Cyclodextrins (EU), or CDs, are cyclic oligosaccharides with a defined ring size that are used in foods, cosmetics, home care products, and pharmaceuticals for active encapsulation and delivery. There are three basic types of natural CDs (alpha, beta, and gamma), which are produced from starch by enzymatic conversion. The bucket-shaped molecule has a hydrophilic exterior and a hydrophobic cavity and is able to form inclusion complexes with many organic guest compounds.
Alpha has the smallest cavity, gamma the largest, and beta has an intermediate size. Alpha works the best with low MW materials and gamma for those with high MW. C log P and molecular weight usually determine which CD will form the best complex with the highest binding constant. Complexation and release mainly depend on temperature and moisture conditions. Beta CD is the most frequently used CD. It has a water solubility of 1.9% and is normally used to make insoluble complexes. Hydroxypropyl (EU) Beta Cyclodextrin is typically used to form water soluble complexes.
Applications of Cyclodextrins
- Increased solubility and bioavailability of actives.
- Reduced volatility (EU).
- Stabilization of actives (light, oxidation, temperature).
- Selective extraction (Cholesterol).
- Taste masking.
- Odor control.
- Extended release of fragrances, flavors, and antimicrobials (EU).
- Moisture-triggered release.
- Making Pickering emulsions.
Commercially Available CDs
- Hydroxypropyl alpha, beta, and gamma cyclodextrins.
- Methylated beta cyclodextrin.
- Alpha, beta, and gamma cyclodextrins.
Procedure for Making Insoluble Complexes
- Make an aqueous slurry containing 40% beta Cyclodextrin (BCD) and 56% water. Add 4% active and mix for an hour. You can heat the slurry or dissolve the active in a water soluble solvent to help facilitate complexation. Spread slurry on pan and dry. Grind dried powder to reduce particle size.
- Most complexes are 1 to 1 or 1 to 2 active/BCD on a molar basis. A 1 to 10 ratio on a weight basis active/BCD is normally a good starting point
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