Influence of Ethanol as a Co-Solvent in Cyclodextrin Inclusion Complexation: A Molecular Dynamics Study

In Search of the Most Stable Molecular Configuration of Heptakis(2,6-O-dimethyl)-β-cyclodextrin and Its Complex with Mianserin: A Comparison of the B3LYP-GD2 and M062X-GD3 Results

Cyclodextrins are well known for their ability to form stable, highly soluble complexes with various substances, which makes them widely used as excipients in food, cosmetics, and pharmaceuticals. In this work, properties of heptakis(2,6-O-dimethyl)-β-cyclodextrin (DM-β-CD) in vacuo and in water, as well as its ability to bind the antidepressant drug mianserin (MIA) in aqueous solution, are investigated computationally. The results are shown to depend strongly on the density functional theory (DFT) applied. The most stable conformers of DM-β-CD found with the B3LYP-GD2 method differ from these indicated by M062X-GD3 and other functionals. According to the latter, two crystal structures, ZULQAY and BOYFOK03, optimized in vacuo and in water, respectively, have the lowest energy. Both the B3LYP-GD2 and M062X-GD3 results show that all tested inclusion and noninclusion complexes of MIA:DM-β-CD in stoichiometry 1:1 are stable in water. However, the structures and their energetic properties obtained with each method differ: in the most stable configurations, different aromatic rings of MIA are embedded inside DM-β-CD, and the corresponding complexation energies (calculated with the 6-31++G(d,p) basis set and corrected for the basis set superposition error) are -29.6 (B3LYP-GD2) and -23.9 (M062X-GD3) kcal/mol. The NMR spectra of DM-β-CD and MIA:DM-β-CD are also compared.

Alginate enriched with phytic acid for hydrogels preparation. Therapeutic applications

In the last decade, numerous innovative strategies have been used to obtain highly efficient synthetic or semi-synthetic biomaterials. Between these innovative biomaterials, hydrogels occupy a distinct place due to their superior biological and physico-chemical characteristics. Alginate is a natural linear polysaccharide with important physico-chemical and biological properties. Recently, we obtained a new hydrogel based on alginate and phytic acid with improved physico-chemical properties. In the present study, the hydrogels previously obtained were tested in terms of their biological properties and possibilities of use in the biomedical field. For this purpose, the hydrogels were loaded with norfloxacin (NRF), an antibacterial compound utilised in the treatment against Gram-negative and Gram-positive organisms. Unfortunately, NRF has low solubility and permeability. In order to provide protection against loss, but also for enhanced bioavailability, and controlled-release of norfloxacin, a drug inclusion complex with cyclodextrin was realized. The effect of complexation on the release profile was highlighted. The addition of NRF to the hydrogel matrices greatly improved the antibacterial activity of the tested compounds. The presence of CD did not affect the homogeneity of the drug distribution. Changes in the polymeric matrix structure were registered after the incorporation of the drug, which were attributed to the relaxation of the network subsequently to the penetration and diffusion of the drug solution simultaneously with the swelling process. The release of NRF from Alg_PA polymeric network has been successfully modulated by the use of CD as a host molecule.

Characteristic of Cyclodextrins: Their Role and Use in the Pharmaceutical Technology

About 40% of newly-discovered entities are poorly soluble in water, and this may be an obstacle in the creation of new drugs. To address this problem, the present review article examines the structure and properties of cyclodextrins and the formation and potential uses of drug - cyclodextrin inclusion complexes. Cyclodextrins are cyclic oligosaccharides containing six or more D-(+)- glucopyranose units linked by α-1,4-glycosidic bonds, which are characterized by a favourable toxicological profile, low local toxicity and low mucous and eye irritability; they are virtually non-toxic when administered orally. They can be incorporated in the formulation of new drugs in their natural form (α-, β-, γ-cyclodextrin) or as chemically-modified derivatives. They may also be used as an excipient in drugs delivered by oral, ocular, dermal, nasal and rectal routes, as described in the present paper. Cyclodextrins are promising compounds with many beneficial properties, and their use may be increasingly profitable for pharmaceutical scientists.

Preferential solvation of carbohydrates in water-trifluoroethanol mixtures: a solvent detected heteronuclear NMR approach

The present study aims to establish a simple approach involving multi-field multinuclear longitudinal relaxation (R1) analysis of the solvents to decipher solute-solvent interactions during the solvation of model carbohydrates in aqueous trifluoroethanol (TFE) co-solvent systems (TFE:D2O). The behavior of D2O and TFE is monitored around β-CD (β-cyclodextrin) and glucose through R1D (2H) and R1F (19F), respectively. Correlation times (τc) are estimated for D2O and TFE for various % (v/v) compositions of TFE:D2O mixtures. The differential trends of the R1 or τc ratio for D2O and TFE (in the presence and absence of carbohydrates) revealed that both β-CD and glucose undergo selective solvation by TFE in comparison to D2O. Owing to its encapsulation properties, β-CD exhibited a comparatively higher tendency to undergo solvation by TFE than glucose. The maximum transfer of solute bound water to bulk solvent appears in the 20-30% (v/v) TFE range. The current approach emerges as being straightforward in contrast to traditional methods that primarily focus on solute behavior to unravel the preferential solvation dynamics.

Cyclodextrin-Assisted Extraction Method as a Green Alternative to Increase the Isoflavone Yield from Trifolium pratensis L. Extract

Trifolium pratense L. is receiving increasing attention due to the isoflavones it contains, which have been studied for their benefits to human health. A common problem with isoflavone aglycones is a rather low water solubility and limited pharmaceutical applications. The use of excipients, such as cyclodextrins in the production of isoflavone rich extracts, could become one of the new strategies for the extraction of target compounds. The aim of this study was to evaluate an eco-friendly method using the effects of α-, β- and γ-cyclodextrins for isoflavone solubilization in plant extracts in comparison to a standard extract without excipients. Extractions of red clover were prepared using ultrasound-assisted combined with thermal hydrolysis and heat reflux. It was determined that cyclodextrins significantly increased the isoflavones aglycone yields. By increasing cyclodextrins in the extraction media from 1 to 5%, the daidzin concentration increased on average by 1.06 (α-cyclodextrins), 1.4 (β-cyclodextrins) and 1.25 (γ-cyclodextrins) times. Genistein concentration increased using α- and γ-cyclodextrins (1.28 and 1.12 times, α- and γ-cyclodextrins, respectively), but decreased using β-cyclodextrins. The results showed that the cyclodextrin-assisted extraction enhanced the yields of isoflavones from red clover, which suggests using cyclodextrins as a green alternative and a cost-effective method to increase its pharmaceutical application.

Colorimetric Detection of Aliphatic Alcohols in β-Cyclodextrin Solutions

The sensitive, selective, and practical detection of aliphatic alcohols is a continuing technical challenge with significant impact in public health research and environmental remediation efforts. Reported herein is the use of a β-cyclodextrin derivative to promote proximity-induced interactions between aliphatic alcohol analytes and a brightly colored organic dye, which resulted in highly analyte-specific color changes that enabled accurate alcohol identification. Linear discriminant analysis of the color changes enabled 100% differentiation of the colorimetric signals obtained from methanol, ethanol, and isopropanol in combination with BODIPY and Rhodamine dyes. The resulting solution-state detection system has significant broad-based applicability because it uses only easily available materials to achieve such detection with moderate limits of detection obtained. Future research with this sensor system will focus on decreasing limits of detection as well as on optimizing the system for quantitative detection applications.

EDTA aggregates induce SYPRO orange-based fluorescence in thermal shift assay

Ethylenediaminetetraacetic acid (EDTA) is widely used in the life sciences as chelating ligand of metal ions. However, formation of supramolecular EDTA aggregates at pH > 8 has been reported, which may lead to artifactual assay results. When applied as a buffer component at pH ≈ 10 in differential scanning fluorimetry (TSA) using SYPRO Orange as fluorescent dye, we observed a sharp change in fluorescence intensity about 20°C lower than expected for the investigated protein. We hypothesized that this change results from SYPRO Orange/EDTA interactions. TSA experiments in the presence of SYPRO Orange using solutions that contain EDTA-Na+ but no protein were performed. The TSA experiments provide evidence that suggests that at pH > 9, EDTA4- interacts with SYPRO Orange in a temperature-dependent manner, leading to a fluorescence signal yielding a "denaturation temperature" of ~68°C. Titrating Ca2+ to SYPRO Orange and EDTA solutions quenched fluorescence. Ethylene glycol tetraacetic acid (EGTA) behaved similarly to EDTA. Analytical ultracentrifugation corroborated the formation of EDTA aggregates. Molecular dynamics simulations of free diffusion of EDTA-Na+ and SYPRO Orange of in total 27 μs suggested the first structural model of EDTA aggregates in which U-shaped EDTA4- arrange in an inverse bilayer-like manner, exposing ethylene moieties to the solvent, with which SYPRO Orange interacts. We conclude that EDTA aggregates induce a SYPRO Orange-based fluorescence in TSA. These results make it relevant to ascertain that future TSA results are not influenced by interference between EDTA, or EDTA-related molecules, and the fluorescent dye.

Effect of Cyclodextrin Types and Co-Solvent on Solubility of a Poorly Water Soluble Drug

The aim of the study was to investigate the solubility of piroxicam (Prx) depending on the inclusion complexation with various cyclodextrins (CDs) and on ethanol as a co-solvent. The phase-solubility method was applied to determine drug solubility in binary and ternary systems. The results showed that in systems consisting of the drug dissolved in ethanol–water mixtures, the drug solubility increased exponentially with a rising concentration of ethanol. The phase solubility measurements of the drug in aqueous solutions of CDs, β-CD and γ-CD exhibited diagrams of A_L-type, whereas 2,6-dimethyl-β-CD revealed A_P-type. The destabilizing effect of ethanol as a co-solvent was observed for all complexes regardless of the CD type, as a consequence of it the lowering of the complex formation constants. In systems with a higher concentration of ethanol, the drug solubility was increased in opposition to the decreasing complex formation constants. According to this study, the type of CDs played a more important role on the solubility of Prx, and the use of ethanol as a co-solvent exhibited no synergistic effect on the improvement of Prx solubility. The Prx solubility was increased again due to the better solubility in ethanol.