The role of Hydrogen Bonding in sunscreen performance

Intramolecular H-bonding facilitates processes such as tautomerization and has significant impact on molecular spectroscopic behaviors and macroscopic properties. We explore how changes in H-bonding between two categories of ultraviolet (UV) filters impact their spectroscopic behaviors and their performance in commercial sunscreen formulations.

We explore first the case of methyl anthranilate (MA), a precursor to the now discontinued UV filter meradimate, which contains a N–H intramolecular H-bond. Using laser and static spectroscopy techniques, as well as computational studies, we created a detailed account of how the intramolecular H-bond influences MA’s spectroscopic behavior, including its performance within a commercial sunscreen formulation. In addition, we compare these results to equivalent ones for homosalate, a salicylate approved for use in commercial sunscreen formulations worldwide. Instead of the N–H bond in anthranilates, salicylates contain a O–H intramolecular H-bond.

Our work reveals key differences in the spectroscopy and chemical dynamics of anthranilates vs salicylates, with important implications for sunscreen performance. This work further highlights how fundamental science can inform product development in real-life applications.