Basic Knowledge about Cyclodextrins and Their Derivatives

(A) Cyclodextrins are a series of non-reducing oligosaccharide compounds derived from starch, consisting of six or more D-pyranose glucopyranose units linked by alpha-1,4-glycosidic bonds. They have a cyclic, hydrophobic, conical structure (cyclodextrin model rotated upward to the right). Within this cyclodextrin family, their names are based on the number of glucose groups in the ring. Cyclodextrins composed of six D-pyranose glucopyranose units are called alpha-cyclodextrin (alpha-CD), those with seven are called beta-cyclodextrin (beta-CD), and those with eight are called gamma-cyclodextrin (gamma-CD). These three cyclodextrins are the most commonly used and are also referred to as base cyclodextrins. Chemically modified versions of these three base cyclodextrins are called base cyclodextrin derivatives, also known as cyclodextrin derivatives. Villiers first discovered cyclodextrins in 1891 when he isolated a crystalline substance (later called cyclodextrin) from potato starch using a culture medium containing Bacillus. Currently, bacteria used in the industrial production of cyclodextrins use a natural enzyme, cyclodextrin-glucosyl-transferase (CGTase). CGTase cuts the spiral starch from both ends and connects it to form a hydrophobic conical ring. Since the cut starch have different lengths, three different cyclodextrins are produced.

(B) Cyclodextrins and their derivatives are widely used in various scientific and industrial fields, such as food and beverages, cosmetics, agriculture, pharmaceuticals, textiles, fragrances, nano-coatings, chemical analysis, molecular recognition, and catalysis. Today, cyclodextrin chemistry has even entered the forefront of molecular information science, becoming a key supramolecular chemistry discipline. Why is cyclodextrin technology so captivating and a vibrant scientific field today? The primary reason is their unique hydrophobic, cylindrical molecular structure. This unique molecular structure is exploited for inclusion complexation and molecular recognition of a wide range of organic compounds. By encapsulating guest molecules within the conical cavity within the molecule, a non-bonded host-guest complex is formed, which can modify and protect the physical, chemical, and biological properties of the guest compound.

(C) Based on our current understanding of cyclodextrins, the following industries can generally consider using cyclodextrins:

1. To prevent UV degradation and oxidation during product storage or processing;

2. To stabilize flavor and aroma;

3. To mask unpleasant flavors such as spiciness and bitterness in food and pharmaceutical applications;

4. To reduce drug irritation to the skin, gastrointestinal tract, or blood vessels;

5. To provide a balanced, slow release of drugs to the body, improving drug bioavailability and reducing toxicity and side effects;

6. To solidify liquid substances;

7. To solidify gaseous substances;

8. To increase the solubility of encapsulated complex guest substances;

9. To emulsify fats, fatty acids, steroids, and hydrocarbons;

10. To control the release of flavors and drugs;

11. To act as a catalyst for chemical reactions;

12. To act as a chemical synthesis intermediate;

13. To serve as an HPLC reagent or the mobile and stationary phases of TLC;

14. Remove harmful substances from food, cosmetics, or pharmaceuticals;

15. Prevent interactions between active ingredients and between active ingredients and dressings in pharmaceutical formulations;

16. Deliver effective drugs in a targeted manner.