Comparison of chemical components and antioxidant capacity of different Echinacea species

Alcoholic extracts of the roots and leaves of three Echinacea species (E. purpurea, E. angustifolia and E. pallida) were analysed for the presence of characteristic chemicals by HPLC directly coupled to ultraviolet absorbance and electrospray mass spectrometric detectors. The method permitted rapid characterization and tentative identification of a large number of caffeoyl conjugates and alkamides in all the samples investigated. The roots of the three species differed markedly in their contents of characteristic compounds. Cichoric acid and verbascoside predominated in extracts of E. purpurea root whereas cynarine and dodeca-2E,4E,8Z,10Z/E-tetraenoic acid isobutylamide were the major chemicals characteristic of E. angustifolia root extracts. Echinacoside and 6-O-caffeoylechinacoside predominated in extracts of E. pallida roots. Characteristic alkamides were also examined by electrospray tandem mass spectrometry (MS/MS) and these compounds provided characteristic fragmentation patterns. Extracts of the roots and leaves of all three species were found to have antioxidant properties in a free radical scavenging assay and in a lipid peroxidation assay.