WO2013068970A2

WO2013068970A2 - Sunscreen compositions

Info

Publication number: WO2013068970A2
Application number: PCT/IB2012/056283
Authority: WO
Inventors: Ncoza DLOVA
Original assignee: University Of Kwazulu-Natal
Priority date: 2011-11-10
Filing date: 2012-11-09
Publication date: 2013-05-16
Also published as: WO2013068970A3

Abstract

This invention relates to sunscreen compositions comprising titanium dioxide, iron oxide, or a mixture thereof. The metal oxide particles having a particle size of between 0.02 to 2000 μm. The metal oxide particles can be derived from kaolinite clay.

Description

SUNSCREEN COMPOSITIONS

BACKGROUND TO THE INVENTION

This invention relates to sunscreen compositions. In particular, the invention relates to a sunscreen composition that provides adequate protection against UVA and partial protection against UVB radiation.

Overexposure to the ultraviolet (UV) radiation, commonly from the sun's rays can lead to severe acute sunburns of the skin. Excessive UV radiation is the leading cause of primarily non-melanoma skin tumours. The worldwide increase in the incidences of skin cancer requires effective means of photoprotection. Hence topical application of sunscreen products is encouraged by health authorities to protect both healthy and photosensitive skins from the sun. Sunscreens are important skin care products used to prevent photoageing and skin cancer, amongst other skin conditions.

Medical organisations such as the American Cancer Society recommend the use of broad spectrum sunscreen which prevents both squamous cell carcinoma and basal cell carcinoma of the skin. However, the use of sunscreens is controversial for various reasons. Many available sunscreens do not block UVA radiation, which does not cause sunburn but can increase the rate of melanoma. Although some sunscreen products specify that the composition is a broad spectrum UVA/UVB protection product, majority of these products do not provide adequate protection against UVA rays. A number of reports indicate that sunscreen products are photounstable particularly in the ultraviolet-A region of the solar spectrum. Therefore, those using sunscreens may be exposed to a high level of UVA without realizing it. UVA causes DNA damage to viable cells deep within the skin, via generation of radicals such as reactive singlet oxygen (ROS). The ROS attack the DNA bases producing lesions increasing the risk of malignant melanomas. Adequate UVA protection is provided predominantly by products that contain zinc oxide, avobenzone and ecamsule. Titanium dioxide also provides good protection, however, does not completely cover the entire UVA spectrum apart from inducing degradation of constituent organic UV blocks. Zinc oxide is superior to titanium dioxide at wavelengths between 340nm and 380nm. Whereas ecamsule has peak protection at 345nm and avobenzone is intrinsically photounstable.

There is therefore a need for safe, cost effective sunscreen compositions that contain materials that protect against the whole range of UV wavelengths, therefore, preventing 100% UV radiation-induced immune suppression and ultimately prevent the development of skin cancer and photoageing.

Clay has been used around the world for centuries by indigenous people as an important medicinal and cosmetic tool. In South Africa, particularly in rural areas, use of clays as sunscreen is a widespread practice. The inventors have therefore used this as a basis for their studies.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a sunscreen composition comprising a metal oxide which is titanium dioxide, iron oxide or a mixture of both these oxides and wherein the metal oxide particles have a particle size of between 0.020 to 2000μηι. In a preferred embodiment of the invention the iron oxide particles have a particle size of between 0.20 to 100μιη and the titanium dioxide particles have a particle size of between 0.30 to 50 m.

According to a further aspect of the invention there is provided a sunscreen composition comprising a kaolinite clay mineral including inorganic particles of titanium dioxide or iron oxide having a particle size of between 0.020 to 2000μιη. In a preferred embodiment of the invention the titanium dioxide particles have a particle size of between 0.30 to 50pm and the iron oxide particles have a particle size of between 0.20 to 100pm.

There is also provided sunscreen composition comprising a kaolinite clay mineral including inorganic particles of titanium dioxide and iron oxide, wherein the inorganic particles have a particle size of between 0.020 to 2000pm. In a preferred embodiment the titanium dioxide particles have a particle size of between 0.30 to 50pm and the iron oxide particles have a particle size of between 0.20 to 100pm.

The white kaolinite clay mineral preferably comprises from about 50.86% oxygen, 20.98% aluminium, 22.78% silicon, 0.97% K, 1.97% Ti, 0.04% Mn, and 2.40% Fe, by weight. The composition may substantially be in the form of particles having a particle size of between 0.020 to 2000μιτι. Preferably the particles have a particle size of between 0.30 to 50pm.

The red kaolinite clay mineral preferably comprises from about 36.43% oxygen, 11.41% aluminium, 15.53% silicon, 0.32% K, 2.21 %Ti and 34.09% Fe, by weight. The composition may substantially be in the form of particles having a particle size of between 0.020 to 2000pm. Preferably the particles have a particle size of between 0.20 to 100pm.

The sunscreen composition can comprise the natural kaolinite mineral and this may be present in any amount of between 25 to 50 % by weight.

The sunscreen compositions also contain materials such as petroleum, liquid paraffin, glycerine and persivate. Other sunscreen agents may be incorporated into the sunscreen composition. These include: zinc oxide, PABA, padimate O, octinoxate, cinoxate, octisalate, homosalate, trolamine salicylate, octocrylene, ensulizole, oxybenzone, sulisobenzone, dioxybenzone, avobenzone, meradimate.

The sunscreen composition may be in the form of an emulsion, gel, lotion, dispersion, cream, powder, spray, solid stick or other topical product. In a preferred embodiment of the invention, the sunscreen composition is water resistant.

According to a further aspect of the invention, there is provided a cosmetic formulation comprising the sunscreen composition as defined above. The formulation may be in the form of anti ageing creams, moisturizers, lipsticks, lipbalms, tanning lotions, make up powders or foundations.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described in more detail, by way of example only, with reference to the accompanying figures in which:

Figure 1 is a report of the particle size analysis of the red clay, taken on

Malvern Mastersizer 2000

Figure 2 is a report of the particle size analysis of the white clay, taken on

Malvern Mastersizer 2000

Figure 3 is a table showing the elemental composition of both red and white clays

Figure 4 is an XRD spectrum showing the composition of the white clay

Figure 5 is an IR spectrum showing the composition of the white clay

Figure 6 is an XRD spectrum showing the composition of the red clay

Figure 7 is an IR spectrum showing the composition of the red clay

Figure 8 is a scanning electron microscopy image of the white clay

Figure 9 is a scanning electron microscopy image of the red clay DETAILED DESCRIPTION OF THE INVENTION

A sunscreen product has been developed from clay, which exhibits specific properties for the protection of human skin against UVA and UVB radiation from the sun.

Both the red and white natural clays contain inorganic compounds and kaolin. Red and white clay samples were analyzed for their chemical composition using energy dispersive X-ray fluorescence analysis and scanning electron microscopy. Further characterisation was performed using a Fourier transform infrared spectrometer. Sun protection of the clays were determined according to the South African Bureau of Standards.

White and red clay samples were bought from a market in Durban, South Africa. Morphological and microchemical analyses of the two clay samples were performed using scanning electron microscopy with energy dispersive X-ray fluorescence analysis (SEM-EDXRFA) techniques. Further characterization was done using Fourier transform infrared (FTIR) spectra in conjunction with FTIR libraries. This was done by drying about 0.25 mg of clay overnight in an oven at 150^°C. The dry sample was cooled in a dessicator and then mixed with about 50 mg KBr to make a pellet. The infrared spectrum of the clay sample was recorded between 250 and 4000 cm^"1. In order to assess the usefulness of both clays as sun screens, in vitro and in vivo sun protection factors (SPFs) of the clays were determined using ultra violet (UV) spectrophotometer and a solar simulator respectively. The testing was done at the School of Pharmacy, Medunsa University in accordance with the South African Bureau of Standards sunscreen 1557 method.

Analysis of the mineralogical composition of the clays using scanning electron microscope and infrared spectrophotometry techniques revealed that the white clay composed predominantly of kaolinite mineral (AI2O3.2SiO₂.2H₂O), while the red clay sample contained iron oxide compounds in addition to kaolinite mineral. This is evidenced by Figure 3. The EDXRFA spectra indicated the presence of kaolin, aluminium, oxygen, silicon, titanium and manganese in both clays, but with high concentration of iron in red clay (Figures 4 and 6).

Both clays have protective properties against UVA and UVB. The in vivo SPF for the white clay is 3.3 and the red clay is 7. The in vitro SPF results were highly variable due to poor spreading. The UVA: UVB ratio for the white clay was 0.82 with a star rating of 4 at critical wavelength 387nm. Similarly, the UVA: UVB ratio of red clay was 0.9 with a star rating of 4 at critical wavelength 388 nm. Both clays provide high UVA protection, but red clay provides higher UVB protection due to the additional iron found in red clay.

Particle size analysis results are shown in Figures 1 and 2. The particle sizes range from 0.020 to 2000μητι for both clays. The optimal particle size of the red clay is between 0.20 to Ι ΟΟμιη and the optimal particle size of the white clay is between 0.30 to 50μηη.

Claims

1. A sunscreen composition comprising a metal oxide selected from titanium dioxide, iron oxide, or a mixture thereof, wherein the metal oxide particles have a particle size of between 0.020 to 2000 pm.

2. The composition according to claim 1 , wherein the titanium oxide particles have a particle size of between 0.30 to 50 pm.

3. The composition according to claim 1 , wherein the iron oxide particles have a particle size of between 0.20 to 100 pm.

4. The composition according to any of the preceding claims, wherein the metal oxide is derived from natural kaolinite clay mineral.

5. A sunscreen composition comprising natural kaolinite clay mineral, wherein the titanium dioxide and/or iron oxide present in the clay have particle sizes of between 0.020 to 2000 pm.

6. The composition according to claim 5, wherein the titanium oxide particles have a particle size of between 0.30 to 50 pm.

7. The composition according to claim 5, wherein the iron oxide particles have a particle size of between 0.20 to 100 pm.

8. The composition according to any one of claims 4 to 7, wherein the natural kaolinite clay mineral is red kaolinite.

9. The composition according to any one of claims 4 to 7, wherein the natural kaolinite clay mineral is white kaolinite.

10. The composition according to claim 8, wherein the red kaolinite clay mineral comprises of an elemental composition of about 36.43% oxygen, 11.41% aluminium, 15.53% silicon, 0.32% K, 2.21 %Ti and 34.09% Fe, by weight.

11. The composition according to claim 9, wherein the white kaolinite clay mineral comprises of an elemental composition of about 50.86% oxygen, 20.98% aluminium, 22.78% silicon, 0.97% K, 1.97% Ti, 0.04% Mn, and 2.40% Fe, by weight.

12. The composition according to any one of claims 4 to 11 , wherein the natural kaolinite clay mineral is present in the composition in an amount of about 25% by weight.

13. A sunscreen composition comprising titanium dioxide having a particle size of between 0.020 to 2000 pm and wherein the composition comprises an elemental composition of about 50.86% oxygen, 20.98% aluminium, 22.78% silicon, 0.97% K, 1.97% Ti, 0.04% Mn, and 2.40% Fe, by weight.

14. A sunscreen composition comprising iron oxide having a particle size of between 0.020 to 2000 pm and wherein the composition comprises an elemental composition of about 36.43% oxygen, 11.41% aluminium, 15.53% silicon, 0.32% K, 2.21 %Ti and 34.09% Fe, by weight.

15. The composition according to any one of the preceding claims, wherein the sunscreen composition, further comprises one or more emollients selected from petroleum, liquid paraffin, glycerine and persivate.

16. The composition according to any one of the preceding claims, wherein the sunscreen composition further comprises sunscreen agents selected from zinc oxide, PABA, padimate O, octinoxate, cinoxate, octisalate, homosalate, trolamine salicylate, octocrylene, ensulizole, oxybenzone, sulisobenzone, dioxybenzone, avobenzone, meradimate.

17. The composition according to any one of the preceding claims, wherein the composition is in the form of an emulsion, gel, lotion, dispersion, cream, powder, spray, solid stick or other topical product.

18. The composition according to any one of the preceding claims, wherein the composition is water resistant.

19. A cosmetic formulation comprising the sunscreen composition as defined in any one of the preceding claims. The cosmetic formulation according to claim 19, wherein the cosmetic formulation is an anti-ageing cream, moisturizer, lipstick, lipbalm, make-up powder or foundation.