Antioxidant and prooxidant activities of phenolic compounds of the extracts of Echinacea purpurea (L.)

Abstract: Background and objectives: In recent years, there is a growing interest on natural and safer antioxidants. So far, little is known about the cytotoxic and (anti) oxidative potential of echinacea (Echinacea purpurea) extracts. Methods: In order to evaluate the antioxidant activity of extracts, total phenolics content and the scavenging capacity on DPPH˙ radicals was determined. The ability of extracts to scavenge superoxide and hydroxyl radicals was tested using electron paramagnetic resonance (EPR) techniques. Also, the extracts were screened for cytotoxicity and antioxidative/prooxidative potential by neutral red and DCFDA assay respectively, using human colon cancer cell line SW480. The cells were exposed to various concentrations of extracts (range: 0, 008 ; 0, 08 ; 0, 8 ; 1 ; 10 i 20 mg/mL) and different treatment times (2, 3, 4 and 24 h). Results: The content of total phenolic compounds of extracts of E. purpurea was 10.57%GAE. The scavenging activity of radicals was found to exhibit 50% of the inhibition value (IC50 value) at the concentration of 15.67 μg/ml for the investigated echinacea extract. Also, the calculated value of 210 mg/ml for hydroxyl and 76.7 mg/ml for superoxide anion radical indicates that the Echinacea extract is rich in antioxidant compounds that neutralize investigated radical species. In in vitro experiments, echinacea extract showed prooxidant effect at lower concentrations and shorter incubation period when SW480 cell line was used as test system. The highest concentration was also the most toxic which is particularly evident after 24 hours of treatment. Conclusions: Echinacea extracts are shown to possess the strong antioxidant potential.