Mebendazolium mesylate anhydride salt: rational design based on supramolecular assembly, synthesis, and solid-state characterization

The design mebendazole (MBZ) multicomponent systems is important to obtain new materials that incorporate the API (active pharmaceutical ingredient) with better thermal stability, avoiding the interconversion of desmotropes. Interestingly, the presence of water molecules in the mebendazolium mesylate monohydrate prevents the formation of the R22(8) supramolecular synthon, found in all mebendazolium salts with polyatomic counterions. Here, we designed a new mebendazolium mesylate anhydrous salt based on statistical scrutiny of all mebendazole crystal structures identified in the literature and an exhaustive analysis of the conformational and geometrical requirements for the supramolecular assembly. The synthesis of this new salt and its solid-state characterization through single-crystal X-ray diffraction and complementary techniques are presented. As expected, mebendazole recrystallization in methanol with methanesulfonic acid - a Food and Drug Administration accepted coformer - in the absence of water yields a mesylate anhydrous salt with 1 : 1 stoichiometry. This new salt crystallizes in the P212121 (19) space group. The main intermolecular interactions found in the crystal structure are the hydrogen bonds that form a R22(8) supramolecular motif that assembles the ionic pairs. Additional non-classical H-bond, as well as π⋯π and carbonyl⋯cation interactions, contribute to the final stabilization of the crystal packing. This new salt is stable up to 205 °C when it undergoes the endothermic loss of the ester moiety to yield 2-amino-5-benzoylbenzimidazole. Moreover, preliminary dissolution experiments in aqueous 0.1 mol L-1 HCl suggest an apparent solubility of mebendazolium mesylate anhydride 2.67 times higher than that of the preferred for pharmaceutical formulations MBZ form C.

Structural features, dissolution performance and anthelmintic efficacy of multicomponent solid forms of fenbendazole with maleic and oxalic acids

Two new multicomponent crystalline phases of fenbendazole (FNB), a benzimidazole anthelmintic agent, with maleic and oxalic acids have been prepared, and their structural and physicochemical properties carefully investigated.

Crystal Engineering of Ionic Cocrystals Sustained by Azolium···Azole Heterosynthons

Crystal engineering of multi-component molecular crystals, cocrystals, is a subject of growing interest, thanks in part to the potential utility of pharmaceutical cocrystals as drug substances with improved properties. Whereas molecular cocrystals (MCCs) are quite well studied from a design perspective, ionic cocrystals (ICCs) remain relatively underexplored despite there being several recently FDA-approved drug products based upon ICCs. Successful cocrystal design strategies typically depend on strong and directional noncovalent interactions between coformers, as exemplified by hydrogen bonds. Understanding of the hierarchy of such interactions is key to successful outcomes in cocrystal design. We herein address the crystal engineering of ICCs comprising azole functional groups, particularly imidazoles and triazoles, which are commonly encountered in biologically active molecules. Specifically, azoles were studied for their propensity to serve as coformers with strong organic (trifluoroacetic acid and p-toluenesulfonic acid) and inorganic (hydrochloric acid, hydrobromic acid and nitric acid) acids to gain insight into the hierarchy of NH+···N (azolium-azole) supramolecular heterosynthons. Accordingly, we combined data mining of the Cambridge Structural Database (CSD) with the structural characterization of 16 new ICCs (11 imidazoles, 4 triazoles, one imidazole-triazole). Analysis of the new ICCs and 66 relevant hits archived in the CSD revealed that supramolecular synthons between identical azole rings (A+B−A) are much more commonly encountered, 71, than supramolecular synthons between different azole rings (A+B−C), 11. The average NH+···N distance found in the new ICCs reported herein is 2.697(3) Å and binding energy calculations suggested that hydrogen bond strengths range from 31–46 kJ mol−1. The azolium-triazole ICC (A+B−C) was obtained via mechanochemistry and differed from the other ICCs studied as there was no NH+···N hydrogen bonding. That the CNC angles in imidazoles and 1,2,4-triazoles are sensitive to protonation, the cationic forms having larger (approximately 4.4 degrees) values than comparable neutral rings, was used as a parameter to distinguish between protonated and neutral azole rings. Our results indicate that ICCs based upon azolium-azole supramolecular heterosynthons are viable targets, which has implications for the development of new azole drug substances with improved properties.

Heterologous-coating antigen enhancing the sensitivity of enzyme-linked immunosorbent assay for detection of mebendazole residues

The heterologous strategy could improve the sensitivity of competitive enzyme-linked immunosorbent assay (ELISA) for detection of chemical contaminants in food samples. In this study, the heterologous coating antigen ELISA was developed to evaluate its sensitivity for mebendazole (MBZ). Results showed that the heterologous ELISA had a linear range of (IC₂₀-IC₈₀) 0.34-10.54 ng/mL, an IC₅₀ value of 1.83 ng/mL, and a limit of detection (LOD) of 0.13 ng/mL, in which the sensitivity of ELISA improved 1.7- and 2-fold (IC₅₀ value dropping from 7.41 and 3.65 ng/mL to 4.27 and 1.83 ng/mL) than that of rabbit IgG- and chicken IgY-based homologous ELISA for MBZ, respectively. The heterologous coating antigen ELISA showed negligible cross reactivity (<0.2%) with its structural analogues, including hydroxy-MBZ, albendazole, oxfendazole, fenbendazole, and flubendazole, except the value of 72.6% for amino-MBZ. The average recoveries of MBZ spiked in pork and chicken muscle samples by the assay ranged from 83.7% to 109.8% and agreed well with those of high-performance liquid chromatography. The results suggested that using heterologous coating antigen could distinctly improve the sensitivity of ELISA for routine screening of MBZ residues in food samples.

Development of a sensitive chicken IgY-based enzyme-linked immunosorbent assay for detection of mebendazole in pork and mutton

Chicken egg yolk IgY has proven to be qualified for analysis of targets in immunoassays. In order to explore the feasibility of chicken IgY-based ELISA for detection of mebendazole (MEB), the chicken IgY against MEB was generated in the laying hens. An enzyme-linked immunosorbent assay (ELISA) based on chicken IgY was developed for detection of MEB with a half-maximum signal inhibition concentration (IC₅₀) of 3.65 ng mL^-1 and a limit of detection of 0.25 ng mL^-1. The assay showed a lower cross reactivity (less than 1%) with other structures analogues (except amino-MEB with the values of 70.7%). The average recoveries of MEB spiked in pork and mutton muscle samples ranged from 93.6% to 106.3% with relative standard deviation less than 8.78% and 10.85% for intra-assay and inter-assay, respectively, and agreed well with those of high-performance liquid chromatography. Our results indicate that generated IgY could be used as a robust reagent for routine screening analysis of small molecular compounds residues in food samples.

Development of an enzyme-linked immunosorbent assay for the detection of mebendazole in chicken and mutton

Mebendazole (MBZ), a synthetic benzimidazole, is most widely used for the treatment of intestinal helminthiasis. In the present study, a hapten mimicking the MBZ structure was designed by introducing propanoic acid and coupling to carrier proteins by the active ester method to immunize New Zealand rabbits. A sensitive enzyme-linked immunosorbent assay (ELISA) was developed for the analysis of MBZ in food samples. The rabbit IgG based ELISA had a half-maximum inhibition concentration (IC₅₀) of 7.41 ng mL^-1, with a limit of detection of 0.27 ng mL^-1. The ELISA showed negligible cross reactivity (<1%) with structural analogs, including hydroxy-MBZ, albendazole, oxfendazole, fenbendazole, flubendazole and oxfendazole, except the value of 90.5% for amino-MBZ. The average recoveries of MBZ spiked in chicken and mutton muscle samples by the assay ranged from 84.31% to 106.28% and agreed well with those of high-performance liquid chromatography. The above results indicated that the generated anti-MBZ IgG-based ELISA showed promise in routine screening analysis of MBZ residues in food samples.

Molecular salts of quinine: a crystal engineering route to enhance the aqueous solubility

Salts of quinine, with α,ω-aliphatic dicarboxylic acids, and aromatic coformers, show superior aqueous solubility. The structural, thermal and microscopy data provide structural, compositional, and stability profiles of the salts.

A cocrystal of L-ascorbic acid with picolinic acid: the role of O-H...O, N-H...O and C-H...O hydrogen bonds and L-ascorbic acid conformation in structure stabilization

A new 1:1 cocrystal (L-Asc-Pic) of L-ascorbic acid (vitamin C) with picolinic acid was prepared as a powder and as single crystals. The crystal structure was solved and refined from single-crystal X-ray diffraction (SCXRD) data collected at 293 (2) and 100 (2) K. The samples of the L-Asc-Pic cocrystal were characterized by elemental (HCNS) analysis and titrimetric methods, TG/DTG/DSC, and IR and Raman spectroscopy. The asymmetric unit comprises a picolinic acid zwitterion and an L-ascorbic acid molecule. The stabilization energy of intermolecular interactions involving hydrogen bonds, the vibrational spectrum and the energies of the frontier molecular orbitals were calculated using the GAUSSIAN09 and the CrystalExplorer17 programs. The charge distribution on the atoms of the L-Asc-Pic cocrystal, L-ascorbic acid itself and its 12 known cocrystals (structures from Version 5.40 of the Cambridge Structural Database) were calculated by the methods of Mulliken, Voronoi and Hirshfeld charge analyses (ADF) at the bp86/TZ2P+ level of theory. The total effective charges and conformations of the L-ascorbic acid molecules in the new and previously reported cocrystals were compared with those of the two symmetry-independent molecules in the crystals of L-ascorbic acid. A correlation between molecular conformation and its effective charge is discussed.

Preparation and Evaluation of Mebendazole Microemulsion for Intranasal Delivery: an Alternative Approach for Glioblastoma Treatment

Although mebendazole (MBZ) has demonstrated antitumor activity in glioblastoma models, the drug has low aqueous solubility and therefore is poorly absorbed. Considering that other strategies are needed to improve its bioavailability, the current study was aimed to develop and evaluate novel microemulsions of MBZ (MBZ-NaH ME) for intranasal administration. MBZ raw materials were characterized by FTIR, DSC, and XDP. Subsequently, the raw material that contained mainly polymorph C was selected to prepare microemulsions. Two different oleic acid (OA) systems were selected. Formulation A was composed of OA and docosahexaenoic acid (3:1% w/w), while formulation B was composed of OA and Labrafil M2125 (1:1% w/w). Sodium hyaluronate (NaH) at 0.1% was selected as a mucoadhesive agent. MBZ MEs showed a particle size of 209 nm and 145 nm, respectively, and the pH was suitable for nasal formulations (4.5-6.5). Formulation B, which showed the best solubility and rheological behavior, was selected for intranasal evaluation. The nasal toxicity study revealed no damage in the epithelium. Furthermore, formulation B improved significantly the median survival time in the orthotopic C6 rat model compared to the control group. Moreover, NIRF signal intensity revealed a decrease in tumor growth in the treated group with MBZ-MaH ME, which was confirmed by histologic examinations. Results suggest that the intranasal administration of mebendazole-loaded microemulsion might be appropriated for glioblastoma treatment. Graphical abstract.

Combined X-ray Crystallographic, IR/Raman Spectroscopic, and Periodic DFT Investigations of New Multicomponent Crystalline Forms of Anthelmintic Drugs: A Case Study of Carbendazim Maleate

Synthesis of multicomponent solid forms is an important method of modifying and fine-tuning the most critical physicochemical properties of drug compounds. The design of new multicomponent pharmaceutical materials requires reliable information about the supramolecular arrangement of molecules and detailed description of the intermolecular interactions in the crystal structure. It implies the use of a combination of different experimental and theoretical investigation methods. Organic salts present new challenges for those who develop theoretical approaches describing the structure, spectral properties, and lattice energy Elatt. These crystals consist of closed-shell organic ions interacting through relatively strong hydrogen bonds, which leads to Elatt > 200 kJ/mol. Some technical problems that a user of periodic (solid-state) density functional theory (DFT) programs encounters when calculating the properties of these crystals still remain unsolved, for example, the influence of cell parameter optimization on the Elatt value, wave numbers, relative intensity of Raman-active vibrations in the low-frequency region, etc. In this work, various properties of a new two-component carbendazim maleate crystal were experimentally investigated, and the applicability of different DFT functionals and empirical Grimme corrections to the description of the obtained structural and spectroscopic properties was tested. Based on this, practical recommendations were developed for further theoretical studies of multicomponent organic pharmaceutical crystals.

A novel lurasidone hydrochloride–shikimic acid co-amorphous system formed by hydrogen-bonding interaction with the retained pH-dependent solubility behavior

The current study was aimed at investigating the lurasidone hydrochloride–shikimic acid co-amorphous system using a new type of organic acid.

The dynamics of ovine gastrointestinal nematode infections within ewe and lamb cohorts on three Scottish sheep farms

Gastrointestinal nematodes (GIN) are a serious concern for sheep producers worldwide. However, there is a paucity of evidence describing the epidemiology of GIN on modern UK sheep farms. The aim of this paper was to understand whether expected seasonal variations of infection are still found in ewes and lambs under varying management strategies in temperate climates. Faecal egg counts (FEC) were conducted on freshly voided samples collected from groups of ewes and lambs every third week for twelve months on three farms in southeast Scotland. The patterns of egg output have been described here in relation to management practices undertaken on the farms. Despite changes in farming practice and climatic conditions, the findings complement historical studies detailing the epidemiology of GIN. Findings include a periparturient rise in ewe FEC on two of the farms, while lambing time treatment appeared to suppress this on the third farm. On the same two farms lamb FEC increased during the summer, reaching a peak in the autumn. The work also highlights how the ad hoc use of anthelmintics does little to impact these patterns.

Spectrophotometric and photocatalytic studies of H-bonded charge transfer complex of oxalic acid with imidazole: single crystal XRD, experimental and DFT/TD-DFT studies

The photocatalytic activity of a new CT complex was tested. Spectrophotometric studies were performed to understand its formation through N⁺–H⋯O⁻ hydrogen bonding, and the structure was confirmed by single crystal XRD.

Crystal structure of a 1:1 salt of 4-amino-benzoic acid (vitamin B10) with pyrazinoic acid

The title 1:1 salt, C7H8NO2 +·C5H3N2O2 - (systematic name: 4-carb-oxy-anilinium pyrazine-2-carboxyl-ate), was synthesized successfully by slow evaporation of a saturated solution from water-ethanol (1:1 v/v) mixture and characterized by X-ray diffraction (SCXRD, PXRD) and calorimetry (DSC). The crystal structure of the salt was solved and refined at 150 and 293 K. The salt crystallizes with one mol-ecule of 4-amino-benzoic acid (PABA) and one mol-ecule of pyrazinoic acid (POA) in the asymmetric unit. In the crystal, the PABA and POA mol-ecules are associated via COOH⋯Narom heterosynthons, which are connected by N-H⋯O hydrogen bonds, creating zigzag chains. The chains are further linked by N-H⋯O hydrogen bonds and π-π stacking inter-actions along the b axis [centroid-to-centroid distances = 3.7377 (13) and 3.8034 (13) Å at 150 and 293 K, respectively] to form a layered three-dimensional structure.

Improved Solubility of Vortioxetine Using C2-C4 Straight-Chain Dicarboxylic Acid Salt Hydrates

The purpose of this study was to improve the solubility of vortioxetine by crystal engineering principles. In this paper, three C2-C4 straight-chain dicarboxylic acid salt hydrates of vortioxetine (VOT-OA, VOT-MA-H2O, and VOT-SUA-H2O, VOT = vortioxetine, OA = Oxalic acid, MA = malonic acid, SUA = succinic acid) were synthesized and characterized by single X-ray diffraction, powder X-ray diffraction, and differential scanning calorimetry. The single crystal structure of three salts reveals that vortioxetine has torsional flexibility, which can encourage VOT to allow combination with aliphatic dicarboxylic acids through N+-H···O hydrogen bonds. The solubility of all salts exhibits a dramatic increase in distilled water, especially for VOT-MA-H2O salt, where it shows the highest solubility, by 96-fold higher compared with pure vortioxetine.

Pharmaceutical cocrystallization: an effective approach to modulate the physicochemical properties of solid-state drugs

This highlight presents an update on applications of cocrystallization to modify properties relevant to efficacy, safety, and manufacturability of drugs.

Novel pharmaceutical salts of albendazole

Novel pharmaceutical salts of albendazole drugs are crystallized with sulfonic acids and carboxylic acids. The disorder of the thiopropyl chain in the parent crystal structure is resolved in the salt crystal structures.

Density functional theory modelling of protective agents for carbonate stones: a case study of oxalate and oxamate inorganic salts

DFT calculations allowed investigating the ability of oxalate monoesters and monoamides salts to act as protective agents for carbonate stones, such as marble or limestones, of historical interest in the field of cultural heritage.

Structural characterization and dissolution profile of mycophenolic acid cocrystals

Three novel cocrystals of mycophenolic acid (MPA) with isonicotinamide (MPA-ISO), minoxidil (MPA-MIN) and 2,2'-dipyridylamine (MPA-DPA) as coformers have been prepared successfully by both slow evaporation and liquid-assisted grinding. The structures of these cocrystals show that all the three coformers form hydrogen bonds with the carboxylic acid group of MPA. The cocrystal MPA-ISO possesses remarkably improved solubility and dissolution rate, while two other cocrystals exhibit the opposite characteristics. The solids in the slurry with pH6.8 phosphate buffer and cocrystals remain as the incipient cocrystal after 24h. However, evidence of slight polymerization was shown in the slurry of pH6.8 phosphate buffer with MPA and MPA-ISO cocrystal.

New multi-component solid forms of anti-cancer drug Erlotinib: role of auxiliary interactions in determining a preferred conformation

Erlotinib is a BCS (biopharmaceutical classification system) class II drug used for the treatment of non-small cell lung cancer. There is an urgent need to obtain new solid forms of higher solubility to improve the bioavailability of the API (active pharmaceutical ingredient). In this context, cocrystals with urea, succinic acid, and glutaric acid and salts with maleic acid, adipic acid, and saccharin were prepared via wet granulation and solution crystallizations. Crystal structures of the free base (Z' = 2), cocrystals of erlotinib-urea (1:1), erlotinib-succinic acid monohydrate (1:1:1), erlotinib-glutaric acid monohydrate (1:1:1) and salts of erlotinib-adipic acid adipate (1:0.5:0.5) are determined and their hydrogen-bonding patterns are analyzed. Self recognition via the (amine) N-H...N (pyridine) hydrogen bond between the API molecules is replaced by several heterosynthons such as acid-pyridine, amide-pyridine and carboxylate-pyridinium in the new binary systems. Auxiliary interactions play an important role in determining the conformation of the API in the crystal. FT-IR spectroscopy is used to distinguish between the salts and cocrystals in the new multi-component systems. The new solid forms are characterized by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) to confirm their unique phase identity.

Salt screening and characterization of ciprofloxacin

With the aim of improving the solubility of ciprofloxacin, polybasic organic acids were utilized to react with ciprofloxacin in different stoichiometric proportions. The use of the solvent drop grinding (SDG) method, as well as the solvent evaporation method, resulted in the crystalline salts ciprofloxacin/fumaric acid (1:1, 2:1), ciprofloxacin/maleic acid (1:1) and ciprofloxacin/citric acid (2:1). The solubilities of these salts in pure water (pH 7.0) were determined using high-performance liquid chromatography (HPLC) at 310 K, with the salts showing considerably greater solubility than ciprofloxacin itself and, interestingly, ciprofloxacin/fumaric acid (2:1) being more soluble than ciprofloxacin/fumaric acid (1:1). Intrigued by this phenomenon, we undertook a comparison of the crystal structures of the salts: the three-dimensional sandwich-like structure observed in the 2:1 salt indicates that the preferred stacking may be a factor in increasing the solubility of ciprofloxacin.

Cocrystals of Hydrochlorothiazide: Solubility and Diffusion/Permeability Enhancements through Drug-Coformer Interactions

Hydrochlorothiazide (HCT) is a diuretic and a BCS class IV drug with low solubility and low permeability, exhibiting poor oral absorption. The present study attempts to improve the physicochemical properties of the drug using a crystal engineering approach with cocrystals. Such multicomponent crystals of HCT with nicotinic acid (NIC), nicotinamide (NCT), 4-aminobenzoic acid (PABA), succinamide (SAM), and resorcinol (RES) were prepared using liquid-assisted grinding, and their solubilities in pH 7.4 buffer were evaluated. Diffusion and membrane permeability were studied using a Franz diffusion cell. Except for the SAM and NIC cocrystals, all other binary systems exhibited improved solubility. All of the cocrystals showed improved diffusion/membrane permeability compared to that of HCT with the exception of the SAM cocrystal. When the solubility was high, as in the case of PABA, NCT, and RES cocrystals, the flux/permeability dropped slightly. This is in agreement with the expected interplay between solubility and permeability. Improved solubility/permeability is attributed to new drug-coformer interactions. Cocrystals of SAM, however, showed poor solubility and flux. This cocrystal contains a primary sulfonamide dimer synthon similar to that of HCT polymorphs, which may be a reason for its unusual behavior. Hirshfeld surface analysis was carried out in all cases to determine whether a correlation exists between cocrystal permeability and drug-coformer interactions.

Thermodynamics and preliminary pharmaceutical characterization of a melatonin–pimelic acid cocrystal prepared by a melt crystallization method

The binary phase diagram and formation enthalpy provided in depth understanding and guidance on the melt crystallization of the melatonin–pimelic acid cocrystal.

Synthon polymorphs of 1 : 1 co-crystal of 5-fluorouracil and 4-hydroxybenzoic acid: their relative stability and solvent polarity dependence of grinding outcomes

Two synthon polymorphs of 1 : 1 co-crystals of 5-fluorouracil and 4-hydroxybenzoic acid were synthesized, and the crystal structures were determined.

The delivery of triamterene by cucurbit[7]uril: synthesis, structures and pharmacokinetics study

In recent years, cucurbit[7]uril (CB[7]) has attracted great attention in drug delivery. Though the effect of CB[7] in enhancing the solubility of water insoluble drugs has been validated, the underlying mechanism remains poorly understood, particularly at a molecular level. This study is designed to evaluate a CB[7]-based pharmaceutical formulation to improve solubility and bioavailability of triamterene (a mild potassium-sparing diuretic). Two polymorphs of triamterene@CB[7] were obtained, and their crystal structures were determined by single crystal X-ray diffraction. The CB[7] molecule forms a stable host-guest complex with triamterene (Ka = 1.69 ± 0.34 × 10(4) M(-1)) in aqueous solution (pH = 1.0). The results of dissolution study demonstrate that the apparent solubility value of triamterene@CB[7] complex in 0.1 M HCl is 1.6 times as large as that of triamterene, while free triamterene was released from triamterene@CB[7] complex in phosphate buffer of pH 6.8. Pharmacokinetic studies in rats reveal that the AUC0-∞ value of triamterene@CB[7] complex increases 2.8-fold compared with that of free triamterene, and t1/2 is prolonged from 1.42 to 2.61 h (P < 0.05) after oral administration. The increased solubility and oral bioavailability are attributed to the formation of a hydrophilic capsule composed of two CB[7] molecules, in which two insoluble triamterene molecules are encapsulated. These results demonstrate that triamterene@CB[7] complex is a stable and effective pharmaceutical formulation.