Intermolecular Interactions and In Vitro Performance of Methyl Anthranilate in Commercial Sunscreen Formulations

In order to afford the required level of broad-spectrum photoprotection against UV-B and UV-A radiation, sunscreens must contain a combination of UV filters. It is important that any interactions between UV filters do not adversely affect their photostability nor the overall photostability of the sunscreen formulation. In this work, we explore the feasibility of using methyl anthranilate (MA) as an alternative to the photo-unstable UV-A filter, avobenzone. From the in vitro studies presented here, we conclude that MA does not provide sufficient UV-A protection on its own but that it is more photostable in formulation than avobenzone. In addition, we found that both octocrylene (OCR) and ethylhexyl methoxycinnamate (EHMC), two commonly used UV-B filters, can stabilize MA through quenching of its triplet states, as previously reported, which has a demonstrable effect in formulation. In contrast with previously reported observations for mixtures of EHMC and avobenzone, we found no evidence of [2+2] photocycloadditions taking place between EHMC and MA. This work demonstrates how a clear insight into the photophysics and photochemistry of UV filters, as well as the interactions between them, can inform formulation design to predict sunscreen performance.