Photodegradation of avobenzone: stabilization effect of antioxidants.

Avobenzone is one of the most common UVA-filters in sunscreens, and is known to be photounstable. Some of the strategies used to stabilize this filter present some drawbacks like photosensitization reactions. Antioxidants are widely used as cosmetic ingredients that prevent photoageing and complement the photoprotection offered by the UV-filters preventing or reducing photogenerated reactive species. The purpose of this work was to study the effect of antioxidants in the photostabilization of avobenzone. The filter dissolved in dimethyl sulfoxide or incorporated in a sunscreen formulation was irradiated with simulated solar radiation (750 W/m(2)). The tested antioxidants were vitamin C, vitamin E, and ubiquinone. The area under the curve of the absorption spectrum for UVA range and the sun protection factor (SPF) were calculated. Vitamin E (1:2), vitamin C (1:0.5) and ubiquinone (1:0.5) were the more effective concentrations increasing the photostability of avobenzone. In sunscreen formulations, the most effective photostabilizer was ubiquinone which also promoted an increase in SPF. This knowledge is important to improve effectiveness of sunscreen formulation. Antioxidants can be valuable ingredients for sunscreens with a triple activity of filter stabilization, SPF boosting and photoageing prevention.