ELECTROCHEMICAL BEHAVIOR OF PHENOLIC ANTIOXIDANTS EXTRACTED FROM PAPAYA AND MANGO

Measurement of cyclic voltammetry (CV) and spectroelectrochemistry to phenolic antioxidants extracted from papaya and mango fruit were performed. CV measurements were achieved on a potensiostat (Autolab). All experiments were carried out with a three-electrode system. The phenolic solutions were 1 mM pH 7.0, and 0.1M KNO3. UV-Vis Spectroelectrochemistry test were performed on a UV-Vis spectrophotometer (Agilent). Tests were carried out on a potentiostat to apply the Eox during the UV-Vis scans. CV results show irreversible oxidation peaks in most cases and some cuasireversible (Figure 1). Chlorogenic acid, followed by caffeic and gallic  acid had the lowest oxidation potential while vanillic acid presented the highest potential followed by p-coumaric acid. Protocatechuic and ferulic acids presented an intermediate oxidation potential. Spectroelectrochemistry shows the absorption changes that support the formation of quinones by oxidation effect. We concluded that cyclic voltammetry and spectroelectrochemistry can be used to characterize the reducing ability and electrochemical behavior of phenolic antioxidant. We found that oxidation potential and antioxidant activity of phenolic studied are influenced by its chemical structure, -OH groups, number and position.