A new and effective evaluation method for Radix Gentianae Macrophyllae herbs based on 2‐phenylethyl β ‐ <scp>d</scp> ‐glucopyranoside, 2‐methoxyanofinic acid and gentioxepine by UPLC–QTOF–MS exploring and HPLC–DAD quantification

Radix Gentianae Macrophyllae (RGM) is a traditional Chinese medicine belonging to the Gentiana genus and including four species of herbs. Owing to the lack of characteristic constituents, it is difficult to discriminate RGMs of different origins or even differentiate between herbs in the same genus. The current research aimed to explore the characteristic aromatic compounds, verify their significance in distinguishing different origins of RGM herbs and provide a simple and effective quality evaluation method. A selective extraction method was developed for noniridoid compounds and the extract was then subjected to UPLC-QTOF-MS analysis to obtain the RGM-MS ion pair database for noniridoid components. An HPLC-DAD quantitative analysis method was further developed based on characteristic aromatic compounds (2-phenylethyl β-d-glucopyranoside, 2-methoxyanofinic acid and gentioxepine) after the ion screening in the MS database. By means of principal component analysis and hierarchical clustering analysis analysis, the significant relationship between aromatic compounds contents and different species of RGM was revealed. As a result, the significance of 2-phenylethyl β-d-glucopyranoside, 2-methoxyanofinic acid and gentioxepine in distinguishing four species of RGM herbs was verified and a sensitive and reproducible HPLC-DAD method was established using these markers, which can be used for the classification and quantitative analysis of RGMs.