β-Cyclodextrin sometimes abbreviated as β-CD, is a heptasaccharide derived from glucose. The α- (alpha), β- (beta), and γ- (gamma) cyclodextrins correspond to six, seven, and eight glucose units, respectively. β-Cyclodextrin is the most used natural cyclodextrin in marketed medicines. The reason for this lies in the ease of its production and subsequent low price (more than 10,000 tons produced annually with an average bulk price of approximately 5 USD per kg).
In β-cyclodextrin, the seven glucose subunits are linked end to end via α-1,4 linkages. The result has the shape of a tapered cylinder, with seven primary alcohols on one face and fourteen secondary alcohol groups on the other. The exterior surface of cyclodextrins is somewhat hydrophilic whereas the interior core is hydrophobic.
β-Cyclodextrin exists as a white (colorless) powder or crystals. The density of its saturated hydrate crystal (βCD·12H2O) is 1.46 g/cm3. β-Cyclodextrin is moderately soluble in water and glycerin; well soluble in dimethyl sulfoxide, dimethylformamide, pyridine, HFIP, and ethylene glycol; and insoluble in ethanol and acetone.
β-Cyclodextrin is widely used in medicine, pharmacy, food industry, textiles. Its molecules can accommodate various biomolecules and hence are also used as a complexing agent. Hydrophobic forms of β- CD have been used as sustained release drug carriers. In addition to improving the solubility of compounds, complexation with cyclodextrin has been used to improve the stability of many drugs by inclusion of the compound and protecting certain functional groups from degradation.[1]
β-cyclodextrin has relatively low solubility in water, and hence industry uses its derivatives, such as 2-hydroxypropyl-β-cyclodextrin (HPbCD), randomly methylated β-cyclodextrin (RAMEB), and β-cyclodextrin sulfobutyl ether sodium salt (SBEbCD).