Solubilization of naproxen using N-methyl-2-pyrrolidone or ethanol and β-cyclodextrin

Solubility trend of naproxen in the presence of 5 and 10 mM of β-CD was measured at 298.2 K and compared with solubility profiles in the absence of β-CD for water + cosolvent mixtures. The saturated solutions of the given volume fractions were reached using shake-flask method, and then the solubility values were measured by UV spectrophotometric method at 256 nm. Afterwards, the experimental solubility data points of naproxen in water + ethanol (EtOH) and water + N-methyl-2-pyrrolidone with and without β-cyclodextrin (β-CD) were correlated with Jouyban–Acree model. Calculation results revealed that the back-calculated solubilities were in good agreement with the corresponding experimental values. By applying the correlated equations, one can rapidly predict the solubility of naproxen in all solvent compositions.     

Nanomolar detection of dopamine in the presence of ascorbic acid at β-cyclodextrin/graphene nanocomposite platform

Nanocomposite of β-cyclodextrin and graphene sheet (β-CD/GS) was successfully prepared, which exhibited high stability in aqueous solution. When used in electrochemical detection of dopamine, the β-CD/GS modified carbon electrode showed low detection limit, broad linear range, along with good ability to suppress the background current from large excess ascorbic acid. The electrochemical reaction of dopamine on the β-CD/GS showed a mass diffusion-controlled process, which was different from the adsorption-controlled process on the unmodified graphene sheet.     

A quartz crystal microbalance study of β-cyclodextrin self assembly on gold and complexation of immobilized β-cyclodextrin with adamantane derivatives

Quartz crystal microbalance (QCM) was used to study the self-assembly of per-6-thio-β-cyclodextrin (t₇-βCD) on gold surfaces, and the subsequent inclusion interactions of immobilized βCD with adamantane-poly(ethylene glycol) (5,000 MW, AD-PEG), 1-adamantanecarboxylic acid (AD-C) and 1-adamantylamine (AD-A). From a 50 μM solution of t₇-βCD in 60:40 DMSO:H₂O, a t₇-βCD layer was formed on gold with surface density of 71.7 ± 2.7 pmol/cm², corresponding to 80 ± 3% of close-packed monolayer coverage. Gold sensors with immobilized t₇-βCD were then exposed alternately to six different concentrations of AD-PEG, 500 μM AD-C or 500 μM AD-A aqueous solutions for association, and water for dissociation. Association of AD-PEG conformed to a Langmuir isotherm, with a best fit equilibrium constant K = 125,000 ± 18,000 M⁻¹. For AD-C and AD-A, association (k _a ) and dissociation (k _d ) rate constants were extracted from kinetic profiles by fitting to the Langmuir model, and equilibrium constants were calculated. The parameters for AD-C were found to be: k _a = 100 ± 5 M⁻¹ s⁻¹, k _d = 110 (±18) × 10⁻⁴ s⁻¹, and K = 9,400 ± 1,700 M⁻¹. For AD-A, k _a = 58 ± 6 M⁻¹ s⁻¹, k _d = 154 (±7) × 10⁻⁴ s⁻¹, and K = 3,800 ± 400 M⁻¹. The results demonstrate the utility of QCM as a tool for studying small molecule surface adsorption and guest–host interactions on surfaces. More specifically, the kinetic and thermodynamic data of AD-C, AD-A, and AD-PEG inclusion with immobilized t₇-βCD form a basis for further surface association studies of AD-X conjugates to advance surface sensory and coupling applications.     

Phosphorylation of β-cyclodextrin with substituted secondary hydroxy groups using phosphorous acid diamide

Phosphorylation of β-cyclodextin with substituted secondary hydroxy groups using 1,2-O,O′-isopropylideneglyceryl phosphorous diamide as a phosphorylating agent, in contrast to phosphorylation with trivalent phosphorus acid chlorides, is found to proceeds under mild conditions, but only in homogenous medium, and to afford acyclic diesteroamidophosphite derivatives of β-cyclodextin.     

Influence of β-cyclodextrin on the protolytic and complexing ability of p-aminobenzoic acid

UV spectroscopy was used to study the protolytic properties and determine the ionization constants of p-aminobenzoic acid in the presence of β-cyclodextrin. Formation of supramolecular structures of 1: 1 composition was established. Stability constants of the β-cyclodextrin-p-aminobenzoic acid inclusion complex were calculated, as were the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) of its formation. The complexing process between β-cyclodextrin and p-aminobenzoic acid was found to occur spontaneously in the temperature range under investigation while being accompanied by energy liberation and leading to a reduction in the system’s entropy.     

Inclusion complexes of sulfanilamide with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin

Sulfanilamide belongs to the group of drugs that have a bacteriostatic effect on different pathogenic microorganisms. This activity originates from the competitive antagonism with p-aminobenzoic acid, which is an integral part of folic acid. The safe use of sulfanilamide is limited due to poor solubility in the aqueous medium. Therefore, the aim of this paper is the synthesis of sulfanilamide, as well as preparing and structural characterization of its inclusion complexes with cyclodextrins. The crude sulfanilamide was obtained in the synthesis between acetanilide and chlorosulfonic acid according to the standard procedure. The synthesized sulfanilamide was recrystallized from water in order to obtain the satisfactory purity of the substance. Sufanilamide was complexed with β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin by the co-precipitation method. A molecular encapsulation of sulfanilamide was confirmed by using FTIR, ¹H-NMR, XRD and DSC methods. Phase-solubility techniques were used to assess the formation of the inclusion complex between sulfanilamide and cyclodextrins. The photostability of sulfanilamide and its inclusion complexes was estimated by UVB irradiation in a photochemical reactor by applying the UV–Vis method. Based on the UV–Vis analysis, sulfanilamide:2-hydroxypropyl-β-cyclodextrin complex was presented as more photostable than sulfanilamide:β-cyclodextrin complex and sulfanilamide. The obtained results enable the potential use of these inclusion complexes for the preparation of oral formulations due to the enhanced solubility of sulfanilamide.     

Preparation of gamma cyclodextrin stabilized solid lipid nanoparticles (SLNS) using stearic acid–γ-cyclodextrin inclusion complex

The inclusion complexation behaviour of higher chain fatty acid, stearic acid (SA) with gamma cyclodextrin has been investigated. The inclusion complex was characterized by FT-IR, ¹H NMR, 2D NMR, XRD and DSC techniques. The results showed that the SA molecule was entrapped inside the gamma cyclodextrin cavity. Further, inclusion complex was treated with lopinavir at 85 °C and emulsified with hot water at 85 °C. The resulted nanoemulsion was cooled down to form solid lipid nanoparticles (SLNs) stabilized with gamma cyclodextrin. Prepared SLNs were having average particle size of 212.5 ± 4.8 nm, zeta potential of ?19.7 ± 0.66 mV and drug loading of 57.54 ± 0.62 %. The surface characteristics of SLNs were also observed with transmission electron microscopy and atomic force microscopy. Results indicate that inclusion complex of SA and gamma cyclodextrin can be used for SLNs preparation.     

Absorptiometric and spectrofluorimetric study of the inclusion complexes of 2-naphthyloxyacetic acid and 1-naphthylacetic acid with β-cyclodextrin in aqueous solution

The inclusion complexes of 2-naphthyloxyacetic acid (NOA) and 1-naphthylacetic acid (NAA) with -cyclodextrin have been investigated in aqueous solution. It has been demonstrated that the naphthalene derivatives form 1:1 complexes when included in the cyclodextrin. A possible structure is proposed, having an axial inclusion of the naphthalene derivatives. In the case of the -CD: NOA complex, the naphthyl moiety is included in the cyclodextrin and the acetic acid group protrudes from the cavity, while NAA is only partially included because of the steric effect of the group in position 1. Association constants of 560±100 M^–1 and 100±50 M^–1 have been calculated for the -CD: NOA and -CD: NAA complexes, making use of the increment in the fluorescene emission produced in the inclusion process.     

Three-dimensional cyclodextrin: A new class of hosts by trehalose capping of β-cyclodextrin

In order to obtain better abiotic receptors for analytical and kinetic applications, the new capped derivative of cyclomaltoheptaose (CDTH) was synthesized by reaction of 6,6-dideoxy6,6-di(S-cysteamine)-,-trehalose with 6A,6D-dideoxy-6A,6D-diiodo-cyclo-maltoheptaose. The CDTH-ACS (anthraquinone-2-sulfonic acid sodium salt) system was investigated. by¹H NMR spectroscopy and by i.c.d. (induced circular dicroism), and a deep inclusion of ACS inside the CDTH cavity, with an association constant about six times larger with respect to ACS- -CD system was found.     

Purification of phloridzin from Lithocarpus polystachyus Rehd leaves using polymeric adsorbents functionalized with glucosamine and β-cyclodextrin

A high-efficient purification method of flavonoids from Lithocarpus polystachyus Rehd leaves is reported. Two adsorbents functionalized with glucosamine (GA) and β-cyclodextrin (β-CD) were synthesized and characterized by the Fourier transform infrared (FTIR) spectra. Also, adsorption properties and purification effect of flavonoids on different adsorbents were investigated. Two typical commercial adsorbents, AB-8 and D101, were employed as the reference materials. The adsorption capacity was enhanced remarkably by the introduction of GA and β-CD groups to the adsorbents. Moreover, the isotherms were well fitted by the Freundlich model. After a one-step column chromatographic separation, the purity of phloridzin increased significantly from 14.65 % to 79.48 % for PS-CD, to 66.56 % for PS-GA, 44.68 % for D101, and to 52.84 % for AB-8. This study provides a novel alternative matrix for the purification of phloridzin from Lithocarpus polystachyus Rehd leaves extracts.     

Structure and energy of formation of β- and γ-cyclodextrin complexes with amino acid enantiomers

The interaction between cyclodextrins (CyD), β-CyD, and γ-CyD, and the L- and D-optical isomers of several amino acids (Ala, Leu, His, Phe) are calculated using DFT. It is found that the L-forms of the investigated amino acids bond more strongly to CyD, due to the different numbers of hydrogen bonds that form. The structures of the resulting complexes are analyzed.     

Synthesis of β3-amino acid and peptides from D-ribose

Synthesis of new β³-amino acid, peptides and conformational analysis are reported from d-ribose, using Wittig olefination and Aza-Michael addition.     

Strong inclusion of inorganic anions into β-cyclodextrin immobilized to gold electrode

The inclusion of inorganic anions such as SO(4)(2-), NO(3)(-), and HPO(4)(2-) into the cavity of β-cyclodextrin monolayers on Au was examined by X-ray photoelectron spectroscopy (XPS), a quartz crystal microbalance (QCM), and chronocoulometric measurements of the competitive inclusion with ferrocene. The inclusion amounts of ferrocence in 0.2 M Na(2)SO(4), NaNO(3), and Na(2)HPO(4) solutions were less than 6% of the adsorption amount of β-cyclodextrin on Au, resulting in the apparent inhibition of the ferrocene redox reaction. The surface association constants of these anions reached about 10 on a logarithmic scale and were much higher than those for the inclusion of common organic guest compounds. A stronger anion inclusion was also demonstrated by the QCM response corresponding to the replacement of a preincluded organic guest with sulfate upon the injection of the sulfate solution. Quantitative analysis of the XPS data suggested a 1:1 association for each of these anions per surface β-cyclodextrin. There was no detectable inclusion for ClO(4)(-), Cl(-), and Br(-).     

Potentiometric determination of ascorbic acid in water–acetonitrile solution using pyrite and chalcopyrite electrodes

Journal of Solid State Electrochemistry - Performance characteristics of the solid-state potentiometric sensors, based on natural sulfide minerals pyrite and chalcopyrite, are assayed in aqueous...     

Synthesis of novel β2,2-amino acid from D-mannose and attempted synthesis of peptides from the amino acid

The study describes the synthesis of new α,α-disubstituted β-amino acid (β^2,2-Caa) and attempts the synthesis of peptides from it. The β^2,2-Caa was prepared from D-(+)-mannose, using crossed aldol and Cannizzaro reactions.     

Inclusion complex of usnic acid with β-cyclodextrin: characterization and nanoencapsulation into liposomes

In this study β-cyclodextrin (β-CD) was used to improve usnic acid (UA) solubility and the inclusion complex (UA:β-CD) was incorporated into liposomes in order to produce a targeted drug delivery system for exploiting the antimycobacterial activity of UA. A phase-solubility assay of UA in β-CD at pH 7.4 was performed. An apparent stability constant of K_1:1 = 234.5 M^?1 and a complexation efficiency of 0.005 was calculated. In the presence of 16 mM of β-CD the solubility of UA (7.3 μg/mL) increased more than 5-fold. The UA:β-CD complex was prepared using the freeze-drying technique and characterized through infrared and ¹HNMR spectroscopy, X-ray diffraction and thermal analyses. The UA:β-CD inclusion complex presented IR spectral modifications when compared with UA and β-CD spectra. ¹HNMR spectrum of UA:β-CD inclusion complex showed significant chemical shifts in proton H5 located inside the cavity of β-CD (Δδ = 0.127 ppm), suggesting that phenyl ring moiety of UA would be expected to be included within the β-CD cavity, interacting with the H-5 proton. A change in UA from its crystalline to amorphous form was observed on X-ray, suggesting the formation of a drug inclusion complex. DSC analysis showed the disappearance of the UA fusion peak UA:βCD complex. No differences between the antimicrobial activity of free UA and UA:βCD were found, supporting the hypothesis that the complexation with cyclodextrin did not interfere with drug activity. Liposomes containing UA:βCD were prepared using hydration of a thin lipid film method with subsequent sonication. Formulations of liposomes containing UA:βCD exhibited a drug encapsulation efficiency of 99.5% and remained stable for four months in a suspension form. Interestingly, the encapsulation of UA:βCD into the liposomes resulted in a modulation of in vitro kinetics of release of UA. Indeed, liposomes containing UA:β-CD presented a more prolonged release profile of free usnic acid compared to usnic acid-loaded liposomes.     

Formation of inclusion complexes and controlled release of atrazine using free or silica-anchored β-cyclodextrin

Immobilization of cyclodextrin on the surface of silica was performed using citric acid as the bonding agent. Inclusion complexes of atrazine with free (CD) or anchored (CDSI) β-cyclodextrin were prepared and then characterized using infrared spectroscopy, X-ray diffraction and differential scanning calorimetry. The complexation reaction showed first order kinetics, with a rate constant (k) of 8.72?×?10^?3 min^?1. There was a rapid increase of absorbance in the first 40?min, followed by attainment of equilibrium after ~2?h. The stoichiometry of the reaction was 1:1, with both free and anchored β-cyclodextrin increasing the solubilization of atrazine in an aqueous medium (by around 1.5 and 3.4 times, respectively). The association constant (K _a) of the complex was 28.93?L?mol^?1 using CD and 130.68?L?mol^?1 using CDSI. In release tests, 62% of the atrazine complexed with CDSI or β-CD was released after 40?h, while 83% of free atrazine was released during the same period.     

Anti-inflammatory,analgesic and molecular docking studies of Lanostanoic acid 3-O-α-D-glycopyranoside isolated from Helichrysum stoechas

Helichrysum stoechas has been conventionally used as herbal tea due to its anti-inflammatory, antioxidant, antimicrobial and diuretic activities. Ethanolic extract of the aerial parts of the plant (HSE) afforded a lanostane triterpenoid glycoside. The isolated compound was characterized as Lanostan-3β-olyl-26-oic acid 3-O-α-D-glycopyranoside (HS-01) with the help of UV, IR, ¹H, ¹³C NMR and MS spectroscopic techniques. HSE (at 100 and 200 mg/kg doses) and the isolated compound, HS-01 (at 10 mg/kg dose) has been investigated for anti-inflammatory and analgesic activities against chemically challenged experimental animal. Both the HSE as well as HS-01 showed a substantial decline in paw volume when compared with the relevant control groups (p < 0.01 & p < 0.001). The HSE and HS-01 also confirms a significant prolongation of the paw licking or jumping towards the Eddy’s hot plate and reduction in quantity of writhes after the introduction of acetic acid in mice (p < 0.01 & p < 0.001). In order to have a better understanding of the binding interactions of HS-01 at molecular level, docking studies were performed with various macromolecular drug targets using AutoDock 4.2 and AutoDock Vina 1.1. Both programs predicted Galectin-3 as most favorable target for HS-01 followed by iNOS, whereas TNFα and COX-2 were among less favorable. Therefore, HS-01 could be developed as suitable therapy against inflammation and associated disorders.