Holistic quality evaluation of compound liquorice tablets using capillary electrophoresis fingerprinting combined with chemometric methods

Abstract

With the popularity of herbal medicines (HMs) throughout the world, their quality is becoming a key issue. Because of the complicated phytochemical matrices and characteristic synergistic effect caused by the presence of multi-components, the quality control of HMs is facing great challenges. Compound liquorice tablets (CLQTs) have a long history as a Chinese herbal formula to treat cough and expectoration. In this paper, an eco-friendly capillary zone electrophoresis (CZE) fingerprinting method was developed for the separation and detection of 36 batches of CLQTs from nine manufacturers. The fingerprint information index, FI, was calculated for choosing satisfactory test conditions. Quantitative comparison of seven major components showed no significant difference between the samples, illustrating its poor discrimination ability for CLQTs. Furthermore, in combination with chemometrics (principal component analysis and hierarchical clustering analysis), the samples were preliminarily clustered into three groups and exhibited a good qualitative consistency in the same manufacturer. Subsequently, a novel equal weight ratio quantitative fingerprinting method was introduced and proved to be a comprehensive and effective method for further discrimination and holistic quality evaluation of the 36 samples. The samples were divided into five quality grades (grades 1–5) based on the ratio qualitative similarity (S_r), ratio quantitative similarity (P_r) and fingerprint-leveling coefficient (α). The approach proposed in this study will be a valuable counterpart for the holistic quality control of HMs or herbal preparations.