Description

1.1 Introduction

Cyclodextrins (CDs) are cyclic oligosaccharides that contain at least six d–(+)–glucopyranose units linked by α–(1, 4) glucosidic bonds. The three natural CDs, α-, β-, and γ-CDs, have 6, 7, and 8 glucose units, respectively, and differ from each other in their size and solubility(Crini, 2014).CDs with less than six glucose units cannot form due to steric hindrance, and CDs with nine or more glucose units are difficult to purify(Bibekarvet al., 2024).

In 1891, Antoine Villiers discovered crystalline dextrins and was the first to isolate the oligosaccharides produced by starch or its derivatives using the cyclodextrin (CD) glycosyl transferase enzyme. The structure of CDs was described 30 years later by Freudenberg and his co-workers, and they were produced in pure form in 1984. Since then, numerous scientific publications and patents have been developed focusing on their diverse applications in the pharmaceutical and food industries, products, and technologies The most common natural CDs used in industrial-scale production are alpha-cyclodextrin (α–CD), beta cyclodextrin (β–CD), and gamma-cyclodextrin (γ–CD)(Jansook et al., 2024).

Cyclodextrins belong to the family of cage-type molecules. They have a non-symmetrical toroidal structure, wider at one end and narrower at the other in a truncated cone shape. They have a hydrophilic exterior, hydroxyl groups at both ends, and a hydrophobic inner cavity (Morin-Crini et al., 2021).