Development and validation of a rapid ultra-high performance liquid chromatography diode array detector method for Verbena officinalis L.

This study presents a fast and validated ultra-high performance liquid chromatography diode array detector (UHPLC-DAD) method for the simultaneous determination of the major compounds in Verbena officinalis L. (Verbenaceae), a medicinal plant listed in the European, British, and, Chinese Pharmacopoeias. In order to get reference substances, nine compounds, belonging to iridoids, flavonoids, and phenylpropanoid glycosides, were isolated from the herb extract. Two of them, namely cistanoside D and leucosceptoside A, were found in this plant species for the first time. Chromatographic separation was achieved in less than 7 min on a Kinetex  1.7 u XB-C18 (50 × 2.10 mm) column by using a solvent gradient of water-acetonitrile modified with 0.1% formic acid. Method validation confirmed the assays sensitivity, linearity (R ≥ 0.997), precision (intraday precision ≤ 1.71%; interday precision ≤ 1.46%) and accuracy (recovery rates between 93.9% and 108.8%) for the quantitative analysis of the eight selected marker compounds. Identity and peak purity of the analytes was confirmed by coupling the UHPLC instrument to a quadrupole time-of-flight mass spectrometer via an electrospray ionization interface (ESI-QTOF-MS) operating in the negative ionization mode. Finally, the applicability of the developed UHPLC-DAD method was successfully proven for the sensitive quantitation of the major compounds in Verbena herb extracts, thereby providing a reliable tool for its rapid quality control.