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Sökning: WFRF:(Basavoju Srinivas)

  • Resultat 1-10 av 15
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1.
  • Alhalaweh, Amjad, et al. (författare)
  • Pharmaceutical cocrystals of nitrofurantoin : Screening, characterization and crystal structure analysis
  • 2012
  • Ingår i: CrystEngComm. - 1466-8033 .- 1466-8033. ; 14:15, s. 5078-5088
  • Tidskriftsartikel (refereegranskat)abstract
    • The objective of this study was to screen and prepare cocrystals of the poorly soluble drug nitrofurantoin (NTF) with the aim of increasing its solubility. Screening for cocrystals of NTF using 47 coformers was performed by high-throughput (HT) screening using liquid assisted grinding (LAG) methods. Raman spectroscopy and powder X-ray diffraction (PXRD) were used as the primary analytical tools to identify the new crystalline solid forms. Manual LAG and reaction crystallization (RC) experiments were carried out to confirm and scale-up the hits. Seven hits were confirmed to be cocrystals. The cocrystals were characterized by PXRD, Raman and IR spectroscopy, thermal analysis (DSC and TGA) and liquid-state NMR or elemental analysis. The solution stability of the scaled-up cocrystals in water was tested by slurrying the cocrystals at 25 °C for one week. NTF forms cocrystals with a 1:1 stoichiometric ratio with urea (1), 4-hydroxybenzoic acid (2), nicotinamide (3), citric acid (4), l-proline (5) and vanillic acid (6). In addition, NTF forms a 1:2 cocrystal with vanillin (7). All but one of the NTF cocrystals transformed (dissociated) in water, resulting in NTF hydrate crystalline material or NTF hydrate plus the coformer, which indicates that the transforming cocrystals have a higher solubility than the NTF hydrate under these conditions. The crystal structures of 1:1 NTF-citric acid (4) and 1:2 NTF-vanillin (7) were solved by single-crystal X-ray diffraction. The crystal structures of these two cocrystals were analyzed in terms of their supramolecular synthons.
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2.
  • Basavoju, Srinivas, et al. (författare)
  • Crystal Structures of Hydrates of Norfloxacin
  • 2006
  • Ingår i: 2006 AAPS Annual Meeting and Exposition. - : American Association of Pharmaceutical Scientists.
  • Konferensbidrag (refereegranskat)abstract
    • Description: Purpose: The aim was to identify new phases of norfloxacin and to analyse their crystal structures. Methods: Norfloxacin was crystallized in methanol under various conditions using solvent-drop grinding method. The single crystal X-ray diffraction data sets were collected on a Bruker Nonius Kappa CCD, using Mo Kα radiation (λ = 0.71073 Å). Results: Norfloxacin mono-and trihydrates were identified. Mono and trihydrates crystallize in Pbca, P21/c space groups respectively. One of the water molecules in trihydrate is in disorder. In these structures, inversion related norfloxacin molecules form stacked layers with quinolone moieties and stabilized by ππ (3.449 to 4.016 Å) interactions. The norfloxacin molecules in stacked layers generate hydrophilic channels to include water molecules through O-HO, O-HO¯ and N-HO¯ interactions. A significant difference in the torsional angles of the piperazinyl ring of norfloxacin in mono-, di- (reported), and trihydrate was evident for conformational flexibility. Conclusion: We report crystal structures of mono and trihydrates of norfloxacin that are channel hydrates. Norfloxacin may exhibit conformational polymorphism
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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 Co-crystallization of Norfloxacin
  • 2006
  • Ingår i: 2006 AAPS Annual Meeting and Exposition. - : American Association of Pharmaceutical Scientists.
  • Konferensbidrag (refereegranskat)abstract
    • Description: Aim: The objective of the study was to prepare co-crystal and salts of norfloxacin and to investigate their structural and pharmaceutical properties. Methods: Norfloxacin was crystallized in a series of solvents in an effort to investigate the polymorphism. Norfloxacin was also co-crystallized with isonicotinamide and succinic acid in different solvents. We have characterised these materials using DSC, IR, Raman and PXRD. The single crystal X-ray diffraction data was obtained and crystal structures were solved. The solubility and moisture sorption behaviour (0-90%RH) of these materials were determined. Results: Norfloxacin Anhydrate, 1 crystallizes in the triclinic P-1 space group with one neutral molecule in the asymmetric unit. The carboxylic acid group participates in the intramolecular O­­-HO (D=2.525 Å) hydrogen bonding with carbonyl group of the quinolone moiety. NorfloxacinIsonicotinamideCHCl3, 2 crystallizes in the centrosymmetric C2/c space group with one molecule of norfloxacin, one molecule of isonicotinamide and one molecule of CHCl3.in the asymmetric unit. Four molecules of norfloxacin generate a rectangular host type network with N-HO (D=2.668 Å) and N-HO (D=2.657 Å) interactions. Two isonicotinamide molecules form robust amideamide (N-HO, D=2.889 Å) homodimer synthon and fits into the rectangular grid (N-HO, D=2.929 Å). The CHCl3 molecules lie in the channels of the host frame work. Norfloxacin (Succinate)0.5 Hydrate, 3 crystallizes in the triclinic P-1 space group with one norfloxacin cation, half molecule of succinate dianion and one H2O molecule in the asymmetric unit. The two succinate anions and two norfloxacin cations form a cyclic tetramer synthon (N-HO, D=2.726 Å) and extends with H2O molecules through the hydrophilic channel generated by quinolone stacked layers (ππ, 4.041 Å) along the a-axis via O-HO (D=2.928 Å) interactions. The rank order of the solubility of these materials was 1<2
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5.
  • 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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6.
  • 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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  • Resultat 1-10 av 15
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