Evaluating the Effect of Fresh and Aged Antioxidant Formulations in Skin Protection Against UV Damage

Introduction: Extrinsic skin damage is often a result of oxidative stress caused by exposure to environmental factors such as ultraviolet (UV) radiation, ozone (O3), and various pollutants. As a result, topical antioxidants have been evaluated for their effectiveness in mitigating or reversing skin damage caused by environmental factors. Topical antioxidants containing a combination of l-ascorbic acid, tocopherol, and ferulic acid have significantly improved markers of skin health after exposure to environment-induced skin damage. However, research suggests that l-ascorbic acid and tocopherol tend to be relatively unstable, possibly affecting their efficacy against outdoor stressor damage. It has been shown that ferulic acid significantly improves the stability of both l-ascorbic acid and tocopherol, but its long-term stabilization effects on these antioxidants are relatively unknown. Material and Methods: This study evaluated the time-dependent effectiveness of a topical antioxidant mix containing 15% l-ascorbic acid, 1% tocopherol, and 0.5% ferulic acid (AOX) on UV-induced skin damage. Skin biopsies (12 mm, n = 60) were placed in a 6-well plate with medium and incubated at 37 ◦C and 5% CO2 overnight. The day after, skin samples were pretreated with 10 µL of differently aged AOX (0-, 6-, 12-, and 36-monthold) and then exposed to different doses of UV light (100, 200, 400 mJ/cm2 ) daily over four days. AOX formulations were stored in a cool, dry, and dark place at approximately 20–22 ◦C during the whole study. This study evaluated 4-hydroxynonenal (4-HNE) and 8-hydroxy-2′ -deoxyguanosine (8-OHdG) as oxidative damage and skin DNA damage markers, Collagen1 and Filaggrin as skin structure, and IL-8 and Nrf2 as inflammatory and defensive response. Results: UV exposure significantly increased oxidative and inflammatory markers in human skin explants affecting also filaggrin and collagen levels. However, pre-treatment with the antioxidant formulation, particularly in its younger formulations (0-, 6-, and 12-month-old), significantly reduced the damaging effect of UV. Additionally, all antioxidant formulations effectively mitigated UV-induced damage across all doses. Conclusions: Our results indicate that pre-treatment with this formulation consistently reduces UV-induced oxidative damage and DNA damage in human skin explants, regardless of the formulation age and the discoloration state. Although effective, the protective capacity of aged formulations may be reduced only when extreme UV exposure is tested, a condition that is unlikely to occur under typical environmental conditions. These results support ferulic acid as a stabilization agent for topical antioxidant mixtures