WO2006117055A1

WO2006117055A1 - Skin lightening composition comprising a conjugated linoleic acid and niacinamide

Info

Publication number: WO2006117055A1
Application number: PCT/EP2006/003261
Authority: WO
Inventors: Jayashree Anand; Mridula Kini; Lalitagauri Rajwade; Ramesh Surianarayanan
Original assignee: Unilever Plc; Unilever Nv; Hindustan Unilever Limited
Priority date: 2005-05-03
Filing date: 2006-03-30
Publication date: 2006-11-09
Also published as: CN101170990B; TW200716191A; EP1888015A1; JP2008540350A; CN101170990A

Abstract

A cosmetic skin lightening composition comprising: (i) 0.01 to 10% by weight of a conjugated linoleic acid and/or its derivatives; and (ii) 0.1 to 10% by- weight niacinamide .

Description

SKIN LIGHTENING COMPOSITION COMPRISING A CONJUGATED LINOLEIC ACID AND NIACINAMIDE

Technical Field

The present invention relates to novel cosmetic compositions. In particular, the present invention relates to a novel skin lightening cosmetic composition.

Background and prior art

Cosmetics are used all over the world and this is a reflection of the inherent natural desire of human beings to look more beautiful and presentable than they actually are. Cosmetics are also used to retain and preserve the youth and appearance of skin in an attempt to overcome physical disfiguration owing to the inevitable natural process of aging. They are also used to conceal and/or remedy conditions like acne, excessive perspiration and body-malodor and provide benefits like anti-aging, anti-cellulite activity, sebum-reduction and/or suppression, oil-control, moisturizing, skin lightening and protection from UV radiation.

Skin color is a feature, which is largely determined by our genetic constitution and to some extent is related to the local geographical conditions. Westerners have very fair skin, whereas people of Negroid race, on the other hand, have dark colored skin. Some people have an intermediate skin color, which is commonly referred to as "wheatish". It is generally known that color of skin is directly proportional to the extent of a pigment "melanin" present in it and melanin is believed to be a natural defense against harmful solar ultra violet radiation. Although melanin offers the above mentioned protection, a lighter skin color is generally perceived to equate with beauty and hence it is a much- desired physical attribute, especially amongst people with wheatish and darker skin color.

Active ingredients and preparations, which counteract skin pigmentation, thereby causing skin lightening, are known. Products, which have been used in practice, are based on hydroquinone, kojic acid, ascorbic acid and azelaic acid and their derivatives. On the one hand, these actives become effective only after several weeks of continued use and on the other hand, unduly long use of such products containing some of these actives may sometimes be unacceptable for toxicological reasons. Some vitamins like vitamin C and vitamin B₆ are also known to effect skin lightening. Niacinamide is also a well-known skin lightening agent and there are several patents that cover various topical formulations of niacinamide, their methods of applications and uses, some of which are referenced herein.

US 4 096 240 (Lever Brothers Company, 1978) describes a cosmetic composition for topical application to human skin containing niacinamide, or a precursor thereof, for lightening the skin, together with an ultra-violet absorbing sunscreen to protect against sunburn or suntan. Preferably more than one sunscreen is employed to provide for protection over a wide UV spectrum.

It has also been reported that niacinamide delivers synergistic skin lightening benefits in combination with other actives.

EP 396 422 (Unilever et al, 1990) discloses a skin lightening composition, comprising niacinamide, dibenzoyl methane and cinnamate sunscreens, as well as silicone oil in the skin lightening composition. The composition gives enhanced skin lightening.

Another well-known skin lightening agent is conjugated linoleic acid and its cosmetically acceptable derivatives. This molecule has also been widely reported in patented formulations claiming various cosmetic benefits, which include inter-alia skin lightening.

US 6 403 064 (Unilever et al, 2002) describes a topical composition comprising conjugated linoleic acid, and/or its' derivatives wherein at least 1 % by weight of the conjugated linoleic acid is present as the trans-10-cis-12 isomer. It is reported that this product is particularly suitable for lightening human skin.

US 6 287 553 (Unilever et al, 2002) relates to a topical composition and cosmetic method for treating skin conditions including wrinkling, sagging, photodamaged skin, sensitive skin, dry skin, flaky skin, red skin, irritated skin, itchy skin and age spots. This composition comprises conjugated linoleic acid or derivatives thereof in which at least 50% by weight of the conjugated linoleic acid is present as the cis-9-trans-11 isomer.

In addition, various combinations of conjugated linoleic acid with other known actives such as ascorbic acid derivatives, retinyl esters, phenolic compounds have been reported for various cosmetic benefits, which include wrinkling, sagging, photodamaged skin, sensitive skin, dry skin, flaky skin, red skin, irritated skin, itchy skin and age spots. Although the prior art describes various cosmetic compositions of niacinamide and conjugated linoleic acid, no attempt had been made in the past to combine the beneficial effects of these two molecules. The present inventors have surprisingly found that effective skin lightening benefits may be obtained through the application of cosmetic compositions to the skin, which comprise conjugated linoleic acid and/or derivatives thereof and niacinamide. The present inventors have developed a novel, synergistic cosmetic composition that efficiently provides benefits far superior to the benefits provided by each of these actives individually, thereby providing the user with a superior multi-active cosmetic composition. While doing so, the essential attributes of the cosmetic composition that include skin-feel, absorbability and ease of spreading have not been compromised upon.

Summary of the invention

According to the present invention there is provided an improved cosmetic composition comprising.

(a) 0.01 to 10% by weight an isomer of conjugated linoleic acid or its' derivatives and

(b) 0.1 to 10% by weight niacinamide

According to a preferred aspect of the present invention there is provided an improved cosmetic composition comprising

(b) 0.1 to 10% by weight niacinamide Wherein said isomer of conjugated linoleic acid and said niacinamide are present at a ratio in the range of 1 :30 to 30:1 parts by weight.

According to a further preferred aspect of the present invention there is provided an improved cosmetic composition comprising (c) 0.01 to 10% by weight an isomer of conjugated linoleic acid or its' derivatives, wherein said isomer is selected from cis-9-trans-11 and trans-10-cis-12 isomers and (d) 0.1 to 10% by weight niacinamide -A-

The invention will now be described in detail with the help of appended description and examples.

Detailed description

Melanin is a bio-polymer pigment synthesized by special dendritic cells known as melanocytes residing mostly between the basal cells of the epidermis. The biochemical process responsible for the production of melanin is caused by the action of an enzyme called tyrosinase, which triggers a cascade of biosynthesis. According to reported sources, melanin is the end product of an oxidative process in which tyrosine is converted with the aid of the enzyme tyrosinase via 3,4-dihydroxyphenylalanine (dopa), dopaquinone, leucodopachrome, dopachrome, 5,6-dihydroxyindole and indole-5, 6- quinone to give, finally, melanin. The exact mechanism of melanin biosynthesis, however is a very complex process. Exposure to sunlight or other UV radiation can stimulate the melanocytes to produce more melanin, hence the so-called "tanning" reaction.

Normal pigmentation of the skin surface is uniform. Localized, excessive pigmentation can occur and such coloration is collectively referred to as hyperpigmentation, which encompasses a wide array of afflictions, all of which are accompanied by increased melanin production. Hyperpigmentation of the human skin may include skin blemishes or disorders including freckles, senile lentigo, liver spots, melasma, brown or age spots, sunburn pigmentation, post-inflammatory hyperpigmentation due to abrasion, bums, wounds, insect bites, dermatitis, and other similar small, fixed pigmented lesions.

Skin lightening is highly desired in instances where people wish to lighten the natural color of their skin or wish to eliminate or minimize hyperpigmentation. From a cosmetic standpoint, it may often be desirable to decolorize what is considered normally pigmented skin to increase "fairness" or to blend hyperpigmented regions into that of the surrounding normal skin.

Many synthetic and natural ingredients have been used in the past to lighten the natural color of skin. The present inventors have identified that a combination of niacinamide and an isomer of conjugated linoleic acid or its derivatives surprisingly act synergistically and provide superior skin lightening benefits. Niacinamide is the amide of niacin or nicotinic acid and is also known as nicotinamide, nicotinic acid amide, pyridine-3-carboxylic acid amide and vitamin B₃. Its chemical structure is represented below.

The amount of niacinamide in the present composition can range from 0.1% to 10%, preferably from 0.1 to about 5% and more preferably from 0.1 % to 2.0% by weight of the composition.

Conjugated linoleic acid (hereinafter also referred to as CLA) comprises a group of positional and geometric isomers of linoleic acid in which various configurations of cis and trans double bonds at positions (6, 8), (7, 9), (8, 10), (9, 11), (10, 12) or (11, 13) are possible. Each positional isomer can have 4 geometrical isomers. For example in the case of the (6,8) isomer, there can be cis-6-cis-8, cis-6-trans-8, trans-6-cis-8 and trans-6-trans-8 geometrical isomers. Similarly there can be 4 geometrical isomers for the remaining 5 positional isomers. Thus twenty- four different isomers of the CLA can exist.

CLA is different from "linoleic acid". Linoleic acid is a straight chain fatty acid, chemically referred to as cis-9, cis-12-octadecadienoic acid. In the case of linoleic acid the two double bonds are not in conjugation. Molecular structure of linoleic acid is represented as

Whereas trans-10-cis-12-CLA has the following structure.

Thus it can be seen that conjugated linoleic acid is structurally different from linoleic acid.

The level of CLA in the present invention can range from 0.01% to 10, preferably 0.01% to 5% and more preferably 0.1 to 2% by weight of the composition. It is also possible to use a combination of two or more isomers of CLA and such combinations are within the scope of the present invention. Among all positional and geometrical isomers of CLA, the ones, which are particularly preferred, are cis-9-trans-11 and trans-10-cis-12 isomers.

The invention also includes cosmetically acceptable derivatives of the free acid which thus comprise conjugated linoleic acid moieties. Preferable derivatives include those derived from substitution of the carboxyl group of the acid, such as esters (e.g. retinyl esters, triglyceride esters, monoglyceride esters, diglyceride esters, phosphoesters), amides (eg ceramide derivatives), salts (e.g. alkali metal and alkali earth metal salts, ammonium salts); and/or those derived from substitution of the C18 carbon chain, such as alpha hydroxy and/or beta hydroxy derivatives.

In the case of triglyceride ester derivatives, all positional isomers of CLA substituents on the glycerol backbone are included. The triglycerides must contain at least one CLA moiety. For example, of the three esterifiable positions on the glycerol backbone, the 1 and 2 positions may be esterified with

CLA and by another lipid at position 3 or as an alternative, the glycerol backbone could be esterified by CLA at the 1 and 3 positions with another lipid at position 2. Wherever the term "conjugated linoleic acid" or "CLA" is used in this specification it is to be understood that the derivatives thereof comprising CLA moieties are also included.

It is also possible to use a combination of free conjugated linoleic acid and its derivatives and such combinations are within the scope of the present invention.

In the composition of the present invention, the isomer of conjugated linoleic acid and niacinamide are present at a relative ratio in the range of 1:30 to 30:1 parts by weight, preferably 1:15 to 15:1 parts by weight and more preferably 1 :6 to 6:1 parts by weight. Optional Skin Benefit Materials and Cosmetic Adjuncts

The composition may additionally comprise materials commonly employed in skin care products such as liquid or solid emollients, silicone oils, emulsifiers, solvents, humectants, thickeners, powders, sunscreens, skin lightening agents, propellants other specific skin-benefit actives. The vehicle may also further include adjuncts such as antioxidants, perfumes, opacifiers, preservatives, colorants and buffers.

A safe and effective amount of sunscreen may be used in the compositions of the subject invention. The composition preferably comprises from 0. 1 % to 10%, more preferably from 0.1 % to 5 %, of a sunscreen agent, which amounts may be wholly either organic or inorganic sunscreen or combinations thereof. The organic sunscreens are preferably chosen from 4-tertiary-butyl-4'- methoxy dibenzoylmethane, available under the trade name Parsol 1789 (Givaudan) or 2- ethylhexyl methoxycinnamate, available under the trade name Parsol MCX (Givaudan) or mixtures of the two sunscreen compounds. Inorganic sunscreens, which may be employed are for example titanium dioxide, zinc oxide or silica such as fumed silica and mixtures thereof. These are preferably in the micronized form. Ultrafine titanium dioxide in either of its two forms, namely water-dispersible titanium dioxide and oil-dispersible titanium dioxide, may be suitable for the invention. Water- dispersible titanium dioxide is ultra-fine titanium dioxide, the particles of which are non-coated 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 "ultrafine or micronized form" is meant particles of inorganic sunscreens having an average particle size of less than 100 μ, preferably 70 μ or less, more preferably less than 40 μ and most preferably from 15 μ to 25 μ.

Other vitamins, which act as skin-lightening ingredients can be advantageously included in the composition to provide for additional skin lightening effects. These include vitamin B₆, vitamin C, vitamin A or their precursors and cosmetically acceptable derivatives. Mixtures of the vitamins can also be employed in the composition of the invention. When present, these vitamins are used in the range of 0.01 to 10.0% by weight of said composition. 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 palpitate, silicone oils such as dimethylpolysiloxane, di-n-butyl sebacate, isopropyl myristate, isopropyl palmitate, isopropyl stearate, butyl stearate, polyethylene glycol, Methylene glycol, lanolin, cocoa butter, corn oil, cotton seed oil, olive oil, palm kernel oil, rape seed 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, tetraalkyl 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; plant extracts such as those from genus Rubia, Symplocus, Curcuma and various perfume/fragrance ingredients may also be included in the composition at ranges from 0.001 to 40.0% by weight of the composition.

Cosmetically Acceptable Carriers, Product Preparation and Form

The composition used according to the invention comprises a dermatologically/cosmetically acceptable vehicle to act as a carrier for the actives. The composition may be in the form of conventional skin-care products, which include creams, gels or lotions and mousses. The composition can also be in the form of a so- called wash-off product for example a bath or shower gel or liquid soap, possibly containing a delivery system for the actives to promote adherence to the skin during rinsing. More preferably the product is a leave-on product, that is to say, a product to be applied to the skin without a deliberate rinsing step soon after its application to the skin. A stearic acid-potassium stearate based vanishing cream based carrier is highly preferred. The vehicle will usually form about 25% to 99.0% by weight of the composition, and can, in the absence of other cosmetic adjuncts, form the balance of the composition.

To prepare the topical composition used in the method of the present invention, the usual manner of preparing skin care products may be employed. The active components are generally incorporated in a dermatologically/cosmetically acceptable earner in a conventional manner. The active components can suitably first be dissolved or dispersed in a portion of the water or another solvent or liquid to be incorporated in the composition. The preferred compositions are oil-in-water or water- in- oil or water-in-oil-in-water emulsions.

The invention will now be described with the help of the following examples. It should however, be understood that the examples cited herein are for illustrative purpose only and to describe the working of the invention. These examples should not be construed so as to limit the scope of the present invention in any manner.

Examples

Table 1 : Formulation of a vanishing cream comprising niacinamide and conjugated linoleic acid.

Legend:

Parsol MCX is 2-ethylhexyl methoxycinnamate (Giavudan)

Parsol 1789 is 4-tertiary-butyl-4'-methoxy dibenzoylmethane (Givaudan) DC 200 is polydimethyl siloxane fluid (350 cSt) (Dow Corning Corporation) MT 100Z is micronized titanium dioxide (size 15nm) (Tayka Corporation, Japan) Clarinol A-80 is mixture of fatty acids high in conjugated linoleic acid containing predominantly cis-9-trans-11 and trans-10-cis-12 isomers (Lodders Croklaan, Netherlands).

The vanishing cream was prepared in the following manner.

Glycerin and potassium hydroxide were added to water and this mixture was heated to 70⁰C to form a water phase. A mixture of stearic acid, cetyl alcohol and isopropyl myristate were heated to 70⁰C to form the oil phase and Parsol MCX, Parsol 1789, DC

200 and MT 100Z were added to this phase under agitation, using a homogenizer. These two phases were mixed for 30 minutes. This mixture was gradually cooled to 55°C while agitating. To this mixture Clarinol A80 and niacinamide were added and mixing was continued for a further 15 minutes. The mixture was further cooled to room temperature and perfume, color and other minor additives were added to the composition.

The formulations (A to D) were tested for their efficacy as regards "skin lightening" benefits. Said benefits were ascertained by employing a panel of human volunteers in the manner described below.

Demonstration of skin lightening benefit/synergy:

The control (A) and other test compositions (B, C, and D) were prepared in the manner described above. These compositions were used to test their skin lightening benefits on a panel of 5 human volunteers having uniform skin color.

The initial skin color of the inner side of their forearms was determined visually by a trained expert and was allotted a score from 1 (fairest) to 10 (darkest). The compositions (A to D) were applied to the inner side of their forearms by trained applicators at pre-designated sites. At the end of 50 repeated applications (5 applications per day at 2.5 hour intervals with no washing cycle) on both the arms the change in skin color of the treated sites was recorded again by the trained expert over a period of 3-11 days. The difference between the initial skin color score and final score where base formulation A (placebo) and formulations B to D were applied are indicative of the efficacy of the formulation. A negative value indicates lightening and positive value indicates darkening, with respect to the initial skin color.

Results

Results of the panel experiments are presented in the table-2 below.

Table-2

A higher negative score indicates fairer skin (skin lightening) over the base. It is evident from the data in table 2 that product D of the invention provides synergistic skin lightening benefit agents as compared to the products B and C which contain only one of the skin lightening actives. Therefore, enhanced skin lightening benefits of the composition of the present invention is demonstrated.

Claims

Claims:

1. A cosmetic skin lightening composition comprising: (i) 0.01 to 10% by weight an isomer of conjugated linoleic acid and/or its derivatives; and (ii) 0.1 to 10% by weight niacinamide.

2. The cosmetic skin lightening composition as claimed in claim 1 wherein said isomer of conjugated linoleic acid and said niacinamide are present at a ratio in the range of

1 :30 to 30: 1 parts by weight.

3. The cosmetic skin lightening composition as claimed in claim 1 or claim 2 wherein said isomer of conjugated linoleic acid and said niacinamide are present at a ratio in the range of 1 :15 to 15:1 parts by weight.

4. The cosmetic skin lightening composition as claimed in any of the preceding claims 1 to 3 wherein said isomer is selected from "cis-9, trans-11" and "trans-10, cis-12" isomers of conjugated linoleic acid.

5. A cosmetic skin lightening composition as claimed in any of the preceding claims wherein said composition comprises 0.01 to 10% by weight sunscreens selected from organic or inorganic sunscreens.

6. A cosmetic skin lightening composition as claimed in claim 5 wherein said organic sunscreen is selected from 4-tertiary-butyl-4'-methoxy dibenzoylmethane and 2- ethylhexyl methoxycinnamate.

7. Use of a cosmetic skin lightening composition according to anyone of the preceding claims for skin lightening.

8. A consumer article comprising:

(a) a cosmetic skin lightening composition in accordance with any one of the claims 1 to 6;

(b) a package for delivering the aforesaid cosmetic skin-lightening composition to an individual; and (c) instructions teaching an individual to apply the aforesaid cosmetic skin lightening composition to the skin of an individual for skin lightening.