Antioxidant activity and low cytotoxicity of extracts and isolated compounds from Araucaria angustifolia dead bark.

The antioxidant activities of the extract and its relevant fraction as well as isolated compounds from the dead bark of Araucaria angustifolia are presented. This tree represents the Mixed Ombrophile Forest, which is endangered due to extensive logging. The dead bark of Araucaria is naturally discarded by the tree, and its hydroalcoholic crude extract has exhibited protective qualities against stress induced by H(2)O(2) in cell culture. Using several in vitro models, here we describe the antioxidant potential of the crude extract and its component ethyl acetate fraction and also of some compounds isolated from the ethyl acetate fraction. We provide the first description of the isolation of two natural product afzelechin derivatives. The extract and isolated compounds, particularly epiafzelechin protocatechuate (5), displayed very high antioxidant activity, as did compound 4, quercetin, which is well known for its antioxidant properties. In a DPPH assay, compound 5 exhibited an IC(50) of 0.7 μM; in a lipid peroxidation assay; IC(50) values of 21 μM and 35 μM were obtained when the oxidation was induced by UV and ascorbate free radicals, respectively.