Controlled release of huperzine A from biodegradable microspheres: In vitro and in vivo studies

This paper describes the effect on Sun Protection Factor (SPF) of the combination of inorganic and organic filters in sunscreen products as determined by an in vitro method. O/W emulsions containing inorganic filters, such as titanium dioxide and zinc oxide, combined with 18 EU-authorized UV-B organic filters were tested. SPF measurements were carried out using a spectrophotometer equipped with an integrating sphere.

This study observed a synergic effect when titanium dioxide was combined with either anisotriazine or octyldimethylPABA. The combination of zinc oxide with 11 UV-B organic filters also exhibited a similar synergy; however, the measured SPF was systematically lower than the protection factor achieved with titanium dioxide.