Structural characterization of arbidol®

Revisiting the Solubility-Permeability Relationship with Hydrophobic Drug Umifenovir in Pluronic Solutions: Impact of pH and Co-Solvent

This study describes the influence of pluronic F-127 (F-127) and ethanol (EtOH) on the solubility of umifenovir (UMF) in buffer solutions of pH 2.0 and pH 7.4, and its permeability through cellulose membranes. A 44.4-fold greater UMF solubility in acidic medium as compared to an alkaline one was estimated at 310.15 K. The concentration of UMF in the saturated solution was enhanced by the interaction with F-127 micelles. The combined positive effect of EtOH and F-127 on the solubility was estimated. The aggregation number of F-127 micelles in the presence of 10% and 20% ethanol appeared to be reduced by 2.1-fold and 4.1-fold, respectively, as compared to buffer pH 7.4. The presence of ethanol in buffer pH 7.4 solution provided better solvent conditions but inhibited the formation of F-127 micelles. The impact of UMF on the aggregation number of F-127 was not pronounced and was expressed only by a slight increase of 1 and 3 units in 10% and 20% EtOH, respectively. According to the values of zeta potential, addition of EtOH reduced the stability of the system. The permeation of UMF in buffer pH 7.4 measured through the cellulose membrane MWCO 12-14 kDa was increased 1.4-fold by 10% EtOH. An increase in EtOH content to 20% reduced this effect to 1.2-fold. Decreasing effect of 1.5% F-127 on the permeability was inhibited by using 10% EtOH. The solution containing 1.5% F-127 and 10% EtOH was shown to be an advantageous system for UMF in view of the solubility-permeability balance. The authors suppose the findings of the study to be useful for the design of pharmaceutical formulations based on UMF antiviral drugs.

Conformational Screening of Arbidol Solvates: Investigation via 2D NOESY

Understanding of the nucleation process's fundamental principles in saturated solutions is an urgent task. To do this task, it is necessary to control the formation of polymorphic forms of biologically active compounds. In certain cases, a compound can exist in a single polymorphic form, but have several solvates which can appear in different crystal forms, depending on the medium and conditions of formation, and show different pharmaceutical activity. In the present paper, we report on the analysis of Arbidol conformational preferences in two solvents of different polarities-deuterated chloroform and dimethyl sulfoxide-at 25 °C, using the 2D NOESY method. The Arbidol molecule has various solvate forms depending on the molecular conformation. The method based on the nuclear Overhauser effect spectroscopy was shown to be efficient in the analysis of complex heterocyclic compounds possessing conformation-dependent pseudo-polymorphism. It is one of the types of polymorphism observed in compounds forming crystal solvates. Combined use of NMR methods and X-ray data allowed determining of conformer populations of Arbidol in CDCl₃ and DMSO-d₆ which were found to be 8/92% and 37/63%, respectively. The preferred conformation in solution is the same that appears in stable crystal solvates of Arbidol.