Influence of grape seed oil on sun protection factor in sunscreen formulations: a study using Central Composite Design approach

This study aimed to evaluate the influence of the grape seed oil (GSO) on the sun protection factor (SPF) of sunscreen emulsified formulations containing butyl methoxydibenzoylmethane (avobenzone (AVO)) and octyl methoxycinnamate (OMC) developed by phase inversion temperature (PIT) employing a Central Composite Design. Formulations were prepared by PIT emulsification process. Seventeen emulsions containing different amounts of GSO, AVO and OMC were obtained according to experimental design. In vitro SPF was determined using a spectrophotometric method. As expected, formulations with the highest concentrations of UV filters, AVO and OMC, resulted in the highest SPF values, while the lowest SPF values were obtained by formulations containing concentrations of these filters below the central point. In the tested concentrations, the variable OMC and its combination with GSO showed to influence the SPF linearly as a function of their concentrations in formulations. The combination of GSO with OMC contributed to increase in vitro SPF. The use of natural compounds with antioxidant activity, such as GSO, is a viable strategy to increase the effectiveness of sunscreens to protect the human skin against UV-induced damage.