The electrochemical redox mechanism and antioxidant activity of polyphenolic compounds based on inlaid multi-walled carbon nanotubes-modified graphite electrode

The electrochemical redox mechanism of polyphenolic compounds (gallic acid [GA], caffeic acid [CA], ferulic acid [FA], and vanillic acid [VA]) were investigated by electrochemical methods at the inlaid multi-walled carbon nanotubes-modified graphite electrode (MWCNTs/GCE). The obtained micro-information such as the number of electrons and protons were used to deduce the electrochemical oxidation mechanism of four polyphenolic compounds. The antioxidation activities of these compounds were also studied by two methods. The radical scavenging activity followed the order: GA > CA > FA > VA, which was in agreement with the result from the spectrophotometry method. The result indicated that compounds with lower oxidation peak potential (E (pa)) showed stronger antioxidation activity. At the same time, compounds with high E (pa) showed lower antioxidant activity. The greater the number of hydroxyls linked to the aromatic ring, the greater the antioxidation activities of four compounds. Structural analysis of these phenolic-based compounds suggested that multiple OH substitutions and conjugations determine their free radical scavenging activity and electrochemical behavior.