gammaCD

GammaCD, or gamma-cyclodextrin, is a cyclic oligosaccharide composed of eight D-glucose units linked by α-1,4 glycosidic bonds. It forms a truncated cone with a hydrophobic interior and a hydrophilic exterior, enabling it to form inclusion complexes with hydrophobic guest molecules. It is one of the natural cyclodextrins, alongside alpha- and beta-CD, differing mainly in ring size and cavity dimensions.

gammaCD is produced industrially by enzymatic conversion of starch using cyclodextrin glucanotransferase (CGTase) enzymes, typically derived from Bacillus species. The process yields a mixture of cyclodextrins, from which gammaCD is isolated by crystallization or selective complexation. Derivatives such as hydroxypropyl-γ-cyclodextrin are used to improve solubility and modify binding behavior.

gammaCD forms non-covalent inclusion complexes with a wide range of hydrophobic substances, enhancing solubility, chemical and thermal stability, and taste masking. Its relatively large cavity allows binding of moderately large guests that are less efficiently complexed by alpha- or beta-CD; complexation is governed by guest size, polarity, and preferred geometry.

Applications span pharmaceuticals, where gammaCD acts as an excipient to improve solubility and bioavailability; cosmetics, where it stabilizes fragrances and pigments; and food and beverage industries, where it stabilizes flavors or essential oils and can reduce off-flavors. In research, gammaCD is used to study host–guest chemistry and to modulate drug pharmacokinetics.

Safety and regulation vary by jurisdiction; gammaCD is generally regarded as safe in many uses as an excipient, but high doses can cause gastrointestinal discomfort. It is not digested by human enzymes and is excreted largely unchanged in urine.