Ferulic acid photoprotective properties in association with UV filters: multifunctional sunscreen with improved SPF and UVA-PF

Ultraviolet (UV) radiation stimulates several injurious biological effects on cutaneous tissue, causing, for instance, photocarcinogenesis. Sunscreens are topical products designed to protect the skin against these harmful effects and their use must be encouraged. The addition of antioxidants, as ferulic acid (FA), a phenolic compound from the class of the hydroxycinnamic acids, in sunscreens could improve their sun protection factor (SPF) and prevent inflammatory reactions. Here, the clinical safety and efficacy of an association of ethylhexyl triazone and bis-ethylhexyloxyphenol methoxyphenyl triazine (UV filters) with ferulic acid were assessed. Samples had good skin biocompatibility and presented satisfactory safety profile, even in a sun-exposed condition. A synergic effect between the natural polyphenol and the UV filters was evidenced, as well as, FA increased in vivo SPF in 37% and the UVA protection factor (UVA-PF) in 26%. The in vivo data indicated that FA reinforced the broad-spectrum characteristic of the photoprotective formulations. Additionally, according to the results from the ex vivo antioxidant test, it is plausible to recommend adjustments on the ex vivo protocol to explicitly determine the positive effects of topical antioxidant ingredients applied over the skin. These results provided a new perspective for the development of multifunctional bioactive sunscreens using FA as a new platform.