Design, Synthesis and in Vitro Evaluation of Vinyl Ester Type Polymeric Prodrugs of Salicylic acid

Vinyl ester polymeric systems linked to salicylic acid were synthesized and evaluated as materials for drug delivery. The carboxyl group of salicylic acid was converted into vinyl ester group by reacting salicylic acid with vinyl acetate in the presence of mercuric acetate as a catalyst. The resultant salicylic acid derivative of vinyl ester was then copolymerized with 2-hydroxyethyl methacrylate or methyl methacrylate by utilizing azoisobutyronitrile as an initiator at the temperature range of 65-70ºC. The structure of all compounds was characterized and confirmed by FTIR, 1H NMR, and 13C NMR spectroscopy techniques and elemental analysis. The resultant vinyl ester type polymeric prodrug containing salicylic acid was hydrolyzed in cellophane membrane dialysis bags containing aqueous buffered solutions at 37 oC and the quantity of the released drug was analyzed by UV spectrophotometer. The obtained release profiles show that drug could be released by hydrolysis of the ester bond and the hydrolytic behaviour of the polymeric prodrug is strongly based on the pH value of the hydrolysis solution