Development of chalcones structure‐related to avobenzone: Photoprotection, photostability, and safety evaluation

Abstract Chalcones are α,β‐unsaturated ketones with extended π‐conjugation, making them promising scaffolds for the development of organic UV filters. In this study, a series of substituted chalcones inspired by the chemical structure of avobenzone (AVO) was synthesized and systematically evaluated for UV absorption profiles, photostability, antioxidant potential, photoprotection, and safety‐related properties. Among the compounds, the 2‐hydroxychalcones 3ca and 3cb showed the most promising profiles. Chalcone 3ca exhibited λ max at 365 nm, critical wavelength of 386 nm, UVA/UVB ratio of 6.3, and molar absorptivity of 58,880 M −1 cm −1 , whereas 3cb showed λ max at 353 nm, critical wavelength of 376 nm, UVA/UVB ratio of 3.2, and molar absorptivity of 28,900 M −1 cm −1 . Both compounds fulfilled broad‐spectrum protection criteria and showed <5% degradation after UVA and UVB irradiation, with photostability comparable to benzophenone‐3 and superior to AVO. Formulations containing 3ca and 3cb reduced UVA‐induced DNA damage by 90.4% and 95.1%, respectively. Skin permeation studies demonstrated predominant retention in the stratum corneum (94.1% for 3ca and 97.4% for 3cb ), minimal penetration into viable epidermis and dermis, and no detectable compound in receptor fluid. Both chalcones showed no relevant irritation in the HET–CAM assay and no significant alterations in skin biometric parameters after topical application. Collectively, these findings support the potential of hydroxy‐substituted chalcones as photostable broad‐spectrum UV filters for topical application.