Validated method for the determination of six metabolites derived from artichoke leaf extract in human plasma by high-performance liquid chromatography-coulometric-array detection

A validated method was developed for the simultaneous determination of the hydroxycinnamates caffeic (CA), dihydrocaffeic (DHCA), ferulic (FA), dihydroferulic (DHFA), and isoferulic acid (IFA) and the flavonoid luteolin (LUT) in human plasma as metabolites derived from artichoke leaf extract. The method involves sample preparation followed by separation using high-performance liquid chromatography on reversed-phase material with a polar endcapping (Aqua-C(18), 250 x 4.6 mm). Selectivity and sensitivity towards the target compounds were achieved by electrochemical array detection (CoulArray). Calibration curves were constructed in the ranges 2.1-51.7 ng x mL(-1) (CA), 2.0-76.7 ng mL(-1) (DHCA), 2.2-53.7 ng x mL(-1) (FA), 2.1-79.2 ng x mL(-1) (DHFA), 1.1-52.6 ng x mL(-1) (IFA) and 2.1-258.6 ng x mL(-1) (LUT). Linearity could be shown for all target compounds over the entire calibration range. Values for within-day and between-day precision and accuracy were in accordance with the international guidelines for validation of bioanalytical methods. It is concluded that this newly developed method is appropriate for analysing samples from bioavailability and pharmacokinetic studies after oral administration of artichoke leaf extract.