Structure‐Photoprotective Capacity Relationship of Phenolic Hydroxyl, Methoxy, and Ethenyl Linker Moieties of Phenolic Acids

As constituents of many plants, polyphenols can neutralize free radicals. By inactivating free radicals, skin homeostasis can be restored, which may prevent further damage and premature skin aging. To prevent the damage caused by UV exposure, photoprotection is becoming increasingly important. Plants known to be rich in polyphenols have been investigated for their use as sunscreens. The synergistic effect, which is due to the specific composition of plant extracts, is a disadvantage for applications such as large-scale sunscreens. The great diversity of polyphenols present in such plants can be an obstacle to the identification of the most effective polyphenol families. Investigating polyphenol families by family could provide more information than plant extracts with various polyphenols and a multitude of other molecules. In this study, we focused on the phenolic acids subclass. Eleven phenolic acids have been investigated for their potential use as sunscreen. According to its Boots Star rating or to its critical wavelength, p-coumaric acid shows good potential for use as a sunscreen especially for exposure to UVB radiation. The absence of cytotoxicity of coumaric acid on normal human dermal fibroblasts (NHDF), even at high concentrations, further validates the potential use of this acid in sunscreen formulations.