Development of Quercetin-DHA Ester-Based Pectin Conjugates as New Functional Supplement: Effects on Cell Viability and Migration

A quercetin derivative with remarkable biological performance was successfully synthesized by chemical modification of the flavonoid with docosahexaenoic acid to synthesize 2-(2,2-diphenylbenzo[d][1,3]dioxol-5-yl)-5,7-dihydroxy-4-oxo-4H-chromen-3-yl-(4Z,7Z,10Z,13Z,16Z,19Z)-docosa-4,7,10,13,16,19-hexaenoate (3), deeply characterized by NMR spetroscopy. Modified quercetin and pectin were involved in a grafting process by an ecofriendly radical procedure able to preserve the biological features of the quercetin derivative. Antioxidant performances of the conjugate were evaluated both in term of total phenolic amount and scavenger activity in organic and aqueous environments. Additionally, in vitro acute oral toxicity was also tested against Caco-2 cells and 3T3 fibroblasts, confirming that pectin conjugate does not have any effect on cell viability at the dietary use concentrations. Finally, in vitro experiments highlighted the ability of the conjugate to counteract the migratory properties of Caco-2 and HepG2 cells, indicating its feature in the reduction of the migration of tumour cells. These data showed that the covalent binding of the quercetin derivative to the pectin chain represents a very interesting strategy to improve the bioavailability of the quercetin, representing an effective means of protecting and to transporting polyphenol molecules.