Echinacea purpurea is known worldwide for its immunomodulatory and anti-inflammatory properties and, together with Echinacea angustifolia and Echinacea pallida, has been widely used as a medicinal plant in herbal medicines. The extracts of these species have a highly complex chemical composition that includes polar compounds (caffeic acid derivatives or CADs), nonpolar compounds (alkylamides and acetylenic secondary metabolites; essential oils), and high molecular weight constituents (polysaccharides and glycoproteins) that have demonstrated to possess interesting biological activities, particularly an immunostimulatory effect capable of modulating various pathways of the immune system.
Main active compounds
While quite large differences can occur depending on genetic and climatic variability, the most common active compounds described in Echinacea are caftaric acid, cichoric acid, chlorogenic acid, caffeic acid, cynarin and echinacoside, but the abundance of each compound may also vary by plant organ such as leaves, roots, or flowers.
Cichoric acid, along with caftaric acid, is the most important CAD of E. purpurea. Cynarin is specific to the roots of E. angustifolia, while echinacoside is a characteristic phytochemical of E. pallida and E. angustifolia but is absent or present only in trace amounts in the aerial and underground organs of E. purpurea. Chlorogenic acid is present in minimal amounts in all Echinacea species.
Several commercial products, ranging from direct pressed juices to ethanolic extracts of whole Echinacea plants or powdered dried roots, leaves and flowers are available in pharmacies and health food stores. Commercial Echinacea products, which are marketed as medicines should have known concentrations of the bioactive compounds. However, the analysis of samples of Echinacea raw material and various products is complex and requires standardized approach to guarantee the quality of the product.
Quantification of the main active compounds remains an important feature in the study of Echinacea and plays an important role in defining quality and authenticity. Different screenings of Echinacea commercial products have highlighted a lack of standardization that may be attributed to fraudulent or misguided commercial practices, the natural diversity of plant sources, and/or the instability of CADs during storage and extraction. These facts make the availability of reliable analytical methods a necessity for research as well as commercial and regulatory purposes.
A variety of spectroscopic, electrophoretic and different chromatographic methods are available for identification and quantification of Ehinacea components. For reliable quantification of Echinacea compounds, development and validation of a suitable and robust method for sample preparation and analysis of Echinacea extracts is essential.
Routine analysis
In our laboratory, we have developed and validated a selective and sensitive HPLC-UV method for the content determination of the main active compounds in Echinacea plant raw materials and in various extracts and food supplements, focusing on the primary bioactive marker component of E.purpurea, the chicoric acid.
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