title: Structural and physicochemical characterization of the inclusion complexes of cyclomaltooligosaccharides (cyclodextrins) with melatonin.
abstract: The stoichiometry, geometry, stability, and solubility of the inclusion complexes of melatonin (MLT) with native cyclomaltooligosaccharides (alpha-, beta- or gamma-cyclodextrins, CDs) are determined experimentally by high-resolution NMR spectroscopy, calorimetric and solubility measurements, and mass spectrometry. The observed differences are discussed in terms of molecular recognition expression of the host-guest (h-g) interactions within the hydrophobic CDs cavities of different size. The 1:1 h-g stoichiometry in water solution prevails at low CD concentrations; the trend to form higher order associations is observed at increasing CD concentrations. The stability order beta-CD>gamma-CD>alpha-CD for the complexes in water solution and beta-CD>alpha-CD>gamma-CD for the protonated or alkali-cationated complexes in the gas phase are rationalized on the grounds of the structural data from NMR spectroscopy and of the thermodynamic parameters from calorimetric measurements.
authors.affiliation: Dipartimento di Chimica e Tecnologie Farmaceutiche e Rete di Spettrometria di Massa del Mezzogiorno, Via Archirafi 32, I-90123 Palermo, Italy.
authors.forename: David
authors.initials: D
authors.lastname: Bongiorno
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Ceraulo
authors.forename: Andrea
authors.initials: A
authors.lastname: Mele
authors.forename: Walter
authors.initials: W
authors.lastname: Panzeri
authors.forename: Antonio
authors.initials: A
authors.lastname: Selva
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Turco Liveri
mesh_terms: D002151:Calorimetry; D003505:Cyclodextrins / Q000737:chemistry*; D005079:Excipients / Q000737:chemistry; D008550:Melatonin / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D012995:Solubility; D021241:Spectrometry, Mass, Electrospray Ionization; D013816:Thermodynamics
chemical_list: D003505:Cyclodextrins; D005079:Excipients; D008550:Melatonin