HPLC-HRMS/MS analysis of saponins and phytoecdysteroids from a Silene colorata hydroglycerinic extract

The genus Silene (family of Caryophyllaceae) is known to contain triterpenoid saponins [1] and phytoecdysteroids [2]. Silene colorata is distributed over the Mediterranean basin, but little is known concerning the phytochemistry of the species. The aim of this work was the development of an analytical method for the rapid characterization of saponins and phytoecdysteroids in a commercially available S. colorata hydroglycerinic extract. After sample preparation on Solid Phase Extraction cartridges, the extract was analyzed by HPLC-HR-MS/MS on an LTQ-Orbitrap platform. The chromatographic and spectrometric conditions applied for the analysis were optimized for the two compound classes. The analysis revealed the presence of three major groups of phytochemicals in the extract, namely di- and tri-glycosylated flavonoids, phytoecdysteroids, and saponins. Among phytoecdysteroids, 20-hydroxyecdysone and a sileneoside derivative (Figure) were the major constituents, while five more major compounds that belong to this category were identified. Saponins detected were molecules of high molecular weights (> 950 and up to 1630) and MS/MS experiments revealed the presence of three to six sugar units on the molecules. In some cases, the glycosidic moiety was esterified with a cinnamic acid derivative, e.g. saponin in the Figure. These structural features of the saponin corresponded with those for saponins in other Silene species [3]. The aglycons of the saponins were characterized with the aid of MS³ experiments. In all cases the triterpenic aglycon gave a pseudomolecular ion of m/z 485.3405, corresponding to a molecular formula of C₃₀H₄₇O₅, with 7.5 RDBeq. The molecular formula corresponded to that of quillaic or gypsogenic acids, that have been both reported as characteristic triterpenoidal aglycones in other species [1].

Keywords: Silene colorata, saponins, phytoecdysteroids, analysis, HRMS/MS, LTQ-Orbitrap

References:

[1] Bottger S, Melzig MF. Triterpenoid saponins of the Caryophyllaceae and Illecebraceac family. Phytochem Lett 2011; 4: 59 – 68

[2] Mamadalieva NZ. Phytoecdysteroids from Silene plants: distribution, diversity and biological (antitumour, antibacterial and antioxidant) activities. Boletin Latinoamericano y del Caribe de Plantas Medicinales y Aromaticas. 2012; 11: 474 – 497

[3] Lacaille-Dubois MA, Hanquet B, Cui ZH, Lou ZC, Wagner H. Acylated triterpene saponins from Silene jenisseensis. Phytochem 1995; 40: 509 – 514