Inclusion complexes of dihydroartemisinin with cyclodextrin and its derivatives: characterization,solubilization and inclusion mode

The characterization, inclusion complexation behavior and binding ability of the inclusion complexes of dihydroartemisinin with β-cyclodextrin and its derivatives, sulfobutyl ether β-cyclodextrin (SBE-β-CD), mono[6-(2-aminoethylamino)-6-deoxy]-β-cyclodextrin (en-β-CD) and mono{6-[2-(2-aminoethylamino)ethylamino]-6-deoxy}-β-cyclodextrin (dien-β-CD), were studied using phenolphthalein as a spectral probe. Spectral titration was performed in aqueous buffer solution (pH ca. 10.5) at 25 °C to determine the binding constants. The inclusion complexation behaviors were investigated in both solution and solid state by means of NMR, TG, XRD. The results showed that the water solubility and thermal stability of dihydroartemisinin were significantly increased in the inclusion complex with cyclodextrins (CDs). According to ¹H NMR and 2D NMR spectroscopy (ROESY), the A, B rings of dihydroartemisinin can be included into the cavity of CDs. The enhanced binding ability of CDs towards dihydroartemisinin was discussed from the viewpoint of the size/shape-fit concept and multiple recognition mechanism between host and guest.     

Biomimetic approach towards the preparation of hydroxyapatite and hydroxyapatite/chitosan/β-cyclodextrin nanoparticles: application to controlled drug release

Hydroxyapatite (HAp) and hydroxyapatite/chitosan/β-cyclodextrin (HAp/CS/β-CD) nanoparticles were successfully prepared in the modified simulated body fluid (SBF) solution at the physiological conditions (pH 7.4, temperature?=?37 °C). CS/β-CD nanoparticles acted as templates for the synthesis of HAp/CS/β-CD nanoparticles to improve the nanoarchitecture of HAp and its crystallinity.The nanoparticles were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Kneading and coprecipitation methods were applied to prepare the inclusion complex involving β-CD and p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin), a photosensitizer for anti-cancer drugs. The 1:1 stoichiometric ratio of the formed inclusion complex was characterized by a formation constant of 7.216?×?10² mol^?1 dm³ and analyzed by ¹H NMR, FTIR, and UV–Vis. The p-THPP delivery release in vitro was in this order: HAp/CS/β-CD?<?CS/β-CD?<?<?HAp/β-CD?<?β-CD, hinting at a better controlled release by HAp/CS/β-CD nanoparticles.     

Thermodynamic study of inclusion complexes of zaleplon with natural and modified cyclodextrins

The thermodynamics and stoichiometry of zaleplon (ZAL) complexation with different cyclodextrin derivatives [β-CD, hydroxypropyl-β-cyclodextrin (HP-β-CD), randomly methylated-β-cyclodextrin (RAMEB), sulphobutylether-β-cyclodextrin (SBE-β-CD)] in aqueous solution was studied by spectrofluorimetry and ¹H NMR spectroscopy in order to obtain a more general understanding of the driving forces behind the inclusion phenomena. Job’s plot derived from the NMR spectral data and statistical analysis of spectrofluorimetric titration data confirmed the formation of equimolar complexes in all systems tested, excluding the possibility of higher order complex formation. Furthermore, thermodynamic parameters obtained by both techniques gave similar and negative values of ΔG° for all complexes, indicating spontaneous inclusion of drug into CDs. From a thermodynamic point of view, two types of inclusions were determined. One is enthalpy driven ZAL complexation with β-CD, HP-β-CD and RAMEB, while the other is entropy driven complexation observed in the case of SBE-β-CD. The mechanisms behind each type of inclusion were discussed in detail.     

Inclusion complexes of melatonin with modified cyclodextrins

The solubility of melatonin (MT) was improved with the addition of modified cyclodextrins (CDs). The solubilities of MT in the presence of β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), mono-6-O-maltosyl-β-cyclodextrin (mono-G₂-β-CD), methyl-β-cyclodextrin (Me-β-CD), and sulfobutylether-β-cyclodextrin (SBE-β-CD) were higher than that of MT itself. In particular, the solubility of MT in the presence of SBE-β-CD was 11 times higher than that of MT itself. The stability constant (K) obtained based on the fluorescence intensity was 490 L/mol for the MT/SBE-β-CD inclusion complex. The structure of the MT/SBE-β-CD complex in aqueous solution was examined by ¹H–¹H rotating frame nuclear overhauser effect spectroscopy NMR. A 5-methoxy moiety of MT was included from the secondary hydroxyl face of SBE-β-CD. The MT/SBE-β-CD inclusion complex was prepared by the freeze-drying method. The results of X-ray diffraction and differential scanning calorimetry confirmed the formation of the complex in solid.     

Novel supramolecular block copolymer containing organic–inorganic pentablock copolymer by ATRP of styrene and vinyl acetate using polydimethylsiloxane/cyclodextrin inclusion complexes as macroinitiator

Organic–inorganic pentablock copolymers have been synthesized via atom transfer radical polymerization (ATRP) of styrene (St) and vinyl acetate (VAc) monomers at 60 °C using CuCl/N,N,N′,N″,N″-pentamethyldiethylenetriamine as a catalyst system initiated from boromoalkyl-terminated poly(dimethylsiloxane) (PDMS)/cyclodextrins macroinitiator (Br-PDMS/γ-CD). Br-PDMS-Br was reacted with γ-CD in different conditions with inclusion complexes being characterized through hydrogen nuclear magnetic resonance (¹H NMR) and differential scanning calorimetry (DSC). Resulting Br-PDMS-Br/γ-CD inclusion complexes were taken as macroinitiators for ATRP of St and VAc. Well-defined poly(styrene)-b-poly(vinyl acetate)-b-poly(dimethylsiloxane/γ-cyclodextrin)-b-poly(vinyl acetate)-b-poly(styrene) (PSt-b-PVAc-b-PDMS/γ-CD-b-PVAc-b-PSt) pentablock copolymer was characterized by ¹H NMR, gel permeation chromatograph (GPC) and DSC. There was a good agreement between the number-average molecular weight calculated from ¹H NMR spectra and that of theoretically calculated. Pentablock copolymers consisting of Br-PDMS-Br/γ-CD inclusion complex as central blocks (inorganic block) and PVAc and PSt as terminal blocks were synthesized by this technique. PSt-b-PVAc-b-PDMS/γ-CD-b-PVAc-b-PSt pentablock copolymer can undergo a temperature-induced reversible transition upon heating of the copolymer complex from white complex at 22 °C to green complex in 55 °C which characterized with XRD and ¹H NMR. XRD showed a change in crystallinity percent of St peak with changing the temperature which calculated by Origin75 software.     

Inclusion complexation of 4,4′-dihydroxybenzophenone and 4-hydroxybenzophenone with α- and β-cyclodextrins

The inclusion complexation behaviours of 4,4′-dihydroxybenzophenone (DHBP) and 4-hydroxybenzophenone (HBP) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) were investigated using UV–visible fluorescence, time-resolved fluorescence, molecular modelling, scanning electron microscopy (SEM), FTIR, differential scanning calorimeter, X-ray diffraction, ¹H NMR and molecular modelling techniques. In both molecules, biexponential decay was observed in water, whereas triexponential decay was observed in the CD medium. The DSC thermogram of the DHBP/α-CD and DHBP/β-CD inclusion complex nanomaterials shows the endothermic peak at 60.8, 101.9, 119.6 and 112.8°C. The upfield chemical shift observed for HBP protons reveal that the phenyl ring (without hydroxyl substitution) entered the CD cavity and the hydroxyl group of HBP is exposed outside the CD cavity. The SEM image of DHBP appears as needle-shaped crystals on the micrometre scale, whereas the irregular bar shape was observed for HBP. Transmission electron microscopy images show that both guest molecules formed nano vesicles with α-CD and formed nano rods with β-CD.     

Inclusion complexes with cyclodextrin and usnic acid

Molecular inclusion complexes of usnic acid (UA) with β-cyclodextrin (β-CD) and 2-hydroxypropyl β-cyclodextrin (HP β-CD) were prepared by the co-precipitation method in the solid state in the molar ratio of 1:1. Structural complexes characterization was based on different methods, FTIR, ¹H NMR, XRD and DSC. Parallel to the complex by the above methods, corresponding physical mixtures of UA with cyclodextrins and complexing agents (β-CD, HP β-CD and UA) were analyzed. The results of DSC analysis showed that, at around 200 °C, the endothermal peak in the complexes with cyclodextrins originating from the UA melting has disappeared. Complex diffractogram patterns do not contain peaks characteristic for the pure UA. They are more appropriate to cyclodextrin diffractogram. This fact points to the molecular encapsulation of UA in the cyclodextrin cavity. Chemical shifts in ¹H NMR spectra after the inclusion of UA into the cyclodextrin cavity, especially H-3 protons (0.0012 and 0.0102 ppm in the β-CD and HP β-CD, respectively) and H-5 and H-6 (0.0134 ppm) and hydrogen from CH₃ (0.0073 ppm) HP β-CD also points to the formation of molecular inclusion complexes. The improved solubility of UA in water was achieved by molecular incapsulation. In the complex with β-CD the solubility is 0.3 mg/cm³, with HP β-CD 4.2 mg/cm³ while the uncomplexed UA solubility is 0.06 mg/cm³. The microbial activity of UA and both complexes was tested against eight bacteria and two fungi and during the test no reduced activity of UA in the complexes was observed.     

Spectroscopic study and antioxidant activity of the inclusion complexes of cyclodextrins and amlodipine besylate drug

The aim of the study was to synthesize and characterization the inclusion complexes of amlodipine besylate (AML) drug with β-cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) which has antioxidating activity property. The guest/host interaction of AML with β-CD and γ-CD in order to complexation drug in β-CD and γ-CD were investigated. The interaction inclusion complexes was characterized by fourier transform infrared and ultraviolet–visible spectroscopies. The formation constant was calculated by using a modified Benesi–Hildebrand equation at 25 °C. The stoichiometry of inclusion complexes was found to be 1:1 for β-CD and γ-CD with AML drug. The antioxidant activity of AML drug and its inclusion complexes were determined by the scavenging of stable radical 2,2′-diphenyl-1-picrylhydrazyl (DPPH^·). Kinetic studies of DPPH^· with AML and CDs complexes were done. The experimental results confirmed the forming of AML complexes with CDs also these indicated that the AML/β-CD and AML/γ-CD inclusion complexes was the most reactive than its free form into antioxidant activity.     

Naproxen: Hydroxypropyl-β-Cyclodextrin:Polyvinylpyrrolidone Ternary Complex Formation

The aim of the present study was to investigate the effect of the presence of thewater-soluble polymer polyvinylpyrrolidone (PVP) MW = 24000 g/mol, on thecomplexation of the phototoxic anti-inflammatory drug naproxen, in its sodiumsalt form, with hydroxypropil-β-cyclodextrin (HP-β-CD). The datashown that the polymer interacts with the free naproxen and with thenaproxen:HP-β-CD inclusion complex. The presence of different proportions of PVP, in the 0–1%(w/w) rangesystematically increased the K_app of the naproxen:HP-β-CD inclusioncomplex formation. The cause of this increase is that the polymer interactswith the HP-β-CD with a binding constant of K₂ = 29000 ± 53 M^-1; and with the naproxen:HP-β-CD inclusion complex, to givea ternary complex naproxen:HP-β-CD:PVP. The binding constant of thisprocess was K₃ = 5350 ± 1 M^-1. NMR data revealed that in the ternary system, PVP is outside of the cyclodextrin, and therefore must be wholly or partially recovering the naproxen:HP-β-CD inclusion complex.     

Effect of hydroxypropyl-β-cyclodextrin complexation on the aqueous solubility, structure, thermal stability, antioxidant activity, and tyrosinase inhibition of paeonol

The objective of this paper is to study the effect of hydroxypropyl-β-cyclodextrin (HP-β-CD) complexation on the aqueous solubility, structure, thermal stability, antioxidant activity, and tyrosinase inhibition of paeonol (PAE). The inclusion complex (PAE-HP-β-CD complex) of HP-β-CD and PAE was prepared by a freeze-drying method. Phase solubility tests showed that the stability constant of the inclusion complex was about 33.8?M^?1 at 25?°C. The experimental results of proton nuclear magnetic resonance (H-NMR) spectroscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) suggested that PAE was included by HP-β-CD to form the PAE-HP-β-CD complex. Furthermore, the thermogravimetric analysis (TGA) results showed that the thermal stability of PAE was improved when it was complexed with HP-β-CD. Comparing the antioxidant activity of PAE with that of the PAE-HP-β-CD complex at the same concentration revealed that the complex of PAE with HP-β-CD was better able to eliminate radical. Furthermore, the experimental results revealed that the formation of a complex with HP-β-CD increased the water solubility of PAE, improving its apparent inhibitive activity of tyrosinase.     

Solid-state NMR and wide-angle X-ray diffraction study of hydrofluoroether/β-cyclodextrin inclusion complex

An inclusion complex (IC) composed of a hydrofluoroether (HFE) guest and a β-cyclodextrin (β-CD) host was newly prepared, and the crystalline structure and the thermal stability of the IC were examined using several analytical methods, including wide-angle X-ray diffraction (WAXD), solid-state NMR, thermogravimetric analysis (TGA), TG–mass spectrometry (TG–MS), and quantum chemical calculation. The WAXD patterns and elemental analysis identified that the IC of an HFE/β-CD form of a channel-type structure, in which one HFE molecule is included in a common cavity of two β-CD molecules. TGA and TG–MS analysis indicated that the HFE molecules included in β-CD are hardly evaporated or degraded up to the decomposition temperature of the β-CD host. Solid-state ¹³C NMR indicated that the β-CD ring structure was deformed by including an HFE molecule in it, and that the ¹⁹F NMR signals of the HFE guest were significantly shifted to higher frequencies by the inclusion due to the dielectric media effect in the cavity of β-CD. Moreover, the ¹⁹F NMR signals of HFE included in IC were further shifted after annealing at 150 °C, which reflected structural changes in HFE/β-CD IC caused at elevated temperatures. The WAXD patterns also confirmed that the packing structure along the crystalline b-direction of HFE/β-CDs, which penetrates the cavities of β-CDs, was compressed by annealing and transformed to a more stable structure.     

Study on preparation and inclusion behavior of inclusion complexes between β-cyclodextrin derivatives with benzophenone

In the paper, the two chemically modified β-cyclodextrin derivatives of 4,4´-diaminodiphenyl ether-bridged-bis-β-cyclodextrins (ODA-bis-β-CD) and p-aminobenzenesulfonic acid-β-cyclodextrin (ABS-β-CD) were synthesized, and then these two β-cyclodextrin derivatives were respectively formed into inclusion complexes with benzophenone (BP) by co-precipitation method. The structure of the inclusion complexes were characterized by UV/vis spectroscopy, FT-IR spectroscopy, elemental analysis, ¹H NMR spectroscopy and XRD. Spectral titration was performed to study the inclusion behavior of the inclusion complexes. These experiments indicated that two inclusion complexes were formed at a stoichiometric ratio of 1:1 and the inclusion stability constants at different temperatures were calculated using the Benesi–Hildebrand (B–H) equation. The thermodynamic parameters (ΔG°, ΔH°, ΔS°) were obtained. As a result, it was found that the two chemically modified β-cyclodextrins containing BP were exothermic and spontaneous process (ΔG°?<?0), and the processes of inclusion complexation were mainly enthalpy driven with negative or minor negative entropic contribution.     

Study on the inclusion compound of β-cyclodextrin with (η5-cyclopentadienyl)tricarbonylmanganese(0)

The supramolecular inclusion compound of β-cyclodextrin (β-CD, host) with (η5-cyclopentadienyl)tricarbonylmanganese [MnCp(CO)3, guest] was obtained in a crystalline state. The host-guest compound is thermally stable and do not liberate the guest on heating at 100$ in vacuum. It was characteried by elemental analysis,1H NMR, differential scanning thermal (DSC) analysis and TLC. Continueous variation plot by NMR method shows that β-CD formed 1:1 inclusion compound with MnCp(CO)3. On the basis of 1H NMR spectra and the model building with Corey Pauling Koltum (CPK) models, the most probable inclusion mode is proposed.     

Synthesis of conjugates of β-cyclodextrin with polyamidoamine dendrimers and their molecular inclusion interaction with levofloxacin lactate

Polyamidoamine (PAMAM) dendrimers of different generations (G2 and G4) conjugated with β-cyclodextrin (β-CD), PAMAM (G2, G4)-CD, were synthesized using substitution reaction from mono-6-iodine-β-cyclodextrin and PAMAM dendrimers. The resulting molecular structures were characterized by NMR, IR. The molecular interaction between various dendrimers and levofloxacin lactate (LFL) were investigated by monitoring the fluorescence of LFL in the presence of dendrimers in buffer solution (pH 7.4) at 25?°C. It was found that the PAMAM (G2, G4)-CD possesses higher sensitizing ability than that of the corresponding parent dendrimers and natural β-CD, and increases concomitantly with the increases of generation and content of β-CD, suggesting that the PAMAM (G2, G4)-CD possesses stronger inclusion ability with LFL. The possible interaction mechanism between PAMAM-CD and LFL was proposed by ¹H NMR analysis and theoretical calculation. The results show that the LFL molecule is located at the amine end of dendrimer molecule and along the side of cyclodextrin cavities to form supramolecular complexes. Furthermore, results indicate that the main driving force of the complex could be attributed to the electrostatic interactions and hydrogen bonding between LFL and PAMAM-CD, as well as the synergistic effect of intermolecular forces.     

Inclusion complexation of a novel diaminodiphenyl disulphide bridged bis(β-cyclodextrin) with bile salts

A novel 4,4′-diaminodiphenyl disulphide bridged bis(β-cyclodextrin) (β-CD) 2 was synthesised, and its inclusion complexation behaviour with bile salts, i.e. cholate (CA), deoxycholate (DCA), glycocholate (GCA) and taurocholate (TCA) have been determined in phosphate buffer (pH 7.20) at 25°C by the fluorescence and 2D NMR spectroscopy. The stoichiometry of resulting inclusion complexes between bis(β-CD) 2 and bile salts was demonstrated, showing 1?:?1 binding model upon all inclusion complexation. The structures of the inclusion complexes between bile salts and bis(β-CD) 2 were elucidated by 2D NMR experiments, indicating that the D-ring and side-chain of bile salts, penetrate into one CD cavity of 2 from the wide opening deeply, while the phenyl moiety of the CD linker is partially self-included in the other CD cavity to form host-linker-guest binding mode. As compared with the native β-CD 1 upon complexation with bile salts, the bis(β-CD) 2 enhances the binding ability and molecular selectivity.     

Complex Formation of Hematoporphyrin with Cyclodextrins and 1,1′-Diheptyl-4,4′-bipyridinium Dibromide in Aqueous Solutions

At around 5×10^-6?mol?dm^-3 of hematoporphyrin (HP), an HP dimer exists as well as an HP monomer. The equilibrium constant for the dimerization of HP in pH 10.0 buffer has been evaluated to be 1.70×10⁵?mol^-1?dm³ from the HP concentration dependence of the absorption spectrum. In aqueous solution, HP forms 1:1 inclusion complexes with β-cyclodextrin (β-CD), γ-cyclodextrin (γ-CD), and heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD). The fluorescence of HP is significantly enhanced by the addition of CDs. From simulations of the fluorescence intensity changes, the equilibrium constants for the formation of the CD–HP inclusion complexes have been estimated to be 200, 95.7, and 938?mol^-1?dm³ for β-CD, γ-CD, and TM-β-CD, respectively. HP forms a 1:1 complex with 1,1′-diheptyl-4,4′-bipyridinium dibromide (DHB) in aqueous solution. In contrast to the addition of CDs, the HP fluorescence is significantly quenched by the addition of DHB. The equilibrium constant for the formation of the HP–DHB complex has been evaluated to be 1.98×10⁵?mol^-1?dm³ from the fluorescence intensity change of HP. The addition of DHB to an HP solution containing β-CD induces a circular dichroism signal of negative sign, indicating the formation of a ternary inclusion complex involving β-CD, HP, and DHB. In contrast, there is no evidence for the formation of a ternary inclusion complex of HP with DHB and TM-β-CD.     

Characterization of the inclusion complex of β-cyclodextrin with sorbic acid in the solid state and in aqueous solution

Crystal structure of β-cyclodextrin (β-CD) complexes with sorbic acid, usually as food preservative, has been determined by single-crystal X-ray diffraction at 113 K. The space group of β-cyclodextrin-sorbic acid complex is P1 with unit cell dimensions of a = 15.284(3) Å, b = 15.402(3) Å, c = 17.981(4) Å, α = 99.67(3)°, β = 112.83(3)°, γ = 102.48(3)° and Z = 1. The result indicates that the β-CD molecules form head-to-head dimers which pack in the intermediate mode. Each dimer contains two guest molecules whose methyl groups are located at the dimer interface while the carboxyl groups protrude from the β-CD primary faces. Water molecules (25.5) are distributed outside the cyclodextrin cavity over 31 sites. Furthermore, nuclear magnetic resonance spectroscopy (¹H NMR) has been employed to investigate the inclusion behavior between the host β-CD and guest sorbic acid in aqueous solution. The results obtained enabled us to structurally characterize the β-CD inclusion complex with sorbic acid.     

Inclusion of α-lipoic acid in β-cyclodextrin. Physical–chemical and structural characterization

The inclusion of α-lipoic acid (LA) in β-cyclodextrin (β-CD) by increasing the aqueous solubility and photostability can enhance its medicinal use in the oral administration. Different preparation methods were employed to obtain an α-lipoic acid-β-cyclodextrin (LA-β-CD) inclusion complex and to determine the physical–chemical characteristics and the interactions present in this compound. The formation of the solid inclusion compound was confirmed by X-ray powder diffraction, differential scanning calorimetry (DSC) and infrared spectroscopy (FTIR). FTIR and DSC data confirm the new obtained compound. The crystalline structure of this compound belongs to the monoclinic system with four molecules in the unit cell. ¹H NMR spectroscopic method was employed to study the inclusion process in aqueous solution. Job plots derived from the ¹H NMR spectral data demonstrated an 1:1 stoichiometry of the inclusion complex in liquid state. 2D NMR data suggest the orientation of LA with the carboxyl group near to narrower rim of the β-CD.     

Study on the Supramolecular System of TAPP and Cyclodextrins by Spectroscopy

The ability of β-cyclodextrin (β-CD), γ-CD, hydroxypropyl-β-CD (HP-β-CD), trimethyl-β-CD (TM-β-CD), sulfurbutylether-β-CD (SBE-β-CD) and carboxymethyl-β-cyclodextrin (CM-β-CD) to break the aggregate of the meso-tetrakis(4-N-trimethylaminobenzyl)porphyrin (TAPP) and to form 2:1 inclusion complexes has been studied by absorption and fluorescence spectroscopy. The formation constants are calculated, respectively, by fluorimetry, from which the inclusion capacity of different CDs is compared and the inclusion mechanism of charged-β-CD (SBE-β-CD and CM-β-CD) is quite different from that of the parent β-CD. At lower pH, the complexation between TM-β-CD and H²TAPP²⁺ (the form of the diprotonated TAPP) hampers the continuous protonation of the pyrrole nitrogen of TAPP and the hydrophobic cavity may prefer to bind an apolar neutral porphyrin molecule. ¹HNMR data support the inclusion conformation of the porphyrin–cyclodextrin supramolecular system, indicating the interaction of the meso-phenyl groups of TAPP with the cavity of CDs. For this host–guest inclusion model, cyclodextrin being regarded as the protein component, which acts as a carrier enveloping the active site of heme prosthetic group within its hydrophobic environment, provides a protective sheath for the porphyrin, creating artificial analogues of heme-containing proteins. However, for TAPP, encapsulated within this saccharide-coated barrier, its photophysical and photochemical properties changed strongly.     

Synthesis, characterization and antitumor activity of 1,2-disubstituted ferrocenes and cyclodextrin inclusion complexes

Seven different ferrocene derivatives have been tested in vitro against Ehrlich ascites tumor cells. Neither ferrocene nor the monosubstituted derivative N,N-dimethylaminomethylferrocene showed cytotoxic activity (IC₅₀ > 1000 μM for 3 h treatments). Better results were obtained with 1,2-disubstituted derivatives. The IC₅₀ values ranged from 376.6 μM for 1,2-diformylferrocene to 71.2 μM for racemic 2-(N,N-dimethylaminomethyl)ferrocenecarboxamide. The latter derivative was also encapsulated in native β-cyclodextrin (CD), heptakis-2,3,6-tri-O-methyl-β-CD (TRIMEB) and 2-hydroxypropyl-β-CD (HPβCD) to give 1:1 (host:guest) inclusion compounds. The existence of true inclusion complexes in the solid state was confirmed by a combination of powder X-ray diffraction, thermogravimetric analysis, FTIR and ¹³C CP MAS NMR spectroscopy. The IC₅₀ value for the β-CD inclusion compound was identical to that obtained for the nonincluded ferrocene derivative. By contrast, the inclusion compounds comprising TRIMEB and HPβCD yielded IC₅₀ values of 25.2 and 20.0 μM, respectively. No obvious relationship could be established between the redox behavior of the compounds determined by cyclic voltammetry and the biochemical data.