Cyclodextrins hydrolytic reactions

ABSTRACT. We modified cyclodextrin (CD) by a histamine group to make a model of a-chymotrypsin. Enzymatic turnover reaction was realized with CD-histamine at around neutral pH value. Compared with amino-CD, it is ascertained that this catalytic activity of CD-histamine is caused by an imidazole group. Using several substrates in the hydrolytic reactions, it shows that CD-histamine has a structural selectivity for substrates which are structurally different to each other. 

On the other hand, many excipients can act to chemically stabilize an API in the solid state and in solid dosage forms. The most common class of stabilizing excipients is cyclodextrins (36). Cyclodextrins can envelop the API in their hydrophobic cavities and shield it from common degradation reactions such as hydrolysis, oxidation, or photodegradation. Some excipients or additives may also act as complexing agents that provide hydrolytic (37) and oxidative (38) stabilization. Many excipients, such as cyclodextrins, dyes, and colored additives, are capable of providing extensive photostabilization in the solid state (39-41). 

Cyclodextrins, by virtue of containing a cavity for the binding of substrate molecules in a non-polar cavity surrounded by nucleophilic hydroxyl groups, are often used as models for hydrolytic enzymes such as chymotrypsin. Strictly speaking, the observed reaction is most often transacylation, rather than hydrolysis [2]. 

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