Quercetin-Loaded Nanomedicine as Nutritional Application

The flavonol quercetin (3,3′,4′,5,7-pentahydroxyflavone) belongs to a class of plant secondary metabolites known as flavonoids. It exists in the daily diet of humans and is known for its numerous biological activities, including as anticancer, anti-infective, hepatoprotective agent, neuroprotective agent, antioxidant, and anti-inflammatory, and prevents cardiovascular disorders. Quercetin, because of its basic chemical structure, shows prominent antioxidant activity which possibly assists it to reduce free radicals from establishing resonance-stabilized phenoxyl radicals. However, poor aqueous solubility, chemical instability, and low oral bioavailability of quercetin have limited its applications. Quercetin digested in the human body (e.g., mouth, small intestine, liver, kidneys) suffers glucuronidation, sulfation, or methylation. To overcome these issues, nanoencapsulation of quercetin is performed which could significantly improve its stability, efficacy, and bioavailability. In this context, we have tried to discuss the utility of various quercetin-based nanoformulations including polymeric nanoparticles, lipid-based carriers, micelles, metallic nanoparticles, inclusion complexes, and conjugate-based encapsulation.