An effective strategy for distinguishing the processing degree of Polygonum multiflorum based on the analysis of substance and taste by LC-MS, ICP-OES and electronic tongue

The efficacy of raw and processed products of Polygonum multiflorum (PM) varies greatly. "Nine cycles of steaming and sunning" (NCSS) is recognized as an effective technology in enhancing efficacy and reducing toxicity for PM. In this paper, PM was prepared differently into three groups (including group R, M, and "9"), which represent raw PM, PM processed using the method of Chinese Pharmacopoeia (ChP) and PM processed using traditional NCSS, respectively. The purpose is to establish an effective method to distinguish raw PM from different processed products and highlight the rationality of processing technology. The main organic compounds that could distinguish these three groups of samples were identified by in-depth mining of mass spectral information and various chemometric methods. Level of related metal cations have been quantified and used as another important distinguishing markers. The electronic tongue was utilized to determine the taste traits of aqueous extract from PM. Furthermore, the material basis that caused the difference in taste was discovered according to correlation analysis. In detail, saltiness has the most important contribution associated with the concentrations of K+ and Na+, however, bitterness and astringency were mainly associated with the contents of epicatechin gallate, catechin, procyanidin B1, procyanidin B2 and epicatechin. This study proposed a novel and effective strategy for identification of processing technology of PM. It lays the foundation for clarifying the modern scientific recommendations of processing technology to PM. On the other hand, it also provides a reference for related researches on other traditional Chinese medicine (TCM).