Influence of different solvents on extractable saponins from Rusci rhizoma

Butcher's broom (Rusci rhizoma, Ruscus aculeatus L., Ruscaceae) is traditionally used against chronic venous disorders. Beside phenolic compounds, especially furo- and spirostanol saponins seem to play an important role in the efficacy of the drug. Recent results indicate that furostanol saponins with a C-22 methyl ether are probably artifacts caused by methanol used in the isolation procedure or as component in the mobile phase of an HPLC system. Aim of the present study was to investigate the influence of different extraction solvents on the yield of saponins and artificial C-22 ethers. Powdered Rusci rhizoma was extracted with MeOH, EtOH, 1-Prop, i-Prop and 1-BuOH. The C-22 methyl, ethyl, and 1-propyl ethers could be detected in the respective extracts using HPLC-MS with a H₂O-MeCN gradient. No butyl and i-propyl derivatives could be observed. The amount of saponins in all extracts was examined by ¹H-NMR calculating the ratio of the saponin signal H-6 and the signal of the internal standard phloroglucinol. The lowest saponin concentration was determined in the MeOH extract. The 1-Prop, 1-BuOH, and i-Prop extracts showed higher and similar saponin concentrations compared to the MeOH extract (around 1.5fold), whereas the highest concentration was determined in the EtOH extract (1.72fold). As no C-22 artifacts could be detected and an acceptable yield could be achieved, 1-BuOH or i-Prop are recommended as extraction solvents for saponins from Butcher's broom.