Quantitative Comparison of Multiple Components in Dioscorea nipponica and D. panthaica by Ultra-High Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Mass Spectrometry

Introduction: Dioscorea nipponica (DN) and D. panthaica (DP) have been uniquely prepared as herbal medicinal products for treating coronary heart disease (CHD) in China. However, so far there has been little discussion and no work comparing the qualitative and quantitative differences between the two herbs nor assessing whether they have similarities in chemical composition that would support their common application for treating CHD. 

Objective: To develop an efficient and reliable method based on UPLC-qTOF-MS for quantitative comparison of saponins in both DN and DP. 

Methods: Using electrospray ionisation and atmospheric-pressure chemical ionisation respectively, six steroidal glycosides and one aglycone were determined in 13 DN samples and 13 DP samples. The comparative analysis of chemical components in DN and DP was carried out by chromatographic fingerprint similarity evaluation, test of significance (t-test) and principle component analysis (PCA). 

Results: The UPLC-qTOF-MS method showed limit of detection and quantitation within the range 0.02-0.2 ng and 0.08-0.5 ng, respectively, for the seven saponins studied. The intra- and interday precision (RSD) were below 5%. The recoveries for the quantified compounds were within the range of 72.79-118.31%. 

Conclusion: This UPLC-qTOF-MS assay provides a suitable method for the identification and determination of major bioactive constituents both in DN and DP. The chemical composition of all DN and DP samples studied exhibited a high level of global similarity. This chemical similarity validates their common application in the pharmaceutical industry as anti-CHD herbal drugs.