Full Length Research Paper

Study on antioxidant activity of Echinacea purpurea L. extracts and its impact on cell viability

Tzu Tai Lee¹, Chung Li Chen², Zhao Han Shieh³, Jun Chen Lin⁴ and Bi Yu³*

¹Department of Biotechnology, Ming Dao University, Changhau, Taiwan 52345, Taiwan.

²Department of Agronomy, National Chung Hsing University, Taichung, Taiwan 40227, Taiwan.

³Department of Animal Science, National Chung Hsing University, Taichung, Taiwan 40227, Taiwan.

⁴Animal Industry Division, Council of Agriculture, Executive Yuan, Taipei, Taiwan 10014, Taiwan.

*Corresponding author. E-mail: byu@dragon.nchu.edu.tw. Tel: +886-4-22860799. Fax: +886-4-22860265.

Accepted 27 August, 2009

   Abstract

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°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 (Fe²⁺) 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 (ED₅₀) 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 ED₅₀ 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 IC₅₀ 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.

Key words: Medicinal plant, Echinacea purpurea L., antioxidant, cell viability.