Cyclodextrin, an efficient tool for trans-anethole encapsulation: Chromatographic, spectroscopic, thermal and structural studies

An alternative cyclodextrin based formulation for oral anticancer drug exemestane: In vitro and cell culture studies

Background: Unknown influence of cyclodextrin on the properties of the film formulation aimed for buccal application. Aim: Development and characterization of a novel bioadhesive film formulation for buccal atenolol delivery containing drug/cyclodextrin inclusion. Method: Interaction between atenolol and randomly methylated β-cyclodextrin (RAMEB) in solution was studied by phase solubility studies. The complex in solid state was prepared by the freeze-drying method and characterized by differential scanning calorimetry and Fourier-transformed infrared spectroscopy (FTIR). The drug, free or in complex form, was incorporated into polymeric films prepared by the casting method using ethylcellulose (EC), polyvinyl alcohol (PVA), and hydroxypropyl methylcellulose (HPMC). The prepared film formulations were characterized in terms of swelling, bioadhesion, and in vitro drug release. Results: The formation of a stabile inclusion complex (Ks = 783.4 ± 21.6 M−1) in 1:1 molar stoichiometry was confirmed in solution and in solid state. The swelling properties of films were predominated by the type of polymer used in the formulation. In vitro bioadhesive properties of the films were well correlated with the swelling properties of the polymers used in the formulation. Although incorporation of the drug, free or in complex form, decreased the bioadhesion of the films, PVA- and HPMC-based formulations retained suitable bioadhesive properties. Higher atenolol solubility upon complexation with RAMEB increased the drug dissolution rate under conditions designed to be similar to those on the buccal mucosa, but it has decreased the drug release rate from the PVA and HPMC film formulation, leading to a sustained drug release pattern. In the case of EC-based films, RAMEB promoted drug release. Other parameters that influenced the drug release rate were associated with the structure of the polymer used in the formulation, swelling characteristics of the films, and the interaction between atenolol and hydrophilic polymers that was demonstrated by FTIR analysis. Conclusion: Incorporation of atenolol in the form of an inclusion complex into hydrophilic films may be an appropriate strategy to prepare a suitable formulation for buccal drug delivery.

This study aimed to investigate the effect of hydroxypropyl methylcellulose on the complexation of fenofibrate and hydroxypropyl-β-cyclodextrin (HP-β-CD). Initially, phase solubility studies with an excess amount of drug in the HP-β-CD solutions with and without hydroxypropyl methylcellulose (HPMC) were investigated. Both of the binary and ternary complexes were prepared by ball-milling. The complexes were characterized by Fourier transform infrared spectroscopy (FI-IR), X-ray powder diffraction (XPRD), differential scanning calorimetry (DSC) and nuclear magnetic resonance spectroscopy (1H-NMR). The AL type phase-solubility diagram revealed that the complexes of fenofibrate and HP-β-CD were formed with molecular ratio of 1:1. The results of FT-IR, XPRD, DSC and 1H NMR analysis show the formulation of inclusion complexes. In conclusion, the interaction occurrs between fenofibrate and HP-β-CD in the complexes, and the existence of HPMC effectively improves the complexation efficiency and stability constant. The in vitro dissolution test suggests ternary complex is superior to binary complex in terms of the release of fenofibrate.

The study was designed to investigate the effect of cyclodextrins (CDs) on the solubility, dissolution rate, and bioavailability of cilostazol by forming inclusion complexes. Natural CDs like beta-CD, gamma-CD, and the hydrophilic beta-CD derivatives, DM-beta-CD and HP-beta-CD, were used to prepare inclusion complexes with cilostazol. Phase solubility study was carried out and the stability constants were calculated assuming a 1:1 stoichiometry. Solid cilostazol complexes were prepared by coprecipitation and kneading methods and compared with physical mixtures of cilostazol and cyclodextrins. Prepared inclusion complexes were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) studies. In vitro dissolution study was performed using phosphate buffer pH 6.4, distilled water, and HCl buffer pH 1.2 as dissolution medium. The optimized inclusion complex was studied for its bioavailability in rabbit and the results were compared with those of pure cilostazol and Pletoz-50. Phase solubility study showed dramatic improvement in the solubility of drug by formation of complexes, which was further increased by pH adjustment. The dissolution rate of cilostazol was markedly augmented by the complexation with DM-beta-CD. DSC and XRD curves showed sharp endothermic peaks indicating the reduction in the microcrystallinity of cilostazol. Selected inclusion complex was also stable at ambient temperature up to 6 months. The in vivo study revealed that DM-beta-CD increased the bioavailability of cilostazol with low variability in the absorption. Among all cilostazol-cyclodextrins complexes, cilostazol-DM-beta-CD inclusion complex (1:3) prepared by coprecipitation method showed 1.53-fold and 4.11-fold increase in absorption along with 2.1-fold and 2.97-fold increase in dissolution rate in comparison with Pletoz-50 and pure cilostazol, respectively.

Background: Stigmasterol possesses numerous physiological effects and is used as food supplements and behaves as a pharmaceutical agent. It exhibits anticancer effects against various cancers. The usefulness of the stigmasterol is restricted due to its poor solubility. To overcome this and enhance the solubility and bioavailability of this phytosterol, molecular encapsulation is utilized to augment the desirable properties of stigmasterol. This research work aims to investigate the interaction between stigmasterol and alpha-cyclodextrin (α-CD) in aqueous solution as well as in solid state and experimentally examined by spectral techniques. Methods: The liquid complexes are characterized by ultraviolet (UV)-visible spectroscopy and solid inclusion complexes are characterized by Fourier transformer infrared resonance and 1H nuclear magnetic resonance spectroscopy. The thermal behavior of the complex is analyzed by differential scanning calorimeter. Phase solubility studies are done to learn the solubility of the newly synthesized complex. Results: Formation constant from UV-visible analysis is found to be 569 M−1 by Benesi–Hildebrand equation. The solubility constant is calculated to be 52 M−1. The results obtained prove the inclusion which is confirmed through molecular docking studies. Conclusion: The newly synthesized inclusion complex is a potent pharmaceutical agent in drug formulation as stigmasterol solubility is enhanced when included in the cavity of α-CD.

To study the effect of β-cyclodextrin (βCD) inclusion complex on the bioavailability of clotrimazole from poloxamer-based suppository, formulations composed of P 188, propylene glycol and different molar ratio of clotrimazole-βCD inclusion complex were prepared. Clotrimazole (1%) has been formulated in a suppository using the thermo sensitive polymer P188 (70%) together with propylene glycol (30%). To increase its aqueous solubility, clotrimazole was incorporated as its inclusion complex at various molar ratios with βCD (1:0.25, 1:0.5, 1:1, and 1:2). The inclusion complex was characterized by differential scanning calorimetry (DSC), XRD and phase solubility studies. It was observed that the complexation with βCD, particularly at high molar ratio (F3 (1:1) and F4 (1:2)) decreased the release profile of clotrimazole considerably. However, suppositories containing inclusion complex at low molar ratio (F1 (1:0.25) and F2 (1:0.5)) showed excellent release profile compared to control formulation. In vivo study in rats at 15 mg/Kg dose showed that the F1 and F2 (82.39 ± 15.40 and 67.05 ± 8.79, respectively) significantly increased the AUC compared to that of F3 (41.48 ± 11.51), F4 (23.34 ± 8.37) and control (46.7 ± 7.87) suppositories. Thus, the suppositories containing inclusion complexes prepared at low drug to βCD molar ratio (F1) could be a potential suppository formulation to increase the bioavailability of hydrophobic drugs such as clotrimazole.

Cyclodextrins possess the ability to increase the apparent solubility and dissolution rate of poorly water soluble drugs. The objectives of the study were to investigate the effect of β-cyclodextrin, hydroxypropyl-β-cyclodextrin and sulfobutyl ether7 β-cyclodextrin on solubility and dissolution rate of docetaxel. Four different methods (physical mixture, kneading, freeze drying and solvent evaporation) were employed for inclusion complexation, at varying drug to cyclodextrin ratios 1:1, 1:2 and 1:4. The inclusion complexes of docetaxel with β-cyclodextrin, hydroxypropyl-β-cyclodextrin and sulfobutyl ether7 β-cyclodextrin at molar ratios 1:1 were characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and proton nuclear magnetic resonance (1H NMR). The dissolution profiles of inclusion complexes were compared with pure drug. The results revealed formation of inclusion complexes between drug and β-cyclodextrin, hydroxypropyl-β-cyclodextrin and sulfobutyl ether7 β-cyclodextrin as confirmed by FTIR. 1H NMR revealed inclusion of drug within cyclodextrin cavity with appearance of proton shifts. Drug crystallinity was reduced with physical mixing and kneading method while amorphous form was attained by freeze drying and solvent evaporation method as revealed by XRD. The DSC and TGA confirmed the formation of inclusion complexes with the absence of melting peak of drug. The effect on solubility and dissolution rate of docetaxel was greater with sulfobutyl ether7 β-cyclodextrin than hydroxypropyl-β-cyclodextrin and β-cyclodextrin when prepared with similar methods. Drug to cyclodextrin ratio 1:1 was the optimum ratio to increase the solubility and dissolution of docetaxel irrespective of the method. It is concluded that sulfobutyl ether7 β-cyclodextrin had greater effect on solubility and dissolution rate of docetaxel than β-cyclodextrin and hydroxypropyl-β-cyclodextrin at molar ratios 1:1.

Formulation of silymarin binary and ternary solid dispersions: Characterization, simulation study and cell viability assessment against lung cancer cell line

Host-guest inclusion complexes of sulfabenzamide with β- and methyl-β-cyclodextrins: Characterization, antioxidant activity and DFT calculation

Preparation and characterization of spiro-acridine derivative and 2-hydroxypropyl-β-cyclodextrin inclusion complex

SN-38, an active metabolite of irinotecan, is up to 1,000-fold more potent than irinotecan. But the clinical use of SN-38 is limited by its extreme hydrophobicity and instability at physiological pH. To enhance solubility and stability, SN-38 was complexed with different cyclodextrins (CDs), namely, sodium sulfobutylether β-cyclodextrin (SBEβCD), hydroxypropyl β-cyclodextrin, randomly methylated β-cyclodextrin, and methyl β-cyclodextrin, and their influence on SN-38 solubility, stability, and in vitro cytotoxicity was studied against ovarian cancer cell lines (A2780 and 2008). Phase solubility studies were conducted to understand the pattern of SN-38 solubilization. SN-38-βCD complexes were characterized by differential scanning calorimetry (DSC), X-ray powder diffraction analysis (XRPD), and Fourier transform infrared (FTIR). Stability of SN-38-SBEβCD complex in pH 7.4 phosphate-buffered saline was evaluated and compared against free SN-38. Phase solubility studies revealed that SN-38 solubility increased linearly as a function of CD concentration and the linearity was characteristic of an AP-type system. Aqueous solubility of SN-38 was enhanced by about 30-1,400 times by CD complexation. DSC, XRPD, and FTIR studies confirmed the formation of inclusion complexes, and stability studies revealed that cyclodextrin complexation significantly increased the hydrolytic stability of SN-38 at physiological pH 7.4. Cytotoxicity of SN-38-SBEβCD complex was significantly higher than SN-38 and irinotecan in both A2780 and 2008 cell lines. Results suggest that SBEβCD encapsulated SN-38 deep into the cavity forming stable inclusion complex and as a result increased the solubility, stability, and cytotoxicity of SN-38. It may be concluded that preparation of inclusion complexes with SBEβCD is a suitable approach to overcome the solubility and stability problems of SN-38 for future clinical applications.

Characterization of an inclusion complex of ethyl benzoate with hydroxypropyl-β-cyclodextrin

Introduction: Selexipag, a selective prostacyclin receptor (IP) agonist used in pulmonary arterial hypertension, suffers from poor aqueous solubility, limiting its oral bioavailability. Cyclodextrin complexation is a widely accepted technique to improve solubility and dissolution properties of hydrophobic drugs. This study aimed to enhance the solubility and dissolution rate of Selexipag by forming inclusion complexes with β-cyclodextrin. Methods: Inclusion complexes of Selexipag were prepared using three techniques: physical mixing, kneading, and solvent evaporation, each in 1:1 and 1:2 molar ratios with β-cyclodextrin. Phase solubility studies were performed to determine the stability constant. The prepared complexes were evaluated for drug content and in vitro dissolution using UV spectrophotometry and paddle method, USP Type II apparatus in 0.1 N HCl. Results: The phase solubility diagram exhibited an AL-type profile with a 1:1 stoichiometry and a stability constant of 164.56 M–¹. All formulations demonstrated acceptable drug content (98.3–102.2 %). Among the tested complexes, the kneading method at a 1:2 ratio (SK2) showed the highest drug release, achieving 94.2 % dissolution in 60 minutes, compared to 29.63 % for pure Selexipag. This enhancement is attributed to increased wettability, amorphization, and reduced crystallinity of the drug. Conclusion: Inclusion complexation of Selexipag with β-cyclodextrin markedly improved its solubility and dissolution rate. The kneading method with a 1:2 molar ratio proved most effective, offering a promising strategy for improving the oral delivery of poorly soluble drugs.

The therapeutic potential of acyclovir is limited by the low oral bioavailability owing to its limited aqueous solubility and low permeability. The present study was a systematic investigation on the development and evaluation of inclusion complex using hydroxypropyl-β-cyclodextrin for the enhancement of oral bioavailability of acyclovir. The inclusion complex of acyclovir was prepared by kneading method using drug: hydroxypropyl-β-cyclodextrin (1:1 mole). The prepared inclusion complex was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, NMR spectroscopy and evaluated in vitro by dissolution studies. In vivo bioavailability of acyclovir was compared for inclusion complex and physical mixture in rat model. Phase solubility studies indicate the formation of acyclovir–hydroxypropyl-β-cyclodextrin complex with higher stability constant and linear enhancement in drug solubility with increase in hydroxypropyl-β-cyclodextrin concentration. Characterization of the prepared formulation confirms the formation of acyclovir–hydroxypropyl-β-cyclodextrin inclusion complex. Dissolution profile of inclusion complex demonstrated rapid and complete release of acyclovir in 30 min with greater dissolution efficiency (90.05 ± 2.94%). In vivo pharmacokinetic data signify increased rate and extent of acyclovir absorption (relative bioavailability ∼160%; p < 0.0001) from inclusion complex, compared to physical mixture. Given the promising results in the in vivo studies, it can be concluded that the inclusion complex of acyclovir could be an effective and promising approach for successful oral therapy of acyclovir in the treatment of herpes viruses.

Objective: Diacerein (DCN) is a new anti-inflammatory analgesic and antipyretic drug developed specially for the treatment of osteoarthritis. DCN is a poorly water-soluble drug with relatively low bioavailability. Therefore, the purpose of this study was to enhance the solubility and dissolution of DCN by complexation with polyethylene glycol 6000 (PEG).Methods: Solid dispersions (SDs) of DCN were prepared in weight ratios of 60:40, 40:60, 20:80, and 5:95 by the melting method using PEG as carrier. These SDs were characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and Fourier transform infrared (FTIR) spectroscopy to ascertain whether there were any physicochemical interactions between drug and carrier that could affect dissolution. Solubility and dissolution studies were conducted with pure DCN, physical mixtures (PMs) and SDs.Results and discussion: Solubility studies indicated that PEG significantly increased the solubility of DCN in water. The Gibbs free energy (ΔGtr°) values were negative, indicating the spontaneous nature of DCN solubilization. Phase solubility studies indicated complex with a possible stoichiometry of 1:1.Conclusion: FTIR, DSC and PXRD studies indicate that there is no chemical interaction between DCN and PEG in solid state. In contrast to slow dissolution rate of pure DCN, the dispersion of drug in PEG considerably enhanced the dissolution rate. Even PMs of DCN prepared with PEG also showed better dissolution profiles compared with that of DCN, indicating the solubilization effect of PEG. Therefore, it is concluded that the preparation of SDs of DCN with PEG provides a promising way to increase its solubility and dissolution rate.