Oxidized quercetin inhibits α-synuclein fibrillization

► Oxidized quercetin inhibits fibrillization of α-synucein more strongly than quercetin does. ► Quercetin disaggregates α-synucein fibrils. ► Quercetin inhibits fibrillization and stabilizes oligomers. ► Quercetin binds with α-synucein in 1:1 ratio. ► Increased hydrophilicity of quercetin and α-synucein adducts accounts for inhibition.