First solid-state NMR spectroscopy evaluation of complexes of benznidazole with cyclodextrin derivatives

Coumarin/β-Cyclodextrin Inclusion Complexes Promote Acceleration and Improvement of Wound Healing

Coumarins have great pharmacotherapeutic potential, presenting several biological and pharmaceutical applications, like antibiotic, fungicidal, anti-inflammatory, anticancer, anti-HIV, and healing activities, among others. These molecules are practically insoluble in water, and for biological applications, it became necessary to complex them with cyclodextrins (CDs), which influence their bioavailability in the target organism. In this work, we studied two coumarins, and it was possible to conclude that there were structural differences between 4,7-dimethyl-2H-chromen-2-one (DMC) and 7-methoxy-4-methyl-2H-chromen-2-one (MMC)/β-CD that were solubilized in ethanol, frozen, and lyophilized (FL) and the mechanical mixtures (MM). In addition, the inclusion complex formation improved the solubility of DMC and MMC in an aqueous medium. According to the data, the inclusion complexes were formed and are more stable at a molar ratio of 2:1 coumarin/β-CD, and hydrogen bonds along with π-π stacking interactions are responsible for the better stability, especially for (MMC)2@β-CD. In vivo wound healing studies in mice showed faster re-epithelialization and the best deposition of collagen with the (DMC)2@β-CD (FL) and (MMC)2@β-CD (FL) inclusion complexes, demonstrating clearly that they have potential in wound repair. Therefore, (DMC)2@β-CD (FL) deserves great attention because it presented excellent results, reducing the granulation tissue and mast cell density and improving collagen remodeling. Finally, the protein binding studies suggested that the anti-inflammatory activities might exert their biological function through the inhibition of MEK, providing the possibility of development of new MEK inhibitors.

Click nanosponge - A novel amine-rich β-cyclodextrin-based crosslinked polymer for heterogeneous catalysis

Cyclodextrin-based nanosponges are promising materials for heterogeneous catalysis due to their inherent synthetic versatility, tunable porosity and nontoxicity. In this work, a primary amine-rich β-cyclodextrin nanosponge was synthesized via click imine condensation reaction between 1,6-hexamethylamine-functionalized β-cyclodextrin (CDAM) and glutaraldehyde (GLT) to afford CDGLAM, in mild conditions. The crosslinked polymer exhibited a BET surface area of 36.39 m2 g-1, an average pore diameter of 3.09 nm (as assessed by the BJH method), and thermal stability up to 253 °C. CDGLAM was tested as heterogeneous catalyst for the metal-free Henry and Knoevenagel reactions, between aromatic aldehydes and nitromethane or ethyl cyanoacetate, respectively, affording the products in moderate to very high yields. These results show the ease of preparation of β-CD-based nanosponges from a green chemistry perspective, as well as their potential for future use in catalytic systems.

A Review of Applications of Solid-State Nuclear Magnetic Resonance (ssNMR) for the Analysis of Cyclodextrin-Including Systems

Cyclodextrins, cyclic oligosaccharides composed of five or more α-D-glucopyranoside units linked by α-1,4 glycosidic bonds, are widely used both in their native forms as well as the components of more sophisticated materials. Over the last 30 years, solid-state nuclear magnetic resonance (ssNMR) has been used to characterize cyclodextrins (CDs) and CD-including systems, such as host-guest complexes or even more sophisticated macromolecules. In this review, the examples of such studies have been gathered and discussed. Due to the variety of possible ssNMR experiments, the most common approaches have been presented to provide the overview of the strategies employed to characterize those useful materials.

Circularly polarised luminescence from excimer emission of anthracene derivatives complexed with γ-cyclodextrin in the solid state

In this study, we report circularly polarised luminescence (CPL)-active molecules that exhibit high fluorescence quantum yields in the solid state. We developed anthracene derivatives with substituents at the 9 and 10 positions, such as ethyl(anthracene-9-carbonyl)glycinate (9AnGlyEt), N-butylanthracene-9-carboxamide (9AnB), N-benzylanthracene-9-carboxamide (9AnPh), and N ⁹,N ¹⁰-dibutylanthracene-9,10-dicarboxamide (9,10AnB). These compounds were complexed with γ-cyclodextrin (γ-CD) in the solid state by grinding, and the fluorescence properties of the resulting γ-CD complexes were investigated. The fluorescence quantum yields were enhanced after γ-CD complexation. Among the prepared γ-CD complexes, 9AnGlyEt/γ-CD had the highest fluorescence quantum yield (Φ _f = 0.35), which was enhanced up to 5.8 times after γ-CD complexation. This was probably due to the interaction between the two anthracene molecules in the γ-CD cavity, which prevented fluorescence quenching caused by aggregation of the compounds. Positive CPL of g _CPL = 1.3 × 10^-3 was observed for 9AnGlyEt/γ-CD based on its excimer emission.

Effect of mechanochemical inclusion of triamterene into sulfobutylether-β-cyclodextrin and its improved dissolution behavior

The formation of inclusion complexes between triamterene (TT) and cyclodextrins (CDs) to increase the water apparent solubility of TT was investigated. UV data showed that the binding constant of the TT/sulfobutylether-β-cyclodextrin (SBE-β-CD) inclusion complex was 510 L/mol. The phenyl ring of TT was inserted into the secondary hydroxy face of SBE-β-CD, as demonstrated by ¹H-¹H rotating frame nuclear Overhauser effect spectroscopy NMR. Physicochemical properties of solid TT/SBE-β-CD complexes prepared by physical mixing, kneading, freeze-drying, and mechanochemical methods were studied by X-ray diffraction and ¹³C cross-polarization and magic angle spinning NMR. With the mechanochemical method, the diffraction peak corresponding to TT disappeared, indicating the formation of an inclusion complex. The results of the dissolution test revealed that the solid complex obtained by the mechanochemical method improved the dissolution of TT. The water apparent solubility of TT can be improved by simple mechanical mixing without organic solvents, and improved bioavailability after oral administration is expected.

Applications of NMR in Drug:Cyclodextrin Complexes

NMR spectroscopy is an effective technique, applicable for studying bioactive materials or drug delivery systems in order to obtain comprehensive details related to structural and dynamic characteristics at atomic resolution. The applications of NMR spectroscopy have been increased considerably as a result of the combination of advancement in technological NMR instrumentation and scientific knowledge. This chapter is dedicated to highlight the applications of NMR spectroscopy in drug:cyclodextrin complexes using both liquid- and solid-state NMR spectroscopy.

Physicochemical characterization and in vitro biological evaluation of solid compounds from furazolidone-based cyclodextrins for use as leishmanicidal agents

The discovery of new drugs and dosage forms for the treatment of neglected tropical diseases, such as human and animal leishmaniasis, is gaining interest in the chemical, biological, pharmaceutical, and medical fields. Many pharmaceutical companies are exploring the use of old drugs to establishing new drug dosage forms and drug delivery systems, in particular for use in neglected diseases. The formation of complexes with cyclodextrins is widely used to improve the stability, solubility, and bioavailability of pharmaceutical drugs, as well as reduce both the toxicity and side effects of many of these drugs. The aim of this study was to characterize solid compounds obtained from the association between furazolidone (FZD) and β-cyclodextrin (β-CD) or hydroxypropyl-β-cyclodextrin (HP-β-CD). The solid compounds were prepared in molar ratios of 1:1 and 1:2 (drug:CD) by kneading and lyophilization. Molecular docking was used to predict the preferred relative orientation of FZD when bound in both studied cyclodextrins. The resulting solid compounds were qualitatively characterized by scanning electron microscopy (SEM), thermal analysis (DSC and TG/DTG), X-ray diffraction (XRD), Raman spectroscopy with image mapping (Raman mapping), and ¹³C nuclear magnetic resonance spectroscopy (¹³C NMR) in the solid state. The cytotoxicity of the compounds against THP-1 macrophages and the 50% growth inhibition (IC₅₀) against Leishmania amazonensis promastigote forms were subsequently investigated using in vitro techniques. For all of the solid compounds obtained, the existence of an association between FZD and CD were confirmed by one or more characterization techniques (TG/DTG, DSC, SEM, XRD, RAMAN, and ¹³C NMR), particularly by a significant decrease in the crystallinity of these materials and a reduction in the melting enthalpy associated with furazolidone thermal events. The formation of more effective interactions occurred in the compounds prepared by lyophilization, in a 1:2 molar ratio of the two CDs studied. However, the formation of an inclusion complex was confirmed only for the solid compound obtained from HP-β-CD prepared by lyophilization (LHFZD1:2). The absence of cytotoxicity on the THP-1 macrophage lineages and the leishmanicidal activity were confirmed for all compounds. MHFZD1:2 and LHFZD1:2 were found to be very active against promastigote forms of L. amazonensis, while all others were considered only active. These results are in line with the literature, demonstrating the existence of biological activity for associations between drugs and CDs in the form of complexes and non-complexes. All solid compounds obtained were found to be promising for use as leishmanicidal agents against promastigote forms of L. amazonensis.

Tailoring microstructural, drug release properties, and antichagasic efficacy of biocompatible oil-in-water benznidazol-loaded nanoemulsions

This study explored the transition of lamellar-type liquid crystal (LLC) to biocompatible oil-in-water nanoemulsions able to modify benznidazole (BNZ) release and target the drug to cells infected with the T. cruzi parasite. Three cosolvents (2methylpyrrolidone [NMP], polyethylene glycol [POL], and propylene glycol [PRO] were tested to induce the transition of anisotropic LLC systems to isotropic nanoemulsions. Mixtures of soy phosphatidylcholine with sodium oleate stabilized the dispersions of medium chain triglyceride in water. Rheological measurements, polarized microscopy, and small angle X-ray scattering demonstrated that there is a phase transition from LLC to desired nanoemulsions. These small and narrow droplet-sized nanocarriers exhibited some advantages and promising features, such as the enhanced BNZ aqueous solubility and slow drug release rate. In vitro cell biocompatibility of formulations was assessed in the Vero E6 and SiHa cell lines. Drug-loaded nanoemulsions inhibited the epimastigote growth of the T. cruzi parasite (IC50 0.208 ± 0.052 μg mL^-1) and reduced its infective life form trypomastigote (IC50 0.392 ± 0.107 μg mL^-1). The oil-in-water nanoemulsions were demonstrated as promising biocompatible liquid drug delivery systems capable of improving the BNZ trypanocidal activity for the treatment of Chagas disease.