Types And Principles Of Action Of Natural Cyclodextrins

Cyclodextrins have a special molecular hole structure composed of dehydrated glucose units, the inner surface of the molecular hole is hydrophobic, the outer surface of the molecular hole is hydrophilic, and the molecular hole has the function of coating guest molecules. On the basis of the in-depth study on the function and mechanism of cyclodextrin hole-enveloped guest molecules, a new discipline ----- host-guest chemistry has been established and developed. Host-guest chemistry is one of the most active, deepening and expanding fields in the field of chemical research today. On this basis, cyclodextrins and their derivatives have gradually become an important material and technical approach to solve the molecular level microcoating technology in the product development process of various industrial fields. In the past decade, it has been widely used in the field of drug and food development, and recently in Japan, Hungary, France and other countries, cyclodextrin has been gradually applied in personal care products, and has shown good application and development prospects. There are three kinds of natural cyclodextrins: α-β - and γ-cyclodextrin. In comparison, the pores of α-cyclodextrin molecular holes are small, and usually can only cover small guest molecules, such as aliphatic hydrocarbons,CO2, propane and other gas molecules. Gamma-cyclodextrin has a large molecular hole and can cover large molecular guest molecules, such as organic macrocyclic compounds, but in general, gamma-cyclodextrin has a high production cost and cannot be mass-produced in industry, and its application is limited to a certain extent. The molecular hole size of β-cyclodextrin is moderate, which can be better coated with some vitamins and small aromatic molecules, etc., and its wide range of inclusion and low production cost are the only cyclodextrin products that can be mass-produced in industry at present, but the solubility of β-cyclodextrin in water limits its application range, for example, under 25℃ conditions. The solubility of β-cyclodextrin in 100ml water is 1. 85g, α-cyclodextrin is 14.5g, γ-cyclodextrin is 23.2g, in order to overcome this defect, in recent years, a lot of work on the improvement of β-cyclodextrin has been carried out at home and abroad, and breakthrough progress has been made.
Due to the special structure and properties of cyclodextrin molecules, cyclodextrin molecules can completely or partially cover some lipophilic guest molecules in molecular holes through the van der Waals force interaction between cyclodextrin molecules and guest molecules, the Yun bond association between cyclodextrin molecules hydroxyl and guest molecules, and the affinity between oilphilic and oilphilic molecules, thus forming cyclodextrin-guest coatings. The process of cyclodextrin coating guest molecules to form cyclodextrin-guest coating is an equilibrium process, and the free cyclodextrin and the free guest molecules and the cyclodextrin-guest coating are in a thermodynamic and kinetic equilibrium process. All coated objects are in different equilibrium conditions because they are in different physical states (solid, dissolved or volatile). It also affects the distribution coefficients involved in the coating process. All the coating actions and processes of cyclodextrins can be understood from these equilibria.
Due to the special structure and properties of cyclodextrin molecules, cyclodextrin molecules can completely or partially cover some lipophilic guest molecules in molecular holes through the van der Waals force interaction between cyclodextrin molecules and guest molecules, the hydrogen bond association between cyclodextrin molecules and the affinity between oilphilic molecules and oilphilic molecules, so as to form cyclodextrin-guest coatings. The process of cyclodextrin coating guest molecules to form cyclodextrin-guest coating is an equilibrium process, and the free cyclodextrin and the free guest molecules and the cyclodextrin-guest coating are in a thermodynamic and kinetic equilibrium process. All coated objects are in different equilibrium conditions because they are in different physical states (solid, dissolved or volatile). It also affects the distribution coefficients involved in the coating process. All cyclodextrin coating actions and processes can be understood from these equilibria.