Electrochemical sensors for the determination of polyphenols as antioxidants from natural sources: A comprehensive review of sensor development and characterization

The rapid, sensitive, and selective quantification of polyphenols has become increasingly important in areas such as food quality control, nutraceutical development, and biomedical diagnostics, due to their exhibiting significant antioxidant properties through their redox-active hydroxyl groups, contributing to a variety of pharmacological effects, including anti-inflammatory, cardioprotective, and chemopreventive activities. This review critically examines recent developments in electrochemical sensor platforms tailored for polyphenol detection in complex biological and environmental samples. Emphasis is placed on nanostructured electrode modifications employing carbon-based nanomaterials (e.g., graphene, carbon nanotubes), metal nanoparticles (Au, Ag, Pt), and metal oxide nanostructures (e.g., TiO₂, ZnO) that facilitate enhanced electron transfer rates, augmented electroactive surface area, and improved sensor stability and reproducibility. The review further explores diverse electrochemical transduction techniques, including cyclic voltammetry, square wave voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy, with comparisons of enzymatic and non-enzymatic sensing approaches. Detailed mechanistic insights into polyphenol electrooxidation pathways, adsorption phenomena, and sensor–analyte interfacial interactions are discussed. Complementary spectroscopic and microscopic characterization methods are highlighted for their roles in elucidating structural, electronic, and surface properties critical to sensor functionality and analytical performance.