Rapid and effective evaluation of the antioxidant capacity of propolis extracts using DPPH bleaching kinetic profiles, FT-IR and UV–vis spectroscopic data

An informative and effective measure of antioxidant capacity based on DPPH (2,2-diphenyl-1-picrylhydrazyl) bleaching kinetic profiles has been developed using principal component analysis (PCA). The activity score and a related parameter, called quercetin factor (QF), were used to estimate antioxidant capacity for 39 propolis extracts based on the first principal component (which explains 98% of the total variance). Determination of the QF parameter requires less time and reagents than previous DPPH-based antioxidant capacity parameters, but does require additional equipment. Additionally, UV–vis and FT-IR spectroscopic features of propolis extracts have been identified, which have been correlated to antioxidant capacity, and offer a spectroscopic and reagent-less rapid evaluation method of the antioxidant activity of biological samples. Together the QF scores based on DPPH bleaching and FT-IR and UV–vis spectra are analyzed in terms of antioxidant capacity, floral origin, and geographic location.