Concentration Of Α-cyclodextrin Research Articles

Calorimetric studies of α-cyclodextrin inclusion complexes with carbendazim and thiabendazole

ABSTRACT Calorimetric titration studies of carbendazim and thiabendazole solutions with α-cyclodextrin solutions were performed. The study involved the determination stoichiometry of the resulting inclusion complexes, their formation constant values and thermodynamic parameters (molar enthalpy and molar entropy) characterising the ligand-receptor complexes. The ITC calorimetric measurements were supplemented with UV–VIS spectroscopic measurements to determine the increase in the water solubility of test fungicides in the presence of increasing concentration of α-cyclodextrin.

Eco-Friendly Tadalafil Surfactant-Free Dry Emulsion Tablets (SFDETs) Stabilized by In Situ Self-Assembled Aggregates of Natural Oil and Native Cyclodextrins.

The main principles of green chemistry and engineering were extended to pharmaceutical formulations to prepare eco-friendly surfactant-free dry emulsion tablets (SFDETs) devoid of solvents or synthetic surfactants. Surfactant-free emulsions were stabilized by in situ cyclodextrins/sweet almond oil inclusion complexes and assessed for creaming stability. Formulation variables' effects on the emulsion droplet size and tadalafil solubility were studied using 22 × 3 factorial design. The emulsions exhibited nanometric and micrometric droplet sizes. The optimized nanoemulsion was loaded with tadalafil, morphologically evaluated, and utilized for preparing lyophilized SFDETs using different gelatin/Pearlitol® ratios. The tablets were characterized and the selected formulation was subjected to storage for 6months. The emulsions prepared using β-cyclodextrin or higher concentrations of α-cyclodextrin showed little or no phase separation. Statistical analysis revealed significant influence of cyclodextrin type and amount on droplet size, while cyclodextrin type and oil volume exhibited significant effect on drug solubility. Morphological examination revealed non-aggregated spherical emulsion droplets. The prepared tablets showed satisfactory mechanical strength, short disintegration times, and enhanced drug dissolution. The selected tablet formulation (gelatin/Pearlitol®, 4:2 w/w) showed acceptable stability at 25°C/60% relative humidity. An overall conclusion claims that the absence of surfactants is expected to minimize the proposed tablets' in vivo toxicity and environmental concerns.

Enhanced enantioselectivity of native α‐cyclodextrins by the synergy of chiral ionic liquids in capillary electrophoresis

In the cyclodextrins family, the native α-cyclodextrin has almost been abandoned in capillary electrophoresis chiral separation due to its much weaker enantioselectivity compared with β-cyclodextrin and their derivatives. In this work, several amino acid chiral ionic liquids were selected to establish synergistic enantioseparation systems with native α-cyclodextrin. Enhanced enantioselectivities were observed in the chiral ionic liquids/α-cyclodextrin synergistic systems compared with single α-cyclodextrin system. A series of comparison experiments were performed to demonstrate the superiority of the synergistic systems. Primary parameters affecting the enantioseparation were systematically optimized, including the type and concentration of chiral ionic liquids, α-cyclodextrin concentration, buffer pH, and applied voltage. Best separations of the model enantiomers were obtained in a 20mM Tris/H3 PO4 buffer at pH 2.5 containing 3% (m/v) α-cyclodextrin and 30mM tetramethylammonium-l-arginine. The results show that the α-cyclodextrin is also worth our attention when selecting chiral selectors for capillary electrophoresis enantioseparation of specific racemic compound.

Inhibitory effect of α-cyclodextrin on α-amylase activity

Purpose : To explore the effect of α-cyclodextrin on the activity of α-amylase with a view to expanding its application range. Methods : The concentration of α-cyclodextrin, temperature, pH and interaction time were used as single factors to explore the influence of α-cyclodextrin on the activity of α-amylase and endogenous fluorescence in the enzyme system. Results : The results showed that the concentration, time, pH and temperature affect the interaction of them. The most obvious conditions for inhibition of α-amylase activity are as follows: 10 mmol/L concentration of α-cyclodextrin, pH 6.9, duration of 120 min and temperature at 55 oC. In addition, the fluorescence intensity of α-amylase changed as a result of the addition of α-cyclodextrin. Conclusion : The activity of α-amylase can be inhibited by α-cyclodextrin. At the same time, the addition of α-cyclodextrin will lead to the transfer of tryptophan group in α-amylase, which cause the change of microenvironment and changes the endogenous fluorescence intensity of α-amylase. Keywords : α-Cyclodextrin, α-Amylase, Fluorescence intensity, Inhibition

Hierarchical supramolecular platelets from hydrophobically-modified polysaccharides and α-cyclodextrin: Effect of hydrophobization and α-cyclodextrin concentration on platelet formation

Micro- and nano-platelets are a group of particles with typical flat surfaces and hexagonal shape. They are obtained by hierarchical self-assembly in water of α-cyclodextrin and polysaccharides hydrophobically-modified with alkyl chains. It is expected that the formation of well structured and cohesive platelets is driven by the interaction between alkyl chains grafted on polysaccharides and α-cyclodextrin. The objective of this investigation is to tune platelet formation by modifying these two parameters, independently on polysaccharide composition. A systematic study was conducted by varying polysaccharide type (dextran, pullulan, amylopectin), degree of substitution (DS:0.1–5.6%) and α-cyclodextrin concentration (0–10 wt%) for a fixed concentration of polysaccharide esterified with palmitoyl groups (1 wt%). Characterizations include ATR-FTIR, elemental analysis, solid state 13C NMR and transmission electron microscopy. Abundant and well-organized hexagonal platelets were obtained with high DS (4.2–5.6%) and a concentration of α-cyclodextrin higher than 2.5 wt%. Isothermal titration calorimetry revealed a sequential binding with a stoichiometry of 2 α-cyclodextrin molecules for 1 palmitoyl group grafted on dextran. This is the first report showing the possibility to control platelet formation by modifying DS and α-cyclodextrin concentration, independently on polysaccharide composition.

Validation of a Capillary Electrophoresis Assay for Monitoring Iodine Nutrition in Populations for Prevention of Iodine Deficiency: An Interlaboratory Method Comparison.

A capillary electrophoresis (CE) assay was recently introduced as a new method for monitoring iodine nutrition in large-scale epidemiological studies. However, further tests revealed unanticipated matrix-dependent interferences when analyzing submicromolar levels of iodide in human urine as the predominate ionic form of dietary iodine. Herein, we describe a rigorous validation study that was used to identify sources of bias and establish modifications to the original CE method to improve method accuracy. An interlaboratory method comparison using CE with UV detection and inductively coupled plasma-mass spectrometry (ICP-MS) was performed to quantify urinary iodide concentrations (n = 71) independently at McMaster University and Hamilton General Hospital, as well as the CDC as part of their quality assurance program. A positive bias in the original CE method was indicated, and buffer conditions were subsequently optimized to overcome matrix interferences for reliable iodine status determination. Positive bias in CE was attributed to variable concentrations of sulfate, a major urinary anion interference with similar mobility to iodide under the conditions originally reported. By increasing the concentration of α-cyclodextrin in the background electrolyte, the CE method was able to tolerate urinary sulfate over its normal physiological range without loss in signal response for iodide. The optimized CE assay generated results that were consistent with ICP-MS using 2 different internal standards (187Re and 130Te) with a median bias under 10%. CE offers a simple, selective, and cost-effective separation platform for surveillance of the iodine status of a population requiring only small volumes (<10 μL) of biobanked urine specimens, which is comparable to previously validated screening methods currently used in global health initiatives for prevention of iodine deficiency disorders.

Sustained drug delivery system for insulin using supramolecular hydrogels composed of tri-block copolymers

Formulating a polypeptide gastrointestinal drug delivery system have been persistent challenges. To overcome these challenges, in situ-forming gels are more attractive because of their biodegradability and easy preparation and administration. In this study, biodegradable triblock copolymer polycaprolactone–polyethylene glycol–polycaprolactone [PCL–PEG–PCL (PCEC)] was synthesized under microwave irradiation and their gelation with different concentrations of α-cyclodextrin (CD) was investigated. PCEC was characterized by 1HNMR and gel permeation chromatography. The hydrogel and copolymer were also evaluated using differential scanning colorimetery, X-ray diffraction study and scanning electron microscopy. Also rheological properties were investigated. Four different concentrations of hydrogels consisting of the copolymer [5 and 7.5% (w/w)] and α-CD [10 and 14% (w/w)] were studied to evaluate insulin cumulative release profiles during 37 days. Finally, CD spectrum and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) tests were performed to approve the stability of released insulin. It was demonstrated that the synthesis of PCEC via microwave irradiation was fast and efficient. Copolymer and α-CD concentrations are important in forming supramolecular hydrogels. Rheographs indicated the injectability and thixotropic behavior. In vitro release studies affirmed the sustained release profile of insulin. Both polymer degradation and drug diffusion are involved in it. Results of stability tests confirmed the stability of insulin following release.

Evaluation of the Cytotoxicity of α-Cyclodextrin Derivatives on the Caco-2 Cell Line and Human Erythrocytes.

Cyclodextrins, even the 6-membered α-cyclodextrin, are approved in the various pharmacopoeias as pharmaceutical excipients for solubilizing and stabilizing drugs as well as for controlling drug release. Recently α-cyclodextrin has also been marketed as health food with beneficial effects on blood lipid profiles. However, the concentration of α-cyclodextrin used may be very high in these cases, and its toxic attributes have to be seriously considered. The objective of this study was to investigate the cytotoxicity of various, differently substituted α-cyclodextrin derivatives and determine relationship between the structures and cytotoxicity. Three different methods were used, viability tests (MTT assay and Real Time Cell Electronic Sensing on Caco-2 cells) as well as hemolysis test on human red blood cells. The effect of α-cyclodextrin derivatives resulted in concentration-dependent cytotoxicity, so the IC50 values have been determined. Based on our evaluation, the Real Time Cell Electronic Sensing method is the most accurate for describing the time and concentration dependency of the observed toxic effects. Regarding the cytotoxicity on Caco-2 cells, phosphatidylcholine extraction may play a main role in the mechanism. Our results should provide help in selecting those α-cyclodextrin derivatives which have the potential of being used safely in medical formulations.

Hexagonal-shaped chondroitin sulfate self-assemblies have exalted anti-HSV-2 activity

The initial step in mucosal infection by the herpes simplex virus type 2 (HSV-2) requires its binding to certain glycosaminoglycans naturally present on host cell membranes. We took advantage of this interaction to design biomimetic supramolecular hexagonal-shaped nanoassemblies composed of chondroitin sulfate having exalted anti-HSV-2 activity in comparison with native chondroitin sulfate. Nanoassemblies were formed by mixing hydrophobically-modified chondroitin sulfate with α-cyclodextrin in water. Optimization of alkyl chain length grafted on chondroitin sulfate and the ratio between hydrophobically-modified chondroitin sulfate and α-cyclodextrin showed that more cohesive and well-structured nanoassemblies were obtained using higher α-cyclodextrin concentration and longer alkyl chain lengths. A structure-activity relationship was found between anti-HSV-2 activity and the amphiphilic nature of hydrophobically-modified chondroitin sulfate. Also, antiviral activity of hexagonal nanoassemblies against HSV-2 was further improved in comparison with hydrophobically-modified chondroitin sulfate. This work suggests a new biomimetic formulation approach that can be extended to other heparan-sulfate-dependent viruses.

Thermodynamic studies of drug–α-cyclodextrin interactions in water at 298.15 K: Procaine hydrochloride/lidocaine hydrochloride/tetracaine hydrochloride/ranitidine hydrochloride + α-cyclodextrin + H2O systems

The osmotic coefficient measurements have been carried out for ternary aqueous solutions containing a fixed concentration of α-cyclodextrin (α-CD) of ∼0.1mol·kg−1 and varying the concentrations (∼0.012 to ∼0.21mol·kg−1) of drugs Procaine hydrochloride (PC·HCl), Lidocaine hydrochloride (LC·HCl), Tetracaine hydrochloride (TC·HCl) and Ranitidine hydrochloride (RT·HCl) at 298.15K using vapour pressure osmometry. The water activities for each ternary system were measured and used to obtain the activity coefficients of α-cyclodextrin (α-CD) and drugs following the methodology developed by Robinson and Stokes for isopiestic measurements. The transfer Gibbs free energies of electrolyte (or drug) from water to an aqueous nonelectrolyte (α-CD) solutions (ΔGtrE) and that of nonelectrolyte (α-CD) from water to an aqueous electrolyte (or drug) solutions (ΔGtrN) have been calculated using the activity data. These were further used for the estimation of pair and triplet interaction parameters. By applying the method based on the application of the McMillan–Mayer theory of virial coefficients to transfer free energy data, the salting constant (ks) values have been estimated at 298.15K. The equilibrium constant (logK) values for the complexation due to host–guest interaction are found high meaning encapsulation of drug molecules in α-CD cavities accompanied by pair-wise and triplet interaction due to hydrophobic hydration and interaction. The logK values are in the order of TC·HCl>RT·HCl>PC·HCl>LC·HCl. All these results are presented, compared and explained in light of host–guest interaction concepts.

Cyclodextrin-Mediated Enhancement of Riboflavin Solubility and Corneal Permeability

Cyclodextrins are water-soluble cyclic oligosaccharides consisting of six, seven, and eight α-(1,4)-linked glucopyranose subunits. This study reports the use of different cyclodextrins in eye drop formulations to improve the aqueous solubility and corneal permeability of riboflavin. Riboflavin is a poorly soluble drug with a solubility up to 0.08 mg mL(-1) in deionized water. It is used as a drug topically administered to the eye to mediate UV-induced corneal cross-linking in the treatment of keratoconus. Aqueous solutions of β-cyclodextrin (10-30 mg mL(-1)) can enhance the solubility of riboflavin up to 0.12-0.19 mg mL(-1), whereas the higher concentration of α-cyclodextrin (100 mg mL(-1)) achieved a lower level of enhancement of 0.11 mg mL(-1). The other oligosaccharides were found to be inefficient for this purpose. In vitro diffusion experiments performed with fresh and cryopreserved bovine cornea have demonstrated that β-cyclodextrin enhances riboflavin permeability. The mechanism of this enhancement was examined through microscopic histological analysis of the cornea and is discussed in this paper.

Chemometrics-guided development of a cyclodextrin-modified micellar electrokinetic chromatography method with head-column field amplified sample stacking for the analysis of 5-lipoxygenase metabolites

A new sensitive method using α-cyclodextrin-modified micellar electrokinetic chromatography has been developed to separate and quantify arachidonic acid metabolites of the lipoxygenase pathways in human polymorphonuclear leukocytes, i.e. leukotriene B4, 6-trans-leukotriene B4, 6-trans-12-epi-leukotriene B4, 5(S)-hydroxy-6-trans-8,11,14-cis-eicosatetraenoic acid, 12(S)-hydroxy-6-trans-8,11,14-cis-eicosatetraenoic acid, and 15(S)-hydroxy-6-trans-8,11,14-cis-eicosatetraenoic acid. The electrophoresis system was optimized with regard to the pH, boric acid, SDS and α-cyclodextrin concentration as well as separation voltage and temperature using a three level resolution IV fractional factorial design and a five level circumscribed central composite design. The resulting optimized conditions included 80mM sodium borate buffer, pH 10.07, containing 16.6mM sodium dodecyl sulfate, and 15mM α-cyclodextrin, using a separation voltage of 12.5kV at 23°C. Sensitivity was enhanced employing head-column field amplified sample stacking which resulted in limits of quantification between 30 and 50ng/mL and limits of detection between 10 and 17ng/mL after solid phase extraction of the lipoxygenase products. The method was validated according to the recommendations of the International Conference on Harmonization and applied to the determination of the lipoxygenase metabolites in polymorphonuclear leukocytes upon stimulation with Ca2+-ionophore A23187 and arachidonic acid. Robustness was confirmed using a three level resolution IV fractional factorial design. The novel method is suitable for the analysis of various arachidonic acid metabolites produced by cells and may be used for evaluation of lipoxygenase inhibitors.

Activity Coefficient Studies in Ternary Aqueous Solutions at 298.15 K: H2O + α-Cyclodextrin + Potassium Acetate and H2O + 18-Crown-6 + Hydroquinone Systems

Activity coefficients of the components in aqueous ternary solutions containing a fixed concentration of α-cyclodextrin and 18-crown-6 at various concentrations of the third solutes potassium acetate and hydroquinone, respectively (concentration range (0.0 to 0.20) mol·kg−1), at 298.15 K were derived from vapor pressure osmometry. Also, data for the osmotic coefficients and activity coefficients for aqueous binary solutions of potassium acetate are obtained and used along with the data for aqueous binary hydroquinone solutions reported earlier to analyze the data of the ternary mixtures. It is observed that there is a lowering of activity coefficients of potassium acetate as well as of hydroquinone in the presence of α-cyclodextrin and 18-crown-6, respectively, which is being attributed to incorporation of the acetate ion and hydroquinone into the α-cyclodextrin and 18-crown-6 cavities, respectively, to form 1:1 inclusion complexes in the solution phase. The salting-in and thermodynamic equilibrium consta...

Activity Coefficient Studies in Ternary Aqueous Solutions at 298.15 K: H2O + α-Cyclodextrin + Potassium Acetate and H2O + 18-Crown-6 + Hydroquinone Systems

Activity coefficients of the components in aqueous ternary solutions containing a fixed concentration of α-cyclodextrin and 18-crown-6 at various concentrations of the third solutes potassium acetate and hydroquinone, respectively (concentration range (0.0 to 0.20) mol·kg−1), at 298.15 K were derived from vapor pressure osmometry. Also, data for the osmotic coefficients and activity coefficients for aqueous binary solutions of potassium acetate are obtained and used along with the data for aqueous binary hydroquinone solutions reported earlier to analyze the data of the ternary mixtures. It is observed that there is a lowering of activity coefficients of potassium acetate as well as of hydroquinone in the presence of α-cyclodextrin and 18-crown-6, respectively, which is being attributed to incorporation of the acetate ion and hydroquinone into the α-cyclodextrin and 18-crown-6 cavities, respectively, to form 1:1 inclusion complexes in the solution phase. The salting-in and thermodynamic equilibrium constant values have been determined using calculated transfer free energies and the method based on application of the McMillan−Mayer virial coefficient theory for solutions. It is noted that the complexation process is assisted by hydrophobic interaction between the complexed species. The apparent molar volume and calculation of virial coefficient for potassium acetate in binary aqueous solutions at 298.15 K are also reported and discussed.

Activity and activity coefficient studies of aqueous binary and ternary solutions of 4-nitrophenol, sodium salt of 4-nitrophenol, hydroquinone and α-cyclodextrin at 298.15 K

Osmotic coefficient measurements are reported for binary aqueous solutions of 4-nitrophenol, sodium salt of 4-nitrophenol and hydroquinone at 298.15 K. The data are analyzed to obtain activities and activity coefficients of solute as a function of solute concentration using appropriate thermodynamic equations and methods of integration. The measurements of solvent activity are made for ternary aqueous solutions containing fixed concentration of α-cyclodextrin (α-CD) and varying amount of 4-nitrophenol, sodium salt of 4-nitrophenol and hydroquinone. The solvent activity data have been used to obtain the individual activity coefficients of the components as a function of solute concentration at 298.15 K. It is observed that there is a lowering of activity coefficients of the phenols as well as of hydroquinone in presence of α-CD, which is being attributed to incorporation of these solute molecules into the CD cavity to form inclusion complexes. The salting-in constant and thermodynamic equilibrium constant values for the formation of 1:1 complexes have been determined using Dagade and Patil's method based on the application of the McMillan–Mayer virial coefficient theory. The results are further discussed in terms of neutral and anionic complex formation, water structural effects and hydrophobic interactions.

Biochemical study of CymJ, the putative regulator of cyclodextrin metabolism in Klebsiella oxytoca M5a1

The products of ten genes clustered in two divergently oriented operons are required for the metabolism of cyclic oligoglucosides, the cyclodextrins, by Klebsiella oxytoca. The function of CymJ, the product of the promoter distal gene in one of the operons was studied. Over expression of cymJ in K. oxytoca led to strong reduction of the expression of the cym operons. This repression could be alleviated by addition of high concentration of α-cyclodextrin into the medium. There is a possible relationship between CymJ and CymD since the absence of CymD in a CymD deletion mutant prevented the repression effect of CymJ. An intriguing finding was that the presence of CymJ in large amount in the cell caused severe cell division inhibition leading to retardation of growth. This morphological change was paralleled by a significant increase in the susceptibility of K. oxytoca to ampicillin. (Med J Indones 2007; 16:69-77) Keywords: cym operon, putative regulator, over expression

Direct Determination of Barbiturates in Urine by Capillary Electrophoresis Using a Capillary Coated Dynamically with Polycationic Polymers

A new, simple and rapid capillary electrophoresis method, using hexadimethrine bromide (HDB) as electro-osmotic flow modifier, has been developed for the identification and determination of nine barbiturates, barbital acid, barbital, phenobarbital, pentobarbital, amobarbital, thiobarbituric acid, butobarbital, N-methyl-5-phenyl-ethyl barbital acid and 5-cyclohexenyl-5-ethyl barbital acid in urine with UV detection at 200 nm. The applied voltage was -25 kV and the capillary temperature was kept constant at 25 °C. The effects of buffer pH, the concentration of HDB and the concentration of α-cyclodextrin were studied systematically. Optimum separation was achieved with 20 mM borate buffer at pH 10.00 containing 0.04% (w/v) HDB and 2.06 mM α-cyclodextrin. Regression equations revealed good linear relationship between the peak area of each compound and its concentration. The correlation coefficients were from 0.9990 to 0.9997. The relative standard deviations of migration times and peak areas were <3.84 and 5.45% (intra-day). The nine barbiturates in urine were successfully determined within 7 min, without a prior preparation step and the method is useful for the investigation of intoxication.

Interactions between anionic mixed micelles and α-cyclodextrin and their inclusion complexes: conductivity, NMR and fluorescence study

Mixed micelle formation of anionic surfactants sodium dodecyl sulfate (SDS) and sodium lauroyl sarcosine (SLAS) have been studied in water and in 5, 10, and 15 mM concentrations of α-cyclodextrin (α-CD) over mole fraction range of αSDS from 0 to 1. From the conductivity curves, the critical micellar concentration (CMC) for the pure and binary mixtures were evaluated. The degree of counterion association (χ) or counterion dissociation (δ), the equivalent ionic conductivities of the monomeric species (Λm), the associated species (Λassc), and the micelle (Λmic) were evaluated from the slope of the conductivity vs concentration plots. The CMC values have been used to calculate the thermodynamic parameters such as the standard free energy of micelle formation \(\Delta G^{{\rm{0}}}_{{{\rm{mic}}}}\) and a transfer of standard free energy of micelle \({\left( {\Delta G^{{\text{0}}}_{{{\rm{M,tr}}}} } \right)}\) from the aqueous medium to additive medium computed. The apparent CMC of the surfactants varies linearly with α-CD concentrations. From the dependence of CMC of the surfactants on α-CD concentration, we are able to determine the association constant (K) of surfactant-α-CD inclusion complexes assuming 1:1 stoichiometry. Mixed micelle behaves ideally in the pure water as well as at the different concentrations of α-CD, which was evaluated by using the Clint equation, the regular solution approximation, and Motomura’s formulation. Self-diffusion coefficients of the micelle increased upon the induction of SDS into the micelle. 2D-rotating frame Overhauser effect spectroscopy spectra of SDS and SLAS were recorded in the presence of α-CD to investigate the interaction between H-atoms of the alkyl chain of the surfactants and H-atoms of the hydrophobic cavity of α-CD indicating multiple complexation. The fluorescence anisotropy of rhodamine B has been measured to observe the structural behavior of mixed micelle.

In vitro and in vivo efficacy of α-cyclodextrin for treatment of experimental cryptosporidiosis

The efficacy of α-cyclodextrin against infection by Cryptosporidium parvum was evaluated using in vitro and in vivo models . Cyclodextrins are water-soluble cyclic hexamers of glucose units with hydrophobic cavities capable of solubilizing lipophiles and are widely used as drug excipients in the pharmaceutical industry. The viability of purified C. parvum oocysts, exposed for 30, 60, 90, 120 min and 24 h to different concentrations of α-cyclodextrin (2.5, 5, 7.5, 10, 12.5 and 15%), was evaluated by inclusion or exclusion of two fluorogenic vital dyes and by an excystation technique. Preventive and curative efficacies against cryptosporidial infections, at different doses (2.5 and 5%) and regimes of administration of α-cyclodextrin, were determined in an experimental neonatal mice model. Results of the viability assay showed a decrease in oocyst viability that was associated with an increase in exposure time, for each of the concentrations used. Moreover, a high proportion of nonviable oocysts (81%) was observed when C. parvum oocysts were exposed to α-cyclodextrin (2.5%) for 24 h. The intensity of infection, determined 7 days post-inoculation by examination of intestinal homogenates, was significantly lower ( P<0.05) than in the control litters, for all the assays carried out with α-cyclodextrin. Only 38.8% of the animals became infected when the α-cyclodextrin solution (5%) was administered 2 h before inoculated oocysts, and every 24 h at 1 and 2 days post-inoculation.

α-Cyclodextrin extracts diacylglycerol from insect high density lipoproteins

α-Cyclodextrins are water-soluble cyclic hexamers of glucose units with hydrophobic cavities capable of solubilizing lipophiles. Incubating α-cyclodextrin with high density lipophorin from Manduca sexta or Bombyx mori resulted in a cloudy, turbid solution. Centrifugation separated a pale yellowish precipitate. Thin-layer chromatography analysis of the lipid extract of the precipitate showed that the major lipid was diacylglycerol, while KBr density gradient analysis of the supernatant demonstrated the presence of a lipid-depleted very high density lipophorin. Transfer of diacylglycerol from lipophorin to cyclodextrin was specific to α-cyclodextrin and was not observed with β- or γ-cyclodextrins. pH had no effect on diacylglycerol transfer to α-cyclodextrin. However, the transfer was strongly dependent on the concentration of α-cyclodextrin and temperature. Increasing the concentration of α-cyclodextrin in the incubation mixture was associated with the formation of increasingly higher density lipophorins. Thus, at 20, 30, and 40 mM α-cyclodextrin, the density of B. mori lipophorin increased from 1.107 g/ml to 1.123, 1.148, and 1.181 g/ml, respectively. At concentrations greater than 40 mM, α-cyclodextrin had no further effect on the density of lipophorin. α-Cyclodextrin removed at most 83–87% of the diacylglycerol present in lipophorin. Temperature played an important role in altering the amount of diacylglycerols transferred to α-cyclodextrin. At 30 mM α-cyclodextrin, the amount of diacylglycerol transferred at different temperatures was 50% at 4°C, 41% at 15°C, 20% at 28°C, and less than 3% at 37°C.We propose that diacylglycerol transfers to α-cyclodextrin via an aqueous diffusion pathway and that the driving force for the transfer is the formation of an insoluble α-cyclodextrin–diacylglycerol complex.