The importance of pH for the formation of stable and active quercetin–polyamidoamine dendrimer complex

Abstract The purpose of this study was to investigate the effect of pH on the complexation of quercetin and polyamidoamaine (PAMAM) dendrimers, which can exert antioxidant activity in aqueous solution. The therapeutic use of quercetin has been limited due to its low water solubility and bioavailability. In this study, quercetin was complexed with generation 4 PAMAM (G4) in different buffers at pH 4–9, with pH 6 showing the best results in terms of solubility and stability. The solubility of quercetin in 0.1 M phosphate buffer at pH 6.0 containing 1% G4 was over 1 mg/ml. The antioxidant and neuroprotective activities of water‐soluble G4–quercetin complex (G4‐Q) were comparable to those of free quercetin dissolved in methanol. In conclusion, this study indicates that the complexation of quercetin with PAMAM dendrimers was optimized at pH 6 and the complex exhibits good water solubility, strong antioxidant activity, and neuroprotective activity.