cyclodextrin

Cyclodextrins are a family of cyclic oligosaccharides composed of glucopyranose units linked by α-1,4-glycosidic bonds to form a torus-like molecule. The natural forms include alpha-cyclodextrin with six glucose units, beta-cyclodextrin with seven, and gamma-cyclodextrin with eight. The outer surface of the molecule is hydrophilic due to hydroxyl groups, while the interior cavity is relatively hydrophobic, allowing the formation of inclusion complexes with suitable guest molecules.

The hydrophobic cavity can host a range of nonpolar compounds, and complex formation is typically non-covalent, often with 1:1 stoichiometry. Cyclodextrins are produced enzymatically from starch by cyclodextrin glycosyltransferase (CGTase) enzymes from certain bacteria, such as Bacillus species, yielding mixtures of the natural cyclodextrins that can be purified as needed.

To broaden utility, many derivatives have been developed, including hydroxypropyl-β-cyclodextrin (HP-β-CD), methylated cyclodextrins, and sulfobutyl ether-β-cyclodextrin (SBE-β-CD). These derivatives generally exhibit greater water solubility and can alter binding properties, enhancing suitability for various applications and routes of administration.

Applications of cyclodextrins span pharmaceuticals, food, cosmetics, and industrial formulations. They are used to increase the aqueous solubility and stability of poorly soluble drugs, mask tastes or odors, and stabilize volatile flavors and fragrances. They also aid in controlled release and have roles in environmental and analytical contexts by encapsulating hydrophobic pollutants or analytes.

Safety and regulatory status depend on size and derivative; natural beta-cyclodextrin has limited solubility and potential toxicity at high doses, whereas many derivatives offer improved solubility and favorable safety profiles for specific applications.