Hepatoprotective Saikosaponin Homologs from Comastoma pedunculatum

Abstract

Eight new triterpenoid saponins, the saikosaponin homologs comastomasaponins A-H (1-8), as well as a known triterpenoid (9) and eight known saponins (10-17) were isolated from the aerial portions of Comastoma pedunculatum. The structures of these compounds were elucidated spectroscopically, and their hepatoprotective activity and cytotoxic activity were evaluated against five human tumor cell lines in vitro. Compounds 1, 5-12, 14, 15, and 17 exhibited potent hepatoprotective activity, and compound 11 displayed cytotoxic activity against HCT-8, Bel-7402, BGC-825, A549, and A2780 human tumor cell lines.

Facile Synthesis of Saikosaponins

“…Flash column chromatography was performed on silica gel SiliaFlash P60 (40−63 µm, Silicycle, Quebec, QC, Canada). NMR spectra were measured on a Bruker AM 400 (Switzerland), Agilent 500, or 600 MHz (U.S.) NMR spectrometer at 25 • C. 1 H and 13 C NMR signals were calibrated to the residual proton and carbon resonance of the solvent (CDCl 3 : δH = 7.26 ppm, δC = 77.16 ppm; CD 3 OD: δH = 3.31 ppm, δC = 49.00 ppm; DMSO-d6: δH = 2.50 ppm, δC = 39.52 ppm). High-resolution mass spectra were recorded with Shimadzu Biotech Axima Performance FTMS, maXis 4G FTMS, Thermo Scientific Q Exactive HF Orbitrap-FTMS, or Agilent-TOF/LC-MS 1260-6230 FTMS.…”

“…Monosaccharide 6, named posaikogenin, was found as an artifact which might be derived from disaccharide 5. A number of saikosaponin-like compounds have also been identified from Clinopodium gracile and other plants, among which Clinoposaponin I (7) bearing a trisaccharide residue is a typical one [11][12][13]. All these seven saponins (1-7) belong to type I saikosaponins, which bear the 13,28-epoxy-ether moiety, and this epoxy-ether moiety is found crucial to their cytotoxic activities.…”

“…) 13. C NMR (125 MHz, CDCl 3 ): δ 172.30, 170.92, 170.57, 170.45, 169.99, 169.45, 169.10, 164.64, 135.12, 132.37, 131.02, 127.50, 124.77, 75.18, 72.65, 72.54, 71.97, 71.40, 69.29, 68.63, 68.25, 61.53, 20.87, 20.77, 20.73, 20.72, 20.52, 16.28, 9.18, 9.16.…”

“…) 13. C NMR (125 MHz, CDCl 3 ): δ 170.84, 170.43, 170.41, 169.37, 169.32, 169.16, 163.64, 134.53, 132.58, 131.04, 129.35, 127.23, 125.79, 100.76, 100.45, 92.44, 74.46, 72.60, 71.95, 71.62, 71.19, 70.90, 70.00, 68.25, 61.43, 20.88, 20.76, 20.68, 20.48, 16.20, 9.02.…”

“…) 13. C NMR (125 MHz, CDCl 3 ): δ 170.90, 170.32, 169.32, 168.83, 166.02, 165.43, 164.59, 135.00, 133.62, 133.31, 132.32, 131.06, 130.95, 130.14, 129.83, 129.79, 129.29, 128.68, 128.60, 127.44, 124.76, 100.92, 99.57, 91.39, 75.07, 74.29, 73.08, 72.75, 71.85, 71.22, 69.36, 68.88, 68.15, 61.60, 20.80, 20.69, 20.60, 19.75, 16.66, 9.24, 9.19.…”