Cyclodextrin-mediated gold nanoparticles as multisensing probe for the selective detection of hydroxychloroquine drug

β-Cyclodextrin (β-CD) modified gold nanoparticles (AuNP) were rapidly synthesized using microwave assisted procedure. Parameters, such as time, pH and concentrations of β-CD and gold, were optimized for the synthesis of β-CD-AuNP. The addition of enantiomers and racemic mixture of hydroxychloroquine (R-HCQ, S-HCQ and RS-HCQ) drugs and their interaction with β-CD led to a red shift in the surface plasmon resonance of β-CD-AuNP. The changes associated with the introduction of HCQ in β-CD-AuNP were studied using various characterization techniques such as UV-vis, FT-IR, XRD, dynamic light scattering, zeta potential, transmission electron microscopy, fluorescence spectroscopy and electrochemical techniques. The host-guest interaction of β-cyclodextrin with S-HCQ, R-HCQ and RS-HCQ resulted in the aggregation of gold nanoparticles. The surface plasmon resonance at 521 nm for β-CD-AuNP was shifted to 600, 620 and 670 nm on the addition of S-HCQ, R-HCQ and RS-HCQ, respectively, with a color change from pink to blue. The selectivity and sensitivity of the developed system for RS-HCQ were investigated and the limit of detection (LOD=3 s/m) was found to be 2.61, 0.15, and 0.85 nM for optical, fluorescence and electrochemical methods, respectively. The successful monitoring of RS-HCQ drug in pharmaceutical samples is possible with these techniques.

Electronic Supplementary Material

Supplementary material is available for this article at 10.1007/s11814-020-0719-7 and is accessible for authorized users.

Application of capillary electrophoresis technique for the enantioseparation of bioactive ferrocene-based compounds versus DFT calculated data

Herein, a series of bioactive ferrocene-modified N-heterocycles with alkyl linkers was prepared in good to quantitative yields starting from easy accessible ferrocene alcohols and heterocycles under acidic or neutral (for imidazole) conditions in racemic forms. The analytical resolution of a number of bioactive racemic ferrocene azoles 1-6 (where azole = imidazole, pyrazole, and benzotriazole derivatives) into enantiomers was first carried out by CE using sulfobuthylether-β-CD (captisol) as a chiral selector. The analytical approaches to highly enantiomeric-enriched ferrocene derivatives are based on the formation of their inclusion complexes. The best chiral separation was achieved using zone CE in a quartz capillary. The ACE was used to evaluate the stability constants of captisol complexes with enantiomeric forms of two ferrocene derivatives 1, FcCHMe-imidazole, and 6, FcCHMe-benzotriazole. The optimal conditions for the resolution of the studied (R, S)-ferrocene compounds 1, 2, and 6 were predicted on the basis of the performed quantum chemical calculations and then implemented by the electrophoretic method. A high correlation between density functional theory calculation results and experimental electrophoresis data were obtained. Successful enantioseparation of racemic mixtures is of great importance for the characterization and further applications of drug candidates in enantiopure forms and in the development of clinical treatment. The advantages of the CE procedure make it possible to have important practical value and significance for determining the purity and enantiomeric excess of other ferrocene-containing compounds.

Synthesis and anti-HCV entry activity studies of β-cyclodextrin-pentacyclic triterpene conjugates

In our previous studies, oleanolic acid (OA) and echinocystic acid (EA), isolated from Dipsacus asperoides, were found to have anti-HCV entry properties. The major issue for members of this type of triterpene is their low water solubility. In this study, a series of new water-soluble triazole-bridged β-cyclodextrin (CD)-pentacyclic triterpene conjugates were synthesized via click chemistry. Thanks to the attached β-CD moiety, all synthesized conjugates showed lower hydrophobicity (Alog P) than their parent compounds. Several conjugates exhibited moderate anti-HCV entry activity. With the exception of per-O-methylated β-CD-pentacyclic triterpene conjugates, all other conjugates showed no cytotoxicity based on an alamarBlue assay carried out with HeLa, HepG2, MDCK, and 293T cells. More interestingly, the hemolytic activity of these conjugates disappeared upon the introduction of β-CDs. Easy access to such conjugates that combine the properties of β-CD and pentacyclic triterpenes may provide a way to obtain a new class of anti-HCV entry inhibitors.

Gas phase isomeric differentiation of oleanolic and ursolic acids associated with heptakis-(2,6-di-O-methyl)-beta-cyclodextrin by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Oleanolic acid (OA) and ursolic acid (UA) are isomeric triterpenoid compounds with similar pharmaceutical properties. Usually, modern chromatographic and electrophoretic methods are widely utilized to differentiate these two compounds. Compared with mass spectrometric (MS) methods, these modern separation methods are both time- and sample-consuming. Herein, we present a new method for structural differentiation of OA and UA by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with the association of heptakis-(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CD). Exact MS and tandem MS (MS/MS) data showed that there is no perceptible difference between OA and UA, as well as their beta-cyclodextrin and gamma-cyclodextrin complexes. However, there is a remarkable difference in MS/MS spectra of DM-beta-CD complexes of OA and UA. The peak corresponding to the neutral loss of a formic acid and a water molecule could only be observed in the MS/MS spectrum of the complex of DM-beta-CD : OA. Molecular modeling calculations were also employed to further investigate the structural differences of DM-beta-CD : OA and DM-beta-CD : UA complexes. Therefore, by employing DM-beta-CD as a reference reagent, OA and UA could be differentiated with purely MS method.

Review of aqueous chiral electrokinetic chromatography (EKC) with an emphasis on chiral microemulsion EKC

The separation of enantiomers using electrokinetic chromatography (EKC) with chiral microemulsions is comprehensively reviewed through December 1, 2006. Aqueous chiral EKC separations based on other pseudostationary phases such as micelles and vesicles or on other chiral selectors such as CDs, crown ethers, glycopeptides, ligand exchange moeities are also reviewed from both mechanistic and applications perspective for the period of January 2005 to December 1, 2006.

Supramolecular Chemistry in Water

Supramolecular chemistry in water is a constantly growing research area because noncovalent interactions in aqueous media are important for obtaining a better understanding and control of the major processes in nature. This Review offers an overview of recent advances in the area of water-soluble synthetic receptors as well as self-assembly and molecular recognition in water, through consideration of the functionalities that are used to increase the water solubility, as well as the supramolecular interactions and approaches used for effective recognition of a guest and self-assembly in water. The special features and applications of supramolecular entities in aqueous media are also described.

Ligand exchange capillary electrophoresis by cyclodextrin derivatives, a powerful tool for enantiomeric separations

Five pure CD derivatives synthesized in our laboratory were used as chiral selectors in the presence of copper(II) ion. Three enantiomeric pairs of amino acids were submitted to separation experiments in CE, by exploiting the ligand exchange mechanism. The results obtained in the investigated systems, together with those of the analogous systems previously studied, clearly show the usefulness of this technique in chiral separations. By comparing the ligand exchange CE results with potentiometric results, either reported elsewhere or studied here for the first time (system Cu/CDampy/tyrosine), it has been possible to rationalise the separation results. The importance of the availability of pure selectors, and to characterise them both spectroscopically and thermodynamically is discussed.

Physicochemical and structural characterization of quercetin-beta-cyclodextrin complexes

Quercetin is a bioactive flavonoid widely used as a health supplement. Being sparingly soluble and chemically unstable in aqueous intestinal fluids, quercetin is poorly absorbed orally. This study aimed to investigate the effects of three beta-cyclodextrins, namely, unsubstituted beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and sulfobutyl ether beta-cyclodextrin (SBE-beta-CD) on the chemical stability and water solubility of quercetin, and to elucidate the complexation mechanisms of these beta-CDs with quercetin. Quercetin-beta-CD complexes in solution were characterized by stability assessment, phase solubility measurements, and 1H-nuclear magnetic resonance (NMR) spectroscopy. Molecular modeling was used to help establish the mode of interaction of the beta-CDs with quercetin. Solubility enhancements of quercetin obtained with the three beta-CDs followed the rank order: SBE-beta-CD > HP-beta-CD > beta-CD. The stability of quercetin at alkaline pHs also showed substantial improvement. NMR spectroscopic analysis suggested that the B-ring, C-ring, and part of the A-ring of quercetin display favorable interaction with the hydrophobic cavity of the beta-CDs, which was confirmed by molecular dynamics (MD) simulations using a solvated model of the quercetin-beta-CD complex. An inclusion complex model has been established for explaining the observed augmentation of solubility and stability of quercetin in water by beta-CDs.