Synthesis of branched cyclodextrins using activated carbon as a catalyst

Abstract

Activated carbon has been reported to act as a catalyst for condensation reactions between glucose molecules. The present study describes the use of activated carbon as a new catalyst for the synthesis of branched cyclodextrins (CDs). Two main methods have been used to synthesize branched CDs: a method using an enzymatic condensation or transfer reaction, and a method using a chemical reaction. However, these methods have problems such as a limited number of the types of branched CDs that can be synthesized that depend on the characteristics of the enzyme, the long reaction time required (several days or more), difficulty in synthesizing branched CD with a high degree of substitution (DS), the need for large quantities of environmentally harmful solvents, and a complicated and costly reaction. Using activated carbon as a catalyst, branched CDs with a high DS could be synthesized within a relatively short time (a few hours), regardless of the type of saccharide in the branched portion. Furthermore, since the reaction was conducted under solvent-free conditions using activated carbon, the amount of solvent used in the production of branched CD could be reduced. The branched β-CDs prepared using the activated carbon catalyst showed high solubility, high solubilization capacity, and low hemolytic activity, similar to the 2-hydroxypropyl-β-CD used for pharmaceuticals. These results indicate that activated carbon is an industrially and environmentally useful catalyst for branched CD syntheses.