Selective extraction of ephedrine from Ephedra sinica using mixtures of CO2, diethylamine, and methanol

The effect of modifiers has been investigated on the SFE efficiencies of ephedrine derivatives (e. g. methylephedrine, norephedrine, ephedrine, and pseudoephedrine) from aerial parts of Ephedra sinica. Among the modifiers employed, methanol containing 10 % (v/v) of diethylamine showed greater enhancement of SFE efficiency for ephedrine derivatives than any other modifiers evaluated in this study. These results might be due to the fact that the salts of Ephedra alkaloids (insoluble in CO2) in plant tissues are changed to their free bases (freely soluble in CO2) by basified modifiers such as diethylamine in methanol. It was supported by measurements of solubilities of these compounds in each supercritical solvent. In addition, CO2 modified with diethylamine in methanol could more readily extract ephedrine than pseudoephedrine, which is the diastereomer of ephedrine.