Calcium complexation by corticosteroids.
Cortisone and hydrocortisone form calcium complexes of 2:1 steroid/Ca(2+) stoichiometry in solution, with formation constants of 201 +/- 1.7 and 184 +/- 1.7 M(-2), respectively-roughly half the value seen for a simple aromatic alpha-hydroxy ketone, phenacyl alcohol (341 +/- 10.0 M(-2)). X-ray crystallographic analysis demonstrates maintenance of this 2:1 stoichiometry in the solid state for the phenacyl alcohol and cortisone complexes, while the hydrocortisone complex crystallizes with a 1:1 stoichiometry in the form of linear chains, with the alpha-hydroxy ketone ligand and C(3) (A-ring) carbonyl groups binding two different calcium ions. In each complex, both in solution and in the solid state, the alpha-hydroxy ketone moiety serves as a bidentate chelator for calcium. Extensive hydrogen-bonded networks are present in each structure, linking various hydroxyl groups, coordinated and noncoordinated hydrate molecules, and the chloride counterions, in essence representing supramolecular complexation of the hydrated chloride anion.
Department of Chemistry, University of Oregon, Eugene, Oregon 97403, USA.
Melanie R
MR
Hauser
Kenneth M
KM
Doxsee
Håkon
H
Hope
D000305:Adrenal Cortex Hormones / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008968:Molecular Conformation; D012996:Solutions
D000305:Adrenal Cortex Hormones; D012996:Solutions; D002118:Calcium