Figure: a Stacking of the layers found in the BSS structure. Bi-O bonds are drawn as black lines. Hydrogen atoms have been omitted for clarity. b The unit cell of BSS viewed down the a-axis. c A section of the bismuth-oxo rod forming the inorganic building unit which includes O2- anions coordinated to alternatingly three and four Bi3+ cations, µ3 and µ4, respectively. d A molecular sketch of a section of the BSS structure with bonds along the rod omitted for clarity. 

Structure deeply influences API properties. A slight change in their chemical structure may drastically affect their intermolecular interactions and, therefore, their efficacy.

For this reason, the investigation and determination of API’s structure play a pivotal role in drug formulation. A research team from Sweden has recently unveiled the structure of bismuth subsalicylate (BSS), an active pharmaceutical ingredient found in several over-the-counter medications for the treatment of impaired digestion. Till now scientists had not been able to characterize this highly exploited API because of its limited dimension and its intricate structural features.

Thanks to the use of advanced electron microscopy techniques, namely three-dimensional electron diffraction and scanning transmission electron microscopy, Svensson Grape E. et al. were allowed to perform a deeper investigation into bismuth subsalicylate structure and explained its high insolubility. In particular, the scientists were able to reveal its layered structure and to show variations in the stacking of layers.

These findings are of crucial importance because they will open opportunities to the future development of bismuth subsalicylate analogues with potentially implemented efficacy. 

Source : https://www.nature.com