Alpha-tocopherol pro-vitamins: synthesis, hydrolysis and accumulation in rabbit ear skin

J Control Release. 2004 Oct 19;99(3):403-13. doi: 10.1016/j.jconrel.2004.08.002.

Abstract

We synthesized esters of alpha-tocopherol (VE) with the aim to develop new pro-vitamins, easily reconverted by enzymes in the skin and able to release another active moiety such as an amino acid, in order to obtain a synergic effect. In particular, the attention was dedicated to the amino acids glycine and alanine and to pyroglutamic acid. The sensitivity of pro-vitamins to enzymatic hydrolysis was evaluated in vitro using porcine liver esterase. Permeation experiments were performed using rabbit ear skin, for the quantification of pro-vitamins and derived VE in the epidermis and dermis. The new derivatives synthesized, and in particular the glycine and alanine derivatives, accumulated in rabbit skin in a significant extent and originated substantial amounts of alpha-tocopherol. In comparison with the acetate derivative (VEAc), the amounts accumulated are comparable or higher. Moreover, the new derivatives, being more hydrophilic, allow the use of vehicles such as the mixture water/propylene glycol/ethanol widely employed for the preparation of creams and gels. Finally, the enzymatic metabolism of these new derivatives generates not only VE, but also components that can have a further advantageous action on skin.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / analogs & derivatives
  • Alanine / chemical synthesis
  • Alanine / metabolism
  • Animals
  • Chemistry, Pharmaceutical / methods
  • Dosage Forms
  • Drug Evaluation, Preclinical / methods
  • Ear / pathology*
  • Esterases / metabolism
  • Glycine / analogs & derivatives
  • Glycine / chemical synthesis
  • Glycine / metabolism
  • Hydrolysis*
  • Liver / enzymology
  • Permeability / drug effects
  • Prodrugs / chemical synthesis*
  • Prodrugs / metabolism
  • Prodrugs / pharmacology
  • Pyrrolidonecarboxylic Acid / analogs & derivatives
  • Pyrrolidonecarboxylic Acid / chemical synthesis
  • Rabbits
  • Skin / chemistry
  • Skin / drug effects
  • Skin / metabolism*
  • Skin Absorption / drug effects
  • Skin Absorption / physiology
  • Swine
  • Tissue Distribution
  • Tocopherols
  • alpha-Tocopherol / analogs & derivatives*
  • alpha-Tocopherol / chemical synthesis*
  • alpha-Tocopherol / metabolism
  • alpha-Tocopherol / pharmacology

Substances

  • Dosage Forms
  • Prodrugs
  • Esterases
  • alpha-Tocopherol
  • Alanine
  • Tocopherols
  • Pyrrolidonecarboxylic Acid
  • Glycine