Transcript ppt
1 Differentiating geometrical isomers of retinoids and controlling their photo-isomerization by complexation with cyclodextrins Analytica Chimica Acta 468 (2002) 161-170 2 Cyclodextrins Cyclic oligosaccharides Composed of D(+)glucopyranose units Hollow, torus-shape cavity Cylinders with a hydrophilic exterior and a hydrophobic interior 3 Cyclodextrins Different types: α-cyclodextrin : six sugar ring molecules β-cyclodextrin : seven sugar ring molecules γ-cyclodextrin : eight sugar ring molecules 4 Structure of α-CD 5 Structure of γ-CD Structure of β-CD 6 Cyclodextrins They form inclusion complexes with a variety of molecules. Insertion of a hydrophobic guest in aqueous solutions of cyclodextrins leads to complexation which no covalent bonds are broken or formed. 7 Applications of Cyclodextrins in Drug delivery technology To improve the physical and chemical properties of drugs To reduce the side effects of drugs To enhance the bio-availibility of poorly soluble drugs 8 Applications of Cyclodextrins in Food industry To stabilize flavors and fragrances To mask undesired tastes in the food and cosmetic industries 9 Applications of Cyclodextrins Chemistry Separation techniques HPLC and … Increasing the solubility and the stability of the analytes and therefore sensitivity of the detection of these analytes Increasing or decreasing the rate of a variety of reactions … 10 Retinoids Very significant biological molecules due to : - Their role in the vision process (retinal) - As vitamins (retinol and its esters) - Their influence in the cell growth (retinoic acid , …) 11 All trans retinal 12 H-NMR spectra of the pure β-CD solution (C=1.0 x 10-2 M) 13 H-NMR spectra of the complex of all-trans-retinal/β-CD at concentrations 4.0 x 10-3 and 1.0 x 10-2 M respectively. 14 Chemical shifts in H-NMR 15 Stoichiometry determination 16 Association constants determination 17 9-Cis retinal 18 Effect of the inclusion process on the photo-isomerization of retinoids 19 Ethanolic solution 20 All-trans-retinal 21 All-trans-retinoic acid 22 Thanks 23