Preparation and intestinal absorption of L-Dopa-D-phenylglycine

L-Dopa-D-phenylglycine was synthesized in this laboratory as L-dopa derivative for improving its intestinal absorption. As designed for transport through the intestine via oligopeptide transporter (PepT1), the competition of this dipeptide with known substrates for PepT1 in brush-border membrane vesicle (BBMV) was investigated. At the presence of L-Glycinyl-L-proline (L-Gly-L-Pro), L-Glycinyl-L-phenylalanine (L-Gly-L-Phe) or cephradine, the uptake of L-dopa-D-phenylglycine in BBMV was reduced to 54.1 ± 4.5%, 57.6 ± 5.2% or 62.9 ± 10.2%, respectively. The inhibition by these dipeptides and the tripeptide mimetic amino-β-lactam was significantly higher than by amino acids L-Phenylalanine (L-Phe) or L-dopa. The results suggested that the intestinal H ⁺-coupled PepT1 was involved in the uptake of L-dopa-D-phenylglycine. The steady state plasma concentrations of L-dopa-D-phenylglycine and L-dopa in rats after a single pass in-situ jejunal perfusion with 0.1 mM perfusate were 104.0 ± 12.90 μg/mL and 1.24 μg/mL respectively. L-Dopa-D-phenylglycine demonstrated a 50.1 fold higher plasma concentration, in terms of molar ratio, than that of L-dopa. D-Phenylglycine was proved to be a satisfactory moiety for the improvement of L-dopa absorption in the intestine.