Conjugation of aspirin with vitamin C: uptake and stability studies

Aspirin and its prodrug obtained as conjugate with vitamin C (AA-Asp) were evaluated on human retinal pigment epithelium (HRPE) cells to investigate their ability to interact with the ascorbate transporter SVCT2 and their cellular uptake. Furthermore, stability in physiological fluids of these compounds was investigated. Transport and inhibition assays were performed by adding [14C]AA and the unlabeled compounds to plated HRPE cells. Intracellular accumulation was measured by incubating HRPE cells with the compounds, followed by HPLC analysis. For kinetic experiments, aspirin and AA-Asp were incubated in phosphate buffer, human plasma and whole blood. Aspirin was taken up into HRPE cells even though it was not able to interact with SVCT2; AA-Asp resulted as a competitive inhibitor of AA-transport weakly taken up into HRPE cells. AA- Asp resulted as a prodrug of aspirin when incubated in whole blood, but not when incubated in plasma: in this case the main metabolic product was salicylic acid.