Influence of Shea (Butyrospermum parkii) butter, TiO2 and ethylhexyl methoxycinnamate on physical parameters and in vitro photoprotective efficacy

Background The development of photoprotective lipsticks containing natural bioactive compounds is a relevant current strategy to increase sun protection factor (SPF) value and lower the concentration of chemical UV filters, known for promoting sensitivity reactions. Aims Twelve photoprotective lipsticks were developed by Design of Experiment (DOE) and characterized to verify the influence of Shea butter (Butyrospermum parkii), titanium dioxide (TiO2), and ethylhexyl methoxycinnamate (EHM) on physical parameters and in vitro photoprotective efficacy. Methods The influence of Shea butter, TiO2, and EHM was evaluated by several parameters, such as melting point, colorimetry, thermal analysis by DSC, texture analysis, and sunscreen activity estimated in vitro. Results The construction of prediction models was possible for the following responses: maximum force by the cantilever test at 25 and 45 degrees C; maximum distance by hardness test at 25 degrees C; slope value at 25 and 45 degrees C by the cantilever test; and UVA/UVB ratio and in vitro SPF. TiO2 and EHM contributed to changes on the in vitro SPF value; however, unexpectedly, Shea butter had no influence on this efficacy parameter. Conclusion The assay allowed us to observe the influence of the variables in the analysis and to develop a response prediction model for some of the parameters assessed.