Rapid identification of polymethoxylated flavonoids in traditional Chinese medicines with a practical strategy of stepwise mass defect filtering coupled to diagnostic product ions analysis based on a hybrid LTQ-Orbitrap mass spectrometer.

INTRODUCTION The methodology of stepwise mass defect filtering (MDF) approach coupled to diagnostic product ions (DPIs) analysis on a hybrid linear trap quadrupole (LTQ)/orbitrap mass spectrometer was the first to be established to screen and identify structural analogues from complex herbal extracts. OBJECTIVE To develop an analytical methodology that could be adopted to screen and identify structural analogues in traditional Chinese medicines (TCMs) rapidly and accurately. METHODS Taking polymethoxylated flavonoids (PMFs) in the leaves of Citrus reticulata Blanco as an example, high-resolution mass data were acquired by high-performance liquid chromatography (HPLC) coupled with a LTQ/orbitrap mass spectrometer. The stepwise MDF with multiple mass defect windows or mass windows enabled the original data to be analysed much faster and more accurately by reducing the potential interferences of matrix ions. Additionally, analysis of DPIs could provide a criterion to classify the target constituents detected into certain chemical families. RESULTS In total, 81 PMFs, including 50 polymethoxyflavones and 31 polymethoxyflavanones or polymethoxychalcones, were screened and identified from the original data and preliminarily identified. CONCLUSION The analytical methodology developed could be used as a rapid, effective technique to screen and identify compounds from TCM extracts and other organic matter mixtures with compounds that can also be classified into families based on the common carbon skeletons.