Identification and quantification of phytochemicals in nutraceutical products from green tea by UHPLC–Orbitrap-MS
Authors: Noelia López-Gutiérrez and Roberto Romero-González and Patricia Plaza-Bolaños and José Luis Martínez Vidal and Antonia Garrido Frenich
A method has been developed and validated for the simultaneous detection and quantification of phytochemicals in nutraceutical products obtained from green tea. For that purpose, ultra-high performance liquid chromatography coupled to single-stage Orbitrap high resolution mass spectrometry (UHPLC–Orbitrap-MS) has been used. A database containing 37 compounds has been used for the detection and identification of the target compounds. The developed methodology was based on solid–liquid extraction, using a mixture of methanol:H2O (80:20, v/v, pH 4), followed by dilution (10 times) with a mixture of ammonium acetate:methanol (50:50, v/v). Chromatographic conditions were optimised and full scan accurate mass data acquisition using electrospray ionisation in positive and negative ion mode was used. Moreover, all-ion fragmentation mode was used to get information of fragment ions, and they were used for identification purposes. The developed method was validated, obtaining repeatability (intra-day) and inter-day precision values (expressed as relative standard deviation, RSD) lower than 16% and 20%, respectively. Lower limits were also evaluated and limits of detection (LODs) ranged from 1 to 50 μg L−1, while limits of quantification (LOQs) ranged from 2 to 150 μg L−1. Recovery was performed at five levels and it ranged from 70% to 109%. Finally, this method was used to evaluate the phytochemical content in 10 samples (tablets or capsules), showing concentrations of (+)-catechin, (−)-epicatechin, gallic acid, (−)-gallocatechin and quercetin-3-O-rutinoside, ranging from 258 (C6) to 10,729 (C6) mg kg−1.