Assessment of the photo-degradation of UV-filters and radical-induced peroxidation in cosmetic sunscreen formulations

Abstract

Photo-instability of common UV-filters is a well documented phenomenon. This study develops a method for concomitant measurement of photostability and photo-induced ROS generation in cosmetic formulations. Oil-in-water formulations containing three common UV filters (OMC, BMDBM, EHT), individually or combined, were further supplemented with phosphatidylcholine and exposed to UVA. All filters show spectral decrease after UVA exposure. OMC and EHT do not induce significant lipid-peroxidation (as measured by TBARS production) while BMDBM does. In the latter case, this is reduced when BMDBM is combined with OMC but not with EHT. Neither OMC nor EHT stabilize BMDBM with respect to loss of absorbance. ROS-generation assessed via TBARS formation was supported by EPR experiments. The UV-induced changes in UV-filter performance, as monitored in the model formulations and in commercial sunscreens, demonstrate that this is a simple and effective method for stability assessment of sunscreen filters under conditions of use.

Keywords::

• UV-filters
• photostability/instability
• lipid peroxidation
• sunscreen formulations
• UV protection

Declaration of interest: The authors thank the Polytechnic University of the Marche and CIBA Specialty Chemicals Incorporation, Basel, Switzerland for financial support. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This paper was first published online on Early Online on 31 December 2009.