Change of Ultraviolet Absorbance of Sunscreens by Exposure to Solar-Simulated Radiation

Abstract

Regarding the outdoor behavior of the Caucasian population, modern sunscreens should provide high and broad-spectrum ultraviolet protection in the ultraviolet B as well as in the ultraviolet A range and should be photochemically stable for ultraviolet doses, which can be expected in solar radiation. At present an assessment of the photostability of suncare products is not a general requirement before marketing. In order to evaluate the photostability of suncare products we conducted an in vitro test and measured the spectral absorbance of 16 sunscreens before, and after exposure to increasing biologically weighted standard erythema doses (5, 12.5, 25, 50) of solar-simulated radiation. Seven of 16 suncare products showed a significant dose- and wavelength-dependent decrease of the ultraviolet A protective capacity, whereas the ability to absorb ultraviolet B was not affected. In the ultraviolet A range, the decrease of absorbance (photoinactivation), respectively, the increase of transmission was 12-48% for an ultraviolet exposure of 25 standard erythema dose. Photoinactivation started in the wavelength range between 320 and 335 nm with a maximum above 350 nm. Furthermore, our analysis showed that the behavior of suncare products was not predictable from its individual ingredients. Neither complex combinations of organic filters nor addition of inorganic filters could absolutely prevent photoinactivation. The inclusion of a single photounstable filter did not mean photoinstability of the complete suncare product. Photoinactivation of sunscreens appears to be an underestimated hazard to the skin, first, by formation of free radicals, second, by increased ultraviolet A transmission.

Alternative methods to evaluate the protective ability of sunscreen against photo-genotoxicity

“…We observed significant increases in transmittance for SPF 20 trials during a 2 hour period of exposure to the sun, but this phenomenon was not observed for SPF 40 trials (data not shown). Photo-inactivation of sunscreens may be responsible for the underestimation of UV-damage as described by Maier et al [28]. We have observed the advantages of repeated application of sunscreen during a period of 4 hours of solar radiation (data not shown).…”

Identification of Quenchers of Photoexcited States as Novel Agents for Skin Photoprotection

“…1 (Gasparro, 2000). However, few photostable chromophores for broadband UVA filtering are available (Maier et al, 2001). Many UVA screens are inefficient, particularly in the near visible UVA and blue visible regions important for skin photosensitization, and rapidly undergo photoisomerization/ degradation due to uncontrolled excited state chemistry (Allen et al, 1996;Serpone et al, 2002).…”

Avaliação da fotoestabilidade e penetração cutânea de fotoprotetores contendo associações de filtros solares, trans-resveratrol e beta-caroteno

“…Estudos têm mostrado que alguns fotoprotetores perdem parte da sua proteção quando expostos à radiação UV (HAYWOOD et al, 2003;MAIER et al, 2001;MARROT et al, 2004;MAIER et al, 2005;SERPONE et al, 2002;TARRAS-WAHLBERG et al, 1999 Depois de selecionar a solução extratora mais adequada para os ensaios de fotoestabilidade, iniciou-se a padronização das condições cromatográficas para análise dos filtros solares, do trans-resveratrol e do beta-caroteno nas diferentes associações utilizadas nas formulações em estudo.…”

“…Estudos anteriores demonstram que alguns filtros solares perdem parte de sua capacidade fotoprotetora quando em contato com a radiação UV (DAMIANI et al, 2006;MARROT et al, 2004;GONZÁLEZ et al, 2007) e, ainda, que a fotoinativação não é um fenômeno que necessita de grandes doses de UV para acontecer (MAIER et al, 2001). Além disso, de acordo com Bonda, Zhang e Pavlovic (2011) o contato com a radiação UV pode reduzir significativamente a atividade antioxidante do trans-resveratrol.…”

“…Além disso, a molécula no estado excitado singleto, pode passar para o estado excitado tripleto através da transição intersistemas. Uma vez, no estado excitado tripleto, a molécula pode dissipar a energia por meio da emissão de um fóton ( Os filtros solares inorgânicos (TiO 2 e ZnO) também absorvem radiação UV, e como consequência disso, podem ser formadas EROS, que podem interagir com os filtros orgânicos (BUCHALSKA et al, 2010;LEWICKA et al, 2013 CAMPOS, , 2010GONZÁLEZ et al, 2007;MAIER et al, 2001).…”