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 mg=mL)
compared with the values obtained for ascorbic acid
(IC50 ¼ 8.4 mg=mL) and gallic acid (IC50 ¼ 2.6 mg=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 30
,40
-
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.