Journal
FREE RADICAL RESEARCH
Volume 46, Issue 3, Pages 265-275Publisher
INFORMA HEALTHCARE
DOI: 10.3109/10715762.2011.651719
Keywords
electron-spin-resonance spectroscopy; free radical; solar radiation; sunscreen; 5,5-dimethyl-1-pyrroline N-oxide
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Funding
- Restoration of Appearance and Function Trust (RAFT) [299811]
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The in vitro star system used for sunscreen UVA-testing is not an absolute measure of skin protection being a ratio of the total integrated UVA/UVB absorption. The in vivo persistent-pigment-darkening method requires human volunteers. We investigated the use of the ESR-detectable DMPO protein radical-adduct in solar-simulator-irradiated skin substitutes for sunscreen testing. Sunscreens SPF rated 20+ with UVA protection, reduced this adduct by 40-65% when applied at 2 mg/cm(2). SPF 15 Organic UVA-UVB (BMDBM-OMC) and TiO2-UVB filters and a novel UVA-TiO2 filter reduced it by 21, 31 and 70% respectively. Conventional broad-spectrum sunscreens do not fully protect against protein radical-damage in skin due to possible visible-light contributions to damage or UVA-filter degradation. Anisotropic spectra of DMPO-trapped oxygen-centred radicals, proposed intermediates of lipid-oxidation, were detected in irradiated sunscreen and DMPO. Sunscreen protection might be improved by the consideration of visible-light protection and the design of filters to minimise radical leakage and lipid-oxidation.
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