Skin absorption and metabolism of a new vitamin E prodrug, delta-tocopherol-glucoside: in vitro evaluation in human skin models.

The aim of this study was to investigate the cutaneous penetration and metabolism of the new vitamin E prodrug delta-tocopherol glucoside (delta-TG), as compared to those of common vitamin E acetate, in vitro, both in reconstituted human epidermis and in viable human skin. Better diffusion was observed with alpha-tocopherol acetate (alpha-TAc) than with delta-tocopherol glucoside in both skin models, at 0.1% and 0.05% in a myritol solution; however, no metabolism was detected with alpha-tocopherol acetate. In all conditions tested (two skin models, two concentrations, three test times, and compartmental analysis) the delta-tocopherol glucoside was metabolized into free tocopherol. In the reconstituted human epidermis, after 18 h, over 90% of the delta-tocopherol glucoside was bioconverted. In the viable human skin, the extent of metabolism was about 20%, with 0.12 and 0.10 microg/cm2 of delta-tocopherol glucoside in the stratum corneum and epidermis, respectively. After topical application, the delta-tocopherol glucoside had a considerable reservoir effect, associated with gradual delivery of free tocopherol. The use of this gluco-conjugated vitamin E at a low concentration shows the capability of the skin to metabolize the prodrug in a slow and prolonged manner, making this gluco-conjugated vitamin E an excellent candidate for continuous reinforcement of antioxidants in the skin.