Characteristics of juglone (5-hydroxy-1,4,-naphthoquinone) using voltammetry and spectrophotometric methods

•Juglone is irreversibly oxidized in at least one electrode step.•Juglone is reduced quasi-reversibly in at least three electrode steps.•Energy levels were confirmed by quantum chemical calculations.•In the reverse-bias cycle of the CV, two peaks are visible.•Juglone is characterized by very high thermal resistance. The objective of this work was to analyse the antiradical capacity of juglone (5-hydroxy-1,4,-naphthoquinone). The influence of oxidation and reduction on juglone was investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), as well as spectrophotometric based methods. The role of juglone in oxidation processes, as either an antioxidant in browning reactions, was examined. These processes are characterized by a high chemical reactivity in redox. Juglone is irreversibly oxidized in at least one electrode step and reduced quasi-reversibly in at least three electrode steps. These results demonstrate that walnut genotypes have different radical scavenging powers. In addition, on the basis of thermogravimetry, it was demonstrated that 5-hydroxy-1,4-naphthalenedione has high thermal stability above 500 °C. The generation of reactive oxygen species and activity in redox processes show the properties of naphthoquinones that render these compounds interesting leads for the development of novel biomolecules for potential use in various therapeutic settings.