Exploring antioxidant reactivity and molecular structure of phenols by means of two coupled assays using fluorescence probe (2,3-diazabicyclo[2.2.2]oct-2-ene, DBO) and free radical (2,2-diphenyl-1-picrylhydrazyl, $$\hbox {DPPH}^{\cdot }$$ DPPH · )

Abstract

Phenolic compounds can be considered as the most important bioactive compounds in Mediterranean diet. However, many of the complex connections between phenols antioxidant reactivity and their molecular structure remain unsolved. To shine light on these issues, the antioxidant reactivity of 15 relevant phenolic compounds was studied. Two different analytical approaches were combined: (a) the well-established 2,2-diphenyl-1-picrylhydrazyl $$(\hbox {DPPH}^{\cdot }$$ ) stable free radical assay, and (b) the 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) fluorescent probe assay. The results obtained confirm how certain structural features (i.e., hydroxyl and methoxy groups, alkyl and alkenyl chains) play a critical role in the singular antioxidant response exhibited by each phenolic compound. This knowledge provides decisive information to select a specific phenolic compound as an antioxidant additive or for the chemical design of new antioxidants. Synopsis (for Contents page): Interactions between DBO (fluorescence quenching) and DPPH (radical scavenging) with fifteen phenolic compounds, which are present in olive oil and wine, served as a measure of antioxidant activity of the phenols and correlated to the molecular structure.