Studies on isolation and structural identification of saponins from the herb Hylomecon japonica and their bioactivities

Abstract

Three undescribed oleanane type triterpenoid saponins (1-3), along with one known saponin (4) were isolated from the whole herb of Hylomecon japonica. Their structures were elucidated by analysis of 1D and 2D-NMR (¹H-¹H COSY, HSQC, and HMBC) spectroscopic data, mass spectrometry (HR-ESI-MS) and chromatographic date (GC and LC) as 3-O-β-d-glucopyranosyl-(1 → 2)-β-d-glucuronopyranosyl gypsogenin 28-O-β-d-galactopyranosyl-(1 → 3)-[β-d-xylopyranosyl-(1 → 4)]-α-l-rhamnopyranosyl-(1 → 2)-β-l-arabinopyranosyl ester (1), 3-O-β-d-galactopyranosyl-(1 → 2)-β-d-glucuronopyranosyl gypsogenin 28-O-α-l-arabinopyranosyl-(1 → 3)-[β-d-xylopyranosyl-(1 → 4)]-α-l-rhamnopyranosyl-(1 → 2)-β-l-arabinopyranosyl ester (2), 3-O-β-d-galactopyranosyl-(1 → 2)-β-d-glucuronopyranosyl gypsogenin 28-O-β-d-galactopyranosyl-(1 → 3)-[β-d-xylopyranosyl-(1 → 4)]-α-l-rhamnopyranosyl-(1 → 2)-β-d-galactopyranosyl ester (3), 3-O-β-d-galactopyranosyl-(1 → 2)-[α-l-arabinopyranosyl-(1 → 3)]-β-d-glucuronopyranosyl gypsogenin 28-O-β-d-glucopyranosyl-(1 → 3)-[β-d-xylopyranosyl-(1 → 4)]-α-l-rhamnopyranosyl-(1 → 2)-β-d-fucopyranosyl ester (4). All saponins possess a partial sequence β-d-galactopyranosyl-(1 → 2)-β-d-glucuronopyranosyl at C-3 of the aglycon. Compound 1 has cytotoxic activity against human colon cancer cell lines HT29, 3 against human gastric cancer cell lines AGS, and 4 against human lung cancer cell lines A549, AGS and HT29. Among them, compounds 3 and 4 showed significant inhibitory effect against AGS with IC₅₀ value of 6.01 ± 1.4 μM, 3.66 ± 1.8 μM, respectively. These results represent a contribution to the chemotaxonomy of the saponins of Hylomecon japonica and their bioactivities.

Keywords: Cytotoxic activities; Gypsogenin; Hylomecon japonica; Papaveraceae; Quillaic acid; Triterpenoid saponins.