WO2004050050A1

WO2004050050A1 - Sunscreen composition for topical application

Info

Publication number: WO2004050050A1
Application number: PCT/EP2003/011507
Authority: WO
Inventors: Govindarajan Raman; Sushama Shripad Wagh
Original assignee: Unilever Plc; Unilever Nv; Hindustan Lever Limited
Priority date: 2002-12-04
Filing date: 2003-10-17
Publication date: 2004-06-17
Also published as: GB0306085D0; AU2003276115A1

Abstract

A sunscreen composition for topical application containing an absorber for radiation at the wavelengths 475 to 515 nm and 595 to 610 nm, wherein the absorber is a dye or mixture of dyes

Description

SUNSCREEN COMPOSITION FOR TOPICAL APPLICATION

The present invention relates to sunscreen formulations, and in particular to sunscreen formulations adapted for anti- tanning efficacy by protecting skin not only from the UV range, but also the visible spectrum of the sun radiation or like artificial lightening using wavelengths between 475 to 515 nm and 595 to 610 nm.

It is usually known that solar ultra violet radiation of the. sun spectrum can cause high rate of acute adverse effects, such as aging of skin and skin burns .

A tan is essentially the skin's way of increasing its defence against the onslaught of damaging UV. Tanning protects against sun damage principally by increasing the melanin content of the epidermis. While it is true that the greater the skin pigmentation the better as far as sun protection goes, it does not necessarily follow that intentional UV induced tanning can achieve an increase in protective pigmentation as the best sun/UV protective strategy.

Recent evidence suggests that tanning occurs only after DNA damage has already occurred. Incremental damage occurs with each exposure to UV radiation even with doses that do not produce erythema (uv induced inflammatory response) . The damage is cumulative with time, and the magnitude of the exposures . In practical terms the biologically important output from the sun reaching the earth surface can be divided into four wavelengths regions, UVB (290-315 nm) , UVA (315-400 nm) , Visible Light (400-760 nm) and Infrared (760-10⁶ nm) . Ultraviolet wavelengths shorter than about 280 nm are heavily absorbed by molecular oxygen, ozone and water vapour in the upper atmosphere and do not reach the surface of the earth in measurable amounts .

It is thus known that the major source of the damaging effects of sunlight stem primarily from the ultra violet portion of the spectrum between 290 to 400 nm. It has thus been the usual trend in the art to avail of various sun protection strategies against such damaging effects of the sun spectrum in the UV range of 290-400 nm, and thus avoid skin disorders and related problems such as aging of skin, chronic sun damages, wrinkling and immunological effects.

The simplest strategy for protection from the harmful effects of UV spectrum of sunlight is avoidance of sun exposure and/or use of protective clothing/measures.

It is also known that application of chemical sunscreens and anti-tan compositions that are specifically formulated to absorb the well known harmful UV spectrum of sun radiation also protect against UV induced damage. Such chemical sunscreens block the penetration of UV radiation through the epidermis by absorbing the incident UV.

The sunscreen molecules (composed of aromatic ring structures and/or alternating single and double bond structures) absorb the high-energy UV photons causing the electronic structure to move to a higher energy state. This energy is dissipated by resonance delocalization and conversion to lower energy long wave radiation, which is then re-emitted as heat . However a certain amount of UV light still enters the epidermis, and no chemical sunscreen blocks 100% of all incident UV radiation.

Moreover, for effective protection, sunscreens are required to be uniformly applied onto the skin. In order to ascertain such uniformity in application of the sunscreen use of colored sunscreens, which would indicate uniform application of sunscreens has been proposed.

WO 94/26233 proposes the use of phenolphthalein, an acid base indicator, added to sunscreens to create initial indication on application of the sunscreen, which subsequently disappears. WO 95/28912 teaches the provision of coloured particles in UV sunblock compositions. US 5747011 discloses colored sunscreen compositions which disappear when dried on the skin or rubbed into the skin. US 6042813 discloses an oil soluble dye which can be added to a sunscreen emulsion which can render the sunscreen visually coloured, such that coloration will substantially disappear when the sunscreen emulsion is rubbed into the skin.

The principal aim for sunscreen formulations over the years was thus directed to a protection against UVB and UVA in sunscreen formulations. However, recent developments are known to provide sunscreen formulations which extend protection not only over the regions of UVA and UVB radiation from 290-400 nm but also to regions perceptible to the eye extending up to 800 nm.

US 6187298 provides cosmetic formulation which offer protection against the damaging effect of the sunlight both in the UV region and also in the long-wave region, the visible region (VIS region) and the infrared wavelength region (IR region) . The prior art suggests light protection filters effective in the wavelength region from 400-800 nm (VIS region) and in the infrared wavelength region (IR region) from 800 nm. The protective filter basically comprises an interference pigment material comprising at least one of i) a copper and/or skin coloured interference pigment which is platelet-shaped or ground mica coated with

Sn0₂ and/or Tiθ₂ or ii) a white body colour and a copper or skin coloured interference colour coated with Ti0₂.

The above prior art teaches sunscreen formulations which provide protection not only in the UV region, but which extends to visible and IR region of the sun spectrum. However, there has not been any detailed study/available knowledge in the art on the relation of the UV region, visible region and IR region of the sun spectrum vis-a-vis tanning, in particular immediate pigment darkening and/or delayed tanning caused by the sun spectra. Also, for such reasons it was not possible to immediately reach to formulations which could serve as sunscreens which could take care of specific tanning symptoms such as immediate pigment darkening, and/or delayed tanning effects. It has thus been a basic objective of the present invention to identify regions in the solar spectrum which cause tanning, especially immediate pigment darkening (IPD) and/or delayed tanning (DT) effects. Also, an objective is to provide cost-effective means for effectively protecting skin against such heretobefore unidentified tanning caused by the solar spectrum.

Another object of the present invention is to provide for sunscreen/anti-tanning formulation which would take care of immediate pigment darkening, as well as delayed tanning caused by the visible spectrum of the sun between 475 to 515 nm and 595-610 nm.

Another object of the present invention is to provide for sunscreen/anti-tanning formulations which would serve as sunscreen/anti-tanning aids for protection not only against ultraviolet exposure, but extend protection to the visible spectrum of the sun radiation, which are found to have substantial contribution in skin damage, especially tanning.

Yet further object of the present invention is directed to provide for sunscreen/anti-tanning formulations which would serve as cost-effective anti-tanning formulations along with the conventional UVA and/or UVB sunscreens.

Yet further object is directed to provide selective anti- tanning dyes which in combination with conventional sunscreen, anti-tanning formulations would provide for protection against tanning from the solar spectrum in regions extending beyond the conventional ultraviolet region of conventional sunscreens .

Yet another object of the present invention is to provide for a cost-effective alternative to the expensive conventionally used UVA/UVB sunscreens, thereby making available sunscreen formulations which would meet the wide- scale demands of cost-effective and safe sunscreens.

Thus according to a first aspect of the present invention, there is provided a sunscreen/anti-tanning system comprising means adapted for absorbing sun spectrum in the visible spectrum between 475-515 nm and 595-610 nm responsible for immediate pigment darkening (IPD) and/or delayed tanning (DT) .

According to preferred aspect the sunscreen/anti-tanning system comprise compounds adapted for absorbing the sun spectra in the visible range between 475-515 nm and 595-610 nm. Such compounds can comprise selective dyes or mixtures of dyes in selective amounts, which would absorb sun spectrum in the visible spectrum between 475-515 nm and 595- 610 nm, and avoid problems of immediate pigment darkening and/or delayed tanning.

The above disclosed sunscreen/anti-tanning system of the present invention is adapted to take care of protecting the skin from the visible spectrum which is an inherent component in sun radiation and found by way of the present invention to cause immediate pigment darkening and/or delayed tanning. In particular, it has been identified by the present invention that the sun spectrum responsible for immediate pigment darkening (IPD) and delayed tanning (DT) is not only the UVB and UVA regions of the sun' s spectrum, but also the visible regions of the spectrum.

In accordance with another aspect of the present invention, there is provided a cosmetic composition comprising along with conventional ingredients at least one sunscreen/anti- tanning system adapted for providing tan protection in the visible spectrum between 475-515 nm and 595-610 nm.

The above cosmetic composition is directed to improve the anti-tanning benefits of such formulations by extending the anti-tanning effects to the visible and late UV regions.

The anti-tanning system can include dyes or mixtures of dye preferably brilliant blue, carmoisine and sunset yellow based on the absorption spectra. In particular, the blue dye which is found to be most effective in offering protection against tan and in combination with yellow offers even better protection.

The details of the invention its objects and advantages are hereby explained in greater detail in relation to non- limiting exemplary illustrations provided by way of example only, and discussed hereunder.

Examples

Example 1 i . Identification of regions in the sun spectra responsible for immediate pigment darkening and/or delayed tanning.

White, Blue, Green, Yellow and Red coloured filters were suitably fixed on a template to let equal transmission of UVA and UVB. Glass cover-slips were used to shield the skin completely against UV radiation and permit total visible region to pass through the window. The white filter lets the total radiation pass through, and is the material control for the colour windows. The description of the filters used is indicated in Table 1.

Sticker templates with these windows were used for the study on 15 subjects. On Day 1, subjects had their designated test sites (forearm) marked with a ball point pen; the sites were then evaluated for even tone. Templates were placed on the forearms, leaving the windows, and open windows at the test sites for the exposure. All other areas on the forearm were kept covered. The sites were then exposed to the sun for 30 minutes to the clear sky mid-day sun, leaving the volunteer in a shade. The sites were visually evaluated prior to the exposure and immediately after on the first day of exposure for IPD evaluation.

The procedure was repeated for three consecutive days and the evaluation of delayed tan was done on day 10. Visual evaluations were done by taking the tan scores and the Tan protection index (TPI) was calculated. The TPI is an indicator of the degree of tanning scores of the treated sites in comparison to the scores at the open sites. The results, i.e. the TPI values at IPD and DT, have been plotted as per the spectral characters the window and have been depicted in the figures .

Table 1

Findings

The results obtained are reported in Figures la, lb, 2a, 2b,

3a, 3b, 4a, 4b, 5a and 5b.

As clearly illustrated in Figures la and lb, the UVB region of the sun spectra (310-325 nm) is only partly responsible for delayed tanning and IPD. The higher UVA region between 360-380 nm is responsible for IPD (Figure 2a) , while 355-365 nm causes delayed tanning (Fig. 2b) . Visible region between 475 to 485 nm caused IPD as well as delayed tanning (Figs. 3a and 3b) . Visible range 595-610nm is responsible more for DT rather than IPD (Figs. 4a and 4b) . The visible region between 500 to 515 nm (Fig. 5a) and 700-705 nm (Fig. 5b) windows caused delayed tanning.

Based on the above findings on relation of the sun spectra and the regions responsible for the IPD and DT, the following exemplary forms of the anti-tanning system of the invention were tested as discussed hereunder.

Example 2

Materials used

Selective Dyes - Food grade dyes brilliant blue (FCF) ,

Sunset yellow, Carmoisine.

Preparation of formulations

Test formulations (1) to (10) with or without the above selected dyes were obtained as detailed in Table 2 hereunder

Table 2

15 subjects were selected for the anti-tanning efficacy trial involving the above formulations (1) to (10) , and the following protocol was followed. On day 1, subjects, had their designated test sites (forearm) marked; the sites were then evaluated clinically for eventone. All the sites received the designated applications 15 minutes before the sun exposure. Templates were placed on the forearm, leaving the windows open at the test sites. The sites were then exposed to the sun for 30 minutes to the clear sky midday sun. The sites were visually evaluated prior to the exposure and lh after on the first day of exposure for IPD. The procedure was repeated for three consecutive days and evaluation of tan was done on day 10 for DT.

Visual evaluations were done by taking the tan scores, and the Tan protection index (TPI) was calculated. The TPI is an indicator of the degree of tanning scores of the treated sites in comparison to the scores at the unprotected (cream # 10) sites. The data was analysed statistically, and is presented in Table 3.

Table 3

As would be evident from the above results, that anti- tanning system involving the dyes Brilliant Blue, Sunset Yellow and Carmoisine, while providing for comparable supplemental sunscreens to avoid to a certain extent immediate pigment darkening necessarily proved to be superior in terms of delayed tanning effects caused by the visible spectra of sun rays.

This confirms the favourable and cost-effective application of the anti-tanning system comprising dyes suggested to take care of problems .of immediate pigment darkening/delayed tanning caused by the visible spectra of sun radiation or like artificial light in the regions of 475 to 515 nm and 595 to 610 nm in combination with conventional sunscreen for a better protection against the sun spectrum extending beyond the UV region. Also, the anti-tanning system and sunscreen formulations incorporating the same would serve as cost-effective alternatives to expensive UVB sunscreen conventionally in use, thereby providing for wide scale and cost effective availability of such sunscreen formulations.

Claims

A sunscreen composition for topical application containing an absorber for radiation at the wavelengths 475 to 515 nm and 595 to 610 nm.

A sunscreen composition according to Claim 1 wherein the absorber for radiation at wavelength 475 to 515 nm and 595 to 610 nm is a dye or mixture of dyes.

A sunscreen composition according to Claim 2 wherein the dye is brilliant blue, carmoisine or sunset yellow, or mixtures thereof .

4. A sunscreen composition according to any preceding claim additionally comprising a UVA and/or a UVB radiation absorber.