Abstract:

An attempt was made to incorporate alpha-tocopherol in negatively and positively-charged submicron emulsions, with the aim of providing an effective topical preparation against skin oxidative damage. In cell culture toxicity experiments using human fibroblast it was shown that the positively-charged alpha-tocopherol emulsion did not exhibit any toxic effect despite the low dilution and respective high concentration used. Negatively and positively-charged submicron emulsions of alpha-tocopherol and their respective blank emulsions were topically applied to rats that were subjected to UVA irradiation under different experimental conditions. No difference was observed between the negatively and positively-charged alpha-tocopherol submicron emulsions regarding the rate of oxidation and peroxyl radical scavenging ability of skin homogenates and both were able to protect rat skin against oxidative stress. However, in a non-invasive evaluation of the lipid hydroperoxidation process in rat skin following exposure to UVA irradiation, the positively-charged alpha-tocopherol submicron emulsion elicited a significantly better protective effect than the corresponding negatively-charged emulsion. These results suggest that the positively-charged emulsion exhibits a more prolonged residence time in the uppermost layers of the skin than the negatively-charged emulsion.