Molecular Mechanics Study of the Inclusion of Trimethylbenzene Isomers in α-Cyclodextrin

Molecular mechanics calculations were employed to study the inclusion of triethylbenzene isomers in -cyclodextrin and their solvation energy in aqueous solution. Trimethylbenzene penetrates partially into the cavity of -cyclodextrin to form 1 : 1 or 2: 1 host–'guest complexes. The interaction energy between host and guest is dominated by van der Waals energy. The inclusion complexes have higher solvationenergies than free -cyclodextrin.     

A Study on the Inclusion of α-Cyclodextrin with Mono-and 1,4-Disubstituted Benzenes by Neural Networks

Itiswellknownthatthecycledextrin(CD)isonekind0ftheidealenzyrnemedels.ThestudiesofcycboextrininmoIecularrmpition,mimeticenzyTneandseParationscienceandtechnolOgyhavebenexPeriencedanenormousinterestintherecentyears.l-5Inspite0fafewdrivingforceshavebenprohof0rtheinclusionofCDwithavarietyofgUestco~nds,therestillrernainsnoclearagreeInent0nthemechanisrnf0rCDinclusioncomPlexation.Daviesetal"'estabIishedamedelfortheinclusionofQ-CDwithl,4-disubstitutedbenzenesbased0naregress1onanalysis.According…     

Effect of Temperature-responsive Solution Behavior of PNIPAM-bPPEOMA-b-PNIPAM on Its Inclusion Complexation with α-Cyclodextrin

The effect of temperature-responsive solution behavior of PNIPAM-b-PPEOMA-b-PNIPAM on its inclusion complexation with α-cyclodextrin was studied. The triblock polymer was prepared by reversible addition-fragmentation chain transfer(RAFT) polymerization and formed inclusion complexes(ICs) after selective threading of the PEO segment of the triblock polymer through the cavities of α-CD units. For comparison, PPEOMA homopolymer was prepared and the inclusion complexation with α-CD was also studied. The ICs were prepared with α-CD when the polymer was in different conformations by changing the temperature, and the formed ICs were characterized by XRD, 1H-NMR, TGA and DSC. The solutions of the ICs show temperature-responsive clear/turbid transition or fluidic emulsion/gel transition depending on the concentration of the α-CD added, and the stoichiometry determined by 1H-NMR and TGA indicates that the stoichiometry of EO to α-CD of the resulted ICs increases with increasing of temperature.     

Comparative Study on the Inclusion Complexation of Rutin with Cyclodextrin Supramolecules

Naturalandchemicallymodifiedcyclodextrinshaveabilitytorecogformanyinorgan-..icororganlcguestmoleculesfOrminghost-guestinclusioncomplexest13.Inrecentyears,increasingattentionhasbeenpaidtoalterphisical,chemicalandbiologicalpropertiesofmolecules'-Theunderstanding'ofthebehaviorofthedrugincyclodextrionmicroenwton-mentisaprerequisitetodevelopmentofanovelandeffectivecarrierspptemforthedrug.6-CDcanforminclusioncomplexeswithrutin[2J.WereporthereastudyoninclusioncomplexationofcyClodextrinsbyfluorAnetr…     

A Study of the Driving Force for Inclusion Complexation of α- and β-Cyclodextrin with Substituted Benzene

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Theoretical Study on the Inclusion Complex of β-Cyclodextrin and Nitrobenzene

Quantum chemical calculations were carried out to investigate the structures and properties for the inclusion complexes of nitrobenzene (NB) into β-cyclodextrin. Two low-energy conformations of β-cyclodextrin (A and B) in the gas phase were initially investigated by the PM3 and B3LYP/6-31+G(d,p) calculations, respectively. Three different orientations were considered in the inclusion process of A and B with NB to form 1:1 complexes. Potential energy scan by PM3 calculations indicated that the phenyl orientation Ab for conformation A and the equator orientation Bc for conformation B are more favorable in energy, respectively. We also considered the 2:1 inclusion complexes of host A or B with guest NB in the gas phase. PM3 calculation indicated that the host-guest interaction energies to form 1:1 complexes are more negative than those to form 2:1 NB/B complexes. Finally, we studied the solvent effect of NB/CD complex, and PM3 results show that the influence of water molecules on the inclusion process is very important. The driving forces for the inclusion process and the geometries of complexes were discussed in detail.     

Study on the Supramolecular Inclusion Complex of β-Cyclodextrin/Lappaconitine

Lappaconitine (Lap) is a diterpenoid akaliamide, naturally occurring in roots and rhizomes of Aconitum and delphinium. Lap reveals bradycardic, hypotensive, antinocieptive activity. However, its application is restrained owing to its poor water solubility, toxicity and side effects on humans. In a number of pharmaceutical studies,CDs have been reported to interact with many drug molecules to form inclusion complexes. These inclusion complexes have been extensively used to improve water solubility of poorly soluble drugs, to reduce their toxicity, and to increase the dissolution rate [1]. In the present work, the β-CD/Lap complex was prepared by kneading method. The products have been characterized by the solubility measurement as well as UV, FTIR, NMR spectroscopy and X-ray powder diffractometry.     

Solubility Study of Nimodipine Inclusion Complexation with α- and β-Cyclodextrin and some Substituted Cyclodextrins

The solubility of nimodipine was measured in aqueous solutions of the following cyclodextrins: -cyclodextrin (-CD), hydroxypropyl--CD (HP--CD), -cyclodextrin (-CD), random substituted methyl--CD (M--CD), three hydroxypropyl--CDs (HP--CD) with mutually different average degree of substitution, and hydroxypropyl--cyclodextrin (HP--CD). From the determined linear solubility diagrams the values of the binding constant K₁₁ of the inclusion complexes of nimodipine with the respective CDs were evaluated. The -CDs efficiently solubilized sparingly soluble nimodipine, the highest value of K₁₁ was found for M--CD (1680 M^-1), followed by -CD (550 M^-1) and HP--CDs, where the higher degree of substitution lowered K₁₁. Only slight solubilization of nimodipine was observed in the solutions of the -CDs and HP--CD.     

Study of the Podophyllotoxin β-Cyclodextrin Inclusion Complex

The structure of the podophyllotoxin (P)/-cyclodextrin(-CD) inclusion complexhas been studied by infrared spectroscopy, UVspectroscopy, NMR spectroscopy and X-raydiffractometry. The association constant is 128 M^-1in water, calculated from thestraight portion of the phase-solubility diagram.     

Interplay between Molecular Recognition and Redox Properties: A Theoretical Study of the Inclusion Complexation of β-Cyclodextrin with Phenothiazine and its Radical Cation

The PM3 molecular orbital method was employed in the conformational analysis of the inclusion complexation of -cyclodextrin with phenothiazine and its radical cation from a complete and unrestricted geometry optimization. Ab initio calculations at the level of HF/3-21G(d) and B3LYP/3-21G(d) were utilized to determine the electronic structures of the host, guest and their complexes. The results indicated that the complexation of -cyclodextrin with the phenothiazineradical cation was significantly more favorable than that with the neutral one, in good agreement with the experimental observation. The charge-transfer interaction was proposed as a physical reason for such behavior. It is suggested that caution should be given when extrapolating one oxidation state behavior to the supramolecular systems in their other oxidation states.     

Experimental and Theoretical Studies on the Inclusion Complexation of β-Cyclodextrin with Phenothiazine Derivatives

Inclusion complexation of -cyclodextrin (-CD) with N-phenylphenothiazine ( 1), N-benzylphenothiazine ( 2) and N-phenethylphenothiazine ( 3) has been studied by means of UV-vis spectroscopy and molecular dynamics simulations. The association constants (K_a) were determined to be 126, 312 and 211 dm³/mol for inclusion of -CD with 1, 2 and 3, respectively. It shows that the K_a values are affected by the substituents of the guest compounds. The structures of the complexes and the conformation of the guest compounds bound by -CD in the complex have been discussed.     

Study of the Supramolecular Inclusion of β-Cyclodextrin with Andrographolide

An inclusion complex of -cyclodextrin with andrographolide (Andro) was prepared by using a convenient new method of microwave irradiation. The structure of the inclusion complex was determined by UV and IR analyses as well as ¹H NMR, ¹³C NMR and two dimensional NOE spectroscopic measurements. The results indicated that the possible stoichiometry of complex formation is 1:1 (guest:host ratio) and the two isomeric 1:1 inclusion complexes are present simultaneously in solution. Thermal studies proved the thermal stability of the inclusion complex.     

Substituent Effects on the Driving Force for Inclusion Complexation of α- and β-Cyclodextrin with Monosubstituted Benzene Derivatives

The association constant values, K_a, for the inclusion of - and -CD with monosubstituted benzene derivatives were determined by means of UV-vis and fluorescence spectroscopy. The stability of the complexes is influenced by the properties of the substituents of the guest compounds. Regression analysis was used to create a set of inclusion models with the experimental association constant ln K_a and the corresponding substituent molar refraction R_m, hydrophobic constant and Hammett constant of the benzene derivatives. The ln K_a value mainly correlated with R_m for -CD and with both R_m and for -CD complexes. The association constants predicted by the models are in good agreement with the experimentally determined data. This suggests that the inclusion complexation of benzene derivatives with -CD is predominantly driven by van der Waals force and with -CD mainly by van der Waals force and hydrophobic interactions.     

Study on the Structure of Supramolecular Inclusion Complex of β-Cyclodextrin with Retinoic Acid

The importance of Vitamin A for human health has been stressed in resent studies1, meanwhile its derivative so-called retinoic acid (RA) has been widely used as pharmaceutical to treat several types of skin disease and cancer2,3. However the application of retinoic acid is restrained for its poor water solubility, unstability and side effect on the human body.Cyclodextrins (CDs) are macrocyclic oligosaccharides built up from 6, 7, or 8 glucopyranose units called (, (, and (-CD, respectively…     

1H-NMR Study on Inclusion Modes of 2-Chloronaphthalene and α-Cyclodextrin in D2

Abstract

With a 1:1 and a 2:1 host-guest stoichiometry, α-cyclodextrin (α-CD) forms inclusion complexes with 2-chloronaphthalene. From simulations concerning observed chemical-shift differences (Δδ_obs) of proton signals of 2-chloronaphthalene, intrinsic Δδ values are estimated for all the guest protons in the 1:1 and 2:1 inclusion complexes. The intrinsic Δδ values indicate that α-CD first binds to a part of a naphthalene ring bearing a C1 atom to form the 1:1 inclusion complex. In the 1:1 and 2:1 inclusion complexes, the symmetry axes of α-CD are tilted approximately 30° relative to a naphthalene longitudinal axis. In the 2:1 inclusion complex, the association through hydrogen bonding most likely occurs between two α-CD molecules whose symmetry axes are laterally shifted.     

Study on Molecular Recognition of Pinocembrin with Methylated-β-Cyclodextrin

The inclusion behavior, inclusion capacity and inclusion mode of pinocembrin (PIN) with dimethyl-β-cyclodextrin (DM-β-CD) and trimethyl-β-cyclodextrin (TM-β-CD) were characterized by X-ray diffraction (XRD), thermal analysis, scanning electron microscopy (SEM), UV-visible spectral titration and molecular docking. The results showed that the packing ratio of PIN/DM-β-CD complex and PIN/TM-β-CD complex was 1:1. The water solubility of PIN increased by 817 times and 575 times in the inclusion complex with DM-β-CD and TM-β-CD, respectively. Molecular docking showed the PIN entered from the large end of the DM-β-CD molecule and penetrated through the cavity. The A and B rings of the PIN were respectively located at the big and small ends of the CD molecule. For the TM-β-CD, only A and C rings of the PIN entered the cavity of CD.     

NMR Study of the Inclusion Complexes of Carboxy-Phenoxathiin Derivatives with β-Cyclodextrin

The inclusion complexes of the carboxylate forms of 3-carboxy-(I) and 2-carboxy-phenoxathiin (II) with -cyclodextrin were studied by bothone- and two-dimensional NMR spectroscopy. The analysis of the induced chemical shifts of theguests in the presence of different amounts of the host indicates the formation of complexes with 1:1stoichiometry and association averaged pK values of 3.75 (I) and 4.4 (II). Thequalitative analysis of cross peaks in the ROESY spectra support the inclusion of the guests in the cavitywith the substituted phenyl ring, the COO^- group being in the proximity of the primary rim.     

Theoretical Study on the Molecular Orbital and Stabilization Energy of Substituted Lithium Carbene Cations

Themetalcarbenecations,esPeciallytransitionmetalcarbenecations,areaclass0funstableintermediateswithhighactivity.TheyareveryimPortamtothefieldoforganometallicchendstryandhavegreatlyattractedchemist'sattention.JacobsonlstUdiedthereactionsofFeCH, andCoCH, withalkanes"',olefms2ingasphase.Butsofarasweknow,thereisnosystematictheoreticalstUdyontheirsmictUresandstability.InthispaPer,westUdythestfUcturalcharacteristics,molecularorbitalsofXCHLi andrelationshiPbetweensubstituelltsandstability,tak…     

A Study on the Driving Force for Binding of Benzene Derivatives by α-and β-Cyclodextrin

WehavedemonstTatedthattheassociationconstantsfortheinclusioncomplexationofa-and6-cyclodextrin(a-and9-CD)withsubstitutedbenzene(PhX)arecorrelatedwithpropertiessuchasmolarrefraction(R.),hydrophobicity(n.)andeIectroniceffect(a.)ofsubstitUentsintheguestcompounds.Uponapplicationofanariificialneuralnetwork(ANN),theassociationconstants(Ka)fortheinclusionofa-CDand6-CDwithsubstitutedbenzenewerepredictedfromR.,rrxandG.withsatisfactoryresultSl'2.Furthermore,theeffectsofsubstituentsinbenzenederivat…     

Inclusion Complexation of Carbaryl and β-Cyclodextrin in Solution and in the Solid State

This study was carried out with the aim ofinvestigating the interactions between-cyclodextrin and carbaryl, a carbamatepesticide, and their effect on some physico-chemicalproperties of carbaryl, such as aqueous solubility andlipophilicity. The interactions between carbaryl and-cyclodextrin were thoroughly investigated bothin solution and in the solid state. The effect of-cyclodextrin on the aqueous solubility ofcarbaryl was evaluated by the phase solubility method.The amount of carbaryl dissolved increased linearlywith the addition of -cyclodextrin according toan A_L type plot and without precipitation of thecomplex. The apparent stability constant of thecomplex was 289 ± 21 M^-1, assuming a 1 : 1stoichiometry; this value was confirmed by a methodbased on circular dichroism measurements.Equimolar carbaryl/-cyclodextrin solid systemswere prepared by physical-mixing and freeze-drying,and fully characterised by Differential ScanningCalorimetry, X-ray powder diffractometry and FourierTransform Infra-Red analysis. The results of the solidstate study demonstrated that the freeze-drying methodyields a system with a high degree of amorphisationand yields an inclusion complex.The dissolution profile of the pesticide was affectedby the physico-chemical properties of each solidsystem, the freeze-dried form dissolving more rapidly. However, the physical association of-cyclodextrin and carbaryl enhanced the aqueoussolubility of the insecticide as well.