Characterisation of the Degradation of Salvianolic Acid B Using an On‐line Spectroscopic Analysis System and Multivariate Curve Resolution

Abstract

Chinese herbal medicines contain complex ingredients that are unstable during the manufacturing process. Current off-line methods are usually time-consuming and inaccurate. The aim of this study was to develop a continuous-flow-based on-line spectroscopic system for monitoring the degradation of unstable compounds in Chinese herbal medicines. An on-line spectroscopic analysis system in the evaluation of the degradation of unstable compounds was implemented, using salvianolic acid B from Danshen (Radix Salviae Miltiorrhizae) as a model compound. Resolution of the mixture spectra obtained during the reaction was performed with multivariate curve resolution (MCR), and the pure spectra and kinetic profiles of reactant species were reconstructed. The degradation process of salvianolic acid B is probably a consecutive two-step reaction of the form A → B → C, where A is salvianolic acid B, and B and C are the intermediate and final products, respectively. The intermediate and final products were suggested to be a mixture of lithospermic acid and danshensu [3-(3, 4-dihydroxyphenyl) lactic acid], and a mixture of danshensu and salvianolic acid A, respectively. The findings suggested that the combined use of on-line spectroscopic analysis and MCR might be a cheap, readily available, sensitive tool to monitor the transformation of unstable components of Chinese herbal medicines.