There is a large chemical variability between commercially available Echinacea for both research and consumption impacts on the quality and efficacy of these products. Globally, herbal industries are largely unregulated, leaving manufacturers responsible for quality control. Several recent efforts to improve regulation have created a need for rapid, accurate, and reliable assays suitable for a quality control setting. Thus, the aim of this study was to develop and validate a high-performance thin-layer chromatographic (HPTLC) method for the quantitative analysis of commercial Echinacea products. HPTLC and high-resolution plate imaging were used to separate and quantify the amounts of three phenylpropanoid compounds which were used then as markers in product quality assessment. The developed method was validated according to the current International Conference on Harmonization (ICH) guidelines in terms of accuracy, precision, linearity, specificity, limits of quantification and detection, and robustness and was used to quantify these markers in three commercial Echinacea formulations. The method achieved better limits of detection than previous assays, despite exhibiting lower repeatability, particularly when quantifying cichoric acid. This work has demonstrated that high-resolution plate imaging can be used as a reliable method for the quantitative analysis of commercial Echinacea products.
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