Unique Coordination Mode of Potassium Ions to Glycyrrhizin: X-ray Crystal Structure of Glycyrrhizin Dipotassium Salt

Abstract The coordination of six potassium ions to glycyrrhizin (1) is shown in a crystal: two crystallographically independent (K1 and K2) and four symmetry-translated potassium ions coordinate to the oxygen atoms of the sugar-linkage moiety, and the K1 and K2 ions form seven and six coordination bonds with the neighboring oxygen atoms, respectively. Although three carboxyl groups of 1 are in an anionic state, two of the glycosides participate in the coordination bonds with the potassium ions.