This study investigates the antioxidant activity of Echinacea Purpurea L. (EP) extracts and its impact on cell viability. The polysaccharides content of EP was 159.8 +/- 12.4 mg/g dry weight (DW), with extracts obtained by applying 55% ethanol at 55 degrees C containing 11.0 +/- 1.0 mg gallic acid equivalent/g DW of total phenolic compound. Trolox equivalent antioxidant capacity, 0.1 mg/mL of EP extracts exhibited only 30% when compared to the ascorbic acid at the same concentration. Reducing power of extracts increased linearly with its concentration and the concentration at 2.0 mg/mL reached about 65% of ascorbic acid at 0.3 mg/mL. The chelating capacity of ferrous iron (Fe(2+)) was 70% as good as that of the synthetic metal chelater EDTA when added to 5.0 mg/mL of EP extracts. The DPPH scavenging capacity showed 85.1% at 0.5 mg/mL of extracts and with half-effective doses (ED(50)) was measured at 0.23 mg/mL. The superoxide anions scavenging capacity of EP extracts was nearly equivalent to ascorbic acid (91.1% vs 93.0%) at the same concentration of 1.6 mg/mL and ED(50) was 0.32 and 0.13 mg/mL, respectively. Microculture tetrazolium assays showed extracts had 92% cell viability at 1.6 mg/mL for chicken's peripheral blood mononuclear cells (PBMCs) and 84% for RAW 264.7 macrophages, neither reaching the IC(50) level. In summary, the EP extracts had antioxidant activity similar to that of ascorbic acid, but have no serious effect on inhibiting chicken's PBMCs viability
