In vitro antioxidant activity of Polygonium hyrcanicum, Centaurea depressa, Sambucus ebulus, Mentha spicata and Phytolacca americana.

Extracts of five plants were investigated for their total flavonoids, phenol contents and their radical scavenging activity using DPPH assays: Polygonium hyrcanicum, Centaurea depressa, Sambucus ebulus, Mentha spicata and Phytolacca americana. Quercetin and butylated hydroxy toluene were used as standard reference with well-documented antioxidant activity. Total flavonoid content in these plants ranged from 31.6 to 109.5 mg g(-1) and the amount of free phenolic compounds was between 32 and 287.5 mg g(-1) extract powder. Free phenolic compounds content were in the order: P. hyrcanium > M. spicata > S. ebulus > C. depressa > P. americana. It was also observed that all methanolic extract samples of studied plants showed free radical scavenging activity. The highest antioxidant activity was found in P. hyrcanium with an IC 50 equal to 0.036 mg mL(-1) that is higher than BHT (IC 50 = 0.054). A correlation between radical scavenging capacities of extracts with total phenolic compounds content was observed. This result indicates that P. hyrcanium contains high levels of phenolic compounds that may contribute to higher free radical scavenging activity compared to the other extracts of the plants in this study.