KR20010089579A - Sunscreen Composition - Google Patents

Abstract

In the present invention (a) 0.1 to 10% by weight of the ultraviolet absorbing sunscreen of the composition dissolved in oil; And (b) a cosmetically acceptable vehicle. Also described are methods of making such compositions. The composition of the present invention has improved sunscreen efficacy.

Description

Sunscreen Composition

Melanin is a black pigment synthesized by the action of the enzyme tyrosinase on the amino acid tyrosine. This reaction occurs in organelles called melanosomes contained within cells called melanocytes. Melanocytes deliver melanocytes with melanin to neighboring keratinocytes, which receive these organelles until they detach from the skin's surface layer in the body. The intensity of skin color is directly related to the number, size, melanin content of melanoma, the rate of its formation and the rate of delivery to keratinocytes. Melanin is also an important protective device for skin and subdermal tissue because it has the ability to absorb incident ultraviolet light.

The UV region is divided into three zones, where UV-A is in the wavelength range of about 320 to 400 nm, giving a tanning effect without inflammation; UV-B is in the region of wavelengths from about 290 to 320 nm, which causes erythema (sunburn) and eventually tanning; UV-C is a region with a wavelength of about 200 to 290 nm, which is generally absorbed by the ozone layer in the Earth's atmospheric layer but is potentially very harmful to the skin.

Melanin formation and pigmentation of the skin are closely related to irradiation with UV light. Photobiological changes that cause erythema also cause melanogenesis and increase pigmentation. Thus, exposure to sunlight darkens the skin by immediate pigment darkening of already formed melanin and also by the formation of new melanin. Many skin compositions have been formulated for the purpose of maintaining skin color against blackening after exposure to ultraviolet light. These compositions were based on materials that reflected and scattered, or absorbed, incident ultraviolet light at wavelengths that burn and tan the skin.

In order to prevent the blackening of the existing melanin and the formation of new melanin, the skin should be widely protected over the UV-A region of about 320 to 400 nm. The inventors have found that by carefully selecting the sunscreen agent, the skin can be protected against the blackening effect by radiation.

British Patent 1 370 236 discloses a skin lightening composition containing niacin and a method of performing skin whitening by delaying the dispersion or distribution of melanin to the epidermis.

British Patent 1 533 119 discloses that niacinamide is useful as a skin lightening agent without causing a skin flushing reaction due to vasodilation, often associated with niacin.

British Patent 2230186 discloses that adding a silicone compound to a composition containing a mixture of sunscreen and niacinamide improves the coverage of the cream against the skin to improve protection against UV light. Doing.

The present invention relates to an improved cosmetic sunscreen composition for topical application to human skin to enhance protection from sunlight and a method of making the same.

The inventors have found that skin protection against UV light by compositions containing sunscreen agents is improved when the sunscreen agent is dissolved in the oil phase. More specifically, the inventors have found that the use of sunscreens dissolved in an oil phase improves sunscreen efficacy over what can otherwise be achieved by using substantially higher levels of sunscreens. Thus, the present invention reduces the amount of sunscreen required to achieve the same UV protection.

Accordingly, the present invention provides a composition comprising (i) 0.1 to 10% by weight of an ultraviolet absorbing sunscreen of a composition dissolved in oil; And (ii) a cosmetically acceptable vehicle. This composition is preferably obtained by the method provided below by the present invention.

The present invention also provides

(i) dissolving 0.1-10% by weight of the ultraviolet absorbing sunscreen agent of the composition in the oil phase;

(ii) neutralizing stearic acid in the aqueous phase; And

(iii) homogenizing the dissolved sunscreen with neutralized stearic acid and a cosmetically acceptable vehicle.

The dissolved sunscreen can be homogenized with neutralized stearic acid and subsequently blended with the vehicle (and other components) of the composition. However, it is desirable to blend the neutralized stearic acid and the vehicle together and subsequently add the dissolved sunscreen to this blend, since this has been found to provide a composition with an optimal sunscreen effect.

Preferably stearic acid is neutralized with an alkali such as potassium hydroxide. Prior to step (ii) it is preferred to melt the stearic acid at a temperature above 70 ° C.

Sunscreen agents are preferably 4-tert-butyl-4'-methoxy dibenzoylmethane available under the trade name PARSOL 1789 from Givaudan, 2-ethyl hexyl methoxy cinnana available under the trade name PARSOL MCX from Jibaudan. Mate, or a mixture of these two sunscreen compounds. The composition contains the sunscreen compound in an amount of 0.1 to 10% by weight of the composition, preferably 0.1 to 5% by weight of the composition.

The oil may be from mineral oil, vegetable oil or any other origin, but is preferably present in the liquid phase at temperatures above 20 ° C. The oil may be selected from mineral oil, peanut oil, sunflower oil, safflower oil, sesame oil or mixtures thereof. However, when using the preferred method of dissolving the sunscreen in the oil phase and subsequently adding it to the neutralized stearic acid and vehicle blended in the water phase, the oil need not be present in the liquid phase at temperatures above 20 ° C. . Suitable oil in this case is isopropyl myristate.

In one embodiment, stearic acid is first melted at 70 ° C. and then neutralized with aqueous potassium hydroxide, to which the sunscreen agent dissolved in oil is added after cooling the emulsion to a temperature below 50 ° C. This emulsion forms the substrate for all other components. All other components can then be homogenized to the substrate. In a preferred embodiment, these other components are blended with stearic acid / aqueous acid and then homogenized onto the sunscreen / oil.

The composition of the present invention may optionally comprise one or more skin whitening agents in an amount of 0.1 to 10% by weight, preferably 0.5 to 5% by weight. The skin whitening agent is preferably selected from niacin, niacinamide, or its precursor capable of releasing niacinamide on the skin. Niacinamide is an amide of niacin and is also known as nicotinamide or pyridine-3-carboxylic acid. An example of a compound that is a niacinamide precursor is niacinamide ascorbate. Other suitable skin whitening agents include placental extracts, hydroquinones and derivatives (e.g. arbutin), kojic acid, dicarboxyl of the formula HOOC- (CxHy) -COOH, where x = 4-20 and y = 6-40. Acids (azelanic acid, sebacic acid), ascorbic acid and derivatives thereof, hydroxy acids (lactic acid, glycolic acid, malic acid, tartaric acid, etc.), ferulic acid, retinol and derivatives or any other known skin whitening compound.

The vehicle that forms part of the cosmetic composition is one or more substances that are compatible with sunscreens and, where present, skin whitening agents and do not harm the skin. Vehicles can act as diluents, dispersants, or carriers for the other ingredients of the composition, and are therefore intended to be readily applied to the skin and evenly distributed throughout the skin at appropriate concentrations.

The Federal Food, Drug & Cosmetic (FD & C) Act of 1938 made food color additive certification mandatory and transferred the authority for its testing from USDA to FDA. To avoid confusing color additives used in food with those manufactured for other uses, three categories of certifiable color additives were created:

Vehicles that may be used in the compositions according to the invention may include water, powder absorbers, binders and carriers and liquids such as emollients, propellants, solvents, wetting agents and thickeners.

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

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

Example 1:

Process for the preparation of the composition according to the invention

60 g of water were heated to 70 ° C. in a main mixer with 0.48 g of potassium hydroxide. 16 g of stearic acid, 4.4 g of isopropyl palmitate and 0.15 g of propyl paraben were heated in a secondary vessel to 70 ° C. and added to the main mixer and mixed well. To this was added other conventional ingredients, 1 g of niacinamide, perfume and water and blended well. The mixture was cooled to 30 ° C. and 0.4 g of Parasol 1789 and 1.2 g of Parasol MCX dissolved in 2 g of mineral oil were homogenized with the rest of the formulation.

Conventional method:

60 g of water and 0.48 g of potassium hydroxide were placed in the main mixer. 16 g of stearic acid, 0.15 g of propyl paraben, 0.2 g of silicon and 4.4 g of isopropyl palmitate were blended in an auxiliary vessel and heated to 70 ° C. to dissolve 0.4 g of Parasol 1789 and 1.2 g of Parasol MCX in a portion of this mixture. These two mixtures were added to the main mixer with stirring and blended well. Other conventional ingredients, 1 g niacinamide, perfume and water, were mixed well by adding and stirring up to 100 g.

Example 2:

Spread and transfer of sunscreen onto the skin

The forearms of the 15 volunteers were washed with soap, patted dry on the surface, and the cream applied after 30 minutes to dry the forearms appropriately and uniformly. Each of the templates was used to mark an area of 2 cm x 3 cm. 30 mg of cream was applied using a glass rod with proper care to spread only inside the marking area. Impressions of the experimental zones were taken individually using cellophane tape from the dispenser with sufficient care not to soil the surface. The tapes were placed on the frame. Other treatments were as follows.

Example 2a: sunscreen or cream without niacinamide (placebo).

Example 2b Cream prepared by the conventional method described above, wherein the sunscreen (Parasol 1789 was 0.4% by weight of the composition and Parasol MCX was 1.2% by weight of the composition) and niacinamide level was 1.0%.

Example 2c A cream prepared as in Example 2b but containing two levels of sunscreen (Parasol 1789 was 0.8% by weight of the composition and Parasol MCX was 2.4% by weight of the composition) and niacinamide (2.0%) My.

Example 2d: A cream prepared according to the invention as described above, wherein a sunscreen dissolved in mineral oil (Parasol 1789 was 0.4% by weight of the composition and Parasol MCX was 1.2% by weight of the composition) was added and niacin 1.0% of amide was added.

Measurement of uniformity of spreading of creams:

The frame with the tapes was placed on a UV light source with the tacky surface of the tape facing down. The UV filter was placed over the light source so that the UV light had a constant intensity ranging from 240 to 350 nm. A homogeneous thin film of fluorescent dye CBS-X with a maximum absorption wavelength of 368 nm and a maximum emission wavelength of 406 and 426 nm was placed on the non-adhesive side of the tape, sandwiched between two cover slips as a 2% solution in 1: 1 glycerol: water. . This enabled the emission of visible light wherever the UV light coming out of the tape taken with a video camera with a macro lens (6 ×) was present.

Thus, wherever the sunscreen is present, UV light will be blocked and the fluorescent material will not be excited to provide a black area. The video camera was connected to a computer with a frame grabber card and used to store the images. Optimas image analysis software was used to quantify the difference in the amount of UV light passed through the tape. The weaker the strength, the better the UV protection and therefore the better the sunscreen efficacy. In addition, for macrophotographing and intensity measurement using advanced image analysis techniques, the actual transmission of UV A and UV B was also measured using special probes for UV A and UV B.

Table 1 below shows the efficacy of the sunscreen agent in the formulations prepared according to the present invention is superior to the cream formulations prepared by the conventional method, and the cream formulation having twice the amount of the sunscreen agent in the formulations prepared according to the conventional method. Shows comparable.

Example burglar UV A UV B 2a 54.17 0.25 0.21 2b 43.62 0.15 0.08 2c 23.06 0.08 0.02 2d 32.46 0.10 0.03

Example 3:

Bio Skin Whitening Data:

Twenty volunteers were selected in which 0.75 g of cream (2d) prepared in accordance with the present invention, or 0.75 g of cream (2b) or placebo (2a) prepared according to a conventional method was applied to one of their forearms twice daily. The other forearms were maintained as uncoated controls. Skin tone was evaluated on a 10 point scale one day before and eight weeks after application. The data shown in Table 2 below is the change in score after 8 weeks of application. Negative scores indicate lighter skin tones compared to the control and positive scores indicate darker skin tones compared to the control.

Example Score 2a +0.04 2b -0.42 2d -0.54

Example 4

The following creams were included in the double blind skin whitening clinical trial. 0.75 g of cream (3a) prepared according to the present invention as described in Example 1 but using 2% isopropyl myristate as an oil phase (instead of mineral oil), or cream (2b) prepared according to a conventional method. Twenty volunteers were applied to one of their forearms twice daily. The other forearms were maintained as uncoated controls. The skin tone was visually evaluated on a 10 point scale one day before and eight weeks after application. The data shown in Table 3 below is the change in score after 8 weeks of application. Negative scores indicate brighter skin tones compared to the control.

Test 1 Test 2 2b -0.46 -0.30 3a -0.51 -0.39

Claims (5)

(i) dissolving 0.1-10% by weight of the ultraviolet absorbing sunscreen agent of the composition in the oil phase; (ii) neutralizing stearic acid in the aqueous phase; And (iii) homogenizing the dissolved sunscreen with neutralized stearic acid and a cosmetically acceptable vehicle. The method of claim 1, wherein after homogenizing the neutralized stearic acid and the cosmetically acceptable vehicle, the dissolved sunscreen agent is homogenized with the neutralized stearic acid and the cosmetically acceptable vehicle. 3. The process according to claim 1, further comprising melting the stearic acid at a temperature above 70 ° C. prior to step (ii). 4. The method of claim 1, wherein the oil phase is isopropyl myristate. A sunscreen composition for topical cosmetics obtainable by the method according to any one of claims 1 to 4.