Isolation of Three Triterpene Saponins, Including Two New Oleanane Derivatives, from Soldanella alpina and Hydrophilic Interaction Liquid Chromatography-Evaporative Light Scattering Detection of these Three Saponins in Four Soldenella Species.

Abstract

The genus Soldanella is one of the few endemic to Europe. Some of its species have relevance in local traditional medicine. Earlier work has indicated the possible presence of saponins in S. alpina. To investigate S. alpina and other related species for the occurrence of saponins. Following sequential extraction with n-hexane, dichloromethane and ethyl acetate the subsequent methanolic extract of S. alpina roots was fractionated after solvent precipitation using fast centrifugal partition chromatography and column chromatography. Structures were elucidated by LC-MSn , high-resolution MS, hydrolysis experiments and one-dimensional (1D)- and two-dimensional (2D)-NMR. A hydrophilic interaction liquid chromatography method was developed to quantitate saponins in the leaves and roots of four Soldanella species. Three triterpene saponins, two of them new natural products, were isolated from S. alpina. Based on an epoxyoleanal aglycone substituted with four sugar units, they were analytically quantitated using a Kinetex 2.6 μm hydrophilic interaction liquid chromatography (HILIC) column together with a mobile phase comprising of ammonium acetate, water and acetonitrile. Method validation confirmed that the assay meets all requirements in respect to linearity, accuracy, sensitivity and precision. All four Soldanella species investigated contained the three saponins. The lowest total level of the three saponins (1.09%) was observed in S. montana leaves while the highest saponin content (5.14%) was determined in S. alpina roots. The detection of saponins within the genus Soldanella is an indication that further phytochemical examination of this genus may reveal more secondary metabolites of interest. Copyright © 2017 John Wiley & Sons, Ltd.