Kinetic Profile of the Antioxidant Activity of Propolis Extract: 2,2-Diphenyl-1-Picrylhydrazyl Radical Bleaching Assay

The objective of this paper was to assess the antiradical effectiveness of propolis extract (PE) based on 2.2-diphenyl-1-picrylhydrazyl radical (DPPH•) bleaching assay kinetic profile. The kinetic profile of scavenging DPPH• for PE exhibited one kinetic period characterized by one kinetic constant. The second-order rate constant (k₂) for the oxidation of PE by DPPH•, determined for the first time in this study, was 0.17 dm³g⁻¹s⁻¹. The obtained k₂ value was compared to that of synthetic antioxidants and natural extracts used in the food industry. Kinetic analysis of PE antiradical effectiveness showed that the k₂ was within the range values for natural colorants of fruit extracts and should be considered as a fast acting natural antioxidant source. The k₂ parameter indicates the extent of oxidation inhibition that is based on all of the kinetic profiles of DPPH bleaching rather than single point measurements. For this reason, the kinetic analysis should become a necessary step for more precise antioxidative characterization of propolis.