Electrochemical Measures for Determining the Total Antioxidant Capacity of Açaí Pulp (Euterpe oleracea) at a Glassy Carbon Electrode

Antioxidants, such as flavonoids, are influential secondary metabolites that play a significant role in regulating human health. Açaí, known for its potent antioxidant properties, has gained popularity in the nutritional field. However, there is a need for accurate methods to quantify its antioxidant capacity. Therefore, the goal of this investigation was to determine the total antioxidant capacity of frozen açaí pulp by applying the concept of the electrochemical quantitative index (EQI) using the cyclic voltammetry technique. The electrochemical response of ethanolic extracts obtained by a nonconventional ultrasound bath was investigated in the anodic region. The results clearly showed redox behavior at +0.37 V and +0.27 V (vs. Ag/AgCl) for the anodic and cathodic peaks, respectively, when evaluated by cyclic voltammetry at a glassy carbon (GC) electrode. By investigating a constant ethanolic extract concentration (0.2%) and analyzing the scan rate and supporting electrolyte effects, it was determined that the frozen açaí pulp extract presented an EQI of about 2.3 µA/V. Similarly, the concept of the EQI was extended to the use of the differential pulse voltammetry profile of a 0.2% ethanolic açaí extract on different supporting electrolytes, which showed that some experimental conditions needed improvement. Still, maintaining pH with a buffer solution in the anodic region is crucial to ensure reproducibility. The antioxidant capacity was also determined using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay to compare the electrochemical results. The Folin–Ciocalteu colorimetric test was applied to determine the total phenolic content of the extract.