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 CO
2) in plant tissues are changed to their free bases (freely soluble in CO
2) by basified modifiers such as diethylamine in methanol. It was supported by measurements of solubilities of these compounds
in each supercritical solvent. In addition, CO
2 modified with diethylamine in methanol could more readily extract ephedrine than pseudoephedrine, which is the diastereomer
of ephedrine.
Key Words Supercritical fluid extraction - Basified modifier - Ephedrine derivatives -
Ephedra sinica