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Eugenia dysenterica DC (cagaiteira) is a native tree from Cerrado biome. Cagaita fruits are known and consumed in natura, mainly by inhabitants from Cerrado. In this study, we evaluated the antioxidant activity of leaves of this plant. For this evaluation we used four methods, the reduction of phosphomolybdenum, scanning by hydrogen peroxide, DPPH radical scavenging assay and determination of electrochemical parameters by differential pulse voltammetry. The results indicate that all extracts from leaves of this species have significant antioxidant potential, following the order: crude ethanol extract CEE)crude aqueous extract (CAE)crude hexane extract (CHE). The voltammetric approaches were also applied in order to evaluate the redox behavior of the hydrophilic extracts, as well as of their sub-extracts. Thus, the results suggest the presence of catechol-like polyphenols, which were confirmed by chromatography and phytochemical methods. Voltammetric analysis showed to be a reliable and fast method to determine redox behavior of E. dysenterica extracts.

Laccase is a poliphenoloxidase enzyme that catalyzes the oxidation of phenolic compounds in the corresponding quinones. The current obtained in this redox process can be used for quantitative analysis. In this work, a carbon paste biosensor modified gluteraldehyde functionalized silica and an enzymatic extract of the Pycnoporus sanguineus fungi as a lacase source is proposed for phenol determination. The effect of carbon paste and electrolyte composition, pH from 3.0 to 8.0, start potential from 0.55 to 0.25 mV, scan rate from 5 to 25 mV s-1 and potential pulse amplitude from 10 to 60 mV on the differential pulse voltammetric response was investigated. A linear correlation of r² = 0.9946 was obtained for the phenol content (catechol) in the concentration range from 50 to 500 nmol L-1, with a detection limit of 30 nmol L-1. This biosensor was used for the determination of different kinds of phenolic compounds, presenting a better response for catechol.