Identification and differentiation of aldose enantiomers in trace natural glycosides by ultra-performance liquid chromatography with diode array detector coupled to quadrupole/time-of-flight mass spectrometry combined with one-pot derivatized protocol

Trace natural products usually possess great biological activity, but the identification of the absolute configuration of monosaccharides in trace natural glycosides is still a challenge. The methods available are not suitable to distinguish enantiomers of monosaccharides in trace natural products when the amount of natural products is less than 1.0 mg. Therefore, this study explored an ultra-performance liquid chromatography with diode array detector coupled to quadrupole/time-of-flight mass spectrometry (UPLC-DAD-Q-TOF/MS) combined with modified one-pot monosaccharide derivatized protocol to distinguish enantiomers of monosaccharides in trace natural products. The experimental parameters were optimized to achieve multiple objectives, and detailed approaches were proposed to improve the sensitivity and resolution of the protonated ion and adduct ion of the monosaccharide derivatives. The retention time of the extracted ion chromatogram and the relative abundance ratio of the characteristic fragment ions were considered for the characterization of the absolute configuration of monosaccharides to distinguish the enantiomers of the monosaccharides of natural products. This strategy was successfully applied to distinguishing 8 pairs of aldose enantiomers, and was verified using trace D-lactose and trace narirutin, which are reference substances commercially available. Moreover, the absolute configuration of the monosaccharide of one trace new compound isolated from the seeds of Moringa oleifera Lam. was successfully identified using this procedure.