Double Off-line Two-dimensional Liquid Chromatography for Separation and Identification of Compounds in Salvia Miltiorrhiza (Danshen)

Abstract

Background: Danshen is an important traditional Chinese medicine (TCM) used for the treatment of cardiovascular and cerebrovascular diseases. Separation and analysis of its components have been widely investigated. However, the systematical two dimensional liquid chromatography (2D-LC) methods have not been developed to comprehensively separate and characterize its components. Objective: In this work, double off-line 2D-LC methods were aimed to develop for the systematical separation of compounds from Danshen. Methods: Using solid phase extraction (SPE), the Danshen extract was divided into a medium-polar fraction (Sample I) and a weak-polar fraction (Sample II) according to their polarities. Based on reversed-phase liquid chromatography (RPLC) and hydrophilic interaction liquid chromatography (HILIC) modes, a 2D-HILIC × RPLC system and a 2D-RPLC × RPLC system were designed for the separation of Sample I and Sample II, respectively. According to reversed-phase and HILIC columns selectivities characterized in our previous reports, ZIC-HILIC and XTerra C18 were employed to build the 2D-HILIC × RPLC system and Click TE-CD and XTerra C18 for the 2D-RPLC × RPLC system, respectively. Results: The 2D-HILIC × RPLC and 2D-RPLC × RPLC systems exhibited excellent orthogonality for the separation of Sample I and Sample II, respectively. Their orthogonalities were 88.42% and 63.24%. Based on these double 2D-LC systems combined with mass spectrometry, at least 200 compounds were found and 33 compounds of them were identified, including 16 phenolic acids and 17 diterpenoid quinines. Conclusion: These results suggest that these two off-line 2D-LC methods are effective for the separation and characterization of components in Danshen.