Cyclodextrins (CDs) are cyclic oligosaccharides composed of D‐(+)‐glucopyranose units linked through α‐1,4‐glycoside bonding. CDs have a narrower rim possessing primary hydroxy groups and a wider rim possessing secondary hydroxy groups. The most popular CDs are α‐cyclodextrin (αCD), β‐cyclodextrin (βCD), and γ‐cyclodextrin (γCD), which are composed of six, seven, and eight D‐(+)‐glucopyranose units, respectively. The molecular dimensions of these CDs are summarized in Table 5.1 . CDs are soluble in water, but they possess a rather hydrophobic cavity. On the basis of the unique hydrophile–lipophile balance, CDs recognize hydrophobic guest compounds, of which the shape and size match their cavities, to form inclusion complexes in water [2–6]. Thus CDs have been attracting considerable interest from researchers as simple biomimetic compounds for decades. CDs have been of increasing importance along with increasing interest in environmentally benign systems not only because CDs are produced enzymatically from starch and are nontoxic but also because CDs are usually used preferentially in aqueous media.
Table 5.1 Molecular dimensions of cyclodextrins.
Source: Ref. . Reproduced with permission of American Chemical Society.
|Cyclodextrin||Number of D‐(+)‐glucopyranose units ...|