Analytical, chemical, and biological perspectives on Quercetin: Structure, biosynthesis, extraction methods, and metal complexation-A review

Quercetin acts as an adsorbent due to its functional groups (-OH, C=O) and aromatic rings, binding via H-bonding and (π-π) interactions to remove pollutants such as toxic heavy metals (Hg²⁺, Cd²⁺) and phenolic compounds from water. Flavonoids represent a diverse group of plant-derived polyphenolic compounds known for their potent antioxidant properties and wide distribution in fruits and vegetables. Quercetin, a prominent flavanol, is notable for its dietary abundance and biological efficacy in mitigating oxidative stress. DPPH (2,2-Diphenyl-1-picrylhydrazyl) is a simple method for measuring antioxidant activity. Evidence suggests that quercetin inhibits lipid peroxidation, contributing to the prevention of chronic degenerative diseases; however, its absorption mechanisms and metabolic transformations remain incompletely understood. This review examines quercetin’s molecular structure, derivatives, and physicochemical properties, and discusses its in vivo antioxidant efficacy. Additionally, the biosynthesis of quercetin within plants is explored, highlighting the biochemical pathways involved. The study also addresses various laboratory methods for the extraction and purification of quercetin from diverse plant sources. Overall, this work aims to provide a comprehensive overview of the application of quercetin on extraction methods, metal complexation (quercetin-copper polymers, immobilized quercetin, heavy metal binding), preparation techniques, health benefits, and biosynthetic processes, thereby advancing the understanding of its mechanisms of action and potential applications in pharmaceutical and biomedical fields.