Analytical applications of retinoid–cyclodextrin inclusion complexes. Part 2. Luminescence properties at room temperature
Retinoids are polyenic molecules of biological importance. They are generally very hydrophobic. This paper describes the luminescence behaviour of inclusion complexes between all-trans-retinal and its geometric isomers, 9-cis and 13-cis-retinal, retionic acid, retinol and retinyl acetate and different cyclodextrins (CDs), viz., α-, β and γ-CD, as well as the modified dimethyl-β-CD, trimethyl-β-CD and hydroxypropyl-β-CD. These complexes were found to emit room-temperature luminescence. The position and intensity of the observed emission maxima depend on the CD and on the guest retinoid. The formation of these inclusion complexes was also followed by UV–visible spectrophotometry. The results obtained allow the quantitative and selective determination of retinoids in aqueous solution owing to the solubility of these inclusion complexes in water.