A novel co-monomer based on Ellagic Acid for free radical polymerization of N-vinyl-2-pyrrolidone

INTRODUCTION Ellagic Acid (EA) is one of the most abundant and relevant antioxidants present in fruits such as berries and in pomegranate [1]; on the other hand, its poor solubility both in water and in organic solvents limits its reactivity and its use as food supplements. The aim of the present work is to modify the structure of the EA in order to use it as co-monomer for radical polymerization of N-vinyl-2-pyrrolidone (NVP) achieving two main goals: protection of antioxidant moiety; different release pathway. MATERIALS AND METHODS EA was reacted with methacryloyl chloride via a hetero-phase reaction in anhydrous CH2Cl2 to obtain a high purity tetra-ester allyl derivate (EAMAC). Polymers were then obtained via bulk photopolymerization of N-vinyl-2-pyrrolidon with different quantities of EAMAC in a square-shaped PTFE mold for 1h. The release assay was performed using hydrolytic and enzymatic conditions. RESULTS AND DISCUSSION EAMAC is the only product obtained since other partially substituted esters (i.e. mono-, bi- and three-esters) are not present: it was obtained with high yield (≈80%w/w) and was fully characterized via 1H-NMR and MS [ESI-Q-Tof MS= 587.48 m/z (EAMAC + Na+)]. Thermal properties were assessed via DSC obtaining a single melting peak at 263°C: degradation starts immediately after melting. EAMAC was used as a co-monomer for NVP bulk photopolymerization; the reaction was performed avoiding the use of photoinitiator. It was observed that the irradiation with UV of EAMAC starts the reaction of polymerization transferring the radical to the NVP. Cross-linked polymers containing different amount of EAMAC were obtained. The release of EA was assessed both using solutions having different pHs and via enzymatic hydrolytic conditions. CONCLUSIONS The reaction of EA with methacryloyl chloride leads to obtain a single, reactive derivate of EA able to react with vinyl monomers, that is highly soluble in organic solvents. Moreover, EAMAC acts as radical initiator avoiding the use of photoinitiator and it leads to obtain crosslinked water-compatible polymers. EA can be released from the polymer and the kinetic of the release is related to the kinetic of the hydrolysis of the ester bonds existing between EA and methacrylic moieties bonded to polyvinyl pirrolydone (PVP) chains. REFERENCES [1] Verotta, L.; Panzella, L.; Antenucci, S.; Calvenzani, V.; Tomay, F.; Petroni, K.; Caneva, E.; Napolitano, A. Fermented pomegranate wastes as sustainable source of ellagic acid: antioxidant properties, anti-inflammatory action, and controlled release under simulated digestion conditions. Submitted to Food Chemistry, 2017 ACKNOWLEDGEMENT Work supported by Fondazione Cariplo and Regione Lombardia for the project ‘‘BIOPLANT’’.