Some physicochemical properties of branched β-cyclodextrins and their inclusion characteristics

Ion mobility mass spectrometry enables the discrimination of positional isomers and the detection of conformers from cyclic oligosaccharides-metals supramolecular complexes

Cyclic oligosaccharides are well known to interact with various metals, able to form supramolecular complexes with distinct sizes and shapes. However, the presence of various isomers in a sample, including positional isomers and conformers, can significantly impact molecular recognition, encapsulation ability and chemical reactivity. Therefore, it is crucial to have tools for deep samples probing and correlation establishments. The emerging ion mobility mass spectrometry (IM-MS) has the advantages to be rapid and sensitive, but is still in its infancy for the investigation of supramolecular assemblies. In the herein study, it was demonstrated that IM-MS is suitable to discriminate several isomers of cyclodextrins (CD)-metals complexes, used as cyclic oligosaccharide models. In this sense, we investigated branched 6-O-α-glucosyl- or 6-O-α-maltosyl-β-cyclodextrins (G1-β-CD and G2-β-CD) and their purely cyclic isomers: CD8 (γ-CD) and CD9 (δ-CD). The corresponding collision cross section (CCS) values were deducted for the main positive singly and doubly charged species. Experimental CCS values were matched with models obtained from molecular modelling. The high mobility resolving power and resolution enabled discrimination of positional isomers, identification of various conformers and accurate relative content estimation. These results represent a milestone in the identification of carbohydrate conformers that cannot be easily reached by other approaches.

Cyclodextrins applied to the treatment of lysosomal storage disorders

Cyclodextrin (CD), a cyclic oligosaccharide, is a pharmaceutical additive that improves the solubility of hydrophobic compounds. Recent research has focused on the potential active pharmaceutical abilities of CD. Lysosomal storage diseases are inherited metabolic diseases characterized by lysosomal dysfunction and abnormal lipid storage. Niemann-Pick disease type C (NPC) is caused by mutations in cholesterol transporter genes (NPC1, NPC2) and is characterized by cholesterol accumulation in lysosomes. A biocompatible cholesterol solubilizer 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was recently used in NPC patients for compassionate use and in clinical trials. HP-β-CD is an attractive drug candidate for NPC; however, its adverse effects, such as ototoxicity, should be solved. In this review, we discuss the current use of HP-β-CD in basic and clinical research and discuss alternative CD derivatives that may outperform HP-β-CD, which should be considered for clinical use. The potential of CD therapy for the treatment of other lysosomal storage diseases is also discussed.

Fine-tuned cholesterol solubilizer, mono-6-O-α-D-maltosyl-γ-cyclodextrin, ameliorates experimental Niemann-Pick disease type C without hearing loss

Niemann-Pick disease type C (NPC) is a fatal disorder with abnormal intracellular cholesterol trafficking resulting in neurodegeneration and hepatosplenomegaly. A cyclic heptasaccharide with different degrees of substitution of 2-hydroxypropyl groups, 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), acts as a strong cholesterol solubilizer and is under investigation for treating this disease in clinical trials, but its physicochemical properties and ototoxicity remain a concern. Here, we evaluated the potential of mono-6-O-α-maltosyl-γ-CD (G2-γ-CD), a single-maltose-branched cyclic octasaccharide with a larger cavity than HP-β-CD, for treating NPC. We identified that G2-γ-CD ameliorated NPC manifestations in model mice and showed lower ototoxicity in mice than HP-β-CD. To investigate the molecular mechanisms of action behind the differential ototoxicity of these CDs, we performed cholesterol solubility analysis, proton nuclear magnetic resonance spectroscopy, and molecular modeling, and estimated that the cholesterol inclusion mode of G2-γ-CD maintained solely the 1:1 inclusion complex, whereas that of HP-β-CD shifted to the highly-soluble 2:1 complex at higher concentrations. We predicted the associations of these differential complexations of CDs with cholesterol with the profile of disease attenuation and of the auditory cell toxicity using specific cell models. We proposed that G2-γ-CD can serve as a fine-tuned cholesterol solubilizer for treating NPC, being highly biocompatible and physicochemically suitable for clinical application.

In Vitro and In Vivo Evaluation of 6-O-α-Maltosyl-β-Cyclodextrin as a Potential Therapeutic Agent Against Niemann-Pick Disease Type C

Niemann-Pick disease Type C (NPC) is a rare lysosomal storage disease characterized by the dysfunction of intracellular cholesterol trafficking with progressive neurodegeneration and hepatomegaly. We evaluated the potential of 6-O-α-maltosyl-β-cyclodextrin (G2-β-CD) as a drug candidate against NPC. The physicochemical properties of G2-β-CD as an injectable agent were assessed, and molecular interactions between G2-β-CD and free cholesterol were studied by solubility analysis and two-dimensional proton nuclear magnetic resonance spectroscopy. The efficacy of G2-β-CD against NPC was evaluated using Npc1 deficient Chinese hamster ovary (CHO) cells and Npc1 deficient mice. G2-β-CD in aqueous solution showed relatively low viscosity and surface activity; characteristics suitable for developing injectable formulations. G2-β-CD formed higher-order inclusion complexes with free cholesterol. G2-β-CD attenuated dysfunction of intercellular cholesterol trafficking and lysosome volume in Npc1 deficient CHO cells in a concentration dependent manner. Weekly subcutaneous injections of G2-β-CD (2.9 mmol/kg) ameliorated abnormal cholesterol metabolism, hepatocytomegaly, and elevated serum transaminases in Npc1 deficient mice. In addition, a single cerebroventricular injection of G2-β-CD (21.4 μmol/kg) prevented Purkinje cell loss in the cerebellum, body weight loss, and motor dysfunction in Npc1 deficient mice. In summary, G2-β-CD possesses characteristics favorable for injectable formulations and has therapeutic potential against in vitro and in vivo NPC models.

The aqueous solubility and thermal stability of α-lipoic acid are enhanced by cyclodextrin

We investigated the effects of various cyclodextrins (CDs) on the aqueous solubility and thermal stability of α-lipoic acid, a compound with low water solubility. α-CD, β-CD, and γ-CD had little effect on the aqueous solubility of α-lipoic acid. In contrast, 6-O-α-maltosyl-CDs increased it in a concentration-dependent manner, 6-O-α-maltosyl-β-CD enhancing solubility the most. The thermal stability of α-lipoic acid in the solid state was improved by the addition of G2-β-CD(®), a commercial product of 6-O-α-maltosyl-β-CD. The thermal stability of α-lipoic acid was also improved by the addition of β-CD. Analysis by differential scanning calorimetry showed that G2-β-CD(®), a mixture of maltosyl-β-CDs, and β-CD efficiently formed complexes with α-lipoic acid. These results suggest that the sizes and shapes of these β-CD compounds are compatible with complexation with α-lipoic acid. Moreover, both the formation of an aqueous complex with G2-β-CD(®) and an insoluble complex with β-CD increased the thermal stability of α-lipoic acid.

Prolongation of intrathecal and sciatic nerve blocks using a complex of levobupivacaine with maltosyl-beta-cyclodextrin in rats

BACKGROUND

We used a cyclodextrin-based drug delivery system, consisting of levobupivacaine complexed with maltosyl-beta-cyclodextrin (G2-beta-CD), in spinal and sciatic nerve blocks in rats to investigate prolongation of the local anesthetic effect.

METHODS

Rats were assigned to four groups (n = 6 in each) and received intrathecally 30 microL of 1% levobupivacaine complexed with 0 (control), 50, 100, or 200 mM of G2-beta-CD. Muscle tone and tail flick latency were studied after intrathecal administration. Four more groups (n = 6) of rats received a sciatic nerve block with 0.5% or 1% levobupivacaine complexed with either 0 or 100 mM of G2-beta-CD. The time course of changes in proprioception, motor function, and nociception after circumferential subcutaneous administration to the sciatic nerve was examined.

RESULTS

With the intrathecal block, all rats stopped tail movement immediately after injection of the local anesthetic. The mean time to recovery of muscle tone with 1% levobupivacaine complexed with 100 mM (80.0 +/- 8.9 min) and 200 mM (91.7 +/- 7.0 min) of G2-beta-CD was significantly longer than that of the control group (38.3 +/- 3.1 min), but tail flick latency was not prolonged. With the sciatic nerve block, all rats were temporarily immobilized after levobupivacaine injection. The anesthetic effects of 0.5% levobupivacaine with 100 mM of G2-beta-CD were twice as long as those for 0.5% levobupivacaine alone, and those of 1% levobupivacaine with 100 mM of G2-beta-CD were 1.4 times longer than those for 1% levobupivacaine alone.

CONCLUSIONS

The complex of levobupivacaine with G2-beta-CD prolonged the anesthetic effect of levobupivacaine in both intrathecal and sciatic nerve blocks in rats.

The customised electronic nebuliser: a new category of liquid aerosol drug delivery systems

Inhalation of aerosols is the preferred route of administration of pharmaceutical compounds to the lungs when treating various respiratory diseases. Inhaled antibiotics, hormones, peptides and proteins are potential candidates for direct targeting to the site of action, thus minimising systemic absorption, dilution and undesired side effects, as much lower doses (as low as a fiftieth) are sufficient to achieve a similar therapeutic effect, compared with oral administration. A quick relief from the symptoms and a good tolerance are the main advantages of aerosol therapy. A new class of electronic delivery device is now starting to enter the market. The eFlow electronic nebuliser (PARI GmbH, Germany) provides improved portability and, in some instances, cuts treatment time to only a fraction of what has been experienced with current nebulised therapy. Drug formulations and the device can be mutually adapted and matched for optimal characteristics to meet the desired therapeutic target. Reformulation of known and proven compounds in a liquid format are commercially attractive as they present a relatively low development risk for potential drug candidates and, thus, have become a preferred pathway for the development of new inhalation products.

Inclusion complexation of lorazepam with different cyclodextrins suitable for parenteral use

The development of a parenteral lorazepam formulation, using cyclodextrins (CDs) as inclusion complexation agents, was investigated. CDs suitable for parenteral injection, i.e., hydroxypropyl-beta-cyclodextrin (HP-beta-CD), hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD), sulfobutylether-7-beta-cyclodextrin (SBE-7-beta-CD), and maltosyl-beta-cyclodextrin (malt-beta-CD) were studied for the possibility to increase the solubility of lorazepam. Lorazepam interacted with all tested CD derivatives and 1:1 complexes are formed. HP-beta-CD exerts the highest solubility improvement, reaching about 6 mg/ml lorazepam in 30% (w/v) CD solution. When using SBE-7-beta-CD or malt-beta-CD only half of that concentration can be dissolved. HP-gamma-CD interacts much less with lorazepam. Parenteral solutions with 4 mg/ml in 30% (w/v) HP-beta-CD solution, with 2 mg/ml in 30% (w/v) SBE-7-beta-CD, and with 2 mg/ml lorazepam in 15% (w/v) HP-beta-CD, were prepared. Sterile filtration of the formulation needs to be applied because of massive degradation of lorazepam during autoclaving. No precipitation is observed after dilution of the different formulations with (physiological) water or with 5% dextrose in water, which proves their suitability for administration with perfusions. The stability of the preparations was investigated in aqueous medium. During the first month, in all solutions more than 90% of lorazepam remained; after 3 months, less than 60% of lorazepam remained in the solutions with 15% (w/v) HP-beta-CD and around 65-70% in the solutions with 30% (w/v) of CDs. Because of this short stability time, the preparations need to be lyophilized.

Phase solubility and structure of the inclusion complexes of prednisolone and 6 alpha-methyl prednisolone with various cyclodextrins

The purpose of this work was to study the inclusion binding interaction of two structurally related steroids, prednisolone and 6alpha-methyl prednisolone with a wide variety of cyclodextrins (CDs), both native (alpha-, beta- and gamma-CD) as well as modified (hydroxypropyl-, sulfobutyl ether-, glucosyl-, and maltosyl-beta-CD and sulfobutyl ether-gamma-CD), and to relate the binding constants to structural differences in the steroids. Phase-solubility diagrams of the steroids with various CDs were obtained. The stability constants (K1:1) revealed that beta-CD formed the strongest complex with prednisolone, followed by gamma-CD. With 6alpha-methyl prednisolone, the stability constants of both beta- and alpha-CD were considerably lower compared with prednisolone. In contrast, gamma-CD formed a stronger complex with 6alpha-methyl prednisolone compared with prednisolone. Derivatives of beta-CD gave slightly altered stability constants compared with native beta-CD. The structures of the complexes between the two guest molecules and native beta-CD were studied by nuclear magnetic resonance spectroscopy. This clearly showed that the introduction of the methyl group led to a different binding geometry of 6alpha-methyl prednisolone compared with prednisolone. Additionally, the nuclear magnetic resonance results indicate the presence of an additional, weaker binding site, which is less populated in prednisolone.

Design and evaluation of cyclodextrin-based drug formulation

The pharmaceutically useful cyclodextrins (CyDs) are classified into hydrophilic, hydrophobic, and ionic derivatives. Because of the multi-functional characteristics and bioadaptability, these CyDs are capable of alleviating the undesirable properties of drug molecules through the formation of inclusion complexes or the form of CyD/drug conjugates. This review outlines the current application of CyDs in design and evaluation of CyD-based drug formulation, focusing on their ability to enhance the drug absorption across biological barriers, the ability to control the rate and time profiles of drug release, and the ability to deliver a drug to a targeted site.

[Pharmaceutical application of cyclodextrins as multi-functional drug carriers]

Owing to the increasingly globalized nature of the cyclodextrin (CyD)-related science and technology, development of the CyD-based pharmaceutical formulation is rapidly progressing. The pharmaceutically useful CyDs are classified into hydrophilic, hydrophobic, and ionic derivatives. Because of the multi-functional characteristics and bioadaptability, these CyDs are capable of alleviating the undesirable properties of drug molecules through the formation of inclusion complexes or the form of CyD/drug conjugates. This review outlines the current application of CyDs in drug delivery and pharmaceutical formulation, focusing on the following evidences. 1) The hydrophilic CyDs enhance the rate and extent of bioavailability of poorly water-soluble drugs. 2) The amorphous CyDs such as 2-hydroxypropyl-beta-CyD are useful for inhibition of polymorphic transition and crystallization rates of drugs during storage. 3) The delayed release formulation can be obtained by the use of enteric type CyDs such as O-carboxymethyl-O-ethyl-beta-CyD. 4) The hydrophobic CyDs are useful for modification of the release site and/or time profile of water-soluble drugs with prolonged therapeutic effects. 5) The branched CyDs are particularly effective in inhibiting the adsorption to hydrophobic surface of containers and aggregation of polypeptide and protein drugs. 6) The combined use of different CyDs and/or pharmaceutical additives can serve as more functional drug carriers, improving efficacy and reducing side effects. 7) The CyD/drug conjugates may provide a versatile means for the constructions of not only colonic delivery system but also site-specific drug release system, including gene delivery. On the basis of the above-mentioned knowledge, the advantages and limitations of CyDs in the design of advanced dosage forms will be discussed.

Study on the inclusion complexes of bromazepam with beta- and beta-hydroxypropyl-cyclodextrins

Solubility enhancement of the water insoluble bromazepam was studied during the formation of its inclusion complexes with beta-cyclodextrin (beta-CD) and beta-hydroxypropyl-cyclodextrin (beta-HP-CD). The phase solubility technique established by Higuchi and Connors and UV-spectrophotometric methods (zero- and second-order derivative approaches) were used to measure the changes introduced in this chemical system. The amount of time, which was necessary to reach equilibrium between inclusion complexes and their free components, was estimated and found equal to 24 h. The study was carried out at (i) pH 7.0 and 25 degrees C and (ii) pH 7.4 and 37 degrees C. The solubility of bromazepam increased linearly as a function of concentration for both beta-and beta-hydroxypropyl-cyclodextrins. Thus, the phase solubility diagrams were classified as of A(L) type in all cases. Under the above-mentioned conditions, the formation constants of the inclusion complexes were calculated and their stoichiometry was evaluated, found in the range of 69-85 M(-1) and 1:1, respectively.

A moderate interaction of maltosyl-alpha-cyclodextrin with Caco-2 cells in comparison with the parent cyclodextrin

The cytotoxicity of maltosyl-alpha-cyclodextrin (G2-alpha-CyD) and maltosyl-beta-cyclodextrin (G2-beta-CyD) toward Caco-2 cells was compared with that of natural alpha-cyclodextrin (alpha-CyD), beta-cyclodextrin (beta-CyD) and gamma-cyclodextrin (gamma-CyD). The degree of increase in cytotoxicity was dependent on the CyD's type and the concentration: the cytotoxicity of CyDs at the same concentration increased in the order of gamma-CyD<G2-beta-CyD<G2-alpha-CyD<<alpha-CyD, although beta-CyD could not be compared to other CyDs because of low solubility in water. Alpha-CyD decreased transepithelial electrical resistance (TEER) and increased the apical-to-basolateral (AP-to-BL) transport of [3H]mannitol, a paracellular transport marker, in a concentration-dependent manner, suggesting that alpha-CyD decreased the integrity of Caco-2 cell monolayers. In addition, alpha-CyD increased the AP-to-BL transport of rhodamine 123, a transcellular transport marker, under the experimental conditions being independent of P-glycoprotein. In contrast, G2-alpha-CyD, G2-betaCyD and gamma-CyD had slight effect on both TEER and the transport of mannitol and rhodamine 123 even at relatively high concentrations up to 150 mM. The inability of G2-alpha-CyD and G2-beta-CyD to effect TEER and the transport of mannitol and rhodamine 123 could be explained by the findings that these maltosylated CyDs released only a small amount of membrane constituents from Caco-2 cell monolayers and interacted only weakly with monolayers composed of L-alpha-dipalmitoylphosphatidylcholine (DPPC) formed on water. These results indicate that G2-alpha-CyD has less cytotoxicity and less disturbing ability toward Caco-2 cell monolayers than alpha-CyD, and G2-beta-CyD has, at least, comparable cytotoxicity to beta-CyD toward them. Thus, from the safety point of view, highly water-soluble G2-alpha-CyD and G2-beta-CyD may be particularly useful in various pharmaceutical formulations.

Improvement of solubility and oral bioavailability of rutin by complexation with 2-hydroxypropyl-beta-cyclodextrin

The object of this study was to enhance the solubility, dissolution rate, and oral bioavailability of rutin by complexation with 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD). The interaction of rutin with cyclodextrins (CyDs) was evaluated by the solubility, and ultraviolet (UV) and circular dichroism (CD) spectrophotometries. The chemical and enzymatic stability of rutin was examined in an alkaline buffer solution and in rat small intestinal homogenates, respectively. Dissolution rates of rutin and its CyD complexes were measured by the dispersed amount method. In vivo absorption studies of rutin after oral administration via conventional tablet containing rutin alone or its beta-CyD complexes was performed on beagle dogs. The stability constants calculated from the phase solubility method increased in the order of HP-gamma-CyD < G2-beta-CyD < beta-CyD < HP-beta-CyD. Spectroscopic studies also revealed that HP-beta-CyD and beta-CyD formed a relatively more stable inclusion complex with rutin. The dissolution rates of rutin increased by the complexation with CyDs in the order of rutin alone < HP-beta-CyD < or = beta-CyD. HP-beta-CyD inhibited the hydrolysis of rutin in the alkaline buffer solution and the small intestinal homogenates of rats, suggesting that HP-beta-CyD may stabilize rutin in a gastrointestinal tract after oral administration. When the tablet containing rutin or its beta-CyD complexes was administered to beagle dogs, the plasma levels of homovanillic acid (HVA) (a major stable metabolite of rutin) after oral administration of HP-beta-CyD complex were much higher than in either that of rutin alone or in its beta-CyD complex. The in vivo absorption study suggests that HP-beta-CyD increased the oral bioavailability of rutin from the gastrointestinal tracts of beagle dogs because of the increase in solubility, faster dissolution rate, and gastrointestinal stability. HP-beta-CyD has a significant advantage with respect to providing high aqueous solubility while maintaining a lack of toxicity in oral pharmaceutical preparations of rutin.

Improvement of subcutaneous bioavailability of insulin by sulphobutyl ether beta-cyclodextrin in rats

The objective of this study was to examine and compare how hydrophilic beta-cyclodextrin derivatives (beta-CyDs) improve the bioavailability of insulin following subcutaneous injection of insulin solution in rats. When insulin solutions in the absence of beta-CyDs were injected into the dorsal subcutaneous tissues of rats, the absolute bioavailability of insulin calculated from plasma immunoreactive insulin (IRI) levels was approximately 50%. When maltosyl-beta-cyclodextrin was added to the solutions, there was no change in the plasma IRI levels and hypoglycaemia compared with those of the insulin-alone solution. Dimethyl-beta-cyclodextrin decreased the bioavailability of insulin, although it increased the maximal concentration of IRI in plasma and the capillary permeability of the fluorescein isothiocyanatedextran 40, a non-degraded permeation marker. When insulin solutions containing sulphobutyl ether-beta-cyclodextrin with a degree of substitution of the sulphobutyl group of 3.9 (SBE4-beta-CyD) were injected, the IRI level rapidly increased and maintained higher IRI levels for at least 8 h. The bioavailability of the insulin/SBE4-beta-CyD system was about twice that of insulin alone and approached 96%. The enhancing effects of SBE4-beta-CyD may be in part due to the inhibitory effects of SBE4-beta-CyDs on the enzymatic degradation and/or the adsorption of insulin onto the subcutaneous tissue at the injection site, although this does not apparently facilitate capillary permeability. These results suggest that SBE4-beta-CyD in aqueous insulin injection for subcutaneous administration is useful for improving the bioavailability and the hence the pharmacological effects of insulin.

Heptakis(2,6-di-O-methyl-3-O-acetyl)-beta-cyclodextrin: A water-soluble cyclodextrin derivative with low hemolytic activity

Acetyl groups were introduced to the hydroxyl groups of heptakis(2, 6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD), and the resulting heptakis(2,6-di-O-methyl-3-O-acetyl)-beta-CyD (DMA-beta-CyD) was evaluated for the inclusion property and hemolytic activity. It was confirmed by means of NMR and mass spectroscopies that in the DMA-beta-CyD molecule, all seven hydroxyl groups at the 3-position were substituted by acetyl groups. Thus, it has the degree of substitution (DS) of 7, whereas DMA4-beta-CyD with the lower substitution (DS 3.8) was a mixture of components with different DS. The aqueous solubility of DMA-beta-CyD was higher than those of beta-CyD, DM-beta-CyD, and heptakis(2,3,6-tri-O-methyl)-beta-CyD (TM-beta-CyD). The hydrophobicity of the whole molecule, assessed from measurements of surface tension, increased in the order of DM-beta-CyD < DMA-beta-CyD < TM-beta-CyD. The half-life of DMA-beta-CyD for hydrolysis in pH 9.5 and 60 degrees C was about 19 h, and there was only slight liberation of acetic acid in rabbit plasma and carboxylesterase (EC 3.1.1.1) at 37 degrees C. DMA-beta-CyD had an inclusion ability similar to that of TM-beta-CyD for p-hydroxybenzoic acid esters with different alkyl chain lengths and an antiinflammatory drug, flurbiprofen, although it was inferior to that of DM-beta-CyD. The hemolytic activity and rabbit muscular irritation of DMA-beta-CyDs were much weaker than those of DM-beta-CyD: no hemolysis was observed even in the presence of 0.1 M DMA-beta-CyD with DS 7. The results suggest that the water-soluble CyD derivative with superior bioadaptability and inclusion ability can be prepared by properly designing substituents at the 3-position and by optimally controlling their degree of substitution.

Pharmaceutical applications of cyclodextrins. III. Toxicological issues and safety evaluation

The objective of this review is to summarize recent findings on the safety profiles of three natural cyclodextrins (alpha-, beta- and gamma-CDs) and several chemically modified CDs. To demonstrate the potential of CDs in pharmaceutical formulations, their stability against non-enzymatic and enzymatic degradations in various body fluids and tissue homogenates and their pharmacokinetics via parenteral, oral, transmucosal, and dermal routes of administration are outlined. Furthermore, the bioadaptabilities of CDs, including in vitro cellular interactions and in vivo safety profiles, via a variety of administration routes are addressed. Finally, the therapeutic potentials of CDs are discussed on the basis of their ability to interact with various endogenous and exogenous lipophiles or, especially for sulfated CDs, their effects on cellular processes mediated by heparin binding growth factors.

Separation and characterization of five positional isomers of trimaltosyl-cyclomaltoheptaose (trimaltosyl-beta-cyclodextrin)

Trace amounts of trimaltosyl-cyclomaltoheptaoses (trimaltosyl-beta-cyclodextrins, trimaltosyl-beta CDs) were found in a mixture of maltosyl-cyclomaltoheptaoses (maltosyl-beta-cyclodextrins, maltosyl-beta CDs) prepared from maltose and cyclomaltoheptaose (beta-cyclodextrin, beta CD) through the reverse action of Klebsiella pneumoniae pullulanase. Five positional isomers of trimaltosyl-beta CD were isolated by high-performance liquid chromatography (HPLC) on a reversed-phase column and a graphitized carbon column. For the structural analysis of 6(1), 6(2), 6(3)-, 6(2), 6(5)-, and 6(1), 6(3), 6(5)-tri-O-maltosyl-beta CDs, an enzymic method using glucoamylolysis, followed by hydrolysis with Bacillus subtilis saccharifying alpha-amylase, was applied. Although 6(1), 6(2), 6(4)- and 6(1), 6(2), 6(6)-substituted isomers were indistinguishable by this method, these isomers were distinguished clearly by digestion of branched oligosaccharides produced from each isomer by the aforesaid method, with B. stearothermophilus neopullulanase or with glucoamylase. The resulting hydrolysates were analyzed by HPLC on an amino derivatized column and by fast-atom bombardment spectrometry (FABMS). The chromatographic behavior and spectral data (13C NMR and FABMS) of five positional isomers of trimaltosyl-beta CD are described.

Comparative study on inclusion complexation of maltosyl-beta-cyclodextrin, heptakis(2,6-di-O-methyl)-beta-cyclodextrin and beta-cyclodextrin with fucosterol in aqueous and solid state

The complexation of fucosterol with three kinds of beta-cyclodextrin (beta-CyD) was investigated in aqueous solution and in the solid state. The solubility of fucosterol increased significantly on its complexation with maltosyl-beta-CyD and heptakis(2,6-di-O-methyl)-beta-CyD (DM-beta-CyD), while no appreciable increase was observed when complexed with beta-CyD. The stability constant of complexation with beta-CyD estimated from solubility determinations was greater for a 1:2 complex than for a 1:1 complex. On the other hand, 1:1 complexation of fucosterol with maltosyl-beta-CyD or DM-beta-CyD was greater than 1:2 complexation. The solid complexes were obtained in molar ratios of 1:2 and 1:3 for beta-CyD and maltosyl-beta-CyD complexes, respectively. The inclusion behaviour of fucosterol with maltosyl-beta-CyD was compared with beta-CyD in the solid state using DSC, powder X-ray diffractometry and CP/MAS 13C NMR. Maltosyl-beta-CyD showed different inclusion behaviour compared with beta-CyD, and produced an amorphous structure of fucosterol on complex formation. The dissolution rate of fucosterol-maltosyl-beta-CyD complex was significantly faster than other complexes due to its high aqueous solubility and amorphous structure.

Protection of erythrocytes against hemolytic agents by cyclodextrin polysulfate

Cyclodextrins generally exhibit hemolytic activity, some at concentrations as low as 1-10 mg/mL or lower. However, we found previously that a highly polysulfated cyclodextrin has no demonstrable hemolytic activity (Macarak et al., Biochem Pharmacol 42: 1502-1503, 1991). In the present study, we determined that, in fact, cyclodextrin polysulfate (CDS) actively protected erythrocytes against hemolysis induced by a wide spectrum of hemolytically active substances, ranging from pharmaceuticals, such as chlorpromazine, to solid suspensions of siliceous particles. The protective action was also effective against the hemolytic action of non-sulfated cyclodextrins. The similar kinetic responses of the erythrocytes to CDS protection against such chemically and structurally diverse hemolytic agents suggest a common mechanism involving the cell. Addition of the sulfated cyclodextrins to other cyclodextrin compounds used to solubilize poorly soluble pharmaceutical agents can extend the allowable maximum dosage without deleterious hemolytic action.

Preparation of di-O-triphenylmethyl-(trityl-) cyclomaltohexaoses and -cyclomaltoheptaoses and characterization of three positional isomers of each by the "hex-5-enose degradation"

Regioisomeric 6(1),6n-di-O-trityl-cyclomaltohexaoses (cG6s) or -cyclomaltoheptaoses (cG7s) were prepared by the reaction of cyclomaltohexaose (1, cG6) or cylomaltoheptaose (5, cG7) with chlorotriphenyl-methane in pyridine and isolation by h.p.l.c. The regiochemical determination of each three ditrityl-substituted derivatives has been accomplished by the "hex-5-enose degradation", followed by measurement of their f.a.b.-mass spectra.

Effect of a novel soft steroid on the wound healing of rabbit cornea

The effect of a 'soft' anti-inflammatory corticosteroid on the corneal wound healing was investigated in rabbits. Albino rabbits were treated with soft steroid and dexamethasone after linear perforating corneal incision. Soft drug design is aimed to control and direct the drug activity and in vivo metabolism to nontoxic moieties. These drugs are rapidly deactivated after they reach the general circulation. While having good local activity, they thus possess high therapeutic indexes without systemic side effects. The wound healing process was evaluated qualitatively by histology. Photomicrographs are presented to show that the soft steroid is as or more effective than dexamethasone in minimizing scarring in addition to its advantageous metabolic properties. This soft steroid may be an efficient anti-inflammatory and anti-allergic agent in topical application without the majority of unwanted activities of traditional drugs by deliberately simplifying their disposition.

O-carboxymethyl-O-ethylcyclomaltoheptaose as a delayed-release-type drug carrier: improvement of the oral bioavailability of diltiazem in the dog

The utility of O-carboxymethyl-O-ethylcyclomaltoheptose (carboxymethyl-ethyl-beta-cyclodextrin, CME-beta CD) as a delayed-release-type drug carrier was investigated in vitro and in vivo, using diltiazem hydrochloride as a model drug. The aqueous solubility of CME-beta CD showed a marked dependency on pH, because of the ionization of the carboxyl group (pKa 3.75). The formation of an inclusion complex between diltiazem and CME-beta CD in aqueous solution and in the solid state was assessed by a solubility method and by X-ray diffractometry, respectively. The rate of release of the drug from the compressed tablet containing the complex was significantly retarded in solutions at low pH and increased with increase in pH, and this was reflected in the blood levels in the dog after the oral administration. The results suggested that the use of CME-beta CD could improve the oral bioavailability of diltiazem and release the drug preferentially in the intestinal fluid but only slightly in the gastric fluid.