Starch-quercetin conjugate by radical grafting: synthesis and biological characterization.

A novel flavonoid-polysaccharide conjugate was synthesized by free radical grafting of quercetin on starch. The covalent insertion of quercetin in the polymeric chain was confirmed by FT-IR, DSC and fluorescence analyses, while an estimation of the amount of quercetin bound per g of polymer was obtained by the Folin-Ciocalteu assay. The conjugate shows improved UV stability and retains the antioxidant properties of free quercetin, such as scavenging activity towards free radicals (DPPH and peroxynitrite); inhibition of the free radical formation (peroxidation of linoleic acid) and total antioxidant activity. The conjugate also prevented drug degradation and shows potential health functionality in the treatment of Alzheimer disease, diabetes and as skin-whitening agent.