An integrated strategy for holistic quality identification of Chinese patent medicine: Liuwei Dihuang Pills as a case study.

Abstract

Liuwei Dihuang Pills (concentrated pills, simplified as LWDHP), one of the most famous classic Chinese Patent Medicine (CPM), is produced by hundreds of pharmaceutical manufacturers with billions of Chinese yuan (CNY) in annual sales. However, current quality identification of LWDHP mainly relies on a thin-layer chromatography (TLC) method that is complicated and deficient. The goal of this study is to simplify the identification process and provide a more comprehensive quality assessment method of LWDHP by developing an integrated strategy based on liquid chromatography coupled with mass spectrometry (LC-MS) and multivariate statistical analysis. Ultra-high-performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UHPLC/QTOF-MS) was employed to perform qualitative analyses of a home-made LWDHP and to establish a stably characteristic compound library by analysis of batches of its component herbs. Then selective ion monitoring (SIM) of single MS was utilised to develop a rapid identification method based on the UHPLC/QTOF-MS analysis result. Multivariate statistical analysis was subsequently used for the quality assessment of different commercial samples. Seventy-eight characteristic compounds were characterised, and 68 of them were recorded to establish a stably characteristic compound library. Thirty-one compounds were selected from the library for the establishment of SIM identification method. Good specificity, capability, and feasibility had been respectively verified by the analysis of blank sample, negative control (NC) preparation samples, home-made LWDHP sample, and commercial sample. Multivariate statistical analysis of 20 batches of commercial LWDHP samples revealed the quality consistency of the same vendor's product and quality difference between diverse vendors' products. The SIM identification method by a single analysis could significantly simplify the identification process of LWDHP, and it was performed in a holistic mode for no less than two compounds of each component herb monitored. Moreover, it could also be combined with multivariate statistical analysis to conduct quality assessments of batches of samples. The integrated strategy used in the study of LWDHP could be applied for the identification of other CPM as well.