Objectives
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‐tocopherol acetate (α‐TAc).
Methods
Skin levels of α‐Toc–fatty acid ester conjugates, total α‐Toc and endogenous α‐Toc were measured in skin samples taken from separate groups of treated and untreated rats. Multiple and extensive treatment with α‐Toc oleate and α‐TAc was also carried out to assess the skin accumulation and safety of these esters.
Key findings
The in‐vivo studies revealed that α‐Toc–fatty acid conjugates penetrated into the skin quantitatively while being comparable with the permeation of α‐TAc. Differences were found between the levels of total α‐Toc and endogenous α‐Toc after application of α‐TAc, α‐Toc oleate, α‐Toc linoleate, α‐Toc‐α linolenate and α‐Toc palmitate, indicating that α‐Toc conjugates of these fatty acids, but not α‐Toc γ‐linolenate or α‐Toc stearate, were hydrolysed to free α‐Toc. In long‐term and extensive treatment, α‐TAc was found to be lethal to rats treated with 1.15 mg/kg of this agent, which had been spread over 16 cm2 of skin. Similar treatment with α‐Toc oleate did not produce any side effects.
Conclusions
This study suggests that α‐Toc conjugates with unsaturated fatty acids may be a good alternative as stable vitamin E derivatives, rather than the α‐TAc ester.