Sustained Effect of Two Antioxidants (Oxothiazolidine and δ-Tocopheryl Glucoside) for Immediate and Long-Term Sun Protection in a Sunscreen Emulsion Based on Their Different Penetrating Properties

The study investigated the skin absorption and antioxidative effects of a sunscreen containing oxothiazolidine (OTZ) and δ-tocopheryl glucoside (DTG) on a reconstructed human epidermis model. OTZ was found to be rapidly absorbed and provided immediate antioxidative protection, but this effect was short-lived. In contrast, DTG was absorbed more slowly and converted into δ-tocopherol, offering prolonged antioxidative effects over at least 24 hours. The combination of OTZ and DTG in the sunscreen formulation provided immediate protection from OTZ and sustained protection from DTG, with the highest level of protection occurring 2 hours after solar irradiation and remaining constant for 24 hours. This suggests that the two antioxidants work complementarily for both immediate and long-term skin protection against oxidative stress induced by sunlight.