1 research outputs found
Ethylene Glycol-Linked Amino Acid Diester Prodrugs of Oleanolic Acid for PepT1-Mediated Transport: Synthesis, Intestinal Permeability and Pharmacokinetics
The purposes of this study were to expand the structure
of parent
drugs selected for peptide transporter 1 (PepT1)-targeted ester prodrug
design and to improve oral bioavailability of oleanolic acid (OA),
a Biopharmaceutics Classification System (BCS) class IV drug. Through
an ethoxy linker the carboxylic acid group of OA was conjugated with
the carboxylic acid group of different amino acid promoieties to form
six diester prodrugs. The effective permeability (<i>P</i><sub>eff</sub>) of prodrugs was screened by in situ rat single-pass
intestinal perfusion (SPIP) model in two buffers with different pH
(6.0 and 7.4) as PepT1 employs a proton-gradient as the driving force.
Compared to OA, 2.5-fold, 2.3-fold, 2.2-fold, 2.1-fold, and 1.9-fold
enhancement of <i>P</i><sub>eff</sub> in buffer with pH
6.0 was observed for l-Phe ester (<b>5c</b>), l-Val ester (<b>5a</b>), l-Lys ester (<b>5e</b>), d-Phe ester (<b>5d</b>), and d-Val ester
(<b>5b</b>), respectively. Furthermore, <i>P</i><sub>eff</sub> of <b>5a</b>, <b>5c</b>, <b>5d</b> and <b>5e</b> in pH 6.0 was significantly higher than that in pH 7.4
(<i>p</i> < 0.01), respectively. These results showed
that the H<sup>+</sup> concentration of perfusion solution had great
effect on the transport of the prodrugs across intestinal membrane.
For the further evaluation of affinity to PepT1, inhibition studies
were performed by coperfusing 0.1 mM prodrug with 50 mM glycyl-sarcosine
(Gly-Sar, a typical substrate of PepT1). It turned out that the <i>P</i><sub>eff</sub> of <b>5a</b>, <b>5b</b>, <b>5c</b> and l-Tyr ester (<b>6f</b>) significantly
reduced in the presence of Gly-Sar (1.7-fold, 2.2-fold, 1.9-fold,
and 1.4-fold, respectively). We supposed that it may be attributed
to PepT1 mediated transport of these prodrugs. <b>5a</b> and <b>6f</b> were selected as the optimal target prodrugs for oral absorption <i>in vivo</i>. Following intragastric administration of 300 mg/kg
(calculated as OA) <b>5a</b>, <b>6f</b> and OA in three
groups of rats, compared with group OA, <i>C</i><sub>max</sub> for the group of <b>5a</b> and <b>6f</b> was enhanced
by 1.56-fold and 1.54-fold, respectively. <i>F</i><sub>app</sub> of group <b>5a</b> and <b>6f</b> was 2.21- and 2.04-fold
increased, respectively, indicating that <b>5a</b> and <b>6f</b> had better oral absorption than OA. The combined results
also suggest that diester prodrugs which conjugated two carboxylic
acid groups of proper amino acid promoieties and parent drug through
a linker can be used for PepT1-targeted prodrug design. With this
strategy, oral bioavailability of OA in rats could be improved significantly