A new strategy for quality evaluation and control of Chinese patent medicine based on chiral isomer ratio analysis: With Yuanhuzhitong tablet as an example

Chiral compounds commonly exist in traditional Chinese medicine (TCM), but little research on the quality control of TCM has been conducted. In this study, a new strategy is proposed, taking Yuanhuzhitong tablet [YHZT, consisting of Radix Angelicae Dahuricae and Rhizoma Corydalis (Yan Hu Suo, YHS)] for example, which is based on chiral isomer ratio analysis to monitor the production process of Chinese patent medicine companies. In the process of content determination for tetrahydropalmatine (THP) in YHZT from different companies, noticeable differences were observed in their chromatographic behaviors. It is known that THP has two enantiomers, naturally coexisting in YHS as a racemic mixture, so we prepared THP twice and subsequently performed chiral separation analysis using supercritical fluid chromatography. As a result, the peak area ratios of two enantiomers from different companies varied remarkably, demonstrating that some companies did not probably manufacture YHZT products in accordance with the prescription proportion, used inferior or extracted YSH crude materials in the production process, and added raw chemical medicine in the production to reach the standard and lower the costs. In conclusion, the peak area ratio of chiral isomers could be taken as a key quality index.