Antioxidant capacity of Rosa species: Optimised cyclic voltammetry method versus in vitro antioxidant properties and selected phytochemicals

The electrochemical method, cyclic voltammetry (CV), was used to examine the antioxidant properties of rosehip species. In order to optimise the CV method, scan speed (25, 50, and 75 mV/s) and pH (2, 4.5, and 7) were varied. Based on anodic current intensity, the optimal conditions were found to be 75 mV/s and pH = 4.5. Cyclic voltammograms were recorded in a potential range from 0 to 1,200 mV/s. The first and second anodic peak detected between 0.465 and 0.529 V, and between 0.707 and 0.782 V, could be attributed to oxidation of catechin-type flavonoids. The third peak, appearing between 0.951 and 1.056 V in the cyclic voltammograms of samples, corresponded to the oxidation of quercetin. A significant correlation was found between CV and in vitro antioxidant assays: FRAP (R2 = 0.7793, p < 0.00001), CV and CUPRAC (R2 = 0.7691, p < 0.00001), and between CV and total flavonoid content (R2 = 0.7611, p < 0.00001), as well as between CV and total phenolic content (R2 = 0.7080, p < 0.00001). The HPLC method was used for the identification of individual phenolic compounds. Principal component analysis (PCA) provided a classification of samples based on their individual phenolic content.