Discovery of prenylated dihydrostilbenes in Glycyrrhiza uralensis leaves by UHPLC-MS using neutral loss scan

This study was conducted to establish a liquid chromatography-mass spectrometry method for mining undiscovered prenylated dihydrostilbenes from the leaves of Glycyrrhiza uralensis. The results of this study showed that dihydrostilbenes are easily fragmented between the alpha-alpha' bonds. In negative ionization mode, fragments with more phenolic groups (except for ortho-phenols) displayed more intense ion peaks, while in positive ionization mode, fragments with less phenolic groups displayed more intense ion peaks. A neutral loss of 56 Daltons was found to be characteristic of prenylated dihydrostilbenes in positive ionization mode. The chromatogram profile of prenylated compounds from G. uralensis leaves was obtained using a neutral loss scan. Through product scans, the structures of the major peaks of dihydrostilbenes were deduced based on their fragment ions. Two of the compounds were deduced to be newly described and their structures were confirmed by NMR spectra analysis of pure compounds obtained by chromatography methods. The prenylated dihydrostilbenes found in high levels in G. uralensis leaves mediated a remarkable degree of a-glucosidase inhibition. These results indicate that G. uralensis leaves are a rich source of bioactive prenylated dihydrostilbenes, and that a combination of neutral loss with product scans of liquid chromatography-mass spectrometry is a feasible method to mining new prenylated dihydrostilbenes from plant extracts.