title: New Solid Forms of the Antiviral Drug Arbidol: Crystal Structures, Thermodynamic Stability, and Solubility.
abstract: Salts of the antiviral drug Arbidol (umifenovir) with pharmaceutically relevant benzoate and salicylate anions were obtained, and their crystal structures were described. For Arbidol salicylate, an unstable solvate with acetonitrile was also found and characterized. Analysis of the conformational preferences of the Arbidol molecule in the crystal structures showed that it adopts two types of conformations, namely "open" and "closed", both of which correspond to local conformational energy minima of the isolated molecule. Thermal stability of the Arbidol salicylate solvates with chloroform and acetonitrile was analyzed by means of differential scanning calorimetry and thermogravimetric analysis. The standard thermodynamic functions of the salt formation were determined. The Gibbs energy change of the process was found to be negative, indicating that the formation of the salts from individual components is a spontaneous process. The dissolution study of the Arbidol salts performed in aqueous buffer solutions with pH 1.2 and 6.8 showed that both salts dissolve incongruently to form an Arbidol hydrochloride monohydrate at pH 1.2 and an Arbidol base at pH 6.8, respectively.
authors.affiliation: G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences , 153045, Ivanovo, Russia.
authors.forename: Artem O
authors.initials: AO
authors.lastname: Surov
authors.affiliation: G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences , 153045, Ivanovo, Russia.
authors.forename: Alex N
authors.initials: AN
authors.lastname: Manin
authors.affiliation: Institute of General and Inorganic Chemistry, Russian Academy of Sciences , Leninskii Prospekt 31, 119991 Moscow, Russia.
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Churakov
authors.affiliation: G.A. Krestov Institute of Solution Chemistry, Russian Academy of Sciences , 153045, Ivanovo, Russia.
authors.forename: German L
authors.initials: GL
authors.lastname: Perlovich
mesh_terms: D000998:Antiviral Agents / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D018360:Crystallography, X-Ray / Q000379:methods*; D004355:Drug Stability; D007211:Indoles / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D012492:Salts / Q000737:chemistry*; D013816:Thermodynamics; D013818:Thermogravimetry; D014961:X-Ray Diffraction; D013440:Sulfides
chemical_list: D000998:Antiviral Agents; D007211:Indoles; D012492:Salts; C086979:umifenovir; D013440:Sulfides
keywords: Arbidol; X-ray diffraction; conformation analysis; dissolution; pharmaceutical salts; solvates; thermodynamics; umifenovir