|WURTELE, EVE SYRKIN|
Submitted to: Planta Medica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/16/2008
Publication Date: 2/24/2009
Citation: Wu, L., Dixon, P.M., Nikolau, B.J., Kraus, G.A., Widrlechner, M.P., Wurtele, E. 2009. Metabolic Profiling of Echinacea Genotypes and a Test of Alternative Taxonomic Treatments. Planta Medica. 75:178-183.
Interpretive Summary: Purple coneflowers, the genus Echinacea, have long been used as an herbal medicine to treat a variety of ailments. The genus includes a number of different species, with three that are commonly consumed. To gain a better understanding of the biochemical variation among the different species, forty different populations were selected to represent a wide range of geographic origins and morphological diversity. Seedlings from these populations were grown under controlled conditions in a greenhouse. Chemical constituents were extracted from fresh roots harvest from these seedlings, which were then analyzed via high-pressure liquid and gas chromatography, and mass spectroscopy. In total, 43 different lipophilic (ones that dissolve in lipids) compounds were detected, including 24 unknowns and 19 that could be precisely identified. Multivariate statistical analyses were then used to see which compounds tended to co-occur and which Echinacea populations had the most similar arrays of compounds. This allowed us to test two alternative taxonomic treatments of the genus. A widely-used system developed by McGregor, based primarily on morphological features, more closely agreed with the dendrogram generated from our data than did a system more recently developed by Binns et al. Our data also support the hypothesis that pale purple coneflower, Echinacea pallida, is a diverse polyploid, incorporating both the genome of Echinacea simulata and of another species, possibly Echinacea sanguinea. Finally, nearly all of the recognized species can be identified by their distinct lipophilic compound fingerprints. These data should be useful to herbal medicine researchers and producers for providing chemical baselines to help standardize Echinacea products, for identifying plant material of unknown origin or species found in commercial products, and for finding new genetic sources to select for increased production of desired bioactive compounds.
Technical Abstract: The genus Echinacea is used as an herbal medicine to treat a variety of ailments. To better understand the potential chemical variation among members of this genus, forty accessions of Echinacea were selected to encompass a broad geographical and morphological diversity. Seeds from these accessions were germinated and grown under controlled conditions. Analysis of metabolites of roots from these accessions was carried out by HPLC-photo diode array (HPLC-PDA), GC-MS, and multivariate statistical analyses. In total, 43 lipophilic metabolites, including 24 unknown compounds, were detected. Weighted principal component analysis (WPCA) and clustering analysis of the levels of these metabolites across Echinacea accessions, based on Canberra distances, allowed us to test two alternative taxonomic treatments of the genus, with the further goal of facilitating accession identification. A widely-used system developed by McGregor based primarily on morphological features was more congruent with the dendrogram generated from the lipophilic metabolite data than the system more recently developed by Binns et al. Our data support the hypothesis that Echinacea pallida is a diverse allopolyploid, incorporating the genomes of Echinacea simulata and another taxon, possibly Echinacea sanguinea. Finally, most recognized taxa of Echinacea can be identified by their distinct lipophilic metabolite fingerprints.