In vitro approaches to antioxidant screening for the development of a sunscreen formulation

The incorporation of antioxidants into sunscreens may provide additional skin photoprotection against the harmful photobiological effects of ultraviolet radiation. The present study evaluated the applicability of a screening approach to the assessment of the antioxidant and photoprotective properties of vitamin C, vitamin E, and coenzyme Q10 and then determined the performance of the most effective antioxidant in a sunscreen formulation. Antioxidant activity was assessed by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, 2,2`-azino-bis (3-ethylbenzothiazoline-6sulfonic acid) (ABTS) assay, and oxygen radical absorbance capacity (ORAC) assay, and the photoprotective potential was investigated by the yeast photoprotection assay. The antioxidant with the best effect was incorporated into sunscreen formulations which were evaluated for 120 days regarding their in vitro photoprotective parameters. Vitamin C showed high antioxidant capacity as well as a photoprotective potential against simulated solar irradiation applied for times longer than 1 h. Although the Sun Protection Factor, UVA/UVB ratio and critical wavelength did not differed significantly (p < 0.05) between the formulation blank and the formulations containing 0.5% or 1% vitamin C, formulations with vitamin C kept their photostability for 6 months. Consequently, the proposed screening approach seems to be promising for the development of an antisolar photostable formulation containing vitamin C as an antioxidant.