Organic ultraviolet (UV) filter chemicals are the active ingredients used in sunscreens, lotions, cosmetics and other personal care products to protection the skin from UV light. One commonly used organic UV filter chemical is octyl methoxycinnamate (OMC), better known by its commercial name, octinoxate. Though they are designed to be photostable, many organic UV filter chemicals are known to degrade upon exposure to UV light, which has implications for their effectiveness in sunscreen products, their fate in the environment, and the potential for unintended toxicity. A previously published study conducted in our lab summarized the aquatic photolysis of OMC, including direct and indirect photolysis and tentative product identifications. In this study, OMC dimer photoproducts have been isolated via preparatory-scale high performance liquid chromatography (prep-scale HPLC) and definitively identified, and the cellular toxicities of OMC and all isolated photoproducts have been determined. In addition to 4-methoxybenzaldehyde (4-MBA) and 2-ethylhexanol (2-EH), which were previously identified, two major photostable OMC dimers have been isolated and identified using mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. The two isolated dimers are truxinates (i.e., arising from head-to-head cycloaddition). A neutral red assay using NIH/3T3 cells, a mouse fibroblast cell line, was performed to assess the cellular toxicities of OMC and its photoproducts. Both the cis and trans isomers of OMC, as well as 4-MBA and the two isolated OMC dimers, are toxic to NIH/3T3 cells at concentrations at or above 100 μM. 2-EH is not toxic to the cells at any concentration tested.  Results from this research give a more complete picture of the implications of OMC photolysis, as well as data that can be used to evaluate the future use of OMC as a sunscreen agent.

Identification and toxicity testing of the photochemical degradation products of octyl methoxycinnamate, a common organic UV filter chemical

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.