Solubilization of 2-Acetoxy-Benzencarboxylic Acid Using Beta Cyclodextrins

2-acetoxy-benzencarboxylic acid is one of the most famous salicylate drugs today, a pharmaceutically active compound known as aspirin. It is poorly soluble in water which results in decreased bioavailability of the drug in the organism. The increase in water solubility of insoluble or poorly soluble drugs is therefore of great importance, which is the aim of this study. Inclusion of the drug in the molecule with a higher water solubility significantly increases its solubility and biological availability. Natural and hydrophilic derivatives of natural cyclodextrins are in the spotlight for their role as solubilizing excipients. Studies indicate that the use of β-cyclodextrin inclusion complexes with acetylsalicylic acid formed, increases the solubility of the drug in water. Many advantages of drug-complexation with cyclodextrins have been reported in scientific literature which includes increased solubility, enhanced bioavailability, improved stability, masking of bad test or odour, reduced side effect. Orally administered aspirin requires high and frequent dosing because it undergoes extensive pre systematic metabolism. Also chronic oral aspirin use is associated with serious gastrointestinal side-effects. Complexation with CD alleviates the side effects to some extent. The bioavailability and solubility of aspirin has to be increased to overcome the side-effects of aspirin related to stomach and gastro intestinal tract. The phase solubility study was performed according to the method of Higuchi and Connors by adding the 2-acetoxi-benzencarboxylic acid in excess to different concentrations of different beta cyclodextrins solutions. Phase solubility study records shown that the stability constant and complex stoichiometry of 2-acetoxi-benzencarboxylic acid-CD complexes gives linearly improve with the concentration of CD. Complexes were analyzed by UV-VIS spectroscopy and were characterized by infrared spectroscopy.

Effects of β-cyclodextrins on the enzymatical hydrolysis of chiral dichlorprop methyl ester

The effect of β-cyclodextrins(β-CDs) on the enzymatical hydrolysis of chiral dichlorprop methyl ester (DCPPM) was studied. Four kinds of β-cyclodextrins(β-cyclodextrin, Partly methylated-CD(PM-β-CD), hydroxypropyl-cyclodextrin(HP-β-CD) and carboxymethyl-cyclodextrin(CM-β-CD)) were used. Compared with 100% DCPPM in the absence of β-cyclodextrins, the activity of lipase decreased with the increase of β-cyclodextrin and PM-β-cyclodextrin. However, CM-β-cyclodextrin stimulated the lipase activity. The inhibition effect of β-cyclodextrin and PM-β-cyclodextrin on the hydrolysis of DCPPM is affected by many factors other than degree of the methylation blocking the active site of lipase. UV-Vis and Fourier transform infrared(FTIR) spectroscopy studies of the complexation of aqueous DCPPM with β-CDs provide fresh insight into the molecular structure of the complex and explain the effects of β-CDs on enzymatical hydrolysis of chiral DCPPM. Data showed that inclusion complexes had formed by complexation of the CM-β-CD with DCPPM and the solubility of DCPPM was increased in water, which leaded to the increased lipase activity.

Inclusion complexes between sildenafil citrate and cyclodextrins enhance drug solubility

Sildenafil citrate is a potent and selective phosphodiesterase-5inhibitor. It is effectively used in the treatment of erectile dysfunction and pulmonary arterial hypertension. The drug is rapidly absorbed and pharmacologically acts within30 min to 1 h after oral administration. However, it has a relatively low absolute bioavailability of 41%because its limited solubility in water is the major problem (1)To improve the oral bioavailability of poorly water-soluble drugs.

Effect of antioxidant activity of caffeic acid with cyclodextrins using ground mixture method

In the current study, we prepared a ground mixture(GM) of caffeic acid(CA) with α-cyclodextrin(αCD) and with β-cyclodextrin(βCD), and then comparatively assessed the physicochemical properties and antioxidant capacities of these GMs. Phase solubility diagrams indicated that both CA/αCD and CA/βCD formed a complex at a molar ratio of 1/1. In addition, stability constants suggested that CA was more stable inside the cavity of αCD than inside the cavity of βCD. Results of powder X-ray diffraction(PXRD) indicated that the characteristic diffraction peaks of CA and CD disappeared and a halo pattern was produced by the GMs of CA/αCD and CA/βCD(molar ratios = 1/1). Dissolution testing revealed that both GMs had a higher rate of dissolution than CA alone did. Based on the1 H-1 H NOESY NMR spectra for the GM of CA/αCD, the vinylene group of the CA molecule appeared to be included from the wider to the narrower rim of the αCD ring. Based on spectra for the GM of CA/βCD, the aromatic ring of the CA molecule appeared to be included from the wider to the narrower rim of the βCD ring. This suggests that the structures of the CA inclusion complexes differed between those involving αCD rings and those involving βCD rings. Results of a DPPH radical-scavenging activity test indicated that the GM of CA/αCD had a higher antioxidant capacity than that of the GM of CA/βCD. The differences in the antioxidant capacities of the GMs of CA/αCD and CA/βCD are presumably due to differences in stability constants and structures of the inclusion complexes.

Synthesis of Methylated β-Cyclodextrins Derived Optically Active Poly(N-diphenylmethyl maleimide)

The methylated β-cyclodextrins derived optically active polymers are firs synthesized through asymmetric polymerization of N-diphenylmethyl maleimide with lithium salt of heptakis(2,6-O-dimethyl) β-cyclodextrin (DM-β-CD) as an initiator. The resulting polymers show negative specific rotation which is opposite in sign to that of DM-β-CD. The asymmetric induction is further confirmed by circular dichroism. The structure is characterized by IR and NMR spectroscopies

N-ALKYLPHENOTHIAZINE RADICAL CATIONS GENERATED IN THE CAVITY OF β-CYCLODEXTRINS IN A(?)UEOUS SOLUTION

Phenothiazine and i^+s derivatives were oxidized by l_2 and 2,2,6,6-tetrametbyl-4- acetyloxypiperidine oxoammonium hexachloroantimonate to the corresponding radical cations in the cavity of β-cyclodextrins in aqueous solution.The mechanism of electron transfer between substrates and oxidants is discussed in terms of association of β-CDs.

Feasibility study of cyclodextrins as active pharmaceutical ingredients for the treatment of GM1-gangliosidosis

GM1-gangliosidosis is a rare lysosomal storage disorder characterized clinically by a wide range of variable neurovisceral,ophthalmological and dysmorphic features. Without enough functionalβ-galactosidase, GM1-gangliosides cannot be degraded in lysosomes, and accumulate to toxic levels in many tissues and organs, particularly in the brain. In spite of several approaches for the treatment of GM1-gangliosidosis.

Gold Nanoparticles Incorporated with Cyclodextrins and Its Applications

Cyclodextrins are naturally oligosaccharides which had cyclic glucopyranoside units even if six units to form α-cyclodextrin (α-CD), seven units β-cyclodextrin (β-CD) or eight units γ-cyclodextrin (γ-CD) and some other derivatives. It has a truncated cone shape with a hydrophobic cavity and a hydrophilic from the external surface of cyclodextrins. Gold nanoparticles incorporated with cyclodextrins enhanced optical and electrical properties of the resulting conjugates, due to the gold nanoparticles’ unique physical and chemical properties because of their surface plasmon resonance. Here is a review of gold nanoparticles/cyclodextrin’s different applications including sensing, antimicrobial effect, and their variable medical/pharmaceutical applications. Generally, gold nanoparticles and cyclodextrin conjugates showed developed and pronounced advantages due to their biocompatibility and enhanced physical and electric properties.

The Effect of Cyclodextrins in Polymer Particles Synthesis

The free radical polymerization of styrene in water in the presence of β-cyclodextrin (β-CD) is described. It is found that β-CD could greatly accelerate the polymerization, enhance the final conversion of monomer. The particle-size distribution of the final polymer is also improved than that without β-CD in the system.

Synthesis of Amino Acid Derived β-Cyclodextrins Used in Chiral Separation by Capillary Electrophoresis

Six new kinds of amino acid derived β-cyclodextrins were synthesized to improve their water solubility and chiral separation properties. They are heptakis{2,6-di-O-[3-L-(1-isopropyl carboxyl methyl amino)-2-(hydroxy) propyl]}-β-cyclodextrin (i.e. L-Val-β-CD), heptakis{2,6-di-O-[3-L-(1-benzyl carboxyl methyl amino)-2-hydroxy propyl]}-β-cyclodextrin (i.e. L-Phe-β-CD), heptakis{2,6-di-O-[3-(D, L-1-benzyl carboxyl methyl amino)-2-hydroxy propyl]}-β-cyclodextrin (i.e. D,L-Phe-β-CD), heptakis{2,6-di-O-[3-(L-1-hydroxymethyl carboxyl methyl amino)-2-hydroxy propyl]}-β-cyclodextrin (i.e. L-Ser-β-CD), heptakis{2,6-di-O-[3-(L-1-carboxylmethyl carboxyl methyl amino)- 2-hydroxy propyl]}-β-cyclodextrin (i.e. L-Asp-β-CD), heptakis{2,6-di-O-[3-(L-2-carboxyl tetramethylene amino)-2-hydroxy propyl]}-β-cyclodextrin (i.e. L-Pro-β-CD). Their chemical structures were certified using FTIR and ()~1H NMR. Except for L-Phe-β-CD and D,L-Phe-β-CD, that are in soluble in water, the other amino acid derived β-CDs all have good water solubility. D,L-tyrosine and promethazine were baselinely separated by L-Val-β-CD in capillary electrophoresis.

Effects of cyclodextrins on hydrolysis of malathion

Cyclodextrins （CDs）, with hydrophobic interior cavity and hydrophilic external surface, are capable of accelerating or inhibiting chemical degradation of organophosphorus pesticides through forming inclusion complexes between CDs and pesticides. This work evaluated the effects of CDs on hydrolysis of malathion in an attempt to assess their potential application in environmental approach. β-CD and its two derivatives, randomly methylated β-CD （RAMEB） and hydroxypropyl β-CD （HP-β-CD）, were tested. It was found that RAMEB could inhibit the hydrolysis of malathion, and this was the function of pH and temperature, the inhibitory effects increase with increasing concentration of RAMEB and elevating temperature between 15 and 35℃. On the other hand, β-CD and HP-β-CD have little or no stabilizing effects on malathion at all pH and temperature studied, except that the large concentration of β-CD and HP- β-CD can mildly reduce hydrolysis of malathion. Both 2 mol/L and 5 mol/L urea increase the inhibitory effects of RAMEB on hydrolysis of malathion at 25℃, oH 9.0.

Gas Chromatographic Enantiomer Separation of Cyclopropane Derivatives on Three 2, 6-Di-O-allyl-3-O-acylated-β- cyclodextrins Chiral Stationary Phases

Eight pairs of enantiomers of cyclopropane derivatives were resolved on capillary gas chromatographic columns using three new 2, 6-di-O-allyl-3-O-acylated-β-cyclodextrins as chiral stationary phases. It was found that the three β-CDs can separate some of the racemic cyclopropane derivatives well.

The protective effect of cyclodextrin on the color quality and stability of Cabernet Sauvignon red wine

The impact of cyclodextrins(CDs)on wine quality and stability remains largely unknown.This study systematically assessed the protective effect of the post-fermentation addition of CDs on color stability of red wine from the viewpoints of color characteristics,copigmentation and phenolic profiles.The grey relational analysis(GRA)and principal component analysis(PCA)methods were employed to dissect the key effective determinants related to color quality.The addition of CDs induced a significant hyperchromic effect of 8.19-25.40%,a significant bathochromic effect and an enhancement of the color intensity.Furthermore,the evolution of anthocyanin forms and the content of monomeric anthocyanins revealed that β-CD is a superior favorable cofactor during wine aging,but for long-term aging,2-HP-β-CD and 2-HP-γ-CD are more beneficial in promoting the formation of polymerized anthocyanins and color stability.This work provides an important reference for the use of CDs to enhance the color quality and stability of red wines.

Simultaneous elution of polycyclic aromatic hydrocarbons and heavy metals from contaminated soil by two amino acids derived from β-cyclodextrins

Two highly water-soluble amino acids, which derived from β-CDs, i.e., glutamic acid-β-cyclodextrin （GluCD） and ethylene-diamine- β-cyclodextrin （EDCD）, were synthesized and were examined for their effect on solubilization of anthracene （ANT）, complexation of cadmium （Cd^2＋）, and elution removal of ANT and Cd^2＋ in soil. The results showed that GluCD and EDCD were powerful complexant for ANT and Cd^2＋. In the presence of 10 g/L GIuCD and EDCD, the solubilization of ANT increased by 47.04 and 23.85 times compared to the control, respectively. GluCD resulted in approximately 90% complexation of Cd^2＋ while 70% complexation was observed for EDCD. Simultaneously, GluCD and EDCD could greatly enhance the elution removal of ANT and Cd^2＋ from soil. GluCD resulted in the highest elution efficiency of ANT and Cd^2＋. With the addition of 10 g/L GluCD, 53.5% of ANT and 85.6% of Cd^2＋ were eluted, respectively. The ANT had a negligible effect on the Cd^2＋ removal due to different complexing sites of ANT and Cd^2＋, while Cd^2＋ enhanced the ANT removal under the addition of GluCD because Cd^2＋ neutralized the -COOH group of GIuCD. Adversely, the removal of ANT was decreased with Cd^2＋ under the addition of EDCD, this was due to the fact that Cd^2＋ enhanced the polarity of EDCD molecule and inhibited the complexation between ANT and EDCD. The study suggested that GluCD could be preferred and be successfully applied to remediation of heavy metals or organic compounds in contaminated soil.

Molecular recognition studies on supramolecular systems (XXIV)——Conformations and complexation abilities of chemically modified cyclodextrins in aqueous solution

Circular dichroism spectral and fluorescence decay methods have been employed to determine the conformations of mono[6-(p-tolylseleno)-6-deoxy]-p-CD(1), mono(6-anilino-6-deoxy) β -CD (2) and mono[6-(L-tryptophan)-6-deoxy]-β-CD (3) in phosphate buffer solution (pH 7.2, 0.1 mol dm-3) at 298.15 K. The results indicate that compounds 2 and 3 formed self-inclusion complexes in aqueous buffer solution, while the substituent of compound 1 was not included into cyclodextrin cavity at all. Furthermore, the complex stability constant (logKs) and Gibbs free energy change (-ΔG° ) of these three cylcodextrin derivatives with several cycloalkanols have been determined by circular dichroism spectral titration in phosphate buffer solution at 298.15 K. It is found that the location of the substituent affects the stability of host-guest complex in aqueous solution.

Predicting complexation performance between cyclodextrins and guest molecules by integrated machine learning and molecular modeling techniques

Most pharmaceutical formulation developments are complex and ideal formulations are generally obtained after extensive experimentation.Machine learning is increasingly advancing many aspects in modern society and has achieved significant success in multiple subjects.Current research demonstrated that machine learning can be adopted to build up high-accurate predictive models in drugs/cyclodextrins(CDs)systems.Molecular descriptors of compounds and experimental conditions were employed as inputs,while complexation free energy as outputs.Results showed that the light gradient boosting machine provided significantly improved predictive performance over random forest and deep learning.The mean absolute error was 1.38 kJ/mol and squared correlation coefficient was0.86.The evaluation of relative importance of molecular descriptors further demonstrated the key factors affecting molecular interactions in drugs/CD systems.In the specific ketoprofen-CD systems,machine learning model showed better predictive performance than molecular modeling calculation,while molecular simulation could provide structural,dynamic and energetic information.The integration of machine learning and molecular simulation could produce synergistic effect for interpreting and predicting pharmaceutical formulations.In conclusion,the developed predictive models were able to quickly and accurately predict the solubilizing capacity of CD systems.Current research has taken an important step toward the application of machine learning in pharmaceutical formulation design.

Molecular recognition and biological application of modified β-cyclodextrins

The molecular recognition based on cyclodextrins(CDs) has become a focus of interest in modern supramolecular chemistry.CDs are known to encapsulate various ions and organic/inorganic molecules in their hydrophobic cavities and form stable inclusion complexes through cooperative noncovalent interactions. During the past few decades, a large variety of modified CDs have been elaborately designed and synthesized, which significantly promotes our molecular-level understanding of the structure–function relationship in many supramolecular systems. Through the accurate analysis on the molecular binding behaviors, one can create a library of CD-based nanoassemblies with controlled physicochemical properties. In this review, we will focus on the stability constant-directed molecular recognition and the biological activities of β-CDs toward some representative bioactive substrates, including metal ions, steroids, porphyrins, amino acids and oligopeptides, as well as drug molecules, with the final goal of promoting their practical applications in the biomedical field.

Self-assembly behavior of phenyl modified β-cyclodextrins

The self-assembly behavior of mono(6-phenolic-6-deoxy)-β-cyclodextrin (1) both in solu- tion and the solid state is comparatively studied by X-ray crystallography and 1H NMR spectroscopy. The results obtained show that the phenolic groups in the crystal 1 can successively penetrate into the adjacent β-cyclodextrin cavities from the secondary side to form head-to-tail linear polymeric su- pramolecule with a 2-fold screw axis. The self-assembly behavior also can be determined in D2O so- lution, giving a self-association constant of 240 mol?1?L. Using the present and previous structures reported for the relevant β-cyclodextrin derivatives, i.e., mono(6-anilino-6-deoxy)-β-cyclodextrin (2), mono(6-phenylselenyl-6-deoxy)-β-cyclodextrin (3), and mono(6-phenylthio-6-deoxy)-β-cyclodextrin (4), we further reveal the factors governing the formations of supramolecular assemblies.

Formation of nanotubes and secondary assemblies of cyclodextrins induced by BBOT

The study of cyclodextrin nanotubes is a significant topic among the self-assembly behaviors of cyclodextrins.We report herein the interaction of 2,5-bis(5'-tert-butyl-2-benzoxazoyl)thiophene(BBOT) with α-,β-,γ-cyclodextrins(CDs).It has been discovered that the reaction patterns of BBOT with CDs are remarkably different.α-CD forms a simple inclusion complex with BBOT in a stoichiometry of 1:2(guest:host).β-CD forms a 1:1 inclusion complex with BBOT at its low concentration.At higher concentration of BBOT,the nanotube and secondary assembly of β-CD are formed.As for γ-CD,the nanotube and secondary assembly are formed within the whole concentration range of BBOT studied.The structure of γ-CD nanotubes is different from that of β-CD nanotubes to a certain extent.

UV-induced self-assembly of the inclusion complexes formed between a long-chain photochromic spiropyran and cyclodextrins

Photochromic spiropyran with a long chain alkyl substitute can form axial complexes with α-, β-, and γ-cyclodextrin, respectively. The complexes show normal photochromism. The novel property of the colored forms of the inclusion complexes is that they can assemble into dimers at relatively low concentration or J-aggregates at relatively high concentration. For α-, β-, and γ-cyclodextrin, λmax of the J-aggregates appear at 700 650, and 630 nm, respectively. The sizes of the cavities of cyclodextrins have very little effect on the spectra and decoloration kinetics of the dimers, but have great effects on the spectra of the J-aggregates. Unlike the charge transfer complex of Krongauz, the decoloration process of the dimers or J-aggregates cannot be described by an exponential or a two-exponential kinetics, but obey half-order kinetics very well. Another result that can be deduced from the kinetic analysis is that unlike the dimers formed in apolar solvents or in polymers, which consist of a