RESUMO
Oxidative stress has been implicated in many pathological conditions such as cancer, aging inflammation and cell death. The Brazilian flora is particularly rich in medicinal plants employed for many purposes. Among them the Piperaceae family and specially the "pariparobas" are widely used in the treatment of liver diseases. In vitro antioxidant activity of Pothomorphe umbellata L. Miq. was evaluated and compared with that of Piper regnellii, another plant from the Piperaceae family commonly used as it were P. umbellata. A purified fraction of the ethanolic extract of P. umbellata, containing 4-nerolidylcatechol was also assayed for antioxidant activity and compared with that of alpha-tocopherol. Rat brain homogenates were incubated with increasing aliquots of crude extracts of different parts of the plants or 4-nerolidylcatechol/alpha-tocopherol for 1 h at 37 degrees Celsius. Both malondialdehyde (MDA) and chemiluminescence (CL) were assayed to evaluate brain tissue autoxidation. The Q1/2 for MDA assay for root, stem and leaves were 4.4, 19.3 and 38.5 mug/mL for P. umbellata and 26.0,64.4 and 13.3 mug/mL for P regnellii, respectively. Calculated MDA and CL Q1/2 values for 4-nerolidylcatechol and alpha-tocopherol were O.75 and O.68 muM for 4-nerolidylcatechol and 14.4 and 1O.9 muM for alpha-tocopherol, respectively. These results indicate high antioxidant activity of P. umbellata root extract as compared to that of vitamin E, which was attributed to the presence of 4-nerolidylcatecho1.