MXPA01006117A - Sunscreen composition - Google Patents

Abstract

A topical cosmetic sunscreen composition comprising (a) from 0.1 to 10%by weight of the composition of an ultra-violet radiation absorbing sunscreen dissolved in an oil;and (b) a cosmetically acceptable vehicle. A process for preparing such a composition is also described. The inventive composition has improved sunscreen efficacy.

Description

SOLAR BLOCK COMPOSITION TECHNICAL FIELD OF THE INVENTION The present invention relates to an improved sunscreen cosmetic composition for topical application to human skin to provide enhanced protection from sunlight and a process for preparing it.

BACKGROUND AND PRIOR ART Melanin is the black pigment synthesized by the action of the tyrosinase enzyme in the amino acid tyrosine. The reaction takes place in organelles called melanosomes contained within cells called melanocytes. The melanocytes transfer melanosomes with melanin to neighboring keratinocytes, which host these organelles until they are diffused from the body from the superficial layers of the skin. The intensity of skin color is directly related to the number, size, melanin content, the rate of formation and transfer of melanosomes to keratinocytes. Melanin is also an important protector of skin and tissues below the skin, as it has the ability to absorb incident ultraviolet light. The UV range is divided into three regions, UV-A, having a wavelength from about 320 to 400 nm, which gives a tanning effect without inflammation; UV-B, having a wavelength from approximately 290-320 nm, which is responsible for erythema (sunburn) and eventually tanning; and UV-C, having a wavelength of about 200-290 nm, normally absorbed by the ozone layer in the earth's atmosphere, but which is potentially very damaging to the skin. Melanogenesis and skin pigmentation are closely related responses for UV light irradiation. The photobiological changes that cause erythema also lead to melanogenesis and increased pigmentation. Hence, exposure to sunlight leads to darkening of the skin by immediate darkening of already formed melanin pigment, and also by the formation of new melanin. Many of the skin compositions are formulated for the purpose of maintaining skin color against darkening following exposure to ultraviolet light. These compositions have been based on materials that deflect and disperse the incident ultraviolet light of the wavelength that produces burns and tanning of the skin or which absorb this light. To prevent the darkening of existing melanin and the formation of new melanin, the skin has to be protected widely through the UV-A range from about 320-400 nm. We have found that by careful selection of sunscreens, we can protect the skin against radiation obscuring effects. GB 1 370 236 discloses a skin lightening composition containing niacin and the method by which it clears the skin is by retarding the dispersion or distribution of melanin towards the epidermis.

GB 1 533 1 1 9 discloses that niacinamide is useful as a skin lightening agent without causing skin redness reaction due to vasodilatation of blood vessels, which is frequently associated with niacin. GB 22301 86 discloses that the addition of a silicone compound to the composition containing a mixture of sunscreen and niacinamide improves the coverage of the cream on the skin for improved protection against UV light. Applicants have found that the protection of the skin against UV light by compositions containing sunscreens is intensified when the sunblock is dissolved in an oil phase. More specifically, applicants have found that the use of the oil phase blocker has improved sunblock efficacy than that which can be obtained otherwise by using the blocker at substantially higher levels. In this way, the amount of blocker required to achieve the same UV protection is reduced by the present invention. Accordingly, the present invention provides a topical sunscreen cosmetic composition, comprising from (i) 0.1 to 10% by weight of the composition of a sunscreen absorber of ultraviolet radiation dissolved in an oil; and (ii) a cosmetically acceptable vehicle. The composition is preferably obtained by the process below provided by the present invention.

The present invention also provides a process for the preparation of a sunscreen cosmetic composition, comprising the steps of: (i) dissolving 0.1 to 10% by weight of the composition of a sunscreen absorber of ultraviolet radiation in an oil phase; (ii) neutralizing stearic acid in an aqueous phase; and (iii) homogenizing the dissolved sunblock with the neutralized stearic acid and a cosmetically acceptable vehicle. The dissolved sunblock can be homogenized with the neutralized stearic acid and can subsequently be mixed with the vehicle (and other ingredients) of the composition. However, it is preferable for the neutralized stearic acid and vehicle to be mixed together and the dissolved sunscreen subsequently added to the mixture since it has been found that this gives a composition with an optimum sunscreen effect. Preferably, the stearic acid is neutralized with an alkali, such as potassium hydroxide. It is preferred that before step (ii), the stearic acid is melted at a temperature above 70 ° C. The sunscreen is chosen, preferably, from 4-butyl tertiary-4'-methoxy dibenzoylmethane, available under the tradename PARSOL 1789 ex Givaudan, 2-ethyl hexyl methoxy cinnamate, available under the tradename PARSOL MCX ex Givaudan or mixtures thereof. the two sun block compounds. The composition comprises 0.1 to 10% by weight of the composition and preferably 0.1 to 5% by weight of the composition of a solar blocking compound.

The oil can be mineral oil, vegetable oil or any other source, but preferably it is in the liquid state at temperatures higher than 20 ° C. The oil can be selected from mineral oil, peanut oil, sunflower oil, safflower oil, sesame oil or mixtures thereof. But if the preferred process is used, where the sun blockers are dissolved in the oil phase and these are subsequently added to the neutralized stearic acid and vehicles mixed in the water phase, then the oil does not need to be one that is in the liquid state at temperatures per above 20 ° C. Suitable oils in these circumstances include isopropyl myristate. In one embodiment, the stearic acid is first melted at 70 ° C and then neutralized with aqueous potassium hydroxide to which the sunscreen dissolved in oil is added after the emulsion has cooled to a temperature of less than 50 ° C. . This emulsion forms the basis for all other ingredients. All other ingredients can be homogenized with the base. In a preferred embodiment, these other ingredients are mixed with stearic acid / aqueous phase before homogenization with the sunscreen / oil phase. The composition of the invention may optionally comprise from 0.1 to 10%, preferably 0.5 to 5% by weight of one or more skin bleaching agents. The skin bleaching agent is preferably chosen from niacin, niacinamide or a precursor thereof which is capable of releasing niacinamide on the skin. Nianeamide is the niacin medium and is also known as nicotinamide or pyridine-3-carboxylic acid. An example of a compound, which is a precursor of niacinamide is niacinamide ascorbate. Other suitable skin bleaching agents include placenta extracts, hydroquinone and derivatives (eg, arbutin), kojic acid, dicarboxylic acids (azelaic acid, sebacic acid), represented by the formula HOOC- (CxHy) -COOH, where x = 4 to 20 and y = 6 to 40, ascorbic acid and derivatives thereof, hydroxy acids (lactic acid, glycolic acid, malic acid, tartaric acid, etc.), ferulic acid, retinol and derivatives or other known skin bleaching compounds. The vehicle forming part of the cosmetic composition is one or more substances, which are mutually compatible with the blocker and if present, the bleaching agent of the skin, and do not damage the skin. The vehicle can act as a diluent, dispersant or carrier for the other ingredients of the composition, and therefore, aims to ensure that they can be easily applied to, and can be distributed uniformly over, the skin at an appropriate concentration. Vehicles that can be used in the compositions according to the invention can include water, absorbers, binders and carriers in powder, and liquids such as emollients, propellants, solvents, humectants and thickeners. The compositions according to the invention can be prepared for topical application to the skin in the form of conventional product types, such as creams, lotions, ointments and aerosol products.

The invention is further illustrated by reference to the following examples.

EXAMPLES Example 1: Process for preparing the composition according to the invention: 60 g of water were heated together with 0.48 g of potassium hydroxide at 70 ° C in the main mixer. 1 6 g of stearic acid, 4.4 g of isopropyl palmitate, 0.1 5 g of propyl paraben at 70 ° C were heated in a side pot and added to the main mixer, mixing well. To this, other conventional ingredients, 1 g of niacinamide, perfume and water were added and mixed well. The mixture was cooled to 30 ° C and 0.4 g of Parsol 1789 and 1.2 g of Parsol MCX dissolved in 2 g of mineral oil were homogenized with the remainder of the formulation.

Conventional process: 60 g of water and 0.48 g of potassium hydroxide were taken in the main mixer. 16 g of stearic acid, 0.1 5 g of propyl paraben, 0.2 g of silicone and 4.4 g of isopropyl palmitate were mixed and heated to 70 ° C in a side container, and in a portion of this mixture 0.4 of Parsol was dissolved. 1 789 and 1 .2 ge Parsol MCX. Both mixtures were added to the main mixer under stirring and mixed well. Other conventional ingredients, 1 g of niacinamide, perfume, water to be taken to 100 g were added and mixed well by stirring.

Example 2: Spreading and delivery of sunblocks on the skin: The forearms of 1 5 volunteers were washed with a soap and the surface was patted dry and the cream was applied half an hour later to ensure a proper and uniform drying of the forearms . Areas of 2 cm x 3 cm each were marked, using a template. 30 mg of cream was applied using a glass bar with the proper care to spread it only within the marks. The impressions of the experimental regions were taken individually using a cellophane tape from a dispenser with sufficient care not to stain the surfaces. The tapes were placed in a frame. The different treatments were as follows.

Example 2a: Cream not containing sunscreen or niacin (placebo) Example 2b: Creams prepared by the conventional process described above, where the sunscreens (Parsol 1789 at 0.4% and Parsol MCX were at 1.2% by weight of the composition ) and the level of niacinam ida was 1.0%. Example 2c: Creams prepared as in Example 2b, but containing twice the level of sunblock (Parsol 1789 at 0.8% and Parsol MCX at 2.4% by weight of the composition) and niacinamide at 2.0%. Example 2d: Creams prepared according to the invention as described above, in which the sunscreens (Parsol 1789 at 0.4% and Parsol MCX at 1.2% by weight of the composition) dissolved in mineral oil were added. Niacinamide was added at 1.0%.

Determination of uniformity of spreading of the cream: The frame with tapes was placed in a UV source, so that the sticky surface of the tape looks up. A UV filter was placed over the source to ensure that UV light of constant intensity was obtained in the range of 240-350 nm. A thin uniform film of a CBS-X fluorescent dye was taken, which has a maximum absorption of 368 nm and maximum emission of 406 and 426 nm, as a 2% solution in glycerol Water 1: 1, between two covers and placed on the side without glue from the tape. This allowed the emission of a visible light wherever UV light entered through the tape, which was captured by the video camera with a macroscopic lens (6X) that was used. In this way, wherever the blocker was present, UV light would be blocked and the fluorescer would not be excited, thus giving a black area. The video camera was connected to a computer with a frame capture card and using this image were stored. Using the computer program of image analysis Optimus it was possible to quantify the difference in the amount of UV uz that passes through the tape. The lower the intensity, better will be the blocking of UV and in this way, the better the effectiveness of the sunblock. In addition, for intensity measurement and macro photography using advanced image analysis techniques, the actual amount of UV A and UV B transmitted was also measured using specific probes for UV A and UV B. Table 1 shows that the effectiveness of sunblock in The formulation prepared according to the invention will be superior to creams prepared by the conventional process and is comparable with creams having twice the amount of sunscreen in a formulation prepared according to the conventional process.

Table 1 Example 3 Skin clearance data in vivo: 20 volunteers were selected who applied 0.75 g of the cream prepared according to the invention (2d), or creams prepared according to the conventional process (2b) or placebo (2a) on one of your forearms twice a day. The other forearm remained as a control without applying. The skin tone was evaluated on a scale of 1 0 points one day before the application and after 8 weeks of application. The data presented in Table 2 is a change in rating after 8 weeks of application. A negative rating indicates a lighter skin tone as compared to the control and a positive rating indicates a darker skin tone as compared to the control.

Table 2 EXAMPLE 4 The following creams were tested in a clinical double skin blinding test. Twenty volunteers were selected, who applied 0.75 g of creams prepared according to the invention as described in example 1, but using 25 sopropyl myristate (instead of minar oil) as the oil phase (3a), or creams prepared according to the conventional process (2b), on one of their forearms twice a day. The other forearm remained as a control without applying. Skin tone was assessed visually on a 10-point scale one day before application and after 8 weeks of application. The data presented in Table 3 is a change in rating after 8 weeks of application. A negative rating indicates a lighter skin tone as compared to the control.

Table 3 Test 1 Test 2

Claims (5)

REIVI NDICATIONS

1 . A process for preparing a sunblock compoon, comprising the steps of: (i) dissolving 0.1 to 10% by weight of the compoon of a sunblock ultraviolet absorber in an oil phase; (i) neutralizing stearic acid in an aqueous phase; and (iii) homogenizing the dissolved solar bio-agent with the neutralized stearic acid and a cosmetically acceptable vehicle.

2. A process according to claim 1, wherein the dissolved sunscreen is homogenized with the neutralized stearic acid and cosmetically acceptable vehicle, after the neutralized stearic acid and cosmetically acceptable vehicle. They have been homogenized.

3. A process according to claim 1 or 2, comprising the additional step of melting the stearic acid at a temperature above 70 ° C before step (ii).

4. A process according to any preceding claim, wherein the oil phase is isopropyl myristate.

5. A topical, sunscreen cosmetic compoon obtainable by the process according to any preceding claim.