Amino Acid Carbamates As Prodrugs Of Resveratrol
Resveratrol (3, 5, 4′-trihydroxy-trans-stilbene), a plant polyphenol, has important drug-like properties, but its pharmacological exploitation in vivo is hindered by its rapid transformation via phase II conjugative metabolism. One approach to bypass this problem relies on prodrugs. We report here the synthesis, characterization, stability and in vivo pharmacokinetic behaviour of prodrugs of resveratrol in which the OH groups are engaged in an N-monosubstituted carbamate ester (-OC(O)NHR) linkage with a natural amino acid (Leu, Ile, Phe, Thr) to prevent conjugation and modulate the physicochemical properties of the molecule. We also report a convenient, high-yield protocol to obtain derivatives of this type. The new carbamate ester derivatives are stable at pH 1, while they undergo slow hydrolysis at physiological pH and hydrolyse with kinetics suitable for use in prodrugs in whole blood. After administration to rats by oral gavage the isoleucine-containing prodrug was significantly absorbed, and was present in the bloodstream as non-metabolized unaltered or partially deprotected species, demonstrating effective shielding from first-pass metabolism. We conclude that prodrugs based on the N-monosubstituted carbamate ester bond have the appropriate stability profile for the systemic delivery of phenolic compounds.
All compounds turned out to be highly stable at pH values close to that of the human stomach, no reaction occurring over 24 hours at 37 °C in 0.1 N HCl, and they underwent slow hydrolysis at near-neutral pH (pH 6.8, representing intestinal pH) thus ensuring protection of the phenolic moieties from first pass metabolism during absorption in the gastrointestinal tract. In contrast all the synthesized prodrugs hydrolyzed in murine whole blood, with kinetics suitable for use as prodrugs. (Sci Rep. 2015 Oct 14;5:15216. )