In recent decades, concerns about harmful ultraviolet (UV) radiation have emerged. Protection against the sun’s rays has become a popular precaution many Americans take. Organic UV filter chemicals (UVFCs) are active ingredients found in sunscreens that absorb UV radiation to prevent it from causing cellular damage. By using a combination of different UVFCs and thereby covering the full range of UV radiation, an appropriate Sun Protection Factor (SPF) can be achieved. However, certain organic UVFCs are known to photodegrade, thus reducing their ability to absorb UV radiation and, in some cases, forming products that can be absorbed through the skin, potentially causing damage to cells. We are investigating the photostability and cellular toxicity of octyl methoxycinnamate (OMC), a common UVFC found in many sunscreens and cosmetic products. Upon exposure to UV light, OMC readily degrades to form photoproducts that have different photoreactivities. We have exposed both aqueous solutions of OMC and OMC in commercial sunscreens to simulated sunlight and analyzed them by high performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS). Known photoproducts of OMC include 2-ethylhexanol (2-EH), 4-methoxybenzaldehyde (4-MBA), and OMC dimers, all of which have been isolated and identified using preparatory-scale HPLC. Further identification of OMC dimers, which form a four-membered ring across the double bond of OMC, has been accomplished using NMR spectroscopy. We also investigated the cellular toxicity of OMC, 2-EH, and 4-MBA using NIH/3T3 cells. OMC and 4-MBA are toxic to cells at concentrations of 0.1 mM and higher, while 2-EH did not show cytotoxic effects up to 1 mM. Results from this research will help us better understand the photodegradation of OMC, as well as the toxicity of OMC and its photoproducts.

Photolysis and toxicity of ultraviolet filter chemical

251st National Meeting (2016)

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