Extraction, isolation and cytotoxic activities of triterpene saponins from ornamental and medicinal plant Lysimachia christinae

The extraction technology of total triterpenoid saponins from ornamental and medicinal plant Lysimachia christinae was optimized by ultrasonic-assisted extraction (UAE) method. The triterpenoid saponins compounds in the extraction were isolated and separated by repeated column chromatography, the structure of the isolated compounds was elucidated on the base of spectroscopic analysis (NMR, HR-ESI-MS, IR) and chemical methods, and the cytotoxicity of the isolated compounds against cancer cells were also evaluated. The results revealed that the optimal extraction conditions for triterpenoid saponins from L. christinae were optimized as liquid-to-solid ratio of 32 mL/g, extraction time of 40 min, extraction temperature of 50 °C, and ethanol concentration of 66 %, with the extraction yield of 17.32 %. Four undescribed oleanane-type triterpenoid saponins (1–4), named Lysichriside C-F, along with four known oleanane-type triterpenoid saponins (5–8) were isolated from the extraction of L. christinae. Compounds 1–3 and 6–7 had the structure type of 13β, 28-epoxy (type I), and compounds 4 and 8 had the structure type of Δ¹² −17-CH₂OH (type II). All the isolated compounds had high toxicity against cancer cell lines in vitro, compounds 3, 5 and 6 revealed significant inhibition against the cancer cell lines tested than other compounds, and with the IC₅₀ values of 2.9–12.3, 1.9–15.7 and 1.8–12.6 μM, respectively. The studies revealed that oleanane-derived sapogenols with the structure of 13β, 28-epoxy and Δ ¹² –17-CH₂OH were the main two structural types of L. christinae, and the triterpenoid saponins in L. christinae had important research and development value.