Echinacea standardization:: Analytical methods for phenolic compounds and typical levels in medicinal species

A proposed standard extraction and HPLC analysis method has been used to measure typical levels of various phenolic compounds ir;the medicinally used Echinacea species. Chicoric acid was the main phenolic in E. purpurea roots (mean 2.27%) summer, (1.68% autumn) and tops (2.02% summer, 0.52% autumn), and echinacoside was the main phenolic in E. angustifolia (1.04%) and E. pallida roots (0.34%). Caftaric acid was the other main phenolic compound in E. purpurea roots (0.40% summer, 0.35% autumn) and tops (0.82% summer, 0.18% autumn), and cynarin was a characteristic component of E. angustifolia roots (0.12%). Enzymatic browning during extraction could reduce the measured levels of phenolic compounds by >50%. Colorimetric analyses for total phenolics correlated well with the HPLC results for E. purpurea and E. angustifolia, but the colorimetric, method gave higher values.