Inclusion Effect and Structural Basis of Cyclodextrins for Increased Extraction of Medicinal Alkaloids from Natural Medicines

The enhancing effects of α-, β-, and γ-cyclodextrins (CyDs) on the aqueous extraction of ephedrine and berberine from the natural medicines were investigated in HPLC analysis, and the greatest effect was observed for β- and γ-CyDs. To clarify the structural basis of such an increased extraction effect with β-CyD, possible interaction modes of (1R,2S)-ephedrine with α-, β-, and γ-CyDs were investigated using molecular dynamic simulations in an aqueous solution system. It was shown that the wrapping model of ephedrine by β-CyD is the most compact and thus increases the solubility most effectively, compared with those by other CyDs. The same mode could be possible for the greatest effect of γ-CyD on the extraction of berberine from natural medicines. This clearly shows that CyDs are useful additives for the effective extraction of bioactive alkaloids from natural medicines.