Cyklodekstryny

Cyclodextrins are carbohydrates from the dextrins group. The most prevalent α-, β- and γ-cyclodextrin consist of 6.7 or 8 glucose units, respectively, linked by α-1,4-acetal bonds, which together form a cyclic structure.

Also known as larger cyclodextrins, up to 39 units of glucose.

Cyclodextrins are produced relatively easily from ordinary starch as a result of its controlled enzymatic hydrolysis using cyclogluconase (CGTase). Cyclodestrins are readily soluble in water and form a toroidal solution. Because all the glucopyranose units in the cyclodextrin ring are present in the chair conformation, all primary hydroxyl groups are on one side of the ring, and secondary on the other side of the ring. The particle takes the shape of a truncated cone (toroid), whose broader edge defines secondary OH groups and narrower primary OH groups. The free electron pairs are directed towards the interior of the molecule and, therefore, the interior of the toroid has hydrophobic (water-repellent) properties. The compounds as a whole are hydrophilic (water-repellent) and water soluble.

Thanks to the hydrophobicity of the interior, cyclodextrins are capable of forming inclusion complexes with hydrophobic compounds. These are host-type complexes, where the cyclodextrin acts as a host and the complex hydrophobic compound is a guest. However, the whole complex is still soluble in polar solvents such as water. This is widely used in pharmacy. β-cyclodextrin complexes with nitroglycerin or hydrocortisone. The use of the drug in the form of a complex with cyclodextrin increases its bioavailability and hence the possibility of reducing the dose. In addition, the drug is gradually released from the complex which lengthens its duration. This allows you to take medicine eg once daily instead of three or four daily doses.

In cosmetic and hygiene products cyclodextrins are used to absorb or gradually release odors (air fresheners, perfumes, fragrance toilet paper). The food industry is used to absorb unpleasant odors and tastes, as well as to preserve the desired color, taste and odor (eg in soluble coffee). Breakdown of cyclodextrins may occur due to changes in the pH of the solution or due to the thermal decomposition of α-1,4-acetal bonds. The thermal decomposition of cyclodextrins is Used to produce systems capable of slow release of fragrances. For this purpose, the dried cyclodextrins are treated with perfume vapors and then added to, for example, washing powders. During ironing, or while carrying fabrics washed in these powders, thermal cyclodextrin decomposes and releases fragrances to the environment.

Cyclodextrins also apply in a variety of chemistry fields. Their ability to form inclusion complexes is successfully used in analytical chemistry, eg to separate isomers of disubstituted benzenes. Also known is the effect of cyclodextrins on the chemical reactions. As a result of the inclusion complex, the guest molecule is isolated from the external environment. The cyclodextrin molecule provides the appropriate microenvironment during the reaction and thus affects the speed, selectivity or reaction mechanism.

Hydroxy groups of cyclodextrins can be modified by using reactions known from carbohydrate chemistry. This additionally enhances the potential of cyclodextrins.

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