Enhancement of rhubarb extract solubility and bioactivity by 2-hydroxypropyl-β-cyclodextrin

Rhubarb is a traditional Chinese medicinal herb, and the ethanolic extract of rhubarb consists of active anthraquinones, which are hydrophobic and have antiproliferative effects on hepatoma cell lines. To increase the aqueous solubility of rhubarb and study the consequent bioavailability, the ethanolic extract of rhubarb was complexed with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), a cyclic oligosaccharide that has a hydrophilic outer surface and a hydrophobic central cavity, to form a rhubarb–HP-β-CD complex. This complex was characterized by performing nuclear magnetic resonance spectroscopy, two-dimensional rotating frame spectroscopy and thin layer chromatography to confirm the inclusion of anthraquinones from rhubarb extract in HP-β-CD (weight ratio of rhubarb extract:HP-β-CD = 1:9). We investigated the effects of complexing rhubarb extract with HP-β-CD on the growth of Huh7 and HepG2 cells by performing cytotoxicity analysis, cellular uptake test, and colony formation assay. Our results showed that complexation of rhubarb extract with HP-β-CD increased the aqueous solubility and bioavailability of rhubarb and thus enhanced its effect on hepatoma cells.     

Increased yield of biotransformation of exemestane with β-cyclodextrin complexation technique

In this study, 6-methylenandrosta-4-ene-3,17-dione and Hydroxypropyl-β-cyclodextrin (HP-β-CD) were used to form a complex, which could be then biotransformed by Arthrobacter simplex ATCC6946 to obtain the antitumor drug exemestane. The complex was analyzed by UV, DSC and TG techniques, while the products were analyzed by HPLC, NMR and MS. These results confirmed that the β-cyclodextrin not only improved the water-solubility of 6-methylenandrosta-4-ene-3,17-dione, but also greatly enhanced the biocompatibility during the biotransformation process. This result may be applied to other precursors which have poor aqueous solubility in the biotransformation processes.     

Influence of hydrophilic polymers on celecoxib complexation with hydroxypropyl β-cyclodextrin

Complexation of celecoxib with hydroxypropyl β-cyclodextrin (HPβCD) in the presence and absence of 3 hydrophilic polymers—polyvinyl pyrrolidone (PVP), hydroxypropyl methylcellulose (HPMC), and polyethylene glycol (PEG)—was investigated with an objective of evaluating the effect of hydrophilic polymers on the complexation and solubilizing efficiencies of HPβCD and on the dissolution rate of celecoxib from the HPβCD complexes. The phase solubility studies indicated the formation of celecoxib-HPβCD inclusion complexes at a 1∶1M ratio in solution in both the presence and the absence of hydrophilic polymers. The complexes formed were quite stable. Addition of hydrophilic polymers markedly enhanced the complexation and solubilizing efficiencies of HPβCD. Solid inclusion complexes of celecoxib-HPβCD were prepared in 1∶1 and 1∶2 ratios by the kneading method, with and without the addition of hydrophilic polymers. The solubility and dissolution rate of celecoxib were significantly improved by complexation with HPβCD. The celecoxib-HPβCD (1∶2) inclusion complex yielded a 36.57-fold increase in the dissolution rate of celecoxib. The addition of hydrophilic polymers also markedly enhanced the dissolution rate of celecoxib from HPβCD complexes: a 72.60-, 61.25-, and 39.15-fold increase was observed with PVP, HPMC, and PEG, respectively. Differential scanning calorimetry and X-ray diffractometry indicated stronger drug amorphization and entrapment in HPβCD because of the combined action of HPβCD and the hydrophilic polymers. Published: September 29, 2006     

Chiral recognition of aromatic compounds by β-cyclodextrin based on bimodal complexation

The chiral recognition of the selected aromatic chiral compounds by native -cyclodextrin (-CD) based on bimodal complexation was studied using a flexible docking algorithm FDOCK. A quantitative empirical free energy relationship model was employed to predict the complex stability constants and the preferred binding modes. The results showed that the calculated complex stability constants are in good agreement with the experimental data. Furthermore, the main force responsible for host-guest complexation is the van der Waals force and the chiral molecules are completely included into the -CD cavity. The chiral recognition for the selected aromatic chiral compounds is the result of the van der Waals force counterbalancing with the other effects, such as the electrostatic interaction and the hydrophobic effect.Figure The favorable structures for the inclusion complexes of (S)_phenylbutyric with -CD. View in the plane normal to the Z-axis. -CD is shown in surface and (S)_phenylbutyric in CPK representation.     

Enhancement of α-cyclodextrin product specificity by enriching histidines of α-cyclodextrin glucanotransferase at remote subsite −6

The industrial use of α-cyclodextrins (α-CDs) has increased because their solubility is higher than those of β-CDs. However, improving the product specificity of α-cyclodextrin glucanotransferases (CGTases) remains unresolved. In this study, three mutants (Y167-deletion, Y167HH, and Y167HHH) were constructed at subsite −6 of α-CGTase to investigate the contribution of amino acid residue 167 to the cyclization ability of α-CD by comparing it with Tyr167His mutant α-CGTase (previously constructed based on the wild-type gene of Bacillus sp. 602-1). As expected, the α:β ratio improved with increasing number of histidine along with residue 167. The Y167HHH mutant had the highest α:β ratio of 13.2 and almost produced single type α-CDs. The Y167HHH mutant enzyme was subsequently purified to homogeneity. The enzymatic properties and the optimal condition of Y167HHH mutant in converting raw starch were also investigated. This study discusses product specificity improvement by inserting specific amino acid residues in the active groove. The results indicate that the histidine-rich mutant α-CGTase possessed better potential in producing α-CDs in an industrial scale.     

The enhancement of the oral bioavailability of γ-tocotrienol in mice by γ-cyclodextrin inclusion

Cyclodextrin (CD) is widely used in the pharmaceutical and nutritional fields to form an inclusion complex with lipophilic compounds for the improvement of their aqueous solubility, stability and diffusibility under physiological conditions. In this study, we investigated the effect of the γ-tocotrienol (γT3) inclusion complex with CD on its oral bioavailability. Five-week-old C57BL6 mice were fed a vitamin E-free diet for 28 days, followed by the oral administration of 2.79 mg of γT3-rich fraction (TRF) extracted from rice bran or the equivalent dose (14.5 mg) of a CD inclusion complex with TRF (TRF/CD). The levels of γT3 in sequentially collected plasma were determined by LC-MS/MS. The pharmacokinetic study revealed that the plasma concentrations of γT3 were increased and peaked at 6 or 3 h after the oral administration of TRF or TRF/CD, respectively (C_max values of 7.9±3.3 or 11.4±4.5 μM, respectively). The area under the curve of plasma γT3 concentration also showed a 1.4-fold increase in the group administered with TRF/CD compared with the TRF-only group. Furthermore, the mice that had received the TRF/CD tended to reduce the endotoxin shock induced by injection with lethal amounts of Escherichia coli lipopolysaccharide, compared with the mice that had received TRF alone. Taken together, our results suggest that the CD inclusion improved γT3 bioavailability, resulting in the enhancement of γT3 physiological activity, which would be a useful approach for the nutrition delivery system.     

Enhancement of enzymatic hydrolysis rate of olive oil in water by dimethyl β-cyclodextrin

Summary The hydrolysis rate of olive oil byCandida cylindracea lipase in an aqueous solution without surfactants can be increased up to 6-fold by the addition of up to 60 mg/ml of dimethyl -cyclodextrin (DMCD).     

α-Chymotrypsin stabilization by chemical conjugation with O-carboxymethyl-poly-β-cyclodextrin

Bovine pancreatic α-chymotrypsin was covalently modified with the O-carboxymethyl poly-β-cyclodextrin (M=1.3×10⁴, 40% COOH groups) using a water-soluble carbodiimide as a coupling agent. The conjugate prepared by this procedure retained high proteolytic and esterolytic activity and contained about 74% carbohydrate by weight of transformed protein. The optimum temperature for α-chymotrypsin was increased by 5 °C after this transformation. The thermostability of the polymer–enzyme adduct was also increased by 5 °C. The conjugate prepared was also more resistant to thermal inactivation at different temperatures, ranging from 45 to 55 °C. Additionally, the modified enzyme was 11-fold more stable at pH 9.0. The direct influence of supramolecular interactions between the hydrophobic amino acid residues located at the surface of the protease and the attached polycyclodextrin moieties on α-chymotrypsin stabilization was demonstrated.     

Development of inclusion complex of brinzolamide with hydroxypropyl-β-cyclodextrin

Glaucoma is an accumulative optic neuropathy resulted from increasing intraocular pressure. Brinzolamide (BRZ) is a kind of carbonic anhydrase inhibitors for glaucoma treatment. In this study, brinzolamide-hydroxypropyl-β-cyclodextrin (BRZ-HP-β-CD) inclusion complex was prepared by solvent evaporation method to improve the solubility of BRZ and enhance the therapeutic effect of BRZ. The formation of the inclusion complex was confirmed by Fourier transform infrared spectroscopy, differential scanning calorimeter and nuclear magnetic resonance spectroscopy. The solubility of BRZ increased about 10-fold after the formation of the BRZ-HP-β-CD inclusion complex. The in vitro corneal accumulative permeability of the inclusion complex increased 2.91-fold compared to the commercial available formulation (AZOPT^®). In addition, BRZ-HP-β-CD inclusion complex (0.5% BRZ) had an equivalent efficiency of lowering intraocular pressure with AZOPT^® (1% BRZ) in vivo. These results identified the BRZ-HP-β-CD inclusion complex might have a promising future as a novel formulation of BRZ for glaucoma treatment.     

Investigation of inclusion complex of cilnidipine with hydroxypropyl-β-cyclodextrin

The objective of this study was to improve the water-solubility and photostability of cilnidipine by complexing it with hydroxypropyl-β-cyclodextrin (HP-β-CD or HP-beta-CD). The interactions of cilnidipine and HP-β-CD were characterized by ultra violet-visible (UV/VIS) spectroscopy, differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier transformation-infrared (FT-IR) spectroscopy and (1)H nuclear magnetic resonance ((1)H NMR) spectroscopy to verify the formation of cilnidipine-HP-β-CD complex inclusion. Moreover, the binding sites in the HP-β-CD structure were also tracked through (1)H NMR spectroscopy analysis. All the characterization information proved the formation of cilnidipine-HP-β-CD inclusion complex, and the results demonstrated the superiority of the inclusion complex in dissolution rates and photostability; in addition, the apparent solubility of cilnidipine was increased more than 10,000-fold in the presence of HP-β-CD. The stability constant (1:1) was found to be 50,116M(-1), suggesting a high tendency of the drug to enter the HP-β-CD cavity. These results identified the cilnidipine-HP-β-CD inclusion complex as an effective new approach to design a novel formulation for pharmaceutical application.     

Enhanced crocetin glucosylation by means of maltosyl-β-cyclodextrin encapsulation

Summary The water-soluble solvent dimethylsulfoxide proved to be inhibitory to the enzymatic glucosylation of crocetin catalyzed by cell-free extracts of saffron (Crocus sativus L.) callus cultures. This problem was circumvented by encapsulating crocetin into maltosyl--cyclodextrin at a 1:3 and a 1:6 ratio which made it possible to carry out the reaction with up to 1,750 and 2,500 M crocetin respectively.     

Stabilization of trypsin by chemical modification with β-cyclodextrin monoaldehyde

The monoaldehyde derivative of -cyclodextrin was attached to trypsin via reductive alkylation with NaBH₄. The thermostability was enhanced from 49.5 °C to 60 °C for modified trypsin. The activation free energy of thermal inactivation at 50 °C was increased by 3.2 kJ mol^–1. The conjugated enzyme retained 100% of its initial activity after 3 h incubation at pH 9.     

Investigation of the inclusion behavior of chlorogenic acid with hydroxypropyl-β-cyclodextrin

The inclusion complexation behavior of chlorogenic acid (CGA) with the hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated in both solution and the solid state by UV-vis and fluorescence spectroscopy, infrared spectroscopy (IR), NMR spectroscopy as well as differential scanning calorimetry (DSC). The experimental results indicate that CGA is able to form an inclusion complex with HP-β-CD. The inclusion complex has a stoichiometry of 1:1 and the formation constant was calculated to be 155.7 M⁻¹. The antioxidant activity of CGA on complexation with HP-β-CD increased as compared to uncomplexed CGA. NMR spectroscopic studies show that the aromatic ring and the vinyl group of CGA are deeply included inside the CD cavity.     

Analytical enantioseparation of N-alkyl drugs by reversed-phase liquid chromatography with carboxymethyl-β-cyclodextrin as mobile phase additive

Carboxymethyl-β-cyclodextrins (CM-β-CDs) with five kinds of degrees of substitution were synthesized and characterized. Analytical enantioseparation of six basic drugs containing N-alkyl groups, including pheniramine, chlorpheniramine, labetalol, propranolol, venlafaxine, and trans-paroxol, was achieved by reversed-phase high-performance liquid chromatography (RP-HPLC) using the synthesized CM-β-CD as chiral mobile phase additives. Key influence factors were optimized, including organic modifier, pH value, CM-β-CD with different degrees of substitution, and concentration of CM-β-CD. The mobile phase was composed of methanol and 10 mmol L⁻¹ of phosphate buffer pH 4.0 containing 10 mmol L⁻¹ of CM-β-CD. Peak resolution for six racemic drugs was gradually increased with an increasing degree of substitution of the synthesized CM-β-CD. The stoichiometric ratio and binding constants for the inclusion complex formed by CM-β-CD and enantiomer were determined, which showed that the stoichiometric ratio for each inclusion complex was 1:1.     

Enhancing purification of α-amylase by superparamagnetic complex with alginate/chitosan/β-cyclodextrin/TPP

The main aim of this study was to synthesize the superparamagnetic nanoparticles coated by alginate/chitosan/β-cyclodextrin to purify α-amylase. Isolated bacteria were identified by morphological, biochemical and taxonomic molecular studies. FTIR- spectrometer, VSM, X-ray instruments and Malvern Zetasizer were used to characterize nanoparticles characteristics. The morphological structures and the elemental composition of the nanoparticles were studied by using FESEM and EDS, respectively. The molecular weight of enzyme was determined using SDS-PAGE, and the enzyme activity detected by zymographic analysis. FTIR studies showed the presence of Fe–O–Fe in the Fe₃O₄ and verified the interaction between chitosan, β-cyclodextrin and alginate. The saturation magnetization for superparamagnetic and coated superparamagnetic nanoparticles was indicated 39 and 1.9?emu?g^?1, respectively. The maximum intensity of the XRD peak indicated the presence of the Fe₃O₄. FESEM and EDS analysis showed that the nanoparticles were regular and spherical in shape and corresponded to the Fe and O elements. Enzyme purification by synthesized nanoparticles was achieved 13.84?U?mg^?1; purification fold of 3.50. The molecular weight of α-amylase was about 22?kDa. The highest activity of α-amylase was observed at 70?°C, pH 9.3 and Ca²⁺-independent. As a conclusion, the coated superparamagnetic nanoparticles showed more applications in enzyme purification comparing to the conventional methods.     

Enhancement of γ-linolenic acid production by Mucor ambiguus with nonionic surfactants

Summary -Linolenic acid (GLA) production by Mucor ambiguus IFO 6742, immobilised in Biomass Support Particles (BSPs), has been investigated in a fluidized-bed fermenter in the presence of nonionic surfactants. In this system, repeated batch cultivation was achieved at higher yield and productivity than by conventional methods, since microbial lipids inlcuding GLA were significantly secreted into the culture broth and/or on the surface of the cell wall.     

Inclusion complexation between baicalein and β-cyclodextrin and the influence of β-cyclodextrin on the binding of baicalein with DNA: a spectroscopic approach

This work deals with the commonly studied cyclic oligosaccharide and gains importance as it is entered on a drug delivering carbohydrate and provides insight into the oligosaccharide complex–biomolecular interaction. The binding of a flavone, baicalein, to β-cyclodextrin and calf thymus DNA is studied. The binding of baicalein to calf thymus DNA in the presence of β-cyclodextrin is analysed using the UV–vis absorption and fluorescence spectroscopy. The mode of binding and structure of the baicalein–β-cyclodextrin complex are reported. The role of the structure and the stoichiometry of the inclusion complex of baicalein–β-cyclodextrin in its influence on DNA binding are analysed.

Highlights

? This paper deals with the binding of a flavone, baicalein to β-cyclodextrin and/or DNA.

? The inclusion complexation between baicalein and β-cyclodextrin is analysed.

? The stoichiometry and the binding strength of the inclusion complex is reported.

? The role of β-cyclodextrin in tuning the binding of baicalein to DNA is emphasized.

? Spectroscopic and docking analysis are used to articulate the results.     

Azaadamantyl nitroxide spin label: complexation with β-cyclodextrin and electron spin relaxation

Abstract

An iodoacetamide azaadamantyl spin label was studied in fluid solution and in 9:1 trehalose:sucrose glass. In 9:1 toluene:CH₂Cl₂ solution at 293 K, the isotropic nitrogen hyperfine coupling is 19.2?G, T₁ is 0.37 µs and T₂ is 0.30–0.35 µs. Between about 80 and 150 K 1/T_m in 9:1 trehalose:sucrose is approximately independent of temperature demonstrating that the absence of methyl groups decreases 1/T_m relative to that which is observed in spin labels with methyl groups on the alpha carbons. Spin lattice relaxation rates between about 80 and 293 K in 9:1 trehalose:sucrose are similar to those observed for other nitroxide spin labels, consistent with the expectation that relaxation is dominated by Raman and local mode processes. Although complexation of the azaadamantyl spin label with β-cyclodextrin slows tumbling in aqueous solution by about a factor of 10, it has little impact on 1/T₁ or 1/T_m in 9:1 trehalose:sucrose between 80 and 293 K.     

Enhancement of mycobactericidal activity of glutaraldehyde with α,β-unsaturated and aromatic aldehydes

Summary Several ,-unsaturated and aromatic aldehydes were evaluated for antimicrobial activity usingMycobacterium bovis as the test strain. Activity of most of the compounds was determined in the presence and absence of 2% glutaraldehyde. Several compounds highly active against this organism, e.g. 2-pentenal, benzaldehyde, ando-phthalaldehyde showed rapid kill of >10⁵ CFU ml^–1 in 5 min. Activity of ,-unsaturated compounds substituted in the ₁ position showed increasing activity with increasing chain length. Of the aromatic aldehydes tested, benzaldehyde andp-dimethylamino benzaldehyde showed little activity alone, but when combined with 2% glutaraldehyde showed increased activity. Substituents added to the benzaldehyde ring (nitro, chloro, methyl, and methoxy) all detracted from the synergism, but still showed increased activity over the activity of 2% glutaraldehyde. The same affect was noted with disubstituted benzaldehyde compounds but not with substitutedo-phthaladehyde (2-formylformaldehyde).