Complete (1)H-NMR and (13)C-NMR spectral assignment of five malonyl ginsenosides from the fresh flower buds of Panax ginseng

BACKGROUND: Ginsenosides are the major effective ingredients responsible for the pharmacological effects of ginseng. Malonyl ginsenosides are natural ginsenosides that contain a malonyl group attached to a glucose unit of the corresponding neutral ginsenosides. METHODS: Medium-pressure liquid chromatography and semipreparative high-performance liquid chromatography were used to isolate purified compounds and their structures determined by extensive one-dimensional- and two-dimensional nuclear magnetic resonance (NMR) experiments. RESULTS: A new saponin, namely malonyl-ginsenoside Re, was isolated from the fresh flower buds of Panax ginseng, along with malonyl-ginsenosides Rb1, Rb2, Rc, Rd. Some assignments for previously published (1)H- and (13)C-NMR spectra were found to be inaccurate. CONCLUSION: This study reports the complete NMR assignment of malonyl-ginsenoside Re, Rb(1), Rb(2), Rc, and Rd for the first time.