Simultaneous determination and characterization of flavonoids, sesquiterpene lactone, and other phenolics from Centaurea benedicta and dietary supplements using UHPLC-PDA-MS and LC-DAD-QToF.

Simultaneous identification and quantification of phenolic acid (chlorogenic acid), sesquiterpene lactone (cnicin), lignan (arctiin), and flavonoids (bracteoside, 6-methoxybracteoside, isokaempferide, and viscosine) in mixed parts of Centaurea benedicta (Syn. Cnicus benedictus) were performed for the first time. The liquid chromatography method showed an adequate performance for the separation of seven compounds. The method was validated for linearity (0.5-100 μg/mL), precision, accuracy, limit of detection (LOD), and limit of quantification (LOQ) as well as robustness. Cnicin and arctiin were detected at concentrations as low as 0.25 µg/mL. Remaining flavonoids and chlorogenic acid were detected at 0.025 μg/mL. The method demonstrated good performance in terms of intra- and inter-day precision (0.1-3.4%), accuracy (98.0-105.0%), lower and upper limits of quantification for all compounds. Analysis of various samples showed considerable variation of 0.9-10.3 mg/g for the marker compound, cnicin. Twenty-one dietary supplements, claiming to contain C. benedictus extract, were analyzed for authenticity. Thirteen (62%) of 21 products showed the presence of all analyzed compounds and were confirmed to contain C. benedictus. A liquid chromatography-tandem mass spectrometry method coupled with electrospray ionization (ESI) is described for the identification of compounds in plant samples. This method involved the use of protonated, deprotonated, and adduct ions for compounds in positive and negative ion modes with extractive ion chromatogram (EIC). The application of liquid chromatography-quadrupole time of flight mass spectrometry (LC-QToF) provided useful information to characterize sixty-four compounds. The developed methods were also applicable for quality assessment of raw materials and dietary supplements containing C. benedictus.