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Differentiating geometrical isomers Differentiating geometrical isomers of retinoids and controlling their of retinoids and controlling their

photo-isomerization by photo-isomerization by complexation with cyclodextrinscomplexation with cyclodextrins

Analytica Chimica Acta 468 (2002) 161-170

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CyclodextrinsCyclodextrins

Cyclic oligosaccharidesCyclic oligosaccharides

Composed of D(+)glucopyranose unitsComposed of D(+)glucopyranose units

Hollow, torus-shape cavityHollow, torus-shape cavity

Cylinders with a Cylinders with a hydrophilic exteriorhydrophilic exterior and a and a hydrophobichydrophobic interiorinterior

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CyclodextrinsCyclodextrins

DifferentDifferent typestypes::

αα-cyclodextrin -cyclodextrin : six sugar ring molecules: six sugar ring molecules

ββ-cyclodextrin -cyclodextrin : seven sugar ring molecules: seven sugar ring molecules

γγ-cyclodextrin-cyclodextrin : eight sugar ring molecules: eight sugar ring molecules

55

Structure of Structure of αα-CD-CD

66

Structure of Structure of ββ-CD-CD

Structure of Structure of γγ-CD-CD

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CyclodextrinsCyclodextrins

They form inclusion complexes with a They form inclusion complexes with a variety of moleculesvariety of molecules..

Insertion of a Insertion of a hydrophobichydrophobic guest in guest in aqueousaqueous solutions of cyclodextrins leads to solutions of cyclodextrins leads to complexation which no covalent bonds are complexation which no covalent bonds are broken or formedbroken or formed..

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Applications of Cyclodextrins in Drug Applications of Cyclodextrins in Drug delivery technologydelivery technology

To improve the physical and chemical To improve the physical and chemical properties of drugsproperties of drugs

To reduce the side effects of drugsTo reduce the side effects of drugs

To enhance the bio-availibility of poorly To enhance the bio-availibility of poorly soluble drugssoluble drugs

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Applications of Cyclodextrins in Food Applications of Cyclodextrins in Food industryindustry

To stabilize flavors and fragrancesTo stabilize flavors and fragrances

To mask undesired tastes in the food and To mask undesired tastes in the food and cosmetic industriescosmetic industries

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Applications of Cyclodextrins ChemistryApplications of Cyclodextrins Chemistry

Separation Separation techniques HPLC andtechniques HPLC and… …

Increasing the Increasing the solubilitysolubility and the and the stabilitystability of the of the analytes and therefore analytes and therefore sensitivitysensitivity of the of the detection of these analytesdetection of these analytes

Increasing or decreasing the Increasing or decreasing the raterate of a variety of of a variety of reactionsreactions

……

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RetinoidsRetinoids

Very significant biological molecules due toVery significant biological molecules due to : :

- -Their role in the Their role in the visionvision process (retinal) process (retinal)

- -As As vitaminsvitamins (retinol and its esters) (retinol and its esters)

- -Their influence in the Their influence in the cell growthcell growth (retinoic (retinoic acid , …) acid , …)

1212

All trans retinalAll trans retinal

1313

H-NMR spectra of the pure H-NMR spectra of the pure ββ-CD solution -CD solution (C=1.0 x 10(C=1.0 x 10-2-2 M) M)

1414

H-NMR spectra of the complex of all-trans-retinal/H-NMR spectra of the complex of all-trans-retinal/ββ-CD at -CD at concentrations 4.0 x 10concentrations 4.0 x 10-3-3 and 1.0 x 10 and 1.0 x 10-2-2 M respectively M respectively..

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Chemical shifts in H-NMRChemical shifts in H-NMR

1616

Stoichiometry determinationStoichiometry determination

1717

Association constants determinationAssociation constants determination

1818

99--Cis retinalCis retinal

1919

Effect of the inclusion process on the Effect of the inclusion process on the photo-isomerization of retinoidsphoto-isomerization of retinoids

2020

Ethanolic solutionEthanolic solution

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All-trans-retinalAll-trans-retinal

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All-trans-retinoic acidAll-trans-retinoic acid

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