Structural Basis for Polymer Packing and Solvation Properties of the Organogermanium Crystalline Polymer Propagermanium and Its Derivatives

Nobuhiro Mizuno, Eiji Nishibori, Mitsuru Oka, Takahito Jomori, Masaki Takata, Takashi Kumasaka

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

Of organogermanium compounds known to have an immunostimulatory action, propagermanium [PGe; 3-oxygermylpropionic acid polymer, (C3H5GeO3.5)n] is the only one used as a pharmaceutical agent, to treat the hepatitis B virus in Japan. However, because of lack of information about its structure, PGe has been confused with a polymeric solid, repagermanium (RGe, Ge-132, poly-trans-[(2-carboxyethyl) germasesquioxane], (C18H30Ge6O21)n), which has the same essential formula as PGe. To clarify this issue, the structure of PGe was analyzed using X-ray diffraction (XRD). PGe has a polymeric ladder-shaped structure of a concatenated eight-membered ring composed of Ge £ O bonds, which is clearly distinguished from the infinite sheet structure in RGe. Moreover, we observed temperature or moisture-dependent transformations among these compounds using powder XRD. For instance, PGe was easily dissolved in water, and transformed to RGe by exposure to water vapor, but transformed into another straight-chain structure when exposed to aqueous solution. As a result of these findings, PGe was indicated to have labile polymer packing against RGe. These characteristics of PGe may affect pharmaceutical properties such as respective stability and solubility, which indicate its unique impact on physiological activity.

Original languageEnglish
Pages (from-to)2482-2488
Number of pages7
JournalJournal of Pharmaceutical Sciences
Volume104
Issue number8
DOIs
Publication statusPublished - 2015 Aug 1
Externally publishedYes

Keywords

  • X-ray powder diffractometry
  • crystal structure
  • crystallography
  • solvation
  • stability

ASJC Scopus subject areas

  • Pharmaceutical Science

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