Investigating the photophysical properties of sunscreen active ingredients

CHED 991

Andrew C. Rudawsky, and Sarah J. Schmidtke, Department of Chemistry, The College of Wooster, 943 College Mall, Wooster, OH 44691
The goal of this study was to investigate the effect of solvent on two sunscreen agents, menthyl anthranilate and sulisobenzone; specifically how spectral properties and stability after irradiation with UV light can change. Analysis of the compounds through absorbance spectroscopy in a broad range of solvents showed that solvent plays a large role in determining the absorbance maxima of sulisobenzone; solvents with lone electron pairs led to blue-shifted absorbance spectra, while menthyl anthranilate was less affected by solvent polarity. It was found that both sunscreens degraded slowly after exposure to sunlight; with sulisobenzone degrading only 8% and menthyl anthranilate degrading 25% after 120 min. Analysis of irradiated menthyl anthranilate and sulisobenzone using 1H NMR confirms the presence of new photoproducts. The optimized structures and energies of both sunscreens, their excited state proton transfer (ESPT) tautomers, and the transition state between the ground state and ESPT tautomer of sulisobenzone were computationally determined.