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1.
  • Alhalaweh, Amjad, et al. (författare)
  • 1:1 and 2:1 urea-succinic acid cocrystals : structural diversity, solution chemistry, and thermodynamic stability
  • 2010
  • Ingår i: Crystal Growth & Design. - : American Chemical Society. - 1528-7483 .- 1528-7505. ; 10:11, s. 4847-4855
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this work was to study the crystal structures of 1:1 and 2:1 urea-succinic acid (U-SA) cocrystals and to investigate the role of solution chemistry in the formation and stability of different stoichiometric cocrystals. The structural diversity of other urea-dicarboxylic acid cocrystals is also discussed. The 1:1 U-SA cocrystal was stabilized by an acid-amide heterosynthon while acid-amide heterosynthons and amide-amide homosynthons stabilized the 2:1 cocrystals. The hydrogen bonding motifs in 1:1 and 2:1 U-SA cocrystals were consistent with other urea-dicarboxylic acid systems with similar stoichiometries. The 1:1 cocrystals were transformed to 2:1 cocrystals upon slurrying in various solvents at 25 °C. The phase solubility diagram was used to define the stability regions of different solid phases in 2-propanol at 25 °C. While no phase stability region for 1:1 cocrystal could be found, the stable regions for the 2:1 cocrystals and their pure components were defined by eutectic points. The solubility of the 2:1 cocrystals was dependent on the concentration of the ligand in the solution and explained by the solubility product and 1:1 solution complexation. The mathematical models predicting the solubility of the 2:1 cocrystals were evaluated and found to fit the experimental data
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2.
  • Alhalaweh, Amjad, et al. (författare)
  • Solubility behavior and solution chemistry of indomethacin cocrystals in organic solvents
  • 2011
  • Ingår i: Crystal Growth & Design. - 1528-7483 .- 1528-7505. ; 11:9, s. 3923-3929
  • Tidskriftsartikel (refereegranskat)abstract
    • The main objective of this study was to investigate the solubility behavior and solution chemistry of indomethacin-saccharin (IND-SAC) cocrystals in organic media. We also evaluated previously proposed models of cocrystal solubility in organic solvents. In addition, the solubility behavior of IND-SAC cocrystals was compared with that of indomethacin-nicotinamide (IND-NIC) cocrystals using the eutectic constant approach. Phase solubility diagrams of IND-SAC cocrystals in various solvents were generated and the transition concentrations, at which drug and cocrystals are in equilibrium with the solvents, were determined. The solubility of IND-SAC cocrystals was explained by the solubility product and solution complexation. The tested models were found to fit the experimental data and to adequately explain the solubility behavior of the cocrystals. The solution complexation of IND and SAC is negligible in ethyl acetate and low in methanol and ethanol. The IND-NIC cocrystals were more soluble than the IND-SAC cocrystals in all the solvents studied. The eutectic constants predicted both the solubility and the stability of the cocrystals. Understanding the solubility behavior and solution chemistry of cocrystals has important implications for the screening, scale-up, and formulation development of this solid form. Further, the determination of eutectic constants is a simple and resource sparing means of obtaining key information on cocrystal stability and solution behavior
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3.
  • Basavoju, Srinivas, et al. (författare)
  • Indomethacin-saccharin cocrystal : design, synthesis and preliminary pharmaceutical characterization
  • 2008
  • Ingår i: Pharmaceutical research. - : Springer. - 0724-8741 .- 1573-904X. ; 25:3, s. 530-541
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose. To design and prepare cocrystals of indomethacin using crystal engineering approaches, with the ultimate objective of improving the physical properties of indomethacin, especially solubility and dissolution rate. Materials and Methods. Various cocrystal formers, including saccharin, were used in endeavours to obtain indomethacin cocrystals by slow evaporation from a series of solvents. The melting point of crystalline phases was determined. The potential cocrystalline phase was characterized by DSC, IR, Raman and PXRD techniques. The indomethacin-saccharin cocrystal (hereafter IND-SAC cocrystal) structure was determined from single crystal X-ray diffraction data. Pharmaceutically relevant properties such as the dissolution rate and dynamic vapour sorption (DVS) of the IND-SAC cocrystal were evaluated. Solid state and liquid-assisted (solvent-drop) cogrinding methods were also applied to indomethacin and saccharin. Results. The IND-SAC cocrystals were obtained from ethyl acetate. Physical characterization showed that the IND-SAC cocrystal is unique vis-a-vis thermal, spectroscopic and X-ray diffraction properties. The cocrystals were obtained in a 1:1 ratio with a carboxylic acid and imide dimer synthons. The dissolution rate of IND-SAC cocrystal system was considerably faster than that of the stable indomethacin gamma-form. DVS studies indicated that the cocrystals gained less than 0.05% in weight at 98%RH. IND-SAC cocrystal was also obtained by solid state and liquid-assisted cogrinding methods. Conclusions. The IND-SAC cocrystal was formed with a unique and interesting carboxylic acid and imide dimer synthons interconnected by weak N-H center dot center dot center dot O hydrogen bonds. The cocrystals were non-hygroscopic and were associated with a significantly faster dissolution rate than indomethacin (gamma-form).
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4.
  • Basavoju, Srinivas, et al. (författare)
  • Pharmaceutical cocrystal and salts of norfloxacin
  • 2006
  • Ingår i: Crystal Growth & Design. - : American Chemical Society. - 1528-7483 .- 1528-7505. ; 6:12, s. 2699-2708
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of this study was to investigate the structural and pharmaceutical properties of norfloxacin (a poorly soluble antibacterial drug), its cocrystal, and salts. Norfloxacin in the anhydrous form (form A, 1) was crystallized. It was cocrystallized with isonicotinamide (2), and organic salts were prepared with succinic acid, malonic acid, and maleic acid (3-5, respectively). These phases were characterized by differential scanning calorimetry (DSC), infrared (IR) and Raman spectroscopy, and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction data were obtained, and crystal structures were solved. The apparent solubility of these phases was determined. Robust O-H⋯O, O-H⋯O-, O-H⋯N, N-H⋯O, N+-H-O -, and N-H⋯N interactions were present in all these structures. Quinolone moieties in these structures stack with π⋯π interactions and form channels to include CHCl3 or H2O. Herein we report a new cocrystal and salts of norfloxacin with improved aqueous solubility
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5.
  • Basavoju, Srinivas, et al. (författare)
  • Pharmaceutical salts of fluoroquinolone antibacterial drugs with acesulfame sweetener
  • 2012
  • Ingår i: Molecular Crystals and Liquid Crystals. - 1542-1406 .- 1563-5287. ; 562:1, s. 254-264
  • Tidskriftsartikel (refereegranskat)abstract
    • Novel organic salts of norfloxacin and ciprofloxacin with artificial sweeteners such as saccharin and acesulfame were prepared. The two salts 1 and 2 were characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Finally, the crystal structures were solved by single crystal X-ray diffraction data and the structures were analyzed in terms of supramolecular synthons. In norfloxacin acesulfamate 1, two norfloxacin cations and two acesulfame anions form an eight membered cyclic tetramer supramolecular synthon. The salt, ciprofloxacin acesulfamate 2, has a similar structure as salt 1. This study contributes the importance of crystal engineering and supramolecular chemistry to the pharmaceutical applications in terms of interactions and structural correlations in the design of new solid phases. Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental file.
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6.
  • Lou, Benyong, et al. (författare)
  • Hydrogen-bonding interactions in the 4-aminobenzoic acid salt of atenolol monohydrate
  • 2007
  • Ingår i: Acta Crystallographica Section C. - : International Union of Crystallography. - 0108-2701 .- 1600-5759. ; 63:12, s. 714-716
  • Tidskriftsartikel (refereegranskat)abstract
    • Atenolol {or 4-[2-hydroxy-3-(isopropylamino)propoxy]phenyl-acetamide} crystallizes with 4-aminobenzoic acid to give the salt {3-[4-(aminocarbonylmethyl)phenoxy]-2-hydroxypropy1}- isopropylammonium 4-aminobenzoate monohydrate, C14H23- N2O3*C7H6NO2-*H2O. In the crystal structure, the water molecule, the carboxylate group of 4-aminobenzoate, and the hydroxy and ether O atoms of atenolol form a supramolecular R33(11) heterosynthon. Three other types of supramolecular synthons link the asymmetric unit into a two-dimensional structure.
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7.
  • Lou, Benyong, et al. (författare)
  • Monohydrous dihydrogen phosphate salts of norfloxacin and ciprofloxacin
  • 2007
  • Ingår i: Acta Crystallographica Section C. - 0108-2701 .- 1600-5759. ; 63:12, s. 731-733
  • Tidskriftsartikel (refereegranskat)abstract
    • Norfloxacin and ciprofloxacin crystallize with phosphoric acid in aqueous solution to give the salts 4-(3-carboxy-1-ethyl-6-fluoro-4-oxo-1,4-dihydro-7-quinolyl)piperazinium dihydrogenphosphate monohydrate, C16H19FN3O3(+) x H2PO4(-) x H2O, and 4-(3-carboxy-1-cyclopropyl-6-fluoro-4-oxo-1,4-dihydro-7-quinolyl)piperazinium dihydrogenphosphate monohydrate, C17H19FN3O3(+) x H2PO4(-) x H2O, respectively. In the crystal structures, the phosphate anions and the piperazine rings of norfloxacin or ciprofloxacin form a 12-membered supramolecular synthon, viz. R4(4)(12). The synthons R4(4)(12) and R2(2)(8) formed between adjacent phosphate anions result in the three-dimensional structures.
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8.
  • Lou, Benyong, et al. (författare)
  • Polymorph control of felodipine form II in an attempted cocrystallization
  • 2009
  • Ingår i: Crystal Growth & Design. - 1528-7483 .- 1528-7505. ; 9:3, s. 1254-1257
  • Tidskriftsartikel (refereegranskat)abstract
    • The metastable form II of racentic felodipine was obtained in an attempted cocrystallization with isonicotinamide. Its low temperature crystal structure was characterized by a ID hydrogen-bonded chain consisting of four independent felodipine molecules.
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9.
  • Shimpi, Manishkumar R., et al. (författare)
  • New cocrystals of ezetimibe with L-proline and imidazole
  • 2014
  • Ingår i: CrystEngComm. - : Royal Society of Chemistry. - 1466-8033 .- 1466-8033. ; 16:38, s. 8984-8993
  • Tidskriftsartikel (refereegranskat)abstract
    • The objectives of the study were to screen and prepare cocrystals of anti-cholesterol drug ezetimibe (EZT) with the aim of increasing its solubility and dissolution rate. Thermodynamic phase diagram based high throughput screening was performed using wet milling/grinding or solution crystallization methods. A large number of coformers were tested and the resulting solids were preliminarily characterized using X-ray powder diffraction (PXRD) and Raman spectroscopy. Potential cocrystals of EZT with L-proline and imidazole and a solvate formamide were identified in the screening experiments. The cocrystal hits were further characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), solution Proton nuclear magnetic resonance spectroscopy (H-1-NMR) and single crystal XRD. The dissolution properties and stability of cocrystals were determined. Single-crystal X-ray diffraction data were obtained for EZT, EZT-IMI cocrystal and formamide solvate of ezetimibe. All three systems were crystallized in non-centrosymmetric orthorhombic space group P2(1)2(1)2(1) with Z = 4. Robust O-H center dot center dot center dot O, O-H center dot center dot center dot N, N-H center dot center dot center dot O and C-H center dot center dot center dot O hydrogen bonds played an important role in all these crystal structures. EZT-PRO cocrystal showed improved apparent solubility and solid state stability.
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10.
  • Trubetskaya, Anna, 1984-, et al. (författare)
  • One way of representing the size and shape of biomass particles in combustion modeling
  • 2017
  • Ingår i: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 206, s. 675-683
  • Tidskriftsartikel (refereegranskat)abstract
    • This study aims to provide a geometrical description of biomass particles that can be used in combustion models. The particle size of wood and herbaceous biomass was compared using light microscope, 2D dynamic imaging, laser diffraction, sieve analysis and focused beam reflectance measurement. The results from light microscope and 2D dynamic imaging analysis were compared and it showed that the data on particle width, measured by these two techniques, were identical. Indeed, 2D dynamic imaging was found to be the most convenient particle characterization method, providing information on both the shape and the external surface area. Importantly, a way to quantify all three dimensions of biomass particles has been established. It was recommended to represent a biomass particle in combustion models as an infinite cylinder with the volume-to-surface ratio (V/A) measured using 2D dynamic imaging.
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