Antioxidant activity and total phenolic content of some Brazilian species

The antioxidant activity of extracts and fractions of six vegetal species from the Brazilian Atlantic Forest were determined. The total antioxidant activity was assessed based on the scavenging activity of the stable DPPH free radical. Eight extracts or fractions of plants showed significant DPPH scavenging activity (IC50 <= 10.0 mu g/mL) compared with the values obtained for ascorbic acid (IC50 = 8.4 mu g/mL) and gallic acid (IC50 = 2.6 mu g/mL). The extracts or fractions were as follows: ethanol extracts of leaves, flowers, and stems of Baccharis illinita DC., ethanol extracts of leaves and stems of B. platypoda DC., hydroalcoholic extract and ethyl acetate fraction of leaves of Cyathea phalerata Mart. and hydroalcoholic extract of bark of Trichilia catigua A. Juss. Seven flavonoids present in the plant extracts were also investigated. The most active compounds were taxifolin, quercetin, and luteolin, which possess the catechol group 3',4'-diOH. In addition, the total phenolic or flavonoid contents of these extracts and fractions were evaluated. The phenolic content of the sample was determined using Folin-Ciocalteu reagent and varied from 489.07 to 11.29 mg/g dry weight expressed as gallic acid equivalents (GAE). The total flavonoid concentrations, detected using 2% aluminum chloride, varied from 61.82 to 5.6 mg quercetin equivalents (QE)/g dry weight. These results suggest that the level of antioxidant activity in these plants varies by a great extent. They also suggest that the phenolic content in these plants provides substantial antioxidant activity. The flora of Brazil appears to be a rich and interesting source for supplementary ethnomedical and phytochemical studies.