A universal method for profiling and characterization of oligosaccharides in traditional Chinese medicines

Oligosaccharides constitute fundamental components in numerous traditional Chinese medicines (TCMs). Conventional chromatographic methods for natural product analysis are not suitable for oligosaccharides due to their large polarity and structural similarity. Herein, an ultra-high performance liquid chromatography with charged aerosol detector (UHPLC-CAD) method was developed for the profiling of oligosaccharides using 9 neutral (DP3-DP11) reference oligosaccharides. Various factors, including columns, mobile phase, elution conditions, flow rate, and column temperature were systematically examined. Optimal separation was achieved using an Amide column with gradient elution within 18 min, at 0.5 mL/min flow rate and 30°C column temperature. Moreover, an ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) method was also optimized to provide structural information. The developed method was applied to detect oligosaccharides in several TCMs, including Morindae Officinalis Radix (MOR), Ziziphi Spinosae Semen (ZSS), Menthae Haplocalycis Herba (MHH) and Chrysanthemi Indici Flos (CIF), revealing 9 and 16 oligosaccharides being uncovered from MHH and CIF respectively for the first time. This study presents a versatile UHPLC-CAD and UHPLC-Q-TOF/MS method with the potential for advancing oligosaccharides discovery and contributing to the quality analysis of TCMs.