Harvest in different years of growth influences chemical composition of Echinacea angustifolia roots

Echinacea angustifolia DC., native from North America, is one of the three Echinacea species that are widely used as herbal remedy, mainly for their immunostimulant properties. Echinacoside, cynarin and alkylamides are the main constituents of the species. Five plants of two accessions (JA2 and JA9) of narrow-leaved coneflower were harvested from the second to the fifth year of cultivation and secondary metabolites content were determined in the whole root as well as in different samples such as the crown, cortex, internal tissue and thin roots. The highest content of marker compounds was found in the thin roots (0.20% for cynarin and 1.11% for echinacoside and from 0.29 to 0.44% for dodeca-2E,4E,8Z,10E/Z-tetraenoic isobutylamide) and in the root cortex (0.16% for cynarin and 1.01% for echinacoside and from 0.31 to 0.48% for dodeca-2E,4E,8Z,10E/Z-tetraenoic isobutylamide). Our results demonstrated that root cortex tissue accumulates the marker compounds, explaining why the thin roots present the higher amount of secondary metabolite. Regarding the entire roots, differences between the accessions (JA9 versus JA2, except for cynarin) and among the years were observed. The lowest and the highest echinacoside content was measured in the JA9 accession, in the second (0.39%) and in the fifth (1.47%) year of growing, respectively. The lowest and the highest dodeca-2E,4E,8Z,10E/Z-tetraenoic isobutylamide content was found in the third year, 0.43% in JA9 and 0.16% in JA2, respectively. The lowest and the highest cynarin content was obtained in the fourth year (0.11% in JA9) and in the fifth (0.22% in JA2), respectively. These results may be useful for Echinacea growers and processors to improve their agronomical and post-harvesting choices.