Chalcone Derivatives: Antioxidant Activity, Photoprotective Properties, and Stability under UV Irradiation

The development of multifunctional photoprotective agents capable of combining ultraviolet (UV) radiation absorption, photostability, and antioxidant activity represents a major challenge in cosmetic science. In this study, a series of 14 chalcone derivatives was synthesized and evaluated for their antioxidant and photoprotective potential. The chalcones, synthesized via the Claisen-Schmidt condensation, were evaluated for their antioxidant activity through DPPH, FRAP, and cyclic voltammetry assays, revealing that compounds 6, 7, and 12 exhibited the highest free radical scavenging capacity, reducing power, and inhibition of lipid peroxidation, with electrochemical data confirming facile oxidation via proton-coupled electron transfer. Photoprotective assessment by the Mansur method demonstrated that these chalcones showed moderate sun protection factor values, with absorption in both UVA and UVB regions and critical wavelengths (λ_c) compatible with broad-spectrum filters. Photostability assays under prolonged UVA irradiation highlighted Chalcone 6 (Chal 6) as exceptionally stable, maintaining its initial absorbance and complete structural integrity even after 72 h of continuous exposure, as monitored by ¹H NMR. Other chalcones underwent partial trans-cis isomerization accompanied by reduced absorbance. The remarkable stability of Chal 6, combined with its antioxidant profile, suggests its potential as a promising candidate for multifunctional sunscreen formulations capable of overcoming the current limitations of unstable UVA filters.