Host–guest inclusion complexes ofβ-cyclodextrin with two vitaminsviz., nicotinic acid and ascorbic acid in aqueous medium have been explored by reliable spectroscopic, physicochemical and calorimetric methods as stabilizer, carrier and regulatory releaser of the guest molecules. Job’s plots have been drawn by UV-visible spectroscopy to confirm the 1:1 stoichiometry of the host-guest assembly. Stereo-chemical nature of the inclusion complexes has been explained by 2D NMR spectroscopy. Surface tension and conductivity studies further support the inclusion process. Association constants for the vitamin-β-CD inclusion complexes have been calculated by UV-visible spectroscopy using both Benesi–Hildebrand method and non-linear programme, while the thermodynamic parameters have been estimated with the help of van’t Hoff equation. Isothermal titration calorimetric studies have been performed to determine the stoichiometry, association constant and thermodynamic parameters with high accuracy. The outcomes reveal that there is a drop in ΔS^o, which is overcome by higher negative value of ΔH^o, making the overall inclusion process thermodynamically favorable. The association constant is found to be higher for ascorbic acid than that for nicotinic acid, which has been explained on the basis of their molecular structures.

Studies of molecular inclusions of a congener series of guest amino acid molecules into the host cavity of α and β-cyclodextrins in aqueous solution have been focused on modern research gaining far reaching effect. With both the α and β-cyclodextrins, it is found that 1 : 1 hosts–guest inclusion complexes are formed with all the guest molecules at both low and high pH. The variation of the thermodynamic parameters with guest size and state are used to draw inferences about contributions to the overall binding from the driving forces, viz., hydrophobic effect, van der Waals forces, H-bonds, electrostatic forces, structural effect and configurational theory. The formation and comparative study of inclusion complexes have been analyzed by available data supplemented with surface tension, pH, density, viscosity, and refractive index.

Host-guest interaction of two significant drugs, phenylephrine hydrochloride and synephrine with α and β-cyclodextrins were studied systematically. Initially two simple but reliable physicochemical techniques namely conductance and surface tension were employed to find out saturation concentration for the inclusion and its stoichiometry. The obtained 1:1 stoichiometry was further confirmed by two spectrometric methods, UV-Vis study and spectrofluorimetry. Significant shifts in IR stretching frequency also support the inclusion process. Relative stabilities of the inclusion complexes were established by the association constants obtained from UV-Vis spectroscopic measurements, program based mathematical calculation of conductivity data. Calculations of the thermodynamic parameters dictates thermodynamic feasibility of the inclusion process. Spectrofluorometric measurement scaffolds the UV-Vis spectroscopic measurement validating stability of the ICs once again. Mass spectroscopic measurement gives the molecular ion peaks corresponding to the inclusion complex of 1:1 molar ratio of host and guest molecules. The mechanism of inclusion was drawn by ¹H-NMR and 2D ROESY spectroscopic analysis. Surface texture of the inclusion complexes was studied by SEM. Finally, the cytotoxic activities of the inclusion complexes were analyzed and found, Cell viability also balances for non-toxic behavior of the ICs. Moreover, all the studies reveal the formation of inclusion complexes of two ephedra free, alternatively emerging drugs (after their banned product having ephedra) SNP, PEH with α and β-CD which enriches the drug delivery system with their regulatory release without any chemical modification.

Stable host–guest inclusion complexes have been formed with guest RNA nucleosides inside aqueous α- and β-cyclodextrins. α-Cyclodextrin has been found to have favorable structural features for inclusion with uridine and cytidine, whereas β-cyclodextrin has that with all the four nucleosides, e.g., adenosine, guanosine, uridine and cytidine. The formation and nature of the inclusion complexes have been characterized using surface tension study, Job's method by ultraviolet spectroscopy and pH measurements. The limiting apparent molar volume, viscosity B-coefficient, limiting apparent molar adiabatic compressibility and limiting molar refraction data have been used to characterize the interaction between nucleosides and cyclodextrins in the experimental ternary solution systems. The inclusion phenomenon has been confirmed by proton NMR study. Association constants and thermodynamic parameters have been evaluated for the formed inclusion complexes by ultraviolet spectroscopy.

The assembly of two natural amino acids (viz., L-arginine and L-histidine) as guests with α and β-cyclodextrins as hosts to form inclusion complexes in aqueous medium has been demonstrated which are highly suitable for diverse applications in modern bio-medical sciences. The ¹H NMR study establishes the formation of inclusion complexes, while surface tension and conductivity studies confirm that the inclusion complexes have been formed with 1 : 1 stoichiometry. The nature of the complexes has been established using thermodynamic parameters, based on density, viscosity, and refractive index measurements. The contributions of different groups of the guest molecules towards the limiting apparent molar volume and the viscosity-B coefficient are determined and solvation numbers are calculated. All the parameters support the formation of the inclusion complexes, which are explained based upon hydrophobic effects, H-bonds, electrostatic forces and structural effects.