Mass Spectrometric Evaluation of ß-Cyclodextrins as Potential Hosts for Titanocene Dichloride.

Bent metallocene dichlorides (Cp2MCl2, M = Ti, Mo, Nb, …) have found interest as anti-cancer drugs in order to overcome the drawbacks associated with platinum-based therapeutics. However, they suffer from poor hydrolytic stability at physiological pH. A promising approach to improve their hydrolytic stability is the formation of host-guest complexes with macrocyclic structures, such as cyclodextrins. In this work, we utilized nanoelectrospray ionization tandem mass spectrometry to probe the interaction of titanocene dichloride with ß-cyclodextrin. Unlike the non-covalent binding of phenylalanine and oxaliplatin to ß-cyclodextrin, the mixture of titanocene and ß-cyclodextrin led to signals assigned as [ßCD + Cp2Ti-H]+, indicating a covalent character of the interaction. This finding is supported by titanated cyclodextrin fragment ions occurring from collisional activation. Employing di- and trimethylated ß-cyclodextrins as hosts enabled the elucidation of the influence of the cyclodextrin hydroxy groups on the interaction with guest structures. Masking of the hydroxy groups was found to impair the covalent interaction and enabling the encapsulation of the guest structure within the hydrophobic cavity of the cyclodextrin. Findings are further supported by breakdown curves obtained by gas-phase dissociation of the various complexes.

Synthesis, separation, and purification of glucosyl-ß-cyclodextrin by one-pot method.

Glucosyl-ß-cyclodextrin (G1 -ß-CD) has wide application prospects in the food, pharmaceutical, agriculture, and chemical industry as its better solubility and biocompatibility than parent ß-cyclodextrin (ß-CD). However, researches on G1 -ß-CD were few due to difficulties in its preparation and separation. In the present study, a one-pot method was as follows: first, maltosyl-ß-cyclodextrin (G2 -ß-CD) was prepared through the reverse synthesis capability of pullulanase. Then, G1 -ß-CD was obtained through hydrolysis by glucoamylase in the same reaction system and further purified by gel filtration chromatography. The results revealed that the optimal conditions for the reverse synthesis were as follows: nG2 :nß-CD , 8:1; enzyme concentration, 60 U/ml; reaction temperature, 60°C; pH, 4.5; reaction time, 60 hr. The optimal conditions for G2 -ß-CD hydrolysis were as follows: reaction time, 8 hr; enzyme concentration, 40 U/ml. Finally, the pure G1 -ß-CD samples were obtained by Sephadex G-25 gel column separation and identified by HPLC, LC-MS/MS, and NMR chromatography. PRACTICAL APPLICATIONS: Commercially available modified CDs are almost synthesized using the chemical method, such as methyl-, sulfonylbutyl-, and hydroxypropyl-CD. However, the chemical synthesis of modified CDs has some security issue, such as organic solvent residue, which limits its application in foods. Based on the relevance references, G1-ß-CD not only has the inclusion properties of the parent ß-CD but also improves solubility and reduces the hemolysis effect and nephrotoxicity. However, the synthesis and separation of G1-ß-CD is an obstacle to its expansion in production and application. In addition, there are few studies on G1-ß-CD and few companies selling the product on the market. In this manuscript, the G1-ß-CD was successfully synthesized by one-pot method and the optimal preparation and separation conditions of G1-ß-CD were investigated.

Eplingiella fruticosa leaf essential oil complexed with ß-cyclodextrin produces a superior neuroprotective and behavioral profile in a mice model of Parkinson's disease.

Evidence indicates that oxidative stress has an important role in the onset and progression of Parkinson's disease (PD). Antioxidant agents from natural products have shown neuroprotective effects in animal models of PD. Eplingiella fruticosa is an aromatic and medicinal plant of the Lamiaceae family that include culinary herbs. The essential oil (EPL) has anti-inflammatory and antioxidant activities. Cyclodextrins are used to enhances pharmacological profile of essential oil. We obtained the EPL from leaves and complexed with ß-cyclodextrin (EPL-ßCD). Phytochemical analysis showed as main constituents: ß-caryophyllene, bicyclogermacrene and 1,8-cineole. We evaluated the effects of EPL and EPL-ßCD (5 mg/kg, p.o. for 40 days) on male mice submitted to the progressive reserpine PD model. Behavioral evaluations, lipid peroxidation quantification and immunohistochemistry for tyrosine hydroxylase were conducted. EPL delayed the onset of catalepsy and decreased membrane lipid peroxides levels in the striatum. EPL-ßCD also delayed the onset of catalepsy, reduced the frequency of oral diskynesia, restored memory deficit, produced anxiolytic activity and protected against dopaminergic depletion in the striatum and SNpc. These findings showed that EPL has a potential neuroprotective effect in a progressive PD animal model. Further, EPL-ßCD enhanced this protective effects, suggesting a novel therapeutic approach to ameliorate the symptoms of PD.

Computer simulation and enantioselective capillary electrophoresis to characterize isomer mixtures of sulfated ß-cyclodextrins.

The enantiomeric separation of methadone in the presence of multiple isomer mixtures of sulfated ß-cyclodextrin (S-ß-CD) was studied experimentally with CZE and theoretically using computer simulation. Experiments were performed over many years with several lots of S-ß-CD from the same manufacturer with a specified degree of substitution of 7-11. Large differences in the migration patterns were observed between certain lots and it was concluded that the extent of labelling in lots released after a transition time was higher than originally specified. The migration pattern was observed to be associated with (i) the ionic strength increase resulting from using S-ß-CDs with a higher charge state and (ii) differences in buffer composition. Apparent binding constants between methadone and the S-ß-CD and complex mobilities were determined for different lots of S-ß-CD at varying ionic strength using phosphate and 3-morpholino-2-hydroxypropanesulfonic acid buffers. The obtained values were used as input for simulations. For a given ionic strength, agreement between predicted and experimentally observed behavior was obtained for different buffers. R-methadone has a stronger interaction with S-ß-CD than S-methadone. For any given configuration there is a distinct S-ß-CD concentration range which results in the cationic migration of S-methadone while the migration direction of R-methadone is reversed. This configuration was demonstrated to be applicable for micropreparative CZE separations.

Physico-chemical and Biological Evaluation of Flavonols: Fisetin, Quercetin and Kaempferol Alone and Incorporated in beta Cyclodextrins.

BACKGROUND: Fisetin,quercetin and kaempferol are among the important representatives of flavonols, biological active phytocomounds, with low water solubility. OBJECTIVE: To evaluate the antimicrobial effect, respectively the antiproliferative and pro apoptotic activity on the B164A5 murine melanoma cell line of pure flavonols and their beta cyclodextrins complexes. METHOD: Incorporation of fisetin, quercetin and kaempferol in beta cyclodextrins was proved by scanning electron microscopy (SEM), differencial scanning calorimetry (DSC) and X-ray powder diffraction (XRPD). Pure compounds and their complexes were tested for antiproliferative (MTT) and pro-apoptotic activity (Annexin V-PI) on the B164A5 murine melanoma cell line and for the antimicrobial properties (Disk Diffusion Method) on the selected strains. RESULTS: The phytocompounds presented in a different manner in vitro chemopreventive activity against B164A5 murine melanoma cell line and weak antimicrobial effect. CONCLUSION: The three flavonols: fisetin, quercetin and kaempferol were successfully incorporated in beta-cyclodextrin (BCD) and hydroxylpropyl-beta-cyclodextrin (HPBCD). Incorporation in beta cyclodextrins had a mix effect on the biological activity conducing to decrease, increase or consistent effect compared to pure phytocompound, depending on the screened process and on the chosen combination.

Micellar Electrokinetic Chromatography of Aminoglycosides.

The components of the aminoglycosides, e.g., gentamicin, sisomicin, netilmicin, kanamycin, amikacin, and tobramycin, and related impurities of these antibiotics can be separated by means of micellar electrokinetic chromatography (MEKC). Derivatization with o-phthaldialdehyde and thioglycolic acid is found to be appropriate for these antibiotics. The background electrolyte was composed of sodium tetraborate (100 mM), sodium deoxycholate (20 mM), and ß-cyclodextrin (15 mM) having a pH value of 10.0. This method is valid for evaluation of gentamicin, kanamycin, and tobramycin. It has to be adopted for amikacin, paromomycin, neomycin, and netilmicin.

Preparation, Characterization and Pharmacokinetic Study of Xiangfu Siwu Decoction Essential Oil/ß-Cyclodextrin Inclusion Complex.

Xiang-Fu-Si-Wu Decoction (XFSWD), a famous Chinese herbal formula, is considered an effective prescription for treating primary dysmenorrhea. The essential oil is a significant effective ingredient of XFSWD. However, its volatility, instability and poor water-solubility influence its pharmacodynamic effects. ß-Cyclodextrin (ß-CD) has the intrinsic ability to form specific inclusion complexes with such drugs to enhance their stability, solubility and bioavailability. The aim of this study was thus to compare the pharmacokinetic characteristics and the oral bioavailability of XFSWD essential oil (XEO) and its ß-CD inclusion complex after oral administration to rats. A simple, rapid, and sensitive ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous quantification of five active components of XEO in rat plasma. The in vivo data showed that XEO/ß-CD inclusion complex displayed higher maximum plasma concentration (Cmax), longer half-time (T1/2) and bigger area under the concentration-time curve (AUC0-24 h). These results demonstrated that the formation of ß-CD inclusion complex has significantly increased the oral bioavailability of the drugs in rats than free oil.

Inhibitory effect of Angelica sinensis extract in the presence of 2-hydroxypropyl-ß-cyclodextrin.

Angelica sinensis (AS) is a traditional Chinese medicinal herb. Its ethanolic extract contains active ingredients, such as ferulic acid, ligustilide, and butylidenephthalide, which are hydrophobic and have inhibitory effects on hepatoma cells. To increase the aqueous solubility/dispersibility of AS extract and study the consequent inhibitory effect on hepatoma cells, the ethanolic extract of AS was complexed with 2-hydroxypropyl-ß-cyclodextrin (HP-ß-CD), a cyclic oligosaccharide that has a hydrophilic outer surface and a hydrophobic central cavity. The AS-HP-ß-CD complex (weight ratio of AS extract: HP-ß-CD=1:5) was prepared and characterized. The effect of complexing the AS extract with HP-ß-CD on Hep3B cell growth was investigated by analyzing cytotoxicity. Our results showed that cytotoxicity inhibition of AS-HP-ß-CD complex was up to 94% and higher than that of AS extract (about 68%). These observations suggested that the use of HP-ß-CD to stabilize AS extract in aqueous solution was possible for herbal medicine application.

Enantioseparation performance of novel benzimido-ß-cyclodextrins derivatized by ionic liquids as chiral stationary phases.

Four novel ß-cyclodextrin (ß-CD) derivatives functionalized by ionic liquids, in which the substituents and cyclodextrin cavity are linked by a CH2-N=C group, were successfully prepared, and the corresponding chiral stationary phases (CSPs) based on silica gel, namely mono-6-deoxy-6-(p-N,N,N-trimethylaminobenzimide)-ß-CD nitrate CSP (4a), mono-6-deoxy-6-(p-N,N,N-trimethylaminobenzimide)-ß-CD tosylate CSP (4b), mono-6-deoxy-6-(p-N-methylimidazolemethylbenzimide)-ß-CD nitrate CSP (4c) and mono-6-deoxy-6-(p-N-methylimidazolemethylbenzimide)-ß-CD tosylate CSP (4d), were applied in high-performance liquid chromatography (HPLC). A large number of analytes including chiral 1-phenyl-2-nitroethanol derivatives, aromatic alcohols and ferrocene derivatives were investigated to evaluate the separation performance of the four CSPs, and excellent enantioseparations were obtained for most of the analytes. For 1-phenyl-2-nitroethanol derivatives and aromatic alcohols, the cationic substituent with smaller volume on ß-CD derivative was beneficial for the enantioseparation of most compounds. Furthermore, the anion structures on these CSPs play an important role in the separation of solutes. The analytes with smaller molecular volume were more effectively separated on CSP 4b with the tosylate anion by offering hydrogen-bonding and π-π interactions, while the nitrate anions on CSPs 4a and 4c were more favorable for the separation of the compounds with larger volumes due to the weaker steric bulk. The enantiomeric separation results of ferrocene derivatives further showed good separation capability of CSPs 4b and 4c. The cooperation of cationic and anionic substituents on ß-CD derivatives is essential for the separation of these chiral compounds.

On-line enantioseparation of chlorpheniramine using ß-cyclodextrin and carbon nanotubes after multivariate optimization.

Multiwalled carbon nanotubes are evaluated here as solid phase extraction (SPE) sorbent aiming to (±)-chlorpheniramine (CPA) enantioresolution with fluorimetric detection. ß-cyclodextrin (CD) was added to the racemate and solutions with HCl and sodium dodecyl sulfate (SDS) in different proportions were assayed as eluents to achieve the separation between both enantiomers. The overall methodology involved a flow injection (FI) strategy enabling high sample throughput and low reagents consumption making it suitable for drug routine quality control. An adequate enantioresolution (2.08) with satisfactory responses for both (R)-CPA (peak area=285) and (S)-CPA (peak area=380) was achieved applying the proposed FI-SPE strategy under the optimized conditions [ß-CD] = 1.0 mmol L(-1), [HCl] = 1.0 × 10(-2) mol L(-1), [SDS] = 4.0 × 10(-4) mol L(-1) and eluent flow rate = 8.0 rpm.

Synthesis of water-soluble multidentate aminoalcohol ß-cyclodextrin derivatives via epoxide opening.

New highly soluble ß-aminoalcohol ß-cyclodextrin (ß-CD) derivatives have been synthesized via nucleophilic epoxide opening reactions with mono-6-amino mono-6-deoxy-permethyl-ß-CD and mono-6-amino mono-6-deoxy-ß-CD. The binding properties of the ß-CD were enhanced by linking aminoalcohol subunits which caused its solubility to improve markedly. The reaction conditions were optimised using microwave irradiation giving moderate-to-good yields with a series of epoxides. A regioselective epoxide opening reaction was observed in the reaction with styrene oxide while the stereoselectivity was strictly dependent on substrate structure.

Regioselective allylation of cyclomaltoheptaose (ß-cyclodextrin) leading to per(2,6-di-O-hydroxypropyl-3-O-methyl)-ß-cyclodextrin.

The selective modification of cyclodextrins remains a real challenge to obtain well-defined structures. The targeted cycloheptakis-(1→4)-2,6-di-O-hydroxypropyl-3-O-methyl-α-D-glucopyranosyl [per(2,6-di-O-hydroxypropyl-3-O-methyl)-ß-CD] was obtained by a three-step procedure. The selective allylation of the hydroxyl functions at the positions 2 and 6 was used as a first step. This reaction was revisited then enlarged to α and γ-CDs to determine new conditions for a one-step synthesis in high yield. The per(2,6-di-O-allyl)-ß-CD derivative was then reacted with iodomethane to provide per(2,6-di-O-allyl-3-O-methyl)-ß-CD. Oxidative hydroboration of the allyl functions was then carried out in order to obtain a new CD derivative with seven primary hydroxyl functions on each side of the truncated cone, having a similar reactivity.

Pilot-scale electrokinetic movement of HCB and Zn in real contaminated sediments enhanced with hydroxypropyl-beta-cyclodextrin.

This study deals with the efficiency of a pilot-scale electrokinetic (EK) treatment on real aged sediments contaminated with hexachlorobenzene (HCB) and Zn. A total of 0.5m(3) of sediments were treated under a constant voltage in a polyvinyl chloride reactor. The changes of sediment pH, electrical conductivity (EC), organic content (OC), the transport of contaminants in sediments and the consumption of electric energy were evaluated. After 100 d processing, sediment pH slightly increased compared with the initial values, particularly in the bottom layer close to cathodic section, while sediment EC in most sections significantly decreased. Sediment OC in all sections increased, which implied that hydroxypropyl-beta-cyclodextrin (HPCD) was successfully penetrated across sediments by electroosmosis. Significant movement of contaminants was observed across sediments with negligible removals. Both HCB and Zn generally moved from sections near anode and accumulated near cathode. Upon the completion of treatment, the electric energy consumption was calculated as 563 kWhm(-3). This pilot-scale EK test indicates that it is difficult to achieve great removal of hydrophobic organic compounds (HOCs), or HOCs and heavy metal mixed contaminants, by EK treatment in large scale with the use of HPCD.

Improved simultaneous enantioseparation of beta-agonists in CE using beta-CD and ionic liquids.

In this study, approaches to improve chiral resolutions in simultaneous enantioseparation of beta-agonists by CE via a CD inclusion complexation modified with ionic liquids (ILs) are described. Different types of ILs, including tetraalkylammonium-based ILs, alkylimidazolium-based ILs and alkylpyridinium-based ILs, were examined and compared for controlling the EOF in order to improve resolutions of beta-agonists enantiomers. In this regard, tetraalkylammonium-based ILs were more effective because they could be used at much higher concentrations than other types of ILs. N-octylpyridinium hexafluorophosphate gave poor resolutions of beta-agonists enantiomers. In addition, when different ILs were mixed to use, they would present particular properties of their own. Moreover, the presence of ILs was essential in the chiral separations of (+/-) salbutamol, (+/-) cimaterol and (+/-) formoterol, which were reportedly not enantioseparated by using the buffer electrolytes containing only beta-CD as a chiral selector.

Method of creating a nanopore-terminated probe for single-molecule enantiomer discrimination.

Nanopores are increasingly utilized as tools for single-molecule detection in biotechnology. Many nanopores are fabricated through procedures that require special materials, expensive facilities and experienced operators, which limit their usefulness on a wider scale. We have developed a simple method of fabricating a robust, low-noise nanopore by externally penetrating a nanocavity enclosed in the terminal of a capillary pipet. The nanocavity was shown to have a pore size on the scale of a single molecule, verified by translocation of molecules of known sizes, including double-stranded DNA (2 nm), gold nanoparticles (10 nm), and ring-shaped cyclodextrin (1.5 nm). The small pore size allows entrapment of a single cyclodextrin molecule. The glass nanopore with a trapped cyclodextrin proves useful in single-molecule discrimination of chiral enantiomers.

Inclusion complex-based solid-phase extraction of steroidal compounds with entrapped beta-cyclodextrin polymer.

Although the hydrophobic interaction-based solid-phase extraction (SPE) has been widely used, the extraction yields of steroids including androgens, estrogens, and corticoids were slightly different along with the physical and chemical properties of each molecule. A new SPE technique based on the formation of an inclusion complex with beta-cyclodextrin (betaCD) has been achieved for comprehensive sample purification in mass spectrometric analysis of 45 endogenous or synthetic androgens, 11 endogenous estrogens, and 21 corticoids. A copolymer of betaCD with epichlorohydrin was prepared by a cross-linking reaction followed by entrapment with 0.3M CaCl(2) to yield an improved SPE sorbent and the hydrolyzed urine samples were applied for purification. Steroidal compounds tested on the entrapped betaCD polymer were extracted with tetrahydrofuran and the overall recoveries ranged from 82% to 112% for 77 steroids in urine. Especially, the hydroxylated estrogens showed an excellent binding capacity (96-116% recovery) to betaCD through hydrogen bonding between their phenolic hydroxyl and exterior hydroxyl groups. A comparison between SPE methods with betaCD and Oasis HLB as a conventional cartridge showed that the extraction efficiency of polar steroids was significantly increased in the betaCD experiment, which has no connection with different polarity of steroid molecules. Due to its multi-functional mechanism derived from molecular inclusion and chemical interactions, this new SPE sorbent resulted in better selectivity and extraction efficiency than that obtained using the conventionally used hydrophobicity-based SPE method.

Chiral separability of hydrophobic boron cluster anions with native cyclodextrins in water-methanol background electrolytes.

Cluster anions of boron are built up on three-center two-electron bonds in contrast to naturally occurring compounds and their synthetic analogs. Methanol works as a solvent and as a competing agent, which advantageously adjusts reasonable strength of their interaction with native CDs in water-organic BGE. The highest methanol concentration preserving chiral discrimination of atropoisomers of individual anions is approximately 35, 55 and 75% v/v for alpha-, beta- and gamma-CD, respectively. alpha-CD separates anionic 7, 8-nido-dicarbaundecaborate clusters with small exo-skeletal substituents. beta-CD separates anions of all four tested structural types. The efficiency of separation of a compound with alpha- or beta-CD is always markedly lower than the separation efficiency at the absence of a CD in BGE. The efficiency of separation of a compound with beta-CD is always lower than the efficiency of separation of the compound with alpha-CD. gamma-CD was proved to be unsuitable as a chiral selector because in BGEs with gamma-CD, effective mobilities of analytes as well as their differences continuously decrease. The decrease was ascribed to the decomposition of the gamma-CD. The assessment of analytical prospect of alpha- and beta-CDs as chiral selectors for chiral separations of boron cluster anions requires knowledge of stability of individual CDs at the conditions of analyses and recognition of the chance to eliminate low separation efficiency.

Physicochemical and biological properties of 6(1),6(3),6(5)-tri-O-alpha-maltosyl-cyclomaltoheptaose (6(1),6(3),6(5)-tri-O-alpha-maltosyl-beta-cyclodextrin).

A unique multibranched cyclomaltooligosaccharide (cyclodextrin, CD) of 6(1),6(3),6(5)-tri-O-alpha-maltosyl-cyclomaltoheptaose [6(1),6(3),6(5)-tri-O-alpha-maltosyl-beta-cyclodextrin, (G(2))(3)-betaCD] was prepared. The physicochemical and biological properties of (G(2))(3)-betaCD were determined together with those of monobranched CDs (6-O-alpha-D-glucopyranosyl-alpha-cyclodextrin (G(1)-alphaCD), 6-O-alpha-D-glucopyranosyl-beta-cyclodextrin (G(1)-betaCD), and 6-O-alpha-maltosyl-beta-cyclodextrin (G(2)-betaCD)). NMR spectra of (G(2))(3)-betaCD were measured using various 2D NMR techniques. The solubility of (G(2))(3)-betaCD in water and MeOH-water solutions was extremely high in comparison with nonbranched betaCD and was about the same as that of the other monobranched betaCDs. The formation of an inclusion complex of (G(2))(3)-betaCD with stereoisomers (estradiol, retinoic acid, quinine, citral, and glycyrrhetinic acid) depends on the cis-trans isomers of guest compounds. The cis isomers of estradiol, retinoic acid, and glycyrrhetinic acid were included more than their trans isomers, while the trans isomers of citral and quinine fit more tightly than their cis isomers. (G(2))(3)-betaCD was the most effective host compound in the cis-trans resolution of glycyrrhetinic acid. Among the branched betaCDs, (G(2))(3)-betaCD exhibited the weakest hemolytic activity in human erythrocytes and showed negligible cytotoxicity in Caco-2 cells up to 200 microM. These results indicate unique characteristics of (G(2))(3)-betaCD in some biological responses of cultured cells.

Effect of alkylimidazolium substituents on enantioseparation ability of single-isomer alkylimidazolium-beta-cyclodextrin derivatives in capillary electrophoresis.

A family of 6-mono(3-alkylimidazolium)-beta-cyclodextrins with one primary hydroxyl group replaced by an alkylimidazolium cation has been developed. The effect of alkyl substitutents on the enantioresolution ability of these single-isomer cyclodextrins towards dansyl amino acids has been studied by capillary electrophoresis. Systematical investigations on the effect of buffer pH and selector concentration on the enatioseparation show that chiral selectors with a shorter alkyl chain (R=C(n)H(2n+1), n

A proposed mechanism for detergent-assisted foam fractionation of lysozyme and cellulase restored with beta-cyclodextrin.

Foam fractionation by itself cannot effectively concentrate hydrophilic proteins such as lysozyme and cellulase. However, the addition of a detergent to a protein solution can increase the foam volume, and thus, the performance of the foam fractionation process. In this article, we propose a possible protein concentration mechanism of this detergent-assisted foam fractionation: A detergent binds to an oppositely charged protein, followed by the detergent-protein complex being adsorbed onto a bubble during aeration. The formation of this complex is inferred by a decrease in surface tension of the detergent-protein solution. The surface tension of a solution with the complex is lower than the surface tension of a protein or a detergent solution alone. The detergent can then be stripped from the adsorbed protein, such as cellulase, by an artificial chaperone such as beta-cyclodextrin. Stripping the detergent from the protein allows the protein to return to its original conformation and to potentially retain all of its original activity following the foam fractionation process. Low-cost alternatives to beta-cyclodextrin such as corn dextrin were tested experimentally to restore the protein activity through detergent stripping, but without success.