Vitamin C and 6-amino-vitamin C conjugates of diclofenac: synthesis and evaluation.
Diclofenac (Diclo), its ascorbic acid (AA) or 6-amino-AA (AA-NH2) pro-drugs (AA-Diclo or AA-NH-Diclo) were prepared and evaluated on human retinal pigment epithelium (HRPE) cells to investigate their ability to interact with the vitamin C transporter SVCT2 and their cellular uptake. Furthermore, stabilities in physiological fluids of these compounds were investigated. For kinetic experiments, AA-Diclo was incubated in Tris-HCl buffer, human plasma or whole blood. The extracted samples were analysed by HPLC. AA-Diclo was hydrolysed following first order kinetics in buffer, plasma (t1/2 about 10 h) and whole blood (t1/2 about 3.5 h). Transport and inhibition assays were performed by adding [14C]AA and the above-mentioned unlabelled compounds to plated HRPE cells. Intracellular accumulation was measured incubating HRPE cells with increasing concentrations of unlabelled compounds, following by HPLC analysis. Diclo resulted as a non-competitive inhibitor of AA-transport, showing a Na+-dependent and ascorbate-independent uptake. AA-Diclo behaved as a competitive inhibitor, but it was not transported into cells, whereas its analogue AA-NH-Diclo showed a decreased inhibitory activity. Stability studies suggest AA-Diclo as a potential candidate to enhance the Diclo short half life in vivo. The discovery of a Na+-dependent transporter for Diclo on HRPE cells opens new perspectives for targeting diclofenac into the brain.
Dalpiaz
A
A
Dipartimento di Scienze Farmaceutiche, Università di Ferrara, via Fossato di Mortara 19, 44100 Ferrara, Italy. dla@dns.unife.it
Pavan
B
B
Scaglianti
M
M
Vitali
F
F
Bortolotti
F
F
Biondi
C
C
Scatturin
A
A
Manfredini
S
S
D001205:Ascorbic Acid / Q000031:analogs & derivatives / Q000737:chemistry*; D001692:Biological Transport; D002250:Carbon Radioisotopes; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D004008:Diclofenac / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics*; D004337:Drug Carriers / Q000138:chemical synthesis / Q000493:pharmacokinetics; D004353:Drug Evaluation, Preclinical / Q000379:methods; D006207:Half-Life; D006801:Humans; D029363:Organic Anion Transporters, Sodium-Dependent / Q000493:pharmacokinetics; D011355:Prodrugs / Q000138:chemical synthesis / Q000493:pharmacokinetics; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters / Q000493:pharmacokinetics; D013997:Time Factors
D002250:Carbon Radioisotopes; D004337:Drug Carriers; D029363:Organic Anion Transporters, Sodium-Dependent; D011355:Prodrugs; C555163:SLC23A2 protein, human; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; D004008:Diclofenac; D001205:Ascorbic Acid