Synthesis and Biological Evaluation of Raddeanin A, a Triterpene Saponin Isolated from Anemone raddeana

First, Raddeanin A, a cytotoxic oleanane-type triterpenoid saponin isolated from Anemone raddeana REGEL, was synthesized. Stepwise glycosylation was adopted in the synthesis from oleanolic acid, employing arabinosyl, glucosyl and rhamnosyl trichloroacetimidate as donors. The chemical structure of Raddeanin A was confirmed by means of H-1-NMR, C-13-NMR, IR, MS and elemental analysis, which elucidated the structure to be 3-O-alpha-L-rhamnopyranosyl-(1 -> 2)-beta-D-glucopyranosyl-(1 -> 2)-alpha-L-arabinopyranoside oleanolic acid. Biological activity tests showed that in the range of low concentrations, Raddeanin A displayed moderate inhibitory activity against histone deacetylases (HDACs), indicating that the HDACs' inhibitory activity of Raddeanin A may contribute to its cytotoxicity.