Photostabilization of organic UV-absorbing and anti-oxidant cosmetic components in formulations containing micronized manganese-doped titanium oxide

Micronized titanium oxide (TiO 2 ) and manganese-doped titanium oxide (TiO 2 :Mn) particles have been incorporated into a variety of oil-in-watet (O/W) and water-in-oil-in-water (W/O/W) emulsions in conjunction with the UV-absorbing organic compounds butyl methoxydibenzoylmethane (BMDM) and octyl methoxycinnamate (OMC) and with the anti-oxidants vitamin E and vitamin C. The retention of the organics under solar exposure has been shown to be significantly enhanced by the addition of TiO 2 :Mn to the formulation. In the case of BMDM and OMC, the retention is increased from 20% and 24% to 63% and 8.3%, respectively, after two hours of solar exposure. In this system, TiO 2 particles are shown to provide only limited protection relative to BMDM and OMC. Vitamin E and vitamin C are actively degraded by the presence of TiO 2 in the emulsion during solar exposure. This effect is reversed with TiO 2 :Mn, the use of which can protect >90% ofanti-oxidants in both the oil and water phases of the formulation. The absence of reactive oxygen species (ROS) generation and surface scavenging of ROS by TiO 2 :Mn is responsible for a significantly reduced ROS load on the organic components and consequent photostabilization of the emulsion.