Probing Inclusion Complexes of Pentoxifylline and Pralidoxim inside Cyclic Oligosaccharides by Physicochemical Methodologies

Structurally different Molecules namely Pentoxifylline and Pralidoxim were chosen along with α-cyclodextrin and β-cyclodextrin to study host-guest inclusion phenomena. The formations of host guest inclusion complexes were confirmed by studying 1H-NMR spectra, FT-IR spectra, apparent molar volume and viscosity co-efficient. The stabilities of inclusion complexes were compared calculating the binding constant from UV-VIS spectroscopic study. The 1:1 stoichiometry of the inclusion complexes were also determined by analysing the Jobs plot and surface tension data. The values for Gibbs’ free energy were found negative for both the processes. Based on all the above experiments the inclusion processes were found feasible for both the compounds. These types of inclusion complexes are of high interest in the field of research and industry as these are used as drug delivery systems.

Size exclusion effect in binary inclusion compounds of α-cyclodextrin

The size exclusion of guests by α-cyclodextrin (aCD) in binary host-guest systems was observed to be a key structure-property relationship for the choice of this host as a receptor. For this, vapor sorption isotherms of water and volatile organic compounds were determined using dry aCD, which show an inclusion threshold by sorbate activity corresponding to a phase transition of guest (or water) inclusion. These phase transitions were also characterized using X-ray powder diffractograms. The analysis of these data shows that interaction of aCD with water does not differ much from that with organic compounds that can be included by aCD without water and therefore are water-mimicking as such. The inclusion and hydration Gibbs energies and composition of the saturated host-guest clathrates were determined from sorption isotherms. The Gibbs energies of guest inclusion by solid aCD and its hydration characterize the guest-host and water-host affinity in the solid state. The correlation of the obtained inclusion parameters with that of guest size indicate the ban on the inclusion of volatile hydrophilic organic compounds with more than three carbon atoms and smaller molecules without hydrophilic groups. These data may be used for estimation of the relative ability of more hydrophobic guests to replace water and organic solvents in solid aCD. The observed inclusion of water and small hydrophilic molecules by solid aCD with phase transition gives an alternative insight into the role of water in activating the inclusion of more hydrophobic guests. Furthermore, the results show the extent to which aCD may be preferable in applications using water or other solvents.

Distinguishing enantiomeric amino acids with chiral cyclodextrin adducts and structures for lossless ion manipulations

Enantiomeric molecular evaluations remain an enormous challenge for current analytical techniques. To date, derivatization strategies and long separation times are generally required in these studies, and the development and implementation of new approaches are needed to increase speed and distinguish currently unresolvable compounds. Herein, we describe a method using chiral cyclodextrin adducts and structures for lossless ion manipulations (SLIM) and serpentine ultralong path with extended routing (SUPER) ion mobility (IM) to achieve rapid, high resolution separations of d and l enantiomeric amino acids. In the analyses, a chiral cyclodextrin is added to each sample. Two cyclodextrins were found to complex each amino acid molecule (i.e. potentially sandwiching the amino acid in their cavities) and forming host-guest noncovalent complexes that were distinct for each d and l amino acid pair studied and thus separable with IM in SLIM devices. The SLIM was also used to accumulate much larger ion populations than previously feasible for evaluation and therefore allow enantiomeric measurements of higher sensitivity, with gains in resolution from our ultralong path separation capabilities, than previously reported by any other IM-based approach.

Cyclodextrin-Catalyzed Organic Synthesis: Reactions, Mechanisms, and Applications

Cyclodextrins are well-known macrocyclic oligosaccharides that consist of α-(1,4) linked glucose units and have been widely used as artificial enzymes, chiral separators, chemical sensors, and drug excipients, owing to their hydrophobic and chiral interiors. Due to their remarkable inclusion capabilities with small organic molecules, more recent interests focus on organic reactions catalyzed by cyclodextrins. This contribution outlines the current progress in cyclodextrin-catalyzed organic reactions. Particular emphases are given to the organic reaction mechanisms and their applications. In the end, the future directions of research in this field are proposed.

Subsistence of inclusion complex via assembly of a drug into cyclic oligosaccharide: Its formation, mechanism, behaviour and importance

The aim of this present work is to make soluble DEPM in aqueous medium through the formation inclusion complex into the hydrophobic hollow space of β-cyclodextrin (β-Cyd) which will provide a novel approach for designing drug delivery system in aqueous medium. The study of supramolecular complexation of DEPM with β-Cyd has been designed in both solution and solid state. In solution phase the evidences of the presence of non-covalent interactions in inclusion complex with 1:1 stoichiometry behaviour are obtained by investigating the UV-spectroscopy. The resultant solid of DEPM and β-Cyd is established by ¹H NMR, FTIR, powder XRD and SEM techniques. So, β-Cyd has the ability to encapsulate DEPM into their core without formation any covalent bonds and also increases the bioavailability of the water insoluble DEPM drug.

Study on Host-Guest Inclusion Complexation of a Drug in Cucurbit [6]uril

Assembly of pyridine-2-aldoxime drug with cucurbit [6]uril (CB[6]) has been investigated by 1H-NMR and 2D-ROESY NMR, UV-Vis spectroscopy, FT-IR spectroscopy, surface tension and conductivity measurements in aqueous saline environment. The distinct cationic receptor feature and the cavity dimension of the CB[6] emphasize that the macro-cyclic host molecule remain as complex with the nerve stimulus drug molecule. The results obtained from surface tension and specific conductivity measurements suggest 1:1 inclusion complex formation between drug and CB[6]. The stability constant evaluated by UV-Vis spectroscopic approach is 2.21×105 M−1 at 298.15 K, which indicates that the complex is sufficiently stable at physiological temperature.

Probing Inclusion Complex Formation of Amantadine Hydrochloride with 18-Crown-6 in Methanol by Physicochemical Approach

The complex formation of amantadine hydrochloride with 18-crown-6 was studied in methanol solution by surface tension, conductivity and IR study. The limiting apparent molar volume data have been used to characterize the interaction between drug molecule (amantadine hydrochloride) and 18-crown-6 in the experimental ternary solution systems. A conductance study concerning the interaction between cationic organic ammonium ions amantadine with 18-crown-6 in methanol solution has been carried out at different temperatures. The formation constant (logK f ) of the resulting 1:1 complex at various temperatures was determined from the conductivity study. The enthalpy (ΔH 0) entropy (ΔS 0) and free energy change (ΔG 0) of the complexation reaction was determined from the temperature dependence of the formation constant.

Probing inclusion complexes of cyclodextrins with amino acids by physicochemical approach

Formations of host-guest inclusion complexes of two natural amino acids, viz., l-Leucine and l-Isoleucine as guests with α and β-cyclodextrins have been investigated which include diverse applications in modern science such as controlled delivery in the field of pharmaceuticals, food processing etc. Surface tension and conductivity studies establish the formation of inclusion complexes with 1:1 stoichiometry. The interactions of cyclodextrins with amino acids have been supported by density, viscosity, refractive index, hydration and solvation number measurements indicating higher degree of inclusion in case of α-cyclodextrin. l-Leucine interacts more with the hydrophobic cavity of cyclodextrin than its isomer. With the help of stability constant by NMR titration, hydrophobic effect, H-bonds and structural effects the formations of inclusion complexes have been explained.

The strategy of two-scale interface enrichment for constructing ultrasensitive SERS substrates based on the coffee ring effect of AgNP@β-CD

Herein we introduced a Raman technique for the detection of aromatic compounds. The combination of the pre-concentration of β-CD and the SERS effect of the coffee-ring enhanced the detection ability of SERS to aromatic compounds.

Insertion behavior of imidazolium and pyrrolidinium based ionic liquids into α and β-cyclodextrins: mechanism and factors leading to host–guest inclusion complexes

The encapsulation of [BMIm]Cl and [BMP]Cl within α and β-cyclodextrin in both the solid state and aqueous solution with 1 : 1 supramolecular assembly.

Host–guest inclusion complexes of RNA nucleosides inside aqueous cyclodextrins explored by physicochemical and spectroscopic methods

Spectroscopic and physicochemical studies reveal formation of host–guest inclusion complexes of RNA nucleosides inside hydrophobic cavity of α and β-cyclodextrins.