The structure and main properties of cyclodextrins

The structure and main properties of cyclodextrins

1. The definition of cyclodextrin:

Cyclodextrins are a type of cyclic oligosaccharides produced by the action of cyclodextrin glucosyltransferase (CGTase) on starch, which are interconnected by 1,4 glycosidic bonds. Common cyclodextrins mainly include alpha cyclodextrin (α-CD), beta cyclodextrin (β-CD), and gamma cyclodextrin (γ-CD), collectively known as natural cyclodextrins.

2.The structure of cyclodextrin:

Cyclodextrin has a unique hollow molecular structure, which can absorb guest substance molecules into its molecular cavity to form molecular inclusion complexes. It is hydrophilic on the outside and hydrophobic on the inside. The hydroxyl -OH constitutes the hydrophilic surface of cyclodextrin, and the carbon chain skeleton constitutes the hydrophobic inner cavity of cyclodextrin.

3.Main properties of cyclodextrin:

A: The properties of cyclodextrin cavities - Inclusion interaction: Forming inclusion complexes (referred to as inclusion complexes) with guest molecules is one of the most important properties of cyclodextrin. Inclusion refers to the phenomenon where the subject and the object, through the interaction and mutual recognition among molecules, partially or completely embed the molecules of the object into the interior of the subject.

B:Tolerance of cyclodextrin to heat, acid, alkali and enzymes:

It is thermally stable, has no fixed melting point, and begins to decompose when heated to approximately 200 ℃. It can be stored for a long time at room temperature

Cyclodextrin is stable to alkali and dissociates from O-H at high pH (2-OH,pKa=12.2).

Cyclodextrin has poor stability to acids. It can undergo hydrolysis in strong acids, and the hydrolysis rate is significantly slower than that of starch. But it is relatively stable in dilute acid at room temperature

Cyclodextrin is not hydrolyzed by β -amylase, but can be slowly hydrolyzed by α -amylase. Generally, the larger the ring of cyclodextrin, the faster the hydrolysis rate.