Re-evaluation of physicochemical and NMR data of triol ginsenosides Re, Rf, Rg2, and 20-gluco-Rf from Panax ginseng roots

Abstract

Ginseng roots were extracted with aqueous methanol, and extracts were suspended in water and extracted successively with ethyl acetate and n-butanol. Column chromatography using the n-butanol fraction yielded four purified triol ginseng saponins: the ginsenosides Re, Rf, Rg2, and 20-gluco-Rf. The physicochemical, spectroscopic, and chromatographic characteristics of the ginsenosides were measured and compared with reports from the literature. For spectroscopic analysis, two-dimensional nuclear magnetic resonance (NMR) methods such as 1H-1H correlation spectroscopy, nuclear Overhauser effect spectroscopy, heteronuclear single quantum correlation, and heteronuclear multiple bond connectivity were employed to identify exact peak assignments. Some peak assignments for previously published 1H- and 13C-NMR spectra were found to be inaccurate. This study reports the complete NMR assignment of 20-gluco-Rf for the first time.