Piperine-hydroxybenzoate as phytochemistry antiosteoarthritis combination: Structural, solubility, and in vivo antiinflammatory study

This study discusses the composition and structure determination of a new multicomponent system from antiinflammatory natural ingredients, consisting of piperine (Pip) and 4-hydroxybenzoic acid (HBA), named Pip-HBA. In addition, this research studied its solubility and anti-inflammatory activity. After screening the stoichiometric proportions, this multicomponent system formation reaction was carried out using the solvent-dropped grinding and evaporation methods. Characterizations using solid analysis including differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD), and Fourier transform infrared spectroscopy (FTIR), confirmed the formation of Pip-HBA. These multicomponent systems showed different thermograms and diffractograms. Furthermore, the FTIR spectrum of Pip-HBA multicomponent system differs from the physical mixture and its constituent components. Single crystal diffractometry (SCXRD) determined Pip-HBA to be a new multicomponent system structure in three dimensions. Pip-HBA showed increased solubility and anti-inflammatory activity compared to single piperine. Therefore, Pip-HBA multicomponent system has quite potential for further preparation development.

Nanoscale colocalized thermal and chemical mapping of pharmaceutical powder aerosols

Inhalation of pharmaceutical aerosol formulations is widely used to treat respiratory diseases. Spatially resolved thermal characterization offers promise for better understanding drug release rates from particles; however, this has been an analytical challenge due to the small particle size (from a few micrometers down to nanometers) and the complex composition of the formulations. Here, we employ nano-thermal analysis (nanoTA) to probe the nanothermal domain of a pharmaceutical aerosol formulation containing a mixture of fluticasone propionate (FP), salmeterol xinafoate (SX), and excipient lactose, which is widely used to treat asthma and chronic obstructive pulmonary disease (COPD). Furthermore, atomic force microscopy-infrared spectroscopy (AFM-IR) and AFM force measurements are performed to provide nanochemical and nanomechanical information to complement the nanothermal data. The colocalized thermal and chemical mapping clearly reveals the surface heterogeneity of the drugs in the aerosol particles and demonstrates the contribution of the surface chemical composition to the variation in the thermal properties of the particles. We present a powerful analytical approach for in-depth characterization of thermal/chemical/morphological properties of dry powder inhaler particles at micro- and nanometer scales. This approach can be used to facilitate the comparison between generics and reference inhalation products and further the development of high-performance pharmaceutical formulations.

Preparation, Characterization, in-vitro and in-vivo Pharmacokinetic Evaluation of Thermostable Dimethyl Fumarate Cocrystals

Dimethyl fumarate (DMF) is an FDA-approved drug for treating relapsing-remitting multiple sclerosis; but it is susceptible to sublimation leading to its loss during processing. Cocrystals can protect against thermal energy via the interaction of DMF with a coformer via weak forces of interaction. With this hypothesis, we have, for the first time, prepared DMF cocrystals using the solvent evaporation method using coformers like citric acid and succinic acid screened by in-silico predictions and hydrogen bonding properties. Analysis using infra-red (IR), powder x-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and sublimation evaluation characterized cocrystals and their thermostability. Comparative analysis of the release profile has been done by dissolution and pharmacokinetic study of DMF and its cocrystals. The cocrystals have improved thermal stability and better pharmacological activities than DMF. In the safety and efficacy evaluation of the formulated cocrystals, they were found to be non-cytotoxic, antioxidant, and inhibiting IL-6 and TNF-α in PBMC induced by lipopolysaccharide (LPS). We have obtained cocrystals of DMF with improved thermal stability and better pharmacological activities than DMF.

Exploring the Co-Crystallization Landscape of One-Dimensional Coordination Polymers Using a Molecular Electrostatic Potential-Driven Approach

The ability of coordination polymers (CPs) to form multicomponent heteromeric materials, where the key structural features of the parent CP are retained, has been explored via molecular electrostatic potential-driven co-crystallization technologies. Thirteen co-formers presenting hydrogen-bond donors activated through a variety of electron-withdrawing functionalities were employed, and the extent of activation was evaluated using molecular electrostatic potential values. Attempted co-crystallizations of the seven most promising co-formers with a family of nine CPs ([CdX'2(X-pz)2]n; X' = I, Br, and Cl; X = I, Br, and Cl) resulted in six successful outcomes; all four of the structurally characterized compounds displayed the intended hydrogen bond. The rationalization of the main structural features revealed that strict structural and electrostatic requirements were imposed on effective co-formers; only co-formers with highly activated hydrogen-bond donors, and with a 1,4-orientation of electron-withdrawing moieties bearing effective acceptor sites, were successfully implemented into the three-dimensional architectures composed of one-dimensional building units of CPs.

Novel Gastroprotective and Thermostable Cocrystal of Dimethyl Fumarate: Its Preparation, Characterization, and In Vitro and In Vivo Evaluation

Crystallization has revolutionized the field of solid-state formulations by modulating the physiochemical and release profile of active pharmaceutical ingredients (APIs). Dimethyl fumarate (DF), an FDA-approved first-line drug for relapsing-remitting multiple sclerosis, has a sublimation problem, leading to loss of the drug during its processing. To tackle this problem, DF cocrystal has been prepared by using solvent evaporation technique using nicotinamide as a coformer, which has been chosen based on in silico predictions and their ability to participate in hydrogen bonding. Fourier transform infrared (FT-IR), powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and sublimation analysis have characterized the cocrystal and its thermostability. Comparative analysis of the release profile has been done by the dissolution and pharmacokinetic study of DF and its cocrystal. Formulated cocrystal is noncytotoxic, antioxidant and inhibits interleukin-6 and tissue necrosis factor-α in peripheral blood mononuclear cells induced by lipopolysaccharide. We have obtained a thermostable cocrystal of DF with a similar physicochemical and release profile to that of DF. The formulated cocrystal also provides a gastroprotective effect which helps counterbalance the adverse effects of DF by reducing lipid peroxidation and total nitrite levels.

Mitigating Drug Stability Challenges Through Cocrystallization

Drug stability plays a significant role in the pharmaceutical industry from early-phase drug discovery to product registration as well as the entire life cycle of a product. Various formulation approaches have been employed to overcome drug stability issues. These approaches are sometimes time-consuming which ultimately affect the timeline of the product launch and may further require formulation optimization steps, affecting the overall cost. Pharmaceutical cocrystal is a well-established route to fine tune the biopharmaceutical properties of drugs without covalent modification. This article highlights the role of cocrystallization in mitigating the stability issues of challenging drug molecules. Representative case studies wherein the drug stability issue is addressed through pharmaceutical cocrystals have been discussed briefly and are summarized in tabular form. The emphasis has been made on the structural information of cocrystals and understanding the mechanism that improves the stability of the parent drug through cocrystallization. Besides, a guided strategy has been proposed to modulate the stability of drug molecules through cocrystallization approach. Finally, the stability concern of fixed-dose or drug combinations and the challenges associated with cocrystals are also touched.

Understanding Hygroscopicity of Theophylline via a Novel Cocrystal Polymorph: A Charge Density Study

The charge density distribution in a novel cocrystal (1) complex of 1,3-dimethylxanthine (theophylline) and propanedioic acid (malonic acid) has been determined. The molecules crystallize in the triclinic, centrosymmetric space group P1̅, with four independent molecules (Z = 4) in the asymmetric unit (two molecules each of theophylline and malonic acid). Theophylline has a notably high hygroscopic nature, and numerous cocrystals have shown a significant improvement in stability to humidity. A charge density study of the novel polymorph has identified interesting theoretical results correlating the stability enhancement of theophylline via cocrystallization. Topological analysis of the electron density highlighted key differences (up to 17.8) in Laplacian (∇²ρ) between the experimental (EXP) and single-point (SP) models, mainly around intermolecular-bonded carbonyls. Further investigation via molecular electrostatic potential maps reaffirmed that the charge redistribution enhanced intramolecular hydrogen bonding, predominantly for N(2') and N(2) (61.2 and 61.8 kJ mol^-1, respectively). An overall weaker lattice energy of the triclinic form (-126.1 kJ mol^-1) compared to that of the monoclinic form (-133.8 kJ mol^-1) suggests a lower energy threshold to overcome to initiate dissociation. Future work via physical testing of the novel cocrystal in both dissolution and solubility will further solidify the correlation between theoretical and experimental results.

Synthesis, Characterization, and Intrinsic Dissolution Studies of Drug-Drug Eutectic Solid Forms of Metformin Hydrochloride and Thiazide Diuretics

The mechanochemical synthesis of drug–drug solid forms containing metformin hydrochloride (MET·HCl) and thiazide diuretics hydrochlorothiazide (HTZ) or chlorothiazide (CTZ) is reported. Characterization of these new systems indicates formation of binary eutectic conglomerates, i.e., drug–drug eutectic solids (DDESs). Further analysis by construction of binary diagrams (DSC screening) exhibited the characteristic V-shaped form indicating formation of DDESs in both cases. These new DDESs were further characterized by different techniques, including thermal analysis (DSC), solid state NMR spectroscopy (SSNMR), powder X-ray diffraction (PXRD) and scanning electron microscopy–energy dispersive X-ray spectroscopy analysis (SEM–EDS). In addition, intrinsic dissolution rate experiments and solubility assays were performed. In the case of MET·HCl-HTZ (χ_MET·HCl = 0.66), we observed a slight enhancement in the dissolution properties compared with pure HTZ (1.21-fold). The same analysis for the solid forms of MET·HCl-CTZ (χ_MET·HCl = 0.33 and 0.5) showed an enhancement in the dissolved amount of CTZ accompanied by a slight improvement in solubility. From these dissolution profiles and saturation solubility studies and by comparing the thermodynamic parameters (ΔH_fus and ΔS_fus) of the pure drugs with these new solid forms, it can be observed that there was a limited modification in these properties, not modifying the free energy of the solution (ΔG) and thus not allowing an improvement in the dissolution and solubility properties of these solid forms.

Co-Crystals of Etravirine by Mechanochemical Activation

The co-crystals formation of etravirine with three carboxylic acids was investigated. New co-crystals of etravirine with adipic acid, benzoic acid, and 4-hydroxybenzoic acid have been synthesized by wet milling of ingredients for 120 min. The novelty of these solid forms was first evidenced by powder X-ray diffraction. Their different morphology was evidenced by SEM microscopy. Spectroscopic analyses (FT-IR, MAS-NMR, and XPS) highlighted the hydrogen bonds between etravirine and co-formers, as a result of the solid-state reaction of the ingredients by wet milling. Thermal analyses pointed out that the milling process caused in co-crystals a reduction in the fusion enthalpy and the melting temperature, compared to the values obtained for etravirine. These co-crystals are stable up to four months on storage under extreme conditions, excepting the co-crystal with benzoic acid which begins to transform into a polymorph of etravirine after 30 days. The UV absorption spectra of the samples tested in three simulated physiological media with pH values of 6, 6.3, and 7 have evidenced the conformation change of etravirine due to hydrogen bonds between etravirine and carboxylic acids.

Pharmaceutical nanocrystals: A promising approach for improved topical drug delivery

The barrier function of skin and non-optimal physicochemical properties of drug present a challenge to skin penetration of many drugs, thus motivating the development of novel drug delivery systems. Recently, nanocrystal-based formulations have been investigated for topical drug delivery and demonstrated improved skin penetration. This review highlights barriers in skin penetration, current techniques to improve topical delivery and application of nanocrystals in conquering obstacles for topical delivery. Nanocrystals can improve delivery through the skin by mechanisms like higher concentration gradient across skin resulting in increased passive diffusion, hair follicle targeting, diffusional corona and adhesion to skin. This would be of interest for formulation scientists for product development of molecules that are 'difficult-to-deliver' topically.

Improving the solubility of anti-proliferative thieno[2,3-b]quinoline-2-carboxamides

Thieno[2,3-b]pyridines are a class of compounds known for their potent anti-proliferative activities against a range of human cancer cell lines. In this research, a number of strategies to generate analogues that have improved aqueous solubility whilst retaining the potent anti-proliferative actions, compared to previously-explored compounds in this class, were made. Herein we report the synthesis of 80 novel compounds, comprising two series, all based on the thieno[2,3-b]pyridine core structure. Overall, it was found that introducing alternative heterocycles did not notably improve the solubility or retain anti-proliferative activity seen in previously-reported analogues. However, pleasingly it was discovered, that the best strategy for improving the solubility was the alteration of the appended alkyl ring to introduce polar groups such as alcohols, ketones and substituted amine groups. In addition to this finding, we have discovered a thieno[2,3-b]pyridine, 15e, with greater aqueous solubility that has ever been seen for this class of compounds that is also a potent inhibitor of cancer cell growth, with IC₅₀'s in the nanomolar range. This new lead structure will form the basis of future explorations into this class of compounds.

Investigation of Poor Solubility of a Salt-Cocrystal Hydrate: A Case Study of the Common-Ion Effect in Betrixaban, an Anticoagulant Drug

Achieving the desired solubility and dissolution of active pharmaceutical ingredients (APIs) continues to be a big challenge in the pharmaceutical industry. In this regard, multicomponent solids of APIs such as salts and cocrystals have shown significant promise in resolving such solubility/dissolution issues. However, very little is known on how the APIs' solubility or dissolution is affected by the drug to coformer ratio in multicomponent solids. Betrixaban, is an anticoagulant drug approved in 2017 for the prevention of venous thromboembolism. During the alternate solid form development studies of the known betrixaban maleate, a rare multicomponent solid form, salt-cocrystal hydrate of betrixaban, was discovered and characterized thoroughly by spectroscopic, thermal, and X-ray crystallographic methods. Significantly, the new betrixaban maleate maleic acid hydrate (1:1:2:1) form has shown lower melting point (80 °C) as compared to its parent salt (197.5 °C). From such a large melting difference (117 °C) between the salt and salt-cocrystal hydrate of API, we anticipated substantially better solubility for the salt-cocrystal hydrate (low enthalpy). Furthermore, the predicted solubility also supported our anticipation. However, the powder dissolution tests at different pH conditions provided contrary results, that is, the salt-cocrystal hydrate showed 10 times lower solubility as compared to its salt. A detailed investigation, considering all the potential factors, revealed that "common-ion effect" could be a critical factor for the low solubility of the salt-cocrystal hydrate in which the API to coformer ratio is 1:3. To the best of our knowledge, this is the first case study on the solubility of pharmaceutical salt-cocrystal hydrates with an emphasis on "common-ion effect" or drug to coformer ratio.

Cocrystallization: Cutting Edge Tool for Physicochemical Modulation of Active Pharmaceutical Ingredients

Cocrystallization is a widely accepted and clinically relevant technique that has prospered very well over the past decades to potentially modify the physicochemical properties of existing active pharmaceutic ingredients (APIs) without compromising their therapeutic benefits. Over time, it has become an integral part of the pre-formulation stage of drug development because of its ability to yield cocrystals with improved properties in a way that other traditional methods cannot easily achieve. Cocrystals are solid crystalline materials composed of two or more than two molecules which are non-covalently bonded in the same crystal lattice. Due to the continuous efforts of pharmaceutical scientists and crystal engineers, today cocrystals have emerged as a cutting edge tool to modulate poor physicochemical properties of APIs such as solubility, permeability, bioavailability, improving poor mechanical properties and taste masking. The success of cocrystals can be traced back by looking at the number of products that are getting regulatory approval. At present, many cocrystals have obtained regulatory approval and they successfully made into the market place followed by a fair number of cocrystals that are currently in the clinical phases. Considering all these facts about cocrystals, the formulation scientists have been inspired to undertake more relevant research to extract out maximum benefits. Here in this review cocrystallization technique will be discussed in detail with respect to its background, different synthesis approaches, synthesis mechanism, application and improvements in drug delivery systems and its regulatory perspective.

Systematic comparison of racemic and enantiopure multicomponent crystals of phenylsuccinic acid—the role of chirality

Comparison of binary cocrystals of chiral and racemic carboxylic acids showed that the introduction of chiral building blocks may lead to the formation of subclasses of multicomponent crystals with unique Z′′/Z^r values combined with complex protonation stages of the molecules.

Mechanochemical cocrystallization to improve the physicochemical properties of chlorzoxazone

Cocrystals of chlorzoxazone prepared by mechanochemical cocrystallization with picolinic acid to improve the physicochemical properties.

Melting point–solubility–structure correlations in chiral and racemic model cocrystals

Comparison of chiral and racemic binary cocrystals showed that the chiral building block limits the formation of certain intermolecular interactions, decreases the packing efficiency, lowers the melting point and increases aqueous solubility.

Rapid Structure Determination of Molecular Solids Using Chemical Shifts Directed by Unambiguous Prior Constraints

NMR-based crystallography approaches involving the combination of crystal structure prediction methods, ab initio calculated chemical shifts and solid-state NMR experiments are powerful methods for crystal structure determination of microcrystalline powders. However, currently structural information obtained from solid-state NMR is usually included only after a set of candidate crystal structures has already been independently generated, starting from a set of single-molecule conformations. Here, we show with the case of ampicillin that this can lead to failure of structure determination. We propose a crystal structure determination method that includes experimental constraints during conformer selection. In order to overcome the problem that experimental measurements on the crystalline samples are not obviously translatable to restrict the single-molecule conformational space, we propose constraints based on the analysis of absent cross-peaks in solid-state NMR correlation experiments. We show that these absences provide unambiguous structural constraints on both the crystal structure and the gas-phase conformations, and therefore can be used for unambiguous selection. The approach is parametrized on the crystal structure determination of flutamide, flufenamic acid, and cocaine, where we reduce the computational cost by around 50%. Most importantly, the method is then shown to correctly determine the crystal structure of ampicillin, which would have failed using current methods because it adopts a high-energy conformer in its crystal structure. The average positional RMSE on the NMR powder structure is ⟨r_av⟩ = 0.176 Å, which corresponds to an average equivalent displacement parameter U_eq = 0.0103 Ų.

Prediction of Dissolution Data Integrated in Tablet Database Using Four-Layered Artificial Neural Networks

A large number of dissolution data were measured and integrated into a previously constructed tablet database composed of 14 kinds of compounds as model active pharmaceutical ingredients (APIs) with contents ranging from 10 to 80%. The database has contained physicochemical and powder properties of APIs, together with basic physical attributes of tablets such as the tensile strength and the disintegration time. In order to enhance the value of this database, drug dissolution data are essential to improving key information for designing tablet formulations. A four-layered artificial neural network (4LNN), newly implemented in commercially available software, was employed to predict dissolution data from physicochemical and powder properties of APIs. Our results showed that an excellent model for the prediction of dissolution data was achieved with 4LNN method. The function of 4LNN was appreciably better than that of conventional three-layered model, despite both models adopting the same number of nodes and algorithms for activation functions. Furthermore, linear regression models resulted in poor prediction of dissolution data.

Multicomponent solid forms of felodipine: preparation, characterisation, physicochemical and in-vivo studies

Objectives

This study aimed to improve biopharmaceutical parameters of the poorly soluble antihypertensive drug, felodipine, by preparing multicomponent solid forms using three coformers, viz. imidazole, nicotinamide and malonic acid.

Methods

The multicomponent solid forms were prepared by mechanochemical synthesis and characterised by various analytical techniques. These solid forms were further assessed for their physicochemical parameters. Pharmacokinetic and in-vivo antihypertensive activity was performed in rats.

Key findings

Felodipine (FEL) was found to be cocrystallised with imidazole (FEL-IM) while it formed eutectic with nicotinamide (FEL-NCT) and malonic acid (FEL-MA). Cocrystal was sustained by NH…N and NH….O hydrogen-bonded network. Solubility and intrinsic dissolution studies in 0.1 N HCl (pH 1.2) revealed that eutectics exhibited higher solubility and release rate than cocrystal vis-a-vis pure drug and were found to be stable under accelerated storage condition. Significant enhancement of bioavailability was observed in eutectics (3.5- to twofold) and cocrystal (1.3-fold) compared with the pure drug. Antihypertensive activity of new solid forms in an animal model showed a marked decrease in systolic blood pressure.

Conclusions

Mechanochemical approach was successful to prepare multicomponent solid forms that have the potential to improve biopharmaceutical parameters of the poorly soluble drug, FEL.

Crystal structures and physicochemical properties of diltiazem base and its acetylsalicylate, nicotinate and l-malate salts

Molecular salts of diltiazem with aspirin, niacin and l-malic acid have been synthesized. Their crystal structures and physicochemical properties have been investigated.

Molecular salts of propranolol with dicarboxylic acids: diversity of stoichiometry, supramolecular structures and physicochemical properties

Crystallization of the drug propranolol with dicarboxylic acids yielded molecular salts with oxalic and fumaric acids in molar ratios of 1 : 1 and 2 : 1, with maleic acid in a molar ratio of 1 : 1.