Synthesis of Novel Bis(β-cyclodextrin)s Linked with Glycol and Their Inclusion Complexation with Organic Dyes

Preparation and Evaluation of an Azobenzenediamide Bridged bis(β-Cyclodextrin)-Bonded Chiral Stationary Phase for HPLC

An azobenzenediamide bridged bis(β-cyclodextrin) chiral stationary phase (AZCDP) was prepared, and its high-performance liquid chromatography performance in reversed-phase and polar organic modes was evaluated by chiral probes, including triazoles, flavanones, amino acids and β-blockers. The results showed that AZCDP had strong chiral separation ability and the 40 chiral compounds were successfully resolved, of which 32 were completely separated (Rs ≥ 1.5) and the best enantioresolution was up to 3.93 within 20 min under a wide range of pH value and temperature. The separation ability of AZCDP with double cavities was significantly better than common CD-CSPs with single cavity, which was related to the synergistic inclusion effect. Compared with the previously reported stilbene (C=C)-bridged CSP, AZCDP with azobenzene (N=N)-bridged had a wider resolution range. For example, it could resolve myclobutanil, pindolol, carteolol, betaxolol, bevanolol and bitertanol, which could not be resolved before, and should be related to the fact that the flexible N=N was more compatible with the synergistic inclusion between cavities than the rigid C=C bridge group. The azobenzenediamide bridging group could also provide hydrogen bond, π-π and other sites, which was conducive to chiral separations.

Mono-6-Substituted Cyclodextrins-Synthesis and Applications

Cyclodextrins are well known supramolecular hosts used in a wide range of applications. Monosubstitution of native cyclodextrins in the position C-6 of a glucose unit represents the simplest method how to achieve covalent binding of a well-defined host unit into the more complicated systems. These derivatives are relatively easy to prepare; that is why the number of publications describing their preparations exceeds 1400, and the reported synthetic methods are often very similar. Nevertheless, it might be very demanding to decide which of the published methods is the best one for the intended purpose. In the review, we aim to present only the most useful and well-described methods for preparing different types of mono-6-substituted derivatives. We also discuss the common problems encountered during their syntheses and suggest their optimal solutions.

Cyclodextrin-Promoted Fluorescence Detection of Aromatic Toxicants and Toxicant Metabolites in Commercial Milk Products

The detection of polycyclic aromatic hydrocarbons (PAHs) and their metabolites in food and in agricultural sources is an important research objective due to the PAHs' known persistence, carcinogenicity, and toxicity. PAHs have been found in the milk of lactating cows, and in the leaves and stems of plants grown in PAH-contaminated areas, thereby making their way into both cow milk and plant milk alternatives. Reported herein is the rapid, sensitive, and selective detection of 10 PAHs and PAH metabolites in a variety of cow milks and plant milk alternatives using fluorescence energy transfer from the PAH to a high quantum yield fluorophore, combined with subsequent array-based statistical analyses of the fluorescence emission signals. This system operates with high sensitivity (low micromolar detection limits), selectivity (100% differentiation even between structurally similar analytes), and general applicability (for both unmodified lipophilic PAHs and highly polar oxidized PAH metabolites, as well as for different cow and plant milk samples). These promising results show significant potential to be translated into solid-state devices for the rapid, sensitive, and selective detection of PAHs and their metabolites in complex, commercial food products.

New synthetic strategies for xanthene-dye-appended cyclodextrins

Xanthene dyes can be appended to cyclodextrins via an ester or amide bridge in order to switch the fluorescence on or off. This is made possible through the formation of nonfluorescent lactones or lactams as the fluorophore can reversibly cyclize. In this context we report a green approach for the synthesis of switchable xanthene-dye-appended cyclodextrins based on the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). By using 6-monoamino-β-cyclodextrin and commercially available inexpensive dyes, we prepared rhodamine- and fluorescein-appended cyclodextrins. The compounds were characterized by NMR and IR spectroscopy and MS spectrometry, their UV-vis spectra were recorded at various pH, and their purity was determined by capillary electrophoresis. Two potential models for the supramolecular assembly of the xanthene-dye-appended cyclodextrins were developed based on the set of data collected by the extensive NMR characterization.

Host–Guest Inclusion System of Luteolin with Polyamine-β-cyclodextrin: Preparation, Characterisation, Anti-oxidant and Anti-cancer Activity

The characterisation, inclusion complexation behaviours, and binding ability of inclusion complexes of luteolin (LU) with four polyamine-modified β-cyclodextrins (NH2-βCD, EN-βCD, DETA-βCD, TETA-βCD; where EN = ethylenediamine; DETA = diethylenediamine; TETA = triethylenetetramine) were investigated in both the solid and solution forms by photoluminescence spectroscopy, 1H and 2D NMR spectroscopy, differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy. The results showed that the water solubility, and the anti-oxidant activity and anti-cancer activity of LU were significantly increased in the inclusion complex with polyamine-β-cyclodextrin. The LU/CDs complex will be useful for its application as herbal medicine or healthcare product.

Host–Guest Inclusion System of Scutellarin with Polyamine-β-Cyclodextrin: Preparation, Characterisation, and Anti-cancer Activity

The inclusion complexation behaviours of scutellarin (SCU) with four polyamine-modified β-cyclodextrins (NH2-βCD, EN-βCD, DETA-βCD, and TETA-βCD; EN = ethylenediamine; DETA = diethylenetriamine; TETA = triethylenetetramine) have been investigated in both solution and solid state by photoluminescence spectroscopy, 1H and two-dimensional NMR spectroscopy, thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. The results showed that, with the increase in the number of amino groups, the hosts polyamine-modified β-cyclodextrins (NH2-βCD, EN-βCD, DETA-βCD, TETA-βCD) were able to solubilise SCU to higher levels than native β-CD (9.0 mg mL–1) up to 15.8, 20.4, 44.6, 50.7 mg mL–1 (calculated as SCU), respectively. Besides, the anti-tumour activity of SCU obviously increased after formation of the inclusion complexes. The SCU/CD complexes will be potentially useful for the design of a novel formulation of SCU for clinical treatment.

Spectrophotometric study of the selective binding behavior of aliphatic oligopeptides by bridged bis(β-cyclodextrin) linked by a 4,4′-diaminodiphenyl disulfide tether

The conformation and binding behavior of 4,4′-diaminodiphenyl disulfide bridged bis(β-cyclodextrin) (1) towards representative aliphatic oligopeptides, i.e., Leu-Gly, Gly-Leu, Glu-Glu, Met-Met, Gly-Gly, Gly-Gly-Gly, and Gly-Pro, were investigated by circular dichroism, fluorescence, and 1H and 2D NMR spectroscopy at 25 °C in phosphate buffer (pH 7.20). The results indicated that 1 acts as an efficient fluorescent sensor and displays remarkable fluorescence enhancement upon addition of optically inert oligopeptides. Owing to the cooperative host–linker–guest binding mode in which the linker and guest are coincluded in the two cyclodextrin cavities, the bis(β-cyclodextrin) 1 gives high binding constants of up to 103–104 (mol/L)–1 for oligopeptides. The bis(β-cyclodextrin) 1 can recognize not only the size and shape of oligopeptides but also the hydrophobicity, giving an exciting residue selectivity of up to 61.3 for the Gly-Leu/Glu-Glu pair. These phenomena are discussed from the viewpoints of multiple recognition and induce-fit interactions between host and guest.