Amino Acid Derivatives as Palmitoylethanolamide Prodrugs: Synthesis, In Vitro Metabolism and In Vivo Plasma Profile in Rats

PLoS One. 2015 Jun 8;10(6):e0128699. doi: 10.1371/journal.pone.0128699. eCollection 2015.

Abstract

Palmitoylethanolamide (PEA) has antinflammatory and antinociceptive properties widely exploited in veterinary and human medicine, despite its poor pharmacokinetics. Looking for prodrugs that could progressively release PEA to maintain effective plasma concentrations, we prepared carbonates, esters and carbamates at the hydroxyl group of PEA. Chemical stability (pH 7.4) and stability in rat plasma and liver homogenate were evaluated by in vitro assays. Carbonates and carbamates resulted too labile and too resistant in plasma, respectively. Ester derivatives, prepared by conjugating PEA with various amino acids, allowed to modulate the kinetics of PEA release in plasma and stability in liver homogenate. L-Val-PEA, with suitable PEA release in plasma, and D-Val-PEA, with high resistance to hepatic degradation, were orally administered to rats and plasma levels of prodrugs and PEA were measured at different time points. Both prodrugs showed significant release of PEA, but provided lower plasma concentrations than those obtained with equimolar doses of PEA. Amino-acid esters of PEA are a promising class to develop prodrugs, even if they need further chemical optimization.

MeSH terms

  • Amides
  • Amidohydrolases / antagonists & inhibitors
  • Amidohydrolases / metabolism
  • Amino Acids / metabolism*
  • Animals
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology
  • Esters / chemical synthesis
  • Esters / chemistry
  • Ethanolamines / blood*
  • Ethanolamines / chemical synthesis*
  • Ethanolamines / chemistry
  • Ethanolamines / metabolism
  • Male
  • Palmitic Acids / blood*
  • Palmitic Acids / chemical synthesis*
  • Palmitic Acids / chemistry
  • Palmitic Acids / metabolism
  • Prodrugs / chemical synthesis
  • Prodrugs / metabolism*
  • Rats, Wistar

Substances

  • Amides
  • Amino Acids
  • Enzyme Inhibitors
  • Esters
  • Ethanolamines
  • Palmitic Acids
  • Prodrugs
  • palmidrol
  • Amidohydrolases
  • fatty-acid amide hydrolase

Grants and funding

The authors have no support or funding to report.