Complex of shikonin and β-cyclodextrins by using supercritical carbon dioxide

Abstract

In this work, the complex of shikonin-methyl-β-cyclodextrin and shikonin-2-hydroxypropyl-β-cyclodextrin were studied in supercritical carbon dioxide (sc CO2) at moderate pressure and temperature much lower than the melting point of shikonin. For comparing, the complex was also prepared by sealed heating method. Complex efficiency between shikonin and 2-hydroxypropyl-β-cyclodextrin (HPBCD) was quite low. Partly formation of shikonin—methyl-β-cyclodextrin (MBCD) was obtained by sealed heating method. Complete formation of shikonin—MBCD was obtained in sc CO2 media in short reaction time. This complexation was accelerated and enhanced by the rise in both the reaction temperature and carbon dioxide pressure up to 100 °C 100 bar. The physical state of cyclodextrins in complex reaction has remarkable influence on the complex. The aqueous solubility of shikonin could be enhanced about 75 times by complexing with MBCD. In this work, the complex of shikonin-methyl-β-cyclodextrin and shikonin-2-hydroxypropyl-β-cyclodextrin were studied in supercritical carbon dioxide (sc CO2) at moderate pressure and temperature much lower than the melting point of shikonin (SK). For comparing, the complex was also prepared by sealed heating method. Complex efficiency between SK and 2-hydroxypropyl-β-cyclodextrin (HPBCD) was quite low. Partly formation of SK—methyl-β-cyclodextrin (MBCD) complex was obtained by sealed heating method. Complete formation of SK—MBCD was obtained in sc CO2 media in short reaction time. This complexation was accelerated and enhanced by the rise in both the reaction temperature and carbon dioxide pressure. The physical state of cyclodextrins in sc CO2 has remarkable influence on the complex. The aqueous solubility of SK could be enhanced about 75 times by complexing with MBCD.