In vivo activity of sertaconazole in experimental candidiasis in the mouse

The antifungal activity of sertaconazole (SZ), 1-(2-[(7-chlorobenzo[b]thien-3-yl)methoxyl]- 2-(2,4-dichlorophenyl)ethyl)-1H-imidazole, has been assessed in vivo in comparison with miconazole (MZ) in a murine vaginal candidiasis model. Mice (eight per group) were maintained in oestrus by subcutaneous injection of oestradiol benzoate (25 mg/kg) 5 days before and 2 days after inoculation intravaginally with 5 x 10(4) blastospores of C. albicans (strain No. 17) in 0.05 ml. Animals were treated with 0.03 ml of the appropriate 2% cream formulation 1 h after infection (single dose regimen) or on days 3, 4 and 5 post-infection (three-dose regimen). The efficacy was measured in each test group by Sabouraud agar plate count of vaginal specimens and expressed as % reduction in the number of yeast cells with regard to the control group (infected and untreated). The two treatments indicated a significant reduction (according to the non-parametric method of Mann-Whitney) (p greater than 0.05) for both SZ (97.9% and 93.6%) and MZ (77.5% and 76.9%) groups. When the values from SZ and MZ were compared, SZ proved more active than MZ in the single dose regimen.     

Modeling the effect of selected cyclodextrins on nifedipine solubility

Nifedipine is a dihydropyridine calcium channel antagonist effective in the clinical management of cardiovascular disease. Due to nifedipine's poor water solubility and erratic bioavailability, complexation with selected cyclodextrins was studied in order to overcome these limitations. The aim was to develop a quantitative structure property relationship (QSPR) to identify cyclodextrin molecular properties important in complex formation and provide a predictive tool which would be valuable during preformulation studies. The QSPR developed indicates that the major driving forces for nifedipine complexation, in addition to cyclodextrin concentration, are hydrophobicity and Van der Waals interactions (3D solubility parameters, hydrophilic surface area and differential connectivity index).     

Comparative studies of the enhancing effects of cyclodextrins on the solubility and oral bioavailability of tacrolimus in rats

The enhancing effects of cyclodextrins (CyDs) on the solubility, the dissolution rate, and the bioavailability of tacrolimus after oral administration to rats were examined and compared with those after administration of a PROGRAF capsule containing the solid dispersion formulation of tacrolimus. Here we used natural CyDs and the hydrophilic beta-CyD derivatives; that is, randomly methylated-beta-cyclodextrin (RM-beta-CyD), heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DM-beta-CyD), 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD), and sulfobutyl ether beta-cyclodextrins (SBE-beta-CyDs). Of the natural CyDs, the solubility of tacrolimus increased in the addition of beta-CyD, indicating that the cavity of beta-CyD comfortably fits the drug. Of the beta-CyD derivatives, DM-beta-CyD had the greatest solubilizing activity and gave the A(p) type phase solubility curve as defined by Higuchi and Connors, suggesting the formation of higher-order complexes. The result of van't Hoff plot suggests that the enthalpy is dominant for the complexation of tacrolimus with DM-beta-CyD. The dissolution rate of tacrolimus was markedly augmented by the complexation with DM-beta-CyD, reflecting its solubilizing activity. An in vivo study revealed that DM-beta-CyD increased the bioavailability of tacrolimus with low variability in the absorption after oral administration of the tacrolimus suspension to rats. The present results suggest that DM-beta-CyD is particularly useful in designing oral preparations of tacrolimus with an enhanced bioavailability and a reduced variability in absorption.     

Effect of cyclodextrins on the solubility and stability of candesartan cilexetil in solution and solid state

Guest-host interactions of candesartan cilexetil (CAND) with cyclodextrins (CyDs) have been investigated using phase solubility diagrams (PSD), X-ray powder diffractometry (XRPD), differential scanning calorimetry (DSC) and molecular mechanical modelling (MM). Estimates of the complex formation constant (K(11)) show that the tendency of CAND (pK(a)=6.0) to complex with CyDs follows the order: β-CyD>HP-β-CyD>γ-CyD>α-CyD. Complex formation of CAND with β-CyD (ΔG°=-31.5 kJ/mol) is largely driven by enthalpy change (ΔH°=-32.8 kJ/mol) and slightly retarded by entropy change (ΔS°=-4.6J/mol K). The HPLC results indicate that complex prepared by freeze drying method is chemically not stable due to the formation of amorphous CAND. Also it may suggest formulating CAND with β-CyD by kneading (dispersion) or co-evaporation (real inclusion complex) methods into capsule rather than compressed in tablets, where the compression enhances the instability of CAND. DSC thermograms for CAND/β-CyD complexes proved the formation of inclusion complexes with new solid phase. MM studies indicate the partial penetration of CAND into the β-CyD cavity.     

Effect of cyclodextrins on the solubility and stability of a novel soft corticosteroid, loteprednol etabonate

To increase the aqueous solubility and stability of the soft corticosteroid loteprednol etabonate (LE), drug complexation using various cyclodextrins (CDs), such as gamma-cyclodextrin (gamma-CD), 2-hydroxypropyl-beta-cyclodextrin (HPBCD), maltosyl-beta-cyclodextrin (MBCD), mixture of glucosyl/maltosyl-alpha-, beta-, and gamma-cyclodextrin (GMCD), and heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DMCD), were attempted. The solubilizing and stabilizing effects of CD by itself or combined with various co-solvents were also investigated. Micronized (5 micron) LE was mixed in various aqueous CD or CD with cosolvent solutions. After equilibration and filtration at 23 degrees C, the solubility of LE was determined by HPLC. Subsequently, the stability of LE in the solutions was also determined by following the LE concentration change in the solution for an appropriate period. CD complexation significantly increased the aqueous solubility and stability of LE. The increase in solubility displayed a concentration dependency on CDs (0-50%). Among the five CDs used, DMCD showed the highest effects on the solubility (4.2-18.3 mg/ml in 10-50% DMCD) and stability (t90 > 4 years at 4 degrees C, when LE 0.5 mg/ml was dissolved in 10% DMCD solution) of LE. By adding co-solvents, such as glycerol, propylene glycol (PG), polyvinyl alcohol (PVA), and polyvinylpyrrolidone (PVP-10), the solubility of LE in DMCD solutions was further increased. Degradation of LE to the corresponding metabolites, delta 1-cortienic acid etabonate (AE) and delta 1-cortienic acid (A), in aqueous CD solutions appeared to be a predicted, two-step kinetics. Differential Scanning Calorimetry (DSC) was used to assist explaining the solubilizing and stabilizing activity differences between CDs. LE/CD mixture or lyophilized LE/CD complex was scanned at a rate of 20 degrees C/min. The exothermic peak found in the DSC diagram with LE/DMCD sample, but not with LE/HPBCD samples, suggests a stronger complex formed between LE and DMCD, resulting in higher solubility and stability of LE in DMCD than in HPBCD.     

HPLC and solubility study of the interaction between pindolol and cyclodextrins

The complexation with beta-cyclodextrin (beta-CD) has been investigated using reversed-phase liquid chromatography. The compounds tested have been pindolol and, for comparison purposes, indole and 4-methoxyindole. The retention behaviour has been analysed on a Kromasil 100 C18 column and the mobile phase used was methanol-pH 6 phosphate buffer (15/85v/v) in which beta-CD was incorporated as a mobile phase additive. The decrease in the retention times with increasing concentrations of beta-CD enables the determination of the apparent stability constants of the complexes. In addition, the low solubility of pindolol, a weak base, in pH 12 aqueous solution has been improved by complexation with different cyclodextrins. The solubility enhancements with 1.4 x 10(-2) M beta-, hydroxypropyl-beta, and gamma-CD have been 1.9, 1.8 and 1.4-fold, respectively, with 2.4 x 10(-2) M methyl-beta-CD it was 2.8-fold whilst no effect was observed with alpha-CD. The stability constants of the complexes at pH 12 have been determined from the solubility isotherms.     

Derivatives of phenoxyacetamide and antimycotic activity

Novel N-(3-methyl-4-R-isoxazol-5-yl)-2-R1-4-R2-phenoxyacetamides and N-(3-methyl-4-R-isoxazol-5-yl)-2-(2-R1-4-R2-phenoxyacetamido) benzamides were prepared and tested against Candida albicans and Cryptococcus neoformans. The results of the antimicrobial assay showed that the presence of two amidic groups usually enhances antimycotic activity.     

Studies on the antimycotic activity of 5-fluoroorotic acid

The antimycotic effect of 5-fluoroorotic acid (FOA) was studied in experimental and clinical conditions. The experiments in vitro were performed on 21 strains of fungi isolated mainly from clinical material. The effect of FOA was compared with those of the structurally related drug 5-fluorocytosine. The clinical study was performed on 40 patients aged 18 to 75 years with mycological diseases. FOA in different dosage forms was applied topically 2 to 3 times daily for 30 days. Microscopic and cultured mycological studies were performed before and after treatment. The results showed that FOA possesses a well-expressed anticandidal effect close to that of 5-fluorocytosine, as well as moderate antidermatophytal effects. Clinical studies of 1% FOA cream showed good therapeutic effects similar to that of Ung. Whitfield, but 55% of the patients developed relapse of the lesions after discontinuation of the treatment. Higher concentrations of FOA included in milk suspension and powder induced severe side effects of local irritability.     

Complexation of phenytoin with some hydrophilic cyclodextrins: effect on aqueous solubility, dissolution rate, and anticonvulsant activity in mice.

The main objective of this study was to evaluate the influence of hydroxypropylated beta- and gamma-cyclodextrins and Me-beta-cyclodextrin (HP-beta-CD, HP-gamma-CD, and Me-beta-CD, respectively) on the dissolution rate and bioavailability of the antiepileptic agent, phenytoin (DPH). The corresponding solid complexes were prepared by a freeze-drying method and characterized by infrared spectroscopy, X-ray powder diffraction, and differential scanning calorimetry studies. Evidence of inclusion complex formation in the case of HP-beta-CD was obtained by (1)H- and (13)C-nuclear magnetic resonance spectroscopy. Drug solubility and dissolution rate in 0.05 M potassium phosphate buffer (pH 6) were notably improved by employing the beta-CDs. Thus a 45% w/v HP-beta-CD or Me-beta-CD solution gave rise to an increase of dissolved drug of 420- and 578-fold, respectively. The Q(10) (i.e. percentage of dissolved DPH at 10 min) was 5.2% for the pure drug and 93, 98, and 96% for DPH/HP-beta-CD, DPH/HP-gamma-CD, and DPH/Me-beta-CD complexes, respectively. Moreover, it was found that in the maximal electroshock seizure test in mice the DPH/Me-beta-CD complex exhibited anticonvulsant activity similar to DPH sodium salt (NaDPH).     

Investigation of solubility properties of nifluminic acid containing cyclodextrins and polyvidone

One of the most important task of the pharmaceutical technology is to reach a possible high gastrointestinal absorbtion of the active ingredient. Therefore, it is necessary to have a good solubility in the gastric/intestinal medium. In this way the applied drug quantity and unwanted side effects can be reduced with solubility increasing. The water-insoluble drug's solubility and bioavailability can be increased by the alteration of their physicochemical properties. Nifluminic acid is a frequently used anti-inflammatory drug with low aqueous solubility. Inclusion complexation with cyclodextrins is an efficacious method to improve the solubility, stability and bioavailability. Ternary systems were prepared and investigated to use nifluminic acid, hydoxypropyl-beta-cyclodextrin and polyvidone. The aims of the study were to investigate the solubility rate, the in vitro diffusion ability, to determine the n-octanol/water partition coefficient, and to study the thermoanalitycal properties of products. The results suggested that complexation with cyclodextrin and the use of polyvidone is better method than to prepare binary systems. Inclusion complexation was presumed in the event of the ternary composition to improve the bioavailability of nifluminic acid.     

Inclusion of acitretin into cyclodextrins: phase solubility, photostability, and physicochemical characterization

Acitretin, a retinoid for the treatment of severe psoriasis, exhibits extremely low aqueous solubility and high photosensitivity. This study investigated the effects of the complexation of acitretin with the respective hydroxypropyl-beta-cyclodextrin (HPBCD) and randomly substituted methyl-beta-cyclodextrin (RMBCD) on the aqueous solubility and photostability of the drug. Phase-Solubility studies indicated that the solubility of acitretin was dramatically improved by formation of complexes and further increased by pH adjustment. Stability constants were much higher for acitretin complexed with RMBCD than with HPBCD. Both cyclodextrins acted to decrease degradation of acitretin in solution. The physicochemical properties of solid inclusion complexes were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffractometry. Molecular modeling with MMFF94s force field (SYBYL V6.6) was utilized to predict the preferred orientation of acitretin in the cyclodextrin cavity and the main structural features responsible for the enhancement of its solubility and photostability.     

Synthesis and antimycotic activity of some benzyloxyimino compounds

Some benzyloxyimio compounds, related to oxiconazole and having a 1H-indole or 1H-benzimidazole moiety, have been synthesized and tested in vitro for their antimycotic activity against Candida tropicalis and C. albicans. The most active was showed to be 0-(2,4-dichlorobenzyl)-1-benzyl-5-nitro-1H-benzimidazole-2-carboxaldehyd e oxime (MIC: 25 micrograms/ml against both microorganisms). A structural feature important for the biological activity of the series appears to be presence of a benzimidazole nucleus substituted by an electron withdrawing group.     

Influence of modified cyclodextrins on solubility and percutaneous absorption of celecoxib through human skin

We evaluated the ability of two modified cyclodextrins, hydroxypropyl-beta-cyclodextrin (HP-beta-Cyd) and 2,6-di-O-methyl-beta-cyclodextrin (DM-beta-Cyd), to influence the percutaneous absorption through isolated human stratum corneum and epidermis (SCE) of celecoxib (CCB). Previous studies demonstrated that DM-beta-Cyd includes the drug, producing a significant increase of water solubility (0.5 mg/ml at 25 degrees C) and dissolution rate of CCB. In this work chemical-physical characterization studies were performed to evaluate the ability of HP-beta-Cyd to include CCB. We showed that only an external interaction could exist between CCB and HP-beta-Cyd that positively influences the water solubility of the drug (0.12 mg/ml at 25 degrees C for CCB-HP-beta-CyD system and 4.12 x 10(-3) mg/ml at 25 degrees C for free CCB). In vitro percutaneous experiments were performed using samples in solution and in suspension containing different Cyd concentrations. Both HP-beta-Cyd and DM-beta-Cyd enhanced drug flux through SCE by means of an increase of dissolution rate of the drug as well as a direct action on the stratum corneum (SC). Histological analysis of treated SCE showed a protective effect of the two Cyds towards an invasive action shown by CCB on SC.     

Experimental and mesoscale computational dynamics studies of the relationship between solubility and release of quercetin from PEG solid dispersions

The flavonol quercetin is potentially clinically relevant for its antimicrobial, beneficial cardiovascular effects, cancer treatment amongst others. However, its successful therapeutic application is severely curtailed by its poor water solubility and poor absorption following oral administration. In this study, solid dispersions of quercetin in poly(ethylene glycol) (PEG) at various compositions demonstrated an increase in the solubility, however with time, dissolution profiles show a decrease in dissolved flavonol concentration. The mechanism by which this decrease in solubility occurs was studied experimentally as well as by computational mesocscale particle dynamics simulations. The results suggest that phase separation of the polymer and flavonol during release from the solid dispersion is responsible for the time-dependent decrease in dissolved quercetin. It is suggested that the increase in release of quercetin in a PEG solid dispersion would only be beneficial if it were administered at the site of absorption, e.g. rectal administration, to ensure absorption prior to phase separation. The solid dispersions presented here would greatly improve the pharmaceutical availability of the flavonol at the site of absorption. Computational mesoscopic modeling was successfully applied to study the solid dispersions and corroborate experimental findings.     

Multicomponent complex formation between vinpocetine, cyclodextrins, tartaric acid and water-soluble polymers monitored by NMR and solubility studies.

This work deals with multicomponent complex formation of vinpocetine (VP) with beta-cyclodextrin (betaCD), sulfobutyl ether beta-cyclodextrin (SBEbetaCD) and tartaric acid (TA), in the presence or absence of water-soluble polymers, in aqueous solution. Complexation was monitored by phase-solubility and proton nuclear magnetic resonance ((1)H NMR) studies. TA demonstrated a synergistic effect on VP solubility, and in the complexation efficiency of betaCD and SBEbetaCD. Additionally, water-soluble polymers increased even more the complexation efficiency of the CDs that was reflected by a 2.1-2.5 increase on K(C) values for VP-CD-TA-polymer multicomponent complexes. SBEbetaCD was more effective in VP solubilization, as K(C) values of VP-SBEbetaCD-TA multicomponent complexes were notably higher than in corresponding betaCD complexes. The large chemical shift displacements from protons located in the interior of the hydrophobic CD cavities (i.e., H-3 and H-5) coupled with significant chemical shift displacements of VP aromatic protons suggested that this moiety was included in the cavity of both betaCD and SBEbetaCD. Two-dimensional rotating frame nuclear Overhauser effect spectroscopy (ROESY) experiments were carried out in order to obtain information about the multicomponent complex geometry in solution. Inspection of ROESY spectra allowed the establishment of spatial proximities between all aromatic protons of VP and the internal protons of the CDs, confirming that the aromatic moiety of VP is included in CD cavities being deeply inserted in SBEbetaCD multicomponent complexes, since additional interactions with the sulfobutyl side chains were evidenced.     

Recent progress in the computational prediction of aqueous solubility and absorption

The computational prediction of aqueous solubility and/or human absorption has been the goal of many researchers in recent years. Such an in silico counterpart to the biopharmaceutical classification system (BCS) would have great utility. This review focuses on recent developments in the computational prediction of aqueous solubility, P-glycoprotein transport, and passive absorption. We find that, while great progress has been achieved, models that can reliably affect chemistry and development are still lacking. We briefly discuss aspects of emerging scientific understanding that may lead to breakthroughs in the computational modeling of these properties.     

Combining computational and experimental evidence on the activity of antimalarial drugs on papain-like protease of SARS-CoV-2: A repurposing study

The development of inhibitors that target the papain-like protease (PLpro) has the potential to counteract the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the agent causing coronavirus disease 2019 (COVID-19). Based on a consideration of its several downstream effects, interfering with PLpro would both revert immune suppression exerted by the virus and inhibit viral replication. By following a repurposing strategy, the current study evaluates the potential of antimalarial drugs as PLpro inhibitors, and thereby the possibility of their use for treatment of SARS-CoV-2 infection. Computational tools were employed for structural analysis, molecular docking, and molecular dynamics simulations to screen antimalarial drugs against PLpro, and in silico data were validated by in vitro experiments. Virtual screening highlighted amodiaquine and methylene blue as the best candidates, and these findings were complemented by the in vitro results that indicated amodiaquine as a μM PLpro deubiquitinase inhibitor. The results of this study demonstrate that the computational workflow adopted here can correctly identify active compounds. Thus, the highlighted antimalarial drugs represent a starting point for the development of new PLpro inhibitors through structural optimization.