Pharmaceutical salts of emoxypine with dicarboxylic acids

Influence of Co-amorphization on the Physical Stability and Dissolution Performance of an Anthelmintic Drug Flubendazole

In this work, the co-amorphization approach was applied to flubendazole (FluBZ), resulting in the formation of two novel solid forms of FluBZ with l-phenylalanine (Phe) and l-tryptophan (Trp). A variety of physicochemical techniques have been used to describe new systems, including powder X-ray diffraction, thermal methods, infrared spectroscopy, and scanning electron microscopy. Co-amorphization has been shown to suppress crystallization tendency and considerably increase the shelf-life storage of amorphous flubendazole solid across a wide range of relative humidities. The dissolution behavior of the amorphous forms in biorelevant media at pH = 1.6, pH = 6.5, and 37 °C has been studied in terms of C_max (maximum FluBZ concentration), T_max (time to attain peak drug concentration), and AUC (concentration area under the curve during dissolution). At pH = 6.5, a continuous supersaturation and the highest AUC value of all examined systems were observed for the FluBZ-Phe (1:1) system. The phase solubility diagrams revealed that the reason for the better dissolution performance of FluBZ-Phe (1:1) at pH = 6.5 is a complexation between the components in a solution. This work highlights the applicability of co-amorphous systems in improving the physical stability and dissolution performance of drug compounds with poor biopharmaceutical characteristics.

New Solid Forms of Nitrofurantoin and 4-Aminopyridine Salt: Influence of Salt Hydration Level on Crystal Packing and Physicochemical Properties

The crystallization of the poorly soluble drug nitrofurantoin (NFT) with 4-aminopyridine (4AmPy) resulted in three multicomponent solid forms with different hydration levels: anhydrous salt [NFT+4AmPy] (1:1), salt monohydrate [NFT+4AmPy+H₂O] (1:1:1), and salt tetrahydrate [NFT+4AmPy+H₂O] (1:1:4). Each salt was selectively prepared by liquid-assisted grinding in the presence of acetonitrile or ethanol/water mixture at a specific composition. The NFT hydrated salts were characterized using single crystal X-ray diffraction. The [NFT+4AmPy+H₂O] salt (1:1:1) crystallized as an isolated site hydrate, while the [NFT+4AmPy+H₂O] salt (1:1:4) crystallized as a channel hydrate. The dehydration processes of the NFT salt hydrates were investigated using differential scanning calorimetry and thermogravimetric analysis. A powder dissolution experiment was carried out for all NFT multicomponent solid forms in pH 7.4 phosphate buffer solution at 37 °C.

Promising effects of emoxypine and its succinate derivative in the management of various diseases-with insights on recent patent applications

Emoxypine and its succinate derivative share a common hydroxypridine structure, which is similar to pyridoxine. These compounds have been utilized therapeutically and industrially, owing to the wide range of properties offered. This includes antihypoxic, neuroprotective and cardioprotective effects, along with pharmacokinetic benefits such as the ability to cross the blood brain barrier (BBB), owing to its relatively small size and low molecular weight. It was observed that emoxypine exhibited iron chelating property in vitro, indicating its usage as a promising therapeutic strategy in the management of neurodegenerative conditions such as Alzheimer's disease (AD), as well as hematologic disorders like thalassemia and hemochromatosis. In addition to this, it has been observed to exert a potent antioxidant effect, therefore, it may be considered for the amelioration of disorders resulting from free radical injury. Studies on its mechanism of action and implications on cellular and molecular levels would help to further the understanding of its benefits, as well as prospects for filing patents for novel applications. The primary focus of this review is to shed light on the broad spectrum of pharmacological properties offered by emoxypine and its succinate derivative, and to highlight the scope for an increased number of pre-clinical and clinical trials to assess its safety and efficacy. In addition to this, the highlights of this article include the recent patents filed and scope for novel applications of these agents.

A combined experimental and theoretical study of miconazole salts and cocrystals: crystal structures, DFT computations, formation thermodynamics and solubility improvement

Experimental and theoretical screening of multi-component crystal forms of miconazole (MCL), an antifungal drug, with ten aliphatic dicarboxylic acids was performed. Seven multi-component molecular crystals were isolated and identified by different analytical techniques, including the powder X-ray diffractometry (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TG), and solubility methods. The crystal structures of the MCL hemihydrate, two cocrystals with succinic ([MCL + SucAc] (2 : 1)) and fumaric acids ([MCL + FumAc] (2 : 1)) and one salt with maleic acid ([MCL + MleAc] (1 : 1)) were redetermined. The new cocrystal of MCL with adipic acid ([MCL + AdpAc] (2 : 1)) was investigated by single crystal X-ray diffractometry. It was found that the AdpAc molecule in the cocrystal has an unusual anticlinal conformation. The combination of periodic density functional theory (DFT) computations and quantum topology analysis confirmed the structure-directing role of the acid-imidazole heterosynthon for the considered crystals. The melting temperatures of all the studied multi-component crystals are between the values of the corresponding individual components except [MCL + MleAc] (1 : 1). A thermal analysis has shown that the thermodynamic and thermophysical characteristics of the considered two-component molecular crystals are strongly dependent both on specific interactions (presence of sites of donor-acceptor interactions and hydrogen bond formation) and on nonspecific interactions - molecule polarizability. Based on the sublimation thermodynamics database of molecular crystals, the standard sublimation thermodynamic functions of MCL were evaluated. The thermodynamic functions of multi-component crystal formation based on MCL were calculated and analyzed. Solubility experiments on the MCL multi-component crystals were carried out in isotonic aqueous buffer solutions at pH 1.2 and 6.8 and compared with the solubility of the MCL free base and its nitrate salt. It was found that the salt/cocrystal formation of MCL with dicarboxylic acids considerably increased the MCL solubility in pH 6.8 buffer. The biggest MCL solubility enhancement was observed in the [MCL + TartAc] (1 : 1) salt. The solubility value of MCL in the [MCL + TartAc] (1 : 1) salt is commensurate with the commercial MCL nitrate salt.

Two Faces of Water in the Formation and Stabilization of Multicomponent Crystals of Zwitterionic Drug-Like Compounds

Two new hydrated multicomponent crystals of zwitterionic 2-aminonicotinic acid with maleic and fumaric acids have been obtained and thoroughly characterized by a variety of experimental (X-ray analysis and terahertz Raman spectroscopy) and theoretical periodic density functional theory calculations, followed by Bader analysis of the crystalline electron density) techniques. It has been found that the Raman-active band in the region of 300 cm−1 is due to the vibrations of the intramolecular O-H...O bond in the maleate anion. The energy/enthalpy of the intermolecular hydrogen bonds was estimated by several empirical approaches. An analysis of the interaction networks reflects the structure-directing role of the water molecule in the examined multicomponent crystals. A general scheme has been proposed to explain the proton transfer between the components during the formation of multicomponent crystals in water. Water molecules were found to play the key role in this process, forming a “water wire” between the COOH group of the dicarboxylic acid and the COO– group of the zwitterion and the rendering crystal lattice of the considered multicomponent crystals.

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.

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.