Effects of Cyclodextrins on Degradations of Emetine and Cephaeline in Aqueous Solution

Abstract

The stabilizing effects of β-, γ- and 2, 6-dimethyl-β-cyclodextrins (β-, γ- and DM-β-CyDs) against photodegradation and thermal degradation of emetine (EM) and cephaeline (CP) in aqueous solution were examined. The degradation rates of EM and CP increased with decreasing pH below about 3 and with increasing pH above about 5, showing V-shaped pH-profiles, and the photodegradation of EM and CP was significantly faster than the thermal degradation. The photostability of EM and CP was improved by the complexation with γ- and DM-β-CyDs, while it was reduced slightly by β-CyD. The emetic syrup was prepared with γ-CyD or DM-β-CyD in pH 4 phosphate buffer colution, and its photostability was investigated. The results suggested that γ- and DM-β-CyD complexations are useful for the stabilization of EM and CP in the syrup preparation.