of po 1 i ami n or a c i do and which is also cosmetically acceptable in that it will not damage the skin / hair. The vehicles that can be used in the composition according to the invention can include absorbent powders, binders, and carriers, and liquids such as emollients, propellants, solvents, humectants and thickeners. Simple carriers such as alcohol, PEG, propylene glycol can also be used. Examples of humidification and humectants include polyols, glycerol, cetyl alcohol, carbopol 934, ethoxylated castor oil, paraffin oils, lanolin and their derivatives. Silicone compounds such as silicone surfactants such as DC3225C (Dow Corning) and / or silicone emollients, silicone oil (DC-200 Ex-Dow Corning) can also be used. The compositions according to the invention can be prepared for local application to the skin / hair in the form of simple solutions or conventional application or washing products such as lotions, creams, ointments, shampoos and / or aerosol products. All percentages referred to herein and in the appended claims are by weight of the composition unless indicated as c o n t r a r i o. The invention will now be illustrated by means of Examples. The Examples are for illustration only and do not restrict the scope of the invention in any way.

EXAMPLE 1 Demonstrated n_ in vi tro of the improvement in the formation of melanin The influence of a peptide sequence with pl 11.0 on the formation of melanin at pH 5 in an in vi tro system, compared to the pH of the system, was analyzed. melanosomal The test conditions for the formation of melanin under conditions i n vi t r o are as follows.

Test Method The test control mixture contains 5 μmoles of DL-DOPA (Dihydroxy phenyl alanine), 20 nmoles of lysozyme and 3.2 units of tyrosinase in acetate buffer pH 5.0 in a test tube. A unit is defined as the amount of tyrosinase needed to convert one nmol of DOPA in one minute. In the experimental set, 11 nmol of polylysine, a poly amino acid sequence with pl 11.0, were used, in addition to other ingredients as defined in the control. The formed melanin was washed with the acetates regulator, the IN sodium hydroxide was suspended and dissolved by heating the sample at 60 ° C for 5 minutes. The absorbance was measured at 400 nm.

Table 1 Sample Melanin formed A 400 Control 0.120 In the presence of polylysine 0.168 The above results show that the polylysine sequence production of melanin is significantly improved. The invention will now be illustrated by reference to the following example of a cosmetic cream.

The application of the cosmetic cream described in the Comparative Example and Example 2 will show that the product described in Example 2 will be significantly superior in darkening of the skin to that of the Comparative Example. It is therefore possible by means of the present invention to provide a composition for darkening the skin / hair which is reversible and without any side effects. The composition is active during the day and night. The numbers in the table represent percentages of the composition by weight.

E x p e 3 Demonstration in vi trode the improvement of the formation of e_l ariina_ The influence of the sequence of poly-amino acid with pol ig ut to pl 2.5, polyarginine (pl 0.9) or polylysine (pl 11.0) in the formation of melanin at pH 5 in an in vi t ro system, comparable to the pH of the melanosomal system, was analyzed. The test conditions for the formation of melanin under conditions i n vi t r o are normal.

Test method: The test control mixture contains 5 mmoles of DL-DOPA (Dihydroxy phenylalanine), lysozyme 20 nmol and 0.45mg of tyrosinase in acetate buffer pH 5.0 in a test tube. In the experimental set, 18 nmol of the poly glutamate were used, as well as a sequence of po 1 i ami noá ci do with pl 2.5 or polyarginine pl 10.9 or polylysine pl 11.0 in addition to the other ingredients as defined in the control. The formed melanin was washed with the regulator, suspended in IN sodium hydroxide and dissolved by heating the sample at 60 ° C for 5 minutes. The absorbance was measured at 400 nm.

Table 2 Sample Melanin formed A 400 Control 0.120 In the presence of polyglutamate pl 3-4 0.048 In the presence of polylysine pl 11.0 0.168 In the presence of polyarginine pl 10.9 0.182 The above results show that in the presence of the sequence of po 1 i ami no acid with alkaline pl or p > 5.0 the production of melanin is significantly increased while in the presence of the sequence of po 1 i amino acid with pl in the acid range does not achieve a similar improvement in melanin production. Example 4 Demonstration of the improvement of ^. melanin formation _ _ _ Twelve female volunteers were chosen with a level skin tone and no scars / visible hair on the forearms. On the palmar side of the forearm, 1 cm squared sites were marked using a template. A mixture of peptides of molecular weight reaching 14 K daltons, having a pl 11.2 at a concentration of 2% in a suitable vehicle was used. The previous solution contains 0.3 μg of protein / μl and 5ml of it was applied for 10 days. The (vehicle) without treatment and placebo served as control. The sites were graduated by an expert, who was blinded to treatment assignments, on day zero and on the eleventh day. The data presented in table 3 show that even under conditions i n v i vo peptides with a pl > 5.0 darkened the skin significantly compared to the two controls, ie the untreated and the vehicle. The critical difference is 0.12. . - - - - Registration for the Expert Evaluation: SUBSTANTIALLY CLARIFIED -1.0 SUBSTANTIALLY DARK +1.0 DEFINITELY CLARIFIED -0.75 DEFINITELY DARKLY +0.75 MODERATELY CLARIFIED -0.5 MODERATELY OSCURECIDA +0.5 SLIGHTLY CLARIFIED -0.25 SLIGHTLY DARK +0.25 NO DIFFERENCE 0

Claims (9)

1. Cosmetic composition for darkening the skin and / or hair comprising from 0.1 to 10% by weight of a peptide having an isoelectric point ranging from 6 to 11.

2. Cosmetic composition according to claim 1, which is applied locally to the skin and / or hair.

3. Cosmetic composition according to the rei indication 1 or 2, wherein the peptide has a molecular weight of 200 to 20,000 Da.

4. Cosmetic composition according to any preceding claim wherein the peptide is linked to either: a) a hydrophobic amino acid selected from alanine, isoleucine, leucine, methionine, phenylalanine, valine, proline and tryptophan; or b) an objective molecule or vehicle.

5. Cosmetic composition according to claim 4, wherein the hydrophobic amino acid is tryptophan.

6. Cosmetic composition according to claim 4 or 5 wherein the target molecule is a peptide.

7. Cosmetic composition according to claim 4, wherein the target molecule is a hexapeptide having the primary sequence (I): (I) Asx-Glm-Por-Leu-Leu-Thr

8. Cosmetic composition according to the rei indication 4, wherein the target vehicle is a micelle or inverse micelle.

9. Cosmetic method of skin / hair darkening comprising the local application to the skin / hair of a composition according to any of the preceding expressions.