Use of alpha-tocopherol esters for topical vitamin E treatment: evaluation of their skin permeation and metabolism

TLDR: The aim of this work was to investigate new pro‐vitamins based on α‐tocopherol (α‐Toc) and fatty acids, and to compare their properties with those of α‐ocopherol acetate ( α‐TAc).

Abstract: Objectives The aim of this work was to investigate new pro-vitamins based on a-tocopherol (a-Toc) and fatty acids, and to compare their properties with those of a-tocopherol acetate (a-TAc). Methods Skin levels of a-Toc–fatty acid ester conjugates, total a-Toc and endogenous a-Toc were measured in skin samples taken from separate groups of treated and untreated rats. Multiple and extensive treatment with a-Toc oleate and a-TAc was also carried out to assess the skin accumulation and safety of these esters. Key findings The in-vivo studies revealed that a-Toc–fatty acid conjugates penetrated into the skin quantitatively while being comparable with the permeation of a-TAc. Differences were found between the levels of total a-Toc and endogenous a-Toc after application of a-TAc, a-Toc oleate, a-Toc linoleate, a-Toc-a linolenate and a-Toc palmitate, indicating that a-Toc conjugates of these fatty acids, but not a-Toc g-linolenate or a-Toc stearate, were hydrolysed to free a-Toc. In long-term and extensive treatment, a-TAc was found to be lethal to rats treated with 1.15 mg/kg of this agent, which had been spread over 16 cm 2 of skin.