Stability and efficacy of sunscreens containing inorganic filters and quercetin

Exposure to the sun can have health benefits, however, excess exposure can cause skin damage, such as skin cancer. Photoprotection can be used as a preventive method against the harmful effects of the ultraviolet (UV) radiation and Brazilian biodiversity is a fertile field for research in this area. Therefore, the aim of this study was the development of sunscreens containing quercetin (bioactive compound) and inorganic filters (titanium dioxide and zinc oxide) with further characterization of the formulae and evaluation of stability. Formulations containing the bioactive compound, isolated or in association with the inorganic filters, presented: pH values biocompatible with the skin; apparent viscosity between 10550 and 23600 cP; sun protection factor (SPF) between 2.1 and 22.5; and broad spectrum protection, with critical wavelengths above 379 nm. It was found that the association of quercetin with inorganic filters was not adequate due to the negative interactions that occurred between the bioactive compound and the metals, which were only identified during the stability study. However, considering the in vitro estimated efficacy of the isolated flavonoid, its use can still be explored as an alternative substitute to classic UV filters.