Quantification of Cynaropicrin in Artichoke Leaf Extracts by 1H NMR Spectroscopy

The quantification of cynaropicrin in artichoke leaf extracts (ALE) by means of quantitative H-1 NMR was performed. The method relies on solid phase extraction for sample preparation and spectra acquisition in DMSO-d(6) containing anthracene as the internal standard. The obtained H-1 NMR spectra revealed excellent signal purity for H-13(b) of cynaropicrin, which was thus chosen for quantification. Validation was performed in terms of selectivity, linearity, precision, accuracy, and robustness. The content of cynaropicrin in the analyzed samples showed considerable variation, ranging from non detectable to 1.6%. The NMR approach does not rely on external calibration, which represents the major advantage compared to traditional approaches based on HPLC.